Soft Iron

—A general term applied to both wrought iron and cast iron which can be shaped with ordinary cutting tools or abraded readily with files. The quality is due to the amount of carbon present and the manner of its combination, and also to the mode of erystallization. Iron which contains practically no carbon, as malleable iron. is very soft, so also is iron which contains the maximum of carbon, as foundry pigs, which may contain as much as 4 or 5 per cent. Carbon when present in the graph i tical condition makes a soft iron, but a very much smaller proportion, when in the combined state, yields white iron, which is extremely hard. Iron allowed to cool slowly in sand is soft, while the same iron cooled rapidly against a metallic chill is hard. Soft iron is used for ordinary castings which have to be machined: tough, slippery and hard iron being reserved for special cla es of work. Where it is nece ary to machine castings of hard iron, grinding or cutting by means of an extremely slow feed is resorted to.