MIXING CASTS OF PIG IRON AT FUR-NACE AND FOUNDRY.
A difference of one per cent, in silicon which can exist between the ends of a cast of pig iron, as shown in the last chapter, should cause any thoughtful person to perceive the wisdom of thoroughly mixing a furnace cast or pile of iron before it is charged into a cupola. This is where the most uniform results in obtaining an even grade of iron are desired in any special line of castings. As an example, if an ill-mixed cast of pig averaging 2.00 per cent, in silicon, with its extreme ends varying i.oo in silicon, was charged without being mixed, one part of the iron charged would contain but 1.50 of silicon while the other portion would contain 2.50 silicon. It is impossible to expect uniform results in castings from such an ill-mixed cast or pile of iron. vSome foundrymen, when first adopting chemistry in making mixtures of iron, have had just such experiences as the above, but, not knowing, it condemned the principle of working by analysis, when, in truth, it was not chemistry that was at fault, but the evils of ill-mixing or ill-diffusion of the silicon in a cast or pile of iron and no attention having been paid to the question of mixing it thoroughly before it was charged into the cupola. The founder adopting chemistry must haveed dull these may exist, but with the reverse conditions the writer has reason to believe, from analyses which he has conducted, that sulphur will generally be found uniformly distributed throughout a casting that has not blown or from any cause been chilled.using different proportions of combined or graphitic carbon A rammer should never be allowed to hit a pattern, as this causes a hard spot on the mould which, in light castings, can change the character of the carbons orhe one 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 "