Malleable Iron

Much of the white iron which is produced is further processed into malleable cast iron and this is done by heating it up to a high temperature for a long period, sometimes with the addition of oxygen containing products like iron oxide (rust) and cooling it slowly over a programmed period. As a consequence the carbides break down, not into graphite but free carbon called "temper carbon", producing a metal with superior mechanical properties to those of grey iron and closer to those of mild steel.

The main advantage of this process is that the casting loses a lot of the brittleness, which is the major defect in cast iron, and so it is much more able to resist shocks It is easily machinable, and has good wear resistance so it is suitable for products such as universal joint yokes, connecting rods, transmission gears, differential cases, compressor crankshafts, flanges, hubs, pipe fittings and valve parts for marine, railway, and many other heavy-duty specialised applications. Since castings are made from white iron, however, there are limits to the sizes of products which can be manufactured. Another disadvantage is that the molten metal casting shrinks as it cools which makes accurate castings more difficult and it is sometimes necessary to use attached feeds or risers from reservoirs of liquid metal to offset this.

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