Experimental investigation of hydrodynamics of melt layer during laser cutting of steel

Abstract

In laser cutting process, understanding of hydrodynamics of melt layer is significant, because it is an important factor which controls the final quality. In this work, we observed hydrodynamics of melt layer on kerf front in the case of laser cutting of steel with inert gas. The observation shows that the melt flow on the kerf front exhibits strong instability, depending on cutting velocity. In intermediate range of velocity, the flow on the central part of the kerf front is continuous, whereas the flow along the sides is discontinuous. It is firstly confirmed that the instability in the side flow is the cause of the striation initiation from the top part of the kerf. The origin of the instability is discussed in terms of instabilities in thermal dynamics and hydrodynamics. The proposed model shows reasonable agreement with experimental results.