METHOD AND FACILITY FOR MANUFACTURING SQUARE STEEL TUBE

摘要

PROBLEM TO BE SOLVED: To provide a square steel tube manufacturing method for heating a round steel tube before hot working at reduced heating cost and reduced equipment cost. SOLUTION: A round steel tube 1 is entirely heated by a first heating means 11 close to A1transformation point, and each corner part formation corresponding part 1A is partially heated at a plurality of positions in the circumferential direction by a second heating means 41 close to A3transformation point. The heated round steel tube 1 is hot-worked by a forming means 51 into a square steel tube having a plurality of corner parts with the normal dimensions and shape. By entirely heating the tube by the first heating means close to A1transformation point and partially heating each corner part formation corresponding part by the second heating means close to A3transformation point required for corner hot working, the heating cost before hot working of the round steel tube can be reduced more than that of a method for entirely heating the round steel tube close to A3transformation point. The first heating means can have a configuration capable of withstanding the temperature close to A1transformation point, and the heating cost before hot working of the round steel tube can be reduced, the frequency of maintenance can be reduced, and the maintenance cost is also reduced. COPYRIGHT: (C)2004,JPO&NCIPI