In this article, you will learn the complete overview of ferrous metal such as its definition, types, uses, properties, and many more.
In our previous article, we learned about the different types of metals and their uses.
Metal can be classified into three categories which are: Ferrous Metal, Non-Ferrous Metal, and Alloys.
Here we will discuss only about ferrous metals.
Ferrous metal is made up of iron and other metals to give the required properties.
Ferrous metals have a high carbon content.
In the case of ferrous metal, the base metal is iron.
So, without wasting time let's get started.
What is Ferrous Metal?
Those metals which have iron as constituents are known as ferrous metals.
Ferrous metals have a high carbon content which generally makes them vulnerable to rust when exposed to moisture.
Most ferrous metals are magnetic which makes them very useful for motor and electrical applications.
Properties of Ferrous Metal
Ferrous metals have some well-known properties:
- High tensile strength.
- Magnetic (Because of the presence of iron)
- Low resistance to corrosion.
- Good conductor of electricity.
- Good conductor of heat.
Types of Ferrous Metal
Ferrous metal can be classified into four types:
- Pig Iron
- Cast Iron
- Wrought Iron
- Steel
Show in the figure different types of ferrous metal which are described below in detail.
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| Types of Ferrous Metal |
Pig Iron
It is obtained by the chemical reduction of iron ore then this impure iron is sent to a blast furnace where it melts at around 1200°c after which iron is obtained from a blast furnace which is called pig iron.
Types of Pig Iron
Pig iron is divided into three categories according to the amount of carbon and the percentage of graphite in pig iron:
- Gray Pig Iron
- Mottled Pig Iron
- White Pig Iron
Gray Pig Iron
It contains 0.3% to 1% carbon and 3% graphite.
Its color is dark brown.
It is used for casting.
Mottled Pig Iron
It contains equal amounts of carbon and graphite.
Its color is brown and It is used for hard casting.
White Pig Iron
It contains 2% to 4% carbon and a very small amount of about 0.5 graphite.
Its color is somewhat white and it is used to make wrought iron.
Cast Iron
It is obtained by melting pig iron with coke and limestone in a cupola furnace.
Cast Iron contains 2% to 4% carbon, 0.8% to 3% sulfur, phosphorus from 1% to 1.5%, manganese from 0.5% to 1%, and 80% to 90% iron.
Due to its high carbon content, it is brittle and has low ductility.
It has good compressive strength but poor tensile and shear strength.
It is used for machine beds, pulleys, brackets, pipe fittings, cylinder blocks for IC engines, etc.
Types of Cast Iron
On the basis of composition, cast iron is mainly divided into five parts:
- Gray Cast Iron
- White Cast Iron
- Mottled Cast Iron
- Malleable Cast Iron
- Ductile Cast Iron
- Alloy Cast Iron
Gray Cast Iron
The freshly fractured surface is brown in color and is known as gray cast iron.
Gray cast iron contains 92% iron and 2% to 4% carbon.
Other elements are present in very small amounts.
Carbon is present in the form of graphite so due to the presence of free graphite in its composition, it acts as a lubricant.
Its melting point is around 1200°C.
Its machining can be done easily.
It is considered the most suitable variety for casting works.
It is relatively less expensive and hence is used for machine parts.
It has high compressive strength and low tensile strength.
It is used for making cylinders, frames of machines, pistons, flywheels, etc.
White Cast Iron
The freshly fractured surface is white in color, it is known as white cast iron.
White cast iron contains 94% iron, 3% carbon, and 0.5% graphite.
Due to the presence of carbon in carbide form, it is extremely hard, brittle, and wear-resistant.
It cannot be machined easily.
It is used as a raw material for malleable cast iron.
It is used mainly for wear and abrasion-resistant parts such as balls for ball mills, wear-resisting pads & liners, crushing rollers, etc.
It takes less rust and cannot be cut easily.
It makes parts that can be made without machining.
Mottled Cast Iron
Mottled cast iron is a mixture of gray cast iron and white cast iron.
It contains 93.5% iron, 1.75% carbon, and 1.75% graphite.
It is hard and brittle and rusts less in it.
Malleable Cast Iron
It is obtained by heating white cast iron at a high temperature of 1500 °C and then cooling it slowly by a special heat treatment process annealing.
Carbon is present in cementite form.
It contains less amount of carbon and more graphite, which because of this becomes soft.
Malleable cast iron as its name suggests so is malleably caused by hammering or pressure by a machine that can be converted into a sheet.
It has good machinability.
It is tougher than grey cast iron and more resistant to bending and twisting.
It is softer, and tough than other types of cast iron and is machinable.
It is used for making parts where dimensional accuracy is required such as automobile parts, gears, door hinges, hubs for wagon wheels, etc.
Ductile Cast Iron
It is obtained by adding a small amount of magnesium or calcium to molten iron.
This causes graphite in cast iron to form nodules or spheres so it is also known as nodular cast iron.
It is ductile.
It has good wear resistance and excellent machinability.
It is used for making crankshafts, gears, pipe and pipe fittings, cylinder heads, valves, etc.
Alloy Cast Iron
Alloy cast iron is prepared by adding other metals such as nickel, chromium, molybdenum, silicon, etc. to cast iron.
All the properties of alloy cast iron are better than normal cast iron.
Wrought Iron
Wrought iron is the purest form of iron.
It contains 99% pure iron and 0.25% carbon and other impurities.
Wrought iron is prepared by the puddling process.
It is a soft and pure type of iron, which is made into sheets when beaten, wires when drawn, rods, rail couplings, crane hooks, etc.
Steel
Steel is mainly a mixture of iron and carbon.
Steel is composed of iron and carbon. The carbon content in steel can range from 0.1-1.5%, but the most widely used grades of steel contain only 0.1-0.25% carbon.
To get some special properties, other metals are also added to it.
Elements such as manganese, phosphorus, and sulfur are found in all grades of steel, but, whereas manganese provides beneficial effects, phosphorus and sulfur are deleterious to steel's strength and durability.
Types of Steel
Steel is mainly divided into the following parts:
- Carbon Steel
- Alloy Steel
Carbon Steel
The steel whose main components are iron and carbon is called carbon steel.
It is also called plain steel.
Carbon steel is probably used for at least 80% of all components in refineries and petrochemical plants because it is inexpensive, readily available, and easily fabricated.
According to the percentage of carbon in iron, carbon steel is divided into three parts:
- Low Carbon Steel
- Medium Carbon Steel
- High Carbon Steel
Low Carbon Steel
The amount of carbon in low-carbon steel ranges from 0.15% to 0.25%.
It is also called mild steel.
Due to the low carbon content, it is soft.
Parts made from it cannot be hard and tempered but they can hard case.
It is used for making nuts, bolts, sheets, wires, machine parts, rods, etc.
Medium Carbon Steel
The amount of carbon in medium carbon steel ranges from 0.25% to 0.6%.
It is harder and tougher than mild steel, and its tensile strength is also high.
Its hardening and tempering can be done.
It is used to make gears, agricultural implements, shafts, spindles, camshafts, spanners, connecting rods, etc.
High Carbon Steel
The carbon content in high-carbon steel ranges from 0.6% to 1.5%.
It is very hard, due to which it wears less.
It can be hardened.
It is used in making sharp tools, dies, punches, files, chisels, and other cutting tools.
Alloy Steel
The steel in which some special properties are obtained by adding other metals like nickel, chromium, vanadium, manganese, molybdenum, tungsten, etc is called alloy steel.
Types of Alloy Steel
Alloy steel can be divided into the following types:
- High-Speed Steel
- Nickel Steel
- Nickel Cobalt Steel
- Nickel Chromium Steel
- Vanadium Steel
- Manganese Steel
- Silicon Steel
- Cobalt Steel
- Molybdenum Steel
- Stainless Steel
High-Speed Steel
High-speed steel is made by adding tungsten to steel, hence it is also known as tungsten steel.
Tungsten steel is very hard and maintains its hardness even at high temperatures.
It is used in making cutting tools, drill bits, hex blades, cutters, reamers, etc.
According to the amount of tungsten, it is of three types:
- Super High-Speed Steel
- Medium-High Speed Steel
- Low High-Speed Steel
Super High-Speed Steel
It contains 22% tungsten, chromium 4%, and vanadium up to 1%.
Medium-High Speed Steel
It contains tungsten 18%, chromium 4%, and vanadium 1%.
Low High-Speed Steel
It contains tungsten 14%, chromium 4%, and vanadium 1%.
Nickel Steel
It contains up to 4% nickel metal.
Its hardness, elastic limit, and tensile strength are high and it does not rust easily.
It is used in making rivets, pipes, axles, and parts of aircraft and engines.
Nickel Cobalt Steel
If 30% to 35% nickel and 5% cobalt are added to the steel, it is called nickel-cobalt steel.
It is also called Invar steel.
Its coefficient of expansion is very less that's why it is used as a precision instrument.
Nickel Chrome Steel
The steel in which 0.5% to 1% carbon, 0.3% to 0.8% manganese, 3% to 5% nickel, and 0.5% to 1.8% chromium are mixed is called nickel chrome steel.
This increases the elastic limit, reduces wear, and also increases hardness and tensile strength.
It is used in making cutlery, automobile parts, cutting tools, etc.
Vanadium Steel
The steel in which 1.5% carbon, 12.5% tungsten, 4.5% chromium, 5% cobalt, and 5% vanadium is added is called vanadium steel.
Due to this, its elastic limit and tensile strength increase, and the ability to tolerate strong shocks arise.
It is mostly used for making tools and cutters.
Manganese Steel
The steel in which 1.0% to 1.9% manganese, and 0.4% to 0.8% carbon are mixed is called manganese steel.
It is also called special high alloy steel.
It wears less.
It is used in making rail lines, grinders, etc.
Silicon Steel
Silicon is mixed in this steel in varying amounts from 1% to 14% according to the work.
It is heat resistant.
It does not rust.
Cobalt Steel
The steel which contains 0.5% to 1.5% high carbon and 5% to 35% cobalt is called cobalt steel.
It has more toughness, tensile strength, and magnetic properties, so it is mostly used for making permanent magnets and more sharp tools.
Molybdenum Steel
The amount of molybdenum in it is very heavy.
It contains molybdenum 4.5% to 9%, carbon 0.8 to 1.5%, chromium 4%, and vanadium 1 to 5%.
On mixing these metals in it, a lot of hardness and toughness come.
It is used to make bearings, motor vehicles, airplanes, etc.
Stainless Steel
If nickel 8%, chromium 18%, molybdenum 2%, and carbon 0.2 to 0.6% are mixed in steel, then it is called stainless steel.
Stainless steels generally contain more than 10% chromium as the main alloying element and are valued for high corrosion resistance. It does not stain, corrode or rust as easily as ordinary steel that's why it is called stainless steel.
Stainless steels have a sufficient amount of chromium present so that a passive film of chromium oxide forms which adheres to the metal surface very tightly and prevents further corrosion.
It is very hard, tough, acid-resistant, and corrosion-resistant.
It does not rust.
It cannot be hardened.
It is often used to make household utensils, watch parts, automobile parts, cars, knives, and airplanes.
These steels can be divided into three groups based on their crystalline structure:
- Austenitic Stainless Steel
- Ferritic Stainless Steel
- Martensitic Stainless Steel
Austenitic Stainless Steel
It contains 18-26% chromium (Cr) and 8-22% nickel (Ni) and less than 0.8% carbon.
It is non-magnetic and non-heat-treatable.
Ferritic Stainless Steel
It contains trace amounts of nickel, 12-17% chromium, and less than 0.2% carbon, along with other alloying elements, such as molybdenum, aluminum, or titanium.
These magnetic steels cannot be hardened by heat treatment but can be strengthened by cold working.
Martensitic Stainless Steel
It contains 11-17% chromium, less than 0.4% nickel, and up to 1.2% carbon.
These are magnetic and are similar in composition to the ferritic group but contain higher carbon and lower chromium to permit hardening by heat treatment.
So here you have to know all aspects related to ferrous metal.
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