Manganese steel was discovered and highly developed by Robert Hadfield of Sheffield, England, along about 1882. His 11 per cent to 14 per cent manganese steel with about 1 per cent of carbon has such great hardness that it cannot be drilled or cut with tools. In forgings and castings it is used for milling machinery for ore treatment; manganese steel rails inserted around sharp curves and for “frogs,” etc., under severe service conditions outlast ordinary steel rails three or four times; it goes into various rolls and crusher parts, steam and dredge shovels, grab buckets, sand pumps, gears, pinions, etc., which have to resist heavy wear. It is much used, too, as a material for burglar-proof safes. The alloy is far too hard to drill and too tough and strong to be broken. It is said that no manganese steel safe has ever been drilled or forcibly entered. In forming irregular shapes, manganese steel must be cast and finished by grinding but for ordinary bars and rails it can be rolled. In the “raw” condition it is quite brittle and extremely hard. Quenching from a cherry-red heat greatly toughens it and makes it ductile. Though now it can be dented by a hammer blow and marked with a file, it always is so tough that it cannot be machined with any tool. Ordinary annealing treatment has no softening effect on the alloy. Silicon Steels When alloyed in the steel in certain quantities, silicon gives desirable properties. Steels with from one to two per cent of silicon in the tempered condition are very tough. For this reason the leaves of automobile springs are often made from it. Steels with from 3 to 5 per cent of silicon are much used in electrical appliances because of their improved magnetic properties. Molybdenum Steels To a certain extent steels containing 3 or 4 per cent of the metal molybdenum, and 1 or 1½ per cent of carbon are used in the construction of permanent magnets. It is said that molybdenum is used in some modern guns, which longer resist the corrosive effect of the powder-gases because of it. A certain amount goes into the high-speed steels where it replaces part or all of the tungsten. Here, however, it has been a disappointment and the amount so used seems to be decreasing rather than increasing. Tungsten Steels Steels with about ½ per cent of each of carbon and tungsten are occasionally used for manufacture of springs, and with greater amounts, e.g., ¾ per cent of carbon and 5 or 7 per cent of tungsten, for permanent magnets for which they are claimed to be the best material known. The use of tungsten in the tool steels (other than the high-speed steels) is considerable. Nickel Steel