Numerical Simulation Of Cold Drawn Q345 Seamless Tube And Tooling Optimization

In the production of tube cold drawing,the fixed short mandrel drawing technology is one of the most important ways.The reasonableness of the design of die geometry is directly related to the quality of the tube after drawing.Cold-drawn dies applied in this paper are different from the traditional dies.The working area is combination of the straight line and arc,which changes the deformation behavior of the tube,so the cold-drawing process is simulated by the finite element technique.In this paper,the final tube is made of Q345 steel whose outer diameter(OD)and inner diameter(ID)were equal to 95 mm and 79 mm respectively,with a size of OD 88.9 × ID 76.2 mm.Tension tests of steel Q345 were carried out under different strain rates.The fitting parameters for the J-C material constitutive model were performed through two different ways,indicating that the result of the Levenberg-Marquarat algorithm coincides with the experimental datas quite well and has a good extrapolation capacity.By simulating tension tests,the critical value of ductile fracture criterion damage was determined.In the stable deformation stage,equivalent stress of the tube reaches a maximum 865 MPa in the fillet area between the short mandrel and the external die.The equivalent strain is unevenly distributed along the direction of the wall thickness and reaches a maximum value in the middle layer.After cold drawing,the axial residual stress is tensile near the inner surface and compressive near the outer surface.The maximum damage in the wall thickness is 0.19,which is less than the critical value.In the actual production,the entrance arc area and fillet area of the dies always suffer the most serious wear,which is also seen in the silmulation result.Finally,this phenomenon is explained from the view of interface pressure and the relative flow velocity.After selecting arange of the die structural parameters,it is deeply analyzedhow the parameters of the die half angle,bearing length,fillet radius,transition zone length,entrance arc radius influence the drawing force,maximum wearing depth,damage distribution andaxial residual stress.By comparing all indexes mentioned above,structure parameters of the new type of die determined by the orthogonal experiment method.After drawing with the new die,the drawing force decreases by 10%.The maximum wearing depth reduces by 3%,the axial residual stress reduced by 14%.The damage value decreases from 0.19 to 0.15,which presents homogeneous distribution along the wall thickness.