Dominant factor of HT780 non-load-carrying T-joint fatigue strength using laser arc hybrid welding and quality control

ABSTRACT

The study intended for clarify that dominant factors of fatigue strength of T-joint which welded by laser arc hybrid welding. Fatigue test has been conducted using five types of HT780 T-joints fabricated under different welding conditions respectively. Dominant factors for fatigue strength of T-joint are flank angle and curvature at toe of T-joint fillet. The fatigue strength is increasing inverse proportional to flank angle and proportional to curvature at toe. Heat-filler feeding ratio affects flank angle and curvature at toe. The former would be decreased and later should be increased by heat-filler feeding ratio increasing. In the study, fatigue strength of the one type of joint shall be recognized as JSSC fatigue strength class D. All types of joint in the study can be dealt as at least JSSC fatigue strength class E. Flank angle of these joints are smaller than 47 degree and curvature of toe are larger than 1.3mm. These quantitative results of the study are very useful for quality control of practical fabrication. That secures the fatigue strength of non-load-carrying T-joint welded by laser arc hybrid welding.

KEYWORDS:

• Laser-arc hybrid welding
• T-joint
• fatigue strength
• heat-filler feeding ratio
• flank angle
• curvature at toe of fillet weld

Acknowledgments

This study includes some of the results of the PJ Research: ‘Research activities of the ferrous metals improved strength and mechanical capabilities research and development team’ project under the auspices of the Japan Development Center for Metals (JRCM), for which we would like to express our gratitude.