Q.1 What do you mean by ferrous metals? Give its classification?
Related Questions -
Q. Explain the properties & application of cast iron. (AKTU - 2009-10)
Q. Name the three alloy of ferrous metals and write their application. (AKTU - 2009-10)
Ans. Those metals which contain iron as main constituent are known as ferrous metals. e.g. pig iron, cast iron, wrought iron, steel and their alloys. Pig iron is the principal raw material for all ferrous metals.
Pig Iron: -
All iron and steel products are derived originally from pig iron. This is the raw material obtained from the chemical reduction of iron ore in the blast furnace. The process of reduction of iron ore to pig iron is called smelting. The main raw materials required to produce pig iron are iron ore, coking coal and flux. Most commonly used flux is limestone. High amount of carbon in pig iron makes its very hard and brittle and unsuitable for making useful articles. Therefore pig iron is refined and remelted to produce other varieties of iron and steel.
Wrought Iron: -
This is the purest form of Iron. Wrought Iron contains less then 0.1% carbon with about 1-3% finely divided slag uniformly distributed in the metal. Wrought Iron is produced by Puddling and Auston process. Wrought iron is a very ductile and malleable metal therefore it is very suitable for wire drawing and making sheets. It offers resistance to corrosion. It finds its maximum use in forged articles. Ultimate strength of wrought iron can be increased by cold working process which is followed by AGEING. It is usually used in the manufacturing of pipes, ship building, cranes, hooks, agricultural equipments, railway couplings, etc.
Cast Iron: - (AKTU - 2010 - 11)
Cast Iron is a general term applied to a large variety of iron-carbon alloys containing 2-4.5% carbon. It has at least 6 elements i.e., iron, carbon, silicon, manganese, phosphorus and sulphur. It melts at 1150oC to 1250oC. It has the ability to take good casting impression. It is a brittle material. It can machined easily to required tolerances.
Classification of Cast Iron: -
It is classified as follows :
(i) Grey Cast Iron
(ii) White Cast Iron
(iii) Malleable Iron
(iv) Spheroidal gray iron or Ductile Iron
(v) Inoculated Iron
(vi) Alloy Cast Iron.
Gray Cast Iron: -
It has following composition :
Carbon content - 3 - 3.75%
Silicon - 1 - 2.75%
Manganese - 0.4 - 1%
Phosphorous - 0.15 - 1%
Sulphur - 0.02 - 0.15%
Rest is Iron
Because of presence of graphitic carbon, it appears grey hence called grey cast iron. Graphite flakes act as stress raisors thus making gray iron brittle in tension. It is strong in compression. It has negligible ductility. Although it is machinable, yet machinability varies with variation of its micro-constituents. Its machinability, can be increased by Annealing. Gray cast iron can be welded by electric arc welding and gas welding. It has good castability due to its low shrinkage during solidification. It is used in the production of automobile cylinders, pistons, machine castings, water pipes, etc.
White Cast Iron: -
It has following constituents :
Carbon content - 1.75 - 2.3%
Silicon - less than 0.4%
Phosphorus - less than 0.2%
Sulphur - less than 0.12%
and rest is iron.
White cast iron contains all its carbon as iron carbide which gives white appearance to the fracture of this iron. It has a good casting properties but has poor weldability. It is produced by rapid cooling of grey iron by modifying graphitizing elements (like silicon). Rapid cooling rate is called chilling.
It finds in applications in the manufacturing of chilled rolls, brake shoes, rolls for rolling mills, etc.
Malleable Iron: -
Malleable cast iron is produced by annealing of white cast iron. To malleabilize the castings, following two methods are used :
(a) White Heart Process: -
In this process, the castings composed of cast iron with most of its carbon is in combined state and packed in iron or steel boxes and surrounded by haematite ore. The boxes are slowly heated upto 950 - 1000oC and maintained at this temperature for 4 - 5 days. After this much heating, part of the carbon is oxidized out of castings and the rest is dispersed in the finely divided forms throughout the casting. The process of decarborization is called malleabilizing. The resulting casting is tough and is capable of withstanding heat treatment without rupture.
(b) Black Heart Process: -
In this process, castings are packed in inert material i.e. ferrous silicate scale or slag and heated up to 1000oC for 2-3 days in neutral atmosphere. The temperature is so controlled that the whole iron carbide in white cast iron is decomposed into “temper Carbon”. Black appearance of fractures of these castings owe to the temper graphite. Such malleabilized castings are called black heart and consist almost of graphite and ferrite. It is tougher than gray CI and more resistant to bending and twisting.
Application: -
Automobile, Tractor, Gear housing, plough parts, etc.
Spheroid Graphite Cast Iron or Ductile Iron: -
It is produced by first desulphurising completely molten gray cast iron and then adding magnesium in the form of nickel magnesium alloy to the laddle before casting. Magnesium causes graphite of grey cast iron to take the nodular a spheroidal form. It helps to transform brittle cast iron into a tough strong material which has a good castability.
Application: -
It find its applications in the manufacturing of crankshafts, heavy machinery frames, marine castings, agricultural equipments, etc.
Inoculated Cast Iron: -
When Inoculauts like ferromanganese, calcium silicide, nickel shots and ferro-silicon are added to molten white cast iron just before casting, inoculated iron castings are produced with graphite in flake form. Inoculation increases strength improves uniform properties in varying sections and makes iron able for high duty castings.
Application: -
Drop forgings, Dies and process, lathe beds, light blanking, air cooled engine cylinders, etc.
Alloy Cast Iron: -
Different alloying elements like Nickel, Chromium, Molybdenum, etc are used to produce alloy cast iron to increase mechanical property of cast iron and enable it for a wide range of application. Nickel is the prime alloying element in cast iron.
Q.2 Explain in brief about steel, carbon steel and Alloy steel?
Related Questions -
Q. Classify steel on the basis of carbon percentage. Also write properties and use of them. (AKTU - 2010 - 11)
Ans. Steel is a malleable alloy of iron and carbon. Carbon content usually varies from 0.8 to 1.5% in steel. Maximum percentage of carbon in steel may be 2%.
Carbon Steel: -
Carbon steel owes its distinctive properties chiefly to the carbon content it contains. Besides iron and carbon steel contain small amounts of silicon, sulphur, phosphorus and manganese. Silicon and manganese are desirable and beneficial elements, while sulphur and phosphorus are undesirable. They can’t be eliminated completely but can be kept to lowest amount.
Classification of Carbon Steel: -
Carbon steel (plain carbon steel) can be classified on the bases of their carbon content.
(a) Low Carbon Steel (Mild Steel): -
Carbon steel having carbon content between 0.15% and 0.3% are called mild steel (low carbon steel).
When carbon content in a plain carbon steel is less then 0.15% (from 0.08% to 0.15%), the steel is called dead mild steel, low carbon steels are not hardened by heat treatment.
Application: -
(i) Dead MS thin sheets, rod, solid drawn tubes,
(ii) MS-Boiler plates, steel channels and angles, drop forgings, cash hardened parts, etc.
(b) Medium Carbon Steel: -
Carbon steel in which carbon content ranges from 0.3% to 0.6% are called medium carbon steel. This steel, can be hardened by heat treatment.
Application: -
Shafts, fish plates, razors, die blocks, gears, agriculture tools, etc.
(c) High Carbon Steel: -
Carbon steel having carbon content between 0.6% and 1.4% are called high carbon steel.
With the increase in carbon content, strength and hardness of steel increase. Strength of steel is almost maximum at about 0.8% carbon, after that, hardness continues to increase but strength starts decreasing. Both machinability and ductility of carbon steel decrease with an increase in carbon content from mild steel onwards.
Application: -
Large forging dies, laminated springs, drills, broaches, reamers, milling cutters, etc.
Alloy Steel: - (AKTU - 2012 - 13)
Alloy steel are those which owes their distinctive properties chiefly to elements other than carbon or jointly to such other elements and carbon. Alloy steel is further classified into two groups :
(a) Low Alloy Steel: -
Alloy steel having alloying elements less than 8% is called “low alloy steels”.
(b) High Alloy Steels: -
Alloy steels having alloying elements greater than 8% are called “High alloy steels”.
Q.3 Write short notes on steel.
Ans. Steel basically differs from cast iron in the amount of carbon conterst contained by it. It is not only the quantity of carbon, which makes the difference but also the form in which it is present. Insteel the amount of the carbon present is upto 1.5 percent and it is completely in the combined form. Higher the percentage of this carbon, harder and tough is the steel. Carbon content cannot be increased in the metal in chemically combined from beyond 1.5 percent. Thus steel can be said to be an alloy of iron and carbon with the carbon consist to a maximum of 1.5 percent. These steels are called plain carbon steels.
Application of plain carbon steel: -
Related Questions -
Q. Explain the properties & application of cast iron. (AKTU - 2009-10)
Q. Name the three alloy of ferrous metals and write their application. (AKTU - 2009-10)
Ans. Those metals which contain iron as main constituent are known as ferrous metals. e.g. pig iron, cast iron, wrought iron, steel and their alloys. Pig iron is the principal raw material for all ferrous metals.
Pig Iron: -
All iron and steel products are derived originally from pig iron. This is the raw material obtained from the chemical reduction of iron ore in the blast furnace. The process of reduction of iron ore to pig iron is called smelting. The main raw materials required to produce pig iron are iron ore, coking coal and flux. Most commonly used flux is limestone. High amount of carbon in pig iron makes its very hard and brittle and unsuitable for making useful articles. Therefore pig iron is refined and remelted to produce other varieties of iron and steel.
Wrought Iron: -
This is the purest form of Iron. Wrought Iron contains less then 0.1% carbon with about 1-3% finely divided slag uniformly distributed in the metal. Wrought Iron is produced by Puddling and Auston process. Wrought iron is a very ductile and malleable metal therefore it is very suitable for wire drawing and making sheets. It offers resistance to corrosion. It finds its maximum use in forged articles. Ultimate strength of wrought iron can be increased by cold working process which is followed by AGEING. It is usually used in the manufacturing of pipes, ship building, cranes, hooks, agricultural equipments, railway couplings, etc.
Cast Iron: - (AKTU - 2010 - 11)
Cast Iron is a general term applied to a large variety of iron-carbon alloys containing 2-4.5% carbon. It has at least 6 elements i.e., iron, carbon, silicon, manganese, phosphorus and sulphur. It melts at 1150oC to 1250oC. It has the ability to take good casting impression. It is a brittle material. It can machined easily to required tolerances.
Classification of Cast Iron: -
It is classified as follows :
(i) Grey Cast Iron
(ii) White Cast Iron
(iii) Malleable Iron
(iv) Spheroidal gray iron or Ductile Iron
(v) Inoculated Iron
(vi) Alloy Cast Iron.
Gray Cast Iron: -
It has following composition :
Carbon content - 3 - 3.75%
Silicon - 1 - 2.75%
Manganese - 0.4 - 1%
Phosphorous - 0.15 - 1%
Sulphur - 0.02 - 0.15%
Rest is Iron
Because of presence of graphitic carbon, it appears grey hence called grey cast iron. Graphite flakes act as stress raisors thus making gray iron brittle in tension. It is strong in compression. It has negligible ductility. Although it is machinable, yet machinability varies with variation of its micro-constituents. Its machinability, can be increased by Annealing. Gray cast iron can be welded by electric arc welding and gas welding. It has good castability due to its low shrinkage during solidification. It is used in the production of automobile cylinders, pistons, machine castings, water pipes, etc.
White Cast Iron: -
It has following constituents :
Carbon content - 1.75 - 2.3%
Silicon - less than 0.4%
Phosphorus - less than 0.2%
Sulphur - less than 0.12%
and rest is iron.
White cast iron contains all its carbon as iron carbide which gives white appearance to the fracture of this iron. It has a good casting properties but has poor weldability. It is produced by rapid cooling of grey iron by modifying graphitizing elements (like silicon). Rapid cooling rate is called chilling.
It finds in applications in the manufacturing of chilled rolls, brake shoes, rolls for rolling mills, etc.
Malleable Iron: -
Malleable cast iron is produced by annealing of white cast iron. To malleabilize the castings, following two methods are used :
(a) White Heart Process: -
In this process, the castings composed of cast iron with most of its carbon is in combined state and packed in iron or steel boxes and surrounded by haematite ore. The boxes are slowly heated upto 950 - 1000oC and maintained at this temperature for 4 - 5 days. After this much heating, part of the carbon is oxidized out of castings and the rest is dispersed in the finely divided forms throughout the casting. The process of decarborization is called malleabilizing. The resulting casting is tough and is capable of withstanding heat treatment without rupture.
(b) Black Heart Process: -
In this process, castings are packed in inert material i.e. ferrous silicate scale or slag and heated up to 1000oC for 2-3 days in neutral atmosphere. The temperature is so controlled that the whole iron carbide in white cast iron is decomposed into “temper Carbon”. Black appearance of fractures of these castings owe to the temper graphite. Such malleabilized castings are called black heart and consist almost of graphite and ferrite. It is tougher than gray CI and more resistant to bending and twisting.
Application: -
Automobile, Tractor, Gear housing, plough parts, etc.
Spheroid Graphite Cast Iron or Ductile Iron: -
It is produced by first desulphurising completely molten gray cast iron and then adding magnesium in the form of nickel magnesium alloy to the laddle before casting. Magnesium causes graphite of grey cast iron to take the nodular a spheroidal form. It helps to transform brittle cast iron into a tough strong material which has a good castability.
Application: -
It find its applications in the manufacturing of crankshafts, heavy machinery frames, marine castings, agricultural equipments, etc.
Inoculated Cast Iron: -
When Inoculauts like ferromanganese, calcium silicide, nickel shots and ferro-silicon are added to molten white cast iron just before casting, inoculated iron castings are produced with graphite in flake form. Inoculation increases strength improves uniform properties in varying sections and makes iron able for high duty castings.
Application: -
Drop forgings, Dies and process, lathe beds, light blanking, air cooled engine cylinders, etc.
Alloy Cast Iron: -
Different alloying elements like Nickel, Chromium, Molybdenum, etc are used to produce alloy cast iron to increase mechanical property of cast iron and enable it for a wide range of application. Nickel is the prime alloying element in cast iron.
Q.2 Explain in brief about steel, carbon steel and Alloy steel?
Related Questions -
Q. Classify steel on the basis of carbon percentage. Also write properties and use of them. (AKTU - 2010 - 11)
Ans. Steel is a malleable alloy of iron and carbon. Carbon content usually varies from 0.8 to 1.5% in steel. Maximum percentage of carbon in steel may be 2%.
Carbon Steel: -
Carbon steel owes its distinctive properties chiefly to the carbon content it contains. Besides iron and carbon steel contain small amounts of silicon, sulphur, phosphorus and manganese. Silicon and manganese are desirable and beneficial elements, while sulphur and phosphorus are undesirable. They can’t be eliminated completely but can be kept to lowest amount.
Classification of Carbon Steel: -
Carbon steel (plain carbon steel) can be classified on the bases of their carbon content.
(a) Low Carbon Steel (Mild Steel): -
Carbon steel having carbon content between 0.15% and 0.3% are called mild steel (low carbon steel).
When carbon content in a plain carbon steel is less then 0.15% (from 0.08% to 0.15%), the steel is called dead mild steel, low carbon steels are not hardened by heat treatment.
Application: -
(i) Dead MS thin sheets, rod, solid drawn tubes,
(ii) MS-Boiler plates, steel channels and angles, drop forgings, cash hardened parts, etc.
(b) Medium Carbon Steel: -
Carbon steel in which carbon content ranges from 0.3% to 0.6% are called medium carbon steel. This steel, can be hardened by heat treatment.
Application: -
Shafts, fish plates, razors, die blocks, gears, agriculture tools, etc.
(c) High Carbon Steel: -
Carbon steel having carbon content between 0.6% and 1.4% are called high carbon steel.
With the increase in carbon content, strength and hardness of steel increase. Strength of steel is almost maximum at about 0.8% carbon, after that, hardness continues to increase but strength starts decreasing. Both machinability and ductility of carbon steel decrease with an increase in carbon content from mild steel onwards.
Application: -
Large forging dies, laminated springs, drills, broaches, reamers, milling cutters, etc.
Alloy Steel: - (AKTU - 2012 - 13)
Alloy steel are those which owes their distinctive properties chiefly to elements other than carbon or jointly to such other elements and carbon. Alloy steel is further classified into two groups :
(a) Low Alloy Steel: -
Alloy steel having alloying elements less than 8% is called “low alloy steels”.
(b) High Alloy Steels: -
Alloy steels having alloying elements greater than 8% are called “High alloy steels”.
Q.3 Write short notes on steel.
Ans. Steel basically differs from cast iron in the amount of carbon conterst contained by it. It is not only the quantity of carbon, which makes the difference but also the form in which it is present. Insteel the amount of the carbon present is upto 1.5 percent and it is completely in the combined form. Higher the percentage of this carbon, harder and tough is the steel. Carbon content cannot be increased in the metal in chemically combined from beyond 1.5 percent. Thus steel can be said to be an alloy of iron and carbon with the carbon consist to a maximum of 1.5 percent. These steels are called plain carbon steels.
Application of plain carbon steel: -
Q.4 Compare between plain carbon steel and alloy steel?
Ans. Comparison between plain carbon steel and alloy steel is as follows :
