Microcraters and surface quality in laser oxygen cutting of thick steel sheets

Characteristics of microcrater structures on a laser-cut surface and their effect on surface roughness were experimentally studied for sheet thicknesses of 3–16 mm. The size and density of craters increased with the sheet thickness. The number of craters had a nonmonotonic dependence on the cutting velocity and peaked at the optimal cutting velocity, which minimized the roughness of the cut surface. A qualitative explanation of the observed phenomena was proposed. It appears that gas flow in the channel removes droplets from the melt mass, which decreases the melt mass in the lower part of the cut and reduces the roughness.