Technology Research On Fiber Laser Butt Welding High-strength Automobile Steel

As one of the advanced manufacturing technologies to promote the development of automotive lightweight technology, laser welding technology is applied more and more extensively in the auto industry, and gradually become a standard welding process. When laser welding technology is applied for automobile body-in-white welding, especially for butt joints, it can greatly improve the strength and stiffness and then increase the security of the body. Also, benefits of reducing the overlap width of the lap joint, saving materials and decreasing the body weight, are all conductive to body lightweight. In this paper, difficulties in the laser welding process for automobile body-in-white butt joints are analyzed. And research on the influence of butt joint gap to performance of high-strength automobile steel after fiber laser welding is developed. Technology of laser welding with filler wire for butt joints is also researched.First, mechanism and characteristics of laser deep penetration welding and laser welding with filler wire are summed up. Then the application of laser welding on automobile body-in-white welding is described. Current status, difficulties and key technologies of laser welding automobile body-in-white butt joints are analyzed. Experimental platform of fiber laser deep penetration welding and laser welding with filler wire is set up. The integration communication and control of experimental set up is conducted.Second, research on the influence of butt joint gap to performance of high-strength automobile steel after fiber laser welding is developed. Optimal parameter is obtained through orthogonal experiments when butt joint gap is zero. Single factor welding experiments are carried out with changing butt joint gap according to the optimized parameter. After welding experiments, weld topography, cross session, tensile strength, micro-hardness and microstructure are detected to analyze the performance of weld. Through processing and analyzing the experiment data, the biggest butt joint gap when weld tensile strength meets the requirement is obtained. This provides references for research and application of laser deep penetration welding on automobile body butt joint.Finally, technology research of laser welding high-strength automobile steel butt joint with filler wire is developed. A large number of orthogonal experiments and single factor experiments are conducted. And then effects of heat input. defocused distance, butt joint gap, material of filler wire, wire feeding speed and other parameters to the welding process are analyzed. After welding experiments, tensile strength, SEM fractography of tensile fracture surfaces and microstructure are detected to analyze the performance of weld. According to the experiment data, characteristics of weld fracture surfaces and cross session of different tensile strength are obtained.