| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a square steel pipe the accuracy of the corner Rs value of which can be improved by a small modification of existing facilities without newly changing the diameter of a forming roll. SOLUTION: In the method of manufacturing the square steel pipe, when a round steel pipe is formed into a square cross section by passing through a plurality of stages of forming stands having upper and lower large-diameter rolls which are driven and small-diameter side rolls which are rotated by following the rotation of the large-diameter rolls, the round pipe is passed through at least one stage of the forming stand in which the small-diameter side rolls are offset to the inlet side of the steel pipe in the axial direction than the upper and lower large-diameter rolls. Because the upper and lower rolls and side rolls are brought into contact with the round steel pipe to be formed almost simultaneously, the steel pipe is deformed almost simultaneously in upward, downward, right and left directions and the amount of deformation is equalized. Thus the corner Rs values are almost equalized. COPYRIGHT: (C)2005,JPO&NCIPI
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