The convective flows and mass transfer of the alloying material in the steel melt during heating of the substrate by a laser pulse

The present work uses the numerical simulation to analyze the effect of the laser pulse on the distribution of the alloying material penetrating into the substrate from its surface. The iron-sulfur alloy is used as the substrate material. The substrate surface is coated with a layer of the alloying material. The metal is heated and melts under the action of the energy. Under the action of capillary and gravity forces, the convection develops in the liquid pool forming and increasing with time. The alloying material forced by the convective flows, penetrates into the melt depth. Upon the impulse, melt coos down and hardens due to the heat release into the unheated material of the substrate and heat exchange with the ambient medium. Calculation results show that the presence of surface-active substances in the melt influences essentially on the physical processes during the alloying, including the distribution of the injected material which depends on the thermocapillary convection. The distribution of the alloying material occurs only due to the convective flow in the melt. Two possible variants of currents are defined. The presence of a stable centripetal motion on the liquid surface is possible provided that its heating does not exceed the temperature Tkp. In this case, the permeated material has a maximum concentration near the free surface and in the Central part of the molten hole and is virtually absent from its periphery. The melt surface temperature above Tkp contributes to the emergence of several toroidal flows in the liquid and more uniform mixing of the alloying substance.