Laser cutting of thick sectioned steels using gas flow impingement on the erosion front

An off-axial gas jet has been developed that has the potential to extend the laser's effectiveness by improving the rate at which parts can be machined, producing high-quality surfaces, enhancing the cutting thickness, and adding to the range of materials that can be machined. In laser cutting, an erosion front (liquid–gas region) forms at the momentary end of the cut. Laser heating, exothermic reactions and shear force between the gas flow and the molten layer dictate the material removal rates. The principle of the off-axial gas jet is to provide straight, nonturbulent flow to the cutting erosion front, causing further oxidation reactions and transferring momentum to the molten slag and dross, thereby improving the cutting speed and the quality of cut. The design features of the off-axial nozzle including the shape, size, gas impinging angle with respect to the erosion front, gas pressure and velocity at the nozzle exit, and the distance between the nozzle and the laser beam are described. Successful test results of the off-axial nozzle in the laser cutting of stainless and carbon steels in the laboratory are presented.