Brazing Sheet Composition for Stronger Corrosion-Resistant Heat Exchangers
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Solution Overview
Problem
Existing aluminum alloy brazing sheets for heat exchangers face challenges in achieving high strength while maintaining corrosion resistance, particularly due to the negative effects of magnesium on brazeability and the formation of intermetallic particles that promote galvanic corrosion.
Innovation Solution
The development of a sheet material with an aluminum alloy core containing 0.1 to 1.2 wt % Si, up to 0.6 wt % Fe, 1.0 to 2.6 wt % Cu, 0.5 to 1.8 wt % Mn, up to 0.6 wt % Mg, 0.05 to 1.0 wt % Zn, up to 0.2 wt % Ti, and up to 0.2 wt % Zr, along with a 4XXX aluminum alloy braze liner. The addition of zinc in the core forms second phase particles that alter the corrosion potential difference, reducing the risk of galvanic corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Mg is added to strengthen aluminum alloys, then strength is improved, but brazeability deteriorates
Solution Approach 1:
The patent applies parameter changes by strictly limiting the Mg content to 0.01-0.5 wt% (dramatically reduced from traditional levels) while optimizing other alloying element parameters (Si: 0.1-1.2%, Cu: 1.0-2.6%, Mn: 0.5-1.8%, Zn: 0.05-1.0%) to achieve both high strength and good brazeability. This parameter optimization resolves the contradiction between strength enhancement and brazeability maintenance.
2Strength
If high Cu containing alloys are used to achieve high strength, then strength is improved, but corrosion resistance deteriorates
Solution Approach 1:
The patent optimizes the Cu content parameter to a moderate range (1.0-2.6 wt%) rather than using high Cu concentrations, and balances it with other elements (Si, Mn, Zn) to achieve strength without excessive galvanic corrosion risk. This parameter balancing approach resolves the contradiction between strength and corrosion resistance.
Solution Approach 2:
The patent creates a composite alloy system with multiple elements (Al-Si-Cu-Mn-Mg-Zn) where each element contributes specific properties. The synergistic interaction among these elements achieves high strength while the controlled composition prevents severe galvanic corrosion, resolving the contradiction through material composition design.
3Duration of action of stationary object
If Mg containing alloys are overaged at elevated service temperatures, then durability is improved, but strength deteriorates
Solution Approach 1:
The patent dramatically reduces Mg content to 0.01-0.5 wt%, which prevents the overaging problem altogether. With such low Mg levels, the alloy maintains stable strength properties at elevated temperatures without the precipitate coarsening that occurs in traditional Mg-containing alloys. This parameter change resolves the contradiction between thermal durability and strength retention.
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 solution enhances the corrosion resistance and mechanical strength of heat exchanger components, while also reducing the risk of premature corrosion and maintaining the structural integrity and heat transfer efficiency of the heat exchanger.
Implementation Method 1
the negative effects of magnesium on brazeability and the formation of intermetallic particles that promote galvanic corrosion
Implementation Method 2
The addition of zinc in the core forms second phase particles that alter the corrosion potential difference, reducing the risk of galvanic corrosion
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.