The IV generation nuclear energy system is an important direction of advanced nuclear energy development. Focusing on the construction requirements of the "CFR600 sodium-cooled demonstration fast reactor", the special stainless steel welding material ER316H (KD) has been developed for the fourth-generation sodium-cooled fast reactor. The replacement design of interstitial solid solution strengthening elements is proposed, which solves both the high temperature strength and the corrosion resistance for the weld joint. By controlling the nickel-chromium equivalent ratio and the microstructure of the weld metal, the welding crack sensitivity of large-thickness stainless steel joint was reduced significantly and the stability of the weld structure at high temperature is improved. The evolution mechanism of the weld metal microstructure and its influence on the performance of the weld joint have been studied, and the optimized composition for the special welding material was identified, which ensure the joint performances including the high temperature strength, corrosion resistance and low crack sensitivity. The developed welding consumables was successfully applied to the first CFR600 sodium-cooled demonstration fast reactor vessel, independent heat exchangers, sodium-air heat exchangers, and high-temperature sodium pipelines successfully.

Fig. 1. Effect of C content and aging time at 600℃ on the decomposition δ-ferrite and properties of weld metal.