Lecture 03_Ferrous Metal & Alloys

7/30/2019 Lecture 03_Ferrous Metal & Alloys

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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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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.


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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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.



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Limestone (CaCo3 & MgCO3)

[after cleaning]

Limestones storage area



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Limestone mine



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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)

http://www.geokem.com/images/scans/Nikolai-Geologist.jpghttp://www.geokem.com/images/scans/Indonesian_coal_mine.jpg


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IRON MAKING


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- 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


Slag


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Slag poured

into ladles

The slags storage area


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ELECTRIC FURNACES

1) Direct Arc


- 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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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



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~ 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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The hot metal charge for basic-oxygen furnace


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- 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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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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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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- 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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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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~ 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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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.

Lecture 03_Ferrous Metal & Alloys

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