Hybrid laser-metal inert gas keyhole welding of thick steel/Al butt joints

Autor: Dongqi Lu, Li Cui, Dingyong He, Feng Pan
Rok vydání: 2019
Předmět:
Zdroj: Journal of Laser Applications. 31:022410
ISSN: 1938-1387
1042-346X
DOI: 10.2351/1.5096102
Popis: Dissimilar joining of steel/Al joints has become more and more significant in industrial applications with particular weight saving interest. However, directly welding of steel/Al joints even in thin thickness is very difficult. In the present study, the hybrid laser-metal inert gas (MIG) source focused on the steel side in keyhole mode was introduced to weld steel/Al butt joints of 6 mm in thickness. Effects of the laser offsets on the weld shape, interface microstructures, and ultimate tensile strength (UTS) of the steel/Al joints were investigated. Sound steel/Al butt joints were obtained by using this hybrid laser-MIG keyhole welding process. By increasing the laser offsets from 0.6 and 0.8 mm, the welds exhibited a better shape with a smooth appearance attributable to the reduced heat input. The positions through the thickness of the steel/Al joints played an important role in the morphology and thickness of the intermetallic compound (IMC) layers at the Al/weld interface. The IMC layers had a thick irregular morphology at the upper part and the lower part, while the layers at the middle part exhibited a relatively thin and uniform morphology. With some certain welding conditions, the Al/weld interface at the lower part of the steel/Al joints transformed to a welding-brazing mode from a fusion one. The island-shape structures were formed at the Al/weld interface, and the IMC layers were composed of Fe2Al5 layer and needlelike Fe4Al13 phases. The maximum UTS of 87.0 MPa was obtained at a laser offset of 0.6 mm. Although the failure occurred in the IMC layers revealed a brittle fracture, the fracture morphology and locations were a mixed failure, which had a certain resistance to the crack propagation of the IMC layers.Dissimilar joining of steel/Al joints has become more and more significant in industrial applications with particular weight saving interest. However, directly welding of steel/Al joints even in thin thickness is very difficult. In the present study, the hybrid laser-metal inert gas (MIG) source focused on the steel side in keyhole mode was introduced to weld steel/Al butt joints of 6 mm in thickness. Effects of the laser offsets on the weld shape, interface microstructures, and ultimate tensile strength (UTS) of the steel/Al joints were investigated. Sound steel/Al butt joints were obtained by using this hybrid laser-MIG keyhole welding process. By increasing the laser offsets from 0.6 and 0.8 mm, the welds exhibited a better shape with a smooth appearance attributable to the reduced heat input. The positions through the thickness of the steel/Al joints played an important role in the morphology and thickness of the intermetallic compound (IMC) layers at the Al/weld interface. The IMC layers had a thick ...
Databáze: OpenAIRE
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