Welding heat treatment issues for No. 20 steel pipe lines
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Urgent help needed: It’s a 20-mm-diameter steel pipeline carrying acidic gases. The design specifications require heat treatment after welding to prevent stress corrosion, but the wall thickness of the pipeline is only 10 mm. Do you think heat treatment is necessary? How should the temperature profile be determined? Is it also necessary to conduct new welding process evaluations? I hope experienced sea travelers can offer help! ! This post was last edited by whb002002 on 2009-4-9 22:01.]
For gases such as hydrogen sulfide, heat treatment is required to prevent stress corrosion. The main chemical elements in steel that affect hydrogen sulfide corrosion are manganese and sulfur. During the welding of equipment, manganese leads to the formation of martensite and bainite microstructures with high strength but low toughness, resulting in extremely high hardness; this is highly detrimental to the equipment’s resistance to hydrogen sulfide stress corrosion (SSCC). Sulfur, on the other hand, forms non-metallic inclusions such as MnS and FeS in the steel, causing localized softening of the microstructure, which can lead to hydrogen-induced cracking (HIC) or stress-oriented hydrogen-induced cracking (SOHIC) in a humid hydrogen sulfide environment. The S element is mainly controlled during production. Post-weld heat treatment can improve the microstructure and prevent stress corrosion.