Four-Layer Aluminum Brazing Sheet With Sacrificial Corrosion Layer
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Solution Overview
Problem
Existing aluminum alloy brazing sheets for heat exchangers lack sufficient corrosion resistance in harsh environments, particularly on the external surfaces of tube members, leading to coolant leakage and functional failure due to corrosion.
Innovation Solution
A four-layer aluminum alloy brazing sheet is developed, featuring a core material with specific compositions of Si, Fe, Cu, and Mn, and intermediate and brazing layers with controlled Si, Fe, Cu, Ti, Zr, and Cr content, along with optimized clad ratios and annealing processes to enhance corrosion resistance and manufacturing feasibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the tube member thickness is reduced to achieve weight reduction, then the fuel consumption is improved, but the corrosion resistance is deteriorated
Solution Approach 1:
The tube member is segmented into multiple functional layers: core material (Al-Mn-Si alloy for strength), intermediate layer (Al-Mn alloy for sacrificial corrosion protection), and brazing material layers (Al-Si alloy for joint formation). This segmentation allows each layer to perform its specific function, enabling thin-walled construction without sacrificing corrosion resistance.
Solution Approach 2:
The intermediate layer acts as a sacrificial anode intermediary between the core material and the corrosive environment. It preferentially corrodes to protect the core material, extending the service life of the thin-walled tube member while maintaining structural integrity.
2Reliability
If a sacrificial anode fin is attached to prevent corrosion, then the corrosion resistance is improved, but the protection is insufficient when the fin corrodes or detaches
Solution Approach 1:
The sacrificial protection function is merged directly into the tube member structure through the intermediate layer, eliminating the need for separate sacrificial anode fins. This integrated approach ensures continuous protection as long as the tube member exists, without dependence on detachable components.
Solution Approach 2:
The intermediate layer provides self-service corrosion protection by automatically acting as a sacrificial anode. It continuously protects the core material through galvanic corrosion mechanisms without requiring external maintenance or replacement, ensuring long-term durability.
3Reliability
If the Mn content in the intermediate layer is increased to improve corrosion resistance, then the corrosion protection is enhanced, but the clad rolling property deteriorates
Solution Approach 1:
The Mn content parameter in the intermediate layer is precisely controlled within the range of 0.35-1.8 mass% to achieve optimal balance. This parameter optimization ensures sufficient corrosion resistance while maintaining adequate clad rolling properties for manufacturing. The Si content is also controlled at 0.3-1.0 mass% to support this balance.
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 provides excellent corrosion resistance, even in harsh environments, by creating a sacrificial anode effect and improving the strength and pitting resistance of the heat exchanger components, thereby preventing coolant leakage and ensuring the longevity of the heat exchanger's functionality.
Implementation Method 1
attach a fin with a lower potential to an external surface of a coolant tube formed of a tube member including no sacrificial layer, to use the fin as a sacrificial anode to prevent corrosion of the tube
Implementation Method 2
performing brazing joint in a heating furnace of an inert gas atmosphere
Implementation Method 3
subjected to no annealing during the cold rolling, and subjected to recrystallization annealing only at a final thickness
Data Source
AI summary
An aluminum alloy brazing sheet includes a four-layer material containing an intermediate layer formed of an aluminum alloy including Mn of from 0.2 to less than 0.35 mass %, Si of 0.6 mass % or less, Fe of 0.7 mass % or less, and Cu of 0.1 mass % or less, with the balance being Al and inevitable impurities, a core material formed of an aluminum alloy including Si of 1.2 mass % or less, Fe of 1.0 mass % or less, Cu of from 0.3 to 1.0 mass %, and Mn of from 0.5 to 2.0 mass %, with the balance being Al and inevitable impurities, and each of an air-side brazing material layer and an internal brazing material layer is formed of an aluminum alloy including Si of from 4 to 13 mass %, with the balance being Al and inevitable impurities.