Abstract:

:Based on the quasi-stable state heat-transfer control model, a finite difference equation of thermal conduction in laser welding is deduced. Then, the critical temperature of thermal-conduction welding is determined by substituting the thermophysieal parameter （specific heat capacity） for the phase-changing latent heat. Thus, the finite difference equation can be solved with Matlab software, and the temperature field of the weldment is numerically simulated. When the vaporization appears on the material surface, the laser welding is in the critical condition between thermal-conduction welding and deep-penetration welding, and the simulated laser power density equates with the lower critical power density of laser deep-penetration welding at a given welding speed. The lower critical power density of zinc-coated high-strength steel is finally simulated at different welding speeds, and the error between the simulated results and the tested ones is kept below 5%.

Key words: laser weiding, numerical simulation, lower critical power density