CHAPTER 2 :

FERROUS MATERIAL

STRUCTURE AND

BINARY ALLOY SYSTEM

JF302 MATERIAL TECHNOLOGY 1

PREPARED BY : ZUREENA BINTI ABU SAMAH

EDITED BY : MDM TAJ NESHA BEGAM BT BAISUL KHAN

SUMMARY • This topic introduces the methods of irons,

steels and cast irons production. It also describes the structure, properties and the usage of irons, steels and cast irons in the engineering field.

• CLO 1. explain various types of materials used in manufacturing industry. (Cognitive Domain : C2 Comprehension )

SYLLABUS : FERROUS MATERIAL STRUCTURE AND BINARY ALLOY SYSTEM

2.1 Understand the metal production

2.1.1 State the content of iron ore a. Magnetite

b. Iron carbonate

c. Hematite

d. Limonite

2.1.2 Explain the process of iron production by using Blast Furnace

2.2 Understand the steel production

2.2.1 Explain the process of steel production by using these

methods a. Basic Oxygen Furnace (BOP)

b. Electric Arc Furnace

2.3 Describe the plain carbon steel

2.3.1 Sketch completely the different phases in equilibrium phase diagram up to 1.7% carbon

2.3.2 Differentiate between iron, steel and cast iron in the iron-carbon equilibrium phase diagram

2.4 Describe the alloy steel

2.4.1 Define term and purpose of alloy steel

2.4.2 Explain elements in the alloy which influence steel properties.

2.4.3 Identify the characteristic of alloy steel a. Structure steel

b. Corrosion resistant steel

c. Heat resistant steel

d. Tool and mould steel

e. Magnetic steel

2.5 Describe the cast iron

2.5.1 Explain position of cast iron in iron-carbon phase diagram

2.5.2 Explain of cast iron properties effect a. Cooling rate

b. Carbon content

c. Cross sectional area

d. Element content

2.5.3 Explain the characteristics and applications of the cast iron

a. Grey cast iron b. White cast iron c. Black malleable cast iron d. White malleable cast iron e. Nodular cast iron

• Understand metal production – iron and steel

• Understand the process of iron and steel production

• Understand plain carbon

• Understand alloy steel

• Understand cast iron

LEARNING OUTLINE

IRON STEEL CAST IRON

TOPIC

Iron (fe)

• Iron is an element and can be pure. • Iron can be extracted from iron ores such as rocks,

mineral. • Classification of iron ores:-

– Magnetite – Iron Carbonate – Hematite – Limonite

• Iron is obtained by reducing iron oxides into metallic in blast furnaces.

• Basic constituent of steel.

• Iron ores are rocks and minerals from which metallic iron can be economically extracted.

• The ores are usually rich in iron oxides and vary in colour from dark grey, bright yellow, deep purple, to rusty red.

• The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite, limonite or siderite.

• Iron ore is the raw material used to make molten iron, which is one of the main raw materials to make steel.

What is iron ore?

2.2 Iron Ores Characteristics 1. GRADE – containing as much as possible iron oxide 2. COMPACTABILITY – not too compact or too brittle 3. PURITY – containing as less as possible impurities 4. SIMILARITY – containing similar composition to one another

Hematite Limonite Magnetite Iron Ore

Iron Ore Mining

• Chemical Formula is (Fe3O4).

• Also called as Black Iron Ore - because the color is black.

• Percentage of Iron; 72 – 62% Fe (Iron)

Magnetite

• Also know as siderite

• Chemical formula (FeCO3)

• Its color is yellowish green

• Percentage of iron; 35 – 40% Fe (Iron)

Iron carbonate

• Chemical formula (Fe2O3)

• Also known as Red Iron Ore.

• Percentage of Iron; 70% Fe (Iron).

HEmatite

• Chemical formula is (FeO(OH).n(H2O))

• Also known as Brown Iron Ore

limonite

Flowchart of iron process

Iron ore

Coal

Sintered iron ore

Coke

limestone Cal

led

as

Ch

arge

• The purpose of use blast furnace is to reduce and convert iron oxides into liquid iron called molten iron.

• The appearance of blast furnace is huge, steel stack lined with refractory brick.

• The blast furnace is around 30 metres high and lined with fireproof bricks.

• Iron ores, coke and limestone are put into the top and preheated air blown into the bottom.

• Iron can be extracted by blast furnace because it can be displaced by carbon.

• It more efficient and more cost effective.

Blast furnace

2.3 Iron Production Process Blast Furnace

Iron Ore is smelted in the Blast Furnace in order to remove unwanted impurities such as rocks, clay and sand, and also to separate the Iron from the Oxygen. The result is Iron which is about 95% pure. The remaining impurities are other elements which can be removed later if necessary. A Blast Furnace is about 100ft. high and produces abut 1000 tons of molten Iron a day. It is made from steel.

Structure of Blast furnace

• To ensure the process of extraction there are combined mixture of substances needed and called as charge.

• Charge: – Iron ore, hematite - often contains sand with iron oxide, Fe2O3. – Limestone (calcium carbonate). – Coke - mainly carbon

• The charge is placed a giant chimney called a blast furnace.

• The hot air that was blown into the bottom of the furnace ascends to the top in 6 to 8 seconds after going through numerous chemical reactions.

• Once a blast furnace is started it will continuously run for four to ten years with only short stops to perform planned maintenance.

The process of blast furnace

• The principal process take place in blast furnace as follow:- 1) Evaporation of moisture

2) Evolution volatiles

3) Decomposition of carbonates

4) Reduction of oxides into metallic iron and other elements

5) Carburization of iron and formation of molten iron

6) Slag formation

7) Combustion of fuel

The principal process of blast furnace

Oxygen in the air reacts with coke to give carbon dioxide:

– C(s) + O 2(g) CO2(g)

The limestone breaks down to form carbon dioxide:

– CaCO3(s) CO2 (g) + CaO(s)

– Carbon dioxide produced in 1 + 2 react with more coke to produce carbon

monoxide: • CO2(g) + C(s) 2CO(g)

– The carbon monoxide reduces the iron in the ore to give molten iron:

• 3CO(g) + Fe2O3(s) 2Fe(l) + 3CO2(g)

– The limestone from 2, reacts with the sand to form slag (calcium silicate):

CaO(s) + SiO(s) CaSiO3(l)

Reaction of iron production

Both the slag and iron are drained from the bottom of the furnace.

• The slag is mainly used to build roads.

• The iron whilst molten is poured into moulds and left to solidify - this is called cast iron and is used to make railings and storage tanks.

• The rest of the iron is used to make steel.

Reaction of iron production

Chapter 2:Ferrous Metals 2.0 Iron Productions 1. Iron ores are main material in iron ingot production. 2. In mining process, the iron ore are in pure state. It also found along with other substances such as oxide, sulphade, sulphur, silicon, etc.

STEEL

Steel is an alloy of iron, containing up to 2% of carbon (usually up to 1%).

It’s a combination of iron & carbon( 0.01 – 1%)

Contains varying amounts of manganese, phosphorus, sulfur, silicon & 20 other alloys

Alloys added to produce steel of different characteristics.

To produce useful steel, molten iron need to be oxidized in another furnace at about 1650°C.

Molten iron is not useful because it’s weak and brittle although it’s very hard.

STEEL

FLOWCHART OF IRON AND STEELMAKING PROCESS

FLOWCHART OF IRON AND STEELMAKING PROCESS

Molten iron casting Produces molten iron from iron ore

Flowchart of iron and steelmaking process

Molten iron

• The main steel making methods are:

1) Basic Oxygen Process (BOP)

2) Electric-arc furnace

Steel production method

• Typical basic oxygen furnace has a vertical vessel lined with refractory lining.

• Only 8-12% of the furnace volume is filled with the treated molten metal

• The vessel consists of three parts: spherical bottom, cylindrical shell and upper cone.

• The vessel is attached to a supporting ring equipped with trunnions.

• The supporting ring provides stable position of the vessel during oxygen blowing.

• The converter is capable to rotate about its horizontal axis on trunnions driven by electric motors.

• This rotation (tilting) is necessary for charging raw materials, sampling the melt and pouring the steel out of the converter.

Basic oxygen furnace (BOF)

Basic Oxygen Furnace

Flowchart of BOF process

Figure - BOF sequence : (1) charging of scrap and (2) molten iron, (3) blowing, (4) tapping the molten steel, (5) pouring off the slag

BOF Process

a) Charging scrap – the scrap is first to be charged

b) Pour molten iron – pouring molten iron from blast furnace

c) Blowing – starting blowing oxygen and the duration time of blowing about 20

min.

d) Discharging steel – Pouring the steel to a ladle. Special devices (plugs, slag detectors)

prevent penetration (carry-over) of the slag into the ladle

e) Discharging slag – De-slagging - pouring the residual slag into the slag pot. The furnace is

turned upside down in the direction opposite to the tapping hole.

Electric Arc Furnace (EAF)

• The electric arc furnace is used to reduce iron from iron ore.

• Heat is generated from an electric arc between electrodes.

• Oxygen is blown into the furnace, and lime and other materials are added to combine with the impurities and form slag.

• Molten iron is extracted and poured out via a tapping spout. It is then processed again in an electric arc furnace to make steel – particularly special quality steel.

EAF Process

• Carbon is the principal alloying element, with only small amounts of other elements (about 0.5% manganese is normal)

• Strength of plain carbon steels increases with carbon content, but ductility is reduced

• High carbon steels can be heat treated to form martensite, making the steel very hard and strong

• Plain Carbon Steels Grouped by Carbon Content 1. Low carbon steels - contain less than 0.20% C

– − Applications: automobile sheetmetal parts, plate steel for fabrication, railroad rails

2. Medium carbon steels - range between 0.20% and 0.50% C – − Applications: machinery components and engine parts such as crankshafts

and connecting rods

3. High carbon steels - contain carbon in amounts greater than 0.50% – − Applications: springs

Plain Carbon Steels

The Allotrophy Of Iron

Iron can exist in more than

one form.

• Up to 910 degrees, alpha iron is in BCC form.

• Between 910 and 1390 degrees, gamma iron exists in FCC form.

• Above 1390 degrees, delta iron returns to BCC form.

Iron Carbon Equilibrium Diagram

Steel part of the Iron Carbon Equilibrium Diagram

• Eutectoid point is a solid to solid change point where solid Austenite changes into solid Pearlite.

Microstructures on steel part of the Iron Carbon Equilibrium Diagram

Iron – carbon system

• Eutectoid Steel

– (0.8 %C)

• Hypo-eutectoid steel

– (< 0.8 %C)

• • Hyper-eutectoid steel

– (0.8% < %C ≤ 2.0%)

Steel (%Carbon ≤ 2.0%)

• Hypo-eutectic cast iron

– (2.0% < %C < 4.3%)

• Hyper-eutectic cast iron

– (4.3% < %C < 6.67%)

Cast Iron (%Carbon > 2.0%)

• Alloy steels are iron-carbon alloys, to which alloying elements are added with a purpose to improve the steels properties as compared to the carbon steels.

• Alloy steels contain alloying elements (e.g. manganese, silicon, nickel, titanium, copper, chromium and aluminum) in varying proportions in order to manipulate the steel's properties, such as its hardenability, corrosion resistance, strength, formability, weldability or ductility.

• Applications for alloys steel include pipelines, auto parts, transformers, power generators and electric motors.

• Contain more than 1.0% of other elements instead of Fe and C. • Purpose of alloying

– Increase hardenability – Improve strength at ordinary temperature – Improve mechanical properties at either high or low temperatures – Improve toughness at any minimum hardness or strength – Increase wear resistance – Increase corrosion resistance – Improve magnetic properties

Alloy steels

Manganese (Mn) • Improves hardenability, ductility and wear resistance.

• Mn eliminates formation of harmful iron sulfides, increasing strength at high temperatures.

Nickel (Ni) • Increases strength, impact strength and toughness,

impart corrosion resistance in combination with other elements.

Chromium (Cr) • Improves hardenability, strength and wear resistance,

sharply increases corrosion resistance at high concentrations (> 12%).

Silicon (Si) • Improves strength, elasticity, acid resistance and

promotes large grain sizes, which cause increasing magnetic permeability.

Copper (Cu) • Improves corrosion resistance.

Influence Of Alloying Elements For Steel

• Structure steels contain carbon and a higher amount of alloying elements such as nickel, chromium, manganese, cobalt, niobium and vanadium.

• These elements are added to improve mechanical properties, ductility and other steel service properties.

Characteristic of structure steel

• Tool and mould steels contain

tungsten, molybdenum, cobalt and vanadium

• Characteristics include high hardness, resistance to abrasion (excellent wear), an ability to hold a cutting edge, resistance to deformation at elevated temperatures (red-hardness).

• Tool steel are generally used in a heat-treated state.

• High carbon content – very brittle

Characteristic of tool & mould steel

• Also known as stainless steel

• Contain between chromium as the main alloying element

• Corrosion resistant for a specified application or environment.

Characteristic of corrosion steel

• There are 3 magnetic elements

– 1. Iron

– 2. Nickel

– 3. Colbolt

• Ability of a material to carry magnetism

• Application - solenoid shafts

Characteristic of magnetic steel

• The combination of chromium (giving the steel excellent corrosion resistance) and Molybdenum (for greater tensile strength and heat resistance).

• Industrial applications include furnaces, heat exchanges and incinerators where temperatures can reach in excess of 1100°C.

Characteristic of heat resistant steel

• Cast iron = an iron-carbon alloy containing from 2.1% to about 4% or 5% carbon

• Cast iron is an important alloy of Fe and C are largely used in industry for its convenience to casting in intricate and good mechanical properties.

• Classification of Cast Irons – The best method of classifying cast iron is according to

metallographic structure. – There are four variables as under to be considered which lead to

the different types of cast irons. • Carbon content • The alloy and impurity content (silicon & carbon) • The cooling rate during and after freezing • The heat treatment after casting.

Cast iron (CI)

• Cheap material. • Lower melting point (1200oC) as compared to steel (1380-

1500oC). • Good casting properties, e.g. high fluidity, low shrinkage,

sound casting, ease of production in large number. • CI is machinable is most cases. • Good in compression but CI with ductility are also available. • Abrasion resistance is remarkably high. • Very important property of CI is its damping characteristics

which isolates vibration and makes it good material for foundation and housing.

• Alloy CI may be good against corrosion.

Properties of cast iron

cast iron in iron-carbon phase diagram

Cooling rate and type of cast iron

Composition and type of cast iron

Classification of cast iron

• The cross-section show the greyish colour, hence the name grey cast iron

• Properties:-

– Good machinibility

– High compressive strength

– Low tensile strength

– No ductility

• Application:-

– Used in foundry work

Grey cast iron

• Shows a “white” crystalline

• Properties:- – Excellent wear resistance

– High compressive stress

– Hard, brittle

• Application:- – Railway wheel brake

– Hammer mills

– Crushing rollers

WHITE CAST IRON

• Malleable cast iron is produced by giving long time heat treatment (annealing) to white cast iron casting.

• The two common types of malleable cast iron are:- 1) Black malleable cast iron

• Produced when white cast iron castings are packed in an oxidizing material to remove some carbon

2) White malleable cast iron • Produced when white cast iron castings are packed in some inert

material (such as ferrous silicate scale or slag) and annealed.

• Result – the casting consists almost entirely graphite and ferrite.

Malleable cast iron

• Properties:-

– Harder and stronger

– Less ductile

– Less impact resistance

• Application:-

– For hardware item, pipe

– Pipe fitting

– Automobile part

White Malleable cast iron

• Properties:-

– Machinability improved

– Higher impact resistance

• Application:-

– Automobile

– Tractor part

– Bush bearing

– Gear wheels

– Spanner

Black Malleable cast iron

• Also known as “spheroidal graphite”

• Obtained by adding magnesium to the molten cast iron

• Properties:- – Strength high – Yield point improves – Brittleness reduces

• Application:- – Hydraulic cylinder – Valves – Pipe – Diesel engines

Nodular/ductile cast iron