Butt Laser Welding of Gapped Metal Sheets With Front and Back Beams
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Solution Overview
Problem
Conventional laser welding methods for butt welding metal sheets with a gap between them result in low energy efficiency due to wasted laser energy passing through the gap, with only 10% to 20% of the energy effectively used for welding, and fail to achieve uniform material properties and mechanical properties equal to the base material.
Innovation Solution
A method involving the simultaneous emission of a first front laser beam, a second front laser beam, and a back laser beam, which create keyholes and melt baths on both metal sheets, with the back laser beam having a larger energy density and volume to efficiently weld the sheets even when they are positioned with a gap, and optionally using a secondary back laser beam to enhance the weld joint quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a standard laser beam is used for butt welding metal sheets with a gap, then the welding process can be performed, but energy efficiency is low because most laser energy passes through the gap without interacting with the sheets
Solution Approach 1:
The laser beam is divided into multiple segments (first front laser beam, second front laser beam, and back laser beam) that act on different regions of the metal sheets. The front beams target the front surfaces while the back beam targets the rear surfaces, ensuring comprehensive energy utilization and preventing energy loss through the gap.
Solution Approach 2:
The welding approach transitions from a single-direction (front-only) laser beam to a multi-dimensional configuration by introducing back laser beams that act from the rear surface. This adds a new dimension (rear surface interaction) to the welding process, ensuring energy is absorbed from both sides of the sheets.
2Reliability
If the laser beam energy is increased to compensate for gap losses, then welding of gapped sheets becomes possible, but the energy waste increases significantly
Solution Approach 1:
Instead of using one high-power beam that loses energy to the gap, the system segments the energy delivery into multiple lower-power beams (front and back) that collectively achieve the required weld quality. Each beam targets specific regions, minimizing energy loss while maintaining reliable welding.
Solution Approach 2:
Different regions of the metal sheets receive different laser beam configurations tailored to their specific needs. The front surfaces receive front laser beams while the rear surfaces receive back laser beams, creating localized energy delivery that optimizes weld quality without excessive energy waste.
3Stability of the object's composition
If three laser beams are used to create a single weld pool with good material mixing, then uniform material properties are achieved, but energy efficiency remains low for gapped sheets
Solution Approach 1:
The welding system segments the melt pool creation process by using separate front and back laser beams that act on opposite surfaces. This segmentation allows each beam to efficiently deposit energy locally without significant loss to the gap, while the thermal conduction and fluid flow still achieve uniform material mixing in the final weld pool.
Solution Approach 2:
The system changes the spatial parameters of energy delivery by introducing back laser beams from the rear surface, in addition to front beams. This parameter change (adding rear surface illumination) improves energy efficiency for gapped sheets while maintaining the material mixing quality through controlled thermal and fluid dynamics in the weld zone.
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
This approach significantly improves energy efficiency and weld quality by ensuring that the laser energy is effectively absorbed and utilized, reducing the gap between the sheets through thermal expansion and surface tension, and achieving mechanical properties comparable to the base material, while maintaining a solid or liquid phase region between keyholes to prevent energy loss.
Implementation Method 1
an important part of the energy of the laser beam is wasted since it passes through the gap and therefore does not interact with the sheets
Implementation Method 2
reducing the gap between the sheets through thermal expansion
Implementation Method 3
reducing the gap between the sheets through thermal expansion and surface tension
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A method of butt laser welding two metal sheets (2, 4) comprises : providing a first metal sheet (2) and a second metal sheet (4), butt welding the metal sheets (2, 4) along a direction of welding, the butt welding step comprising simultaneously emitting : a first front laser beam (12) creating a first front spot (18) at the intersection with the first metal sheet (2), and generating a first front keyhole in the first metal sheet (2) at the first front spot (18), a second front laser beam (14) creating a second front spot (20) at the intersection with the second metal sheet (4), and generating a second front keyhole in the second metal sheet (4) at the second front spot (20), a back laser beam (16) creating a back spot (22) on the first and second metal sheets (2, 4), and generating a back keyhole in the first and second metal sheets (2, 4) at the back spot (22), the first and second front laser beams (12, 14) and the back laser beam (16) being configured in such a manner that at each moment in time, a solid phase region and/or a liquid phase region of the metal sheets (2, 4) remains between the first front keyhole and the back keyhole and between the second front keyhole and the back keyhole.