Laser-induced infrared characteristic analysis for evaluating joint deviation during austenitic stainless steel laser welding

Abstract

During high-power fiber laser welding, molten pool thermal radiation contains plenty of information which is related to the welding quality. In order to study the relationship between the molten pool characteristics and the welding stability during high-power (10 kW) fiber laser butt joint welding of type 304 austenitic stainless steel plates, the laser beam spot was controlled to move along the weld joint center, parallel to the weld joint with deviation, and cross the weld joint with two different slopes. Under these four different experimental conditions, the infrared radiation characteristics of a molten pool infrared image in laser welding process was investigated based on welding thermal radiation and heat conduction mechanism. An infrared-sensitive high-speed camera was used to capture the molten pool dynamic infrared images during laser welding. The image processing and pattern recognition algorithm were applied to analyze the molten pool characteristics. The molten pool width, keyhole area, keyhole swing, keyhole sharp degree, and position coordinates were defined as the characteristic parameters of a molten pool to analyze the welding stability. It was found that the joint deviation would affect the welding stability which could be reflected by the welding thermal balance, temperature distribution of a molten pool, and the shape of the corresponding infrared thermal image. Welding experimental results showed that the stability of high-power fiber laser welding process could be estimated by the proposed infrared characteristic parameters.