Tempering is an important step in the heat treatment of metals, mainly used to improve the toughness and stability of workpieces after quenching. The following is the detailed information of tempering:

Purpose
Eliminate internal stress: After quenching, large internal stress will be generated inside the workpiece, and tempering can effectively reduce these stresses.
Improve toughness: The hardness of the quenched metal is usually very high, but the toughness is poor. Tempering can improve toughness and reduce the risk of brittle fracture.
Adjust hardness: By controlling the tempering temperature, the hardness of the workpiece can be adjusted to achieve the desired performance.

Tempering process
Heating: Heat the quenched workpiece to a certain temperature, usually between 150°C and 700°C, and the specific temperature is selected according to the required hardness and toughness.
Maintain temperature: Maintain at a set temperature for a period of time to make the metal structure undergo a corresponding phase change.
Cooling: Usually cool naturally in the air to help the metal structure stabilize.

Tempering temperature and effect
Low-temperature tempering (150°C to 250°C): Mainly used to improve toughness, suitable for workpieces that require higher toughness.
Medium temperature tempering (300°C to 450°C): used to balance hardness and toughness, commonly used in mechanical parts.
High temperature tempering (500°C to 700°C): suitable for reducing hardness to increase plasticity, suitable for workpieces for certain special purposes.

Application
Tempering is widely used in the manufacture of parts that need to withstand impact and fatigue, such as gears, bearings, tools, etc., to ensure that they have good performance and long service life during use.