Abstract:
At present, 65Si2CrV valve spring steel produced by Chinese steel plants mainly faces two problems: poor inclusion control and insufficient strength and toughness. In this experiment, Ce + Nb treatment method was used to solve them. The results indicated that the content of T.O (total oxygen in steel), S, P, and As element decreased gradually with the increasing of rare earth Ce, indicating that rare earth Ce has a good effect on deep purification of molten steel. The size of pearlite clusters in 0#-3# experimental steel decreased gradually, and the interlayer spacing of pearlite showed a trend of first decreasing and then increasing, with the addition of rare earth Ce and Nb. The tempering temperature has a significant impact on the mechanical properties of experimental steel. Specifically, the strength of the valve spring steel decreased gradually, while the plasticity of steel showed an increasing trend, as the tempering temperature increases. The types and compositions of alloying elements also have a significant impact on the microstructure and mechanical properties of experimental steel. An appropriate amount of Nb and Ce can effectively refine the microstructure of experimental steel and improve its strength and plasticity. However, it should be noted that too much Ce will deteriorate the performance of steel. In this experiment, 0.021wt.% Nb + 0.042wt.% Ce can make the best results. The yield strength of experimental steel was approximately equal to the combined contribution of fine grain strengthening, solid solution strengthening, precipitation strengthening, and dislocation strengthening. The comprehensive effect of these four strengthening mechanisms determines the overall yield strength variation of 0#-3# experimental steel.
