Alloy steel grades are specified when a hard wear resisting surface is required. However, because of the alloying elements after heat treatment, superior mechanical properties are achieved. The choice of steel will depend on the ruling section and the properties required for the component. Typical applications include gears, cams rollers, transmission components and other highly stressed parts.
For increased surface hardness, many of the specifications are suitable for induction hardening. Typical specifications � BS 970, 605M36, 708M40, 817M40, European Standard EN 100830-1 41Cr4, 42CrMo4, 34CrNiMo6. Specifications include: American A1S1 4140 4340.
Steels in this group usually contain two or more of the alloying elements nickel, molybdenum, vanadium. Bars are supplied in the softened condition. After machining, the components can be hardened and tempered to the required mechanical properties, or supplied in the final heat treated condition where the components can be put into service without further heat treatment. Direct hardening alloy steels are used for applications where high strength and resistance to shock is an important requirement.