The ferrous metals themselves can be classified into families and these are as

The ferrous metals themselves can be classified into

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The ferrous metals themselves can be classified into ‘families’, and these are as shown in Fig. 4 below. Fig. 4. CLASSIFICATION OF FERROUS METALS Non-metallic materials Metals Engineering materials
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~ Page 14 of 79 ~ 1. PLAIN CARBON STEELS These are essentially alloys of iron and carbon in which the carbon is chemically combined with the iron and traces of other substances such as sulphur and phosphorus which are impurities carried over from the extraction process and a small amount of manganese to offset the deleterious effects of the impurities. None of the other elements is present in sufficient quantities to qualify as an alloying element, hence these simple steels are referred to as plain carbon steels. 2. ALLOY STEELS These are similar to low-carbon and medium-carbon steels with the addition of other metals such as manganese, nickel, chromium, molybdenum and vanadium, in sufficient quantities to materially alter and enhance the properties of the metal. The alloying elements may be present singly or in combination, and the alloys so formed may have increased strength, or improved corrosion resistance, or improved heat resistance. 3. CAST IRONS These are also alloys of iron and carbon but, since the amount of carbon present is greater than 1.7- 2%, not all the carbon is chemically combined and some ‘free carbon’ is present in the form of graphite flakes evenly distributed through the mass of the casting. Because cast iron has not undergone the refinement processes of steel making, the amount of the impurities of sulphur, phosphorus and silicon will be greater. Although tending to weaken the metal, these impurities have the advantage of helping to reduce the metals melting temperature and increase its fluidity so that it can be cast in intricate moulds more easily. The properties of simple grey cast irons may be enhanced by such processes as malleabilising (malleable cast irons) and by the addition of alloying elements (alloy cast irons). 4. WROUGHT IRON This is the nearest commercial material to pure iron. It contains only 0.03% carbon but up to 1.8% impurities, mainly slag inclusions. Wrought iron bars can be readily forged to shape and joined by forge welding. The slag inclusions give it a fibrous structure which results in extreme toughness, malleability and ductility when cold. The slag fibres also improve the corrosion resistance of wrought iron compared with mild steel. Wrought iron was the first malleable and ductile ferrous metal before steel making had been developed and was widely used in early engineering projects and equipment. And because of its relatively low strength, wrought iron is now mainly used for decorative, architectural ironwork. NON-FERROUS METALS These materials refer to all the remaining metals known to mankind.
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