Layered Aluminum Brazing Sheet for Recyclable Heat Exchangers
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Solution Overview
Problem
Brazing sheets used in heat exchangers face challenges in recyclability due to high content of alloying elements like manganese, silicon, and zinc, which affect their suitability for recycling into new aluminum alloys, and require balancing chemistry to maintain properties like formability, strength, and corrosion resistance.
Innovation Solution
A brazing sheet composition comprising a core layer of 6XXX series aluminum alloy with a solidus temperature of at least 600°C and a brazing layer of 4XXX series aluminum alloy, with an interliner layer containing no more than 0.5 weight percent manganese, allowing for controlled atmospheric or vacuum brazing while enhancing recyclability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high content of alloying elements (manganese, silicon, zinc) is used in brazing sheets, then corrosion resistance and strength are improved, but recyclability deteriorates
Solution Approach 1:
The brazing sheet is divided into multiple layers with different compositions: a core layer (6XXX series aluminum alloy) providing structural integrity and recyclability, a brazing layer (4XXX series aluminum alloy) enabling joining operations, and an interliner layer protecting the core from contamination. This segmentation allows each layer to be optimized for its specific function while maintaining overall recyclability of the core material.
Solution Approach 2:
Different regions of the brazing sheet have different chemical compositions tailored to local requirements: the core layer has controlled alloying elements for recyclability and strength, the brazing layer has specific composition for brazing performance, and the interliner layer has protective composition. This local quality optimization resolves the contradiction between corrosion resistance and recyclability.
2Strength
If high content of alloying elements is used in brazing sheets, then tensile yield strength is improved, but formability deteriorates
Solution Approach 1:
The core layer uses 6XXX series aluminum alloy with controlled magnesium and silicon content to achieve adequate strength while maintaining good formability. The brazing layer uses 4XXX series aluminum alloy with different composition optimized for brazing performance. This local quality differentiation allows the core to be formed while the brazing layer provides the necessary strength.
Solution Approach 2:
The brazing sheet is a composite structure combining different aluminum alloys in specific layers. The 6XXX series core layer provides formability and structural integrity, while the 4XXX series brazing layer provides strength and brazing capability. This composite approach resolves the contradiction between strength and formability.
3Ease of manufacture
If brazing layer solidus temperature is lower than core layer solidus temperature, then brazing processability is improved, but core layer structural integrity may be compromised
Solution Approach 1:
The core layer is designed with a high solidus temperature (at least 600°C) to maintain structural integrity during brazing, while the brazing layer is designed with a lower solidus temperature to enable brazing at temperatures below the core layer's melting point. This parameter differentiation allows successful brazing without compromising core integrity.
Solution Approach 2:
The multi-layer composite structure allows different thermal properties in different layers. The 4XXX series brazing layer melts at lower temperature than the 6XXX series core layer, enabling selective melting and brazing while the core remains solid and structurally intact. This composite design resolves the contradiction between brazing processability and core integrity.
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 recyclability, formability, corrosion resistance, and tensile yield strength, enabling efficient recycling and maintaining structural integrity and corrosion performance.
Implementation Method 1
brazing the first part to the second part by a process comprising at least one of controlled atmospheric brazing and vacuum brazing
Data Source
AI summary
Brazing sheets, articles formed from or including all or a portion of a brazing sheet, and methods of forming articles of manufacture are provided. A brazing sheet embodiment comprises a core layer, a brazing layer, and an interliner layer intermediate the core layer and the brazing layer. The core layer comprises a 6XXX series aluminum alloy having a core layer solidus temperature of at least 600° C. and comprising at least 0.3 weight percent magnesium based on a total weight of the 6XXX series aluminum alloy. The brazing layer comprises a 4XXX series aluminum alloy having a brazing layer solidus temperature lower than the core layer solidus temperature. The interliner layer comprises a first aluminum alloy comprising no greater than 0.5 weight percent manganese based on a total weight of the first aluminum alloy.