The quenching of steel heat treatment

The quenching of vacuum heat treatment is the method of quenching the workpiece into the quenching medium for a few seconds and then cooling it in the air for a certain time. This operation can be repeated multiple times. If the retention time is correct and repeated operation, the workpiece surface and center can achieve the required hardness. This quenching method is beneficial to prevent quenching and cracking.

This is because the martensite of the surface of the workpiece is tempered by the internal heat of the workpiece, which reduces the internal stress due to the internal heat of the workpiece. However, it is important to note that when the workpiece stays in the air, the austenite cannot be decomposed in order to continue to change to martensite when the subsequent quenching medium is very cold.

The large pressure die made of steel is designed to be hardened by the whole. The hardness requires HRC38~ 43. Due to the complex shape of the workpiece, the porous, multi-groove and thickness are very uneven, so it can be easily quenched. Therefore, using the method of the interrupted quenching: 850 ℃ heating, cooling, to 810 ~ 830 ℃, quenching into the water, keep 2 ~ 3 s, air cooling 1 ~ 1.5 s, repeatedly for three times, finally in 350 ℃ tempering 1 h, hardness meets the requirements as a result, the quenching crack.