Analysis of transient behaviors of keyhole during 304 stainless steel laser welding

FENG Yan-zhu, GAO Xiang-dong, PENG Cong,
ZHANG Yan-xi, GUI Xiao-yan, YOU De-yong

(Guangdong Provincial Welding Engineering Technology Research Center,
Guangdong University of Technology, Guangzhou 510006, China)

Abstract: Aiming at the difficult observation of the keyhole transient behavior during laser welding，a three-dimensional model coupled with the molten pool and keyhole transient behaviors was established to investigate the keyhole transient behaviors during 304 stainless steel laser welding. A ray-tracing heat source was employed to describe the laser energy distribution in the model. At the same time, a variety of physical factors were taken into account such as fluid flow, heat of evaporation, Marangoni shear stress, recoil pressure and surface tension. Moreover, the 304 stainless steel laser welding experiment was carried out to validate the proposed model. The geometry of the cross-section of simulated weld was good consistent with the experimental result, showing that the proposed model can reflect the process of laser welding. Based on the simulated images, the characteristics of keyhole on the surface and vertical section of weldment were extracted to analyze the transient behaviors of keyhole. The results indicate that the transient behaviors of keyhole are affected by the bubbles, the area of the keyhole on the vertical section increases as the bubble breaks. The opening length of the keyhole on the upper surface of the weldment is related to the inclination angle of the rear part of the keyhole. The changes of the keyhole area on the vertical section and the length of the keyhole are larger compared with the width of keyhole.

Key words: 304 stainless steel; laser welding; numerical simulation; keyhole transient behavior