his file. It would not hold an edge as a cutting tool, yet could not be cut with saws nor machined on a lathe. It was non-magnetic despite containing over 80% iron, and had very high electrical resistance. Attempts to grind it simply glazed and polished the surface. Most striking, when heated and quenched, it behaved almost opposite to plain carbon-steel. After performing several hundred tests, he realized that they must be accurate, although the reason for the combination of hardness and toughness defied any explanation at the time. Hadfield wrote, "Is there any case similar to this among other alloys of iron, if the term alloy may be used? No metallurgical treatise refers to them... Possibly when the nature of the laws governing alloys is better understood, this will be found to be only one of other cases...". Hadfield's invention was the first alloy of steel to demonstrate considerable differences in properties compared to carbon steel. In the modern age, it is known that manganese inhibits the transformation of the malleable austenite phase into hard brittle martensite that takes place for normal steels when they are quenched in the hardening procedure. The austenite of Hadfield steels is thermodynamically unstable and will transform into martensite when subject to mechanical impact thus forming the hard surface layer. Hadfield patented his steel in 1883, but spent the next five years perfecting the mixture, so did not present it to the public until 1887. He finally settled on an alloy containing 12 to 14% manganese and 1.0% carbon, which was ductile enough to be indented but so hard it could not be cut. It became the first alloy steel to become commercially viable. Hadfield originally marketed his steel for use in railways and trams, but quickly began producing it for everything from saw plates to safes. Use Mangalloy has been used in the mining industry, cement mixers, rock crushers, railway switches and crossings, crawler treads for tractors and other high impact and abrasive environments. It is also used in high impact environments like inside a shot peening machine. These alloys are finding new uses as cryogenic steels, due to their high strength at very low temperatures. See also Ferromanganese, an ferroalloy with much higher manganese content (usually around 80%), not a steel but rather an ingredient used in making steels References Steel alloys Manganese compounds