| Low alloy high-strength wear-resistant steel is widely used in the field of construction machinery due to its high hardness,good toughness and weldability.At present,the high strength wear-resistant steel produced in China still has some problems,such as poor impact toughness at low temperature and unstable mechanical properties.By increasing hardness,the wear resistance of wear-resistant steel can be greatly increased,but it also brings many negative effects,such as decreasing toughness and shortening service life of steel.In this paper,the intercritical quenching-tempering process is used to heat treat the NM500 wear-resistant steel produced by a domestic factory,and the evolution law of the microstructure and property of the experimental steel under different process parameters is studied,so as to ensure the hardness of the experimental steel and improve its toughness.The main research contents and conclusions are as follows:(1)The effects of quenching temperature and holding time in the two-phase zone on the microstructure and mechanical properties of the NM500wear-resistant steel were investigated,and the results showed that during the quenching temperature increases from 820℃to 880℃,the ferrite gradually decreased and the martensite increased,and when the quenching temperature was 880℃,the microstructure was almost all martensite;When the quenching temperature is 870℃and the holding time is 36 min,the hardness is 508 HV,and the impact work at-40℃is 37.4 J for the dual-phase steel.(2)The evolution law of microstructure and mechanical properties of the NM500 wear-resistant steel during the tempering process of complete quenching and intercritical quenching was studied.The results show that the toughness and low temperature tempering stability of the wear-resistant steel can be significantly improved by adopting intercritical quenching-tempering process.At a tempering temperature of 200℃,the microstructure of the experimental steel contains high density dislocated lath martensite,?transition carbides,a small amount of ferrite and residual austenite.The hardness of the experimental steel reaches 503 HV and the impact energy is 49 J at-40℃,which is 23 J higher compared with complete quenching-tempering.(3)The wear resistance of the NM500 wear-resistant steel with different heat treatment parameters was studied under the conditions of friction and wear.The results show that the wear rate of the experimental steel using the complete quenching-tempering process is 3.36 mm~3/N·m at a tempering temperature of 200℃,and the wear rate of the intercritical quenching-tempering process was 1.96 mm~3/N·m,and the wear resistance was improved.At this time,the wear mechanism of the experimental steel using the intercritical quenching-tempering process is mainly furrows. |
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