For a solution at 100°C with PH=10, carbon steel is used – is post-weld heat treatment required?
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For a solution at 100°C with PH=10, carbon steel is used – is post-weld heat treatment required?
It’s related to the material and wall thickness of the pipe chosen, not to the medium
How much pressure? If it is at atmospheric pressure, heat treatment is not necessary.
Post-weld heat treatment is generally recommended for alkali solution pipelines, especially those using NaOH as the alkali solution
Thank you. I have a question: In Appendix D of SH/T3059, are the temperature and concentration limits for the use of carbon steel and low-alloy steel in alkaline solutions applicable only to NaOH solutions? My personal understanding is that for alkaline solutions with a concentration or pH value equivalent to that of NaOH, the material selection can be determined by referring to the modified diagram. I’m not sure if this understanding is correct; I hope experts can give me some advice.
Post-weld heat treatment should be carried out when the temperature exceeds 46 degrees and the alkali content is greater than 5% to prevent alkali stress corrosion.
After thorough research, the pH value is 10; if my calculations are correct, the mass concentration of NaOH is approximately 4%. At 100°C, according to the guidelines for selecting alkali solutions, post-weld heat treatment is required. I hope someone can correct me!
If NaOH is present, heat treatment won’t solve the problem; the temperature is too high. In some factories, carbon steel used in the alkali solution pipelines is heated with low-pressure steam, and leaks often occur. Using this for heat treatment at 100°C probably won’t solve the problem either.