High‐speed micro‐grooving of metal by angled irradiation of single‐mode CW fiber laser

Laser micro‐grooving has excellent potential to improve the surface properties of metals. In this study, high‐speed micro‐grooving of the surfaces of mild steel SS400 and aluminum alloy A1050 was investigated using a single‐mode continuous‐wave fiber laser with an average power of 200 W. Experiments were conducted at laser beam scanning speeds of 1 to 6 m/s. The incident angle of the laser beam in the plane perpendicular to the scanning axis was varied from 0 to 60°. A relatively deep groove (approximately 30 μm in depth) and a high upheaval (10 μm in height) were formed along the scanning line at an incident angle of 45° on the SS400, whereas only shallow grooves were formed on A1050. The micro‐groove formation mechanism was discussed on the basis of high‐speed camera observation, groove shapes, and the thermophysical properties of the metal. Asymmetric molten metal flow and solidification around the keyhole are thought to play important roles in micro‐groove formation. Although the laser irradiation conditions must be optimized according to the thermophysical properties of the material, angled laser irradiation has the potential to effectively form micro‐grooves.