超薄不锈钢在航天、医疗器械、日用品中的应用日趋广泛, 对其激光焊接质量也提出了更加苛刻的要求。由于材料很薄, 易于汽化穿孔, 要想得到连续、无烧穿的焊缝, 关键是对参数的精确控制。采用光纤激光实现了0.2 mm厚1Cr18Ni9Ti 不锈钢片的对接及搭接焊。研究了激光功率、焊接速度、离焦量、脉冲频率、占空比等工艺参数对焊缝表面成形的影响规律, 并对焊缝显微组织及接头力学性能进行了考察。结果表明, 在连续焊模式下, 即使采用非常小的热输入, 也无法避免焊缝起始及收尾处出现的烧穿; 脉冲焊模式下, 热输入一定时, 采用低的脉冲频率、占空比及焊接速度相比高的脉冲频率、占空比及焊接速度可以有效减少单脉冲能量, 从而避免焊缝在起始及收尾处的烧穿。在优化的工艺参数下可得到表面成形良好、无烧穿的对接及搭接焊缝。焊缝中心区由柱状晶与等轴晶组成, 几乎不存在热影响区, 对接接头抗拉强度可高于母材, 搭接接头经拉剪测试断于母材。

With the wide application of ultra-thin stainless steel in aerospace, medical equipment and commodities,laser welding of ultra-thin stainless steel has drawn much attention. This material is very difficult to be welded because of material’s evaporation during welding, causing burn-through. The welding parameters should be appropriately controlled to obtain continuous welds without burn-through. In this paper, butt and lap welding of 1Cr18Ni9Ti stainless steel sheet with thickness of 0.2 mm was realized by fiber laser, and the influence of welding parameters such as laser power, welding speed, defocusing distance, pulse frequency and duty on weld appearance was investigated. The microstructure and mechanical properties of the welded joints were also investigated. The results show that burn-through is easy to occur in weld, especially for butt welding. Under continuous welding mode, burn-through cannot be avoided even under very low heat input. Under pulsed welding mode,low frequency, duty and welding speed can reduce single pulsed energy, thus effectively preventing burn-through. Under optimized welding parameters, welds without burn-through can be obtained for both butt and lap welds. The tensile strength of butt joint is higher than the base metal, and the lap joint fractures at the base metal during tensile-shear testing.Weld is composed of columnar crystals and equiaxed grains, and no obvious heat-affected zone is observed.