Are post-heating and dehydrogenation the same thing?
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The welding procedure includes only post-heating without hydrogen removal, and its application temperature and time are very similar. If they’re not the same thing, how should we make a distinction in practical use?
They’re not the same thing, right? Emergency post-heating involves applying heat treatment promptly after welding, before cracks form; this helps to prevent cold cracks. The temperature for emergency post-heating is usually between 300–600°C. Its purpose is to reduce residual stresses, improve the microstructure, lower hardenability, and reduce diffused hydrogen. For austenitic stainless steels, post-heating isn’t very effective in removing hydrogen. There’s also post-heating and heat treatment after welding! Normalizing, quenching and tempering, etc
It’s not the same; there’s a discussion on the forum, just search for it
Post-heating and dehydrogenation should both serve the same purpose. I can’t remember if the temperature range is the same. If it’s the same, then the intermediate heat treatment process is the same as well.
Post-heating is used to reduce the cooling rate of the welded part and prevent the formation of hardened microstructures. Dehydrogenation is itself achieved through PWHT, that is, post-weld heat treatment; the two are not the same thing.
The main reason they are difficult to distinguish is that their purposes are essentially the same. The dehydrogenation seems to be a bit higher at higher temperatures. But it’s not clear which one to use in which situation.
The purpose of post-weld heat treatment for carbon steel and low-alloy steel is to drive hydrogen out of the weld metal; post-weld heat treatment is a method of hydrogen removal, and heat treatment performed immediately after welding can also serve to remove hydrogen.
They are not the same thing; eliminating H accelerates the diffusion of hydrogen leakage, while post-heating is used to remove residual stresses
Then why wait? Just remove the hydrogen directly.
It’s even worse: first, post-heating doesn’t impose any restrictions on the materials; second, there is specialized heat treatment for residual stresses, so there’s no need to introduce post-heating as well.