Single-Layer Aluminum Alloy Sheet for Brazing Strength and Corrosion
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Solution Overview
Problem
Aluminum alloy materials with single-layer heat joining capability face challenges in maintaining sufficient brazeability, material strength, and corrosion resistance due to issues with liquid phase distribution and grain boundary formation during brazing, leading to reduced joining performance and premature fin peeling.
Innovation Solution
An aluminum alloy sheet composition comprising Si 2.00 to 3.00%, Fe 0.05 to 0.40%, Mn 0.80 to 1.80%, with optional additives, and controlled grain boundary distribution and grain size after heating, ensuring 25% to 90% grain boundaries in the sheet thickness direction and an average grain size of 950 µm or less, enhances brazeability and material strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Si content is increased to increase the liquid phase amount, then the brazeability is improved, but the material strength decreases excessively
Solution Approach 1:
The invention optimizes the Si content parameter within a specific range (2.00-3.00 mass%) rather than increasing it without limit. This parameter optimization ensures sufficient liquid phase formation for good brazeability while preventing excessive Si from causing severe material strength degradation. The controlled parameter range resolves the contradiction between improving brazeability and maintaining strength.
2Reliability
If the Cu content is increased to increase the liquid phase ratio, then the brazeability is improved, but the corrosion resistance deteriorates and material strength increases reducing formability
Solution Approach 1:
The invention strictly controls the Cu content parameter to 0.20 mass% or less to prevent Cu-rich precipitates that would deteriorate corrosion resistance. By optimizing this parameter within a limited range, the invention achieves adequate liquid phase formation for brazeability while maintaining corrosion resistance and formability, thus resolving the contradiction between improving brazeability and preventing corrosion resistance deterioration.
3Strength
If the grain size is reduced to improve material strength, then the strength increases, but the deformation resistance at brazing temperature decreases
Solution Approach 1:
The invention creates local quality differentiation in the grain structure by controlling grain boundaries to be distributed at specific proportions (25% to 90% in width direction) within the sheet thickness. This local grain boundary distribution provides deformation resistance at brazing temperature through grain boundary strengthening while maintaining overall material strength, resolving the contradiction between strength and high-temperature deformation resistance.
4Ease of manufacture
If the fillet area is reduced due to single-layer heat joining, then the manufacturing cost decreases, but the corrosion protection life is shortened causing premature fin peeling
Solution Approach 1:
The invention optimizes multiple parameters simultaneously including Si content (2.00-3.00 mass%), Fe content (0.05-0.40 mass%), Mn content (0.80-1.80 mass%), grain boundary proportion (25%-90%), and grain size (950 µm or less). This multi-parameter optimization achieves adequate fillet formation for sufficient corrosion protection life while maintaining the cost advantages of single-layer heat joining without requiring additional joining materials, thus resolving the contradiction between manufacturing cost and corrosion protection life.
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 sheet achieves improved brazeability and material strength, preventing premature fin peeling and maintaining structural integrity in corrosive environments by optimizing grain boundaries and grain size distribution.
Implementation Method 1
the liquid phase generated inside the alloy material by heating is used for joining
Implementation Method 2
the material changes into a semi-molten state during the heat joining
Data Source
Figure 1
Figure 2(a)~2(d)
Figure 3(a)~3(d)
AI summary
An aluminum alloy sheet having single-layer heat joining capability, the aluminum alloy sheet being formed of an aluminum alloy is provided. The aluminum alloy sheet comprises: Si of 2.00 to 3.00 mass %; Fe of 0.05 to 0.40 mass %; and Mn of 0.80 to 1.80 mass %, with a Cu content of 0.20 mass % or less (including 0.00 mass %) and a Zn content of 6.00 mass % or less (including 0.00 mass %), and optionally comprising any one or two or more among Mg of 0.08 mass % or less, Ti of 0.30 mass % or less, Zr of 0.30 mass % or less, Cr of 0.30 mass % or less, V of 0.30 mass % or less, Be of 0.10 mass % or less, Sr of 0.10 mass % or less, Bi of 0.30 mass % or less, Na of 0.10 mass % or less, and Ca of 0.05 mass % or less, with the balance being Al and inevitable impurities. After a heating test in which a temperature is raised from 300°C to 400°C at an average temperature rising rate of 60°C/min or less and then held at 600±3°C for 5±3 minutes, in a cross section perpendicular to a rolled surface and perpendicular to a rolling direction, a proportion of regions each having one or more grain boundaries in a sheet thickness direction is 25% or more and less than 90% in a width direction, and average grain size on a sheet surface in a direction perpendicular to the rolling direction is 950 µm or less.