In-process monitoring and adaptive control for stable production of sound welds in laser microspot lap welding of aluminum alloy

A new procedure of in-process monitoring and adaptive control has been developed for laser microspot lap welding of A3003 aluminum alloy sheets of 0.1 and 1 mm in thickness. The objective is to consistently produce sound laser partial-penetration lap-joint welds. It was revealed that the reflected laser beam and the radiated heat from the welding area were effective as in-process monitoring signals in detecting melting, keyhole generation, and through-hole formation in the upper sheet during laser irradiation. Laser pulse duration and peak power were controlled at every 0.15 ms interval during the laser spot welding on the basis of the heat radiation signal detecting the through-hole. Upon investigation of 20 samples, 4 nonbonded welds with holes were formed under conventionally used conditions. On the other hand, sound partially penetrated spot welds were produced in all 20 samples subjected to laser lap welding under the proposed in-process monitoring and adaptive control.