Laser-Arc Hybrid Welding: Key Factors for Success

There are many factors that affect the formation of laser-arc hybrid welding, mainly including arc current, laser power, defocusing amount, relative position of the laser and arc, and welding speed. These factors significantly influence the formation of the weld seam and the welding quality.

Arc Current

With a constant laser power, when the current is low, the penetration depth increases with the increase of current. However, when the current is high, the change in penetration depth is not significant and sometimes even decreases. Research on the dual-focus laser-MIG arc hybrid welding process has found that at the same laser power, the penetration depth increases with the increase of arc current.

When the current reaches a certain value, the penetration depth reaches its maximum, but with further increase in current, the penetration depth decreases.

Laser Power

Laser power is the main welding parameter that affects the fusion welding of the hybrid heat source. It greatly influences the formation of the weld seam, especially the penetration depth, which increases with the power. Studies on aluminum/steel laser hybrid welding by Lei Zhen and others have shown that the penetration depth increases with the increase of laser power.

Laser power also affects the width of the fusion zone, but the effect is not very pronounced. Research on the dual-focus laser-MIG arc hybrid welding process indicates that at lower arc currents, the width of the fusion zone increases with the increase of power, but this change is not significant at higher currents.

Defocusing Amount

The defocusing amount has little effect on the stability of the arc and the width of the fusion zone, but it significantly affects the penetration depth. The focal point of the laser beam is defined as zero defocusing when it is on the workpiece surface, positive defocusing when it is above the workpiece, and negative defocusing when it is below the workpiece.

There is usually an optimal defocusing amount that maximizes the penetration depth. In the case of arc and YAG hybrid welding, the best defocusing amount was found to be -1mm.

In the study of stainless steel YAG-MAG laser hybrid welding, it was found that the penetration depth in hybrid welding with the same defocusing amount is twice that of laser welding.

Relative Position of Laser and Arc

The relative position of the laser and arc affects the formation and quality of the weld seam in hybrid welding. Research indicates that when the laser beam is in front and the arc is behind, the surface of the weld seam is uniformly full, whereas when the arc is in front and the laser beam is behind, the weld seam surface exhibits inclined grooves.

Furthermore, in the former case, the hardness of the upper part of the weld seam is lower than the lower part, while in the latter case, the hardness of the upper part is greater than the lower part.

Welding Speed

At a constant laser power, as the welding speed increases, the penetration depth and width of the fusion zone decrease. This is because, at a constant laser power and welding current, as the welding speed increases, the heat input per unit length and time decreases, resulting in less heat spreading to the surroundings and thus less heat available for melting the metal.

Additionally, as the welding speed increases, the arc contracts, leading to a reduction in the heating area of the arc and consequently a decrease in the width of the fusion zone.

Research conducted by the Harbin Welding Research Institute confirmed that the parameters of Na:YAG laser+pulsed GMAW hybrid heat source welding significantly affect the width of the weld seam, with an increase in welding speed resulting in a decrease in the width of the fusion zone.

At a constant laser power, an increase in welding speed leads to a decrease in penetration depth and width of the fusion zone, eventually resulting in shallower penetration or even incomplete fusion. Properly reducing the welding speed can increase the penetration depth, but excessively slow welding speed may cause over-melting of the workpiece, or even burn-through.

Therefore, it is necessary to find an appropriate welding process that meets the requirements of high efficiency while achieving greater penetration depth. Experimental studies on aluminum/steel laser-MIG hybrid fusion-brazing connections have demonstrated that this method can achieve high-speed welding of aluminum/steel, with a maximum welding speed of up to 5m/min.

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