Effect Of Quenching And Partitioning On Structure And Properties Of 22 SiMnCrNi2MoA Steel

In order to achieve energy saving and environmental protection,people have conducted a lot of research on the lightweight of automobiles.In addition to automobiles,many products such as power line steel fittings also need to be lightweight.The effective means to achieve weight reduction is to use advanced high-strength steel and increase the strong plastic product of the material.The typical process method to increase the strong plastic product is the quenching-partitioning(Q&P)process.This paper mainly studies the microstructure and properties of 22 SiMnCrNi2MoA steel with different quenching-partitioning process parameters.The mechanical properties of the test steel are studied by DNS 100 universal testing machine,NI-300 impact testing machine and HR-150A Rockwell hardness tester.The microstructure of the test steel is studied by GQ-300Leica inverted metallographic microscope,Philips XL-30ESEM environment scanning electron microscope and polycrystalline X-ray diffractometer.The experimental results show that;(1)The final structure after quenching and partitioning is mainly a mixed structure of tempered martensite and retained austenite.When the partitioning temperature is 380?,a ferrite structure appears.During the partitioning process,the addition of alloying elements Si and Mn cannot completely inhibit the precipitation of carbides,and the tempering of martensite and the partitioning of carbon in martensite to retained austenite are performed simultaneously.(2)When the quenching temperature is 120-220?,as the quenching temperature increases,the tensile strength and yield strength decrease continuously,and the decrease is not very significant,while the elongation first increases and then decreases.When the quenching temperature is 180?,The retained austenite content is the most,and the elongation reaches the maximum.The short quenching holding time has little effect on the performance of the test steel.The diffusion rate of carbon at low temperature is slower than that at high temperature,so the quenching holding time has little change in the volume fraction of initial martensite and initial austenite.The influence on the organization and mechanical properties is negligible.(3)The partitioning temperature has a major effect on the structure and performance.The partitioning temperature mainly affects the diffusion rate of carbon atoms.The higher the temperature,the faster the diffusion rate.As the partitioning temperature increases,the tensile strength and yield strength Slowly decreasing,the hardness change law is consistent with the strength,and the elongation first increases and then decreases.When the partitioning temperature is 320?,the elongation reaches the maximum value of 15.76%,and the toughness is also the best.When the partitioning temperature is 320?,the comprehensive mechanical properties of the test steel reach the best.When the partitioning temperature is 380?,the structure has changed significantly and transformed into tempered troostite.The influence of single factor on performance and structure is studied by orthogonal experiment.Obtained,when the partitioning time is lOmin,the overall performance of the test steel reaches the best.With the partitioning,the actual result is that the partitioning temperature is higher,the shorter the time,the better the performance,the lower the partitioning temperature,the longer the partitioning,the better the performance.(4)Finally,the best process for obtaining the experimental results is that the quenching temperature is 180?,the partitioning temperature is 320?,and the partitioning holding time is 120s,the strength product of the test steel reaches the maximum.