Automatic control of penetration by monitoring oscillation of the molten pool in TIG welding of thin steel plates

In automatic butt welding of relatively thin plates, it is important to control,welding conditions in order to obtain a sound full penetration weld. Especially, it is difficult to obtain a full penetration weld, because the optimum welding condition change with groove conditions, such as gap of groove, shape of groove and so on, Recently, it was reported that there is an intimate relationship between the oscillation of the molten pool and penetration. The frequency of a molten pool decreases drastically with transformation from partial penetration to full penetration. Accordingly, estimation of penetration mode by detecting frequency of the molten pool is attempted, and, furthermore, real-time control for full penetration welding is performed. In this study, the principle of detection of penetration, detection method of molten pool oscillation and control system of welding condition according to the frequency of molten pool oscillation are investigated. As a result of experiment, it is demonstrated that the control system constructed is effective for automatic TIG are welding of thin plates.