Multilayer Aluminum Brazing Sheet for Flux-Free Oxide Film Breaking
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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, insufficient diffusion of Mg, and decreased brazability due to Si diffusion and oxide film formation, especially in thick brazing materials or high temperature conditions.
Innovation Solution
An aluminum alloy brazing sheet is developed with a four-layer or five-layer structure, comprising specific compositions and grain sizes for the brazing, intermediate, and core materials, which suppresses Mg diffusion and Si infiltration, ensuring efficient oxide film breaking and improved brazability by controlling the chemical composition and processing of the materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Mg is added to the core material and diffused into the brazing material to break oxide films, then brazability is improved, but the solidus temperature of the core material decreases and Mg quantity is limited
Solution Approach 1:
The patent divides the brazing sheet into multiple functional layers: a core material layer with controlled Mg content (0.03-3 mass%) and an intermediate layer with higher Mg content (0.03-10 mass%). This segmentation allows the core material to maintain its structural integrity and solidus temperature while the intermediate layer provides sufficient Mg for oxide film breaking during brazing, thus resolving the contradiction between brazability and solidus temperature.
2Reliability
If Mg is added to the brazing material to break oxide films, then brazability is improved, but Si diffusion increases and brazability decreases
Solution Approach 1:
The patent introduces an intermediate layer positioned between the core material and the brazing material. This intermediate layer acts as a mediator that controls the interaction between Mg and Si during brazing. The intermediate layer with specific Mg content (0.03-10 mass%) and composition prevents excessive Si diffusion into the core material while still providing adequate Mg for oxide film breaking, thus resolving the contradiction between brazability improvement and composition stability.
3Reliability
If flux is used for brazing aluminum materials, then oxide film breaking is effective, but manufacturing cost increases
Solution Approach 1:
The patent enables the brazing sheet to break oxide films autonomously through controlled Mg diffusion during the brazing process itself, without requiring external flux materials. The Mg in the intermediate layer (0.03-10 mass%) and core material (0.03-3 mass%) reacts with oxide films at brazing temperature, providing self-service oxide film breaking functionality. This eliminates the need for separate flux application steps and reduces manufacturing costs while maintaining effective oxide film removal.
4Reliability
If vacuum brazing is used, then oxide film breaking is effective, but equipment cost and maintenance cost increase
Solution Approach 1:
The patent enables oxide film breaking to occur through the inherent Mg content in the brazing sheet structure (intermediate layer with 0.03-10 mass% Mg and core material with 0.03-3 mass% Mg), allowing the material to serve its own oxide removal function. This self-service mechanism works effectively in inert gas atmospheres without requiring vacuum equipment, thereby eliminating the need for expensive vacuum brazing equipment and its associated maintenance costs while still achieving reliable oxide film breaking.
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 effectively breaking the oxide film and preventing Si diffusion, maintaining the shape of heat exchangers, and reducing the need for flux, thus lowering manufacturing costs and improving productivity.
Implementation Method 1
diffusing Mg added to the core material into the brazing material
Implementation Method 2
Mg effectively acts on breakage of an oxide film on the surface of the brazing material
Data Source
AI summary
An aluminum alloy brazing sheet is formed of a four-layer material formed of a brazing material, an intermediate material, a core material, and a brazing material. The intermediate material comprises Mg of 0.40 to 6.00 mass %, and has a total of contents of Mn, Cr, and Zr being 0.10 mass % or more. The core material comprises Mg of 0.20 to 2.00 mass % and comprises one or two or more of Mn of 1.80 mass % or less, Si of 1.05 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.