Simulation Study On The Effect Of Drawing Process On The Microstructure And Properties Of Pearlitic Steel Wire

Steel wire is widely used in industrial production and daily life in modern times.Cold drawing is one of the key processes in steel wire production,which induces diameter reduction and strengthening of steel wire.Therefore,drawing process greatly affects the performance of steel wire in service.Therefore,it is of great theoretical and practical value to study the effects of cold drawing process on the microstructure and properties of steel wire.In this paper,the influence of drawing process on the uneven distribution of stress and strain on the cross section of pearlitic steel wire and the mechanical response in the micro zone are studied by the combination of macroscopic finite element method and crystal plastic finite element method simulation.The main research contents and conclusions are as follows.(1)The finite element software Abaqus has been used to construct the multi-pass drawing models on the macro scale and the pearlite colony model on the micro scale,and the stress distribution and strain distribution and micro mechanical response of the steel wire have been studied.At the macro scale,a batch of multi-pass drawing models corresponding to 17 drawing processes have been established by Python script.It is found that the axial residual stress distribution on the cross section of the steel wire is"surface tension and internal pressure" and shows a variation of "s" type,the radial residual stress is "surface zero and internal pressure" and the circumferential residual stress is "surface tension and internal pressure".From the core to the surface of the wire,the axial tensile strain distribution increases first and then decreases,and reaches its maximum value at the sub-surface about 3/4R away from the core.The distribution of radial compressive strain is similar to that of axial strain,and the value is about half of the axial strain.The variation of circumferential strain is small.In addition,the strain path gradually becomes tortuous from the center to the surface.(2)With the same total reduction ratio,the total number of passes,the die angle and the reduction ratio allocation of each pass have great influences on the stress distribution and strain distribution of the steel wire.The range of axial strain and axial residual stress on the cross section increases with the increase of the total number of passes and the increase of the die angle.On the other hand,by adopting the process of decreasing partial reduction ratio gradually,the range of axial strain on the cross section decreases,and the wire with more balanced internal and external properties can be obtained.(3)At the microscopic scale,based on the rate-dependent crystal plastic finite element theory considering dislocation density evolution,a representative volume element model containing 256 pearlite colony has been established.Submodel method is used to introduce different boundary conditions of macro model to realize macromicro coupling simulation.It is found that when the strain path is not very different on the cross section of steel wire,the larger the strain is,the more severe the work hardening will be.When the strain path is different but the strain is the same,the more tortuous the strain path is,the more intense the work hardening is.Combining with the influences of inhomogeneous strain distribution and strain path,on the cross section of cold-drawn steel wire,the hardness of the subsurface is the highest.The mechanism of additional strengthening from tortuous strain path has been further explored at the single grain level.It is found that the complex stress state can drive more slip systems to operate,which leads to the increase of slip strain and the increase of immobile dislocation density,and finally realizes the additional work hardening effect.In addition,the strength of textures at different positions on the cross section and under different processes is compared and analyzed.It is found that large strain is beneficial to<110>silk texture generation,while tortuous strain path is not conducive to<110>silk texture generation.