Research On Control Of Microstructure,Properties And Residual Stress Of Wear-resistant Steel Based On Quenching-partitioning And Cryogenic Treatment

The presence of residual stress restricts the use of strip steel with the application of the new generation of cooling technology with ultra-fast cooling as the core.In this regard,in this paper,ABAQUS software was used to simulate the distribution of temperature-structure-stress of wear-resistant steel during laminar cooling process,the evolution of residual stress of wear-resistant steel subjected to quenching partitioning and cryogenic treatment process.Moreover,the mechanism of quenching-partitioning and cryogenic treatment process on the microstructure,mechanical properties and residual stress of wear-resistant steel was investigated by means of the tensile test,impact test,wear resistance test and stress measurement by blind hole method,SEM,XRD,EBSD.And the main conclusions were drawn as follows:(1)The modeling results of temperature-structure-stress of wear-resistant steel in the laminar cooling process show that with the increase of initial temperature difference in the transverse direction of wear-resistance steel,the uniformity of temperature and the synchronization of phase transformation between the edge and the middle of wear-resistance steel are deteriorated,leading to a sharp increase in residual stress.(2)The microstructure of sample treated to quenching-partitioning and cryogenic treatment is composed of martensite/bainite,ferrite,retained austenite and fine carbides.With the increase of cryogenic time and cryogenic time,the matrix microstructure of wear-resistance steel is refined,which results in an excellent fit of strength-plasticity with an product of strength and elongation up to 17 GPa·%.(3)The quenching-partitioning and cryogenic process reduces the amount of unstable retained austenite,increases the boundary hindering the growth of crack,and improves toughness of wear-resistance steel.The impact toughness and hardness of sample treated by cryogenic treatment for 6 h achieved the best match,which results in an improvement by41.3% of wear resistance compared with the sample treated by quenching-partitioning process.(4)The quenching partitioning and cryogenic process significantly reduce the residual stress of wear-resistant steel,and the reduction of residual stress by increasing the number of cryogenic cycle is higher than that of increasing the cryogenic time.Multiple cryogenic cycle treatments lead to lattice shrinkage,resulting in an increase in the number of carbon atoms escaping.Therefore,the precipitation of substantial fine carbides during subsequent tempering process results in greater relaxation of the residual stress than other processes.Compared with the quenching-tempering and quenching-partitioning processes,the reduction rates of residual stress of sample subjected to quenching-partitioning combined with three-time cryogenic cycle treatment are 56.6% and47.2%,respectively.