Superposed YAG Laser Welding for Thick Copper
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Solution Overview
Problem
Conventional laser welding methods using YAG lasers face challenges in achieving deep penetration and reproducibility, particularly with thick copper plates, due to inadequate optical coupling and short interaction time with YAG second harmonic Q-switched laser light.
Innovation Solution
A method and apparatus that superpose YAG fundamental and harmonic pulse laser lights with variable pulse widths, where the YAG harmonic pulse laser light peaks before the fundamental, and control the downslope of the fundamental pulse laser light to ensure stable keyhole formation and reduced humping, using optical fibers with varying core diameters to optimize energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If YAG second harmonic Q-switched laser light is applied as intermittently repeated pulse, then optical coupling characteristic with copper and gold is improved, but interaction time with welding materials is too short to achieve deep penetration
Solution Approach 1:
The patent combines YAG fundamental pulse laser light and YAG second harmonic pulse laser light into a single welding process. The fundamental laser provides long pulse width for deep penetration, while the second harmonic laser provides good optical coupling with copper and gold surfaces, achieving synergistic effect that neither laser could accomplish alone
Solution Approach 2:
The YAG second harmonic pulse laser light is applied before the YAG fundamental pulse laser light to preheat and improve optical coupling with the copper or gold surface. This preliminary action prepares the surface to better absorb the subsequent fundamental laser energy, enabling deeper penetration
2Duration of action of moving object
If YAG fundamental pulse laser light with long pulse width is used, then interaction time with welding materials is extended for deep penetration, but optical coupling characteristic with copper and gold remains insufficient
Solution Approach 1:
The patent merges the advantages of both YAG fundamental and second harmonic lasers by superimposing their beams. The fundamental laser provides the necessary long interaction time for deep penetration, while the second harmonic laser component ensures adequate optical coupling with copper and gold surfaces
3Reliability
If conventional laser welding method superposes YAG fundamental and second harmonic lasers, then optical coupling is improved, but keyhole and penetration depth are still insufficient for thick plate welding
Solution Approach 1:
The patent optimizes multiple parameters including pulse width ratios, peak power ratios, and time intervals between the fundamental and second harmonic laser pulses. By carefully adjusting these parameters, the system achieves both good optical coupling and sufficient penetration depth for thick copper plates
Solution Approach 2:
The second harmonic laser pulse is applied beforehand to preheat the surface and improve optical coupling, preparing the material to better absorb the subsequent fundamental laser energy. This sequential approach enables deeper keyhole formation and penetration than simultaneous or reversed sequencing
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 enables deep penetration welding with improved reproducibility and quality by extending interaction time and stabilizing the melted portion around the keyhole, resulting in smooth nugget surfaces and consistent penetration.
Implementation Method 1
laser welding technology that welds metal using lasers
Implementation Method 2
the optical coupling characteristic of the laser light with the welding materials is important
Data Source
AI summary
A YAG pulse laser oscillator 10 oscillates/outputs pulse width-variable YAG fundamental pulse laser light LB, and a YAG pulse laser oscillator 12 oscillates/outputs pulse width-variable YAG second harmonic pulse laser light SHG. An emission unit 20 superposes the pulse laser light LB and the pulse laser light SHG on the same optical axis and focuses, and irradiates a welding point K on welding pieces (W1 and W2) with, the pulse laser light LB and the pulse laser light SHG. A control unit 18 controls the laser oscillation operation of the laser oscillators 10 and 12 so that the point in time when the laser output of the YAG second harmonic pulse laser light SHG reaches its peak is slightly earlier than the point in time when the laser output of the YAG fundamental pulse laser light LB reaches its peak.