At the present time the methods of the gas assisted laser cutting (GALC) of the different steels (alloyed and non-alloyed) and also of non-ferrous metals, such as Al and Ti, using one of the inert gases (nitrogen, argon, helium) or the active gas (oxygen) or air as assist gas are widely spread. However these cutting methods have the series of essential shortcomings. Heaving performed the theoretical and practical investigations of the mentioned methods we concluded that the great interest is the use of mixtures containing inert gases and oxygen with controlled concentration. The application of such assist gas mixtures permits the laser cutting velocity to be increased as against the use of pure inert gas. The chose of optimal oxygen concentration leads to reduction of expensive gases consumption and makes the cutting process cheaper.
The luminescent method was used to measure the spectrum of turbulent pulsations of gas density in fast- axial flow CO2 laser with radio-frequency discharge input. It is shown that gas density pulsations increase through gas discharge along gas flow axes. In continuous-wave fast-axial flow (FAF) CO2 laser there is subsidiary deterioration of quality of active medium due to intrinsic turbulence intensified by gas discharge energy input.
Gas assisted laser cutting (GALC) is accompanied by formation of heat affected zone (HAZ). A part of laser beam power is spent on this. Thermal losses cannot only decrease GALC efficiency, but cause thermal deformations of the treated material. The temperature measurement of samples heating under GALC were performed. The dependence of the samples temperature on cutting velocity was obtained under blowing by nitrogen and oxygen. In the first case dross was formed, the contribution of its crystallization enthalpy into plate heating was taken into account in estimations of GALC energy balance. As a result, the limiting physical value of heat losses was obtained, and its dependence on velocity was plotted. It has been revealed that a portion of thermal losses at low cutting velocities was essential. A qualitative physical model was suggested which gave a satisfactory description of the obtained experimental results. The GALC conditions for minimum thermal losses were defined.
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