Alloy steel that are contain expensive alloys to produce a desired physical property or characteristic, and are often sold only by the kilogram or tons. They are generally very hard, wear resistant, tough, nonreactive to local overheating, and frequently engineered to particular service requirements. They must be dimensionally stable during hardening and tempering. They contain strong carbide formers such as silicon, manganese, molybdenum, vanadium, and chromium in different combinations, and often cobalt or nickel to improve high-temperature performance.
Alloy steel is often subdivided into two groups: high alloy steels and low alloy steels. The difference between the two is defined
somewhat arbitrarily. However, most agree that any steel that is alloyed with more than eight percent of its weight being other
elements beside iron and carbon, is high alloy steel. Low alloy steels are slightly more common.
