核用ODS钢电阻点焊性能

为评价氧化物弥散强化合金(oxide dispersion-strengthened alloy, ODS)钢的电阻点焊性能，使用金相显微镜及扫描电镜观察了9CrYWT-ODS钢焊点不同区域的组织，测试了焊点的拉伸剪切性能，确定了合适的焊接电流范围. 结果表明，焊点不同区域内氧化相尺寸存在明显差异，热影响区回火区温度较低，氧化相细小，热影响区相变区温度较高，氧化相有所长大，熔核区温度很高，氧化相明显粗化. 随着焊接电流增大，熔核尺寸增大导致焊点最大拉伸剪切力升高的同时，失效方式由界面失效逐渐转变为部分界面?部分焊点拔出失效及完全焊点拔出失效，继续增大焊接电流到飞溅产生时，熔核尺寸减小引起最大拉伸剪切力降低，失效方式再次转变为部分界面?部分焊点拔出失效和界面失效. 根据拉伸剪切试验结果确定合适的焊接电流范围为6.6 ~ 7.0 kA.

Resistance spot weldability of nuclear ODS steel

For evaluating the resistance spot weldability of oxide dispersion-strengthened alloy (ODS) steel, the microstructure of different regions of 9CrYWT-ODS steel spot weld was observed by optical microscope and scanning electron microscope, and the tensile and shear properties of spot welds were tested. Finally, the appropriate welding current range was confirmed. Results show that the size of the oxides in different areas of the spot weld exhibits obvious differences. The tempered zone in the heat affected zone contains tiny, dispersed oxides due to the low temperature during welding process. The phase transformation zone in the heat affected zone contains less small oxides and more large oxides owing to the higher temperature. The very high temperature in the weld nugget zone results in obvious coarsening of the oxides. As the welding current increases, the increase of the nugget size leads to the increase of tensile and shear force, and the tensile shear failure mode gradually changes from the interfacial mode to the partial interfacial-partial pullout mode, and then further transformed into the fully pullout mode. Continuing to increase the current to the occurrence of splash, the decrease of the nugget size results in the decrease of tensile shear force. The failure mode again changes to the partial interfacial-partial pullout mode and interfacial mode. According to the tensile and shear test results, the appropriate welding current range is 6.6 ~ 7.0 kA.