Experiments on and Finite Element Analyses of the Tilting of Fine Steel Wire in Roller Die Drawing

Roller die drawing is required for manufacturing low-formability materials such as high-carbon steels into fine wires with a diameter of 500 μm or less because of its characteristic lower friction than conventional die drawing. However, tilting, which is the inclination of the wire under the roll bite, often occurs in fine wires, which degrades their dimensional accuracy. Excessive tilting may generate wrinkling and overfill of the wire; thus, the design of the drawing setup of roller dies for reducing tilting is important from an industrial viewpoint. With the aim of designing a new setup for roller die drawing that can eliminate tilting; we carried out systematic experimental and analytical investigations. We first experimentally focused on the distance between adjacent rollers, and then theoretically focused on the area reduction ratio and roll-to-wire diameter ratio using the finite element method (FEM), taking the twisting moment as a representative parameter to evaluate the effect of different manufacturing conditions. It was found experimentally that there is a maximum threshold distance between adjacent rollers for preventing tilting. To draw a 200-μm-diameter wire without tilting, the roller distance should be set at no more than 8 mm, which leads to a more compact setup than the conventional one. Theoretical analysis revealed that a smaller area reduction ratio and a smaller roll-to-wire diameter ratio are required to reduce the tilting of the wire in roller die drawing.