Numerical simulation of wire temperature field for prediction of wire transfer stability in laser hot wire welding

With preheating wire by resistance heat, laser hot wire welding improves process stability and wire deposition efficiency, which gives broad potential applications in surfacing and narrow gap welding. It is a critical issue to control the temperature field of preheated wire in this process. Whether the temperature is so high that the wire fuses outside molten pool or so low that the wire cannot melt timely in the molten pool, results in poor wire transfer stability and bad weld formation. This paper is purposed to calculate the wire temperature field for the prediction of wire transfer stability under various welding parameters. A transient heat conduction model is set up. Heat sources of the wire include resistance heat and reflected laser, and the heat source of molten pool is laser. All heat exchanges are considered as the heat boundary conditions. The calculated temperature of wire part outside the molten pool is verified by infrared ratio temperature measurement. The calculated temperature of wire part in the molten pool is verified by measurement of the molten pool size. Combining the wire temperature field and welding process observed by the high speed imaging, the temperature criterions of wire transfer stability are obtained. Thus, numerical simulation of the wire temperature field can be used to predict the wire transfer stability under various welding parameters in laser hot wire welding.