Abstract: In order to develop woodworking circular saw blade, band saw, spring and other hardware tools with high properties and long life, the Ni element with mass fraction of 0.2% and 0.4% was added to the 75Cr1 steel, respectively. The effect of different Ni content on mechanical properties and microstructure of the 75Cr1 steel as hot rolled and heat treated was studied by mechanical property test, microstructure analysis and heat treatment test. The results show that within the range of 0%-0.4% Ni addition, the strength and hardness of the hot rolled 75Cr1 steel can be reduced, but the plasticity improved, the higher its content is, the more significant the effect is, however, the impact property is not obvious change. Ni content has little effect on quenching hardness, when it reaches 0.4%, the hardness of the steel shows a trend of decreasing, but the plasticity after tempering is obviously improved; after tempering, the strength and hardness of the steel are reduced, but the impact absorbed energy is improved. The higher the Ni content, the more obvious the improvement effect. On the aspect of microstructure, Ni can refine the size and lamellar spacing of the hot rolled 75Cr1 steel pearlite colonies, promote the spheroidization of lamellar pearlite, and refine the microstructure after quenching and tempering. Considering economy and mechanical properties, the optimal addition of Ni in the 75Cr1 steel is 0.2%.

Key words: Ni alloying, high carbon tool steel, 75Cr1 steel, mechanical properties, microstructure