Deformation analysis of surface flaws in stainless steel wire drawing

Recently, the high surface quality of drawn wires and rods has been required for the manufacture of automobiles and machines. The surface flaw of a drawn wire has a significant influence on the quality of product. Using three-dimensional finite element analysis (FEA), this study investigates growth of surface defects due to wire drawing when these on wire, wire breaks due to surface defects are common problems in wire drawing. The drawing of a wire rod and poor handling at the time of conveyance are cited as causes of a surface cracks. The authors carried out multi-pass drawing of the stainless steel wire with an artificial crack, and investigated growth and disappearance of a crack from both sides by experiments and FEA. A crack with a small angle becomes smaller under repeated drawing. However, in actuality, the flaw remains inside the wire because of the development of an overlap, and thus it is difficult to completely remove the flaw. When the crack angle is small, the crack side surfaces are pushed toward each other and the crack becomes an overlap defect. In contrast, when the crack angle is large, the bottom of the crack rises, and the crack is repaired satisfactorily. Furthermore, the scratch shape and the drawing conditions were varied, and the deformation state of a crack was clarified. Moreover, the influence which the surface treatment of peeling has on a wire rod, was considered. Superior wires without flaws could be obtained by removing the flaws before drawing and by multi-pass drawing.