Aluminum Brazing Sheet Corrosion Control via Layered Alloy Composition
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Solution Overview
Problem
The reduction of material thickness in brazing sheets for heat exchangers leads to increased diffusion of Zn and Cu, resulting in decreased pitting potential differences between the inner and outer surfaces, deteriorated corrosion resistance, and early generation of through holes.
Innovation Solution
An aluminum alloy brazing sheet with a core material containing Cu 0.5-1.3%, a sacrificial material with Zn 4.0-7.0%, and a brazing material with Si 6.0-11.0% and Zn 0.1-3.0%, where the pitting potential difference is maintained within specific ranges to control element diffusion and optimize potential balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the material thickness is reduced to improve heat exchanger performance and reduce size, then the weight and size are reduced, but the diffusion of Zn and Cu increases during brazing, causing deterioration of corrosion resistance
Solution Approach 1:
The invention changes the chemical composition parameters of the aluminum alloy, specifically controlling Cu content at 0.5-1.3%, Zn at 4.0-7.0%, and Si at 6.0-11.0%, to optimize the balance between diffusion control and corrosion resistance in thin-walled structures
Solution Approach 2:
The invention uses a composite material structure with multiple layers including aluminum alloy core material, sacrificial material layer, and brazing material layer, where each layer has specific composition to address both weight reduction and corrosion resistance requirements
2Productivity
If the material thickness is reduced, then the productivity and performance are improved, but the pitting potential difference between inner and outer surfaces decreases, leading to early through hole generation
Solution Approach 1:
The invention adjusts compositional parameters including Cu: 0.5-1.3%, Zn: 4.0-7.0%, and Si: 6.0-11.0% to control diffusion rates and maintain adequate pitting potential differences even in thin-walled structures
Solution Approach 2:
The sacrificial material layer is pre-applied to the core material before brazing, creating a protective barrier that prevents direct corrosion attack on the core material during and after the brazing process
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 provides a brazing sheet with improved corrosion resistance and controlled element diffusion, maintaining adequate pitting potential differences, even with reduced thickness, thereby preventing through hole generation and enhancing the material's performance.
Implementation Method 1
a sacrificial material (liner material) made of aluminum alloy with electrochemically lower potential than that of the core material is bonded to the other surface of the core material... the material functions as a sacrificial anode material and corrosion of the core material can be prevented
Implementation Method 2
diffusion of Zn added to the sacrificial material into the interior of the core material and diffusion of Cu added to the core material into the sacrificial material and the brazing material are promoted
Data Source
AI summary
The present invention relates to an aluminum alloy brazing sheet with a thickness of 0.30 nm or less, including: a core material; a sacrificial material cladding one surface of the core material; and a brazing material cladding the other surface of the core material, in which the core material is made of A1—Mn—Si-based aluminum alloy containing by mass %, Cu: 0.5 to 1.3%, the sacrificial material is made of aluminum alloy containing, by mass %, Zn: 4.0 to 7.0%, the brazing material is made of aluminum alloy containing, by mass %, Si: 6.0 to 11.0% and Zn: 0.1 to 3.0%, in a pitting potential after brazing beat treatment, a thickness of a region in which a potential difference from the noblest potential in the core material is 100 mV or more is 10% to 50% of the thickness of the brazing sheet.