Here is a list of important non-ferrous metals: 1. Aluminium 2. Copper 3. Lead 4. Tin 5. Zinc 6. Magnesium 7. Nickel.
1. Aluminium:
Although aluminium is very abundant in the earth it is never found free, nor can it, by present methods be obtained commercially from clay in which it exists in such great quantities. There is but one commercial ore called ‘bauxite’. Bauxite is hydrated aluminium oxide generally believed to consist of mixture of monohydrate Al2O3. H2O and trihydrate AL2O3 . 3H2O. The chief impurities are oxide, silica, clay and titanium oxide. It is found in districts of Bihar, Madras and Madhya Pradesh.
2. Copper:
Copper is one of the comparatively few metals that are found in the metallic state. It occurs in some minerals such as copper glance (Cu2S), copper pyrites (CuFeS2), malachite (CuCO3.CuO2H2) and azurite (2CuCO3.CuO2H2). Copper ores are found in Burma, Sikkim and, Singhbhoom (Bihar).
3. Lead:
The chief lead ore is lead sulphide, PbS, called galena or galenite. Its distribution is very wide. There are practically no important deposits of lead in which galena is not present to some extent. Silver sulphide is scarcely ever absent from galena; the amount is small, however, generally being less than 0.3 percent.
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The ores are roasted in the reverberatory furnace when lead oxide and sulphate are formed.
To the roasted ore, silica, coke, metallic iron and lime are added and then smelted in a blast furnace. Lead oxide and sulphate react with iron to form ferrous oxide and sulphate, there by releasing metallic lead. Ferrous oxide combines with silica to form slag.
The heavy metal obtained from the bottom of the furnace is further oxidised in Bessemerd converter to remove most of the impurities.
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Physical and Mechanical Properties:
(i) Lead is a bluish grey metal with a high metallic lustre when freshly cut.
(ii) It is the softest and heaviest of all the common metals.
(iii) It can readily be scratched with fingernail when pure.
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(iv) It is least tenacious of the common metals.
(v) It is very malleable and may be readily formed into foil.
(vi) When hot it may be extruded by hydraulic press into tubes, rods and wire.
(vii) Melting point = 327.4°C, boiling point = 1744°C.
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(viii) Its specific gravity is 11.35 and electrical resistivity 20.65 microhms.
(ix) It marks paper.
Uses:
1. It is employed for chemical laboratory and plant drains.
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2. It finds extensive applications as sheaths for electric cables, both overhead and underground.
3. In the form of sheet lead it serves excellently for roofs, gutters and cornices.
4. Large quantities of the metal are consumed in the manufacture of white lead and other paint pigments.
5. Lead enters into greater variety of alloys such as brasses and bronzes, low melting point alloys for sprinkler heads, safety plug in boilers, fire door releases and fuses.
4. Tin:
The chief source of tin is tinstone (or cassiterite) SnO2. Large deposits of tinstone occur in Tairy (Burma) and small quantifies in Hazaribagh (Bihar).
A. The ore is crushed, calcined, washed and then smelted in a furnace using anthracite coal and sand, to obtain crude tin.
B. The crude tin is then refined in a reverberatory furnace to get commercially pure tin.
C. Chemically pure tin is made by electrolytic deposition from commercial tin.
Physical and Mechanical Properties:
(i) It is a brightly shining while metal.
(ii) It is soft and malleable and can be hammered into thin foils.
(iii) Melting point = 232°C, boiling point = 765°C.
(iv) Its specific gravity is 7.3 and electrical resistivity 7.59 microhms.
Uses:
1. Used alone as coating on other metals and alloys owing to its resistance to corrosion.
2. It is employed especially in low melting point alloys as a complete or partial substitute for bismuth. Cadmium is used chiefly in alloys.
3. It is used as moisture proof packing.
5. Zinc:
The common ores of zinc are zincite (ZnO), calamine (ZnCO3) and zinc blende (ZnS). These ores are available in Burma.
The oxide is heated in an electric furnace where the zinc is liberated as vapour.
The vapour is then cooled in condensers to get metallic zinc.
Physical and Mechanical Properties:
(i) It is bluish-grey metal.
(ii) It becomes brittle at 200°C and can be powdered at this temperature
(iii) Its specific gravity is 6.2 and melting point 481°C.
Uses:
1. It is used in sheet form as a corrosion resisting surface or lining or as a protective coating on iron and steel in the form of a galvanized or sprayed surface.
2. It is also used in electric cells and in making brass and other alloys.
6. Magnesium:
It occurs in nature in the following minerals:
Magnesite (MgCO3). Dolomite (CaCO3 MgCO3), Kieserite (MgSO4.H2O) and Carnallite (MgCl3.KC1.6H2O). In India magnesite occurs in Madras and Mysore and dolomite in many states.
7. Nickel:
The most important known deposits of the world are those of the Sudhbury district of Ontario, Canada where nickel bearing iron sulphides containing not over 3 percent of the nickel are found. About 90 percent of the worlds’ production comes from this source.
Physical and Mechanical Properties:
(i) It is silvery white metal capable of taking a high polish.
(ii) It is almost as hard as steel.
(iii) When it contains a small amount of carbon, it is quite malleable. In fact, it may be satisfactorily rolled with as little as 0.005 percent of carbon.
(iv) It is somewhat less ductile than soft steel, but small amounts of magnesium improve the ductility considerably.
(v) Nickel is resistant to the attack of most acids, but it dissolves readily in nitric acid.
(vi) It is very permanent upon exposure to atmosphere.
(vii) It is ferromagnetic below 360°C.
(viii) Melting point = 1452°C, boiling point = 2732°C.
(ix) Its electrical resistivity is 10.9 microohms per cm cube.
(x) Specific gravity is 0.85.
(xi) The annealing temperature lies between 750° and 850°C.
(xii) The forging temperature is 1100° to 1250°C.
Uses:
1. Used as an alloying metal in some types of steel and cast iron, as, also in alloys like monel metal, permalloy, cupro-nickel and nickel-silver.
2. It is extensively used to plate iron and brass as a protective coating.