Aluminum Brazing Sheet Structure for Fluxless Mg Supply Control
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Solution Overview
Problem
Current methods for brazing aluminum materials in inert gas atmospheres or vacuums without flux face challenges such as limited Mg quantity for oxide film breaking, poor diffusion of Mg, and instability in brazing due to Si diffusion, leading to inadequate brazability and productivity issues.
Innovation Solution
An aluminum alloy brazing sheet with a four-layer or five-layer structure, comprising specific compositions and grain sizes, where the intermediate material provides controlled Mg supply and Si diffusion prevention, ensuring efficient oxide film breaking and stable brazing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Mg is added to the core material and diffused into the brazing material, then oxide film breaking is improved, but the Mg quantity is limited by the solidus temperature requirement, resulting in insufficient Mg for effective oxide film breaking
Solution Approach 1:
The invention divides the Mg supply function into two segments: the core material provides initial Mg content (0.01-2.00 mass%), and an intermediate material layer (5-50 μm thick) with high Mg content (0.10-6.00 mass%) is inserted between the core material and brazing material. This segmentation allows the intermediate layer to serve as a dedicated Mg reservoir that diffuses Mg into the brazing material without being constrained by the core material's solidus temperature limitations.
Solution Approach 2:
The intermediate material layer acts as an intermediary between the core material and brazing material. It has higher Mg affinity than the core material but lower than the brazing material, creating a gradient that facilitates controlled Mg diffusion from the intermediate layer into the brazing material during heating, thereby enabling sufficient Mg supply for oxide film breaking.
2Strength
If the grain size of the core material is small, then material strength is improved, but Si diffusion into the core material causes molten state and loss of shape maintenance capability
Solution Approach 1:
The intermediate material layer serves as a diffusion barrier between the brazing material and core material. It has lower Si affinity than the brazing material, preventing excessive Si diffusion into the core material that would cause molten state. This allows the core material to maintain small grain size for strength while preserving shape maintenance capability during brazing.
Solution Approach 2:
The invention applies different material properties to different layers: the core material has small grain size for strength, the intermediate layer has specific composition and grain size (20-300 μm) for controlled diffusion, and the brazing material has Si for joining. This local differentiation allows each layer to optimize its function without compromising others.
3Quantity of substance
If an intermediate material is provided between brazing material and core material, then Mg supply is improved, but Mg diffusion may be insufficient when brazing material is thick or heating rate is high
Solution Approach 1:
The invention optimizes the intermediate material layer thickness (5-50 μm) and Mg content (0.10-6.00 mass%) to achieve appropriate Mg diffusion speed. The layer is thin enough to allow rapid Mg diffusion during brazing heating, yet thick enough to provide sufficient Mg quantity. This parameter optimization ensures effective oxide film breaking even with high heating rates or thick brazing materials.
4Reliability
If flux is used for brazing aluminum materials, then oxide film breaking is improved, but manufacturing cost increases due to flux application steps
Solution Approach 1:
The intermediate material layer contains Mg that automatically diffuses into the brazing material during heating to break the oxide film. This self-service mechanism eliminates the need for external flux application, reducing manufacturing steps and costs while maintaining reliable oxide film breaking capability.
Solution Approach 2:
The invention extracts the oxide film breaking function from the flux and integrates it into the intermediate material layer. The Mg in the intermediate layer performs the oxide film breaking function internally during heating, removing the need for separate flux application processes and reducing manufacturing complexity.
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 solution achieves excellent brazability by promptly supplying Mg into the brazing material, effectively breaking the oxide film and suppressing Si diffusion, thereby enhancing the brazing process's efficiency and stability.
Implementation Method 1
Mg added to the core material is diffused into the brazing material during brazing heating
Implementation Method 2
bring the molten brazing material into contact with a base material
Implementation Method 3
heating the material in vacuum
Data Source
AI summary
An aluminum alloy brazing sheet is formed of a brazing material, an intermediate material, a core material, and a brazing material. The intermediate material contains Mg of 0.40 to 6.00 mass %, and has total of contents of Mn, Cr, and Zr being 0.10 mass % or more. The core material contains Mg of 0.20 to 2.00 mass % and one or two or more of Mn of 1.80 mass % or less, Si of 1.50 mass % or less, Fe of 1.00 mass % or less, Cu of 1.20 mass % or less, Ti of 0.30 mass % or less, Zr of 0.30 mass % or less, and Cr of 0.30 mass % or less. Each of the core material and the intermediate material has a grain size of 20 to 300 μm, and each of the brazing materials contain Si of 4.00 to 13.00 mass %.