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TRANSCRIPT
PROJECT REPORT
(Project Semester December-June 2011)
A) Tri Ethyl Ammine (TEA) Gas Optimization
B) Study of Scrubber Unit in Cold Box Machine
C) Water management in Wash Prepartaion
Submitted by
Preet Inder Singh
08107042
Under the Guidance of
Prof. Rajesh Kumar Kanda Mr. Saini
Mechanical Engg. Dept. D.G.M
PEC University of Technology New Projects
Chandigarh D.C.M Engg. Products, Ropar
Department Of Mechanical Engineering
Punjab Engineering College University of Technology,
Chandigarh
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3rd January 2011 to 14th April 2011
DECLARATION
I hereby declare that project work entitled ‘i)Tri Ethyl Ammine (TEA) Gas Optimization and ii)
Study of scrubber unit on cold box machine and iii)water management in wash preparation’ is
an authentic record of my own work carried out at D.C.M Engg. Products as requirements of six
months project semester for the award of degreeof B.E. Mechanical Engineering, Punjab
Engineering College University of Technology, Chandigarh, under the guidance of Mr. Saini and
Prof.Rajesh Kanda, from 3rd Jan ’2011 to 14th april 2011.
Preet Inder Singh
08107042
Date: _____________
Certified that the above statement made by the student is correct to the best of our knowledge
and belief.
Prof.Rajesh Kanda Mr. Saini
Mechanical Engg. Dept. D.G.M
PEC University of Technology New Projects
Chandigarh D.C.M Engg. Products, Ropar
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ACKNOWLEDGEMENT
I would like to express my gratitude towards the management of D.C.M Engg. Products for
giving me such an opportunity to undergo inplant training in their renowned and esteemed
organization.
I thank Mr.Saini, Mr.Surender Singh , Mr. Harkaran Singh Cheema and Mr.Manpreet Singh, for
giving me an opportunity to learn in this department. I thank them for their superlative support,
practical skills, for their day-to-day assistance and encouragement given to me during my
training period.
I acknowledge my sincere thanks to Prof.Rajesh Kanda, my project guide who have given me the
utmost guidance and support throughout inplant training.
I also place on record my sincere thanks to each and every employee of D.C.M Engg. Products
who has given me full co-operation during my training period.
Preet Inder Singh
08107042
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CONTENTS
1. Project Synopsis
2. Introduction to D.C.M Engg. Products
2.1 Company Profile and History
2.2 Different Departments in D.C.M
3. Definition and Breifing about Casting
4. Casting Process
4.1 Components of casting
5. Core Making Process
5.1 Different Types
5.2 Chemical Characterization of Cold Box Resins and Activators
5.3 Sands
5.4 Mixing
5.5 Transportation
5.6 Pattern Equipment for core production
6. Cold Box Machine
6.1 Description of the machine
6.2 Outline of the operation
6.3 Start Position of machine
6.4 Checking points before operation
6.5 Gas Generator
7. Scrubber
8. Testing
8.1 Description of process and testing equipmen
8.2 The analytical results
9. Core making revolution
9.1 Introduction
9.2 The Eshamine Plus Process
9.3 The Ecolotec Process
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9.4 Production Expereince
9.5 Environmental Considerations
9.6 Summary
10. Advances in coremaking technology
10.1 Trends in tooling Design
10.2 New Binder Technology
10.3 Conclusions
11. Coatings (Wash)
11.1 Classification of mould and core coatings
11.2 Wash Perparation
11.3 Automization for water management
APPENDICES
1. Appendix I: Bio Filteration of TEA Gas
2. Appendix II: Properties of Gray Cast Iron
3. Appendix III: Binders and Additives
4. Appendix IV: Sand testing and control
BIBLIOGRAPHY
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1.PROJECT SYNOPSIS
This project summarizes work done by me during six months of inplant training in D.C.M, Engg.
Products, Ropar. As an inplant trainee I was assigned the duty to work in the Core-Shop
department, which made me familiar with Cores. The project presents information regarding the
principles of core production during casting followed by analysis on TEA gas optimization, with
a prime attention on its optimal usage during core production in cold box, core making machine.
Along with study and understanding of Scrubber Unit in a Cold Box Machine. Second part of
my report explains the water management in wash preparation . The objective of this live project
was to analyze, learn and implement the practical considerations of optimization of TEA gas
during Core Production in cold box machine with complete knowledge of scrubber unit. Along
with the study of usage of water in preparing wash for cores made by either hot, cold or shell
process.
In the Core Shop Dept., I was introduced to principles of core shop and core production for
casting.
A core is a device used in casting and molding processes to produce internal cavities and
reentrant angles. The core is normally a disposable item that is destroyed to get it out of the
piece. They are most commonly used in sand casting.
Some core making processes are defined as under:
Sodium Silicate/ CO2 Process Molasses Process Shell process Green sand Cold-box
TEA (Tri ethyl Amine) has been used widely as a catalyst in foundaries. TEA has irritating
effects on the skin, eyes, trachea and bronchi. Main symptoms in workers exposed to TEA are
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foggy and halo vision when looking at a light, So regulation of TEA gas is a must and its usage
must be optimized.
TEA exposure levels of foundries and their core makers vary greatly. Stationary air
measurements in factories are not sufficient to assess TEA exposure. Instead, personal sampling
is needed. The harmful effects of TEA gas can be measured form urine samples of the workers
working at the cold box m/c and the workers elsewhere.
Regulation of TEA gas is done by the scrubber unit placed with the cold box m/c where TEA gas
is used as a catalyst. After TEA gas is used it is passed through the scrubber unit. The term
scrubber unit is used basically to the devices which control pollution. The process is well
explained by the diagram below
In Cold-box Core making Process TEA ( Tri ethyl Ammine) Gas is passed through the core in
the machine to get a finally hardened-baked core which can be used in casting after going
through wash process.
Scrubber Unit is a unit in cold box machine in which the harmful TEA gas is neutralized. After
the TEA gasses passes through the core, knowing the fact that TEA gas is a catalyst, it doesn’t
get consumed so fumes of TEA are neutralized in scrubber unit.
Wash Prepartion
They buy chemicals from Gargi and water is added to those slimy or powdery chemicals to make
less viscous hence a useable wash. Initially water is filled till the 100 lt. mark in the tanker and
two bags of wash (paste form) is added to the tank. After a liltle bit of manually stirring, mixer is
switched on for 30 mins. If still some solid particles are remaining then mixer is switched on for
another 15 mins. Here viscosity is adjusted to approx 24 secs. Then they are diluted as per
requirement in particular areas for specific cores. Then the tank is cleaned before next batch is
prepared.
Cores are coated with a refractory wash to increase the cores refractiveness and to produce a
smoother metal surface in the cored cavity of the casting. These materials are called washes.
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They can be purchased in a variety of types and refractive strength. A common home made wash
is graphite and molasses water mixed to a nice paint consistency.
Water mangement can be applied right at the beginning of wash preparation where a lot of water
is wasted and a possible automization can be applied as well after thorough study at the fieldAll
these topics are exhaustively covered with the requisite technical literature and in depth design
and planning principles associated with them. The systematic procedure adopted in the industrial
atmosphere for carrying out the projects is also mentioned. Inplant training at such renowned and
reputed organization was a highly enriching and fruitful experience, which will definitely help
me in future.
This project presents information regarding the principles followed during analysis of TEA gas
optimization in core making process..
This report is presented in following sections namely,
Definition of Core Making and Briefing Of Cold-box Core Making Machine
TEA Gas – Observations and optimization
Study of Scrubber Unit and final Analysis
Water management in wash preparation
These topics are adequately provided with the necessary technical literature, consisting of brief
explanation on terminologies used and in depth design principles associated with their design.
The systematic procedure adopted in the industrial atmosphere for carrying out the projects is
also mentioned before the detailed explanation of the work carried out on the sections.
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2.1 INTRODUCTION TO D.C.M
DCM has been an industrial front runner in the Indian sub continent. The history of DCM group
goes back to 1889 with the Delhi Cloth Mills, when industry was in its infancy in India.
In domestic market DCM is associated with top automotive players: Maruti Udyog, Hyundai
Motors, Mahindra & Mahindra, International Tractors Ltd., Ashok Leyland, Eicher Motors,
Escorts, Swaraj Mazda, JCB India, Force Motors, Simpson & Co and many more.
India is emerging as major auto component supplying hub to the global automotive
manufacturers resulting in tremendous scope for increased business opportunities in domestic as
well as international markets. Set up another plant in south India, project engineering work for
which has commenced.
"Company employs more than 1700 people at its manufacturing plant at Ropar, Punjab. At its
Ropar plant company houses two high pressure moulding lines with press pour, state of the art
tooling & designing facility in addition to other supporting processes and equipments."
Company’s registered office is at New Delhi. It is a subsidiary of DCM Limited. DCM
Engineering Limited is not a listed entity. Its holding company is however listed at BSE and
NSE.
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2.2 DIFFERENT DEPARTMENTS OF D.C.M
1. HPM (High Pressure Moulding) 2. Melting (furnace) Area
3. Core Shop and sand control 4.Fettling Area
5.Shot Blast and Painting 6.Return & New Sand Plant
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3.CASTING
3.1 GRAY CAST IRON
Cast iron is derived from pig iron, and while it usually refers to gray iron. Gray iron is the most
versatile of all foundry metals. The high carbon content is responsible for ease of melting and
casting in the foundry and for ease of machining in subsequent manufacturing. The low degree or
absence of shrinkage and high fluidity provide maximum freedom of design for the engineer.
Gray iron is one of the most easily cast of all metals in the foundry. It has the lowest pouring
temperature of the ferrous metals, which is reflected in its high fluidity and its ability to be cast
into intricate shapes. As a result of a peculiarity during final stages of solidification, it has very
low and, in some cases, no liquid to solid shrinkage so that sound castings are readily obtainable.
For the majority of applications, gray iron is used in its as-cast condition, thus simplifying
production. Gray iron has excellent machining qualities producing easily disposed of chips and
yielding a surface with excellent wear characteristics. The resistance of gray iron to scoring and
galling with proper matrix and graphite structure is universally recognized.
Gray Cast Iron also identifies a large group of ferrous alloys which solidify with a eutectic. The
colour of a fractured surface can be used to identify an alloy. White cast iron is named after its
white surface when fractured, due to its carbide impurities which allow cracks to pass straight
through. Grey cast iron is named after its grey fractured surface, which occurs because the
graphitic flakes deflect a passing crack and initiate countless new cracks as the material breaks.
COMPOSITION
Carbon (C) and silicon (Si) are the main alloying elements, with the amount ranging from 2.1 to
4 wt% and 1 to 3 wt%, respectively. Iron alloys with less carbon content are known as steel.
While this technically makes these base alloys ternary Fe-C-Si alloys, the principle of cast iron
solidification is understood from the binary iron-carbon phase diagram. Since the compositions
of most cast irons are around theeutectic point of the iron-carbon system, the melting
temperatures closely correlate, usually ranging from 1,150 to 1,200 °C (2,102 to 2,192 °F),
which is about 300 °C (572 °F) lower than the melting point of pure iron.
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PROPERTIES
Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point,
good fluidity, castability, excellent machinability, resistance to deformation and wear resistance,
cast irons have become an engineering material with a wide range of applications and are used in
pipes, machines and automotive industry parts, such as cylinder heads (declining usage), cylinder
blocks andgearbox cases (declining usage). It is resistant to destruction and weakening by
oxidisation (rust).
3.2 CASTING PROCESS
Several molding processes are used to produce gray iron castings. Some of these have a marked
influence on the structure and properties of the resulting casting. The selection of a particular
process depends on a number of factors, and the design of the casting has much to do with it. The
processes using sand as the mold media have a somewhat similar effect on the rate of
solidification of the casting, while the permanent mold process has a very marked effect on
structure and properties.
Green sand molding is frequently the most economical method of producing castings. Until the
introduction of high-pressure molding and very rigid flask equipment, dimensional accuracy has
not been as good as can be obtained from shell molding. If green sand molds are not sufficiently
hard or strong, some mold wall movement may take place during solidification, and shrinkage
defects develop. Although castings up to 1000 lb or more can be made in green sand, it generally
is used for medium to small size castings. For the larger castings, the mold surfaces are
sometimes sprayed with a blacking mix and skin dried to produce a cleaner surface on the
casting. This procedure is often used on engine blocks.
To withstand the higher ferrostatic pressures developed in pouring larger castings; dry sand
molds are often used. In some cases, the same sand as used for green sand molding is employed,
although it is common practice to add another binder to increase the dry strength.
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The shell molding process is also used for making cores which are used in other types of molds
besides shell molds. Its principal advantage is derived from the ability to harden the mold or core
in contact with a heated metal pattern, thus improving the accuracy with which a core or mold
can be made. In addition to the improved accuracy, a much cleaner casting is produced than by
any other high-production process. Although the techniques and binders for hot box and the
newest cold box processes differ from those used for the shell molding process, the principle is
similar in that the core is hardened while in contact with the pattern.
Centrifugal casting of iron in water-cooled metal molds is widely used by the cast iron pipe
industry as well as for some other applications. With sand or other refractory lining of the metal
molds, the process is used for making large cylinder liners.
For some types of castings, the permanent mold process is a very satisfactory one, and its
capabilities have been described by Frye. Since the cooling or freezing rate of iron cast into
permanent molds is quite high, the thinner sections of the casting will have cementite. To remove
the cementite the castings must be annealed, and it is universal practice to anneal all castings.
The most economical composition of the iron for permanent mold castings is hypereutectic. This
type of iron expands on solidification, and, because the molds are very rigid, the pressure
developed by separation of the graphite during freezing of the eutectic ensures a pressure tight
casting. Since the graphite occurs predominantly as Type D with very small flakes, permanent
mold castings are capable of taking a very fine finish. For this reason, it finds extensive use in
making valve plates for refrigeration compressors. The process is also ideally suited for such
components as automotive brake cylinders and hydraulic valve bodies. Although the
predominantly Type D graphite structure in permanent mold castings with a matrix of ferrite
have much higher
strength than sand
castings of
comparable graphite
content, the structure
is not considered
ideal for applications
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with borderline lubrication. The castings perform very well, however, when operating in an oil
bath.
Unless some special properties are desired and are obtained only with a particular casting
process, the one generally selected yields castings at the lowest cost for the finished part.
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4 SAND CASTING
Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand as the mold material.It is relatively cheap and sufficiently refractory even for steel foundry use. A suitable bonding agent (usually clay) is mixed or occurs with the sand. The mixture is moistened with water to develop strength and plasticity of the clay and to make the aggregate suitable for molding. The term "sand casting" can also refer to a casting produced via the sand casting process. Sand castings are produced in specialized factories called foundries.Over 70% of all metal castings are produced via a sand casting process.
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There are six steps in this process:
1. Place a pattern in sand to create a mold.
2. Incorporate the pattern and sand in a
gating system.
3. Remove the pattern.
4. Fill the mold cavity with molten metal.
5. Allow the metal to cool.
6. Break away the sand mold and remove the casting.
4.1 COMPONENTS
a) Pattern
From the design, provided by an engineer or designer, a skilled pattern maker builds a pattern of
the object to be produced, using wood, metal, or a plastic such as expanded polystyrene. Sand
can be ground, swept or strickled into shape. The metal to be cast will contract during
solidification, and this may be non-uniform due to uneven cooling. Therefore, the pattern must
be slightly larger than the finished product, a difference known as contraction allowance.
Pattern-makers are able to produce suitable patterns using 'Contraction rules' (these are
sometimes called "shrink allowance rulers" where the ruled markings are deliberately made to a
larger spacing according to the percentage of extra length needed). Different scaled rules are
used for different metals because each metal and alloy contracts by an amount distinct from all
others. Patterns also have core prints that create registers within the molds into which are placed
sand 'cores. Such cores, sometimes reinforced by wires, are used to create under cut profiles and
cavities which cannot be molded with the cope and drag, such as the interior passages of valves
or cooling passages in engine blocks.
Paths for the entrance of metal into the mold cavity constitute the runner system and include
the sprue, various feeders which maintain a good metal 'feed', and in-gates which attach the
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runner system to the casting cavity. Gas and steam generated during casting exit through the
permeable sand or via risers, which are added either in the pattern itself, or as separate pieces.
b) Molding box and materials
A multi-part molding box (known as a casting flask, the top and bottom halves of which are
known respectively as the cope and drag) is prepared to receive the pattern. Molding boxes are
made in segments that may be latched to each other and to end closures. For a simple object—
flat on one side—the lower portion of the box, closed at the bottom, will be filled with a molding
sand. The sand is packed in through a vibratory process called ramming and, in this case,
periodically screeded level. The surface of the sand may then be stabilized with a sizing
compound. The pattern is placed on the sand and another molding box segment is added.
Additional sand is rammed over and around the pattern. Finally a cover is placed on the box and
it is turned and unlatched, so that the halves of the mold may be parted and the pattern with its
sprue and vent patterns removed. Additional sizing may be added and any defects introduced by
the removal of the pattern are corrected. The box is closed again. This forms a "green" mold
which must be dried to receive the hot metal. If the mold is not sufficiently dried a steam
explosion can occur that can throw molten metal about. In some cases, the sand may be oiled
instead of moistened, which makes possible casting without waiting for the sand to dry. Sand
may also be bonded by chemical binders, such as furane resins or amine-hardened resins.
An intimation slip is sent from the tool design department to the initiator for attending the design
discussion meeting. During this meeting, the tool initiator discusses the various aspects of the
design.
In fixtures, the initiator discusses the loading, clamping, etc of the tool.
In moulds,
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Layout,
No. of cavities,
Gating and runner systems,
Cooling systems, etc
Are discussed by the initiator.
The minutes of the discussion are recorded and
filed in the tool request file after the tool is
released.
c) Cores
To produce cavities within the casting—such as for liquid cooling in engine blocks and cylinder
heads—negative forms are used to produce cores. Usually sand-molded, cores are inserted into
the casting box after removal of the pattern. Whenever possible, designs are made that avoid the
use of cores, due to the additional set-up time and thus greater cost.
Two sets of castings (bronze and aluminium) from the above sand mold
With a completed mold at the appropriate moisture content, the box containing the sand mold is
then positioned for filling with molten metal—
typically iron, steel, bronze, brass, aluminium, magnesium alloys, or various pot metal alloys,
which often includelead, tin, and zinc. After filling with liquid metal the box is set aside until the
metal is sufficiently cool to be strong. The sand is then removed revealing a rough casting that,
in the case of iron or steel, may still be glowing red. When casting with metals like iron or lead,
which are significantly heavier than the casting sand, the casting flask is often covered with a
heavy plate to prevent a problem known as floating the mold. Floating the mold occurs when the
pressure of the metal pushes the sand above the mold cavity out of shape, causing the casting to
fail.
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After casting, the cores are broken up by rods or shot and removed from the casting. The metal
from the sprue and risers is cut from the rough casting. Various heat treatments may be applied
to relieve stresses from the initial cooling and to add hardness—in the case of steel or iron, by
quenching in water or oil. The casting may be further strengthened by surface compression
treatment—like shot peening—that adds resistance to tensile cracking and smooths the rough
surface.
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d) SANDPLANT
The sand plant in a foundry is heart of sand casting process. It’s the basic process of casting. In
new sand plant new sand (Allahabad sand , in case of D.C.M) is added to the sand storage and its
is prepared with addition of certain mixers and binders and additives like coal dust so that it can
be used for casting. This sand is not directly used, it is mixed with return sand which comes from
knocking off the casting and it is mixed with the used sand and then sieved and segregated and
added with more mixtures and additives to be used in casting process.
Hence Sand Plant is divided in two main parts:
i)New Sand Plant
ii) Return Sand Plant
Sand Plant Equipment
VIBRATORY KNOCK-OUT:
Shakeout Machine is designed to separate sand and castings from mould box. The Shakeout
Machine consists of a top deck, made out of thick steel plate having drilled holes, which together
with top rugged fabricated frame floats on heavy duty springs resting on a supporting structure.
The floating top frame is made to shake violently either by an eccentric shaft drive mechanism or
by vibro-motor system. Four sizes ranging from 1 to 12 MT is available in the Wesman range.
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COVEYORS: Wesman designs and supplies different types of conveyers namely Oscillating,
Belt type, Pallet and Roller conveyer in standard and custom design sizes.
Oscillating Conveyer has a vibrating trough, supported by arms of special design. This conveys
material due to a special pattern of oscillating motion imparted by combined action of driving
crank and the inclined supporting arms. Down load leaflet
Belt Type Conveyer is available mainly for movement of material horizontal or slightly inclined
plane. Troughed endless rubber belt, supported by sets of idle rollers, is held between two drums
at the two ends. The drive drum is powered by motor and gear box or geared-motor
arrangement. Available in various lengths and sizes according to specific requirement.
Elevator: Wesman supplies belt and bucket type elevators mainly for conveying foundry sand in
vertical direction. Rust free fiber-glass buckets are available as an option. Some parts of the
Elevator body are also made of Fiber-glass for longer life. These are tailor made to suit the
specific plant layout and capacities.
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Rotary Table Feeder: The Rotary Table feeder is used to feed sand from a bunker to a
Conveyer or other downstream equipment where pre-set feed rate is required. The feed rate may
be mechanically adjusted which would remain unaltered till it is re-set. These are available in
three table sizes for various feed rates from 4 to 20 MT/hr.
Screw Feeder: Screw feeders are use for conveying additive from additive hopper to mixer at
the required rate. These are fitted with VFD controlled Motors for varying the RPM for adjusting
the required feed rate.
Polygonal Screen: Rotary Polygon Screen is used in Sand Preparation Plants for removal of
lumps of sand, large pieces of scrap, non-magnetic and coarse foreign materials from the
knocked out used sand or dried new sand. This is done by using rotating hexagonal screen of
required mesh size.
Aerator: Aerators effectively disintegrate foundry moulding sand to produce fluffy sand that
would ram to a uniform density in moulds and produce impression of finer details. Aerators are
normally installed at the outlet of Mullers or on top of a distribution belt conveyor after Muller
and before molder’s hoppers. Aeration is effected by rotating combs.
Magnetic Separator: Magnetic separators are used to separate iron pieces from the return
knocked out sand. These are either Drum type used as a non drive drum of a conveyer or over
band type used across conveyor at a short height of return sand line. High intensity anisotropic
strontium ferrite permanent magnets are used in Wesman magnetic separators for stronger
magnetic pull.
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Core and Mould oven: Both batch (trolley) type and
continuous (vertical) type core and mould ovens are
available in various sizes, from 500 to 3000 Kg, for
baking / drying of cores / moulds of various
compositions. Wesman ovens may be fired with oil
/gas. Some of the trolley type batch ovens are
available with Electric heating option.
e) FETTLING
When a recently poured cast has cooled off sufficiently, the founder can dismantle any
surrounding FLASK or shuttering used to contain the mould during casting, and then remove
easily broken off investment or sand from the cast. If a mechanical aid such as a JACK
(BREAKING) HAMMER or hand chisel is used to assist in this KNOCKOUT, great care is
taken to avoid cutting into and damaging the underlying cast; with some castings (esp iron),
mishandling during the knockout can lead to a brittle fracture of the design.
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Once the flask has been cleared from the foundry floor, the founder is left with a cast and
attached metal running system covered with spent refractory. If the wax was CORED (to make
the cast hollow), there will also be the remains of an internal refractory mass, complete with core
vents and retaining pins projecting through cast’s metal surface. The process of removing these
now superfluous attachments, and the initial working of the cast, is known as FETTLING.
The runners, risers and pouring cup are normally cut away first, though some may be
temporarily left on for use as pick-up points for hooks, chains and vice grips. Any residual
refractory in the vicinity of the cut is first removed, this prevents excessive dust exhaust. Most
founders remove attachments by FRICTION CUTTING, (using an aluminium oxide cut off disc
mounted on a portable angle grinder), though band saws and PLASMA CUTTERS may
sometimes be used as an alternative. The attachment is cut off, leaving a short stub of metal close
to the surface of the cast. This is done carefully, without damaging any part of the artist’s work.
The remaining stub or SIGHTING permits fine finishing to be carried out a later, more
convenient point.
If a core mass has been used to create a cast hollow, this material must now be completely
removed. Core refractory (be it sand, plaster and grog, or ceramic), can be ‘cooked’ into a very
hard, tenacious substance, so a complete removal of the core mass can be a very time consuming
operation. Dislodging spent core from difficult to reach areas can be aided by working thin
chisels and other dislodging tools through any core pin and patch holes already in the cast.
WATER JET BLASTING may also be used to washout core debris.
It is important that all the core mass is removed from the interior of the cast to prevent a long
term degeneration of the cast’s structure and minimise the weight of the finished sculpture. The
hygroscopic potential of both PLASTER & GROG, and sand core refractory makes these
materials especially prone to the absorbtion of moisture. Waterlogged core contents can over
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time expand to split the cast, or else react with the cast alloy to effectively rot the sculpture’s
fabric from the inside out.
Any residual refractory still adhering to the cast after knocking-out is dislodged by either
manual, mechanical or chemical means. Methods of fine refractory removal are diverse, and can
include hand chiselling, wire brushing, pickling in a weak acid solutions, wet and dry shot
blasting, ultrasonic washing, vibration and attrition by abrasive media – all of which can be used,
either individually or in combination, to clean the cast.
The degree of difficulty encountered in removing residual mould material very much depends
upon the type of refractory, how well it was fired, and the surface textures on the underlying cast.
As a rule, CERAMIC SHELL investment easily breaks away from smooth surfaced casts,
requiring little if any further treatment other than a gentle rub over with a fine abrasive cloth; this
is possible because the cast contracts slightly on cooling, effectively breaking up the rigid
ceramic coating which cannot gain a purchase on smooth cast surfaces. The same (ceramic)
refractory will often adhere tenaciously to heavily textured or undercut cast surfaces, and
probably require repeated treatments to fully dislodge the investment. In this instance, shell
removal is made difficult and time consuming because the textured surface of the design acts as a
key, into which the outer investment locks fast as the cast contracts.
Before progressing to fine finishing, the fettled cast may be given a light surface treatment such
as a SHOT-BLASTING, this provides the founder with a clear view of the cast’s surface
condition. Despite some artists’ concerns that shot or bead blasting removes significant amounts
of surface detail to affect the quality of their work, the air pressure levels and blasting media
used in art foundry workshops usually only removes surface material from the cast measurable in
microns (1µm = 0.001mm). Unless seriously mishandled, a finished cast which has been shot-
blasted should show no discernable reduction in surface quality when compared to a cast that has
been prepared by other means. Exceptions to this general rule include the use of shot blast media
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on antique or restoration projects, or on very thin walled casts which might be inadvertently
‘holed’. Some flat designs (thin plaques, bas relief, and sheet metals, etc), can suffer a
‘stretching’ effect if heavily blasted, distorting them from a flat plane. As a rule though, shot and
bead-blasting (glass bead peening) are perfectly legitimate and safe workshop procedures for use
on new casts.
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5. CORE MAKING PROCESS
Core Making Processes:
A core is a device used in casting and molding processes to produce internal cavities and reentrant angles. The core is normally a disposable item that is destroyed to get it out of the piece. They are most commonly used in sand casting.There are many types of cores available. The selection of the correct type of core depends on production quantity, production rate, required precision, required surface finish, and the type of
metal being used. Some core making processes are defined as under:
5.1 DIFFERENT TYPES OF CORE MAKING PROCESS
Sodium Silicate/ CO2 Process Molasses Process Shell process Green sand
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Cold Box Sodium Silicate/CO
2 Core-making Process
It is one of the easiest modern core-making processes. In this process, sodium silicate (4 -6%) is mixed with silica sand by either Batch type mixer or Continuous type screw mixer. After mixing coating of sodium silicate takes place on silica sand. The sand is rammed into a core-box and cured by passing CO2 through the core. CO2 dissolves in the water of sodium silicate
and forms carbonic acid. SiO2 + Na2O + H2O (l) + CO2 (g) → H2CO3 + Na2O + SiO2
Carbonic acid reacts with sodium silicate and forms silica jel. H2CO3 + Na2O + SiO2 → SiO2 (gel) + Na2 CO3 • H2O (glass)
The silica gel that is formed binds individual sand grains together. Sand temperature is critical in this process. The core should be between 25ºC to 30ºC (75ºF to 85ºF). Below 15ºC (60ºF) the reaction proceeds very slowly, and more CO2 or gassing time is required to fully cure the core.
Above 30ºC, excessive amounts of moisture evaporate during the curing process, resulting in a very weak and brittle bond. It should also be noted that the gel tends to hydrate, which causes a reduction in binder strength. This limits core shelf life to about one month.
Molasses Process7-10 % molasses is mixed with silica sand and filled in mould or core boxes then put them in ovens to dry at about 200oC. It takes time and is not suitable for mass production.
Shell ProcessIn shell process Silica and is coated with Phenol formaldehyde. The color would become light brown. This sand is Thermoplastic.Then it is filled in core box and heat at 200 oC, which allows the chemical components in the sand to bond together and form the shape within the core box.
There are two processes of coating of Phenol formaldehyde.Warm at 80-100 oC: Phenol formaldehyde is added in liquid form about 3-3.5% Hot at 120-130oC: Phenol formaldehyde is added in form of solid flakes about 3-3.5%.
Cold box ProcessCold box process consists of two parts:
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Polyol Phenolic Resins (1%)Isocynate (0.4%)
The "polyol" representing one of the components is a phenol-formaldehyde resin exhibiting benzyl ether character. These resins display the general formula:
in which the sum of m and n is at least two, and the ratio m:n is at least 1:1
The polyisocyanate is an oligomeric product of 2,4'- and 4,4' -diphenylmethanediisocyanate, and exhibits the following structure:
However, the difference in polarity of the polyisocyanate and phenolic resin limits the choice of appropriate solvents that are compatible with both components. This "compatibility" is nonetheless necessary to achieve complete reaction and curing of the binder.
Polar solvents are, for example, very appropriate for phenolic resins, but less so forpolyisocyanates. The situation is exactly the reverse when nonpolar solvents are used.The preferred nonpolar solvents are high-boiling aromatic hydrocarbons (generally in the form of mixtures).
Silica sand represents the bulk of the sand grades used for the cold box process and also the particle size of the sand has a major effect on the bending and tensile strength of the core produced using the cold box method. The fact must also be considered that the required binder level is directly related to the particle size.
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5.2 Chemical Characterization of Cold Box Resins and Activators
In the classic polyurethane-based cold box process, the binder represents a twocomponentsystem chemically composed of a polyol and a polyisocyanate.The "polyol" representing one of the components is a phenol-formaldehyde resin exhibitingbenzyl ether character. These resins display the general formula:
in which the sum of m and n is at least two, and the ratio m:n is at least 1:1 (x = -H or -CH2OH).
The polyisocyanate is an oligomeric product of 2,4'- and 4,4'-diphenylmethanediisocyanate,and exhibits the following structure:
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Both the phenolic resin component and the isocyanate are generally used in the form ofsolutions in organic solvents.However, the difference in polarity of the polyisocyanate and phenolic resin limits thechoice of appropriate solvents that are compatible with both components. This "compatibility"is nonetheless necessary to achieve complete reaction and curing of the binder.Polar solvents are, for example, very appropriate for phenolic resins, but less so forpolyisocyanates. The situation is exactly the reverse when nonpolar solvents are used.The preferred nonpolar solvents are high-boiling aromatic hydrocarbons (generally in theform of mixtures) exhibiting a boiling range above 150 C at atmospheric pressure. Esterswith sufficiently high boiling points are used as polar solvents.Despite all the advantages polyurethane binders offer to the foundry industry, the aromaticsolvents hitherto considered indispensable in them have created serious disadvantagesdue to emissions in production of core and mold components, and particularly after pouringoff. At the high temperatures prevailing during the casting operation, the binder componentsare subjected to a pyrolysis process involving creation of new, stable compounds. Inthe presence of aromatic hydrocarbons, this pyrolysis process generates benzene, tolueneand xylenes, which exhibit particularly great thermal stability.
The development of the new cold box binder systems at HÜTTENES-ALBERTUS followed acompletely different path.Instead of the previously favored high-boiling aromatic hydrocarbons, plant-based solvents(methyl esters of vegetable oils) were used for the resins and activators.Aside from the ecological advantages of these odorless, environmentally friendly, non-pollutingand CO2-neutral natural products, the new solvents meet all physical requirementsfor polyurethane binder systems. They are high boiling, sufficiently low in viscosity,odorless, and are classified as innocuous at the workplace. They are furthermorenonflammable, a property that considerably simplifies transportation and storage of theresin and activator solutions prepared from them.
CatalystsThe gasses required for curing are members of the family of tertiary amines. These tertiaryamines vary with respect to their vaporization points:DMEA Vaporization point 36 - 38 CDMIA Vaporization point 65 - 68 CTEA Vaporization point 87 - 89 C
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5.3) Sands
The sand molding matrix is of special significance in the cold box process. In this method,the question of sand is equally as important as in the other mold and coremakingprocesses used in the foundry. The economy of the process and quality of the castings tobe produced depend to a critical extent on the sand being used.In principle, all refractory matrices used in the foundry industry can be employed for thecold box process. These essentially represent silica sand, chromite sand and zircon sand.
a) Silica SandsSilica sand represents the bulk of the sand grades used for the cold box process, althoughno statistical data on the exact distribution of the sand matrices exist. European silicasands nearly exclusively date from the Tertiary and Cretaceous periods, and represent theproducts of weathering of quartz-rich prehistoric rocks in sedimentary deposits. Silica sandsare considered of high quality when they contain only minor amounts of accompanyingminerals. Such accompanying minerals largely represent the following products:Feldspar, mica, glauconite, alkaline metal oxides and carbonaceous minerals.It is known that these impurities depress the sintering point of silica sand to a greater orlesser extent. In the cold box process, the presence of alkaline metal oxides andcarbonaceous minerals furthermore affects sand workability and the required level ofcatalyst.
Foundry-quality silica sands are basically conditioned by:Washing, desludging, grading and drying.Aside from the above criteria, the grain shape and surface character are of significance in afoundry silica sand.The grain shape is differentiated according to the following types:
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b) Chromite SandThe starting material for chromite or chrome ore sand, as this material is often termed inpractice, is chrome ore. As in the case of silica sand, this material is appropriatelyconditioned for use in the foundry.Use of chrome ore sand in the cold box process is always necessary when casting defectssuch as finning occur in gray cast iron. Finning is one of the group of defects caused bysand expansion, and because of the pertinent coefficients of thermal expansion isencountered particularly frequently when silica sand is used (cf. Table 1, Page 10).
c) Zircon SandThis represents a zirconium oxide silicate, in mineralogy termed "zircon". Althoughzirconium is relatively widely distributed in the earth's crust, there are only few workablezircon sand deposits. The zircon sand used in the foundry industry mainly comes fromAustralia. Both zircon sand and chrome ore sand are used to fight the casting defect offinning.
The following must be considered when chrome ore sand or zircon sand are processed in acold box mixture:♦ They reduce the flow of the molding sand mixture.♦ Due to the reduced flow mentioned above, an increase in the shooting pressure isrequired to achieve an identical level of core compaction.♦ This results in a reduced corebox service life.♦ They also reduce the bench life of the molding sand mix.♦ If mixtures of chrome ore sand and silica sand are used, the flow is similarly reducedand in some cases where long shooting paths are involved accompanied by demixing(also applies to mixtures of zircon sand and silica sand).
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5.4) MIXING
"Working With the Cold Box Process in the Coremaking Department of a Foundry".However, working with the cold box process requires more than just the Gasharz (Resin),Aktivator, catalyst and refractory matrix components discussed above. Mixers, coreshooters, coreboxes, gassing apparatus and similar equipment are also necessary. Themixing principles that dominate the German foundry industry will be described below.The purpose of blending a molding sand mix is to coat the refractory matrix componentswith the gas-curing resin and activator. The following facts illustrate the enormous effortinvolved in this task. Silica sand H 32, AFS 46, exhibits a theoretical specific surface areaof 77 cm2/g. This means that 50 kg of this silica sand possesses a theoretical specificsurface area of 3850 m2. This corresponds to the area of a hall with sides 62.0 x 62.0meters long. In a very brief time, this 3850 m2 area must now be coated with a quantity ofonly 360 mL resin and 360 mL activator in a mixer.
Agitator-Type Mixers
Operation of an Agitator-Type MixerThe motor-driven agitator or mixing beam propels the mixture, which is forced outwardagainst the walls of the vessel by the rotary motion of the agitator. The continuousmovement forces layers of the mixture upward along the walls of the vessel until themixture falls back towards the center into the bulk of the material. Figure 1 illustrates thisoperation.
The mixing capacity depends on the following parameters:
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♦ Rotational speed (rpm) of the agitator♦ Peripheral velocity at the tip of the agitator♦ Ratio of diameter to height of mixing vessel♦ Mixing equipment design♦ State of wear of mixing equipment
Vibratory Mixers
Operation of a Vibratory Mixing VesselThe mixing vessel (Wall A) is set into oscillating motion (B) by the horizontal rotation of aneccentric that is instrumental in producing the vibratory movement. The resultant frictionbetween the mixing vessel (1) and mixture (7) causes rotary movement (C) of the mixture.Part (b) of Figure 2 shows a momentary situation. This clearly demonstrates that the inertiaof the mixture (7) always causes it to contact only a small area x (c in Figure 2) of thevessel wall. Compressive forces D (c in Figure 2) originate at this rapidly oscillating 13interface, and are directed toward the interior of the mixture. These cause "liquefaction" ofthe mixture and furthermore produce agitation of the mixture within itself (d in Figure 2).Figure 3 shows the various mixing equipment system designs.
The efficacy of the mixer depends on the♦ Diameter of the mixing vessel♦ Angle of incidence♦ Width of transport blades♦ Frequency of the vibratory motor♦ Diameter of the oscillation cycle
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5.5) Transportation In the present sense, transportation only refers to conveyance of the molding sand from themixer to the core shooter. In series-production foundries such as an automotive foundry,such transportation is accomplished using automatic floor conveyers. However, foundriescertainly still exist even in Germany where this transportation is accomplished by manualmeans. The transportation time should be as brief as possible. There is a great danger thatsand workability problems will arise, since the molding sand is also stored in the hopper ofthe core shooter .
Core Shooters, Gassing EquipmentThese points will only be discussed to the extent that this is indispensable. More preciseinformation is available from the pertinent manufacturers.From the point of view of the binder manufacturer, it is important that the core shooters bematched to the size of the cores to be produced with them. The reason for this requirementmay be explained as follows.
Shooting of a 1 kg core on a 25 L core shooter should be avoided. If this were to happen,the result would be that the core shooter - with a molding sand supply of 200 kg - wouldonly exhaust this supply in approximately three hours. In case of outdoor temperatures inexcess of 30 C, storage of the molding sand for a three-hour period could lead to problemsin core fabrication (cf. Section 4).
As a rule of thumb, the reaction rate doubles with every 10 C increase in thetemperature.
A further point to be observed when installing core shooters and gassing equipment is toalso provide for a dehumidifier (chill dryer). As already known, the activator of the cold boxsystem reacts with the moisture in the air, forming a polyurea and CO2. The polyurea doesnot form stable binder links between the individual sand grains, i.e. the core does notachieve its required strength. Moreover, the polyurea is not thermally stable, anddecomposes to yield nitrogen when exposed to the heat of casting.
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5.6) Pattern Equipment for Core Production
Coreboxes
Coreboxes for the cold box process may be manufactured from various materials includingWoodWood/plasticAluminum/plasticGrey IronSteelThe selection of a construction material depends on the number of cores to be produced inthe corebox. Combinations of wood and plastic, or better of aluminum and plastic (Slide 1)can definitely be used as corebox materials in a jobbing foundry with lot sizes of 20 to 1000cores. In selecting the plastics for use in corebox construction, it should be noted that theplastic must be resistant to the components used in the cold box process. When the lotsizes mentioned above are exceeded, it is advisable to perform a cost analysis for thepattern equipment.After selection of the materials to be used, the second most important consideration in coreproduction is the design of the corebox.Slide 1 shows a core with quite simple geometry. Cores of this or a similar shape arealways produced in vertically parted coreboxe
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A cylindrical injection port may be seen in the upper part of the corebox. This should be aslarge as possible and as small as necessary. A port that is as large as possible permits themolding sand to be shot into the corebox with the lowest possible pressure. Furtheradvantages of a large injection port are:- Increased corebox service life (lower wear)- Less cleaning expense.- Reduced binder buildup below the injection port- Improved, faster permeation of the catalyst (large area)- Reduced catalyst consumption
The port should also be as small as necessary to avoid the following disadvantage:- The large injection port section must be separated from the core if it cannot be used as a coreprint.
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6). COLD BOX MACHINE
DCH – 1010 COLD BOX MACHINE
This machine has brought about good results to the company. It is equipped with vertical core
removal mechanism and the horizontal split core box combined with the effective top blow
method.
1. Specification
- Core Box Size : 1000 X 1000 X 260
- Operating System : Manual , Joggin, 1-Cycle Auto
And automatic systems
- Power Source : Air Cylinder
Hydraulic Cylinder
Motor
- Blowing Method : One time blowing with Multi-Holes
- Blowing Volume : Max 50kg
- Working Air Pressure : 5-7 kg/cm3
- Blowing Air Pressure : 2-4 kg/cm3
- Power : Main – AC415V, 50HZ, 3PH
Working: AC220, 50HZ
- Accessories : Gas Generator
Scrubber Tank
Batch Mixer
Hydraulic Unit
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6.1)Description of the
machine
The machine is composed to Top Board at
the top, Columns in the middle and bed at
the bottom. Hopper for supplying sand,
blowing valve and air tanks are installed at
the Top board and rails are at the bottom of
the board. Travelling on the rails blow head
Gassing Head are to be moved between the
blowing position and sand supply position
by the Traverse Cylinder.
Clamp table at the bed raises the bottom
core box. At body of the machine, fork
unloader, dust collector for cleaning core
box, cleaning device for blow plate and
quick change device for changing quickly
the blow plate, up ejector plate, up core box and bottom core box installed.
1) Clamping Device
Bottom core box lifting cylinder installed at the bed of the machine join the bottom and up core
box. Core ejector cylinder is installed at the clamp table for ejecting the core in the bottom core
box.
2) Blowing and Gassing device
Blow plate is presses to the upper core box by the head cylinder. Compressed air in the air tank
blows the sand in the blow head inside the core box.
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After blowing, gassing head moves to the upper core box by the press cylinder and blow the gas
inside the core box. Up Ejector is installed at the gassing head for ejecting the core in the upper
core box.
3) Unloading Device
After completing gassing, the up eject pins eject the core into the bottom core box. Then the
bottom core box comes down. Bottom eject pins installed at the clamp table raise the core in the
core box and the unloader moves forward to receive the core. The core is moved on the fork of
the unloader. The dust sprayer installed at the unloader cleans the core box when the unloader
moves back to original position.
6.2) Outline of operation
Joggin Operation
This is for adjusting each mechanism manually. At this condition, interlock is not in act and
therefore have to pay attention at this system.
Manual Operation
This is for checking and adjustment of each mechanism before starting automatic operation.
Each mechanism is operated by the manual operation switch filled to the control panel and
operation box.
Single cycle automatic operation
This is for the operation of one complete cycle of motions of each mechanism linked by timers
and limit switches.
Single cycle means the processes from clamp table up to taking out of shell core.
Repeat automatic operation T h I
This is the automatic operation of the above simple cycle operation after another by the
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function of wait timer (cleaning timer)
6.3) Start position of this machine
When each mechanism is under the following conditions respectively, this machine is regulated
to be at start position. Before operating the machine, check that each part is stopped at start
position.
Part Name Position
__________________________________________
Traverser Sand feed Side
Clamp Table Down
Unloader Rear
Head Cylinder Up
Bottom Cylinder Down
Dust Sprayer Stop
Blower Stop
Bottom Ejector Down
Dump Gate Closed, Up
Gas Cylinder Up
Blow Plate Reverse Stop
Blow Plate Clamp Clamping
Upper core box clamp pin Insert
Core box exchange hook Loosened
Core Box Moving Transfer Rear
Rail Supporter Down
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6.4) Checking points before operation
* Check the amount of the lubrication and hydraulic oils.
* Check and drain the air filter
* Check the air pressure at every air outlet points
* Check for any oil/air leakage
* Check the switches
* Check the bolts and nuts
* Check the amount of the Ammine Gas
* Check whether the contents in the scrubber tank is as follows
(Water + Phosphoric Acid = 3+1 )
* Check whether the pipes for gassing and scrubber are connected tight.
* Check whether there are any inflammable materials
a) Preparation for Operation
After completing the installation of the machine, piping electric cable connection
- Switch on the Power S/W and supply power.
- Supply air to the Air-Inlet valve
*Working Air Pressure: 5-7kg/cm2
*Inlet air pressure: 2-4kg/cm2
- Select manual for operation
- Check whether the units are at original position.
- For the units that uses 3 way solenoid valves, operate supplying back pressure.
- Set the time for automatic operation
- Supply sand to blow head
- Reset the blow counter
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b) Operation
a) Manual operation
Run manually before operating
- Turn on the operation switch
- Push the operation preparation switch
- Turn the operation system selecting switch to manual position
- Turn on switches for operation
- Check and make it sure that the units are in original position
- Operate each units manually
b) 1-cycle Automatic Operation
When there are not any troubles while operating manually, operate the machine according to the
following orders for 1-cycle automatic operation.
- Turn the operation system witch to 1-cycle automatic position
- Set the time of the timer
- Push the automatic start switch and related switches.
c) Automatic Operation
Operate the machine automatically by turning the operation system, selecting switch to
automatic position.
When there are not any troubles while operating manually, operate the machine according to the
following orders for 1-cycle automatic operation
Turn the operating system selecting switch to 1-cycle automatic position.
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1) Adjustment
Adjusting blowing Air pressure
Even though working pressure is 5-6kg/cm2 set the blowing pressure 2-4kg/cm2 using the
pressure reducer
Adjusting Cylinder Speed
Adjust the volume of the air by handling the cylinder speed control valve
Adjusting the traversing position of the units
Control the stopper installed at the bracket for cushion cylinder.
Adjusting the timer
Adjust the timer when its not in operation. If you adjust the timer while operation it shall not be
adjusted and even cause disorder of the timer.
Timers Time (sec)
Blowing 2-4
Gassing 5-10
Purging 20-30
Program Controller
Change the program only after stropping the operation of the machine
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2) Core Box Exchange
1. Lift up clamp table
2. Make it down the ejector plate
3. Remove manually the ejector plate clamp
4. Disassemble upper core box clamp
5. Lift up the ejector plate
6. Make it down the clamp table
7. Move blow head to blowing side
8. Install Jig for the blow plate
9. Make the blow head down
10 Lift up the clamp table
11. Move the core box transfer carriage to ‘exchange’ position and put it on the rails.
12. Make the clamp table down.
13. Lift up blow head
14. Lock the core box exchange hook
15. Disconnect the piping and electric connection to the core box
16. Move the core box on the core box transfer carriage
17. Fix the core box to the core box transfer carriage
18. Disassemble the core box exchange hook
19. Move backward the core box transfer carriage
To assemble the core box follow the opposite direction of the above orders.
3) Cleaning the blow pate
Operating method to clean the blow plate
- Make it sure that the blow head is at sand position
- Lift up the blow plate
- Assemble the blow plate
- Make the blow plate down
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- Tilt the blow plate
Assemble it according to the opposite direction of the above orders
Sketch of layout of a cold box machine
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6.5) Gas Generator
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a) Structure
Gas generator is made for hardening the core by supplying amine in the form of gas.
b) Characteristics
The volume of amine can be controlled automatically by the timer.
As the surface exposed to amine is made of stainless steel materials. , there’s no harm to the
machine owing to the gas.
As the outlet of amine and amine tank are always kept in cool condition by the cooling device, it
can be used even though the temperature goes up.
c) Preparation
Check whether amine is enough in the tank through the gauge.
Start the air heat switch
Open the valve and check the air pressure gauge.
Try gassing 3 or 4 times without the gas.
Measure the volume of amine by controlling the timer
Installed at the switch panel.
Check the operating condition of the scrubber.
d) Adjustment
Set the timer: Timer for gassing:: 2-4 sec
Timer for purging :: 5-10 sec
Set the pressure: Pressure for gassing :: 0.5-1 kg/cm2
Pressure for purging :: 1.5-2 kg/cm2
Adjust the volume of amine by looking at the CC Cup at the
back of the generator.
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e) Operation
When the generator is started gassing valve (1) and amine valve (4) are operated at the same
time. According to the time set by the timer, gassing valve (1) stops and then, purging valve (2)
starts operation. During the time set at the timer. When the time is passed the purging valve (2)
and amine valve (4) stop their operation and then, amine valve (3) starts operation. 1cycle
operation is completed when amine valve (3) stops after the time set at the timer.
f) Caution
-Use dry air for spraying amine gas
-If possible make short the length of pipe between the gas
generator and gas head.
g) Maintenance
When repair is necessary, make sure the following:
-Close the air valve
-Close the amine valve
7.) SCRUBBER (SCABBER UNIT)
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Scrubber is a unit for neutralization of the amine gas through the Ph Meter.
a) Preparation
-Check if the Ph is below 7.
-If the Ph is over 7, exchange the water and phosphate.
b) Adjustment
-Pour phosphate and water with the ratio of 3:1
-Set the Ph Meter as follows
*Low: 4
*High: 7
c) Operation
-Turn on the Fan
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-Turn on the pump
d) Caution
-Keep the ratio of phosphate and water and make it 3:1 by adding water or phosphate.
Troubles and Measurements
Troubles Reasons Measurements
In part hardening is not
performed well
Air-vent is blocked *Clean the back of the vent
*After Operating the scrubber,
check if the air flows well
Core boxes are not matching
completely
*Replace the seal for core
boxes
*Check if the core boxes are
assembled well.
*Check if the core boxes are
damaged
Leakage between generator
and gassing head
Check the connecting pipe
The volume of resin generated
and gassing is not measures
exactly
Check by measuring
manually. If necessary, repair
the measuring device.
Hardening is not stable (from
time to time hardening is not
performed well)
The volume of amine is
smaller than required
Increase the volume
Purging is not done at all The volume of air is smaller
than required
Check the purging device
The regulating valve is
polluted
Loosen the bolt and clean
inside the valve
Pressure goes up The valve gets wornout Exchange with new one
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8.) TESTING
This report contains the results of emission testing at sampling locations before and after the core
machine exhaust gas scrubber as part of a Core Making Emissions Study. All testing was
conducted in the foundry of D.C.M.
The specific objective of this test was to determine the emission levels of a selected group of
Hazardous Air Pollutants (HAPs) and Volatile Organic Compounds (VOCs) produced during
core making and to evaluate the impact of the acid scrubbers on those emissions. The resultant
emissions are expressed as mass of emission per kg of resin (kg/kg) as well as parts per
million (v/v).
The testing performed involved the collection of air samples during the sand and binder mixing,
core blowing, and catalyst addition processes. Process and stack parameters were measured and
include: the weights of the sand and binder; stack temperature, pressure, volumetric flow rate and
moisture content. The process parameters were maintained within prescribed ranges in order to
ensure the reproducibility of the tests. Three sixty-minute sampling periods were performed for
this test at both the inlet and at the outlet stack of the gas scrubber. Samples were collected and
analyzed for selected target compounds .
Triethylamine (TEA) results expressed as parts of TEA per million parts
of air are reported for results from the outlet stack of the scrubber.
Results from Test EC for the measured analytes are shown in the following table.
Analyte
Triethylamine (ppm, v/v) 1(Pre Scrubber) and <0.041 (Post Scrubber)
The concentration of triethylamine was found to be below the method
quantitation limit at the post scrubber position.
It must be noted that the reference and product testing performed is not suitable for use as
emission factors or for purposes other than evaluating the relative emission reductions associated
with the use of alternative materials, equipment, or processes. The emissions measurements are
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unique to the specific castings produced, materials used, and testing methodology associated
with these tests, and should not be used as the basis for estimating emissions from actual
commercial foundry applications.
8.1) Description of Process and Testing Equipment
Ford automotive I-4 engine block cores were prepared using a multicavity
corebox on the DCH 1010 core machine in the Production foundry. Sand and
Ashland 305/904 core binder were weighed and mixed at a rate of 1.75% binder based on
sand in the core sand mixer above the core machine. The sand/resin
mixture is introduced (blown) into the core tooling in the core machine. Next, a measured
amount of the catalyst triethylamine (TEA) gas is heated to 84oF and allowed to expand into
the sand in the core box to cure the core, finally purge air is heated to 84oF and blown
through the sand mixture in the core box. All these gases are exhausted to the wet
gas scrubber charged with sulfuric acid at pH 2 or less. Engine block cores consist of four parts,
crankcase, Journal, Headslab, & Water Jacket. In one blow, either two each of the crankcase
and journal cores or three each of the Headslab & Water jacket cores are produced.he part print
is studied for the overall dimensions, tolerances, material etc. blank development is done
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highlighting the loading, dimensional requirements, etc. The component material is 1.5mm thick
COPPER with an annual quantity requirement of 6,00,000 Nos.
8.2)The analytical results
of the emissions tests provide the mass of each analyte in the sample. The total mass of the
analyte emitted is calculated by multiplying the mass of analyte in the sample times the ratio
of total stack gas volume to sample volume. The total stack gas volume is calculated from
the measured stack gas velocity and duct diameter, and corrected to dry standard conditions
using the measured stack pressures, temperatures, gas molecular weight and moisture
content. The total mass of analyte is then divided by the weight of the resin used to provide
emissions data in pounds of analyte per pound of resin
9.) CORE MAKING REVOLUTION
9.1) IntroductionIncreasing demands for greater productivity and lower overall costs are forcing foundries to examine how existing processes and technologies can be redesigned to become more cost-effective and environmentally more acceptable. The core room is a critical area for high production ferrous and non-ferrous foundries and corebinder technology has been the focus of intensive development effort by both Foseco and SMC in recent years.This article describes two of the latest gas-cured core making techniques which are perfectly suited to meet the highest demands in terms of quality, productivity, and environmental considerations -the ESHAMINE Plus phenolic-urethane cold box process and the ECOLOTEC process.
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9.2) The ESHAMINE Plus process
PrinciplesThe phenolic-urethane cold box (PUCB) process is the most widely used gas cured binder process in the foundry industry and has been the preferred core making process for high production foundries for the past 20 years or so. In this process a tertiary amine(part 3) catalyses the reaction between the phenolic resin (part 1) and polyisocyanate (part 2) through the formation of an intermediary complex (A), i.e
The speed of this reaction, and therefore the core hardening reaction, is essentially determined by the rate of formation of the amine intermediate complex. This, in turn, is determined by the size ofthe amine molecule. Until now the following chemicals have typically been adopted in the phenolic-urethane cold box process; c TEA (triethylamine) DMEA (dimethyl ethyl amine)c DMIA (dimethyl isopropyl amine) All these substances exist as liquids at ambient
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temperature and must be vapourised to function effectively in the core making operation. Under cold ambient conditions problems of amine condensation in the gas supply lines or in the corebox itself are not uncommon.In contrast, the patented ESHAMINE Plus processutilises specific phenolic-urethane binder part (1) and (2) components and a tertiary amine whichexists as a gas at room temperature and is the most reactive of the tertiary amine family.This chemical is: TMA (trimethylamine).
Key characteristics of the tertiary amines commonly used in the phenolic-urethane cold box process are shown in table
Process benefits – production experience
The use of trimethylamine in the phenolic-urethane process has received very little attention over the past 20 years due to difficulties in controlling and optimising dosing levels. However, the recent development by SMC of a novel gassing equipment design now facilitates the use of TMA and enables substantial benefits in terms of productivity and reduced amine catalyst levels. Production tests to date with the ESHAMINE Plus process have shown gassing times reduced by up to 78% and purge times reduced by 54% compared to conventional DMEA or TEA catalysed core making operations. These reductions have been found to have a significant impact on the overall cycle time of the core machine and core output has increased by 30% on average .
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In addition to improved productivity, the quantity of amine catalyst required is significantly reducedresulting in material cost savings and a cleaner environment. Measurements in the core storage area for example have indicated that amine emissions can be reduced by in excess of 50% when compared to DMEA or TEA cured cores. A further benefit of the ESHAMINE Plus process is that amine scrubber unit maintenance and service costs are significantly reduced due to the lower quantity of amine required for the curing process. A summary of benefits is shown in figure 3. Furthermore, due to the faster and more efficient curing mechanism in the ESHAMINE Plus process, it has been observed that cores made using the process possess superior moisture resistance compared to conventionally catalysed phenolicurethanecold box processes, e.g with DMIA.
Process conversion
As TMA exists in the gaseous state, clearly changes must be made to the existing core machine’sgassing installation, or alternatively, additional new equipment must be installed. Advice on process conversion and equipment requirements can be provided by Foseco and SMC in collaboration with established and reputable core machine suppliers. The use of easily re-useable
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and re-fillable gas cannisters for the TMA provides further significant environmental benefits over conventional liquid amines which are often supplied in tanks, drums or containers and which require significant cleaning of residues before being re-used.
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9.3) THE ECOLOTEC PROCESS
In the ECOLOTEC process, a water-based alkaline phenolic resole resin is mixed with sand and then hardened by gassing with carbon dioxide. The carbon dioxide acts to reduce the pH of the resin, thereby initiating a cross-linking reaction with a complexing agent present in the resin solution. As this reaction mechanism is between a gas and the liquid resin, the rate of reaction is dependent on the temperature, pressure and flow rate of the carbon dioxide gas and temperature of the mixed sand.
Properties
As with most sand binders, the characteristics of the base sand have a significant effect on theultimate strengths of ECOLOTEC bonded cores. In addition to sand purity and chemistry, particle shape and particle size distribution are especially important factors.Ideally, the sand should be round grained or have rounded edges and have a particle size distribution spanning 3 sieves. As the quality of core depends on an effective reaction between the carbon dioxide gas and the ECOLOTEC(r) resin binder, an AFS of around 55 - 60 is most suitable as this promotes natural pressure build up within the core box during gassing (see figure 5). Where coarser sands of AFS 45 - 50 are unavoidable for whatever reason, then a more reactive ECOLOTEC resin should be used to ensure strength development in a sufficiently rapid time. Higher reactivity ECOLOTEC resins have been developed for applications where higher immediate strengths are required, or faster cycle times are desirable (see figure 6). Though the ECOLOTEC process involves curing with carbon dioxide, the mechanism for curing is completely different to that of a sodium silicate system. In the case of silicate the objective tends to be to gas at very high flow rates in order to obtain a certain degree of dehydration. In contrast
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with the ECOLOTEC process, it is is very important to avoid dehydration of the binder and to ensure that it is the cross linking bonding mechanism which takes place through optimised carbon dioxide temperature, pressure and flow rate. Positioning of gas ingates and vents is alsoimportant if dead areas of uncured sand are to be avoided (see figure 7)
Sand flowabilityThe flowability of phenolic resole CO2 mixed sand is slightly inferior to that of phenolic- rethane cold box mixed sand. However in most cases, satsifactory core compaction can be achieved through minor changes to core box venting or machine blow pressures. Recent development work in the laboratory and in pilot production trials has also shown that theaddition to the mixed sand of flowability agents can also have a significant impact on corecompaction, core strength and the ease of strip and release of cores from the core box. Work inthis area is continuing. Recent development work in the laboratory and in pilot production trials has also shown that the addition to the mixed sand of flowability agents can also have a significant impact on core compaction, core strength and the ease of strip and release of cores from the core box. Work in this area is continuing.
Thermal propertiesECOLOTEC bonded cores demonstrate outstanding thermal properties and are capable of excellent casting quality on all alloys. In the iron test casting (see figure 8), the ECOLOTEC process shows clear benefits compared to sodium silicate bonded coresand phenolic-urethane cores. ECOLOTEC cores show neither sand burn-on, norfinning defects. The breakdown of the cores is noticeably better than sodium silicate, whilst finning defects common with the phenolic-urethane system are not generally observed.
Effect on green sandDue to the alkaline nature of ECOLOTEC bonded sand, there is clearly an effect on the re-circulating green sand system of mixed core sand. The inflow of alkaline salts into the green sand from ECOLOTEC cores can result in strong activation of the bentonite clay.In those green sand systems where a fully activated bentonite is being used, conversion to ECOLOTEC for cores would normally necessitate a move to a partially activated bentonite to counteract the activating effect of the ECOLOTEC core sand.
ProductivityDue to the avoidance of the purging or flushing time necessary when using the henolic-urethane cold box process, core cycle times with the ECOLOTEC process are often shorther than with the PUCB process.
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9.4)Production experience
Case Study 1 - Improved casting qualityThe valve body core and casting shown in figure 9, was originally made in phenolic-urethane cold box. Despite the use of specialist coatings, finning defects were found in the valve body leading to high scrap rates. With ECOLOTEC cores, castings were produced free from fins and scrap levels were reduced.
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Case Study 2 - Avoidance of capital investmentAgain, the core in this example , was originally made in phenolic-urethane cold box. Coremaking production was restricted however, as the core room could only operate when the exhaust air was channelled to the cupola and the foundry only melted on five days per week. The foundry avoided the purchase of an amine scrubber by converting to the ECOLOTEC process. In addition to a more flexible and lower cost coremaking process, an added benefit was that – unlike with the urethane process – cores could be cast uncoated with excellent results.
9.5)Environmental considerations
Increasingly nowadays aspects of the environment are becoming a priority for foundries. Compared to other core making processes, the ECOLOTEC process provides significantly improved environment with respect to VOC emissions on core making and on casting. In terms of certain key compounds, emissions with the ECOLOTEC process lie below the allowable limiting values.
phenol 12 mg per m3 limiting value 20 mg per m3benzol 3 mg per m3 limiting value 5 mg per m3amine 1 mg per m3 limiting value 5 mg per m3
Residual materials from the ECOLOTEC process canbe disposed of as follows: Sand exposed to heat can be disposed of as Disposal Class 1 (phenolic-urethane core box sand is Class 2) Sand not exposed to heat can be deposited on a domestic rubbish tip. Initial pilot tests have also indicated that thermally regenerated sand can be re-used as core sand – work in this area is ongoing. It should also be noted that the carbon dioxide required for the hardening process is produced by extraction from the atmosphere – consequently there is no reinforcement of the ”greenhouse” effect by use of the ECOLOTEC process.Increasingly nowadays aspects of the environment are becoming a priority for foundries. Compared to other core making processes, the ECOLOTEC process provides significantly improved environment with respect to VOC emissions on core making and on casting. In terms of certain key compounds, emissions with the ECOLOTEC process lie below the allowable limiting values.
9.6) SummaryProduction foundries today are under increasing pressure to reduce costs and improve core roomefficiency, whilst at the same time ensuring compliance with ever demanding environmentallegislation.The ESHAMINE Plus and ECOLOTEC processes provide foundries with viable options to face up to this challenge.
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10) ADVANCES IN CORE MAKING TECHNOLOGY
Rapid advances are occurring in core design and production because of the need for reducing foundry and machining scrap and the need for binders that are environmentally friendly.Modeling programs that describe mold filling have made tremendous progress in the past 20 years in their ability to calculate metal velocities that can be used to minimize splashing, reoxidation, bubble trails, folds, and similar anomalies that degrade casting properties. Now, the industry is accelerating into new core design and production technologies.
Historically, core box designs were based on experience. Foundrymen have focused on metallurgy for a hundred years, but comparatively little has been published on core making technology such as box design, vent theory, and core quality measures.
10.1)Trends in Tooling Design
A review of tool design since the phenolic urethane cold box (PUCB) binders were introduced in the late 1960s will help understand the current trends. The 1970s were the practical beginning of the cold box era. During this time, significant investments were made to convert many shell, hot box, and sodium silicate bonded cores to the PUCB process. The economic benefits of the process derived from high production rates, and reduced core costs per unit produced.
The growth of cold box processes was impressive throughout the 1980s. New processes, including SO2-cured acrylic epoxy and ester-cured alkaline phenolic resins, were introduced, and improvements were made in the PUCB system. Equipment manufacturers introduced the appropriate gas generation, core making, and scrubbing equipment for the cold box processes. As the economic benefits found in the 70s became harder to improve upon, an emphasis was placed on understanding the effects of chemical variations and the physics of blowing and gassing all of the binders. Significant research was done in tooling design, and guidelines were developed to ensure that core makers could use the new technology and save money. These guidelines have appeared in AFS Transactions and have been published by several industry suppliers.
During the 1990s, high production cold box processes became affordable to foundries of all sizes and came to dominate the market. But the intellectual property once present in most captive pattern shops was lost because of downsizing and early retirements. In addition, some foundries began to outsource tooling design and core production to independent pattern and core shops. However, some “industry experts” kept up with the technology and continued their research and publication
In one case, an automotive company, a resin manufacturer, and some experienced computational fluid dynamics (CFD) professionals joined forces to develop ‘math models’ to simulate cold box
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core making. Arena-flow computer aided engineering (CAE) coupled cold box tooling design with process optimization, and the engineering model became a reality in 2001
This technology was built on over 30 years of experience with cold box core-making and fluid dynamics research. The technology will be as useful as solidification and machining software now used in the foundry industry. The technology offers foundries reduced time to market, tooling design flexibility, and core making process design.
The primary benefit is performance analysis of proposed tooling designs. This CAE technology assists designers with core geometry and layout for multiple cavity core boxes, blow tube selection and location, vent selection and location, and other aspects of tooling design. Complete processes can be modeled and optimized with respect to gassing equipment, core-making equipment, and consumables (resin, catalyst, sand, etc.) selection.
Tool design requires some input values to set up the geometry. A grid pattern for a water jacket core is illustrated.(Image A) Needed information includes:
CAD files representing 3D geometry of the core blowing machine, blow tubes, and core box geometry.
Sand characteristics (type, size distribution, density, and binder loading). Vent characteristics (type, size, location, open area). Process conditions (blow pressure and time, gas pressure and time, purge pressure and
time).
The software then solves equations for flow and calculates core blowing and gassing parameters. (Image B) Output information can be in animation and an image formed for detailed analysis. Blowing and gassing simulation can provide optimized tooling and process parameters, and the design can be finalized based on core quality, cycle time, and desired behavior, including cavity filling pattern, tool wear, and cleanliness.
The technology, coupled with precision core boxes, allows more complicated and accurate core and mold assemblies than previously possible. Progress is being made in automation to assemble complicated core packages with minimum labor.
10.2) New Binder Technology
Oxides, bubble trails, and subsurface porosity are some of the most aggravating defects encountered in castings. These anomalies are difficult to detect and are often not found until castings are machined. A blow hole and an associated oxide trail in a high performance head casting is illustrated. The gas came from a water jacket core, produced a layer of oxides, and collected in a boss where it produced a hole that was discovered during tapping.
There is a large amount of development work going on worldwide to improve the performance of core binders and to make them more environmentally friendly. There is renewed interest in sodium silicate, modifications of the PUCB and alkaline phenolic resins, and new binders being introduced. PUCB binders are the benchmark in the industry, and an industry goal is to develop products that are as fast as PUCB, provide an equally good casting surface, improve the shakeout
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behavior, and eliminate the use of noxious gaseous catalysts and scrubbers. LKBinder, GMBOND, and ECOLOTEC, are examples of recent innovations.
LKBinder is intended primarily for aluminum castings. It is reported to be free of odor, dimensionally stable, produce smooth casting surfaces, and be used in a variety of molds including green sand. The binder is in a water carrier and is thermally cured in a warm box. The heat evaporates water from the binder, causing cure at the pattern surface. When the core is partially cured, it can be taken from the core box, thoroughly dried, and placed in a mold.
After solidification, cores can be mechanically removed or placed in water and the binder dissolved. The system eliminates the need for a gas scrubber around the core machines and reduces ventilation requirements around work areas.
GMBOND is based on a unique protein that forms a reversible gel in water and dries to a rigid, partially crystalline polymer when the water is removed. Cores are made by removing moisture with heat. No reactive chemicals are used, so the core making area is safe for the workers. The binder is biodegradable, and there are no hazardous chemicals or wastes to deal with.
Cores made with GMBOND are dimensionally stable, produce a smooth casting surface, and are easily removed from aluminum castings. Emissions from castings made with protein binders are reported about a tenth of the level of Hazardous Air Pollutants (HAPS) found with PUCB binders.
The ECOLOTEC Process is based on an alkaline water-based P-F resin, cured with carbon dioxide (CO2). This material is also reported to provide a clean, safe, high-production, gas-cured core making process for aluminum, copper based alloys, iron, and steel castings.
Emissions during sand mixing, core making and core storage (SARA 313, Form R reportable compounds) are said to be dramatically reduced, as are emissions during pouring, cooling, and shakeout. The process involves no flammable components, and since cores are cured with CO2, no gas scrubber is required. This binder is a virtually odorless.
Core production rates with the ECOLOTEC Process often exceed those of other organic gas-cured processes. The curing gas cycle may be slightly longer than used for PUCB processes, but no purge cycle is required.
Casting surface quality is reported to be exceptionally good. Veining defects are virtually non-existent — without the use of “anti-veining” sand additives.
CORDIS, an inorganic system introduced in the early 1990s, is based on polyphosphate chemistry. The binder provides strength, collapsibility, humidity resistance, and enhanced flow of the coated sand. This system is in commercial use today. It reduces defects, and has excellent dry or wet shakeout characteristics.
Phenolic urethane systems are also being modified and improved for performance and environmental characteristics.
These developments include “Biodiesel,” or methyl ester solvents for lower VOC emissions during core making and lower HAP emissions at pouring, cooling and shake-out. Biodiesel
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solvent-based PUCB’s offer better release, dip and redry performance, and improved curing speed, which lowers the use of amine catalysts.
A new catalyst called DMIPA (dimethylisopropylamine) has also been introduced that has a higher reactivity than TEA. The high reactivity reduces catalyst consumption, causes faster curing, and improves the work place by reducing odor. This catalyst is not regulated under the new MACT standards for iron foundries.
Work also continues on improving the ester-cured phenolic cold-box system (ECPCB). This technology features a water-based binder with low VOCs, high hot strength, and low odor during mixing and core making and low smoke and HAP’s during pouring, cooling and shake-out. This product technology also exhibits lower expansion defects, especially veining in iron castings and hot tears in steel.
There is also a renewed interest in sodium silicate binders sparked by the environmental advantages, performance breakthroughs, and historically stable pricing. DevCo 285 is a modified, hybrid sodium silicate that produces dimensionally stable cores for all types of metals. It can be cured with liquid hardeners, CO2, heat, and with microwaves. The binder has virtually no odor or smoke during or after pouring.
10.3)Conclusions
The future of tooling design has become relatively clear. Computer aided design will play a significant role in complex cold box tooling, and the skills of manufacturing engineers will change to use it. Tool design will become more fully integrated into the design chain internally in Tier I foundries, Tier II jobbing foundries, and contract pattern shops.
Precision cores will open the way for mechanized core assembly to reduce the labor content.
Binders are rapidly evolving to minimize casting defects, minimize emissions, and produce smooth cast surfaces. Core removal from aluminum castings has historically been troublesome, but innovations in water soluble binders are rapidly eliminating this problem. The future for core technologies used in the foundry industry is full of promise.
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11). COATINGS (WASH)
Cores are coated with a refractory wash to increase the cores refractiveness and to produce a smoother metal surface in the cored cavity of the casting. These materials are called washes. They can be purchased in a variety of types and refractive strength. A common home made wash is graphite and molasses water mixed to a nice paint consistency.Water mangement can be applied right at the beginning of wash preparation where a lot of water is wasted and a possible automization can be applied as well after thorough study at the field. Out of my observations, I have listed few in tabular form as under.
PRE ASSEMBLY AREA : Water based washesWASH VISCOSITY (in secs)
1 Wash Zircon 16-182 Mix Wash 80:20 :: Zr:Gr 16-18
HPM LINE1 Alcohol based mould-cote-11 wash 12-14
SUPPLY OF DIFFERENT WASHES TO CORE SHOP-IWater Based Washes1. Terrapaint/graphite 16-20For Brushing1. Terrapaint/graphite 26-302. 80:20 (Zr:Gr) mix 16-203. Zircon 16-204. Arkolpal 14-16TWO PART AREAWater Based Washes1. Zircon Wash 15-182. Mix Wash 16-203. Terrapaint 15-18
MARUTI AREAWater Based Washes 1. Mix Wash 16-20
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2. Terrapaint/graphite wash (for barrel cores) 15-183. Terrapaint/graphite wash ( for FW/FE cores) 16-204. Arkopal 14-16
CORE SHOP IIWater Based Washes1. Terrapaint/graphite wash 17-192. Rheotec-161/g 21 wash 15-183. Mix wash 16-204. Arkolpal wash 14-165. Zircon Wash (w/jkt) 15-18
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11.1) Classification of mould and core coatingsMinerals: e.g. Aluminium silicate
Zircon silicateGraphite
Carrier liquid: Wateriso – Propanol
Delivery from: PowderPasteSlurry (Ready for Use)
The table below shows a general view over the Coating products fromHÜTTENES – ALBERTUS and their principle applications.
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11.2) WASH PREPARATION
How wash is prepared?
They buy chemicals from Gargi and water is added to those slimy or powdery chemicals to make less viscous hence a useable wash. Initially water is filled till the 100 lt. mark in the tanker and two bags of wash (paste form) is added to the tank. After a liltle bit of manually stirring, mixer is switched on for 30 mins. If still some solid particles are remaining then mixer is switched on for another 15 mins. Here viscosity is adjusted to approx 24 secs. Then they are diluted as per requirement in particular areas for specific cores. Then the tank is cleaned before next batch is prepared.
CONSTITUENTS
TYPE
WATER(Lt.)
ALCOHOL (KG)
TERRAPAINT / GRAPHITE PASTE (KG)
ZIRCON(KG)
MOLD COTE -11POWDER (KG)
MIN MIXING TIME (MTS)
GRAPHITE/TERRAPAINT Water Base Wash
100 ± 10 - 100 ± 5 - - 30
ZIRCON Water Based Wash
100 ± 10 - - 100 ± 5 - 30
GRAPHITE/NOLD COTE-II Alcohol Base Wash
- 20 ± 2 - - 13 15
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11.3) Washes Used in DCM
A) Water Based Washes
i) Zircon WashDISOPAST 2357 Disopast 2357 is a ready to use zirconium based mold /core coating with an aqueous carrier. A special combination of inorganic / organic suspenders and binders results in high solids level which ensures rapid drying possible. The result is an extremely compact, abrasion resistant coating. ZIRKOPAL 1853 Zirkopal 1853 is a pasty, white mould/ core coating based on zirconium silicate for dilution with water. It is equipped with a novel system of binders and suspending agents, which provide the mould coat with significant advantages. These include an improved high temperature performance including protection against sand expansion defects, an increased resistance to erosion and reduction of the gas evolution during pouring to a minimum. In practical use, this product gives very compact coatings, which are quite resistant to even very high temperatures and which completely shield the moulding material from the liquid metal. Smooth clean and gas free castings may thus be prepared.
ii) Graphite
KOALID G.W. Koalid GW is a blackish Grey coating based on graphite aluminum silicate and iron oxide with water as a carrier liquid. The coating has excellent suspension stability and owing to the refractory composition it is able to prevent the formation of finings and scabs The penetration tendency of cast iron melts is reduced as well. A clean and smooth surface finish can be achieved. This coating is suitable for high to medium cast iron castings. NEKROPAL 5930 E Nekropal 5930 E is a black refractory coating based on carbon containing raw materials, aluminium silicates and iron oxide. The carrier liquid is water. The coating contains a high percentage carbon. Combined with good cooling properties this carbon content allows a good peel of the coating from the casting surface. Because of the special suspension agent the coating exhibits excellent application properties and the suspension characteristic of the coating is very good.
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iii)Zircon Graphite
ARKOPAL 4044 Arkopal 4044 is a zirconium and graphite based mold /core coating with an aqueous carrier. It is a water-based coating with high solid contents for brushing applications. Arkopal 4044 maintains an excellent coverage and brush ability. Arkopal 4044 has got superior suspension property and ensures excellent finishing on heavy iron castings.
iv)Aluminium Silicate ARKOPAL MRW 94I Arkopal MRW 94 I is a ready to use water based mixed refractory coating for cores / moulds made by shell process. ARKOPAL 6172 XL Arkopal 6172 XL is a yellow coating based on high quality aluminium silicates and iron oxides and water as carrier. Arkopal 6172 XL grants low reactivity to metal oxides and excellent performance at high temperatures. Clean and smooth surface finish of the castings is obtained. ARKOPAL 6172 XLM Arkopal 6172 XLM is a yellowish coating based on high quality aluminum silicates and iron oxides and water as carrier. Arkopal 6172 XLM grants low reactivity to metal oxides and excellent performance at high temperatures. On account of the nature of the refractories used as fillers the coating is permeable, allowing the gasses generated from the decomposition of the binders to escape across the coating film without building excessive gas pressure. It also has good anti veining properties. ARKOPAL 6172 Arkopal 6172 is a reddish coating based on high quality aluminium silicates and iron oxides and water as carrier. Arkopal 6172 grants low reactivity to metal oxides and excellent performance at high temperatures. Clean and smooth surface finish of the castings is obtained. ARKOPAL 499 Arkopal 499 is a reddish brown coating of high quality aluminium silicates and iron oxides. Arkopal 499 grants low reactivity to metal oxides and excellent performance at high temperature. Clean and smooth surface finish of the castings is obtained. ARKOPAL 6423 Arkopal 6423 is a brownish coating based on high quality aluminium silicates, Graphites and iron oxides and water as carrier. Arkopal 6423 grants low reactivity to metal oxides and excellent performance at high temperatures. Nature of the refractory use as filler and as special additive the coating is more permeable allowing the gasses generated from the decomposition as the binders to escape across the coating film without building excessive gas pressure.
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ARKOPAL 6005 Arkopal 6005 is a Greyish colour coating based on high quality aluminum silicates and iron oxides and water as carrier. Arkopal 6005 grants low reactivity to metal oxides and excellent performance at high temperatures. Clean and smooth surface finish of the castings is obtained. B) ALCOHOL BASED WASHES
i) ZIRCON (Alcohol Based) ZIRKOFLUID RM 94 IZirkofluid RM 94I is a coating material based on zirconium. Alcohol is used as carrier liquid. The newly- designed binder and suspension system gives this coating material best application properties. A high zirconium ensures a dense layer and thus an excellent protection against penetrations and mould metal reactions. It also maintains a good adhesive and abrasive resistance. ZIRKOFLUID 1219Zirkofluid 1219 is a coating material based on zirconium. Alcohol is used as carrier liquid. The newly- designed binder and suspension system gives this coating material best application properties. A high solid content assures a dense layer and thus an excellent protection against penetrations and mould metal reactions. It also maintains a good adhesive and abrasive resistance. ZIRKOFLUID 3256Zirkofluid 3256 is a light Green alcohol based zirconium ceramic coating for steel, iron and heavy section non-ferrous castings. It has good suspension properties and is ready for use at 62-66 ° baume. It has excellent peel off from the castings due to exceptional resistance to metal penetration. ZIRKOFLUID PASTE 94 IZirkofluid paste 94I is a coating material based on zirconium. Alcohol is used as carrier liquid. The newly- designed binder and suspension system gives this coating material best application properties. A high zirconium ensures a dense layer and thus an excellent protection against penetrations and mould metal reactions. It also maintains a good adhesive and abrasive resistance. ZIRKOFLUID 3565Zirkofluid 3565 is a coating material based on zirconium and ceramics. Alcohol is used as carrier liquid. The newly- designed binder and suspension system gives this coating material best application properties. A zirconium and ceramic combination gives a dense layer and thus an excellent protection against penetrations and mould metal reactions. It also maintains a good adhesive and abrasive resistance.
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ii) GRAPHITE (Alcohol Based) KOALID RM 94 I Koalid RM 94I is a ready to use coating based on graphite and magnesium silicates. Alcohol is used as a carrier liquid. A new suspension and binder system gives the product good manufacturing properties as well as good suspension stability. Owing to its basic materials it is able to prevent the formation of finings and scabs. The penetration tendency of cast iron melts is reduced as well. A clean and smooth surface finish can be achieved. KOALID PASTE 94 I Koalid Paste 94I is a coating based on graphite and magnesium silicates in paste form. Alcohol is used as a carrier liquid. A new suspension and binder system gives the product good manufacturing properties as well as good suspension stability. Owing to its basic materials it is able to prevent the formation of finings and scabs. The penetration tendency of cast iron melts is reduced as well. A clean and smooth surface finish can be achieved.
iii) ZIRCON GRAPHITE (Alcohol Based) ARKOFLUID 21 RM Arkofluid 21 RM is a zirconium and graphite based mold /core coating with alcohol as a carrier. It is alcohol-based coating with medium solids suitable for brushing and spraying application. Arkofluid 21 RM maintains a good coverage and brush ability and due to its superior suspension property it ensures uniform coverage and thus excellent finish even on heavy iron castings.
iv) MAGNESITE (Alcohol Based) ARKOFLUID 5848 Arkofluid 5848 is a light brownish cream coating based on a high quality magnesite with Isoproponal as a carrier. The coating exhibits excellent flow properties. The refractory filler system performs best on moulding materials such as Olivine (basic refectories). Mould/metal reactions and penetrations are avoided.
v) ALUMINIUM SILICATE (Alcohol Based) ARKOFIX 4476 Arkofix 4476 is a Red – Brownish, Zircon free coating based on selected Al Silicates with alcohol as a carrier liquid Due to its mineral composition Arkofix 4476 works very efficiently
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against sand expansion defects and metal penetration. If used on cold box cores the tendency to defects is reduced by pyrolysis carbon.
11.4) Possible automization for water management in wash preparation
Current Scenario: The wash is prepared by mixing it in a mixer for approximately 30 minutes with approximately qty of water to form a very thin paste so that it is suitable for using on the cores. Then this very thin paste is taken to the respective area to be applied on the core. Before its application on the core it is diluted to required viscosity number as given on the information sheet ( or as the required properties of the product, demanded by the customer) . So there’s is possibility of wastage of water at two ends and in addition to wastage of water there is possibility of wastage of the wash prepared because of manual error or automatic mechanical fault. The picture displays the application of wash on the barrel cores before they are taken to the ovens for baking at 120 degree Celsius. Baking is another important process in core making , which is required for specific hardening , specially for cores made by cold box process.
Next in the image is a vertical oven where the core is taken and baked before taking it to the production line.
Automization : Possible automization , which I could suggest people at D.C.M was combining the two stages of dilution of wash slurry into thin paste, in a single process by using a intensive mixer, as used in preparation of core sand for mixing it with binders and catalyst. After studying few types of mixers I came to a conclusion that the following type of intense mixture , which is manufactured by Ganesh Foundries is Suitable for them. It saves time and wastage of water and possibility of errors reduces to 50 percent than previous situation.
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Intensive Mixer
Ganesh intensive sand mixer is specially designed for mixing core sand and similar materials. The s type impellers are fabricated and hard spot welded. The wear plates are exchangeable. Pneumatic door opening is provided. This is advanced design for big and small foundries.The breakers are also provided to break the heterogeneous mass. Ganesh co2 sand mixers and Ganesh no-bake sand mixers are also available.• Designed for high speed mixing of green sand & other additives to prepare high capacity moulding sand. Shorter mixing time, Economic usage of benlonite, consists of mixing chamber, mixing blades, motorized gear drive for mixing blades & blender with drive unit.
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APPENDIX
I Fate of Intermediate Biodegradation Products of Triethyl Amine in a Compost-based Biofiltration System
Biodegradation of organic pollutants is becoming increasingly popular for process industries generating large flows of flue gas with low pollutants’ concentration. Adoption of stricter emission policies in recent years and increasing costs of chemicals and disposal of hazardous wastes generated from chemical treatment technologies have been the main driving force behind the development and optimization of biological treatment systems. The technology is still under development in terms of economics, equipment, process
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kinetics, and operational skills and different layouts and flow trains are being proposed including biofiltration, biotrickling filter, and bioscrubber (Burgess et. al., 2001). In biofiltration, microorganisms immobilized on an organic porous support bed metabolize pollutants in contaminated gaseous stream passing through into less harmful products (van Groenestijn & Hesselink, 1993; Ergas et. al., 1994). Apart from nutritional and environmental requirements of the biomass, porosity and bulk density of the bed media are important for the effect they have on the gas phase pressure drop across the bed. Amines are widely used as catalysts in casting operations. They are also the major pollutants in the gaseous emissions of chemical manufacturing factories. During the production of casting cores with the so called cold-box-process, polyurethane is used as a binder in the sand core. Considerable amount of amine vapor is used in this process and is partly liberated to the ambient air. Tertiary amines, such as triethyl amine (TEA) are the main gaseous catalysts for polymerization reactions comprising the majority of nitrogenous emissions (Borger et. al., 1997; Strikauska et. al., 1999; Busca & Pistarino, 2003). TEA has a very low odor threshold and exposure to it may cause adverse health effects such as asthma and visual disturbances (Belin et al., 1983; A kesson et al., 1985). Metabolic pathways of TEA in humans have been studied (A kesson et al., 1988) but information on microbial degradation of TEA is limited. In contrast to poor results obtained under anaerobic conditions (Kawahara et al., 1999), Tang et al. (1996) reported that 100% removal efficiency of TEA at loads up to 140 gm-3h-1 in a laboratory-scale reactor. Other studies have suggested suitable biodegradation potential of amines (Tang et. al., 1996; Chou & Shiu, 1997). As such, biofiltration seems to be an appropriate method to treat waste gases containing these pollutants. This study was conducted to investigate the performance of biofiltration system in treating triethyl amine-laden flue gas from casting operations under various conditions of inlet concentration, moisture content, and loading (organic and hydraulic). Specifically, the fate of intermediate products of TEA in a pilot plant system is evaluated
Filter Media and Microbial Culture Filter media was prepared by blending of sieved compost and wood chips. Municipal compost (equivalent diameter 2-5 mm) with a C:N:P ratio of 100:7:2, 37.8% organic matter and a pH value of 6.8 was obtained from a local composting facility. Wood chips (2-5mm) were added as bulking material to produce a 60:40 v/v ratio of compost-wood chip. The inoculum consisted of municipal activated sludge from the local regional wastewater treatment plant. The following nutrient and buffering solution was also added to the activated sludge (g dm-3): KH2PO4, 5; K2HPO4, 2.5; Potassium, 0.2; sodium, 0.64; Calcium, 5; Magnesium, 2; Chloride, 3.7; phosphorus, 1.15 (Auria, et. al., 2000). Operational and performance parameters.
The critical parameters include Empty-Bed Residence Time (EBRT), Mass Loading Rates (MLR), Removal Efficiency (RE) and Elimination Capacity (EC). EBRT is the time a parcel of air will remain in a empty biofilter and overestimates the actual treatment time. MLR define the amount of contaminant entering the biofilter per unit area or volume of filter material per unit time. Both terms are normalized, allowing for comparison between reactors of different sizes.
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RE and EC are used to describe the performance of a biofilter. RE is the fraction of contaminant removed by biofilter and EC is the mass of the contaminant degraded per unit volume of filter material per unit time. Removal efficiency is an incomplete descriptor of biofilter performance because it varies with contaminant concentration, air flow, and biofilter size and reflects only the specific conditions under which it is measured. The EC is normalized with respect to volume by definition and allows for direct comparison of the results of two different biofilter systems.
Diagram for bio-filteration setup
Gas samples were collected at the inlet, outlet, and in the 5cm plenum between the sections. The amount of TEA was measured by UV spectrophotometer (UV/VIS-911, GBC CO, Australia) at a wavelength of 215 nm. For measuring pH, 1 g of biofilter bed material and 20 mL distilled water were blended and agitated for 10 min and measured by a pH meter (691-Metrohm, Switzerland). Moisture of biofilter bed material was measured by weight loss of 2 g solid sample after being dried at 106°C for 24 h. Heated water was circulated around the bed exterior and connected to a precision thermostat (Atbin Co.) to control temperature within 1 °C. Temperature was maintained at 30 °C and measured using alcohol in a glass thermometer with a range from –10 to 110 and a scale division of 1°C. Gas flow rate was measured using flow meter (Omega Fl-2016) with units of l/min. A water-filled manometer with a minimum division length reading of 1 mm water column was used to measure pressure drop across the column.
Results and Discussion
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At the startup of biofilter, influent TEA concentration was adjusted to 20 ppm at an organic loading rate of 6 g m-3h-1 and relative humidity of 50-55%. Also, water temperature in humidifier was adjusted to 28±2°C. Superficial gas velocity was 57.3 m hr-1, corresponding to a residence time of 48 seconds. The observed acclimation period was 3 weeks because microorganisms in municipal activated sludge had not been acclimated to the target pollutant. Decreasing of removal efficiency was observed with a lag period after increasing the inlet concentration with subsequent increase in the removal efficiency after gradual acclimation of microbes to the pollutant.
Elimination Capacity EC shows what portion of the incoming organic loading is being biodegraded. As the loading rate is increased, a point of saturation or maximum EC corresponding to maximum microbial substrate utilization rate is observed. This limitation is due to the effect of high concentrations on the Monod kinetics of biodegradation (Nevin & Barford, 2000). In some cases, it is known that very high concentration of substrate can become inhibitory (Devinney et. al., 1999). In order to evaluate EC, OLR can be increased through increased influent concentration or flow rate (reduced HRT). By increasing inlet TEA concentrations while maintaining constant flow rate (HRT=48 s), OLR was increased. As shown in Figure 3,, there is a linear relationship between EC and OLR up to an OLR value of 72.3 g m-3h-1(inlet TEA concentration of 250 ppm). Beyond this value, a flattening of the curve is observed with eventual decreasing trend for OLR values greater than 120 g m-3h-1. This is a bit lower than the results reported before (Tang et. al., 1996) on the onset of inhibitory effects at loading rate of 140 g m -3h-1 for the compost/chaff biofilter. The difference may be attributable to the higher column length of 100 cm and HRT value of 60 vs. 48 s for
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this study.
Ammonia/Ammonium Due to the alkaline nature of TEA, initially an increase in pH was observed. Because of equilibrium relationships, fraction of ammonium ion at high pH is low and observed effluent ammonia concentration was high. With time, further adaptation of microbial population resulted in degradation of TEA and consequent reduction of pH in the system. It took more than a month after the startup period for the effluent ammonia concentration to fall below the 25 ppm level. Ammonium concentration inside bed increased with time with the first section having the highest levels measured. As has been suggested previously (Sheridan, Curran, and Dodd, 2002), ammonia in the first step is absorbed on to the biofilter packing material, giving rise to the formation of ammonium ion. The bacterial consortium then degrades this ammonium to nitrite producing H+, which reduces the pH of the system, thus increasing the ability of the biofilter to absorb more and more.
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Nitrate Presence of ammonia in the effluent is a function of the degree of nitrification in different sections of the reactor. An equilibrium relationship between fractions of ammonia gasammonium ion determines the availability of ammonium ion for onset of nitrification by nitrifiers. In actual operational conditions, the degree of approach to equilibrium is difficult to ascertain but the ratio of ammonia-ammonium is a function of many factors including temperature and pH. The higher the population of nitrifiers, the higher the rate of disappearance of ammonium ion and subsequent rate of dissolution of ammonia gas into the solution. As seen in figure 5, minimal nitrate levels are observed in the first section and the highest concentrations are in the third section implying low microbial population at the inlet section. The rate of increase in nitrate concentration is not uniform in the reactor indicating a gradual adaptation of nitrifiers with optimal conditions finally reached in the third section. A potential ramification of the trend of nitrate increase is thatsufficient contact time should be allowed in the reactor so as to avoid high outlet ammonia concentrations and better utilization of available reactor length for establishment of nitrifiers. Periodic reversal of flow direction may aid in increoverall nitrifier biomass but the dynamics of microbial population under different conditions warrants further research.
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II Table of properties of Gray cast iron
(The American Society for Testing Materials (ASTM) numbering system for grey cast iron is established such that the numbers corespond to the minimum tensile strength in kpsi. Thus an ASTM no. 20 cast iron has a minimum tensile strength of 20 kpsi. Note particularly that the tabulations are typical values. Multiply strength in kpsi be 6.89 to get strength in MPa.)
III BINDERS and ADDITIVES
Binders are added to a base sand to bond the sand particles together (i.e. it is the glue that holds the mold together).
Clay and waterA mixture of clay and water is the most commonly used binder. There are two types of clay commonly used: bentonite and kaolinite, with the former being the most common.[14]
OilOils, such as linseed oil, other vegetable oils and marine oils, used to be used as a binder, however due to their increasing cost, they have been mostly phased out. The oil also required
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careful baking at 100 to 200 °C (212 to 392 °F) to cure (if overheated the oil becomes brittle, wasting the mold).ResinResin binders are natural or synthetic high melting point gums. The two common types used are urea formaldehyde (UF) and phenol formaldehyde (PF) resins. PF resins have a higher heat resistance than UF resins and cost less. There are also cold-set resins, which use a catalyst instead of a heat to cure the binder. Resin binders are quite popular because different properties can be achieved by mixing with various additives. Other advantages include good collapsibility, low gassing, and they leave a good surface finish on the casting.Sodium silicateSodium silicate [Na2SiO3 or (Na2O)(SiO2)] is a high strength binder used with silica molding sand. To cure the binder carbon dioxide gas is used, which creates the following reaction:
The advantage to this binder is that it occurs at room temperature and quickly. The disadvantage is that its high strength leads to shakeout difficulties and possibly hot tears in the casting.
AdditivesAdditives are added to the molding components to improve: surface finish, dry strength, refractoriness, and "cushioning properties".Up to 5% of reducing agents, such as coal powder, pitch, creosote, and fuel oil, may be added to the molding material to prevent wetting (prevention of liquid metal sticking to sand particles, thus leaving them on the casting surface), improve surface finish, decrease metal penetration, and burn-on defects. These additives achieve this by creating gases at the surface of the mold cavity, which prevent the liquid metal from adhering to the sand. Reducing agents are not used with steel casting, because they can carburize the metal during casting.Up to 3% of "cushioning material", such as wood flour, saw dust, powdered husks, peat, and straw, can be added to reduce scabbing, hot tear, and hot crack casting defects when casting high temperature metals. These materials are beneficial because burn-off when the metal is poured creating voids in the mold, which allow it to expand. They also increase collapsibility and reduce shakeout time.Up to 2% of cereal binders, such as dextrin, starch, sulphite lye, and molasses, can be used to increase dry strength (the strength of the mold after curing) and improve surface finish. Cereal binders also improve collapsibility and reduce shakeout time because they burn-off when the metal is poured. The disadvantage to cereal binders is that they are expensive.Up to 2% of iron oxide powder can be used to prevent mold cracking and metal penetration, essentially improving refractoriness. Silica flour (fine silica) and zircon flour also improve refractoriness, especially in ferrous castings. The disadvantages to these additives is that they greatly reduce permeability.
Parting compoundsTo get the pattern out of the mold, prior to casting, a parting compound is applied to the pattern to ease removal. They can be a liquid or a fine powder (particle diameters between 75 and 150 micrometres (0.0030 and 0.0059 in)). Common powders include talc, graphite, and dry silica; common liquids include mineral oil and water-based silicon solutions. The latter are more commonly used with metal and large wooden patterns.
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IV SAND TESTING IN FOUNDARIES
The testing process is divided in to three stages: sampling of the bulk material, sample preparation, and testing.
Sampling is usually done at three different points of the process: upon first arrival from the supplier, en transport for processing (usually on a conveyor), and after processing. In each situation it is important to take a representative sample by mixing the sand or by taking multiple samples in different locations. Also, the sample must be stored in an air tight container to keep from spoiling it.
There are more than 25 basic tests, however only the important ones for the given casting process are used. The basic test measure the following parameters: wet tensile strength, mouldability, friability, moisture content, permeability, green compression strength, compactability, loss on ignition, volatiles content, grain size & distribution, dust (dead clay) content, and active clay content. Each of these tests can lead you to obtain specific characteristics of sand which can be crucial quality of casting. Advanced testing tests for other parameter, such as splitting strength, shear strength, and high temperature compression strength.
Sand control
Green sand is made up of basic sand (shell sand), bentonite or another binder, pitch powder or coal dust, and uninvited dust. Green sand properties cannot be standardized for all foundries and castings as such, yet place to place and job to job the specifications can be set to maintain minimal amount of rejection. A basic set of parameters to test are:
1 Fineness number (grain size/AFS Number) of the base sand2 Moisture content in the mixture (ranges from 2-7% depending on the casting method)3 Permeability (ability of compacted mould to pass air through it)4 Total clay content (dust content)5Active clay content (presence of active bentonite/clay which can readily bond)6 Compressive strength
For parameters 1, 2, 4 and 5 standard bulk material sampling methods can be applicable or sampling can be done with help of sand muller, sand sampler and sand splitter to do it in a standardized manner.
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BIBLOGRAPHY
REFERENCE BOOK AUTHOR
The complete handbook of sand casting C. W. Ammen Mold & Core Test Handbook American Foundry Soceity
Research Papers by Arena Flow LLC, Ashland Specialty Chemical Company, Foseco Metallurgical Inc., HA International LLC, Hormel Corporation, JB DeVenne Inc., and Laempe-Reich Company, Ursula und Emil BergerWEBSITES
www.wikipedia.org www.http://www.gargi-india.com/ http://www.foseco.com.tr/ www.foundrymag.com http://sharif.edu/~torkian/TorkianetalBiofilConfNov06.pdf
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