Alloy Structural Steels General Classification

Alloy structural steel is generally divided into quenched and tempered structural steel and surface hardened structural steels.

Quenched and tempered structural steel, the carbon content of such steel is generally about 0.25% ~ 0.55%, for the structural section of a given cross-section size, during the quenched and tempered, if along the cross-section quenching, the mechanical properties are good, if quenching is impermeable, there are free microstructure of the ferrite, the toughness decreased. For the tempering brittle tendency of steel such as manganese steel, chrome steel, nickel chrome steel, tempering should be fast cooling.

Surface hardened structural steel, for the manufacture of hard wear-resistant surface of the heart and flexible parts, such as gears, shafts and so on. In order to make parts of the heart of high toughness, carbon content in steel should be low, generally 0.12 ~ 0.25%, as well as the right amount of alloying elements to ensure proper hardenability. Carburizing or carbonitriding steel, after 850 ~ 950 ℃ carburizing or carbonitriding, quenching and tempering at low temperature (about 200 ℃) state. Nitriding steel by nitriding (480 ~ 580 ℃), it can be used directly, no longer quenched and tempered.