PRODUCTION OF SEAMLESS METAL PIPE AND BILLET FOR SEAMLESS METALLIC PIPE

摘要

PURPOSE:To enable the rolling of a larger sized material and high alloy material with increasing the rolling capacity by eliminating the peak electric power to generate at the piercing completing time of a squeeze rolling by subjecting the end part of the bottom side of a billet to a diameter reducing work over the proper length in advance. CONSTITUTION:The diameter reducing part A of taper shape which is made to make the diameter reduction quantity so larger gradually as to approach the bottom end face is formed over the adequate length of the bottom part of a billet. A step-like diameter reducing part B may be formed as well. In this case, the step pat is apt to remain as a flaw after the completion of the final rolling if the diameter reduction per step be >=5mm. The above worked billet is rolled with piercing so that the diameter reduction parts A, B become at the completion side of the piercing. Not only the increase in rolling capacity but also the improvement in productivity and miniaturization of a motor are enabled because of the peak electric power caused at the piercing completion time being able to be eliminated by rolling like this.