To study the optimum heat treatment process of 51CrV4 spring steel for high-speed trains,the microstructure and mechanical property changes of the steel under quenching temperatures ranging from 840-900 ℃ and tempering temperatures from 380-520 ℃ were analyzed using Optical Microscope(OM),Field Emission Scanning Electron Microscopy(FESEM),universal tensile and the rotating bending fatigue testing machine.The criteria for selecting the best performance of the spring steel of journal box were discussed to determine the suitable heat treatment process.The results show that with the increase of quenching temperature,the austenite grains of 51CrV4 gradually grow larger,the cementite dissolves more completely into the austenite,less blocky ferrites and undissolved granular cementites are remained,which result in the increase of tensile and fatigue strength,and the decrease of toughness and plasticity.With an increase in tempering temperature,the transformation from martensite to tempered troosite becomes more complete,and the carbide precipitate grows from needle-like to rod-like or granular shapes,solution strengthening and precipitation strengthening become weaker,which contributes to a decrease in strength and an increase in toughness and plasticity.Considering that the 51CrV4 journal box spring still has a higher failure rate and lower impact toughness,a reasonable strength-toughness matching should be achieved for 51CrV4 steel.Therefore,the optimum heat treatment process ranges for obtaining better comprehensive performances are quenching at 900 ℃ followed by tempering at 460-480 ℃,quenching at 880 ℃ followed by tempering at 460 ℃.The tensile and yield strength are 1505-1551 MPa and 1389-1430 MPa,respectively,and the impact toughness is 14.7-16.7 J.
关键词
热处理工艺/51CrV4钢/轴箱弹簧/组织性能/弹簧失效
Key words
Heat treatment process/51CrV4/Journal box spring/Microstructure and properties/Spring failure
维普
万方数据