Research On Strain Path Of Pearlitic Wire Under Large Deformation

With the development of automobile and tire lightweight,steel cord need to develop high-strength cold-drawn steel wire.Develop high-strength thin steel wire which may reduce the sawing and material loss in silicon and sapphire wafer cutting.However,the method of increasing the mechanical properties of steel wires by increasing the plastic strain amount has reached the bottleneck,and it is urgent to find other effective ways.In this paper,Abaqus finite element analysis software is used to simulate the multi-pass drawing process of steel wire.The purpose is to clarify the law of strain path in the process of cold drawing and to provide theoretical basis for studying the microstructure evolution and mechanical properties through strain path,to provide a new idea or method for the development of high strength steel wire by controlling strain evolution through strain path.In this paper,the concept and characterization method of strain path is analyzed firstly.And Schmitt factor calculated using the stress deviator is selected to express strain path.According to the production process of multi-pass cold drawing of pearlite wire and combining the characteristics of finite element software,the finite element model of multi-path drawing was established by using the technology of field variable transfer and mesh re-division.Aiming at the problem of large deformation and inhomogenous mechanical properties of the surface layer to the center,a large deformation material model was constructed and modified based on the experiments.It is found that the equivalent strain distributions of the passes are the same in the direction from the center to the surface,the equivalent strain value is smallest in the center but largest in the sub-surface.And the equivalent strain at the surface layer is the largest.After the end of 23 passes drawing,the maximum strain value would up to 4.360.The results show that the strain path maintains constant during drawing at center and surface of steel wires.The other area experiences a dramatic strain path change before the bearing zone.The strain path change of the sub-surface is the biggest.The influence of process parameters on the strain path is studied.It is found that the strain path change gets greater with the increase of the die angle.But with the increase of the reduction,the strain path change becomes smaller.The yielding stress at different radius of drawn pearlitic steel wires is tested.It is found that the distribution of yielding stress in the radial direction is inhomogenous.The wire surface has the highest stress.It reduces gradually with reducing radius and then increases.When the relative radius is 0.8,the yielding gets a peak.It reduces again with reducing radius.It mainly results from the different strain path experienced during wire drawing.