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 semi-formed square steel tube before hot working at reduced heating cost and reduced equipment cost. SOLUTION: A steel plate 1 is formed and butt-welded to manufacture a semi-formed square steel tube 5. The semi-formed square steel tube 5 is entirely heated by a first heating means 31 close to A1transformation point, each corner part 6 is partially heated by a second heating means 61 close to A3transformation point, and the heated semi-formed square steel tube 5 is hot-worked by a forming means 71 to the normal dimensions and shape. By entirely heating each corner part by the first heating means close to A1transformation point and partially heating each corner part by the second heating means close to A3transformation point required for corner hot working, the heating cost before hot working of the semi-formed square steel tube can be reduced more than that of a method for entirely heating the semi-formed square steel tube close to A3transformation point. COPYRIGHT: (C)2004,JPO&NCIPI