固定 TIG アークによる立向溶接現象 : アーク溶接現象に関する界面張力理論(第 12 章)

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With the aim to study the mechanism of vertical welding in the light of "interfacial tension theory" hitherto reported, the authors have studied phenomena of a simplified vertical welding, using a fixed TIG torch against a vertically set mild steel plate. Following are the conclusions obtained by putting together the various facts, observed through the high speed cine-photography and the rapid blow technique applied to the steel plate in the course of welding, with the interfacial tension theory. 1) From the measurement of the penetration angles and bead angles at the edge of the penetration surface, the contact angle of the molten metal of mild steel was estimated approximately to be 60 degrees, assuming static equilibrium of molten metal drop, and this value conforms well to the observed configuration of the molten metal drop during welding. 2) Smooth weld bead with no undercut is generally obtainable when the molten metal drop is completely confined within the penetration surface, leaving no exposed metal surface. The authors discovered that the indirect melting action of the arc plays the most essential role in keeping the upper penetration angle large enough for the confinement of the metal drop. 3) Change of the type of the penetration and moving pattern of small floating particles on the molten pool seems to show that the arc coveres almost the whole surface of the molten pool at the start, forming a 'peripheral type' penetration, and later, the arc is limited to the central part of the pool resulting in 'Pa' type penetration (typical penetration of paraffin plate heated by a spot heat source.) At the final stage of welding, decreased upper penetration angle results in slipping of the molten metal drop into, and then out of, the penetration surface, leaving the exposed metal surface. 4) Three types of the exposed metal surface, from which the bulk of the molten metal was expelled, were observed in this experiment. 1st type surface is the 'slipping solidification' surface, and 2nd is the one covered partially by small metal droplets and 3rd is the one coverd completely by a thin film of the molten metal. Occurrence of either type of exposed surface depends on the strength of the indirect and direct melting action and blasting force of the plasma jet.
社団法人溶接学会の論文
1969-02-25

固定 TIG アークによる立向溶接現象 : アーク溶接現象に関する界面張力理論(第 12 章)

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