Abstract
A square steel pipe is reshaped from a welded round pipe by roll forming. The effect of roll diameter on the cross-sectional size of the square steel pipe was investigated by experiment and three-dimensional finite element simulation. When the diameter of the top roll is larger than that of the side roll, the width of the cross section of the formed pipe is smaller than the height. To make the width and height equal, it is necessary to perform finishing forming in the last stage. When the diameter of the top roll is larger than that of the side roll, the width of a corner part of the formed pipe is larger than the height. The difference between the width and height of a corner part of a product is greater than that of a half-finished pipe. The difference becomes so large that the ratio of the diameter of the top roll to that of the side roll becomes large. The square steel pipe was formed by offsetting the small roll to the upstream side. The offset method is effective in making the width and height of a corner part equal.
