The tempering process is a heat treatment process in which the quenched workpiece is reheated to an appropriate temperature below the lower critical temperature and cooled to room temperature in air, water, oil, and other media after holding for a period of time.
The purpose of tempering :(1) eliminate the residual stress of the workpiece during quenching to prevent deformation and cracking;(2) Adjust the hardness, strength, plasticity, and toughness of the workpiece to meet the performance requirements;(3) Stabilize the structure and size to ensure the accuracy;(4) Improve and improve machining performance.
Tempering classification:
● Low-temperature tempering
Refers to the tempering of the workpiece at 150~250℃.
Objective: To maintain high hardness and wear resistance of quenched workpiece and reduce quenching residual stress and brittleness
Tempered martensite is the tissue obtained by tempering martensite at low temperatures.
(Acicular martensite)
Application: cutting tools, measuring tools, molds, rolling bearings, carburizing and surface quenching parts, etc.
● Moderate heat
Refers to the tempering of the workpiece between 350 ~ 500℃.
Objective: To obtain high elasticity and yield point, appropriate toughness. The tempering trochtite is obtained after tempering, which means that the ferrite matrix formed by tempering martensite is distributed in the complex phase structure of extremely fine spherical carbide (or cementite).
(Trostenite)
Application of tempering process: spring, forging dies, impact tool, etc.
● High-temperature tempering
Refers to the workpiece tempering above 500℃.
Objective: To obtain better comprehensive mechanical properties of strength, plasticity, and toughness.
After tempering, the tempered Soxhlet is obtained, which means that the ferrite matrix formed by tempering Martensite is distributed in the complex phase structure of fine spherical carbide (including cementite).
(Sostenite)
Application of tempering process: Widely used in all kinds of important structural parts, such as connecting rod, bolt, gear and shaft parts, etc.
