Study On Phase Transformation Process And Microstructure Evolution Of 20MnSi(V)rebar

20MnSi(V)rebar is widely used in construction engineering as a structural steel with excellent comprehensive properties.In order to meet the requirements of energy saving and consumption reduction,R&D high-performance energy-saving engineering construction steel is imminent.In this paper,the microstructure and mechanical properties of 20 MnSi rebar are optimized by using TMCP,which can provide experimental and theoretical basis for the research and application of 20 MnSi rebar.The phase transformation and microstructural analysis of 20 MnSi rebar were carried out by using DIL805A/D differential dilatometer to heat,cool and load stress,and the TMCP experiment of 20MnSi(V)steel was carried out on the Gleeble-1500 thermal simulator with different deformation temperature and deformation,combined with metallographic observation,TEM analysis and performance testing methods,demonstrate the feasibility of improving 20 MnSi steel’s performance by the stress loading,TMCP and adding micro alloy technology to further optimize the organization.It was found that:The austenite start temperature AC1 and end temperature of AC3 are all increased with increasing heating rate.Austenite formation time is significantly reduced,and the peak transformation rate is significantly increased;Based on the result of different cooling rates,the continuous cooling transformation diagram(CCT curve)was analyzed and plotted;The experimental results show that the loading stress promotes the transformation of undercooled austenite in 20 MnSi steel,increases the phase transition temperature of ferrite and pearlite,refines the microstructure,increases the dislocation density,and improves the relative content of pearlite in the microstructure,and at a relatively low temperature load stress will make the above phenomenon more obvious;Different deformation temperature and deformation affect the microstructure and properties of 20MnSi(V)steel,with the decrease of deformation temperature,the deformation resistance of 20MnSi(V)steel increases,the microstructure is refined and the dislocation density increases,due to the strengthening of VC precipitation,20 MnSiV steel microstructure is more uniform refinement than 20 MnSi steel under the same condition;The microstructure of 20MnSi(V)steel is more refined and dislocations increase with the increase of the deformation amount under the same deformation temperature,and the strain induced precipitation behavior of 20 MnSiV steel under the large deformation amount makes the precipitation of more VC,thus makes the structure more compact.