WE Colloquium: Yi Huang, Laser as direct and indirect source in welding process

Abstract

Laser, because of inherent advantages, is widely used in the industry, especially metal welding and joining. By deep exploring the principle of laser beam, it can be used as indirect and direct source to enhance or execute welding process. Traditionally considered as direct thermal source, laser can also be adopted as force source. To this end, laser enhanced GMAW was developed to realize this concept. Laser recoil pressure force was identified as the main auxiliary force to detach droplet. The electromagnetic force needed to detach droplets, thus the current that determines this force, is reduced. The undesired dependence of the metal transfer on the current is decoupled such that the current may be freely chosen to control the weld penetration and weld pool without restrictions as in conventional GMAW due to the need for metal transfer. Wire feed speed, arc voltage, and laser intensity were identified three major parameters that affect the laser enhanced metal transfer process and a systematic series of experiments were designed and conducted. The behaviors of the laser enhanced metal transfer process under the effects of these parameters were analyzed using the established physics of metal transfer. Pulsed laser and/or weld current could also be utilized to better control droplet detachment. Desired heat input and current/arc pressure waveforms may thus be both delivered and controlled by GMAW through laser enhancement. Laser recoil pressure force was estimated based on the difference of gravitational force with and without laser pulse, and the result was with an acceptable accuracy. A nonlinear model based on the physical analysis of laser enhanced GMAW was established to simulate the dynamic metal transfer in this novel process, and the results agree with the experimental one.

Laser beam welding which utilizes heat as direct source is widely used in ultra high strength steel welding. Martensitic steel was selected to build vehicle body structure frame because of its excellent material characteristics in some vehicles, and laser welding was chosen as the joining process. Trailing impact rolling and intensive cooling were adopted to reduce hot cracks and improve weld property as the strength weakness in the heat affected zone was too significant. The weld zone can be controlled at the reasonable range to achieve good assembly performance to meet design requirements.

Bio

Dr. Yi Huang received his PhD Degree in Electrical and Computer Engineering (Welding Major) from the University of Kentucky, Lexington, Kentucky in 2011, and M.S. in Materials Engineering (Welding Major) and B.S. in Welding Engineering from the State Key Laboratory for Advanced Welding and Joining, Harbin Institute of Technology, Harbin, China, in 2006 and 2004, respectively. His major research interests include novel welding and joining processes development for advanced materials, welding and joining metallurgy especially for microjoining, and analytical modeling of materials joining process, and dissimilar material welding and joining.

Dr. Huang is currently employed as a Staff Advanced Manufacturing Engineer at Tesla Motors, Fremont, CA. He leads Welding and Joining R&D team for exploring novel welding and joining processes for current and future vehicle models, and welding and joining processes selection and qualification, design, cost control, equipment introduction and launching for body in white, closure in white, battery enclosure, seat framing, and other structure assembly. Dr. Huang has published more than 20 papers in peer-reviewed journals and conferences. He was the recipient of the A. F. Davis Silver Medal Award for Machine Design in 2011 and Charles H. Jennings Memorial Awards in 2012 from American Welding Society (AWS), and Henry Granjon Prize for Joining and Fabrication Technology from International Institute of Welding in 2012.