Evaluation of ssaw steel pipe welding quality, first look inside and outside weld reinforcement and shape control how well the weld line is structured flow. Weld reinforcement tall and not too smooth transition, the weld toe stress concentration coefficient large against SCC unfavorable. In addition, the external weld reinforcement tall, will give the tube Chan Kee rot job increases does the cost increase; inner welding than tall, then the pipeline medium frictional resistance, also big energy pipeline. Therefore, in the production of submerged arc welded pipes, it must be controlled inner and outer weld than high. High weld reinforcement API 5L standard provides only a minimum standard and marine oil and gas pipelines and pipe are in control of the weld reinforcement 2.5mm or less.

Stress concentration butt joint weld reinforcement is mainly caused. It welds high more serious, but the strength of welded joints decreases. Flatten after welding reinforcement, as long as no less than the base material, reduce stress concentration, sometimes it can increase the strength of welded joints. Corner radius weld the smaller, the greater the degree of stress concentration; on the contrary, the degree of stress concentration is smaller. Therefore, the submerged arc weld requirements: First, Gaoyao small; the second is to smooth over the weld, so turn radius R as the value increases.

Spiral pipe seam weld joints are the butt of stress if you do not control the weld reinforcement and corner radius, the weld toe is large, so that the service pipe in this process, especially in corrosive media, prone to stress corrosion cracking in the weld toe. Weld forming and welding process will inevitably produce residual stress, thus forming the tube, after welding to eliminate the residual stress. Expanding to eliminate the residual stress, but it is difficult to completely eliminate the residual stress, residual stress at the weld toe, it is impossible to eliminate. To prevent stress corrosion cracking in the weld toe, which requires good control of molding, welding residual stress, especially the residual stress at the weld toe.

Such as the use in anticorrosion epoxy glass cloth anti-corrosion, external weld reinforcement tall, will not easily weld toe pressure prison. At the same time the higher the seam should be more thicker coating, due to standard coating thickness is outside the weld vertex for the reference calculation, which increased the cost of preservation. SSAW steel pipe in water pressure expanding, by expanding the size of the lumen and steel consistent with the left and right portions of the outer mold 2 will wrap the pipe, so the weld reinforcement is too large, when expanding weld shear stress to bear on the large, 2 side seam prone to the "small straight edge" phenomenon. But experience has shown that when the outer weld reinforcement controlled at about 2mm, does not occur when the water pressure expanding "small straight edge" phenomenon, the tubular unaffected.

This is because the outer weld Gao Yu, the shear stress of welded joints are exposed to small. As long as thisshear stress in the elastic deformation range, unloading springback after transplanting, the pipe will be restitution. Conveying the inner surface of spiral submerged arc coating done if not embalmed, its inner weld than tall, the frictional resistance of the transmission medium is large, whereby energy transfer lines will increase.