アルミニウム合金薄板の部分溶込みおよび貫通スポット溶接における適応制御

抄録

A new procedure of in-process monitoring and adaptive control for stable formation of laser spot lap welds has been developed with the objectives of producing sound partial- and full-penetration welds without through-holes and swell in A3003 aluminum alloy sheets, respectively. In the case of the formation of partial-penetration welds, the reflected laser beam and the radiated heat from the welding area were effectively utilized as in-process monitoring signals in detecting melting and though-hole formation in the upper sheet during laser irradiation. Laser pulse duration and peak power were controlled at every 0.15 ms interval during spot welding on the basis of the heat radiation signal detecting the though-hole. In the full-penetration welds, spot welding was performed at low laser power density to reduce the swell of joint part. Then the concavity level of a weld fusion zone increased remarkably with an increase in the pulse duration. Therefore, the laser pulse duration was controlled at 0.15 ms intervals on the basis of the total intensity of heat radiation so as to produce a satisfactory spot weld fusion zone. As a result, fully penetrated welds of desirable sizes with the reduced swells were consistently produced in all 20 samples. These results proved the effectiveness of in-process monitoring and the availability of adaptive control.