Brazing-Sheet Aluminium Alloy for Post-Braze Strength Retention
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Solution Overview
Problem
There is a need for an aluminium alloy with high strength at elevated temperatures, specifically maintaining post-braze strength for extended periods at 260°C and 300°C, while also providing corrosion resistance and being suitable for various brazing methods to meet the demands of high-performance diesel engine turbochargers and heat exchangers.
Innovation Solution
A wrought aluminium alloy with a composition of Mn 0.5% to 1.8%, Cu 0.4% to 2.2%, Sc 0.01% to 0.6%, Zr 0.01% to 0.4%, and optional Cr and Ti, combined with a minimum Sc and Zr addition of 0.22%, which enhances post-braze strength and corrosion resistance, and can be used in brazing sheets and extruded products for heat exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional aluminium alloys are used in heat exchangers for diesel engine turbochargers, then the heat exchanger can operate at elevated temperatures, but the post-braze strength decreases significantly after prolonged exposure to temperatures above 260°C
Solution Approach 1:
The patent modifies the chemical composition parameters of the aluminium alloy by adding specific amounts of Sc (0.01-0.6%), Zr (0.01-0.4%), and Ag (up to 0.6%), while controlling Mn (0.5-1.8%) and Cu (0.4-2.2%). These compositional changes enable the alloy to maintain post-braze strength of 40 MPa or more after 1000-2000 hours at 260-300°C, resolving the strength degradation issue
Solution Approach 2:
The invention creates a multi-element composite aluminium alloy system combining Sc, Zr, Ag, Mn, and Cu with aluminium base. This composite material structure provides synergistic effects where Sc and Zr form strengthening precipitates, Ag enhances high-temperature strength, and Mn-Cu provide solid solution strengthening, collectively maintaining strength at elevated temperatures
2Strength
If the aluminium alloy composition is modified to increase post-braze strength at elevated temperature, then strength is improved, but corrosion resistance may be compromised
Solution Approach 1:
The patent carefully controls the concentration parameters of alloying elements to achieve optimal balance. Sc (0.01-0.6%) and Zr (0.01-0.4%) are added in small amounts for strengthening without excessive corrosion susceptibility, while Ag (up to 0.6%) enhances high-temperature strength. The controlled composition maintains both strength and corrosion resistance
3Reliability
If the aluminium alloy is designed for high strength at elevated temperature, then it becomes suitable for charge air coolers, but the alloying complexity and manufacturing difficulty increase
Solution Approach 1:
The patent defines specific compositional ranges for alloying elements that balance performance and manufacturability. The ranges Sc (0.01-0.6%), Zr (0.01-0.4%), Ag (up to 0.6%), Mn (0.5-1.8%), and Cu (0.4-2.2%) provide sufficient high-temperature strength while remaining practical for industrial alloy production and brazing processes
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 alloy achieves a post-braze yield strength of 40 MPa or more after 1,000 to 2,000 hours at elevated temperatures, maintaining high corrosion resistance and compatibility with multiple brazing processes, making it suitable for heat exchanger applications.
Implementation Method 1
A wrought aluminium alloy with a composition of Mn 0.5% to 1.8%, Cu 0.4% to 2.2%, Sc 0.01% to 0.6%, Zr 0.01% to 0.4%, and optional Cr and Ti
Implementation Method 2
The alloy achieves a post-braze yield strength of 40 MPa or more after 1,000 to 2,000 hours at elevated temperatures
Implementation Method 3
Sc 0.01% to 0.6%, Zr 0.01% to 0.4%
Data Source
Figure 1
AI summary
The invention relates to a wrought aluminium alloy, ideally for use as core alloy in a brazing sheet product, and having increased post-braze strength at elevated temperatures and which aluminium alloy can be used for use in heat exchangers. The wrought aluminium alloy comprising (in wt.%): Mn 0.5% to 1.8%, Cu 0.4% to 2.2%, Sc 0.01 % to 0.6%, Zr 0.01 % to 0.4%, Ag up to 0.6%, optional one or both of 0.03% to 0.5% Cr and 0.01 % to 0.6% Ti, Mg up to 0.6%, Fe up to 0.7%, Si up to 0.8%, Zn up to 0.5%, balance aluminium and impurities.