Repair method for transversal cracks of welding seams of thick-wall submerged arc welded pipe

Abstract

The invention discloses a repair method for the transversal cracks of the welding seams of a thick-wall submerged arc welded pipe, comprising the following steps of: confirming defects, preheating before gouging, performing air gouging, grinding, performing MT (magnetic particle test), eliminating the residual liquids of PT (penetration flaw test), preheating before welding, welding, eliminating hydrogen after welding, and performing NDT (nondestructive test). By virtue of the repair method disclosed by the invention, the defects of the cracks in the welding seams or base metal can be completely removed after the lengths and positions of the defects of the cracks are determined. According to the invention, the preheating is performed in the initial stage of the air gouging, the operation method of the air gouging is proper, the range of the air gouging is 50 mm at the both ends of each crack, the both ends of each gouged groove are smoothly and flatly transited, and the included angle A between the transition surface and a vertical line is at least greater than 45 degrees, so that crater cracks are not easy to occur during the arc striking or arc stopping of the welding. In the repair method disclosed by the invention, thorough removal for the cracks is confirmed by virtue of magnetic particles, the preheating is adequately performed before the welding, the welding is rapidly performed in strict accordance with a small current, and heat input and welding bead widths are strictly controlled; a welding rod barrel is electrified, so that welding rods in the welding rod barrel can be really insulated, and a heat-insulating and slow-cooling measure is adopted after the welding is finished.

Description

technical field [0001] The invention belongs to the technical field of submerged arc welded pipe welding, and in particular relates to a method for repairing transverse cracks in weld seams of thick-walled submerged arc welded pipes. Background technique [0002] During the welding process of thick-walled submerged arc welded pipes, when the weld seam was scanned on site, it was found that there were similar transverse cracks between the second layer and the fourth layer of most of the completed welds, which were transverse or curved. more. Defects in the existing technology for reworked welds: no preheating during gouging, improper gouging operation method, too small gouging range, too large angles at both ends of the gouging, resulting in arc craters when welding starts or ends Cracks; it is not sure whether the cracks must be removed, there is no preheating before welding, or the preheating is not sufficient, the weld bead is too wide during the welding process, and the...

AI Technical Summary

Problems solved by technology

Defects in the existing technology for reworked welds: no preheating during gouging, improper gouging operation method, too small gouging range, too large angle at both ends of the gouging, resulting in arc craters when welding starts or ends Cracks; it is not sure whether the cracks must be removed, there is no preheating before welding, or the preheating is not sufficient, the weld bead is too wide during the welding process, and the heat input is too large; the welding rod barrel cannot be really insulated, and there is no insulation and slow cooling after welding, etc.

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