Laser cutting is one of the most advanced material processing methods, utilizing a focused high-power beam of light. While the process may seem straightforward, it involves a series of complex physical phenomena that determine the quality and efficiency of cutting. In this article, we will analyze in detail the key mechanisms occurring during the interaction of the laser beam with the material.
Mechanism of Melting and Vaporization of Material
Radiation Absorption
When the laser beam strikes the surface of the metal, part of the energy is reflected, while another part is absorbed by the material. The absorption coefficient depends on:
- The wavelength of the laser radiation
- The temperature of the material
- The surface condition (roughness, presence of oxides)
- The angle of beam incidence
The absorbed energy transforms into heat, causing a localized increase in the material’s temperature. Notably, as the temperature rises, the absorption coefficient also increases, leading to a phenomenon of positive feedback.
Phase Transitions
In the laser beam interaction zone, the material undergoes sequential phase changes:
- Heating to the melting point
- Solid-liquid phase transition (melting)
- Heating the liquid to the boiling point
- Liquid-gas phase transition (vaporization)
The speed of these transitions depends on the power density of the laser beam and the thermophysical properties of the material. At very high power densities, direct transition from solid to gas (sublimation) can occur.
Formation of the Cutting Kerf
Mechanism of Kerf Formation
The formation of the cutting kerf is a dynamic process that can be divided into the following stages:
- Initiation – localized melting and partial vaporization of the material
- Development – removal of molten material by the assist gas stream
- Stabilization – formation of a channel with a relatively constant cross-section
The kerf geometry is influenced by:
- Laser beam parameters (power, energy distribution)
- Cutting speed
- Pressure and type of assist gas
- Material properties
Hydrodynamics of the Process
Complex flow phenomena occur within the cutting kerf, including:
- Movement of molten metal under gas pressure
- Formation of eddies and turbulence
- Interactions between liquid and gaseous phases
- Temperature and surface tension gradients
Formation and Control of Dross
Mechanism of Dross Formation
Dross forms due to:
- Insufficient removal of molten material
- High liquid viscosity
- Improper gas pressure
- Excessive cutting speed
The structure of dross depends on:
- Physicochemical properties of the material
- Process parameters
- Cooling conditions
Methods for Dross Control
Minimizing dross formation can be achieved by:
- Optimizing process parameters
- Proper selection of assist gas
- Controlling the flow dynamics within the kerf
- Using specialized nozzles
Heat-Affected Zone (HAZ)
Characteristics of HAZ
The heat-affected zone is the area of the material where structural changes occur due to the thermal cycle. Its size and properties depend on:
- Laser power
- Interaction time
- Thermal conductivity of the material
- Phase transitions in the solid state
Impact on Material Properties
In the heat-affected zone, the following may occur:
- Microstructural changes
- Variations in hardness
- Formation of residual stresses
- Modifications of mechanical properties
Conclusion
Understanding the physical phenomena occurring during laser cutting is crucial for optimizing the process and achieving high-quality products. The complexity of interactions between the laser beam, material, and assist gas requires careful selection of process parameters and consideration of material properties. Further development of this technology will involve a deeper understanding and control of the described phenomena.
References
- Steen, W. M., & Mazumder, J. (2010). Laser Material Processing. Springer.
- Ready, J. F. (2001). LIA Handbook of Laser Materials Processing. Laser Institute of America.
- Ion, J. C. (2005). Laser Processing of Engineering Materials. Elsevier.
- Pro Metal Form (2025). Physics of Metal Laser Cutting Processes.
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metal processing
