Some issues regarding chromium-molybdenum steel plates and welding
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I was working on a project recently that involved chromium-molybdenum steel, and the technical specifications weren’t written very clearly; there were some parts that were hard to understand； 1. It’s normal for the heads of chromomoly steel to have weld seams, right? The technical agreement states that welded seams are not allowed to be used in hot forming as well as in normalizing and tempering heat treatment processes ； (That’s what was said; it seems to mean that welding is not possible, probably because the size of the equipment itself is small, less than DN1200, and this is why such a requirement was set.) 2. Regarding welds: A senior colleague said that normalizing has a significant impact on the performance of welds. Could you explain why? 3. For example, in the case of joining end caps, if there is no subsequent normalizing and tempering in the welding process (that is, no heat treatment to restore the part to its original condition), then if welding test pieces are available, can heat treatment be carried out in the same furnace, thereby eliminating the need for a separate welding process?
1. Those with a DN1200 diameter do not require splicing. It should be considered that small diameters cannot be joined together ； 2. The main purpose of normalizing is to refine the microstructure, improve the properties of the steel, and obtain a microstructure in an equilibrium state. Compared to the annealing process, the main difference in normalizing is that the cooling rate is slightly faster, which results in a shorter production cycle for normalizing heat treatment. Therefore, when annealing and normalizing can both meet the performance requirements of the parts, normalizing should be preferred whenever possible. 3. If the spliced end cap has welds and requires normalizing, then the welding procedure qualification shall be one that takes normalizing into account. If normalizing is not required. Welding evaluation is essentially normal heat treatment evaluation
Learn from the views upstairs! ! ! ! !
The first question: if the head is very large, it will definitely need to be joined; joining parts with a smaller diameter is done, of course, to save material. This is related to the width of the steel plates purchased. If it is a horizontal equipment with a head diameter of 1200 MM and the steel plate’s width is also 1200 MM, then welding will definitely be necessary. Also, don’t you have any drawings for your equipment? Conduct the acceptance in accordance with the technical requirements specified in the drawings. Equipment manufacturing is definitely carried out in accordance with the design technical requirements.
The main issue is that the welding process qualification has been unsuccessful, as there are no suitable welding materials available.