| 摘要 |
A method of producing a welded square steel tube from a single steel plate by preparing the opposite side edges of the plate for welding, bending the plate at the portions corresponding to the four corners of the square tube, fitting together the opposed edges of the bent plate, subjecting the edges to tack welding, welding together the opposed edges from inside and outside the tubular bent plate and straightening the resulting tube. These steps are conducted in succession while the steel plate is being conveyed in its longitudinal direction. An apparatus for practicing this method is also disclosed.
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