Description

Tempering is a heat treatment process that heats quenched metal products or parts to a certain temperature, and then cools them in a certain way after holding for a certain period of time. Tempering is an operation performed immediately after quenching, and is usually the last heat treatment of the workpiece. A process, so the joint process of quenching and tempering is called final treatment.

The Role Of Tempering Is To:

① Improve the stability of the structure, so that the workpiece will no longer undergo tissue transformation during use, so that the geometric size and performance of the workpiece will remain stable.

② Eliminate internal stress in order to improve the performance of the workpiece and stabilize the geometric dimensions of the workpiece.

③ Adjust the mechanical properties of steel to meet the requirements of use.

The reason why tempering has these effects is that when the temperature rises, the activity of atoms increases, and the atoms of iron, carbon and other alloying elements in steel can diffuse quickly to realize the rearrangement of atoms, thus making them unstable. The unbalanced organization gradually transforms into a stable balanced organization. The relief of internal stress is also related to the decrease in metal strength as the temperature increases.

Generally, when steel is tempered, the hardness and strength decrease, and the plasticity increases. The higher the tempering temperature, the greater the change in these mechanical properties. Some alloy steels with high content of alloying elements will precipitate some fine-grained metal compounds when tempered in a certain temperature range, which will increase the strength and hardness. This phenomenon is called secondary hardening.