Deformation features of sheet metal (0.23 percent carbon steel) that the seam is welded using a high-frequency electric resistance welding machine and a pair of squeeze rolls in a mill to produce a circular welded pipe (51.3mm in external diameter, 5.0mm wall thickness) are discussed with reference to experimental measurements and results calculated using the rigid-plastic finite-element method. The results are as follows. Both the V-convergence angle, that is, the apex angle of the V-shaped seam formed at the entry of a pair of squeeze rolls and the inclination angles of the metal flow lines directed outward or inward in the heat-affected zone adjacent to the welded seam increase with an increase in both the upset imposed by a pair of squeeze rolls and the flange diameter of the rolls. The maximum value of the inclination angle is found on the metal flow line close to the outer surface of the heat-affected zone. This maximum inclination angle can be reduced significantly by making the welding temperature uniform in the wall thickness direction.
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