Laser Welding Melt Pool Control for Large Inter-Sheet Gaps
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Solution Overview
Problem
Laser welding methods face challenges in maintaining joint strength when welding steel sheets with large inter-sheet gaps, particularly exceeding 0.3 mm, as existing techniques either require frequent shim replacement, dedicated clamps, or result in reduced productivity due to low-energy laser irradiation.
Innovation Solution
A laser welding apparatus and method that utilizes a laser oscillator and condenser lens to form and flow a melt pool by scanning the laser, either through driving the condenser lens or a jig, allowing the melt pool to rotate and converge, thereby maintaining joint strength even with large inter-sheet gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If laser welding is performed with large inter-sheet gap (≥0.3mm), then the joint strength declines and weld bead surface sinks, but using shim rollers to maintain gap control requires frequent replacement and reduces productivity
Solution Approach 1:
The invention extracts and eliminates the need for shim rollers by directly controlling the melt pool behavior through laser parameters. The keyhole welding mode inherently manages the gap without requiring external filling materials, thus removing the productivity bottleneck caused by frequent shim replacement.
Solution Approach 2:
The invention changes the laser welding parameters (power, speed, focus position) to achieve keyhole welding mode that can accommodate large inter-sheet gaps. By optimizing these parameters, the melt pool maintains stability and penetrates through the gap effectively without requiring mechanical gap control devices.
2Manufacturing precision
If laser tack welding is performed alternately with welding sites using a clamp, then gap control is improved, but a dedicated large-size clamp is needed and productivity is reduced
Solution Approach 1:
The invention replaces the mechanical clamp system with a laser-based control system. By using laser keyhole welding with optimized parameters, the process achieves both gap control and welding in a single operation, eliminating the need for separate clamping and tack welding steps.
3Manufacturing precision
If first laser irradiation is performed in defocused state to melt upper sheet and form protrusion, then gap is reduced, but processing time becomes long and productivity declines
Solution Approach 1:
The invention performs preliminary keyhole formation and melt pool stabilization in the first laser irradiation phase, creating the conditions for effective penetration welding. This preliminary action of establishing a stable keyhole allows the second phase to proceed efficiently without requiring additional gap-reduction operations.
Solution Approach 2:
The invention changes the laser focus position and power parameters during the two-phase process. In the first phase, the laser is focused to create a stable keyhole and melt pool. In the second phase, parameters are adjusted to achieve complete penetration and sound weld formation, reducing total processing time compared to defocused pre-melting methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables welding of steel sheets with inter-sheet gaps up to 1 mm without a decline in joint strength, improving productivity and reducing the need for frequent shim replacement or dedicated clamps.
Implementation Method 1
a laser oscillator that generates laser; and a condenser lens that converges the laser
Implementation Method 2
applying the laser to the plurality of sheets superposed together so as to form a melt pool
Implementation Method 3
a condenser lens that converges the laser
Implementation Method 4
converges the laser generated by the laser oscillator
Implementation Method 5
forming a melt pool in the plurality of sheets by applying the laser to the plurality of sheets
Implementation Method 6
form a melt pool in the plurality of sheets superposed together by applying the laser
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A laser welding apparatus generates laser by a laser oscillator, converges the laser by a condenser lens, and applies the laser to an upper sheet (101) and a lower sheet (102) superposed together so as to weld the upper sheet (101) and the lower sheet (102) to each other. According to this apparatus, by laser irradiation, a melt pool Y is formed in the upper sheet (101) and the lower sheet (102) superposed together. Furthermore, by laser irradiation, the melt pool Y is caused to flow, and the upper sheet (101) and the, lower sheet (102) are welded together.