Fibre laser cutting of thin section mild steel: An explanation of the ‘striation free’ effect

This paper presents the results of an experimental and theoretical investigation into the phenomenon of ‘striation free cutting’, which is a feature of fibre laser/oxygen cutting of thin section mild steel. The paper concludes that the creation of very low roughness edges is related to an optimisation of the cut front geometry when the cut front is inclined at angles close to the Brewster angle for the laser–material combination.

► ‘Striation free’ fibre laser cut edges are covered in microscopic striations.
► The lowest roughness mild steel cut edges are produced at intermediate speeds.
► At low speeds melt viscosity increases roughness.
► At high speeds the increased melt flow increases roughness.
► The low roughness striations are inclined at 8–14°, correlating with maximum laser absorption.