Steel. The addition of a small quantity of carbon greatly increases the hardness and tenacity ot iron, and converts it into steel. The amount of carbon to be added, should be just that which will produce the maximum of hardness and toughness, without rendering it brittle; ordinary steel contains about 1 per cent, of carbon; hard steel 1.6 to 1.7 per cent. The percentage of carbon in English steel is estimated by Berthier to be 1.87. It melts at about 2500° Fahr.

3274. To Convert Iron into Steel

3274. To Convert Iron into Steel. This is usually done by the process of cementation, producing what is termed blistered steel. At the bottom of a trough about 2 feet square and 14 feet long, usually formed of fire clay, is placed a layer, about 2 inches thick, of a cement composed of 10 parts charcoal and 1 part ashes and common salt; upon this is laid a tier of thin iron bars about 1/2 inch apart; between and over them, a layer of cement is spread, then a second row of bars, and so on, alternately, until the trough is nearly full; lastly a layer of cement covered with moist sand and a close cover of fire-tiles, so as to exclude the air. The trough is exposed to the heat of a coal fire, until a full red heat, about 2000° Fahr., is obtained and kept up steadily for about 7 days. A hole is left in the end of the trough, to allow of a bar being drawn out for examination. "When a bar, on being withdrawn and broken, has acquired a crystalline texture, the metal is allowed to cool down gradually, some days being allowed for this, and the charge, when cool, withdrawn from the trough. The bars will be found covered with large blisters, hence the name of the process, and increased about 1/150 in weight. The steel is now sufficiently good for files and coarser tools, but for finer instruments, several varieties of finer steel are required. (Makins).

3275. To Make Shear-Steel

3275.    To Make Shear-Steel. This is produced by cutting up bars of blistered steel, into lengths of 30 inches, and binding them in bundles of 8 or 9 by a ring of steel, a rod being fixed for a handle. These are brought to a welding heat, and welded together under a tilt hammer. The binding ring is then removed; and, after reheating, the mass is forged solid, and extended into a bar. In cases where this operation is repeated, the steel is called double-shear steel. {Makins.)

3276. To Make Cast-Steel

3276.    To Make Cast-Steel. Cast-steel is the best variety for all fine cutting tools. This is a mixture of scraps of different varieties of blistered steel, collected together in a good refractory clay crucible; upon this a cover is luted, and it is exposed to an intense heat in a blast furnace for 3 or 4 hours. The contents are then run into moulds. After being subjected to the blows of a tilt-hammer, the cast steel is ready for use. (Makins).

3277. Steel Made from Iron Scraps

3277.    Steel Made from Iron Scraps. Take iron scraps in small pieces, put 40 pounds in a crucible, with 8 ounces charcoal, and 4 ounces black oxide of manganese; expose the whole l1/2 hours to a high heat, and run into moulds.