Research On Fatigue Property Of 60Si2CrVAT Spring Steel

Using 60Si2CrVAT spring steel as testing material, the effect of heat treatments, surface states and carbides on the fatigue life were investigated by means of optical microscope, scaning electron microscope, X-ray diffraction, microhardness and fatigue test. Surface states included surface decarburizing, shot peening and inoxidzable coating.The results show that the tensile properties of isothermal salt bath process are lower than that of conventional quenched and tempered one when austenization temperatures were the same. Therefore the fatigue test only proceeds conventional processing and finds that the fatigue life of 510℃tempering is higher than that of 580℃when quenching at 860℃.The influence of practical decarburized depth, inoxidzable coating and shot peening are mainly studied the effect of surface states to fatigue property in this test. After quenching at 860℃and holding 40min, 80min, 160min, 320min, 640min oil cooling, surface topography can be observed. When the holding time is 40min and decarburization depth is 0.06mm, the fatigue cycle index can reach up to 1000000 without fatigue breaking. When the holding time is extended to 160min and the decarburization depth is 0.18mm, at this time fatigue life droved to assemble but low. This indicates that with prolonging the holding time, the decarburization depth is deepened and the fatigue life is reduced but assembles at the same heating-up temperature. When the decarburization reaches a certain depth, fatigue life is much stabilizer but lower. Compared with brushing coat and without brushing coat at 860℃quenching 580℃tempering, the influence of brushing coat is little to fatigue life. Shot peening can increase the fatigue life of spring steel at the same heat treatment. After the second shot peening, the fatigue life is decreased which instruct that shot peening can not be excessed or it will generate micro tear which is affected fatigue life.The influence regularity of carbide on fatigue life is that more undissolving carbide will reduce fatigue life of spring steel.