| Light weight is one of the most important technologies for reducing fuelconsumption, decreasing automobile emissions and improving security ofautomobile. At present, one of the main measures of achieving light weight isadopting high-strength lightweight materials. To reduce weight of automobile toachieve the function of energy saving and environmental protection, lightermaterials such as aluminum alloys, magnesium alloys, plastic and compositematerials are used, so it requires us to master connection technology of dissimiliarmaterials such as steel/aluminum. Welding-brazing is suitable for welding steelwith aluminum, it provides a new approach for high-quality and efficientconnection of steel with aluminum.In this thesis, the phenomenon of non-homogeneous intermetallic compoundslayer often appears on the interface during steel-aluminum laser welding-brazingexperiments has been analysed. So in order to improve this phenomenon, researchabout the influence of v-shaped groove on properties of laser welding-brazedsteel-aluminum butt joint was carried out. At the same time, having carried outtechnical research about laser welding with filler wire.Fristly, mechanism and characteristics of laser welding and laser welding withfiller wire were summed up, the advantages and disadvantges of laser weldingtechnology and its application fields were stated, current situation of application ofautomobile body-in-white lightweight materials and current status ofsteel-aluminum dismiliar metal connections were analysed, the platform ofsteel-aluminum laser butt welding-brazing experiments was set up.Secondly, the influence of v-shaped groove on butt joint properties ofsteel-aluminum was deeply discussed.3D numerical simulation of temperature ofsteel-aluminum laser butt welding-brazing with no groove and a v-shaped grooveon parent material were carried out using ANSYS respectively, temperaturecontours under above two situations were obtained through a series of steps such asmodeling, meshing, selecting the heat source, establishing the boundary conditionand post-processing. According to the difference of temprarure gradient on theinterface and relative theoretical analysis, a v-shaped groove can improve thephenomenon of non-homogeneous intermetallic compounds layer occurs on the interface commonly during experiments of steel/aluminum laser buttwelding-brazing, it can be a good guidance for steel-aluminum laser buttwelding-brazing experiments.Thridly, the experiments of steel-aluminum laser welding-brazing with nogroove were carried out. Optimal parameter was obtained through orthogonalexperiment. Then single factor welding experiment according to the optimizedparameter was carried out to explore the welding quality under different processparameters, concluding rule of process parameters (laser power, welding speed,wire feed rate)had influence on welding quality. After welding experiments, weldtopography, microstructure, tensile strength were detected to analyze theperformance of weld. The common welding defects during the welding processwere summarized and explained.Finally, the experiments of steel-aluminum laser butt welding-brazing with av-shaped groove on parent material were carried out. The results were compared tothose there is no groove on parent material in cross session, the distributionsituation of intermetallic compounds on the interface between seam and galvanisedsteel, tensile strength, the location of fracture. A v-shaped groove can improvemechanical property of seam during steel-aluminum laser butt welding-brazingexperiments was proved by contrast experiment. |
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