Effect of Vanadium and Strontium Addition on Thermal Fatigue Properties of 5CrNiMo Hot Work Die Steel

5 CrNiMo hot work die steel samples were produced with various amounts of vanadium（V）and strontium（Sr） as well as different adding modes of vanadium,thermal fatigue properties of the samples were tested and analyzed.The results show that both the amount of V and Sr and the adding mode of V have an effect on the thermal fatigue properties of the samples. Comparing with the sample without V and Sr,the thermal fatigue crack grade of the sample with 0.5% of V and 0.5% of Sr changes from 7 to 2,and the thermal fatigue properties have an obvious improvement. The thermal fatigue crack grade of the sample by adding pure vanadium metal changes from 3 to 2 with the thermal fatigue properties improved,in comparison to the sample by adding FeV40 alloy.The optimum addition amount for both of V and Sr is 0.5%,and it’s better to add pure vanadium metal into the 5 CrNiMo hot work die steel.