Here is a list of non-ferrous metals used in engineering structures.
1. Aluminium:
The aluminium occurs in abundance on the surface of earth. It is available in various forms such as oxides, sulphates, silicates, phosphates, etc. But it is commercially produced mainly from bauxite (AI2O3, 2H2O) which is hydrated oxide of aluminium.
The aluminium is extracted from bauxite ores as follows:
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(i) The bauxite is ground and then it is purified.
(ii) It is then dissolved in fused cryolite which is a double fluoride of aluminium and sodium, AlF3, 3NaF.
(iii) This solution is then taken to an electric furnace and the aluminium is separated out by electrolysis.
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Following are the properties of aluminium:
(i) It is a very good conductor of heat and electricity.
(ii) It is a silvery white metal with bluish tinge and it exhibits bright lustre on a freshly broken surface.
(iii) It is a non-magnetic substance.
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(iv) It is rarely attacked by nitric acid, organic acid or water. It is highly resistant to corrosion.
(v) It is light in weight, malleable and ductile.
(vi) It is very soft.
(vii) It melts at 660°C and its boiling point is 2056°C.
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(viii) It possesses great toughness and tensile strength.
(ix) It readily dissolves in hydrochloric acid.
(x) Its specific gravity is about 2.70.
2. Cobalt:
The cobalt is found to occur in free state in meteorites. Its two important ores are arsenide and sulphoarsenide.
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Manufacture of Cobalt:
The ores are purified and they are then fused with limestone or sand in a blast furnace. It gives impure oxide of cobalt. The impurities from this oxide of cobalt are removed by various wet processes.
Properties of Cobalt:
Following are the properties of cobalt:
(i) If cobalt is red hot, it can decompose steam.
(ii) If it is in a finely ground powder form, it may absorb hydrogen to the extent of about 150 times its volume.
(iii) It is a lustrous white metal.
(iv) It is magnetic and can retain its magnetic properties upto a temperature of about 1100°C.
(v) It is malleable and ductile.
(vi) It is not affected by atmosphere at ordinary temperature.
(vii) It is not attacked by alkalies.
(viii) Its specific gravity is 8.90.
(ix) It melts at 1480°C and its boiling point is 2900°C.
Uses and application of Cobalt:
The cobalt is widely used in the preparation of special alloy steels, ceramic products, television articles, etc. It forms the basis of all blue colours used in glass and porcelain manufacture.
3. Copper:
The copper occurs in practically all important countries of the world. Its principal ores are Cuprite Cu2O, Copper glance Cu2S, Copper pyrites CuFeS2, Malachite CuCO3, Cu(OH)2 and Azurite 2CuCO3, Cu(OH)2.
The approximate content of copper in the above principal ores is as follows:
Cuprite or red oxide of copper – 88%
Copper glance – 80%
Copper pyrites – 35%
Malachite or green carbonate of copper – 56%
Azurite or blue malachite – 55%.
Manufacture of Copper:
The copper is manufactured by a laborious method and the treatment to be adopted largely depends on the quality of copper ores.
Following is the general outline of the modern process of copper manufacture:
(i) The ores, usually pyrites, are cleaned and crushed and they are then calcined in a reverberatory furnace.
(ii) The calcined ores are mixed with silica and a small quantity of coke. The mixture is then smelted in a blast furnace.
(iii) The melted metal is oxidized in the Bessemer converter. It gives blister copper.
(iv) The impurities contained in blister copper are removed by melting it in a reverberatory furnace in presence of air.
(v) The slag is removed and pure copper to the extent of about 99.70 per cent is obtained.
(vi) Very pure copper or 100 per cent copper is obtained by the process of electrolysis.
Properties of Copper:
Following are the properties of copper:
(i) It becomes brittle just below its melting point.
(ii) It can be worked in hot or cold condition, but it cannot be welded.
(iii) It has a peculiar reddish brown colour.
(iv) It is a good conductor of hat and electricity.
(v) It is attacked by steam at white heat.
(vi) It is not attacked by dry air, but moist air gives a green coating to the copper surface.
(vii) It is not attacked by water at any temperature.
(viii) It is malleable, ductile and extremely soft.
(ix) It melts at 1083°C and its boiling point is 2300°C.
(x) Its specific gravity is 8.92.
Uses and application of Copper:
The market forms of copper are ingots, sheets, tubes and wires. It is extensively used for making electric cables, alloys, household utensils, electroplating, lighting conductors, dowels in stone masonry, blocks for printing, etc. It is mainly used in the manufacture of alloys of which brass and bronze are important.
4. Lead:
The lead occurs occasionally in free state in nature. In combined form, it mainly occurs as sulphide, the ore being known as the Galena PbS. This is the most important and widely distributed ore of lead. It contains about 86 per cent lead and 14 per cent sulphur. It is always associated with silver sulphide and often gold. A pure galena possesses a metallic bluish lustre of dark grey colour.
The other ores with their approximate lead content are as follows:
Anglesite – 68%
Bournonite – 40%
Cerussite – 77%
Mimetesite – 75%
Pyromorphite – 75%
Manufacture of Lead:
For the extraction of lead from its ores, the various processes have been evolved in different countries.
The galena is used as the chief ore and the process is as follows:
(i) The ores are ground and sieved. The impurities are segregated out as far as practicable. The separation is further accomplished in the flotation machine.
(ii) The coke and metallic iron are added to the ores.
(iii) The mixture is then smelted in a blast furnace.
(iv) The impure lead is obtained which is further purified in a reverberatory furnace.
Properties of Lead:
Following are the properties of lead:
(i) It can be cut with a knife.
(ii) It makes impression on paper.
(iii) It melts at 327.5°C and its boiling point is 1620°C.
(iv) It is a lustrous metal with bluish-grey colour.
(v) It is converted into litharge, when heated strongly in presence of air or oxygen.
(vi) It is not attacked by dry air, but moist air takes away its bright metallic lustre and a dark protective film is produced on the surface of metal.
(vii) It possesses little tenacity.
(viii) It is readily dissolved in dilute nitric acid.
(ix) It is very soft, plastic and almost devoid of elasticity.
(x) Its specific gravity is 11.36.
Uses and application of Lead:
The lead is widely used for making shots, bullets, alloys, storage cells, sanitary fittings, cisterns, water-proof and acid-proof chambers, gas pipes, roof gutters, printing types, damp-proof courses of buildings, cable coverings, preparation of lead oxides for paints, etc.
5. Magnesium:
The magnesium does not occur in free state in nature, but it is a widely distributed element found in the combined state. Its principal ores are magnesite MgCO3, dolomite CaCO3, MgCO3, kieserite MgSO4, H2O and carnallite MgCl2, KCl, 6H2O.
Manufacture of Magnesium:
For obtaining magnesium on a small scale, the anhydrous magnesium chlorite is heated with sodium in presence of coal gas. For large scale production, the magnesium is obtained by the electrolysis of fused carnallite.
Properties of Magnesium:
Following are the properties of magnesium:
(i) It burns when heated in air with a dazzling bluish-white light extremely rich in ultra-violet rays.
(ii) It carries away heat easily.
(iii) If it is in the form of finely divided particles, it burns readily and easily.
(iv) If strongly heated, it can decompose steam.
(v) It is a silver-white metal possessing a high lustre.
(vi) It is ductile and malleable.
(vii) It is not affected by alkalies.
(viii) Its melting point is 651°C and it boils at 1110°C.
(ix) Its thermal coefficient of expansion is high.
Uses and application of Magnesium:
The magnesium is used in photography, fire-works, signalling, paints, whitening paper pulp, etc. It alone cannot be used for structural work. But some of its alloys may be employed for some structural parts. It is used as a refractory material in the form of magnesia bricks for the lining of steel and electric furnaces. It is also used as a cementing material for the manufacture of artificial stone, plaster, tiles, etc.
6. Nickel:
The nickel occurs in free state in meteorites. In combination, it chiefly occurs as sulphide ores and silicate ores. The most important nickel ore is a mineral composed of magnetic iron pyrites with nickel.
Manufacture of Nickel:
The nickel is extracted from sulphide ores as follows:
(i) The ores are cleaned of earthy matter.
(ii) They are roasted in heaps.
(iii) The roasted ores are smelted in blast furnace along with limestone, quartz and coke.
(iv) The molten mixture of nickel and copper sulphide collects at the bottom. It is led to Bessemer converter with basic lining.
(v) After treatment in converter, the metallic nickel is obtained by repeated smelting and electrolysis.
Properties of Nickel:
Following are the properties of nickel:
(i) If nickel is red hot, it can decompose steam.
(ii) If it is in a finely ground powder form, it may absorb hydrogen to the extent of about 17 times its volume.
(iii) It is a greyish white lustrous metal.
(iv) It is capable of taking a high polish and can easily be welded.
(v) It is fairly resistant to the actions of atmosphere and it becomes dull after a long time.
(vi) It is hard, malleable and magnetic.
(vii) It is not attacked by fused alkalies.
(viii) It ranks below iron in electric conductivity.
(ix) Its resistance to corrosion is high.
(x) Its specific gravity is 8.90 and melts at 1452°C. Its boiling point is 2900°C.
Uses and application of Nickel:
The nickel is widely used as a coating for other metals and for the preparation of alloys like German silver, nickel steels, etc. Its practical use is confined to the manufacture of chemical apparatus, crucible, electroplating parts of machines, domestic utensils, etc.
7. Tin:
The tin occurs chiefly as tinstone or cassiterite which is its oxide, SnO2. It is also available in nodules which are known as the stream tin.
Manufacture of Tin:
The tin is extracted from its ore as follows:
(i) The ore is crushed and washed to remove impurities.
(ii) It is then calcined in a revolving calciner.
(iii) The calcined ore is allowed to cool.
(iv) After cooling, it is washed with water.
(v) The liquid is allowed to rest. The refined tinstone collects at the bottom as it is heavy.
(vi) It is then smelted in a furnace with anthracite coal and sand.
(vii) It is finely refined in a reverberatory furnace to obtain commercially pure tin.
Properties of Tin:
Following are the properties of tin:
(i) If a bar of tin is bent, a peculiar noise occurs which is sometimes known as the cry of tin. The cracking noise is due to the internal friction of crystal surfaces.
(ii) It becomes brittle when heated to a temperature of about 200°C.
(iii) It melts at 231.5°C and boils at 2260°C.
(iv) It is a white metal with a brilliant lustre.
(v) It is dissolved in hydrochloric acid (HCl) with evolution of hydrogen.
(vi) It is not affected by dry air.
(vii) It is not attacked by pure water.
(viii) It is soft and malleable.
(ix) Its specific gravity is 7.31.
(x) It withstands corrosion due to acids.
Uses and application of Tin:
The tin is rarely used alone. It is used for plating, lining lead pipes and for the preparation of alloys and solder. The pure tin is commercially used for making evaporating basins, infusion pots, etc. It is also used for giving a protective coating to the copper and iron utensils.
The steel sheets coated with tin are used for making cans for food, fruit and milk industry. The tin-foils are used for silvering of mirrors and for wrapping up cheese, chocolates, tobacco, toilet soaps, etc.
8. Zinc:
The zinc does not occur in free state in nature. Its principal ores are zincite or red zinc ZnO, franklinite ZnO, Fe2O3, calamine or zinc-copper ZnCO3 and zinc blende ZnS. A good quality of zinc blende may contain 50% of zinc. The pure ZnS contains about 65% of zinc. It is the chief source of the metal.
Manufacture of Zinc:
The zinc ore is heated in an electric furnace to remove all volatile constituents present in the ore. The zinc is liberated in the form of vapour. This vapour is then condensed to get the metallic zinc.
Properties of Zinc:
Following are the properties of zinc:
(i) It burns with a greenish white flame when strongly heated in air.
(ii) It may be drawn into wires and rolled into sheets between temperature range of 100°C to 150°C.
(iii) It melts at 419.4°C and boils at 907°C.
(iv) It is a bluish white metal.
(v) It is brittle at the ordinary temperature.
(vi) It is a good conductor of heat and electricity.
(vii) It is not affected by dry air.
(viii) It is not affected by pure water.
(ix) It resists corrosion.
(x) Its specific gravity is 7.14.
(xi) If it comes in contact with iron, copper or lead in presence of moisture, the galvanic action starts and the zinc is quickly destroyed.
(xii) It should be kept clear of lime and calcareous substances.
(xii) It is harmfully attacked and ultimately destroyed by acid, hot water and sea salt.
Uses and application of Zinc:
The zinc is used in electric cells, for galvanizing, in the preparation of alloys, paints, etc. The zinc has great value as a protective covering or coat to iron works, plain and corrugated sheets, iron vessels, etc. and as a lining to the drinking water storage tanks.