Application Of Roller Die Drawing Technology In Preparation Of High Strength Steel Wire

To explore the feasibility of roller-die drawing technology in the preparation of high strength steel wire,Scanning electron microscopy(SEM),Transmission electron microscopy(TEM),Electron backscatter diffraction(EBSD),X-ray diffraction analysis(XRD),The differential scanning calorimeter(DSC)and mechanical properties testing methods were used to study the effects of two forming methods on microstructural deformation and mechanical properties of low carbon steel wire and high carbon steel wire.Effects of drawing methods on microstructural evolution and mechanical properties of low carbon steel wire were studied.The results show that when the drawing strain is 0.23,the strength of steel wire drawn in roller dies is 660 MPa,the strength of cold drawn steel wire is 621 MPa,and the strength of roller-die drawing wire is about 6% higher than that of cold drawn steel wire.while the drawing strain is 1.18,the strength of steel wire drawn in roller dies is 854 MPa,the strength of cold drawn steel wire is 898 MPa,the strength of roller-die drawing wire is about 5% lower than that of cold drawn steel wire.Under any strain,the plasticity of steel wire drawn in roller dies is better.Deformation behavior in the steel wire after roller-die drawing is more coordinated than that in cold drawn steel wire,specifically,smaller grain size and stronger <110> fiber texture are detected in the roller-die drawing wire.TEM shows that in the initial stage of deformation,a large number of sub-crystals are formed in the roller-die drawing wire,at the later stage of deformation,lower dislocation density in the roller-die drawing wire leads to weaker work hardening.The analysis of residual stress shows that residual tensile stress on the surface of the cold drawn steel wire is larger,after roller-die drawing,residual tensile stress on the surface of steel wire is smaller,and gradually changes to residual compressive stress with strains.Effects of drawing methods on microstructural evolution and mechanical properties of high carbon steel wire were investigated.The results show that when the drawing strain is 1.18,the strength of steel wire drawn in roller dies is 1583 MPa,the strength of cold drawn steel wire is1493 MPa,and the strength of roller-die drawing wire is about 6% higher than that of cold drawn steel wire.Deformation behavior in the steel wires after roller-die drawing is more coordinated than that in cold drawn steel wires,specifically,smaller grain size and stronger <110> fiber texture are detected in the roller-die drawing wire.During the process of drawing,the shearing stress generated by cold drawing is easy to cause fracture of cementite lamellae,and there is high density dislocationentanglement in the fracture zone.In the process of roller-die drawing,the cementite lamellae is slowly bent and deformed in order to reduce the shearing effect.Specifically,thinner lamellae and stronger work hardening effect are detected in steel wire drawn in roller dies.DSC shows when the drawing strain is 1.18,the exothermic peak appears between 403°C and 491°C in the roller-die drawing wire,while the exothermic peak appears between 381°C and 472°C in the cold drawn steel wire,which indicates that steel wire drawn in roller dies has better thermal stability and the deformation storage capacity is lower.The analysis of residual stress shows residual tensile stress is introduced on the surface of cold drawn steel wire,and the residual stress on the surface of steel wire drawn in roller dies gradually changes from tensile stress to compressive stress.