is an alloy of iron which can be forged without any further treatment. The limit of forgeability or malleability lies at approximately 2% C (as a rule at 1.7% C). In the binary iron-carbon system, all alloys with contents of up to about 2% C are considered as steels, whereas cast iron, tempered cast iron, hard cast iron and raw iron are not. There are a large number of trade and manufacturing designa- tions for steel, some of the better-known types of which are given below: Austenitic steel, machine steel, strip steel, construction steel, stainless steel, case- hardened steel, cast steel, spring steel, profile steel, cold-rolled steel, LD steel, alloyed steel, magnetic steel, non-rust steel, tempered steel, heat-resistant steel and tooling steel.