Spiral Laser Welding with Dual-Beam Keyhole Stabilization
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Solution Overview
Problem
Laser welding of metal sheets, particularly with challenging material compositions, faces issues such as entrapped gas, cooling rate discrepancies, and material loss due to spatter, which compromise the quality and strength of weld joints, especially when dealing with dissimilar materials or coatings.
Innovation Solution
The use of dual-beam laser radiation with a center beam and an annular beam, where the powers are controlled independently, tracing spiral patterns to maintain a stable keyhole and facilitate gas release, while a controlled laser-power ramp-down minimizes spatter and cracking, enabling strong weld joints even in scenarios with entrapped gas or coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If keyhole welding is used to achieve deep penetration and strong weld joints, then weld strength is improved, but entrapped gas and material loss due to spatter occur
Solution Approach 1:
The laser beam is divided into two separate beams: a center beam and an annular beam. The center beam creates the keyhole for deep penetration and strong weld joints, while the annular beam surrounds and stabilizes the keyhole, reducing spatter and material loss. This segmentation allows each beam to perform its specific function optimally.
Solution Approach 2:
The annular beam acts as an intermediary between the center beam and the surrounding environment. It stabilizes the keyhole formed by the center beam, controlling the melt pool dynamics and reducing violent convection that causes spatter. This intermediary beam prevents material loss while maintaining the deep penetration capability.
2Length of moving object
If keyhole welding is used to achieve deep penetration, then weld depth is improved, but entrapped gas compromises weld quality
Solution Approach 1:
The laser beam is divided into a center beam that creates the deep keyhole and an annular beam that stabilizes it. The annular beam's presence prevents chaotic keyhole oscillations that trap gas, ensuring smoother metal flow and reduced gas entrapment while maintaining deep penetration.
Solution Approach 2:
The annular beam provides continuous stabilization feedback to the keyhole formed by the center beam. By surrounding the keyhole, it monitors and controls the melt pool dynamics, preventing conditions that lead to gas entrapment while maintaining the deep penetration profile.
3Length of moving object
If high laser power density is used to achieve keyhole welding, then penetration depth is improved, but cooling rate discrepancies cause cracking
Solution Approach 1:
The segmented beam structure allows the center beam to provide high power density for deep penetration while the annular beam distributes heat more evenly in the surrounding area. This reduces thermal gradients and cooling rate discrepancies that cause cracking.
Solution Approach 2:
The dual-beam configuration changes the thermal field parameters by creating a more controlled temperature distribution. The annular beam's heat input modifies the cooling rates in the heat-affected zone, reducing thermal stress and preventing cracks while maintaining deep penetration capability.
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 method achieves high-quality, strong weld joints with minimal entrapped gas and cracks, ensuring reliable bonding of dissimilar metals and metals with coatings, regardless of gap size, thereby enhancing the strength and conductivity of the welds.
Implementation Method 1
Absorbed laser power heats the irradiated material, thereby melting material in each part to be joined
Implementation Method 2
laser powers and higher laser power densities that are sufficient to vaporize some of the irradiated material
Implementation Method 3
Pressure of the vaporized material on surrounding melted material opens a channel through the melted material
Data Source
AI summary
Laser welding methods include focusing laser radiation onto a first metal sheet disposed on a metal part, optionally with one or more intervening metal sheets therebetween. The laser radiation is steered to trace at least one spiral path to spot-weld together the metal parts. The laser radiation includes a center beam and an annular beam to maintain a stable keyhole. One method is tailored to weld aluminum parts, e.g., with high gas content and/or dissimilar compositions, and the laser radiation traces first an outward spiral path and then an inward spiral path. The center beam is pulsed during one segment of the inward spiral path. Another method is tailored to weld steel or copper parts having a coating at an interface therebetween, and the laser radiation traces an inward spiral path. The interface may be a zero-gap interface, or a non-zero gap may exist.