To obtain a welded steel pipe of a high quality in its welded portion, having a good welded portion, and a right bead cutting is made possible by measuring a hoop edge displacement in front of the least stage squeeze rolling and making an adjustment of roll positions, roll gaps or a shoe plate position and the like so as to make the displacement the smallest.
The steel pipe 11 is manufactured with a tin sheet hoop 10. The displacement of the hoop edge just in front of No.2 squeeze rolls 2, which is the last stage of the squeeze rolling, is detected by a lever type contact displacement meter 3 with an accuracy of 0.01 mm or below. By making an adjustment of positions and the like of No.1-2 squeeze rolls 1, 2 or a fin pass roll 4 and the like, the displacement of the hoop edge is made to be the smallest. When manufacturing the steel pipe 11 with a sheet thickness of 1 mm or less, a cutting bite position in a longitudinal direction of the steel pipe 11 to cut an outer face welding bead is made to match the inner face roller position of the steel pipe 11. Bead cutting is conducted by supporting the outer face bite from the inner face of the steel pipe 11.
OGURI HITOHISA
KANNOU SHIYUUICHI
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