LASER CUTTING OF THICK SECTIONED STEELS USING GAS-FLOW IMPINGEMENT ONTHE EROSION FRONT

An off-axial gas jet has been developed that has the potential to exte nd the laser's effectiveness by improving the rate at which parts can be machined, producing high-quality surfaces, enhancing the cutting th ickness, and adding to the range of materials that can be machined. In laser cutting, an erosion front (liquid-gas region) forms at the mome ntary end of the cut. Laser heating, exothermic reactions and shear fo rce between the gas flow and the molten layer dictate the material rem oval rates. The principle of the off-axial gas jet is to provide strai ght, nonturbulent flow to the cutting erosion front, causing further o xidation reactions and transferring momentum to the molten slag and dr ess, thereby improving the cutting speed and the quality of cut. The d esign features of the off-axial nozzle including the shape, size, gas impinging angle with respect to the erosion front, gas pressure and ve locity at the nozzle exit, and the distance between the nozzle and the laser beam are described. Successful test results of the off-axial no zzle in the laser cutting of stainless and carbon steels in the labora tory are presented.