Effect of normalizing cooling rate on microstructure and properties of 20CrNiMo steel

The effects of different normalizing cooling rates on the microstructure and properties of 20CrNiMo were studied by means of scanning electron microscope,metallographic microscope and hardness tester.The results show that pearlite and ferrite are mainly present in the furnace cooled 20CrNiMo structure,and pearlite and ferrite are mainly present in the air cooled 20CrNiMo structure,and a small amount of martensite is also found.In addition to pearlite and ferrite,a certain amount of martensite was also found in the air-cooled + air-cooled 20CrNiMo structure.With the increase of normalizing cooling rate,martensitic transformation is easily induced.In addition it is found,with the increase of normalizing cooling rate,the Rockwell hardness of 20CrNiMo is basically stable,and the microhardness increases in some areas,which is consistent with the microstructure change trend.