158 METALLURGY OF CAST IRON.
used Bessemer 1.85 to 2.00 in silicon with excellent success in making electric street car motor gear wheels. These wheels, as many know, are cast in a "blank" and the teeth are milled out. When first starting in to make these castings it was a '' trick '' of ours to take a pin hammer and strike upon the teeth of a spoiled wheel until the tooth would flatten out as if one were pounding a piece of wrought iron. This was partly due to low phosphorus, causing the iron to possess a malleable toughness. Bessemer containing from 1.95 to 2.25 silicon would make an excellent iron for all castings such as. ordinary weight of lathes and planers. For heavy punches and shears it would be well to have the iron range from 1.10 to 1.30 in silicon, with sulphur about .030 in the pig. It is to be remembered that owing to Bessemer being low in phosphorus it is not as fluid and does not run a mould as well as Fotindry iron. Nevertheless, it can be melted "hot" enough to ran castings as thin as " stove plate," if the liquid metal is not retained too long in the ladle or has not to run up too far in a mould, or a long distance from the 'c gate; '' but cannot be recommended for such light work.
A founder can utilize common scrap with Bessemer pig metal for all work above stove plate thickness, as in this respect sufficient silicon can be obtained in " Bessemer, " as well as in " Foundry,'' to soften scrap, and thus often assist in cheapening a mixture. Silicon does not, as a general thing, go as high in Bessemer as in Foundry. When silicon exceeds 2.50 per cent, in Bessemer, it is generally called an " off Bessemer," the same as when it exceeds . 10 in phosphorus. To be over 2.50, the limit for silicon in regular Bes-flexible that anyne castings. analysis which may be given is simply an average of the whole, generally taken from the two ends andith the uncertainty of furnace workings when in urgent need of ten hundred jon of iron; and Sir........................ 2,720 "