Energy mechanism during machining process by high-power continuous CO2 laser

Abstract.

The high-power continuous CO₂ laser (4 KW) can provide an energy capable of causing melting or even, with special treatment of surface, vaporizing an XC42 - iron sample. During the laser–metal interaction, the energetic machining mechanism takes place according to the following assumptions:

Laser energy absorbed by metal is maximal for a p-polarization. The melting front precedes the laser beam. The beam interacts with a preheated surface whose temperature is near the melting point. In such conditions one finds that mean average absorptive power (A), calculated through Maxwell’s equations at fusion temperature, is around 25%, which enables us to calculate the laser energy absorbed by the metal. The available thermal models provide a lot of information concerning thermal diffusion but are unable to describe the physical process of the groove. Hence practical information required for industrial applications cannot be obtained. So in this work we have established a model able to calculate the characteristic parameters of the groove (or cut) as a function of laser energy and beam impact diameter (D). This model is based on writing down the balance of exchanged heat during the time of laser–material interaction (Δt). This new procedure makes it possible to determine the machining parameters (laser power P, impact diameter D, and machining speed V) which one has to use during the machining process in order to implement an optimum groove (or cut) with predetermined characteristics (width L_s, and groove depth P_r).