Post-weld heat treatment of stainless steel equipment
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I am a technician at a pressure vessel manufacturing company; previously, I was only involved in the post-weld heat treatment of carbon steel equipment, with heating temperatures ranging from 600 to 640 degrees； Several stainless steel units in recent orders require post-weld heat treatment after fabrication. Conventionally, stainless steel equipment does not require heat treatment; therefore, I am not very familiar with the heat treatment processes for such equipment. As far as I understand, heat treatment of stainless steel equipment refers to solution treatment or stabilization treatment, and for this purpose the heating temperature needs to reach 800–1000 degrees. Won’t the equipment deform at such high temperatures? Therefore, I would appreciate it if experienced colleagues could share their insights.
This is too technical; I can’t answer it for now
It’s unlikely. In the pressure vessel industry, both domestically and internationally, it is not practical to carry out post-weld heat treatment on stainless steel vessels. However, solubilization or stabilization treatments for components such as end caps, which are formed through hot forming, are feasible.
This post was last edited by fzujunru on 2018-6-21 00:32. Welding heat treatment is meant to eliminate residual welding stresses, right? So, just using a heating element to apply low-temperature annealing at around 540 degrees to the weld area should suffice, right? Solution treatment shouldn’t be easy to carry out; if it’s only to eliminate welding residual stresses, there’s no need for solution treatment. Furthermore, stabilization treatment only applies to a few grades of stainless steel that contain the stabilizing elements Ti and Nb
Go and take a look at Zhang Wenhua’s “Stainless Steel and Its Heat Treatment”
The issue with the last time was that I didn’t understand properly; as Brother Shanglou said, its heat treatment refers to the process of restoring the mechanical properties of a component after cold working. According to Article 8.1 of GB150.4: This requirement applies when the deformation of austenitic stainless steel exceeds 15%. But by looking at the formula in the table, for my device with an inner diameter of 1200 and a wall thickness of 8, the deformation rate of the cylinder is calculated as 50*8/604 = 0.66. What is the value of Rf for the deformation rate of the head?
Even after drawing the standard head, it was not possible to measure the R arc; therefore, I used the method of determining the four centers of an ellipse to find that the value of small R was 205. The deformation rate of the head is then: 75*8/209 = 2.87. It appears that the deformation rates of both the head and the cylinder have not exceeded 15%. There is no need to perform performance-restoring heat treatment on this device; then why was such a requirement specified during the design phase? I’m not sure if my understanding this time is correct; I would appreciate your guidance and corrections.
It seems that the overall heat treatment proposed in the design is aimed at the welds; we have encountered similar situations before as well!