List of Metals Used in Industries | Industrial Engineering

Engineering materials play a vital role in our day-to-day life. We use a variety of metals and non-metals such as cast iron, steel, aluminium, copper, zinc, lead, tin, glass, rubber, wood, plastic, etc. in automobile industries. Metal (ferrous and non-ferrous) play a vital role and are extensively used in manufacturing industries because of their excellent mechanical properties.

Ferrous Metals Used in Industries:

The ferrous metals contain iron as their main constituents. The important ferrous metals used in industries are pig iron and cast iron and, hence, we shall discuss cast iron and steel and their alloys.

1. Iron:

Iron ore is the base material for iron and steel. Hematite and magnetite are the main ores which will have about 55-60% iron. Iron ore may have the combination of alumina, silica, phosphorous, manganese, sulfur, and others. Pig iron is prepared in blast furnace which is the base metal for all steel furnaces which contain 3.9% carbon, 1% silicon, 1% manganese, and a small percentage of sulfur and phosphorous.

It is hard and brittle and too weak in strength. Its ductility is poor. It is mainly used for making magnets. Iron can be alloyed with carbon to form alloys which has wide application in industries. The alloying materials are silicon, manganese, chromium, nickel, vanadium, tungsten, etc. to enhance their mechanical properties.

Ferrous Alloys:

Ferrous metals contain iron as the main constituents. There are many ferrous metals used in industries like pig iron, cast iron, wrought iron, and steel. However, only the cast iron and steel will be discussed below as they are important.

The important ferrous metals are as follows:

Cast Iron:

Cast iron is an alloy of iron and carbon. It has carbon content of more than 2% and lies in between 2% and 6.6%. For practical reasons, normally 2—4% of carbon content is permissible due to excellent casting properties. It contains small amount of silicon, sulfur, phosphorous, and manganese. Cast iron has low melting temperature (about 1198°C).

So, it can be melted easily and requires less cost involved in fuel. During casting, it can flow in moulds very easily. Cast iron is a brittle and hard material due to the presence of high percentage of carbon. It has low cost and good casting properties like machinability, wear resistant, and high compressive strength.

During casting, it may form blowholes, a defect in casting. Cast iron can be alloyed with nickel, chromium, molybdenum, copper, silicon, and manganese. These elements give more strength and much improved properties of high wear resistance and heat resistance.

The alloy of cast iron can be extensively used for making internal combustion (IC) engine parts, namely piston, piston rings, crankcase, etc.

i. Grey Cast Iron:

Grey cast iron is an ordinary cast iron used for commercial purpose. It has 3.1-3.4% of carbon, 0.09-2.7% of silicon, and a small percentage of phosphorous, sulfur, and the rest is iron. Silicon makes the cast iron soft. It produces good casting without blowholes. It becomes easier to machine. It is used in making cylinder block of multi-cylinder engines, CI pipes, and pipe fittings.

ii. White Cast Iron:

White cast iron has 2-2.3% carbon. In addition to carbon as alloying element, it has 0.84-1.3% silicon, 0.1-0.5% manganese, 0.03-0.2% phosphorous, and a trace of sulfur and the rest is iron as main constituents. It is used to form malleable cast iron and wrought iron. It holds carbon in the form of carbide to make it hard and is also called malleable iron.

Cast Iron Impurities:

Cast iron impurities are as follows:

i. Silicon:

Cast iron holds about 3% silicon as alloying element. It makes the cast iron soft to make good machining. It forms good casting without any casting defects.

ii. Sulfur:

It makes the cast iron hard and brittle. Large percentage of sulfur gives poor result in casting. Hence, the sulfur content is always kept as low as 0.1%.

iii. Manganese:

It makes the cast iron white and hard. The percentage of manganese is kept as low as 0.74%. It helps to control the harmful effects produced by the presence of sulfur content.

iv. Phosphorous:

It is well known that in casting process two properties, fusibility and fluidity, of metals are important. The content of phosphorous forms the ability to have better fusibility and fluidity but it increases the brittleness. The percentage composition of phosphorous is kept low and should not exceed 1%.

2. Steel:

Steel is an alloy of iron and carbon. The alloying element is carbon. The content of carbon present is up to 1.4%. The carbon content forms iron carbide (Fe₃C) which increases hardness and strength. In addition to this, steel may have some other elements such as silicon, sulfur, and manganese to improve certain desirable properties.

Nowadays, most of the steels are produced in the form of plain carbon steel. Plain carbon steels are those which possess properties mainly due to its carbon percentage and it will not have more than 0.5% silicon and 1.5% manganese.

The plain carbon steel varying from 0.1% carbon to 1.4% carbon is divided into three categories:

(a) Low carbon steel (mild steel): (0.1-0.25% carbon)

(b) Medium carbon steel: (0.25-0.55% carbon)

(c) High carbon steel: (0.55-1.4% carbon)

Plain Carbon Steel:

Among the various alloying elements carbon is the most important. It is present in all the alloys of iron. The maximum amount of carbon that can be alloyed with iron is 6.67%. Alloys with less than 2% carbon are known as steel and for the best result it may be taken as 1.4% carbon. More than 2% carbon has been categorized as cast iron.

In addition to carbon, these alloys also contain silicon, manganese, sulfur, etc. There is an increase of hardness and strength due to the presence of excess carbon. The carbon forms cementite which is brittle. However, it decreases the ductility. Plain carbon steel has poor corrosion resistance. The effect of environment can be minimized by painting and galvanizing the metal surface.

(a) Low Carbon Steel (Mild Steel):

Low carbon steel is defined as the plain carbon steel which has the carbon content in the range of 0.1-0.25%. The properties are changing with the variation of carbon content. It is ductile and soft. It is used to manufacture nails, nuts, bolts, washer, fencing wires, etc.

(b) Medium Carbon Steel:

Medium carbon steel is defined as the plain carbon steel which has the carbon content in the range of 0.25-0.55%. The properties can be varied with the change of carbon content. It has less ductility but more hardness. It has high tensile strength than low carbon steel. It is used for making spindles, shafts, connecting rods, etc.

(c) High Carbon Steel:

High carbon steel is one in which the content of carbon varies in between 0.55% and 1.4%. It has high tensile strength and hard enough. The machining can be done easily. It is used to manufacture files, drills, dies, wrenches, chisels, punches, cutting tool, etc. Besides carbon, there are many other elements in small quantities such as silicon, sulfur, manganese, and phosphorous.

If 0.05-0.3% of silicon is added with low carbon steel, it gives good result. The porosity of the metal is removed. It also removes the gases quickly which forms during casting and there is no chance of forming blowholes.

The steel becomes hard and tough. Manganese acts as de-oxidizing and purifying agents. It makes the low carbon steel more ductile and increases the bending characteristic. Phosphorous makes the steel more brittle and more resistant to atmospheric condition. Sulfur is added to improve the quality of steel.

Alloy Steel:

We have seen that the plain carbon steel contains alloying element carbon with a small percentage of silicon, manganese, and other elements. Plain carbon steel or simply steel will have only the alloying element carbon. Besides carbon, the other alloying elements such as nickel, chromium, vanadium, cobalt, manganese, tungsten, and molybdenum are termed as alloy steel.

Steel is considered alloy steel if it has alloying elements other than carbon. In order to obtain some specific properties, for specific purpose, these alloying elements are added with it. The alloy steels are required when additional characteristics such as ductility, strength, toughness, and corrosion resistance are desirable for a specific purpose.

The effects of these elements are summarized as follows:

i. Nickel:

Steel alloying with 2-4.5% nickel and 0.1-0.4% carbon is used to make sheet steel. It increases the tensile strength, hardness, toughness, and gains ability to reduce rust. It is used to produce IC engine parts such as crankshaft, connecting rods, and boiler plates.

If nickel percentage is increased to 24%, it becomes high heat resistant metal which is suitable to make boiler tubes, sparkplugs, and valves of IC engines. A special kind of steel, known as INVAR, is made with 35% nickel and 0.4% carbon. It is used to make measuring instrument parts, namely pressure measuring instruments and electrical measuring instrument parts.

ii. Chromium:

If chromium is added with steel, it further increases the hardness, strength, and corrosion resistance. Chromium is a good carbide maker and it forms carbide of chromium and iron. A chrome steel contains 0.4-1.5% chromium is used for making steel balls, rollers, bearing balls, racers, etc.

A steel, containing 3.2% nickel, 1.4% chromium, and 0.24% carbon is known as nickel chrome steel. The metal becomes further hard and tough. It is used to make crankshafts of multi-cylinder engines and axles which require high load capacity and strength.

iii. Vanadium:

It gives a pronounced effect of improving hardness of steel. If 0.15-0.25% vanadium with 0.5-1.4% chromium and 0.12-1.1% carbon are added with steel, it produces a remarkable effect of improving toughness and the steel becomes stronger. These are used to make spring, high speed tools, etc.

iv. Tungsten:

If it is added with steel, it shows good quality, gains high strength, and becomes high temperature resistant. It is a very strong carbide maker and forms abrasive resistant grains. Steel containing 18% tungsten, 4% chromium, 1% vanadium, and 0.7% carbon is known as high speed steel. It gains the cutting ability. It is used to make high speed cutting tools such as drillbit, dies, reamers, milling cutters, etc.

v. Manganese:

Addition of manganese in steel reduces the formation of iron sulphide if sulfur is already present in steel. It makes the steel hard and tough. A steel with 10-13% manganese and 0.9-1.2% carbon forms a steel which is hard and tough in nature. It is generally used to make mining and rock cutting tools and rock crushing tools.

vi. Silicon:

Addition of silicon makes the steel hard and it gains the strength but ductility becomes low. Silicon 1.5-2% and 0.1-0.4% carbon added with steel possesses good magnetic properties. It is used to make transformer core, etc.

vii. Molybdenum:

It is a strong carbide maker. Addition of small quantity of molybdenum in between 0.15% and 0.25% along with chromium and manganese increases the tensile strength up to the maximum (hot hardness). The cost of molybdenum is less as compared to tungsten and so, in place of tungsten, it can be used. It is used to prepare aeroplane and automobile parts.

viii. Cobalt:

A small quantity in the range of 1-12% of cobalt is added with high speed tools. It gives hardness up to the maximum limit known as red hardness by retaining hard carbide at high temperature. It increases strength and hardness. It can be effectively used for high temperature operations.

Stainless Steel:

It comes under special category of steels. It is prepared for special purpose such as high speed steel, stainless steel, heat resisting steel, etc. Stainless steel is manufactured by proper heat treatment with proper and correct finishing process. It gains the ability to prevent oxidation and corrosive attack of the environment and corrosive media. There are three types of stainless steel.

i. Ferritic Stainless Steel:

It contains more amount of nickel in the range of 15-20% and 0.1% carbon. It possesses great strength, toughness, and good corrosion resisting. It can be welded, forged, and machined. It can be used for making pipes and food processing plants used in chemical plants. It resists the nitric acid reaction in chemical processes.

ii. Martensitic Stainless Steel:

It contains 10-14% chromium and 0.36% carbon. It has anti-corrosion properties. It can be rolled, machined, and welded. It is used for making turbine blades, shafts, scissors, knives, cutlery etc.

iii. Austenitic Stainless Steel:

It contains 18% chromium and 7% nickel. It has more resistance to corrosion. It has good tensile strength. It is very tough. Machining is very difficult for such steel. It is specially used in chemical plants to make appliances and tanks. The utensils and cutlery are also manufactured with this steel.

Non- Ferrous Metals Used in Industries:

The non-ferrous metals are used in various engineering applications based on their specific properties as compared with ferrous metals in spite of the higher cost. Non-ferrous metals are defined as the metals which contain metals other than iron as their main constituents.

Non-ferrous metals are used due to the following reasons:

Some of the non-ferrous metals are as follows:

i. Aluminium

ii. Copper and its alloy (brass and bronze)

iii. Lead

iv. Tin and its alloy (Babbitt)

v. Zinc

vi. Nickel and its alloys (monel and nichrime)

vii. Magnesium

We shall now discuss these metals and their alloys in details below:

1. Aluminium:

It is white in color and light in weight. It has low melting temperature (658°C) and high thermal conductivity. It is found soft and weak in most of the purposes. If it is alloyed with other elements in small quantity, it gains the hardness and rigidity. It is a good electrical conductor. It is used in making IC engine pistons, aerospace, and marine industries. It is a good corrosion resistance. It is soft and ductile. Aluminium is difficult to weld and solder. It is used for making utensils and overhead cables.

Hindalium is the most popular aluminium alloys. It is the alloy of aluminium and magnesium with a small quantity of chromium.

2. Copper:

It is most widely and universally used non-ferrous metals in engineering industries. It is very soft, malleable, and ductile. It has reddish-brown appearance of pleasing color appealing to the eyes. It has high thermal and electrical conductivity. Its melting temperature is 1082°C. It is mostly used for making electrical wires, cables, busbars, transmission cables, and refrigerator pipes.

Two separate pieces of copper can be joined by brazing. It resists corrosion. Copper can be used to make alloys. Brass is the alloy of copper and zinc in which zinc is the main constituents. Bronze is the alloy of copper and tin in which tin is the main constituents.

i. Brass (Alloy of Copper):

Brass is the most widely used alloy of copper. In industries, various types of brass are used depending upon the proportion of copper and zinc. With zinc content up to 38%, copper forms a structure which has high ductility. With zinc content in between 38% and 45%, it forms CuZn which increases the hardness. The strength of brass is further increased when small amounts of nickel and manganese are added.

The addition of lead (1-2%) improves the machining operation of brass. It has low thermal and electrical conductivity as compared to copper. Brass is very resistant to environmental condition. Corrosion is not so prominent as compared to other metals. It is used for making valves, cocks fittings, musical instruments, utensils, etc.

ii. Bronze (Alloy of Copper):

Bronze is an alloy of copper and tin. It has 80-90% copper and 5-20% tin. The hardness and strength increases with the increase of tin content. The metal is hard but can be shaped or rolled into wires, rods, tubes etc. It is used to make status. Bronze is costly as compared to brass.

iii. Gun Metals (Alloy of Copper):

It is an alloy of copper, tin, and zinc. It has 87% copper, 10.0% tin, and 3% zinc. The zinc is added to increase the fluidity and to make the metal clean in appearance. Frozing operation can be done to shape the metal. It is not suitable to work in cold state. The metal is strong enough and it is a corrosion resistant with humid atmosphere and water exposure. It is used to make boiler fittings, bushes, bearing, gland, etc.

3. Lead:

It is a metal of bluish grey color. The melting temperature is very low (325°C). It is very soft and it can be cut easily. It is usually used for making solders. It can be alloyed with other elements. An alloy of 82% lead, 16% antimony, 1.5% tin, and 0.5% copper is used for making large size bearing.

4. Tin:

It is called white metal. It shines brightly. It is soft, malleable, and ductile. It can be rolled into a very thin sheet. It is used for making alloys. It is very useful in many industrial applications.

Babbitt Metal (Tin Base Alloy):

It is a tin base alloy to contain 88% tin, 7.5% antimony, and 3.9% copper. It is very soft having less strength and low coefficient of friction. It can be used to make bearing to be fitted in cl casing to take up high pressure and load. The alloy containing 85% tin and 14% lead is very much suitable for soldering purposes.

5. Zinc:

It is slightly bluish white metal. Zinc is used in engineering industries because of its low melting temperature (419°C) and high corrosion resistant. It forms a protective layer of oxides which protect the metal from corrosion. It is very much used in printing work used by printing industries. It is used for galvanizing the steel to protect from corrosion. It is used to make die which is very popular in die industries.

The metal is very malleable and ductile at normal temperature. It can be rolled within 100°C to make sheets and wire. At high temperature, exceeding 100°C, it cannot be used for service. It becomes so brittle that it can be powdered. The metal forms alloy with aluminium, copper, and magnesium. The alloying elements improve the mechanical properties such as hardness and ductility.

6. Nickel:

It is white in color and looks like silver. It is capable of holding high polishing. It is hard enough. It becomes quite malleable when it is alloyed with small amount of carbon (0.006%). It has low ductility, but improves with addition of very small amount of magnesium in it.

It prevents the metal to reach with most of the acids, but it dissolves in nitric acid. The steel, copper, and brass can be coaled with nickel to make the surface clean, smooth, and attractive. It can be alloyed with other element. It is broadly used in industries due to its high mechanical properties and corrosion resistant.

i. Monel Metal (Nickel Base Alloy):

It is an important alloy of nickel and copper. It contains 68% nickel and 28% copper and the rest is other constituents such as silicon, carbon, iron, and manganese. It has melting temperature of 1365°C. It is strong, tough, and ductile. It is much superior to brass and bronze and having good corrosion resistant. It is used for making propellers, condenser tubes, steam turbine blades, food processing plant equipments, salty water exposed propellers, and equipments.

ii. Nichrome (Nickel Base Alloy):

It is a nickel base alloy. It consists of 65% nickel, 15% chromium, and 20% iron. It is high heat and oxidation resistant. It is used in making electrical resistance wire for electrical furnace, strip heaters, and heating elements used in electrical header.

7. Magnesium:

It is designated as light weight metal used in engineering industries. Its alloys are used because of their light weight and very good mechanical properties. It is used where weight has the prime importance. It is used in aerospace applications involving very high speed. It is hard as compared to aluminum. The machining of this metal and alloy is easy and requires less power for its operation. It can form alloy with aluminium, zinc, copper, and cadmium.

It cannot form alloys with iron and chromium. It can be easily welded by traditional welding method. The metal can be used to form sheets, wires, and tubes. The magnesium ribbon and powder can be made which are quite useful in engineering applications. In powder form, it is used in manufacturing of flash light for production of rockets and signals.