Welding process qualification: Before starting welding, in accordance with the international general standards and relevant national and enterprise standards, in accordance with the welding process specifications that have been formulated in detail, the actual pipe section test piece welding is carried out under the site supervision of the project supervision, and then the process evaluation of the test piece .
Welding process qualification test items include: B-ray detection, ultrasonic detection, tensile strength test, grooved hammer break test, guided bending test, low temperature impact toughness test, macrostructure inspection of welded joints, hardness determination, C6D resistance performance test, etc. If the test result is unqualified, the welding process should be modified or the welder should be replaced until the test results of the weldment meet the design requirements. Records of welding procedure qualification test results and assessment reports shall be archived.
Welding procedure specification: The welding procedure specification should be based on the qualified welding procedure assessment report, combined with welding construction experience and actual welding conditions. The welding procedure specification should indicate: steel pipe steel grade and material range, pipe diameter and wall thickness range, joint form and size, filler metal model and specifications, welding method, welding position, welding direction, electrical characteristics, process parameters, counterpart, Weld bead cleaning and grinding, manual welding and semi-automatic welding, pre-weld pre-weld and post-weld heat treatment, inter-pass temperature, shielding gas and flow rate, equipment requirements, welding environment requirements, inspection methods and qualification standards, etc.
Attention should be paid when choosing welding materials:
(1) Non-low-hydrogen electrode can be used for root welding and hot welding, which is conducive to obtaining a good weld back formation and improving welding efficiency;
(2) Filler welding and cover welding should use low-hydrogen electrode, which can anneal and dehydrogenate root welding and hot welding. However, non-low-hydrogen type of flux-cored wire should not be used to ensure good toughness of the weld metal.
When the basic elements of the welding procedure specification are changed, the welding procedure shall be re-qualified.
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