Manganese steel

Mangalloy, also called manganese steel or Hadfield steel, is a steel alloy containing an average of around 13% manganese. Mangalloy is known for its high impact strength and resistance to abrasion once in its work-hardened state.

Mangalloy is made by alloying steel, containing 0.8 to 1.25% carbon, with 11 to 15% manganese. Mangalloy is a unique non-magnetic steel with extreme anti-wear properties. The material is very resistant to abrasion and will achieve up to three times its surface hardness during conditions of impact, without any increase in brittleness which is usually associated with hardness. This allows mangalloy to retain its toughness.

Most steels contain 0.15 to 0.8% manganese. High strength alloys often contain 1 to 1.8% manganese. At about 1.5% manganese content, the steel becomes brittle, and this trait increases until about 4 to 5% manganese content is reached. At this point, the steel will pulverize at the strike of a hammer. Further increase in the manganese content will increase both hardness and ductility. At around 10% manganese content the steel will remain in its austenite form at room temperature if cooled correctly. Both hardness and ductility reach their highest points around 12%, depending on other alloying agents. The primary of these alloying agents is carbon, because the addition of manganese to low-carbon steel has little effect, but increases dramatically with increasing carbon content. The original Hadfield steel contained about 1.0% carbon. Other alloying agents may include metals like nickel and chromium; added most often to austenitic steels as an austenite stabilizer; molybdenum and vanadium; used in non-austenitic steels as a ferrite stabilizer; or even non-metallic elements such as silicon.

Mangalloy has fair yield strength but very high tensile strength, typically anywhere between 350 and 900 megapascals (MPa), which rises rapidly as it work hardens. Unlike other forms of steel, when stretched to the breaking point, the material does not "neck down" (get smaller at the weakest point) and then tear apart. Instead, the metal necks and work hardens, increasing the tensile strength to very high levels, sometimes as high as 2000 MPa. This causes the adjacent material to neck down, harden, and this continues until the entire piece is much longer and thinner. The typical elongation can be anywhere from 18 to 65%, depending on both the exact composition of the alloy and prior heat-treatments. Alloys with manganese contents ranging from 12 to 30% are able to resist the brittle effects of cold, sometimes to temperatures in the range of −196 °F (−127 °C).

...
Wikipedia