Mechanical Performance Analysis And Forming Process Optimizationof Cold-drawnpearlitic Wires

In this paper，cold drawn steel wire was selected as the research object. In order toimprove the comprehensive mechanical properties of the wire, the mechanical property,residual stress and drawing process of the wire has been researched. The main researchcontents are as follows：(1) Based on a series of basic experiments and XRD residual stress detectionexperiments,a comprehensive analysis of the mechanical property and residual stresswith different drawing process has been performed. Then a conclusion was drawn thataxial residual stress is the main factor affecting the performance of the wire.(2) A finite element model of wire multi-pass cold drawing process has beenestablished in the paper, and the finite element model was verified by the residual stresstest results. Then through a series of FEM analysis, the wire metal flow and deformationfeature is summarized. Also the distribution of axial, circumferential and radial residualstress has been analyzed.(3) Based on the simulation results of wire multi-pass cold drawing, an index(strain MSE θ) was proposed which is used to evaluate the deformation uniformity ofthe wire. An analysis of axial residual stress distribution and strain MSE θ with differentwire drawing process has been carried out. After studied the residual stress distributionof various passes while the wire experienced eight passes drawing,it is found that axialresidual stress of the surface and center is increased with the drawing passes increases.(4) Combined the finite element simulation with orthogonal experimental design,the study has been carried out to optimize the six significant drawing factors (mold halfcone angle α, sizing zone length l, the compression ratio r, drawing speed v, frictioncoefficient μ and backpull stress). Then the sensitivity of each drawing parameters to σzand θ has been determined.(5)A hybrid optimization method was applied in present work．Orthogonalexperimental design and BP neural network were combined together to build a modelwhich describes the relationship between surface axial residual stress and each drawingfactors correctly. The wire drawing process was optimized by genetic algorithmcombined with BP network model which has been constructed, to decrease the axialresidual stress of wire surface. Through the process of optimization，the optimaldrawing process was obtained, that is, α=4, l=2mm, r=5%, v=2200mm/s, μ=0.13, bt=130MPa.After the verified by simulation, the axial residual stress of the wiresurface has been decreased41%, and the hybrid optimized effect is fully perfect. Itimproves the overall mechanical properties of steel significantly. Apparently, there is acertain reference to develop similar wire drawing process.