Melt flow and microstructural characteristics in beam oscillation superimposed laser welding of 304 stainless steel

• Published in: Journal of manufacturing processes Vol. 50; pp. 629 - 637
• Main Authors: Li, Junzhao, Sun, Qingjie, Liu, Yibo, Zhen, Zuyang, Sun, Qi, Feng, Jicai
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2020
• Subjects: Beam oscillation; Laser welding; Melt flow; Microstructure; Melt flow; Microstructure; Laser welding; Beam oscillation
• ISSN: 1526-6125; 2212-4616
• DOI: 10.1016/j.jmapro.2019.12.053

[Display omitted] •Beam oscillation technology was applied to butt welded 304 stainless steel.•The effects of beam oscillation on weld morphology and weld defects were investigated.•The beam oscillation can increase the solidification rate, reduce the size of molten pool and refine grain size.•The content of ferrite was reduced and more skeletal ferrite was observed in the fusion zone and mechanical properties were increased. The effects of laser beam oscillation parameters on weld morphology, microstructure and mechanical properties of 304 stainless steel are investigated. The weld depth was increased at lower oscillation amplitudes with high frequency, while greatly decreased at higher oscillation amplitudes. The undercut defect was inhabited by beam oscillation. The periodical movement of laser beam caused a formation of vortex and some turbulence at the front of molten pool, which could increase the solidification rate and reduce the size of molten pool. Increasing beam oscillation frequency may disturb weld pool solidification more severely and cause more significant grain refinement. The growth direction of columnar crystal in the weld was changed. The content of ferrite was reduced and more skeletal ferrite was observed in the fusion zone in the case of beam oscillation. The microhardness and tensile strength value of beam oscillation welded joint was slightly increased than that of conventional welded joints. The ductile fracture mode with dimples was observed for all welded joints.