Effect of Heat Treatment Process on Microstructure and Properties of New Type Cold Work Die Steel SDC90

The microstructure,hardness and impact property of a new type cold work die steel SDC90,compared with Cr12MoV steel,were studied by using optical microscopy,Rockwell hardness tester and impact test machine for determining the optimum heat treatment process.The results show that ledeburite and carbides in the SDC90 steel were finer and distributed more uniformly than those in Cr12MoV steel.After quenching at 1 040 ℃ and tempering at 210 ℃,the hardness of SDC90 steel was equal to that of Cr12MoV steel,while the impact energy of the SDC90 steel was almost twice as high as that of Cr12MoV steel.After quenching at 1 080 ℃ and tempering at 540 ℃,the hardness and impact energy of the SDC90 steel were both higher than those of Cr12MoV steel.The service life of the steel was prolonged due to good combination of the high hardness,strength and toughness.