Research On Effect Of Rolling And Heat Treatment Process For Microstructure And Properties Of 40cr Steel

40Cr steel is an structural alloy steel which is mainly used to manufacture shaft parts in the mechanical manufacturing industry.It has good comprehensive mechanical properties and has been currently widely used in China’s machinery manufacturing industry,mainly used to manufacture shaft parts.However,because of the reticular ferrite structure,it is easy to be break when used.In this paper,the high temperature deformation,continuous cooling transformation,rolling process and heat treatment process of 40Cr steel is researched,and the transformation of structure,the change of ferrite content and the change of properties is analyzed in this paper.The main work is as follows:(1)The effect of deformation temperature and deformation rate on the prior austenitic morphology and deformation resistance of the experimental steel are investigated by a single pass compression test.Analyze the stress-strain curve and austenite grain growrth law.(2)The continuous cooling transformation curves of experimental steel under static and dynamic conditions are established using methods of expansion and metallographic test.The effects of the deformed and undeformed continuous cooling transition curves is compared.The eutectoid ferrite phase transition shifts the ferrite and pearlite transition regions to the left.(3)The effects of different rolling process parameters on the microstructure and hardness are studied using a thermal simulation experiment machine.The results show that during single pass deformation,the ferrite in the structure is mostly thin strips,and there is a reticular ferrite structure;two passes of deformation and heat preservation can increase the ferrite content,while refining the grains can make ferrite The volume is evenly distributed,which improves the organization and performance.(4)The effects of different quenching temperature,tempering temperature and tempering time on the micro structure and mechanical properties of the experimental steel are studied.The experimental results show that a suitable long-term high temperature tempering can simultaneously increase the strength and toughness of the experimental steel and reduce the hardness;Sub-temperature quenching can improve the properties of the experimental steel and retain the ferrite in the original structure.The morphology of the structure before quenching also has a great impact on the properties after heat treatment.(5)The simulation of the production site has carried out the optimal control rolling and cooling and heat treatment experiments on the experimental steel to observe the structure and measure the mechanical properties.The results show that there is no reticular ferrite in the structure after the controlled rolling and cooling experiment.The mechanical properties are improved and the grains are fine after heat treatment.