Quality Evaluation of Spiral Seam Cold Bending Pipe of X70 Steel

The properties of X70 spiral seam cold bending pipe with 1 219 mm diameter were researched. The results showed that the ellipticity change of cold bending pipe end was comparatively obvious,and the wall thickness reduction was appeared on outer side than inner side of cold bending pipe. The effect of bending process of pipe on the structure and property of welding seam was not obvious. The base material on outer side by aging treatment exhibited higher strength and hardness than the base material on straight part of cold bending pipe. The extensibility and impact toughness of cold bending pipe was a litter lower than that of original pipe.