Dynamic distribution characteristic of temperature field and weld morphology control in pulsed microplasma arc welding ultra-thin sheets

Based on the numerical calculation of pulsed microplasma arc welding (P-MPAW) 100 μm ultrathin sheets, dynamic distribution characteristic of weld pool temperature field under dynamically loading the actual heat source and influence of pulse parameters on it were studied. Effect of pulse parameters on weld morphology was investigated and the numerically calculated results were verified. In addition, the relations between the matching of pulse parameters and welding speed with the weld morphology were discussed. The results were as following. Firstly, the dynamic variations of temperature distribution are characterized with cyclical fluctuation and inertia. The higher the pulse frequency or the smaller the ratio of peak current to base current, the stronger the fluctuating amplitude and the more intense the inertia of temperature variation corresponding to the changes of pulsed current are. Secondly, there are two forms of weld morphologies with pulsed current, continuous weld and non-continuous weld morphologies. These two different weld morphologies are attributed to the matching of welding speed, seam length during peak current period and pulse parameters. Finally, the continuity of experimentally obtained weld morphology was well explained by the numerically calculated results about the ratio of pulse period to lasting time when the maximum weld pool temperature is higher than the material melting point.