Aluminum Brazing Sheet Composition for Thin Heat Exchanger Strength
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Solution Overview
Problem
Existing aluminum alloy strips or sheets for brazed heat exchangers face challenges in achieving a balance between mechanical strength, corrosion resistance, and brazing ability, particularly in reducing tube thickness without compromising these properties.
Innovation Solution
A specific composition range for the core alloy, including Si: 0.25-0.60%, Fe: ≤0.25%, Cu: 0.60-1.10%, Mn: 1.40-2.00%, Ti: 0.05-0.10%, Mg: ≤0.05%, and controlled impurities, along with optional cover and interlayer alloys, enhances mechanical strength and corrosion resistance without degrading brazing ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of aluminum alloy strips is reduced to decrease weight and improve efficiency, then weight reduction is achieved, but mechanical strength and resistance to fatigue stress deteriorate
Solution Approach 1:
The patent modifies the chemical composition parameters of the aluminum alloy by precisely controlling the content ranges of Si (0.1-0.3%), Cu (0.6-1.1%), Mn (1.2-2.0%), and other elements. This parameter optimization enables the alloy to achieve enhanced mechanical strength and fatigue resistance even at reduced thicknesses, directly resolving the contradiction between weight reduction and strength maintenance
Solution Approach 2:
The patent creates a composite alloy system by combining multiple elements (Al-Si-Cu-Mn-Ti-Mg) in specific proportions. This composite material approach leverages the synergistic effects of different elements to achieve superior mechanical properties at thin gauge, allowing weight reduction without sacrificing strength
2Strength
If alloying elements are added to increase mechanical strength, then mechanical strength improves, but corrosion resistance deteriorates
Solution Approach 1:
The patent optimizes the concentration parameters of alloying elements to achieve a balance between strength and corrosion resistance. Specifically, Si is limited to 0.1-0.3% to prevent excessive intermetallic formation that would harm corrosion resistance, while Cu is optimized at 0.6-1.1% to provide strength without over-alloying. This precise parameter control resolves the contradiction between strength enhancement and corrosion protection
Solution Approach 2:
The patent applies different alloying strategies to different functional requirements: Si and Cu are controlled to provide localized strengthening mechanisms while Mn (1.2-2.0%) is optimized to provide both strength and corrosion resistance. This differentiated approach to element distribution and concentration allows simultaneous achievement of strength and corrosion resistance
3Strength
If alloy composition is modified to improve mechanical properties after brazing, then mechanical strength improves, but brazingability deteriorates
Solution Approach 1:
The patent carefully adjusts the alloy composition parameters to ensure compatibility with brazing processes. The Si content (0.1-0.3%) and Cu content (0.6-1.1%) are optimized to achieve sufficient mechanical strength while maintaining good wetting and bonding characteristics during brazing. The controlled composition prevents excessive intermetallic compound formation that would compromise brazing quality, thus resolving the contradiction between post-brazing strength and brazingability
Solution Approach 2:
The patent ensures homogeneous distribution and compatible interaction of alloying elements (Si, Cu, Mn, Ti, Mg) to create a uniform microstructure that responds consistently to brazing heat treatment. This homogeneity prevents localized variations in brazing behavior and ensures uniform mechanical properties throughout the component after brazing, resolving the contradiction between strength improvement and manufacturing ease
Data Source
Figure 1
AI summary
The invention relates to a strip or sheet intended for manufacturing brazed heat exchangers, having a core layer made of aluminium alloy with the following composition (% by weight): Si: more than 0.25% and less than 0.70%; Fe: less than 0.25% and at least 0.08%; Cu: more than 0.60% and less than 1.10%; Mn: more than 1.40% and less than 2.00%; Ti: less than 0.15% and more than 0.05%; Mg: less than 0.05%; Zr: less than 0.01%; Cr: less than 0.01%; Zn: less than 0.20%; impurities: less than 0.05% each and less than 0.15% in total; remainder aluminium.