| Quenching tempering refers to dual heat treatment based on quenching and high temperature tempering. It’s aimed to ensure good comprehensive mechanical property of workpieces. Quenched and tempered steel is divided into two categories, carbon quenched/tempered steel and alloy quenched/tempered steel. Carbon content is strictly controlled no matter carbon steel or alloy steel. In case carbon is too high, workpieces after quenched and tempered have high strength but toughness is not enough. On the other hand, toughness can be increased but without enough strength in time of too low carbon content. To ensure good comprehensive mechanical property of quenched/tempered workpieces, carbon content is usually controlled within 0.30~0.50%. In time of quenching and tempering, the entire section of workpieces requires complete quenching to make workpieces form micro-structure mainly consisting of fine needle quenching martensite and form micro-structure mainly containing average tempering sorbite through high temperature tempering. It is impossible for small factories to conduct metallographic analysis for every furnace, and only test hardness as a general rule. That is to say, the hardness after quenching must reach the quenching hardness of the material. |
