Ferrous and non-ferrous alloys

Both ferrous and non-ferrous alloys are largely used in all branches of machine-building.

They are fabricated into desired shapes by the following processes: casting, rolling, wire-drawing, forging, pressing (including extrusion), stamping, machining and joining.

The principal ferrous materials used are: pig iron (P.I.), cast iron (C.I.), wrought iron (W.I) and steel, there being various kinds of steels, such as mild steel (M.S.), carbon steel (C.S.) and alloy steels.

Pig iron may be said to be the starting point in the production of all the other ferrous materials. It contains from 92 to 97 per cent iron, the remainder being carbon, silicon, manganese, sulphur and phosphorus.

Cast iron is essentially pig iron which has been modified in structure by remelting in a cupola (usually with the addition of steel scrap) and by casting it into moulds.

Wrought iron, which is now seldom produced, is the iron from which nearly all carbon and most of the sulphur, phosphorus, etc., have been removed by a process known as puddling.

Steel may be roughly defined as an alloy of iron and carbon, with the percentage of carbon ranging from almost zero, in mild steel, up to 1.8 in some tool-steels, with other elements being present in sufficient quantities, the chief alloying elements used being nickel, chromium, molibdenum, silicon, vanadium, tungsten, cobalt and copper. The properties of steels can be changed at will by varying either the composition or the heat treatment, or both.

High-speed steels, for instance, are basically iron-carbon alloys to which various elements, principally tungsten and molibdenum, have been added to improve their hardness, toughness, heat resistance and wear resistance, considerable changes in their properties being attained by slight changes in heat treatment. In selecting a high-speed steel for a particular application the following factors should be taken into consideration: relative were resistance, relative toughness, relative grindability and relative red hardness.

Non-ferrous alloys are nearly all alloys which have been developed to meet the specialised need of industry. They have been grouped according to their dominant element.

Copper-base alloys are used where high thermal or electrical conductivity is the chief requirement.

Aluminium-base alloys are used where light weight is a primary requirement. They are also used because of their resistance to corrosion. Besides, aluminium-base alloys have desirable combinations of mechanical properties with thermal and electrical conductivity.

Casting made of magnesium-base alloys are used where light weight is needed.

There are also lead-base alloys, tin-base alloys, zinc-base alloys and nickel-base alloys.

Both ferrous and non-ferrous metals are known to possess, in some degree, the following properties: elasticity, ductility, malleability, toughness, brittleness, hardness, wear resistance, and corrosion resistance, and corrosion resistance. Each of these properties should be taken into consideration in choosing the proper production processes. In addition, the processing engineer is required to be familiar with one more property – the mechanical strength of materials. It may be described as the ability to be familiar with one more property – the mechanical strength of materials. It may be described as the ability to withstand tensile, compressive and shearing stresses under all kinds of loads and under different temperatures. Mechanical strength is defined by numerous testing machines and methods to be found at any plant and laboratory.