Based on many years of heat treatment experience, for non-quenched and tempered steel parts, the cooling method after forging will directly affect the final performance of the product. In the actual test process, several cooling methods such as natural air cooling, slow cooling in the box and controlled cooling are usually used. Comparing the metallographic structure and mechanical properties of parts under different methods, it was found that under the rapid cooling condition of natural air cooling, due to the faster cooling rate before phase transformation, the amount of ferrite in the surface structure is smaller and the ferrite network is thinner. , which is beneficial to improving the high-frequency quenching and mechanical properties of parts: However, in order to eliminate the internal stress of the parts and reduce the deformation during the processing of the parts, the cooling rate should not be too fast. Therefore, a more reasonable cooling method for non-quenched and tempered steel parts after being heated and forged by a medium frequency induction annealing machine should be:
(1) Use rapid cooling before phase transformation, and the cooling rate can be controlled at 40°C~80°C per minute to obtain finer ferrite grains.
(2) Slow cooling is used during the phase change process and after the phase change is completed to eliminate the residual stress inside the forging. It can also eliminate or reduce the uneven hardness, uniformize the hardness, and facilitate cold working. This is the use of medium frequency for non-quenched and tempered steel. During the forging production process of the induction heating machine, the purpose and effect to be achieved is to control the post-forging cooling.
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GS-ZP-1200
