Three-Layer Aluminum Cladding for Brazable Corrosion-Resistant Heat Exchangers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aluminum alloy heat exchangers face challenges in achieving both excellent brazability and external surface corrosion resistance, particularly due to issues with the distribution and concentration of Zn during brazing, which affects the sacrificial anode effect and leads to insufficient corrosion resistance and increased production costs.
Innovation Solution
A three-layer clad material composition is used, where one side of the core material is clad with an aluminum alloy containing 3 to 10% Si and 1 to 10% Zn, and the other side with an aluminum alloy containing 3 to 13% Si and 0.05% Cu, with specific Si content differences between the cladding materials to optimize Zn distribution and corrosion resistance, ensuring the cladding material 1 is on the air side and cladding material 2 is in contact with the refrigerant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sheet material clad with Al-Zn-based alloy is used to form refrigerant tube, then external surface corrosion resistance is improved, but brazability deteriorates due to Zn flowing during brazing
Solution Approach 1:
The patent applies local quality by creating a three-layer clad structure where each layer has different composition and function: the outer layer (cladding material 1) contains Zn for corrosion protection, the intermediate layer (cladding material 2) has optimized Si content for brazability, and the core material provides structural strength. This localized differentiation of properties resolves the contradiction between corrosion resistance and brazability.
Solution Approach 2:
The patent uses composite materials by combining three different aluminum alloy compositions in a layered clad structure. The outer cladding layer contains Al-Zn-Si alloy for corrosion resistance, the intermediate layer contains Al-Si alloy for brazability, and the core is Al-Mn-Cu-Ti alloy for strength. This composite approach allows each layer to perform its specific function optimally.
2Ease of manufacture
If filler metal powder is applied to the surface of Al-Zn-based alloy, then brazability is improved, but production cost increases due to expensive filler metal powder
Solution Approach 1:
The patent extracts the brazability function from a separate filler metal powder application process and integrates it into the cladding structure itself. The intermediate cladding layer (cladding material 2) with 3-13% Si content serves as the brazable surface, eliminating the need for additional expensive filler metal powder while maintaining good brazability.
Solution Approach 2:
The cladding structure is designed to be self-sufficient for brazing operations. The intermediate cladding layer with appropriate Si content provides inherent brazability, allowing the material to serve its own brazing needs without requiring external filler metal additions, thereby reducing production costs.
3Ease of manufacture
If sheet material clad with Al-Si-based alloy filler metal is used, then brazability is improved, but corrosion resistance deteriorates due to insufficient Zn remaining on external surface
Solution Approach 1:
The patent segments the brazable surface and corrosion-resistant surface into separate layers. The intermediate cladding layer (cladding material 2) with high Si content provides brazability, while the outer cladding layer (cladding material 1) with Zn maintains corrosion resistance. This segmentation allows both functions to coexist without interference.
Solution Approach 2:
Different regions of the clad material are assigned different qualities: the intermediate layer has high Si content for brazability, while the outer layer has Zn for corrosion resistance. This local differentiation ensures that brazing operations can be performed effectively while the external surface maintains its sacrificial anode protection.
4Reliability
If Si concentration in cladding material is increased to suppress Zn flowing during brazing, then corrosion resistance is maintained, but brazability deteriorates due to insufficient liquid filler
Solution Approach 1:
The patent transitions from a single-layer to a three-layer clad structure, adding dimensional complexity to resolve the contradiction. By distributing Si content across different layers (lower in outer layer, higher in intermediate layer), the system achieves both corrosion resistance and brazability that cannot be obtained in a single layer.
Solution Approach 2:
The patent changes the Si concentration parameter across different layers: the outer cladding layer has 3-10% Si to maintain corrosion resistance, while the intermediate cladding layer has 3-13% Si to provide adequate liquid filler for brazability. This parameter differentiation resolves the contradiction between maintaining Zn distribution and ensuring sufficient liquid filler.
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
This configuration enhances brazability and provides excellent external surface corrosion resistance, preventing perforation corrosion and maintaining the sacrificial anode effect while reducing production costs by optimizing the distribution and concentration of Zn during brazing.
Implementation Method 1
a phenomenon in which Zn included in the sacrificial anode material flows during brazing is suppressed by reducing the amount of liquid filler as compared with a known Al—Si-based alloy filler metal so that a sufficient amount of Zn remains on the external surface of the refrigerant tube after brazing to provide a sacrificial anode effect
Implementation Method 2
assembling a member such as a fin material with the refrigerant tube to form a specific structure, and effecting brazing using a fluoride flux in an inert gas atmosphere
Data Source
AI summary
A three-layer clad material includes a core material, a cladding material 1, and a cladding material 2, the core material including an aluminum alloy that includes 0.5 to 1.8% of Mn, and either or both of more than 0.05% and less than 0.2% of Cu, and 0.05 to 0.30% of Ti, with the balance being Al and unavoidable impurities, the cladding material 1 including an aluminum alloy that includes 3 to 10% of Si, and 1 to 10% of Zn, with the balance being Al and unavoidable impurities, and the cladding material 2 including an aluminum alloy that includes 3 to 13% of Si, and 0.05% or less of Cu, with the balance being Al and unavoidable impurities, wherein the Si content X (%) in the cladding material 1 and the Si content Y (%) in the cladding material 2 satisfy the value (Y−X) is −1.5 to 9%.