About 28NiCrMoV8-5 steel and its welding

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Now I am encountering a problem about 28NiCrMoV8-5 steel and its welding on a piece of equipment. I have never come into contact with this type of steel before and the information is very limited. I hope friends who know more can help me. The steel composition: C0.24-0.3 ； Si is less than 0.4 ； Mn0.15-0.4 ； Cr1-1.5 ； Mo0.35-0.55 ； Ni1.8-2.2 ； V0.05-0.15% ； SP is less than 0.035 ； The yield strength is greater than 590MPa, the tensile strength is about 750MPa, and the steel thickness is about 330mm. Now the problem is: 1. We are going to use narrow gap submerged arc welding. Do you have relevant welding materials (welding wire and flux)? 2. If stress relief annealing is performed after welding, how much will the base metal in the heat affected zone soften? 3. Is it appropriate to perform stress relief annealing after welding? 4. Welding CCT diagram, structure, properties, etc. of this steel type. I don’t know much about this steel type, and I hope friends who know about it can give me some advice.