Treatment method for improving strength of 20CrMnMo steel

Abstract

The invention discloses a treatment method for improving strength of 20CrMnMo steel. The treatment method comprises the following steps: 1, putting 20CrMnMo steel workpieces which are subjected to carburizing and quenching and are cooled to the room temperature into low-temperature equipment, wherein certain gaps are formed among the steel workpieces; 2, powering on the refrigeration system of the low-temperature equipment, precooling at minus 40+ / -5 DEG C, keeping the temperature, and setting the temperature keeping time according to sizes of the steel workpieces; 3, cooling the steel workpieces to minus 230 DEG C to minus 100 DEG C at a velocity of 5-20 DEG C / minute, and keeping the temperature for 6-48 hours; 4, powering off the refrigeration system of the low-temperature equipment, naturally increasing the temperature of the steel workpieces, and taking out the steel workpieces when the temperature is increased to minus 45 DEG C or greater, and cooling to the room temperature. The treatment method is simple and convenient to operate, low in cost and free of waste emission or environment pollution, the strength, the hardness and the wearing resistance of the 20CrMnMo steel can be effectively improved, and the service life of the 20CrMnMo steel can be prolonged.

Description

technical field [0001] The invention relates to the field of metal heat treatment, in particular to a treatment method for improving the strength of 20CrMnMo steel. Background technique [0002] 20CrMnMo steel is widely used, and the requirements for its mechanical properties are getting higher and higher. The existing treatment method of 20CrMnMo steel is quenching after carburizing, and then tempering at low temperature, so that the steel parts show higher strength, hardness and wear resistance. After quenching, the steel parts will retain a certain amount of retained austenite, which is an unstable phase and will transform into martensite in the subsequent processing or service process, affecting the dimensional stability of the workpiece. The instability of austenite is prone to volume changes caused by structural transformation, resulting in metal fragmentation. Moreover, there are many physical properties, especially thermal properties and magnetic properties. [0003...

AI Technical Summary

Problems solved by technology

[0002] 20CrMnMo steel is widely used, and the requirements for its mechanical properties are getting higher and higher. The existing treatment method of 20CrMnMo steel is quenching after carburizing, and then tempering at low temperature, so that the steel parts show higher strength, hardness and wear resistance. After quenching, the steel parts will retain a certain amount of retained austenite, which is an unstable phase and will transform into martensite in the subsequent processing or service process, affecting the dimensional stability of the workpiece. The instability of austenite is prone to volume changes caused by structural transformation, resulting in metal fragmentation. Moreover, there are many physical properties, especially thermal properties and magnetic properties.

However, the current heat treatment processes have certain limitations. Process 1 only reduces the residual austenite through cold treatment.

Process 2 performs a low-temperature tempering after quenching to reduce the residual stress of the material, and then performs cryogenic treatment to achieve the above purpose. However, for 20CrMnMo steel, the low-temperature tempering after quenching produces relatively stable retained austenite , the subsequent cryogenic treatment cannot significantly reduce the amount of retained austenite, and the corresponding increase in hardness is also very small, so the effect of cryogenic treatment is not obvious