Suppression of Bending Phenomenon of Steel Tube in Diameter Reduction by Cold Press

Abstract

A new die design is proposed for the suppression of the bending phenomenon that occurs in the cold-reduction process of the outside diameter of steel tube using a die. Numerical investigation by axi-symmetric elastic-plastic finite element analysis (FEA) was carried out in order to determine appropriate die geometry for the suppression of the bending phenomenon. The proposed die geometry suppresses the undershooting phenomenon by which the outside diameter of a worked tube is smaller than the inside diameter of the die, and ensures the contact of the tube outer surface to the bearing portion of the die to suppress the bending phenomenon. The key to the new die design for suppressing the undershooting phenomenon is the installation of a finishing zone with a small die angle where a small reduction of diameter is given to the tube. For suppressing the bending phenomenon, longer bearing length is necessary in addition to the suppression of undershooting. In order to examine the validity of the calculated result by FEA, a laboratory experiment was carried out on a steel tube with 0.45 per cent mass carbon content.