Mangalloy
At around 10% manganese content the steel will remain in its austenite form at room temperature if cooled correctly.
Unlike carbon steel, mangalloy softens rather than hardens when rapidly cooled, restoring the ductility from a work-hardened state.
[12] Alexandre Pourcel, of the French Terre-Noire Cie., was able by the 1878 World's Fair in Paris to produce ferro-manganese with as much as 80 per cent of manganese and only a small amount of carbon.
B. Karsten [14] noted that adding fairly large amounts of manganese to iron would increase its hardness without affecting its malleability and toughness,[15] but the mix was not homogeneous and the results of the experiment were not considered to be reliable.
[3] Sulfur combines with iron to form a sulfide that has a lower melting point than steel, causing weak spots, which prevented hot rolling.
Manganese is usually added to most modern steels in small amounts because of its powerful ability to remove impurities.
[19][13] Hadfield had been studying the results of others who experimented with mixing various elements with steel, such as Benjamin Huntsman and A.H. Allen.
Hadfield began by mixing ferro-manganese with crucible steel and silicon, producing an alloy of 7.45% manganese, but the material was unsatisfactory for his purposes.
It looked dull and soft, with a submetallic luster similar in appearance to lead, yet sheared the teeth off his file.
[13] 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.
[13] 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.
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.
Hadfield originally marketed his steel for use in railways and trams, but quickly began producing it for everything from saw plates to safes.
[13] 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.
