For X70 pipes with 309L+306L surfacing on the inner wall and subsequently bent, how should stress-relief heat treatment be carried out?
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This post was last edited by realben on 2010-7-1 14:36. The base material is API 5L X70; a 309L+316L layer is welded onto the inner wall, and then the pipe is bent. How should stress-relief heat treatment be carried out? Is it normalizing followed by tempering? Still 620 degrees? Keep it at that temperature for a certain period of time? I hope everyone will come and discuss together
Reply 1# I’m not very familiar with the pipeline steel used in xxrc APIs. Could you explain it? What domestic or ASME grade is equivalent to it?
The ASME 9 classification is: S NO 1-3; this is roughly equivalent to grade 10 of A333. Below are the main properties and composition of X70: Yield strength: 570 Mpa; Tensile strength: 670 Mpa; Impact strength at 0 degrees: 200 J, 196 J, 178 J. Composition: C: 0.08, Si: 0.2, Mn: 1.4, P: 0.015, S: 0.003, Cr: 0.14, Ni: 0.07, Mo: 0.02, Cu: 0.07, V: 0.01, Nb: 0.036, Ti: 0.02, B: 0.0001. Heat treatment condition: Quenched and tempered
Reply to 4# xxrc: It seems to be C-Mn steel, but it is a modified steel and a high-strength steel. First, check the requirements for stress relief treatment in Volume 8 of ASEM; it’s in the UCS section, where the heat treatment temperatures and times for various steels are listed. For the heat treatment of cladding, a transition layer should be welded first; once it passes non-destructive testing, stress-relief heat treatment as specified in the UCS guidelines is carried out. After that, the cladding layer is welded, and no heat treatment is required for stainless steel cladding layers.
We first perform surfacing welding before processing the elbow, as it is difficult to carry out surfacing welding on the inner wall of the elbow. Therefore, the production process is as follows: 1. Surfacings welding of straight pipes ---- 2. Fabrication of elbows ---- 3. Stress relief. The question now is: how do we eliminate stress? What are some reference materials for temperature and time?
Reply to 6# xxrc: Then your cladding layer also needs to undergo heat treatment. But it’s no problem; this is inevitable. Manufacturers generally handle the heat treatment of composite sheets in the same way, focusing on the base material rather than the cladding layer. First, you need to check whether there are any recommended heat treatment requirements for your API 5L steel grade; if not, you will have to rely on similar materials as a reference. Look up the P.No. of such materials in ASME Volume IX, and then use that P.No. to find information in ASME Volume VIII. UW40 specifies the general requirements for heat treatment, while UCS56 outlines the heat treatment requirements specific to different steel grades as designated by their P.No., for example:
Yeah, sure, it can be used as a reference. Thanks to the guy upstairs
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