Aluminum Alloy Brazing Sheet for Heat Exchanger Welding
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Solution Overview
Problem
Existing aluminum alloy brazing sheets for heat exchangers face challenges in maintaining strength and corrosion resistance while being thinned, leading to increased weld defects and cracking during electric resistance welding.
Innovation Solution
An aluminum alloy brazing sheet with a core containing Si, Cu, and Mn, and a sacrificial material with Si, Zn, and Mg, optimized to improve strength and corrosion resistance, and featuring a work hardening exponent of not less than 0.05 and average crystal grain size of not more than 10 μm to enhance weldability and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the tube material is thinned to reduce heat exchanger mass, then weight reduction is achieved, but weld defects and weld cracking increase during electric resistance welding
Solution Approach 1:
The invention changes the chemical composition parameters of the aluminum alloy by precisely controlling the content ranges of Si (0.1-1.0%), Cu (0.5-1.2%), and Mn (0.5-2.0%). This parameter optimization improves the material's inherent weldability and cracking resistance, allowing thin-walled tubes to be welded without the defects that normally occur when simply thinning conventional alloys.
Solution Approach 2:
The invention uses a composite clad structure with a core aluminum alloy and an Al-Zn-Mg sacrificial material layer. This composite structure provides both the strength needed for thin-walled construction and the corrosion resistance required for reliable welding performance, resolving the contradiction between weight reduction and weld quality.
2Weight of moving object
If the tube material is thinned and strengthened to reduce heat exchanger mass, then weight reduction is achieved, but weld cracking occurs during electric resistance welding
Solution Approach 1:
The invention optimizes the alloy composition parameters, specifically controlling Si at 0.1-1.0%, Cu at 0.5-1.2%, and Mn at 0.5-2.0%, to achieve the right balance between strength and ductility. This prevents weld cracking while maintaining thin wall thickness for weight reduction.
Solution Approach 2:
The invention applies a sacrificial material layer with specific Al-Zn-Mg composition on the inner surface of the tube. This local modification provides enhanced corrosion resistance and weldability at the critical welding zone without compromising the overall thin-walled structure's weight advantage.
3Strength
If the core alloy composition is optimized for strength, then strength after brazing is improved, but high frequency weldability deteriorates
Solution Approach 1:
The invention carefully balances the composition parameters: Si (0.1-1.0%) for strength, Cu (0.5-1.2%) for brazing strength, and Mn (0.5-2.0%) for overall performance. This optimized parameter set achieves both high strength after brazing and good high frequency weldability, resolving the contradiction between these two manufacturing requirements.
Solution Approach 2:
The invention uses a composite structure where the core aluminum alloy provides strength after brazing, while the Al-Zn-Mg sacrificial material layer on the inner surface provides the necessary weldability for high frequency welding. This division of functions resolves the contradiction between strength and ease of manufacture.
Data Source
AI summary
An aluminum alloy brazing sheet for heat exchangers has a core, a sacrificial material formed on one side of the core, and a brazing filler metal formed on the other side of the core. The core is made of an aluminum alloy containing Si, Cu, Mn, and Al. The sacrificial material is made of an aluminum alloy containing Si, Zn, Mg, and Al. The brazing filler metal is made of an aluminum alloy. The aluminum alloy brazing sheet for heat exchangers has a work hardening exponent n of not less than 0.05. The core has an average crystal grain size of not more than 10 μm in a cross-section. The aluminum alloy brazing sheet for heat exchangers has excellent strength and corrosion resistance even when it is formed into a thin material and also has excellent high frequency weldability and weld cracking resistance during electric resistance welding.