Abstract. In order to prevent humping defects in high speed laser welding, relationship between humping tendency and welding parameters such as laser power, welding speed and shielding gas blowing direction is studied in this paper. It is found that hump will appear periodically when the welding speed exceeds 21m/min. humping tendency is not sensitive to the varieties of laser power but becoming obvious with the increase of the welding speed. The humping tendency is less obvious when gas blows backward instead of forward. The cross-section morphology characteristic of humping is observed. Rayleigh instability model is used to explain the forming mechanism of humping and the relationship between process parameters and humping tendency in high speed laser welding process. It is found that the potential mechanism of humping phenomenon is the break-up of liquid column due to surface tension. When the length-to-width ratio is less than π, humping can be suppressed. To raise the temperature of weld pool can prevent the liquid metal from cooling too fast and is good for liquid metal spreading, thus the humping is suppressed as well.
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