Post-weld heat treatment
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The drawings require overall stress-relief heat treatment for the equipment. The material of the cylinder is Q345R+S30403 (54+3), while the nozzles are made of S30403Ⅲ, DN80. The cylinder has now completed its overall heat treatment; stainless steel forged pipes are to be installed, and the weld joints are of different steel types. Is it possible to omit post-weld heat treatment for the fillet welds?
Isn’t it meant to be the whole thing? It should be done for everything, right?
I would like to ask: the classification of S30403 into grades II and III is specified in which standard?
See NB/T47010-2017
“”The drawings require overall stress-relief heat treatment for the equipment; it seems that your technical team does not understand the meaning of this requirement. It is not that stress-relief heat treatment cannot be applied to austenitic stainless steel welds – it depends on the design requirements regarding the susceptibility of austenitic stainless steel to intergranular corrosion. Generally, during the welding process evaluation for austenitic stainless steel, a test for intergranular corrosion is carried out after simulating stress-relief heat treatment (sensitization treatment), and the results show that the material meets the requirements regarding resistance to intergranular corrosion. If overall heat treatment is not to be applied to the stainless steel forged pipes as well, it is necessary first to obtain approval from the designers. Additionally, a detailed design is required for the structure of the joints formed by welding different types of steel. For example, before heat treatment, an 6 mm thick layer of austenitic stainless steel can be welded onto the edges of the carbon steel grooves; after heat treatment, the forged pipes can then be assembled. In this case, the subsequent stainless steel welds do not require post-weld heat treatment. Welding on carbon steel materials should be avoided immediately after stress-relief heat treatment.
First, it depends on whether the welding process evaluation you have chosen requires heat treatment; if not, it can be omitted. However, generally, Q345R material with a thickness of 54 mm is not subjected to such treatment, as the internal stresses are too high and this can lead to cracks. If your forged parts are to be welded to Q345R, the best approach is to follow the method mentioned on floor 7.
Heat treatment is definitely necessary to eliminate the overall internal stress. As for whether there are other issues with austenitic stainless steel during heat treatment, that is another question.