Keyhole stability during laser welding—Part II: process pores and spatters

Abstract

Spatters and pores that occur during laser deep penetration welding are unwanted defects that make post processing necessary. Therefore, these defects need to be avoided. The origin of pores and spatters are assumed to be in the process dynamics, especially the highly dynamic vapor channel. The keyhole is assumed to be responsible for producing these defects. Based on keyhole calculations from Part I, in this paper, calculated keyhole properties are correlated to pore and spatter formation observed during experiments. Spatters are recorded using a high speed camera and a spatter detection routine for measuring spatter speed, size and number per time. Pore number per time and pore sizes are detected using X-ray imaging after welding. Temporal spatter and pore characteristics can be correlated to dynamic values of the keyhole. The analytical model can predict spatter and pore formation depending on local frequencies and amplitudes in the keyhole. When using different beam profiles, extremely high local frequencies of the Top Hat beam at smaller keyhole dimensions seem to lead to an increased spatter and pore formation. The spring coefficient can be used as an indicator to predict spatter and pore characteristics.