In situ tensile of ultra-narrow gap laser welded joint of bainitic steel

ABSTRACT

Ultra-narrow gap laser welding (ultra-NGLW) is an advanced welding technology for thick bainite steel with a welding gap of only 4 mm. We studied the failure mechanism of the tensile fracture of ultra-NGLW joints of bainitic steel via in situ tensile tests. The tests show that cracks for all micro-zone specimens propagated along the tensile direction at 42°∼45°. Further analysis of the crack tips by Electron Back Scatter Diffraction showed main cracks along directions with high Schmid Factors (SF >0.44), and micro-cracks were found on the grain boundaries of (111) and (101) grains. It was revealed that the wire-filling zone and heat-affected zone were mainly intergranular expansion, whereas in the no filling zone, the crack propagation was transgranular.

KEYWORDS:

• In situ tensile
• ultra-narrow gap laser welding
• crack propagation
• Schmid Factor
• bainitic steel

Acknowledgements

The authors gratefully acknowledge the financial support from the Development Program of China (grant number 2016YFB1102100). We also express sincere thanks to Dr Yong Chen for his helpful discussion.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Development Program of China [grant number 2016YFB1102100].