Laser Weld Joint Coating for Localized Corrosion Protection
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Solution Overview
Problem
Laser welding of pre-coated sheet metal plates results in weld joints devoid of anti-corrosion protection, leading to corrosion and potential component failure, as existing solutions like paint layers provide inferior protection and can be damaged or improperly applied.
Innovation Solution
A process involving laser welding with two distinct beam spot-sizes, where a larger beam spot-size is used to apply a powdered anti-corrosion material to the weld joint, melting it and forming a localized anti-corrosion layer that adheres to the joint, thereby providing enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser welding is used to join pre-coated sheet metal plates, then welding speed and productivity are improved, but the weld joint loses anti-corrosion protection
Solution Approach 1:
The patent applies preliminary action by depositing the anti-corrosion layer immediately after welding while the weld joint is still hot. The pre-coated sheets are welded first, then the anti-corrosion powder is applied to the hot weld joint, allowing the powder to melt and bond to the substrate. This sequential approach ensures corrosion protection is established before the joint cools down.
Solution Approach 2:
The patent utilizes parameter changes by controlling the temperature of the weld joint and the characteristics of the laser beam. The weld joint is maintained at elevated temperature (above melting point of powder but below melting point of base metal) during powder application. The laser parameters are adjusted to melt the powder and form a protective layer without damaging the underlying weld structure.
2Reliability
If a paint layer is applied to cover the weld joint, then corrosion protection is provided, but the protection is inferior and can be damaged or improperly applied
Solution Approach 1:
The patent replaces the mechanical painting process with a thermal deposition process. Instead of mechanically applying paint that requires drying and curing, the anti-corrosion powder is thermally deposited by melting it with a laser beam. This creates a metallurgically bonded layer that is inherently more durable and resistant to damage than painted coatings.
Solution Approach 2:
The patent exploits phase transitions by melting the anti-corrosion powder and allowing it to solidify on the weld joint. The powder transitions from solid to liquid state under laser heating, then solidifies to form a dense, adherent protective layer. This phase change ensures complete coverage and strong bonding without the defects associated with liquid paint application.
3Strength
If the pre-coat layer is disrupted during welding, then welding integrity is achieved, but scaling occurs during subsequent hot-stamping processing
Solution Approach 1:
The patent applies preliminary anti-action by depositing the anti-corrosion layer on the weld joint before hot-stamping processing. This protective layer is applied in advance to prevent the scaling that would otherwise occur when the disrupted pre-coat is exposed to high temperatures during hot-stamping. The anti-corrosion layer acts as a barrier against oxidative environments.
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
The localized anti-corrosion layer effectively forms a barrier against ambient corrosion, improving the integrity and longevity of the weld joints by providing superior protection compared to traditional paint layers and ensuring consistent coverage even on inward-facing surfaces.
Implementation Method 1
scanning a laser beam having a second beam spot-size along the weld joint, the second beam spot-size larger than the first beam spot-size; and during the scanning, providing a flow of a powdered anti-corrosion surface layer material toward a portion of the weld joint that is being irradiated by the laser beam, wherein the powdered anti-corrosion surface layer material is melted by the laser beam
Implementation Method 2
the powdered anti-corrosion surface layer material is melted by the laser beam and forms a layer adhering to the weld joint
Data Source
AI summary
The present invention relates generally to laser welding in the manufacture of sheet metal components, such as for example automobile components. More particularly, the present invention relates to a process and a system for forming a localized anti-corrosion surface layer along a laser welded joint (weld bead), subsequent to the laser welding together of sheet metal plates having an anti-corrosion surface layer pre-coat.