Excerpt from The Metal Mixer: The Easiest, Simplest and Most Exact Method of Mixing Iron by Chemical Analysis, With Tables and Ready Made Mixtures; Indispensable to Molders, Melters and Foundry Men

Foundry iron contains several of these elements, or im purities as they are sometimes called, but there are only five in which we are mostly interested in. They are silicon, phosphorus, sulphur, manganese and the carbons. Of these five, I think the carbons are the most important, because carbon is the element that gives the iron its character. Foundry iron contains carbonin two distinct forms, calledgraphite carbon and combined carbon. And according to the percentage of each of these carbons, so will the iron be hard or soft. Graphite, or soft carbon, is always high in very soft open grained iron. Combined or hard carbon is always high in very hard, close grained iron. In making mixtures for the cupola it is a more difficult proposition to take hold of the carbons and figure their content than it is silicon or some other element, so, as a rule if We wish to reduce or change the carbons, we generally add some low carbon steel scrap, or change the carbons by using high or low silicon in the mixture, as the case may require. In making mixtures for the ordinary run of machinery castings, we do not trouble about the carbons because we find if silicon is high, graphite carbon will be high also, and if silicon is lowered, graphite carbon will be lower, and com bined carbon will be higher, and the more we lower the silicon the more combined carbon we will get in our cast ings. Chemists long ago proved, if we wish to regulate the carbons it can be done through the silicon, which at once proves that silicon is one of the most important, if not the most important element the founder has to work with. Not only does it influence the carbons, but the other elements also, to a certain extent. For we find if we get silicon normal for the class of work we are making, the other elements also will be normal, especially so, if we use the ordinary run of foundry irons. As the silicon can be raised or lowered as required, it is the first element that should be figured in mixing iron by chemical analysis. When iron contains more than 3 5 per cent silicon, it will begin to get hard. Not hard and strong like a low silicon close grained iron, but hard, short and brittle. So in making mixtures, we never go above 3. 25 per cent silicon, and even that per centage is very rarely used, except in fine stove plate, or work similar to it. There are special mixtures however, for acid proof castings, that call for a much higher percentageof silicon, but these are exceptional, and are not included in the ordinary run of foundry products. Silicon and mangan ese are not affected by mineral and vegetable acids, like graphite carbon, sulphur and phosphorus are. So in making mixtures for this kind of work, the combined carbon, silicon and manganese should be high, especially the silicon, which of course will make the casting very brittle. To make such mixtures takes considerable experimenting, even' by the most experienced chemist and metallurgist. In arranging the different mixtures I have tried to make them as progres sive as possible. The few mixtures from my note books, I thought would give the reader an idea of what has been done with steel mixing. These were made when pig iron was very much cheaper than now, as some were made as far back as 1904. The analysis of different pig irons will also give beginners a working idea of the composition of iron. The few remarks on the influence the different elements have upon the iron will all help the student how to use, and mix them to accomplish a certain purpose.

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