Multilayer Brazing Sheet for Corrosion-Resistant Heat Exchangers
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Solution Overview
Problem
Current aluminum heat exchanger materials face challenges in achieving high strength and corrosion resistance, particularly with high Cu content alloys that are susceptible to corrosion due to the formation of intermetallic particles, leading to galvanic corrosion and premature fin corrosion.
Innovation Solution
Incorporating Zn into the core composition and utilizing a multilayer architecture, including a waterside liner and interliner, to adjust the corrosion potential difference between heat exchanger components, forming Cu5Zn2Al and Cu3ZnAl3 phases that reduce galvanic corrosion, and using a 4XXX aluminum alloy braze liner with specific compositions to enhance corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high Cu content is used to increase strength, then mechanical strength is improved, but corrosion resistance deteriorates due to galvanic corrosion from intermetallic particles
Solution Approach 1:
The patent applies local quality by creating a multilayer structure where the core alloy contains high Cu (1.0-2.6 wt%) for strength, while the braze liner (4XXX series) provides a different composition optimized for corrosion resistance. This spatial differentiation allows each layer to perform its specialized function without compromising the other.
Solution Approach 2:
The patent uses composite materials by combining the high-Cu core alloy with a 4XXX series aluminum alloy braze liner. This composite structure integrates the high strength of Cu-containing alloys with the corrosion resistance of Si-containing braze liners, resolving the contradiction between strength and corrosion resistance.
2Strength
If Mg is added to strengthen aluminum alloys, then mechanical strength is improved, but brazeability deteriorates in controlled atmosphere brazing
Solution Approach 1:
The patent limits Mg content in the core alloy to ≤0.6 wt% to maintain brazeability, while achieving strength through Cu (1.0-2.6 wt%) and Mn (0.5-1.8 wt%). This localized optimization of alloying elements resolves the conflict between strength enhancement and brazing performance.
3Strength
If Mg containing alloys are used for strengthening, then mechanical strength is improved, but service life deteriorates due to overaging at elevated temperatures
Solution Approach 1:
The patent changes the alloying parameters by limiting Mg to ≤0.6 wt% and emphasizing Cu (1.0-2.6 wt%) and Mn (0.5-1.8 wt%) for strengthening. This parameter optimization prevents overaging issues while maintaining strength, thereby extending service life at elevated temperatures.
Solution Approach 2:
The composite structure with Cu and Mn in the core provides age-hardening capability that is more stable at elevated temperatures compared to Mg-based strengthening, thus improving service life under thermal exposure.
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 effectively reduces fin corrosion, maintains mechanical integrity, and enhances the corrosion resistance of heat exchanger components, ensuring prolonged service life and efficient heat transfer.
Implementation Method 1
high Cu content alloys that are susceptible to corrosion due to the formation of intermetallic particles, leading to galvanic corrosion and premature fin corrosion
Implementation Method 2
the Zn of the core forms second phase particles which alter the corrosion potential difference between the matrix of the core and the second phase particles
Implementation Method 3
a braze liner layer of a composite brazing sheet is melted by exposure to high temperatures, e.g., in a furnace, and serves as filler metal to form a braze joint between the heat exchanger components
Data Source
AI summary
An apparatus, material and method for forming a brazing sheet has a high strength core bonded with corrosion protection layer on the coolant side and/or layers on both airside and coolant side. The material enables heat exchanger components, such as tube, header, plate, etc., for applications, such as automotive heat exchangers, that require high fatigue life as well as high service life in a corrosive environment.