Issues regarding the welding of 2520 duplex steel heat exchange tubes to Q345 carbon steel tube sheets
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According to relevant information, it is possible to perform dissimilar steel welding directly between the 2520 heat exchange tubes and the tube sheet (with a thickness of 250 mm), or it is also possible to first weld-on a layer of 309+347 to the tube sheet before carrying out the welding. Dear experts, which welding method is more reliable and controllable? The medium inside the pipe is propylene in gas phase at 100 degrees, while the outside of the pipe is exposed to industrial circulating water at 35 degrees. If there are other approaches, please advise. Thank you to all of you.
2520 is not a duplex steel, so there is no problem with directly welding it to carbon steel pipe plates. For very important occasions, stainless steel for tube sheet towers is definitely much better. . .
Although the original poster only specified the operating temperature and not the operating pressure, given the medium and operating temperature, there is no need to use a material like 2520; if its use is necessary, welding of dissimilar steels can be employed directly.
You mean 2205, right? 2520 is suitable for high-nickel stainless steel in high-temperature environments; welding 2205 duplex steel with carbon steel is no problem
For various heat exchangers, especially those with gas flowing inside the tubes, special attention must be paid to T2T welding； 1: There are entry and exit effects at T2T ； 2: Due to the inlet/outlet effect, cooling water forms a vapor chamber in the gap of the T2T shell side, and this cycle leads to scaling in the gaps, increased thermal resistance, and poor heat transfer. With unchanged inlet and outlet conditions, cracks will form in the shell-side gap of T2T, due to fatigue and high temperature ； The principle mentioned above can be applied to your welding ； 2205 is welded directly to the Q345R tube sheet; at this weld site, Cr and Ni are incorporated into the Q345R tube sheet, resulting in increased strength but reduced toughness, and an increased tendency to crack ； Transition welding can ensure that the T2T weld points avoid the aforementioned issues. Of course, strict welding discipline is also necessary; during transition welding, a low wire energy input and no movement are all essential. What is the entrance/exit effect? You can ask Baidu.