Abstract
The importance of convective heat transfer in weld pool has been widely recognized in relation to the penetration shapes of base metal. The main causes that associate streaming in molten puddle are the electromagnetic force, surface tension, airodynamic drag force and buoyancy force, but quantitative effect of each factor has not been well analysed.
The author have, therefore, conducted numerical analyses of the fluid flow induced by surface tension in order to clarify the independent contribution of thermocapillary effect to the liquid motion in weld pool. A simplified model was employed where the liquid was contained in a hemispherical basin of constant wall temperature and the liquid center was kept different but constant temperature. Under the assumption of laminar flow in a basin, the behaviours of stream lines, velocity and temperature distributions in a pool were obtained. The result gained were as follows:
1) The temperature distributions on the free surface as well as the heat flux distributions on the basin wall became quite different from those of conductive heat transfer as the convection grew stronger in the basin.
2) The effect of natural convection in ordinary weld pool whose size is in the order of centimeter (10°cm) could be reasonably neglected.
