Processing of metals by pulse laser radiation of millisecond range of duration

Dynamic parameters' dependencies of laser pulses shape, divergence of beam and aperture angle of the laser from vapour-gas channel growth and melting zone depth were detected. The significance of melt buffer volume for neutralization of liquid metal ejection from the molten zone during deflection of the melt surface was studied and experimentally proved. The effect of heat source self-concentration on the bottom of expanding vapour-gas channel was experimentally obtained for the first time. Rotational flow of the melt was detected. This flow was identified as Rayleigh-Taylor instability. The presence of extremum for dependence of melting depth from aperture angle b was experimentally found. It was also found that maximal value of the melting depth can be obtained if the aperture angle 2b is equal to 75 mrad. The melting depth, which is more than 6 mm, at the energy less than 20 J for pulse laser radiation of millisecond duration was obtained for the first time. This result exceeds by the factor of 3 the value, which was previously believed as maximal.