铝硅镀层钢激光填丝焊接接头组织和性能

Microstructure and properties of laser welded joint with filler wire of Al-Si coated press-hardened steel

对铝硅镀层热成形钢进行激光填丝焊接试验,研究填充焊丝对焊接接头显微组织、力学性能及拉伸失效机制的影响.结果表明,在激光自熔焊条件下,焊缝中平均Al元素含量为1.90%(质量分数),显微组织为马氏体和粗大的δ铁素体,焊接接头抗拉强度和断后伸长率分别为1 340 MPa和1.80%,因δ铁素体与马氏体之间存在显著的硬度差(142 HV),拉伸时裂纹源于δ铁素体和马氏体之间的相界面.在激光填丝焊条件下,焊缝平均Al元素含量降低至0.96%,由于填充焊丝对铝的稀释作用使得焊缝为全马氏体组织,焊接接头抗拉强度和断后伸长率分别提升至1 510 MPa和4.4%.因填充焊丝同时对焊缝中的碳也有稀释作用,焊缝中马氏体硬度(491 HV)低于母材中马氏体(523 HV),拉伸时裂纹于马氏体内部萌生并扩展,最终断裂于焊缝.

The effects of filler wire on the microstructure,mechanical properties and tensile failure mechanism of welded joints were studied.The results show that the average Al content in the weld seam is 1.90% without filler wire,and the microstructure contained martensite and coarse δ-ferrite.The tensile strength and elongation of the welded joints were 1 340 MPa and 1.80%,respectively.Due to the significant hardness difference(142 HV) between δ-ferrite and martensite,the crack originated from the phase interface between δ-ferrite and martensite.The average Al content in the weld seam was reduced to 0.96% with filler wire.Due to the dilution of Al by filler wire,the microstructure was full martensite and the tensile strength and elongation of the welded joint were increased to 1 510 MPa and 4.4%.The hardness of martensite in the weld seam(491 HV) was lower than that in the base metal(523 HV) because the filler wire also dilutes the C.During tensile test,the crack initiated and propagated in the martensite and finally filed in the weld seam.