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GUJARAT TECHNOLOGICAL UNIVERSITY

MSMT NOVEMBER 2013 SOLVED QUESTION PAPER

ANKITKUMAR BRAHMBHATT

11/30/2013

PARUL INSTITUTE OF ENGINEERING AND TECHNOLOGY DS FIRST SHIFT(MECHANICAL)

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Q.1 Answer any seven out of ten. 14

1. Explain the construction properties of Ionic or Electrovalent bond.

ANSWER: IONIC:

1) They are rigid,Unidirectional,Crystalline in nature. 2) Ionic Solids are bad conductors of electricity in their solid state. 3) Ionic solids are good conductors of electricity in their moltern state. 4) Ionic Solid have high melting and boiling temperatures. 5) Ionic Solids are freely soluble in water but they are slightly soluble in organic

solvants. ELECTROVALENT:

1) They are bad conductors of electricity. 2) This Covalent solids are directional in nature. 3) Crystal of covalent bonding are strong,hard,and have high melting points. 4) Covalent solids are insoluble in water. There are soluble in organic solvents like

benzene,toluene,etc.

2. Explain secondary bond and state its characteristics.

ANSWER: It is also known as waander waals bonds secondary bonds. They are formed in the elements or compounds whose electron configuration is such that very little electron transfer is taking place between the atoms. Due to Dipole attraction Types:Dispersion,Dipole,Hydrogen.

Characteristics:

1) Molecular Compounds are generally transparent to lights. 2) Molecular Compounds are generally good insulator, with the oxception of water . 3) Molecular Compounds have low strength as they are held by weak forces of attraction. 4) Molecular compounds have low melting points.

3. Define: (1) Space lattice (2) Unit cell.

ANSWER: Space Lattice: During Solidification of metals, their atoms are take up fixed positions in a regular pattern, referred as space lattice.

Unit cell: The minimum value of the crystal which gives an idea of the atomic structure of a metal through its volume is called is called Unit cell.

4. Define: (1) Density (2) Melting point.

ANSWER: Density: The density of the material is the weight of it per unit volume.

Melting Point: The Temperature at which solid metals get transformed into liquid state is called Melting Point.

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5. Write short note on a super conductivity.

ANSWER: Super Conductivity::It is the Phenomenon of abrupt drop of resistivity of some materials, at a temperature called super conducting transition temperature before absolute zero is reached .It is due to the condition by the drift of electrons in the direction of the applied electric field being opposed by irregularities within the lattice.

6. Explain thermal expansion and thermal diffusivity.

ANSWER: Thermal Expansion: It is increase in dimension of a material on application of heat. It depends upon the interatomic and intermolecular forcesae well as on structural arrangement.

Thermal Diffusivity: it is the ratio of thermal conductivity of a material to its heat capacity per unit volume.

h=Kt/C where, Kt=Thermal Conductivity ,C=Specific Heat Capacity.

Thermal Diffusivity is the rate at ehich a disturbance in temperature of one part of a body travels to another part.It is also a measure of how little the distribution is attempted as it travels from point to point.

7. Write definition of Equilibrium diagram.

ANSWER:

The Solidification of Metal Alloy is Clearly understood by means of equilibrium diagrams.

• These are graphical representation of the changes in state due to variation in temperature and concentration.

• This indicate the nature and constitution of the alloys and the amount and the composition of the phases in a given system.it is also called constitutional diagram or Phase diagram

The Equilibrium Diagram

• The temperature composition diagram shows the changes of structure taking place during heating& cooling. This diagram is known as an Equilibrium Diagram. On

X axis: Metal Composition Y axis: Temperature Scales are plotted. The full name of this diagram is “Thermal Equilibrium Diagram" known as Phase Diagram or Constitutional Diagram.

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Fig: Phase Diagram

8. Write definition of solid solution.

ANSWER:

• In liquid stage metal form homogeneous liquid solution, The solid Solution is formed. If Solvent &Solute atoms are of similar size and electron structure, solid solution forms very readily if elements A in B forms solid solution in B by its 10%.

Fig: Types of Solid Solution

9. Define an alloy and binary and ternary alloy.

ANSWER:

An Alloy is an intimate mixture with metallic properties and is composed of two or more elements of which at least one is metal.

While the other is constituents or elements are known as alloying element, The cast iron,brass,Wrought iron,Steel,Bronze,White metal,Gun Metal, Duralumin and Mangalium are all alloys.

Binary and Ternary Alloy: Pure metal are considered as single phase, likewise the solid solution is also a single phase.

If pure metal and chemical compounds are in existance together in an alloy then in existance together in an alloy than in that alloy there exists two phases which are different from each other .in this way solid solution & pure metal together will give two phase .

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10. Define heat treatment and its objectives.

ANSWER:

It is sequential process of heating and cooling the steel component to get desired combination of properties in the component.

• Heating Component at higher temperature called austenitizing temperature, during which the previous structure of steel is converted in to Austenite phase.

• Holding the steel at austenitizing temperature for some time period so that formation of homogenous austenite can occur throughout the entire cross section of the part.

• Cooling back the part which is having homogenous austenitic structure to the room temperature at a particular cooling rate depending upon the properties required.

• Reheating of component to a higher temperature but lower than lower critical temperature and cooling again this is an optional process and performed if required.

Objective Of Heat Treatment

To improve combination of different properties.

To remove internal residual stresses from the component after basic manufacturing processes such as casting,forging,Rolling.

To improve grain size of the material.

To increase the hardness of the material.

To improve the toughness of the component.

To improve machinability of the material.Etc

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Q.2 (a) Explain time temperature transformation (TTT) curve. 03

ANSWER:

OR

(a) Explain pit furnace with neat figure. 03

ANSWER: Small size parts to be heat treated can be charged in a pit furnace.

fig: Pit furnace

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(b) Describe normalizing process. 03

ANSWER:

Normalizing

• It is defined as heating the steel to austenite phase and cooling it in the air. When steel is cold worked the crystal structure and the metal may be brittle and unreliable.

• The internal structure of the hot worked forged part may also be discoed owing to being worked at a very low temperature.

• It can also be seen that a variable finishing temperature will result in a variable structure for forging of the same carbon content.

• Likewise if a casting is poured at a somewhat indefinite temperature and cools at different rates in different parts, it may be unreliable. Normalizing is therefore, used particularly for the following purpose

1. To eliminate coarse grained structure.

2. To remove the internal stresses that may have been caused by working..

3. To improve the mechanical properties of the steel.

Purpose Of Normalizing

• To obtain desired microstructure and mechanical properties.

• To improve the Machinability of low carbon steels.

• To eliminate coarse grained structure resulted from working operation such as rolling, Forging etc.

• To modify and improve cast dendritic structure and reduce segregation by homogenizing the micro structure.

• To improve tensile strength of casting and forging component.

• To improve weld structure after welding process.

Process

• In normalizing ,steel is uniformly heated to a temperature which causes complete transformation to austenite .Different normalizing temperature and resulting hardness with respect to different carbon content is shown in the table .

• The steel is held at the Austenizing temperature for sufficient amount of the time for the formation of homogeneous austenite structure through the cross section. The soaking time is one hour per25 mm thickness of the component.Cooliing is done in still air in a uniform manner, which is faster than furnace cooling.

• Application of the normalizing Process

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• To obtain uniform structure.

• To refine the grain size.

• To obtain desired strength of too soft & ductile steel.

• To reduce internal stress. To improve weld structure.

• To Remove the carbide network from the grain boundaries hypo eutectoid steel.

• To improve engineering properties of steel.

OR

(b) Explain optical principal of microscope with neat figure. 03

ANSWER:

Principal: It works on the principle of reflection of the light rays.

Fig: Ray Diagram Of Metallurgical Microscope.

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(c) State the sequential steps of preparing a micro-specimen. 04

ANSWER:

1) To examine the internal details % structure of the metal specimen of 1cm,size should be prepared.

2) The surface of the specimen should be prepared by filing & grinding for grinding the specimen use emery paper of grades 1 and 0.after grinding on one emery paper. This will clear the scratches from the surface by grinding.

3) After Completing the rough grinding using grade 1 emery paper, fine grinding should be done by using 0,00,000,0000 emery papers. If zero grade fine emery papers are not available then used equivalent emery papers of 200grit,320 grit,400 grit and ,600 grit for the purpose of polishing.

4) The disc covered with shifon velvet containing diamond dust or dimontine should be rotated. On this rotating disc the final polishing of the surface of specimen should be done.

5) After final polishing of specimen obtain its surface like mirror and free from scratches.

6) he specimen surface should be immersed in etching reagent to make the grain boundaries visible. Without etching usually specimen can not be seen under the microscope. Etching imparts unlike appearances to the metal constituents and thus makes metal structure apparent under the microscope. Before etching the specimen should be thoroughly washed in running water.Innerse the polished surface in the etching reagent or by rubbing the polished surface gently with a cotton swab wetted with the etching reagent.

7) After etching again wash the specimen thoroughly and allow it to dry.

8) Now the specimen can be said ready to be studied under microscope.

OR

(c) Classify cast iron .give difference between white cast iron and grey cast iron. 04

ANSWER:

WHITE CAST IRON GREY CAST IRON It is white in colour It is having Grey Colour It is brittle It is soft material It is very hard It absorbs Vibrations Low Compressive Strength It is having less ductility Poor Mechanical Properties Melting Point is 1150 to 1200°C Manufacture Anvil, Wheel of railway coach Pipe and Pipe fittings, Agricultural

Equipments.

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(d) State the effect of phosphorus, sulphur,silicon,manganese as impurities on C.I. 04

ANSWER:

Effects

Phosphorus:

• It is an impurity in the cast iron makes it fusible and increases the fluidity. • It makes the cast iron brittle hence its content is limited mostly to 1%. • The cast iron containing P can be used to cast intricate shapes of the castings. • P lower the melting point and reduces shrinkage. • Strength of cast iron is slightly improved by P i.e up to 0.3%

Sulphur:

• It is harmful to have sulphur present as an impurity in cast iron. • It decreases the viscosity of the CI and makes it hard and brittle. • It tend to react with iron and forms the FeS which is low melting point compound and

it increases the possibilities of cracking at elevated temperatures known as HOT SHORTNESS.

Silicon:

• The silicon in the CI is 2.5%. • It promotes the formation of free graphite in cast iron.so it makes it soft so that its

machining can be done easily. • Blowhole does not appear in the casting if this impurity is present in the casting. • It gives freedom from oxides and blow holes by remaining oxygen as Sio2 and

promotes Fluidity.

Manganese:

• Impurity promotes the formation of carbide and makes the cast iron white and tough. • The cast iron is protected by Mn against harmful effects of So Amt of Mn is set

according to the S content. • MnS increases the Tensile strength and hardness, Mn improves the soundness of

casting.

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OR

(d) Draw neat sketch of Iron-carbon equilibrium diagram. 04

ANSWERFigfigfifigfi

Fig: Iron Carbon Diagram

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Q.3 (a) Write the properties of copper and give four use of copper, with reasons for its selection. 03

ANSWER:

Properties of Copper:

1) It is having Shining Yellowish red colour.

2) It is anti corrosive metal.

3) Density is 8.9 gm/cm3.

4) It is Good Conductor of Heat and Electricity.

5) Melting point is 1083°C.

6) It is having FCC Crystal Structure.

7) Machinability is very good.

8) It can be easily welded.

9) It is easy to cast.

10) It can be hot and cold worked.

11) Tensile strength 180-200 N/mm2

12) Hardness is 30-40 B.H.N

If annealed we can get elongation up to 50-60%.

Use Of Copper & Reason for its Selection

1) Electrolytic copper is good conductor of electricity &hence the electrical conductors & wires are produced by using electrolytic copper.

2) Copper is forming solid solution with zinc, therefore it is used for producing brass. By changing its percentage content its strength can be increased. Its properties can be imported by cold working .Therefore to produce different variety of brass, the copper is used.

3) Copper used to form its alloy known as Gunmetal. The gun metal is tough and have good strength. It is corrosion resistant. Therefore gun metal is used to produce pump parts, bolt & nut, Bushing etc.for ships building.

4) Copper alloy aluminium bronze has good strength &toughness. It is resistant to corrosion due to the effect of atmosphere, acid and salt. Therefore it is in gears, valves stem, pump parts,bushings,propeller nut etc.

5) Copper is heat conductive materials, hence used in radiators pipes& fins. 6) Copper has high heat conductivity so used in locomotive fire box, water heating

equipments etc.

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7) Due to its shining it is used in medals, buckles and name plates.

OR

(a) Compare high carbon steel and tool steel. 03

ANSWER:

TOOL STEEL: Tool and Die steels may be defined as special steels which have been developed to form ,cut or otherwise change the shape of a material into a finished or semi finished product.

Properties of tool steel

1) Slight change of form during hardening.

2) Little risk of cracking during hardening.

3) Good Toughness.

4) Good Wear Resistance.

5) Very Good Machinability.

6) A good Degree of Thorough hardening.

7) Resistance to decarburization.

HIGH CARBON STEEL:

C:0.6-0.8 %,Having Ferrite+Pearlite Micro structure,Hardness:350-600 B.H.N, Tensile strength:765-1420°C,Yield Strength:645-1170.

Die,Saw,Screw-Driver,Band Saw, Anvil Face,Hammer,Winch,Laminated Spring, Cable Wire, Big Dies of Cold Press,Chisels,Shearing blades, Punch & Drill, Spanners etc,are made from high carbon steel.

(b) Explain cooling method of alloy steel as per BIS. 03

ANSWER:

OR

(b) Give appropriate material for following. (1)Cycle frame (2) car body (3) piston ring (4) hacksaw blade (5) anvil. 03

ANSWER:

Cycle Frame: 50 Carbon(Vehicle Spring Steel),Carbody:C-Mn lighter ,

Piston Ring: Alloy Cast Iron ,Hacksaw Blade: Carbon Mn Steel or Hardened Steel ,

Anvil: White Cast Iron(WCI).

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(c) Differentiate brass and bronze. 04

ANSWER:

BRASS BRONZE Brass contains alloying elements like lead,Zinc,Silicon,Tin

Bronze contains alloying elements like Zinc,Tin,Lead,Iron,Aluminium,and Nickel.

It is Corrosion resistant & possesses good strength.

It is resistant to heat and corrosion high temperature strength is good. It resists oxidation.

Pipes,Tubes,&Fittings,Plumbing Goods, Hardware, Small gears, Pump Impeller, Valve & Its Fittings, Ornamental Castings, High cast part, Structural Parts, Bearing Steam Pipe Fittings, Marine Castings,Hydrallic Valves etc,are made from brass.

Pressure Castings,Bushings,Bearings,Steam pressure castings,Gears,Pumps,Heavy Duty parts, Marine Equipments, Valve Sheet, Valve Guide, Valve Stem, Acid Resistant pump, Dairy Equipments etc are made from bronze.

By increasing the Zinc Content in brass it is becoming Cheaper.

In Comparison to brass this metal is costlier.

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(c) State merits and demerits of adhesive materials. 04

ANSWER:

MERITS(any four)

1) Time for joint making is less. 2) They are moisture resistant materials. 3) They are free from the attacks of insects. 4) They can be used to join very thin parts. 5) It acts as an insulator between the two parts to be joined. 6) Different types of materials can be joined together. 7) High temperature is not required to make the joint. 8) Less skill is required to make the joint. 9) Good finished joints are obtained. 10) Simple design is sufficient to make the joint.

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DEMERITS(any four) 1) If surface cleaning is improper then poor joints results. 2) Intricate equipments required to provide heat & pressure for joint making. 3) Joint has lesser strength. 4) The joints damages due to more heat & moisture. 5) This joint is less stable in comparison to metal joints. 6) Testing methods for testing these joints are not developed.

(d) What are the ceramic materials? Give the classification of ceramic materials. 04

ANSWER:

• Ceramic are the materials produce from inorganic substance and are non metallic. They possess good thermal & electrical insulation properties.

• Ceramic word is derived from a Greek word keramos which means potter man's clay, but modern ceramic are the mixture of metallic & non metallic elements.

• Ceramic products are tiles,bathtub,sanitry wares, surgical instruments, auto parts& tools.

• Today the production of ceramic tiles in the world is getting momentum. In India Spartech ceramic of India limited is the leading manufacturer.

• The other manufacturer are Hindustan sanitary wares,EID,Parry & Naysor are also producing sanitary wares.

• Application base classification of ceramic are

Fig: Classification of Ceramic Material

CERAMIC

CEMENTS ABRASSIVE GLASSES CLAY PRODUCTS REFRACTORIES ADVANCE CERAMIC

STRUCTURAL CERAMIC CLAY PRODUCT

WHITE WAVES FIRE CLAY SILICA

BASIC SPECIAL

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OR

(d) Write the difference between thermoplastic and thermosetting plastics. 04

ANSWER:

THERMOPLASTIC THERMOSETTING PLASTIC It is produced by addition polymerisation. It is produced by condensation

polymerisation. Its Structure is linear and Chain Type Its Structure is cross linked Its Strength is less. Its Strength is more Its Structure is granular It has polymeric type of structure. This plastic cannot be used for higher temperatures.

This can be used at higher temperatures.

P.V.C,Acrylic,Polyethylene polystyrene are the examples of thermo plastic.

Phenolics,Epoxy,Melamine,are the examples of thermo setting plastics.

It is used to produce toys,Toiletwares,and fan blades,etc

It is used to produce Radio TV cabinets, Body of Phones, Automobile parts.

Q.4 (a) Explain uniform corrosion and pitting corrosion. 03

ANSWER:

Uniform: This type of corrosion initially occur on some portion of the surface and then spread on the whole surface. Continuous reduction in metal volume is caused by this corrosion. As this type of corrosion occurs equally on whole surface hence it is called "Uniform Corrosion".

If the parts are not produced from the corrosion resistant material, then strength of them are reduces due to this corrosion. The ways of preventing it are change of material and coating the surface with corrosion resisting material. This type of corrosion results into grater loss hence parts are to be produced using corrosion resistant material.

Pitting: This type of corrosion occurs due to metal loss by the electro chemical process from the surface of positive polarity parts. Its effect is seen on limited surface area but it is serious. The corrosion occurs very fast and can not be noticed till the part fails. Usually the type of corrosion is seen in aluminium parts but in humid environment SS parts are also corroded by it. The formation of crack by due to breakage of protective layer anodic region forms on the part surface.

The surface surrounding to this anode behave as cathode giving rise to galvanic cell. Small holes are developed on the parts surface by this type of corrosion. Repairing is costly. The dimension of the part are reducing based on the depth of pits, which reduces the area resisting the stress and part is failing.

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OR

(a) Explain galvanic and crevice corrosion. 03

ANSWER:

Galvanic: When a cell is made by using less active metal cathode with active metal anode, then destruction of cathode occurs very fast in comparison to its normal rate. Less active metal destruct very fast under electro chemical action. This is called as Galvanic Corrosion, It is proportional to the difference of electric potential and surface area. It is caused when two dissimilar metals comes in contact.E.g joint of Copper, Copper earth connection with steel pipe which gives rise to galvanic cell.Galvenic Corrosion is dependent on

1.High potential difference between anode & cathode

2.More Acidic Electrolyte

3.More Oxygen Concentration in electrolyte nearer to cathode.

Crevice: It is localised electrochemical corrosion Occurring at crevice and udnershiled surface where stagnant solution can exist. It is Occurring and gasket,rivets,bolts,between valve seats, valve disk etc.

It is caused to SS,Titanium,Copper,and Aluminium Alloy, The crevice formed at joint allow liquid to enter into them and they are narrow enough to keep the entered liquid stagnant.

Fibrous gasket acts as wicks, absorbs an electrolyte solution and keep it min contact with the metal surface. This developes location for crevice corrosion. The mechanism of this corrosion is similar to that of pitting.It initiates anodic Cathodic reaction on surface to cause crevice corrosion.

(b) Write differences of erosion and pitting corrosion. 04

ANSWER: (Write any four point)

EROSION PITTING It is caused due to separation of surface coating under effect of velocity.

It occurs due to metal loss by the electro chemical process from the surface of positive polarity parts.

The rate of Corrosion is more. Its effect is seen on limited surface area but it is serious.

The pump impeller, pipelines and pipe fittings becomes victim of this corrosion if solid matters are following with liquid flow.

The corrosion occurs very fast and cannot be noticed till the part fails.

Reduction of velocity, change in atmosphere and change in energy of solution can reduce the amount corrosion occurring.

It is observed in Al parts but in humid environment SS parts are also corroded by it.

Pipe surface carrying liquid and gas gets eroded due to this corrosion.

The formation of crack due to breakage of protective layer anodic region forms on the parts of surface. The surface surrounding to

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this anode behave as cathode giving rise to galvanic cell.

When metal layer breaks in pipe by reosion,than it cannot be repaired. Due to striking of liquid in condenser pipes,tubes,agitator and vessels their surfaces are more eroded.

Small holes are developed on the part surface by this type of corrosion. Repairing of the surface having such pits is costly as many many number of pits are produced in surface having such small pits is costly as many many numbers of pits are produced in surface by this corrosion.

The Dimension of the parts are reduced based on depth of pits, which reduces the area resisting the stress and part is failing.

OR

(b) State industrial application of electrolysis. 04

ANSWER:

Application Of Electrolysis.

1) To obtain galvanized products by developing layer of Zinc on Steel. 2) The parts are used in marine application are plated with cadmium layer to protect ferrous

metal parts from corrosion. 3) Nickel plating is done to protect parts surfaces against corrosion and to provide them

attractive &Decorative appearance. 4) Chromium platting is used to obtain wear resistant property and attractive appearance. 5) The kitchen utensils ,Equipments, tin cases, food containers are electroplated to keep them

free from acidic effect. 6) The electroplating is also used to increase soldering possibility. 7) Gold Plating is used for electric contacts and surfaces of reflectors. 8) Solver plating is used to decorate jwellery,cutlery,musical,surgical and electronics

instruments.

(c) Define powder metallurgy and explain basic concept and application of powder metallurgy 07

ANSWER:

Powder Metallurgy is the process of manufacturing the component using the powder of the metal and alloy.Non metallic element are also added in the powder based on the property requirement of the product.

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• Chart shows the basic process steps to be followed to manufacture a product by powder metallurgy process.

• Pre sintering is an optional operation. It is performed to impart machinability to the competed powder metallurgy parts. Once the parts are sintered ,it becomes very difficult to machine the same.So,if machining is required in producing a part,pre sintering is done prior to machining and after doing required machining on the part final sintering is performed.

• Secondary operation are mainly done to finish the parts. Depending upon dimensional and functional requirement of the product, secondary operations can be machining,rolling,heat treatment, surface coating,impregnation,etc.

Application

• To produce refractory parts of tungsten,Tantalum,Molybdenum which are used in the electrical bulb, radio valves ray tube filaments,cathod,anode and control grids e.g. WC.

• To produce refractory carbide, which are difficult to machine e.g. WC

• Automobile applications, electrical contracts,Cranckshaft drive, camshaft sprockets, piston rings, brake lining by PM root.

• To produce self lubricating bearings and filters.

• To produce intricate gears which needs more machining if produced by conventional method.

• Components of two metals and non metals like non porous bearings, electric motor brush are produced by powder metallurgy.

• Aerospace application:rocket,missile,satellite,space vehicle parts,e.g Be,Al,Zr powders are used in Solid fuel rocket.

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• Atomic Energy application are Be as fuel canning material, powder control rod,Rediation reflector,Zr and alloy as cladding material.

• Grinding Wheels containing steel & diamond powders are produced by powder metallurgy.

• Various parts of watches, type writter.calculator,Clutch&brake by P/M root.

Q.5 (a) State the properties of solid solution. 04

ANSWER:

Properties Of Solid Solution • Thermal &Electrical properties are reduced due to formation of solid solution. • The strength and hardness of all the alloy metals increases due to solid solution

• Solid solution reduces the ductility &malleability of the alloys.

• The density, specific heat &heat distribution get changed according to the proportions of alloying elements.

• By changing the proportion of the alloying element, there is no possibility to change the stiffness any more.

• Solid solution alloys exhibit differential freezing.

• Solid solution are conductors but not as the pure metals on which they are based.

• The Constituents of the solid solution cannot be detected by the microscope.

• It is simply a solution in the solid state consisting of atoms combined in one type of space lattice.

(b) Describe hardening and tempering process. 04

ANSWER:

Tempering

• It is Process of heating previously hardened steel to temperature below the lower critical temperature (A1) and cooling back to room temperature.

PROCESS

• Tempering Temperature for a hardened steel can vary from 100 to 680 °C depending upon the requirements. Low alloy constituents steels are tempered above 400°Cto get good combination of strength and ductility. Spring steels are tempered between 300 to 400°C.Folowing guideline are generally adopted for deciding tempering temperature.

1.Low temperature is used for carbon and alloy cutting tools and measuring tools, They are also carburized and surfaced hardened.

2.Medium Temperature is used to increase elongation and ductility by reducing hardness and strength.

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3.High temperature is used to maintain the ration of strength and ductility of structural steel.

Effects Of Tempering

• Relief Of Internal Stress.

• Formation Of Stable Phases.

• Increase In Toughness.

• Decrease in Hardness.

• Provide Right structural Condition Combined with toughness and Shock Resistance.

Hardening:

• It is a process for hardening a ferrous materials in such a manner that the surface layer is substantially harder than the remaining material.

• This is achieved by having different chemical composition and structure at the surface and at the core. For that following two methods are in use.

1) Hardening is the surface by changing phases and micro constituents of the material without changing the chemical composition at the surface. This is called surface hardening.

2) Hardening the surface by changing the chemical composition at the surface .This is called case hardening.

TYPES OF SURFACE HARDENING

SURFACE

HARDENING

CASE HARDENING

INDUCTION HARDENING FLAME HARDENING CARBURIZING NITRIDING

CYNIDING

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(c) State properties and application of following material. (1) Muntz metal (2) gun metal. 03

ANSWER:

MUNTZ METAL GUN METAL This alloy is known as Muntz Metal,Cu 60%,Zn 40%.

This alloy contains 2 to 5%Zn ,5 to 10%Sn and remaining Cu.

Possesses good properties to work with hot working properties.

It is resistant to corrosion & have good strength.

It is used for sheet castings and stamping production.

It is used for producing bearing,stamping,marine components, hydraulic valve & gears.

(d) State compotation and application of following material. (1) Bell metal (2) Babbitt metal. 03

ANSWER:

BELL METAL BABBITT METAL It is having 20%Sn and remaining Cu. It is having less than 10% Sn. This alloy is hard therefore wear resistant. Lead alloys with Tin and Aluminium makes

bearing metals like babbits. The bell of bell metals are used in church,schools,and hospitals.

It is used to produce shots of ammunitions.

Lead alloyed with antimony ,tin, copper makes this type of metal.

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