Influences of Residual Elements Cr,Ni and Cu on Microstructure and Properties of SPHC Strip

The influences of residual elements Cr,Ni and Cu content on the microstructures and properties of SPHC hot rolled strip steel was studied by means of tensile testing machine,hardness tester,metallo-graphic microscope and SEM.The results show that the structure of SPHC hot rolled strip steel is composed of ferrite and pearlite.The range of grain size of SPHC hot rolled strip is 19.05~19.32 μm.The hardness of SPHC strip increases firstly and then decreases with increasing residual elements content,.The maximum difference in tensile strength is 15 MPa,the maximum difference in yield strength is 45 MPa and the maxi-mum difference in elongation is 7.5%.The relation between strain hardening index and yield ratio shows a negative linear correlation.It indicates the increase of microcontent residual elements improves material strain hardening index.When residual elements Cr and Cu appear small amount and uniform precipitation at grain boundary,its effect of weakening the mechanical performance is low,and the resulted steel shows a good mechanical property.