Under what circumstances must stainless steel containers be heat-treated?
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Austenitic stainless steel containers generally do not require stress-relief heat treatment. When is it necessary to do it? (I forgot in which textbook it was mentioned)
It seems that the container must undergo heat treatment when used at low temperatures.
Stainless steel components that require corrosion resistance must undergo heat treatment, followed by pickling and passivation
Heat treatment of austenitic stainless steels: The common heat treatment processes for austenitic stainless steels include solution treatment, stabilization treatment, and stress relief treatment. (1) Solution treatment. Heating the steel to 1050–1150°C and then quenching it in water serves primarily to dissolve the carbides in austenite and maintain this state at room temperature, thereby significantly improving the steel’s corrosion resistance. As mentioned above, to prevent intergranular corrosion, solution treatment is typically used to dissolve Cr23C6 in austenite, followed by rapid cooling. Air cooling can be used for thin-walled parts, while water cooling is generally employed. (2) Stabilization treatment. It is generally carried out after solution treatment, and is commonly used in 18-8 steel containing Ti and Nb. After solution treatment, the steel is heated to 850–880°C and then cooled in air; at this temperature, the chromium carbides dissolve completely, whereas the titanium carbides do not dissolve completely and precipitate during cooling, preventing the formation of new carbides. This effectively eliminates intergranular corrosion. (3) Stress relief treatment. Stress relief is a heat treatment process used to eliminate the residual stresses in steel resulting from cold working or welding; it generally involves tempering at 300–350°C. For steels that do not contain the stabilizing elements Ti and Nb, the heating temperature should not exceed 450°C to prevent the precipitation of chromium carbides, which could lead to intergranular corrosion. For cold-worked and welded parts of ultra-low carbon and Ti-, Nb-composite stainless steels, heating at 500–950°C followed by slow cooling is required to relieve stress (the upper temperature limit is used for removing welding stress); this can reduce the tendency to intergranular corrosion and enhance the steel’s resistance to stress corrosion.
Stainless steel generally undergoes more solid solution treatment and stabilization treatment
No, for stainless steel, impact testing and heat treatment are not required when used at temperatures above -196°C
The original poster asked under what circumstances heat treatment is necessary, but none of the replies above addressed this point properly. Austenitic stainless steels are generally only subjected to solution treatment; those containing stabilizing elements are treated to stabilize them. Heat treatment requirements are usually specified explicitly in the technical specifications section of the drawings, and it must be carried out whenever required by the drawings
Generally, it is understood that pressure vessels made of any material that are prone to stress corrosion, or those exposed to highly hazardous media under high pressures, require stress-relief heat treatment. Logically, shouldn’t stainless steel also undergo heat treatment under these two conditions? I’m not sure if that’s correct?
GB150 specifies that equipment with media classified as extremely hazardous or highly hazardous shall undergo heat treatment, with the exception of austenitic stainless steels. However, ASME standards specify that post-weld heat treatment is only required for carbon steel and low-alloy steel; stainless steel does not require such treatment. Nevertheless, for austenitic stainless steel pressure vessels with a thickness greater than 50 mm, heat treatment is still necessary.