A transport theoretical model of the keyhole plasma in penetration laser welding

Abstract

In laser welding with high laser intensities a hole is formed in the material, the so-called keyhole. In this keyhole a plasma is detected, which is characterized by high charge densities and high pressure as well as being influenced by the boundary of the keyhole. The authors describe the transport of the laser power into the material by the plasma for a CO2 laser and iron. They set up a system of stationary transport equations for the ions, electrons and non-excited neutrals, which contain convective transport and heat flux. The boundary conditions take into account the evaporation of neutral atoms from the hot keyhole surface and the transition from the quasineutral presheath plasma to the sheath plasma. With the incident laser power as input parameter the authors obtain the radial variation of the hydrodynamic variables and quantities like the degree of ionization, the electron temperature and the fraction of absorbed laser power.