Can overall post-weld heat treatment replace hydrogen elimination treatment?

　　If the entire equipment is heat treated immediately after welding, the post-weld hydrogen elimination treatment can be dispensed with.

How do you understand that "immediately"?

What is the shortest time immediately? One day or one hour?

I think there should be a concept of time. Just like GB150 stipulates that if carbon steel and low alloy steel are used for a long time at temperatures above 425 degrees, this "long term" can be understood as 10,000 to 100,000 hours, which is comparable to the design life of the pressure vessel.

What is hydrogen elimination treatment? What is its function? Is it the same as heat treatment?

Post-weld hydrogen elimination treatment refers to the low-temperature heat treatment performed after the welding is completed and the weld has not yet cooled to below 100°C. The general specification is to heat to 200~350℃ and keep warm for 2-6 hours. The main function of post-weld hydrogen elimination treatment is to accelerate the escape of hydrogen in the weld and heat-affected zone, and is extremely effective in preventing welding cracks during welding of low-alloy steel. During the welding process, due to the uneven heating and cooling, as well as the constraints or external constraints of the component itself, welding stress will always be generated in the component after the welding work is completed. The existence of welding stress in components will reduce the actual load-bearing capacity of the welded joint area and produce plastic deformation. In severe cases, it will also cause damage to the component. 　　Stress relief heat treatment is to reduce the yield strength of the welded workpiece under high temperature to achieve the purpose of relaxing the welding stress. There are two commonly used methods: The first is overall high-temperature tempering, that is, placing the entire weldment into a heating furnace, slowly heating it to a certain temperature, then keeping it warm for a period of time, and finally cooling it in the air or in the furnace. This method can eliminate 80%-90% of welding stress. Another method is local high-temperature tempering, that is, only heating the weld and its surrounding area, and then slowly cooling it to reduce the peak value of the welding stress and make the stress distribution relatively gentle, thereby partially eliminating the welding stress. 　　After welding of some alloy steel materials, the welded joints will have hardened structures, which will deteriorate the mechanical properties of the materials. In addition, this hardened structure may cause joint damage under the action of welding stress and hydrogen. If after heat treatment, the metallographic structure of the joint is improved, the plasticity and toughness of the welded joint are improved, thereby improving the comprehensive mechanical properties of the welded joint. reference web http://ks.cn.yahoo.com/question/1508073004313.html

What the person above said is good, the sooner you put it into the furnace after welding, the better. You are afraid of cracking. If it cracks, it will be over. There is no need to do the overall heat treatment.

Yes, if heat treatment is performed immediately after welding, there is no need to do hydrogen elimination treatment.

Thanks for the explanation on the 8th floor. Hydrogen elimination treatment should be carried out immediately after welding.

If heat treatment is performed immediately, there is no need to eliminate hydrogen.

Agree with what 12th floor said. Because during the welding process, factors such as insufficient baking of the welding material and the air humidity of the welding environment can easily cause hydrogen penetration in the weld, materials that are sensitive to hydrogen embrittlement must undergo hydrogen elimination treatment in time (the processing temperature is generally around 250°C). If the equipment is welded and post-weld stress relief heat treatment is performed immediately, the hydrogen elimination treatment can be avoided. Otherwise, the hydrogen elimination treatment of the weld seam should be performed first, and then the stress relief heat treatment is performed.

Heat treatment immediately after welding can be used instead, only for the last weld.

Can you actually name a few commonly used materials that are prone to hydrogen embrittlement? Let’s talk about it based on practice!

8. What the person above said is good. The sooner you put it into the furnace after welding, the better. Heat treatment immediately after welding can be used instead.

No, because the overall heat treatment is carried out after all welding is completed, how to ensure that the temperature of the joint welded first is not lower than 100℃.

GB150 10.4.3 Vessels that require hydrogen elimination treatment after welding can be exempted from hydrogen elimination treatment if post-weld heat treatment is performed immediately after welding.

If post-weld heat treatment is performed immediately after welding, hydrogen elimination treatment can be avoided. The subsequent time limit is generally within 3 hours.

I found that many manufacturers do not use hydrogen in the final heat treatment. .