Precautions for quality inspection of steel pipe welds
Welding quality inspection refers to: using methods such as investigation, inspection, measurement, testing, and detection to compare welding quality with the use requirements of welded steel pipes, prevent continuous production of unqualified steel pipes, and avoid the occurrence of quality accidents. Under normal circumstances, post-weld inspection mainly ...
Welding quality inspection refers to: using methods such as investigation, inspection, measurement, testing, and detection to compare welding quality with the use requirements of welded steel pipes, prevent continuous production of unqualified steel pipes, and avoid the occurrence of quality accidents. Under normal circumstances, post-weld inspection mainly includes: actual welding records, weld appearance and dimensions, post-heat and post-weld heat treatment, steel pipe welding test plate, metallographic inspection and fracture inspection, non-destructive inspection, pressure test, density test, etc.
The quality inspection of steel pipe welds is usually divided into appearance inspection, non-destructive testing, and destructive testing of steel pipe welding test plates. The inspection items are determined according to the type of welding structure, working characteristics, and importance. In principle, the inspection methods and inspection scope of various types of welded structure steel pipe welds shall be in accordance with relevant national standards, manufacturing procedures, or the company's steel pipe welding technical conditions. The inspection procedure is specifically specified by the welding process specification.
For welded joints of certain structural materials, the inspection procedure of nondestructive testing of welds is a key link to ensure the quality of welds. For example, high-strength steel thick-walled joints with a yield strength of 460MPa often have a tendency to hydrogen-induced delayed cracking under certain working conditions. Therefore, it is stipulated that the nondestructive testing of welds must be carried out 48 hours after welding; for example, welded joints with a tendency to reheat cracking should be subjected to nondestructive testing of welds again after stress relief treatment of welds. The inspection procedure of welds is closely related to the welding process, and nondestructive testing methods and inspection procedures must be specified in the welding process specification.
For welded structures that require the strength of the joint to be equal to that of the parent material, such as boilers, pressure vessels, and pipelines, welded steel pipe welding test plates are usually specified to test the mechanical properties, chemical composition, metallographic structure and other properties of the joints. In fact, this is also a further verification of the welding process specification. Compared with the welding process assessment test plate, the welding conditions of the steel pipe welding test plate are closer to the actual welding production conditions. If all the inspection results are qualified, it means that the welding process is applicable, continues to be effective, and can be reused. In the large-scale production of welded structures, steel pipe welding test plate inspection failures also occur from time to time. At this time, a careful analysis should be conducted and the cause should be found out through corresponding tests. In addition to the misuse or misuse of structural materials and welding materials, the main problem is the welding process. If the test results prove that the welding process is indeed not well considered, the welding process specification should be modified.
