Discussion on the heat treatment of surfacing parts

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Regarding surfacing components such as flanges and tube sheets, is heat treatment required? First, let me share my thoughts: 1) Regarding the tube sheet, it goes without saying that heat treatment is necessary. The surfacing layer of the tube sheet, especially the transition layer, is subject to very high welding stresses. If heat treatment is not carried out, drilling holes in it later may result in numerous cracks in that transition layer. Therefore, the tube sheet must undergo heat treatment after surfacing, so as to eliminate these welding stresses, before any further machining can take place. 2) Regarding flanges (whose surfacing areas are usually the sealing surfaces and inner holes of the flanges), I believe there are two scenarios: ① If the medium used in the equipment is hazardous, overall heat treatment of the equipment is often required. In that case, no additional intermediate heat treatment is necessary during the flange surfacing process, as the overall heat treatment of the equipment later on will already eliminate the stresses resulting from the flange surfacing; therefore, there is no need for further intermediate heat treatment after the flange surfacing is completed. ②The equipment itself does not require overall heat treatment; the surfacing of flanges and the processing after welding do not suffer any impact if no intermediate stress-relief heat treatment is carried out, so it is possible to omit such treatment. Although heat treatment helps to relieve stresses and stabilize the equipment’s performance, it is not necessary to carry out the intermediate heat treatment for flange surfacing when this is not specified in the drawings or technical requirements. If such treatment is explicitly required, then it must be carried out according to the specifications given in the drawings. Additionally, I would like to ask everyone: is there any standard or specification that explicitly requires heat treatment after flange surfacing? 3) Here, I would like to ask everyone: how do various units operate? How does everyone understand this issue? Additionally, how is the timing for heat treatment after surfacing determined? (Is it done after welding the transition layer, or after welding the surface layer? What are the advantages and disadvantages of each approach, and what is the actual performance in practice?) )