Brazed Heat Exchanger Baseplate Alloy for Stronger Joints
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Solution Overview
Problem
Existing aluminium alloys used for brazed heat exchanger assemblies suffer from metallographic braze-related defects such as excessive Si diffusion and braze voids, leading to joint quality issues and sensitivity to Liquid Film Migration (LFM), which undermines structural integrity and joint strength.
Innovation Solution
A brazed heat exchanger assembly using an age-hardenable 3XXX-series aluminium alloy with specific compositions (Mn 0.8%-1.8%, Cu 0.15%-1.20%, Si 0.25%-1.30%, Mg 0.10%-0.60%, Fe up to 0.8%, Zn up to 0.3%, Ti up to 0.20%, Cr up to 0.25%, Zr up to 0.25%, balance aluminium and impurities up to 0.05%, total up to 0.20%) that provides increased post-braze strength and improved brazability, reducing Si diffusion and enhancing joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional aluminium alloys (5XXX, 6XXX, or 7XXX-series) are used for baseplates in brazed heat exchanger assemblies, then good formability and brazability are achieved, but post-braze strength is insufficient and excessive Si diffusion occurs during brazing
Solution Approach 1:
The patent changes the chemical composition parameters of the aluminium alloy baseplate by specifying precise ranges for Mn (0.8-1.8%), Cu (0.15-1.20%), Si (0.25-1.30%), and other elements. This parameter optimization resolves the contradiction by achieving both good brazability (through controlled Si content) and high post-braze strength (through age-hardenable Mn and Cu content) without excessive Si diffusion during brazing.
2Weight of moving object
If the baseplate thickness is reduced to meet weight targets, then weight is decreased, but structural integrity and strength may be compromised
Solution Approach 1:
The patent enables thinning of the baseplate by fundamentally changing the material properties through optimized alloy composition. The age-hardenable 3XXX-series aluminium alloy with specific Mn (0.8-1.8%) and Cu (0.15-1.20%) content provides high strength-to-weight ratio, allowing reduced thickness while maintaining structural integrity. This resolves the contradiction between weight reduction and strength preservation.
3Reliability
If brazing temperature is increased to ensure proper brazing, then brazing reliability is improved, but Si diffusion into the baseplate increases causing metallographic defects
Solution Approach 1:
The patent resolves this contradiction by changing the baseplate material composition parameters - specifically controlling Si content (0.25-1.30%) and adding Mn (0.8-1.8%) and Cu (0.15-1.20%). This optimized composition allows brazing at standard temperatures without excessive Si diffusion, while the age-hardenable elements ensure proper joint strength develops after brazing.
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 achieves enhanced post-braze strength, improved joint integrity, and resistance to LFM, allowing for thinner gauge baseplates and increased structural integrity, while maintaining good brazability, thus meeting modern automotive weight and emission targets.
Implementation Method 1
an age-hardenable 3XXX-series aluminium alloy
Implementation Method 2
The various components are commonly joined to each other by brazing. In a brazing process, a brazing filler metal or brazing alloy
Implementation Method 3
excessive Si diffusion
Data Source
AI summary
The invention relates to a brazed heat exchanger incorporating an aluminium alloy baseplate and wherein the baseplate is made from an aluminium alloy having a composition, in wt. %, of: Mn 0.8-1.8, Cu 0.15-1.20, Si 0.25-1.30, Mg 0.10-0.60, Fe ≤0.8, Zn ≤0.3, Ti ≤0.20, Cr ≤0.25, Zr ≤0.25, balance aluminium and impurities.