Electro-magnetic Force near Anode Boundary and Double Convection in TIG Arc Weld Pool.

Molten pool phenomena of He-TIG arc welding were observed and electro-magnetic force near the anode boundary was considered. A new theory which combine the anode area, electro-maganetic force, surface tension and convection was developed.(1) On the bounadary of bright area, inner zone, was found floating slag patches, that means it is the colliding line of out- surface flows.(2) The boundary was found to be a specific line on which e-m force is maximum and its direction changes abruptly, under simple asuumtions and more elaborate one of Sozou and Pickering.(3) If the anode area coincides with inner area, the followings were considered.1 Radial surface flow is not hindered by weak e-m force at the center.2 Flow is suppressed near the anode boundary by the strong inward e-m force, and builds up high pressure.3 Underward e-m force concentrates near the boundary of dual convection.4 The liquid outside of anode is cold and is adsorbed, and desorption yields inward flow.5 1-4 effects collaborate to drive both radial-inside and axial-outside flow.6 R-A type binary convection and its penetration pattern was reasonably explained well through anode area.(4) Various factors influencing anode area were considered.