Influence of laser processing on shape of melted zone and character of thermal cycles in steel

摘要

In this work three-dimensional mathematical model of laser melting of steel is presented. It includes Gaussian source of heat moving along the specimen. Nonlinear relationships between thermal and mechanical characteristics and temperature were applied and the influence of chemical composition of melted material has been also taken into consideration. Results of calculations are shown in the form of graphs illustrating liquid movement in melted zone. It was shown that the melting process is mainly controlled by value and gradient sign of surface tension. For most steels the surface tension is closely connected with sulfur content. Calculations were carried out for three values of sulfur content and two melting velocities. Curves of heating and cooling in laser treated material were calculated basing on numerical solution of equations of mass, momentum and energy conservation in three-dimensional layout. Using results of the work it is possible to explain the microstructure arisen after laser melting.