核主泵屏蔽套近无缺陷激光焊接技术

Near-free-defect Laser Welding of AP1000 Nuclear Reactor Coolant Pump Can

针对我国AP1000核主泵屏蔽套焊接过程存在的问题,提出一种近无缺陷激光焊接技术,实现屏蔽套材料Hastelloy C-276的优良焊接成形。分析激光焊接过程对材料微观组织的影响规律,评价核主泵温度条件下焊接接头拉伸性能;研究焊缝在酸碱盐中的电化学腐蚀行为,评价焊缝耐腐蚀性能。通过有限元法计算屏蔽套焊接变形特征,揭示横向收缩变形对制造精度的影响。结果表明,所提出的脉冲激光焊接技术可以实现核主泵屏蔽套材料的优良焊接成形,焊缝处无明显焊接缺陷;在核主泵温度条件下,焊接接头力学性能与母材基本相当,可以保证长使役可靠性;焊缝在中性及酸性环境下,腐蚀性能均优于母材,提升了焊缝的可靠性。通过模拟计算发现激光焊接会导致焊接样件发生横向收缩变形,但该变形大小仅为屏蔽套制造精度的1/10,焊接精度完全满足屏蔽套制造要求。

Aiming at solving the problems in the welding process of AP1000 nuclear reactor coolant pump can in China, a laser welding technology with near-free-defect is proposed to achieve the good welding of Hastelloy C-276 which is used as the materials of the nuclear reactor coolant pump can. The effect of laser welding process on the microstructure is analyzed, and the tensile properties of weld joint at the different working temperature are evaluated. Also, by the electrochemical corrosion experiments of weld joint in acid, neutral and alkali solution, the corrosion resistance of weld joint is investigated. In addition, the welding deformation characteristics are calculated based on the finite element method, and the influence of transverse shrinkage distortion on the manufacturing accuracy is revealed. The results indicate that the pulse laser welding technology could achieve the good welding of Hastelloy C-276 without obvious welding defects. Under the condition of the can working temperature, the mechanical properties of welding joint is almost the same as that of base metal, which can guarantee the long using credibility. The corrosion resistances of the weld joint in the neutral and acidic conditions are better than those of base metal, which could improve the reliability of the weld joint. By the numerical simulation, it is found that the laser welding could cause the transverse shringkage distortion of the welding sample. But the distortion size is just 1/10 of the can manufacturing precision, so the welding precision completely satisfies the requirements of manufacturing precision of the nuclear reactor coolant pump can.