Bolt heat treatment
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Can’t the bolts be used anymore after the entire equipment is heat-treated?
:'(The heat treatment process and the final heat-treated state of bolts are different from those of stress vessels after welding; if most bolt materials are subjected to post-welding heat treatment along with the vessels, it will certainly affect their properties. How can such a thing be done?)
If that’s the case, new bolts will have to be replaced.
I’d like to ask why bolts need to be heat-treated along with the equipment
The heat treatment process for bolts is different from the post-weld heat treatment for pressure vessels
The materials for pressure bolts are usually treated by quenching and tempering. If the post-weld heat treatment temperature did not exceed the tempering temperature of the bolt material and there is no severe oxidation on the surface, it should still be usable. For example, the heat treatment process for 30CrMoA is typically quenching at 940°C followed by tempering at 650°C. When the shell material is of Fe-1 category (such as Q245R), the post-weld heat treatment temperature is around 600°C, and this has little impact on the mechanical properties of the bolt material. When the shell material is of Fe-5A class (such as 12Cr2Mo1R), the post-weld heat treatment temperature is around 680°C, which has a significant impact on the mechanical properties of the bolt material; such bolts should not be used any longer. The above applies to pressure-bearing fasteners with requirements regarding strength performance; ordinary assembly fasteners can still be used. Pressure-bearing fasteners should not and need not undergo post-weld heat treatment along with the furnace.
A U-tube heat exchanger that requires overall heat treatment
U-tube heat exchangers require overall post-weld heat treatment. What are the materials used for the tube side and the shell side, and what are the fluids flowing through them? If the tube box requires heat treatment, machining should be carried out after the treatment. Do the tube boxes, tube bundles, and shell all require heat treatment?
Heat treatment of bolts is different from heat treatment of equipment