Effect Of Heat Treatment And Pulse Current On Microstructure And Properties Of 30CrMnSi Steel

30CrMnSi exhibits the properties of high strength and high toughness,which is often applied to manufacture high-speed and high-loaded key components,as well as widely used in aerospace,automobile and other industries.With the continuous upgrading of industrialization,automotive design and production enterprises have gradually improved the lightweight,cost and performance standards of automotive steel.However,high strength steel usually has large residual stress after forming,which is easy to cause springback and even cracking.It is urgent to explore a forming method to solve this problem.As a new forming method,electro-assisted forming（EAF）can improve the mechanical properties of materials through the effects of electroplasticity.Based on this,this study took30CrMnSi steel as the research object,explored the influence of heat treatment temperature and electric assisted forming on its mechanical properties and microstructure,and discussed the action mechanism of pulse current in the tensile forming of 30CrMnSi steel.The main research contents and results are as follows:The effects of quenching temperature and tempering temperature on the microstructure and mechanical properties of 30CrMnSi steel were studied.The results show that in the range of 800℃～880℃,the number and size of martensite in 30CrMnSi steel increase with the increase of quenching temperature,and the tensile strength and hardness both show an upward trend.When quenching at880℃,the tensile strength and hardness reach their peak values,which are 1773MPa and 49 HRC,respectively.The reason for this phenomenon is that the steel with high strength and hardnessγ-Cr_1.36Fe_0.52 phase.After low temperature tempering,30CrMnSi steel has the lowest wear amount and the best wear resistance.In this state,some carbon atoms in the steel precipitate and form（Fe,Cr）₇C₃ carbide with the alloy element Cr,while the steel is tempered at a higher temperature and the carbide is transformed into（Fe,Cr）₂₃C₆.Based on the pulse current assisted tensile test,the effects of current density,duty cycle and tensile rate on the microstructure and mechanical properties of30CrMnSi steel were analyzed,and the strengthening and toughening mechanism of pulse current was discussed.The results show that with the increase of current density and duty cycle,the tensile strength and elongation of 30CrMnSi steel increase first and then decrease.When the current density is 10 A/mm² and the duty cycle is 1%,the strong plastic product of 30CrMnSi steel reaches 33.3 GPa%.After the pulse current of 10 A/mm² and 20 A/mm² strength grade is applied,dense martensite zone appears in the metallographic phase of the gauge length section of30CrMnSi steel,and more dimples appear in the fracture morphology.When the current density and duty cycle are too large,the number of dark martensite decreases,the number of light areas increases,and the number of dimples decreases.The strength of 30CrMnSi steel is affected by Joule heating effect of current and crack arrest effect.The current increases dislocation mobility and improves the plasticity of steel.