Li Liqun

Model of laser-TIG hybrid welding heat source

The welding mechanism of laser-TIG hybrid welding process is analyzed. With the variation of arc current, the welding process is divided into two patterns: deep-penetration welding and heat conductive welding. The heat flow model of hybrid welding is presented. As to deep-penetration welding, the heat source includes a surface heat flux and a volume heat flux. The heat source of heat conductive welding is composed of two Gaussian distribute surface heat sources. With this heat source model, a temperature field is calculated. The finite element code MARC is employed for this purpose. The calculation results show a good agreement with the experimental data.

Study of welding characteristics in CO2 laser-TIG hybrid welding process

In this paper, 304 stainless plates with 4mm thickness were welded with CO2 Laser-TIG paraxial hybrid welding. The arc shapes and weld characteristics were studied under different energy ratios between laser and arc. The experimental results indicated that hybrid welding exists two welding mechanisms---deep penetration welding and heat conductive welding. Because of the action of keyhole induced by laser, TIG arc was fixed and compressed, and the current density and the penetration depth increased dramatically, which took on the weld characteristic of deep penetration welding. When current increased to some degree, the keyhole induced by laser disappeared and arc expanded abruptly, it caused the penetration depth rapidly drop, which took on the weld characteristic of heat conductive welding. Furthermore, the effect of distance from laser to TIC arc and pulsed laser on hybrid welding characteristics were also studied.In this paper, 304 stainless plates with 4mm thickness were welded with CO2 Laser-TIG paraxial hybrid welding. The arc shapes and weld characteristics were studied under different energy ratios between laser and arc. The experimental results indicated that hybrid welding exists two welding mechanisms---deep penetration welding and heat conductive welding. Because of the action of keyhole induced by laser, TIG arc was fixed and compressed, and the current density and the penetration depth increased dramatically, which took on the weld characteristic of deep penetration welding. When current increased to some degree, the keyhole induced by laser disappeared and arc expanded abruptly, it caused the penetration depth rapidly drop, which took on the weld characteristic of heat conductive welding. Furthermore, the effect of distance from laser to TIC arc and pulsed laser on hybrid welding characteristics were also studied.

The characteristic of laser forming aluminum sheet under consecutive irradiations

This paper has studied the laser forming process of pure aluminum sheets by a Nd:YAG laser with 2kw maximum power. Based on the Temperature Gradient Mechanism, the change of bending angle, mechanical behavior and the thicken effect were investigated under consecutive irradiations. The reducing bending often observed after a few irradiations was related to the thickening of heated zone. When the thickness of sheet metal up to some degree and almost has no change, the increment of bending angle begin appear the rising trend. It was concluded that gradual thickening reduced subsequent bendability. Moreover, empirical equations for predicting thickness of heated zone were derived, which can be used for predicting the variation of bending angle with number of irradiations.This paper has studied the laser forming process of pure aluminum sheets by a Nd:YAG laser with 2kw maximum power. Based on the Temperature Gradient Mechanism, the change of bending angle, mechanical behavior and the thicken effect were investigated under consecutive irradiations. The reducing bending often observed after a few irradiations was related to the thickening of heated zone. When the thickness of sheet metal up to some degree and almost has no change, the increment of bending angle begin appear the rising trend. It was concluded that gradual thickening reduced subsequent bendability. Moreover, empirical equations for predicting thickness of heated zone were derived, which can be used for predicting the variation of bending angle with number of irradiations.