by J.M.Drew St. Paul Publishing Company 1918
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IRON AND STEEL
It is necessary, or at least desirable, that the young blacksmith should know something about the nature of the materials he is to work with. He, of course, knows in a general way something about the different kinds of iron, (cast iron, wrought iron, malleable cast, eac.), which he sees all about him; and has, as a rule, a general knowledge of steel and the uses to which it may be put. He has heard of cast steel, tool steel, machine steel, and Bessemer steel, and has perhaps a somewhat dim idea of what is meant by each of these terms.
Let us in a few words define the different kinds of iron and steel, and show how each is made and for what it may be used. Iron, as every school boy knows, is mined in many parts of the world where it is found mixed with stone and other materials. This mixture is called “ore,” and may be in the form of solid rock or a brown powder or dust. Iron is seldom found in the pure state, but there is a great difference in the purity of the ores found in different parts of the world. This fact will be referred to later. The iron is separated from the ore by a melting process called “smelting,” which consists in melting the ore by great heat so that the iron will flow out in a liquid form. This liquid is not pure iron, but contains more or less impurities, depending upon the purity of the ore from which it is melted. From the smelter the liquid iron flows out in a trench in the earthen floor, and is led into little side trenches of the right size to make a lump of iron which may be handled by one man. These lumps are called “pig iron,” from the fancies resemblance to a litter of pigs which a row of them presents when in the trenches. For a like reason the large trench is called the “sow.”
Common cast iron is made by melting pig iron or a mixture of pig iron and old cast scrap iron and pouring it into molds. The proper mixing of the materials is of great importance in making good castings. Malleable cast iron, or, as it is more commonly called “malleable iron,” is common cast iron from which the carbon has been baked by long-continued heating in red-hot ovens. It is the usual practice to bake it for seven days. By baking out the carbon the iron is made much less brittle, and hence is useful for a great many more purposes than the common cast iron.
Wrought iron, as we usually see it, is made of old wrought iron scrap, which is worked over by being done up in bundles held together by wire or band iron, heated to welding heat and run between rollers to give it the required shape and size. In reworking old scrap great care must be taken to use only wrought iron scrap, and pickers are employed to carefully exclude all pieces of cast iron and steel; for if any of these materials get into the bundles the result will be too much carbon, which will cause the iron to be harsh and brittle, instead of malleable and tough. The best wrought iron for purposes where great toughness is required comes from Sweden, but is commonly known to the trade as “Norway iron.” It is very tough, because it is free from carbon and other impurities. The ore from which it is made is the finest iron ore known, and for this reason is used for making the finest grades of tool steel. No scrap iron is used in making Swedish iron.