Application effect of cryogenic process
1. Effect of different cryogenic treatment processes on retained austenite in w6cr5mo4v2co steel (volume percent)
In the process of cryogenic treatment, a large amount of retained austenite transforms into martensite, especially the supersaturated metastable martensite will decrease the supersaturation during the process from – 196 ° C to room temperature, and the Ultra-fine Carbides with the size of only 20-60a are precipitated, which can reduce the lattice distortion of martensite and reduce the micro stress The dislocation movement can be hindered during the deformation, thus strengthening the matrix structure. At the same time, the precipitation of ultra-fine carbide particles evenly distributed on the martensite matrix weakens the catalytic effect of grain boundary. The refinement of matrix structure not only weakens the segregation degree of impurity elements at the grain boundary, but also plays a role in strengthening the grain boundary, thus improving the performance of high-speed steel, and significantly improving the hardness, impact toughness and wear resistance. If the hardness is increased from 60HRC to 62-63hrc, the die resistance increases by 30% – 40%.
It can be seen that the relative wear resistance of the die increases by 40% after cryogenic treatment. After prolonging the cryogenic treatment time, the relative wear resistance of the die increases with little change in hardness.
An example is given
- Punch: the high-speed steel punch of automobile factory can only be used for 100000 times without cryogenic treatment. However, the service life can be increased to 1.3 million times by using liquid nitrogen after – 196 ° C × 4H cryogenic treatment and tempering at 400 ℃
- Stamping die: production and application results show that the output of cryogenic treatment is increased by more than two times
- Cold stamping die for silicon steel sheet: in order to reduce the brittleness and internal stress of the die after cryogenic treatment, the combination of cryogenic treatment and moderate temperature tempering can improve the anti-destructive property and other comprehensive properties of the die. The grinding life of the die is increased by more than 3 times, which is stable at 51-70000 punches. After cryogenic or ultra cryogenic treatment of precision measuring tools, dimensional stability, wear resistance has been significantly improved.