核电S32101双相不锈钢微型罩局部干式水下FCAW焊接冶金的基础研究

In order to ensure the safe operation of nuclear power facilities, underwater welding repair technologies of nuclear spent fuel pool should be studied. According to the requirements of repairing spent fuel pools of China's third generation nuclear power stations which are made of S32101 duplex stainless steel, a mini-cap local dry underwater flux cored arc welding (FCAW) method attached with far infrared heating modules has been proposed. Using a combination of numerical simulation and experimental measurements to reveal the characteristics of the temperature field and thermal cycles of the mini-cap composite heat source underwater FCA welding.Based on WRC 92 and Delong diagrams and combined with the calculation of equilibrium phase diagrams of S32101 steel, the microstructures of underwater welds are predicted and then orthogonal experiments are designed for validation. The influences of the wire and shielding gas composition, water depth and welding parameters on weld microstructure, mechanical and corrosion properties are clarifed. Combined with simulations of the welding temperature field, the effects of welding parameters and additional heating sources on HAZ microstructures, mechanical and corrosion properties are pointed out. The mechanism of hydrogen dissolved, aggregation, diffusion and escape in the mini-cap composite heat source underwater FCA welding and its impact on the properties of welding joints are researched.The results will help to deepen understanding of underwater welding metallurgy, materials, and joint properties of duplex stainless steels, and lay the theoretical and experimental foundations for the research and development of nuclear spent fuel pool underwater welding repair technologies.

为了保障我国核电设施的安全运行，必须研究核电乏燃料池的水下焊接维修技术。针对我国第三代核电乏燃料池用的S32101双相不锈钢，提出了外加远红外加热模块的微型排水罩局部干式复合热源水下药芯焊丝焊接（FCAW）方法。采用数值模拟和实验检测相结合的方法,揭示微型罩复合热源水下FCAW焊接温度场和热循环的特征；依据WRC92和Delong组织图，结合S32101钢平衡相图的计算，先对水下焊缝组织进行预测，然后设计正交试验进行验证，阐明焊丝和保护气体成分、水深、焊接参数等对焊缝组织、力学和耐腐蚀性能的影响规律；结合焊接温度场模拟，研究焊接参数和外加加热机制对HAZ组织、性能的影响规律，研究微型罩复合热源水下FCAW中的氢溶解、聚集、扩散和逸出的规律及其对接头性能的影响。研究成果有助于深化对双相不锈钢水下焊接冶金、材料和接头性能等的认识，为研发我国核电乏燃料池的水下焊接修复整体技术奠定理论和试验基础。

我国正大力建设核电站，而我国第三代核电乏燃料池采用S32101双相不锈钢建造，在地震、袭击等特殊情况下可能受到破坏。为了冷却乏燃料以及防止其发生链式反应，乏燃料池中注满一定浓度的硼水，因此乏燃料池的维修必须采用水下焊接技术。本项目针对我国第三代核电乏燃料池用的S32101双相不锈钢，进行了水下湿法、微型排水罩局部干法和高压干法水下药芯焊丝焊接（FCAW）的研究。依据WRC92和Delong组织图，结合S32101钢平衡相图的计算，对水下焊缝的组织形成进行预测。结合水下焊接温度场的分析，研究焊接参数和外界环境热传导机制对HAZ组织、性能的影响规律。主要研究了水下焊接电弧稳定性、双相不锈钢焊接接头组织的模拟分析、水下焊接温度场分析、水下脉冲焊接工艺参数优化、水下焊缝成形以及焊丝成分、水深、焊接参数等对焊缝组织、力学和耐腐蚀性能的影响规律。研究成果有助于深化对双相不锈钢水下焊接冶金、材料和接头性能等的认识，为研发我国核电乏燃料池的水下焊接修复整体技术奠定理论和试验基础。