lecture 03_ferrous metal & alloys
TRANSCRIPT
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MANUFACTURING PROCESS(BMFG 2323)
LECTURE 3
FERROUS METALS AND ALLOYSJuffrizal KarjantoDesign and Innovation DepartmentFKM
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FERROUS METALS AND ALLOYS 1
- Due to the wide range in mechanical, physical, and chemical properties, ferrous metals
and alloys are among the most useful of all metals.
- Contains of iron as their base metal; general categories are carbon and alloy steels,
stainless steels, tool and die steels, cast irons, and cast steels.
Produced product:
Sheet steel for automobiles, appliances and containers.
Plates for boilers, ships, and bridges.
Structural members such as I-beams, bar products, crankshafts and railroad rails.
Tools, dies and molds.
Fasteners such as bolts and nuts.
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FERROUS METALS AND ALLOYS 2
IRON AND STEEL MAKING
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- The three basic materials used in iron and making steel are:1) Iron ore.
2) Limestone.
3) Coke.
FERROUS METALS AND ALLOYS 2
1) Iron Ore- After it is mined, the ore is crushed into small particles and the impurities are removed
by using the magnetic separation techniques.
- The ore is formed into pellets by using water and various binders.
- Typically, this pellets contains 65% of pure iron and about 25mm in diameter.
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FERROUS METALS AND ALLOYS 3
Iron ore
(after cleaning)
Iron ore
storage area
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2) Limestone- Function: to remove impurities from molten iron.
- It reacts chemically with impurities, acting like a flux which causes the impurities to
melt at low temperature.
- It also combines with the impurities to form a slag, where this slag will float over the
molten metal.
FERROUS METALS AND ALLOYS 3
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Limestone (CaCo3 & MgCO3)
[after cleaning]
Limestones storage area
FERROUS METALS AND ALLOYS 4
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Limestone mine
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FERROUS METALS AND ALLOYS 5
3) Coke
- Coke is obtained from special grades of bituminous coal, that are heated in
vertical coke oven to temperatures of up to 11500C and then cooled with water
in quenching towers.
- Functions:
i) Generate high level of heat required for the chemical reactions in iron making.
ii)Producing CO (removes the O2), which is then used to reduce iron oxide to iron.
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Coal mine Coal(after cleaning)
FERROUS METALS AND ALLOYS 9
http://www.geokem.com/images/scans/Nikolai-Geologist.jpghttp://www.geokem.com/images/scans/Indonesian_coal_mine.jpg -
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FERROUS METALS AND ALLOYS 6
IRON MAKING
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FERROUS METALS AND ALLOYS 6
- All three basic materialscarried to the top of the blast furnace and dumped right
to the bottom section of the furnace.
- Basically, the furnace is a large steel cylinder lined with refractory heat-resistance brick.
- The height of the furnace can goes up to 10 story building.
- The charge mixture is melted in reaction at 16500C together with air which pre-heated
about 11000C, blasted into the furnace through nozzles called tuyeres.
- The basic reaction: between O2 and C to produce CO which then reacts with the iron oxideand reduces it to iron.
- Preheating the incoming air is necessary because the burning coke alone does not produce
sufficiently high temperatures for these reactions to occur.
- In the blast furnace, the molten metal accumulates at the bottom of the furnace while
the impurities float on top of the molten metal.
- Slag has many commercial use, and is rarely thrown away.
- It often reprocessed to separate any other impurities that may contain.
- Slag is used in making cement, fertilizers, building materials and road ballast.
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Steel worker at blast furnace tap
FERROUS METALS AND ALLOYS 7
Slag
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FERROUS METALS AND ALLOYS 8
Slag poured
into ladles
The slags storage area
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ELECTRIC FURNACES
1) Direct Arc
FERROUS METALS AND ALLOYS 3
- Source of heat in this furnace is a continuous
electric arc which formed between the three
graphite electrodes (750mm in dia. and 1.5m to
2.5m in length) and the charged metal.
- Temperature: 19250C.
- Steel scrap, carbon and limestone are dropped
into the electric furnace thru the open roof.
- The roof then is closed and the electrodes are
lowered turned on the power, and within 2H,
the metal melts.
- Next, the current is shut off, the electrodes are raised, the
furnace is tilted, and the molten metal is poured into a ladle.
- The capacities can range: 55 to 82 tones of steel per day.
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FERROUS METALS AND ALLOYS 4
2) Indirect Arc
INDIRECT ARC TYPE
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3) Induction
- Used for small amount of quantities.
- The metal is placed inside a large pot (made
from refractory material and surrounded with
copper coils)
- The alternating current is passed thru this
copper coilsform heat and melt the metals.
- This type of electric furnace are also used
for remelting metal for casting.
INDUCTION TYPE
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Scrap charges
or
Electric furnace
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Electric furnace
Continuous
casting
FERROUS METALS AND ALLOYS 5
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FERROUS METALS AND ALLOYS 6
~ BASIC OXYGEN FURNACE ~
- The most fastest steel making
process.
- 180 tones of pig iron + 82 tones
of scrap are charged into a vessel;
fluxing agent (lime) are also added.
- Pure O2 is blown into the furnace
for about 20 min. thru a lance,
under a pressure of 1250kPa.
- Iron oxide is produced due to an
oxidation process.- The oxide react with the carbon in
the molten metal, producing CO +
CO2.
- The lance is then retracted, and the furnace is tapped by tilting itthe slag is removed by
tilting the furnace at the opposite direction.
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FERROUS METALS AND ALLOYS 6
The hot metal charge for basic-oxygen furnace
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FERROUS METALS AND ALLOYS 6
- There are 3 types of steel ingots depending on the amount of gases evolved duringsolidification.
Steel ingots
Rimmed
Semi-killed
Killed
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FERROUS METALS AND ALLOYS 6
1) KILLED STEEL
- Fully deoxidized steeltherefore, eliminated the porosity.
- In the process of deoxidization, the dissolved O2 in the molten metal will react with
elements such as aluminum, silicon, manganese, as well as vanadium to form a metallicoxides, eg: aluminum killed steel.
- Free from any porosity, free of any blowholes, and relatively the mechanical and
chemical properties of an ingots are uniform due to the shrinkage during solidification.
- Produce pipe on top of the ingots (shrinkage cavity).
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2) SEMI-KILLED STEEL- Partially deoxidizedcontains some porosity (occurred at the upper central section
of the ingot.
- Little or no pipe.
3) RIMMED STEEL- Has low amount of C (< 0.15%).
- The evolved gas are controlled partially by the addition of other element such as
aluminum.
- The gases produce blowholes along the outer rim of the ingots.- Little or no pipe.
- Ductile skin with good surface finish.
- If not properly controlledblowholes may break through the skin and the impurities
tend to segregate toward the center of the ingot.
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FERROUS METALS AND ALLOYS 7
CONTINUOUS CASTING
(STRAND CASTING)- Can produce higher quality steels at reduced cost.
- The molten metal in the ladle is cleaned, and then
equalized in temperature by blowing the nitrogen
gas thru it (5 to 10 minutes).
- The molten metal then is poured into a reservoir(tundishcan holds up to 3 tons of metal).
- The molten metal travels downwards thru
water-cooled copper molds and start to solidify.
- Before starting with the casting process, a solid
starter bar, is inserted at the bottom portion ofthe mold.
- The cooling rate develops a solidified skin
(12 to 18mm of thickness).
- Purpose, to support the metal itself during travel
downwards at speed 25 mm/s.
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FERROUS METALS AND ALLOYS 6
- Additional cooling is provided with water sprays along the travel path of the solidifying
metal.
- The moldsare coated with graphite or solid lubricantsto reduce the friction and
adhesion at the mold-metal interfaces.
- The molds are also vibrated to reduce friction and sticking.
- The continuous cast metal can be cut into desired lengthby using techniques of shearing
or computer-controlled torch cutting.
- Sometimes it can be straight away fed into rolling mill for further reduction of the thickness
as well as for the shaping purposes such as channel or I-beams.
- Next, these steel plates will undergo few other processes such as:
a) cleaning by chemicals to remove the surface oxides.
b) cold rolling to improve strength and surface finish.
c) annealing.
d) coating (galvanizing or aluminizing) to improve resistance to corrosion.
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FERROUS METALS AND ALLOYS 6
REFINING- A process of eliminating or separating the impurities, residuals from the melting metal.
- The eliminating process occurs in melting furnace or ladles.
- Create a uniform properties and a greater consistency of compositionproduce high-grade
steels and alloys for high performance and critical applications.
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FERROUS METALS AND ALLOYS 6
~ CARBON AND ALLOY STEELS ~
TABLE 5.1
Product Steel Product Steel
Aircraft forgings,
tubing, fittings
Automobile bodies
Axles
Ball bearings and races
Bolts
Camshafts
Chains (transmission)Coil springs
Connecting rods
Crankshafts (forged)
4140, 8740
1010
1040, 4140
52100
1035, 4042, 4815
1020, 1040
3135, 31404063
1040, 3141, 4340
1045, 1145, 3135, 3140
Differential gears
Gears (car and truck)
Landing gear
Lock washers
Nuts
Railroad rails and wheels
Springs (coil)
Springs (leaf)Tubing
Wire
Wire (music)
4023
4027, 4032
4140, 4340, 8740
1060
3130
1080
1095, 4063, 6150
1085, 4063, 9260, 61501040
1045, 1055
1085
- The most commonly used metals and have a wide variety of applications.
- Available in various basic product shapes such as plate, sheet, strip, bar, wire, tube,
castings and forgings.
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EFFECTS OF VARIOUS ELEMENTS IN STEELS
- Various elements are added to steels in order to impart the properties of materials:
harden, strength, toughness, wear resistance, weldability, machinability.
- Generally the higher the percentage of the elements in the steels, the greater theproperties that impart; eg: the higher the C content, the greater the hardenability of
the steels, as well as greater in strength, hardness, and wear resistance. On the other
hand, the higher the C content, there are a reduction of ductility, weldability, and
toughness.
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CARBON STEELS- Generally are classified by their proportion (by weight) of carbon content.
- Can be divided into three types:
i) Low-carbon steel (mild steel).
- Has less than 0.30% C.
- Used for common industrial products and machine components;
eg: bolts, nuts, sheet, plate, and tubes).
- Do not require high strength.
ii) Medium-carbon steel.
- Has 0.30 to 0.60% C.
- Generally used in applications which requires higher strength than low-carbon
steel; eg: machinery, automotive, and agricultural equipments parts: (gears,
axles, connecting rods, crankshafts, railroad equipment, and parts for metal
working machinery.
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iii) High-carbon steel.
- Has more than 0.60% C.- Generally used for parts requiring strength, hardness, and wear resistance;
eg: cutting tools, cable, music wire, springs, and cutlery.
- The parts usually are heat treated and tempered after being manufactured
into shapes.
- Carbon steel containing sulfur and phosphorus which known as resulfurized carbon steels,
and rephosphorized carbon steels.
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ALLOY STEELS
- Steel containing significant amount of alloying element which called alloy steels.
- This type of steels can be heat treated to obtain the desired properties.
- Structural-grade alloy steels are used mainly in construction and transportation industries
due to their high strength.
- Other of alloy steels are used in applications where strength, hardness, creep and fatigue
resistance, and toughness are required.
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FERROUS METALS AND ALLOYS 6
HIGH-STRENGTH LOW ALLOY STEELS
- To improve the strength-to-weight ratio of steels, a number of high-strength low alloy
steels (HSLA) have been developed.
- These steels have a low carbon content (usually less than 0.30%).
- These type of steels are also characterized by a microstructure consisting of fine-grain
ferrite as one phase and martensite together with austenite as a second phase.- HSLA steels usually are produces in a form of sheet by microalloying and controlled
hot rolling.
- Other shapes: plates, bars, and structural shapes.
- The ductility, formability, and weldability of HSLA steels, however generally are inferior
to those of conventional low-alloy steels.
- Therefore, to improve the properties, a process which called dual-phase steels aredeveloped.
- Application: parts of automobile bodies, mining, agricultural; HSLA plates are widely
used in ships, bridges, building construction, and other shapes such as I-beams, channels,
and angles used in buildings.
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MICROALLOYED STEELS- One of the HSLA steels which recently developed.
- Have superior properties; can eliminate heat treatment, hence not required other
manufacturing process such as quenching, tempering, and stress relievingtherefore
this type of steels are much more cheaper compared to medium-carbon steels.
- Contains of ferrite-pearlite microstructure with fine dispersed particales of carbonite;
0.5% C, 0.8% Mn, and 0.1% V.
-With carefully controlled cooling (usually in air), these materials develop improved
uniform strength.
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STAINLESS STEELS
- Characteristics: corrosion resistance, high strength and ductility, and high chromium content.
- Other alloying elements in stainless steels: nickel, molybdenum, copper, titanium, silicon,
manganese, columbium, aluminum, nitrogen, and sulfur.
- This kind of steels have low carbon content, therefore the corrosion resistance is high.
- Produced by using electric furnaces or basic-oxygen process and the techniques are similar
to those used in steelmakingcan be in a form of variety of shapes.
- Application: cutlery, kitchen equipments, health care and surgical equipment, chemical,
food-processing, and petroleum industries.
- Generally can be divided into five types:
i) Austenitic (200 and 300 series).
ii) Ferritic (400 series).
iii) Martensitic (400 and 500 series).
iv) Precipitation-hardening (PH).
v) Duplex structure.
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i) AUSTENITIC (200 AND 300 SERIES)
- Composed of chromium, nickel, and manganese in iron.
- Non-magnetic metal and excellent in corrosion resistance, but susceptible to stress-corrosion
cracking.- Harden by cold working process; if increase the cold work will reduce the formability.
- The most ductile of all stainless steels and can be formed easily.
- Application: kitchenware, fittings, welded construction, lightweight transportation equipment,
furnace and heat exchanger parts, components for severe chemical environments.
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iv) PRECIPITATION-HARDENING (PH)
- Contain chromium and nickel, copper, aluminum, titanium, molybdenum.
- Good corrosion resistance and ductility and high strength at elevates temperatures.
- Application: aircraft and aerospace structural components.
v) DUPLEX STRUCTURE
- Mixture of austenite and ferrite.
- Good strength, higher resistance to corrosion (in most environments), higher stress
corrosion cracking if compared to austenitic steels 300 series.- Application: water treatment plants, heat exchanger components.
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TOOL AND DIE STEELS
- Special alloyed steels designed for high strength, impact toughness, and wear resistanceat room and elevated temperatures.
- Application: commonly used in forming and machining of metals.
HIGH SPEED STEELS (HSS)
- The most highly alloyed tool and die steels.
- Maintain their hardness and strength at elevated operating temperatures.
- Generally, there are two types of high-speed steels:
i) molybdenum type (M-series).
ii) tungsten type (T-series).
- The M-series steels contain up to about 10% molybdenum with chromium, vanadium,
tungsten, and cobalt as other alloying elements.- The T-series steels contain 12 to 18% tungsten with chromium, vanadium, and cobalt as
other alloying elements.
- The M-series steels have higher abrasion resistance, under go less distortion in heat
treatment, and less expensive compared to T-series steels.
- HSS tools can be coated with titanium nitride and titanium carbide for the enhancement
of wear resistance.
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DIE STEELS
HOT-WORK STEELS (H-SERIES)
- Designed for use at elevated temperatures.
- High toughness as well as high resistance to wear and cracking.
- Alloying elements are: tungsten, molybdenum, chromium, and vanadium.
COLD-WORKS STEELS (A, D, AND O-SERIES)
- Used for cold-working operations.
- High resistance to wear and cracking.
- Available as oil-hardening or air-hardening types.
SHOCK-RESISTING STEELS (S-SERIES)
- Designed for impact toughnesssuitable in the application as header dies, punches,
and chisels.