| 摘要 |
PURPOSE:To prevent a tube breaking and to improve the accuracy of dimension by obtaining a critical elongation of a blank rolled stock previously, regulating the ratio between an elongation on each stand and the critical value to constant and setting a diameter reducing ratio of the blank pipe. CONSTITUTION:A tension test of the blank rolled stock is performed previously by Grieble high temp. test, etc., to obtain a critical erosion. To maintain the ratio of the elongation of each rolling stand of a continuous reducing rolling mill and the critical elongation value obtained previously to be constant, the diameter reducing ratio of the blank pipe of each stand are set. The reducing rolling of the seamless steel pipe are performed by the zero-setting of a thickness reducing ratio of the blank pipe. Though a stretch coefficient of each stand becomes larger at later stand, because the elongation ratio for the critical value is maintained the same, the tube breaking of the product is prevented and its accuracy of dimension is improved. |
