Is pre-weld hydrogen removal and post-weld heat treatment required for the repair of pressure vessels made of 304L that are currently in use?
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Is pre-weld hydrogen removal and post-weld heat treatment required for the repair of pressure vessels made of 304L that are currently in use? The medium is acidic gases H2S (about 40%) and H2, with a pressure of 0.5 MPa and a temperature of 40°C℃
This post was last edited by jizhanwei22 on 2017-2-8 at 17:20. My opinion is: none of them are necessary. Reason: Starting with hydrogen removal heat treatment, its main purpose is to eliminate delayed cracks that occur during metal welding; however, delayed cracks do not arise in all metal weldings. Only low-alloy steels with higher strength grades are likely to exhibit this phenomenon. Therefore, S30403 does not require dehydrogenation heat treatment. Post-weld heat treatment is even less necessary. GB150 specifies clearly that, unless otherwise specified in the drawings, welded joints of austenitic stainless steel do not require heat treatment. Furthermore, if austenitic stainless steel is improperly heat-treated, intergranular corrosion is exacerbated, leading to the precipitation of Cr23C6 in the base metal and welds as well as the formation of a σ-phase, which results in the embrittlement of the austenitic stainless steel.
Austenitic stainless steel does not require pre-heating or post-heating treatment, but the weld groove and the area within 20 mm on either side must be cleaned to remove oil and other contaminants.
Whether pre-weld degassing and post-weld heat treatment are necessary depends on the design requirements. For information on pre-weld degassing, it is recommended to read this article: \"Degassing Treatment for Pipes Before Welding\" http://www.docin.com/p-948954449.html