Manganese Steel
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.