Heat and Mass Transfer and Their Effect on Penetration Shape in Stationary TIG Arc Weld Pool

概要

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The importance of convective heat transfer in the weld pool has been widely recognized in relation to the penetration shapes of base metal. The main causes associated with a streaming in molten pool are the electromagnetic, force, buoyancy force, surface tension and aero dynarnic drag force. Therefore, in this work, authers have paid special attention to the importance of convectional heat transfer in the weld pool and the onode size or heat source size under the same heat input, or same current value. A finite difference method was employed to solve the above-mentioned mechanisrn. The results obtained were as follows : 1) When are length is short, the velocity field induced by outward surface shear stress consists of two flow loops of opposite directions in the molten pool, which leads to a comparatively deep weld shape. 2) In case of short arc length and positive temperature coefficients of surface tension, surface tension is predominant. Accordingly, penetration shape is deep. 3) In case of long arc tength, aero dynamic drag force is predominant, which lead, to a 'shallow' center and a 'deep' peripheral penetration. 4) The melting efficiency of the weld pool is the highest when the penetration shape turns out hemispherical, and both deep and shallow penetration welds have a lower melting efficiency.
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1993-04-01