Issues with heat treatment of pipelines?
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This post was last edited by Shandong Huaxing on 2010-12-7 at 13:44. A new steel pipe line No. 20 has been installed; the medium flowing through it is acidic. The design drawings require heat treatment after welding to prevent stress corrosion. How should the temperature profile be determined? Is it necessary to conduct new welding procedure qualifications? Thank you! ~
This post was last edited by Shandong Huaxing on 2010-12-7 at 13:45. For media such as hydrogen sulfide and amine-rich liquids, 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 wet hydrogen sulfide environment. The S element is mainly controlled during production. Post-weld heat treatment can improve the microstructure and prevent stress corrosion. (Reposted from foxbat)
This post was last edited by Shandong Huaxing on 2010-12-7 at 13:46. Have you also carried out heat treatment for such pipelines in your newly installed equipment? How to conduct quality inspection?
This post was last edited by Clauspolunit on 2010-12-7 at 18:00. For pipelines related to H2S (including sour gas, sour water, and amine solutions), stress relief treatment is usually carried out to prevent stress corrosion. Generally, new installations only require post-weld heat treatment, whereas old pipelines also need pre-weld heat treatment. There are specific standards that detail how to carry out pre-welding and post-welding heat treatment. I only remember that quality inspection departments usually check whether the construction unit has carried out heat treatment as required by examining the hardness of the welds.