Effect of Quenching and Tempering Temprature on Microstructure and Hardness of Hot Working Die Steel 4Cr5MoSiV

Microstructure and hardness of 4Cr5MoSiV steel quenching and tempering have been observed and analysed by metallographic microscope and the hardness tester. The result show that, carbides of 1 040℃, 1 060℃ quenching were not completely dissolved in austenite, martensite microstructure becomed thicker increases with the quenching temperature; Hardness increased first and then decreased with temperature raised, maximumvalue was 56.5 HRC at 1 100℃; Grain size decreased gradually with the increased of temperature. The solubility of carbides in autenite had a great effect on the hardness of martensite transformation. Tempering was at the range of 490℃-560℃ after 1050℃ and 1 100℃ quenching, obtained different microstructure, and many types of carbides were precipitated in the tempering microstructure, mainly including M₂₃C₆ and M₆C, tempering hardness wasobviously improved by those carbides of microstructure.