为了研究冷轧复相钢和低合金高强钢(HSLA)差厚板的拼焊性能，采用10 kW 级光纤激光器，改变激光功率和焊接速度进行拼焊实验。针对焊缝成形、金相组织、接头硬度、拉伸强度和成形性能进行一系列测试实验。结果表明，冷轧复相钢和低合金高强钢光纤激光拼焊可以得到成形良好的焊缝。焊缝组织以板条马氏体树枝晶为主，复相钢热影响区分为回火软化区、细晶等轴马氏体区和粗晶等轴马氏体区以及混合区等。拉伸试样断裂位置均位于低合金高强钢母材，焊缝杯突裂纹均位于薄板一侧并平行于焊缝。实验结果为冷轧复相钢和低合金高强钢差厚板激光拼焊提供一定的工艺和理论指导。

To research the tailor welding of cold rolled multi-phase steel and high strength low alloy (HSLA), tailor welding is conducted with 10 kW fiber laser varying laser power, welding velocity and defocusing amount. Weld seam formation, metallographic microstructure, hardness and formability are tested. The results show that the formation of weld seam is sound. The metallographic microstructure of weld seam is mainly lath martensite dendrites. Heat affected zone of multi-phase steel is combined with tempered softening zone, fine grain equiaxed zone, coarse grain equiaxed zone and the mixture zone. The width of softening zone is affected by welding velocity most severely. The tensile strength and formability of weld seam are sound. The fracture location of tensile specimen is base metal of HSLA consistently. The fracture location of Erickson LDH test is parallel with the weld seam on the side of HSLA. The results can provide guidance on welding processing and theory of tailor welding of multigauge cold rolled multi-phase steel and HSLA.