Intermediate heat treatment
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I would like to ask the experts: for 15CrMoR material with a thickness of 55 mm, the drawing requires uniform preheating before welding, stress-relief heat treatment to be carried out in between, as well as hydrogen removal treatment. When should the intermediate heat treatment here be carried out?
Reply to 1# xlm010633: Hydrogen elimination treatment should be carried out immediately after welding. Our factory’s process involves a temperature of 300–350 degrees Celsius for 2 hours, followed by holding the material at that temperature before cooling it slowly; stress-relief heat treatment is also performed after welding
Our factory controls things in the same way; it’s just that this time the drawings specify intermediate heat treatment. I would like to know when this intermediate heat treatment should be carried out, and also where I can find relevant information on this
Hydrogen removal treatment is carried out immediately after welding. Our factory’s process involves a temperature of 300–350 degrees Celsius for 2 hours, followed by slow cooling in still air. Stress-relief heat treatment is also applied after welding, or H! can be used as well
Reply to 3# xlm010633: To be precise, this topic is covered in the chapter on low-alloy high-strength steels in the training materials for pressure vessel design engineers; you can try to find those materials!
For 15CrMoR with a thickness of 55 mm, I believe that degassing at 300–350 degrees for 2 hours is sufficient; there’s no need to carry out stress relief in between. If stress relief is required, it should be done by putting the material into the furnace right after welding, or after degassing following welding, and then heating it to over 600 degrees to relieve stress – this constitutes intermediate stress relief. 630 degrees is a suitable temperature for this purpose. After the processing is complete, final post-weld heat treatment is necessary, and this is the most important step; the temperature for this treatment is usually 690 degrees, with the holding time determined based on the thickness of the plate and the specific conditions of each manufacturing facility.
The thickness of the 15CrMoR material is 55 mm; the drawings require uniform preheating before welding, stress-relief heat treatment to be carried out in between, and hydrogen removal treatment as well. When should the intermediate heat treatment here be carried out? In my opinion, the key is to ensure proper control of the interpass temperature. If the weld is 2 to 3 meters long and there are no preheating measures on the back side of the weld, it’s difficult to maintain the interpass temperature required by the welding process. If it is possible to attach an electric heating plate to the back of the weld, it will be easy to meet your requirements. What you call intermediate heat treatment, I think, is about controlling the interlayer temperature of each layer. As soon as welding begins, it has to be done. Carry out dehydrogenation treatment promptly after welding is completed.