Aluminum Brazing Sheet With Mg Gradient for Flux-Free Nitrogen Brazing
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Solution Overview
Problem
Existing aluminum alloy brazing sheets face challenges in achieving excellent brazability without using flux in an inert gas atmosphere, as they often fail to break the oxide film effectively, leading to poor surface quality and brazing failures due to the formation of thick MgO films.
Innovation Solution
An aluminum alloy brazing sheet comprising a core material with 0.10 to 0.50% Mg and a brazing material with Si 6.00 to 13.00% and limited Mg content, where the Mg integration value from the surface to a depth of 30 nm is 150 atm %×nm or less, along with optional additions of Bi, Fe, Si, Mn, Cu, Zn, and acid etching to control oxide film thickness and enhance brazability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Mg is added to the brazing material to weaken oxide film, then oxide film breaking ability is improved, but MgO film forms on the surface which prevents good brazability
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of Mg element within the brazing material. The Mg content is controlled to be 0.01-0.05 mass% in the brazing material surface layer (0-10 μm from surface) and 0.1-0.5 mass% in the core material. This localized distribution allows the Mg to effectively weaken the oxide film during brazing while limiting the total Mg available to form harmful MgO films on the surface.
Solution Approach 2:
The patent changes the parameter of Mg concentration distribution within the brazing material. Instead of uniform Mg distribution, it establishes a specific gradient where Mg concentration is lower at the surface (0.01-0.05 mass%) and higher in the core (0.1-0.5 mass%). This parameter change optimizes the balance between oxide film weakening capability and MgO film suppression.
2Ease of manufacture
If flux is applied to the surface before brazing, then brazing process is simplified, but additional operations and cost increase are required
Solution Approach 1:
The patent implements self-service by incorporating Mg element directly into the brazing material structure. The Mg in the brazing material surface layer (0.01-0.05 mass%) automatically weakens the oxide film during the brazing heating process itself, eliminating the need for separate flux application and removal operations. The brazing material serves its own oxide film breaking function through its compositional design.
3Reliability
If Mg content in brazing material is increased to break oxide film, then oxide film weakening is improved, but brazing quality deteriorates due to thick MgO film
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of Mg element within the brazing material. The Mg content is controlled to be 0.01-0.05 mass% in the brazing material surface layer (0-10 μm from surface) and 0.1-0.5 mass% in the core material. This localized distribution allows the Mg to effectively weaken the oxide film during brazing while limiting the total Mg available to form harmful MgO films on the surface.
Solution Approach 2:
The patent changes the parameter of Mg concentration distribution within the brazing material. Instead of uniform Mg distribution, it establishes a specific gradient where Mg concentration is lower at the surface (0.01-0.05 mass%) and higher in the core (0.1-0.5 mass%). This parameter change optimizes the balance between oxide film weakening capability and MgO film suppression.
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 enables excellent brazability by effectively weakening the oxide film, preventing MgO film formation, and ensuring the molten brazing material spreads uniformly, resulting in improved surface quality and reduced brazing failures.
Implementation Method 1
Mg in a brazing material surface layer reacts with oxygen that enters from the outside, thereby easily forming a MgO film
Implementation Method 2
Mg is relatively easily oxidized, and the Mg in a brazing material surface layer reacts with oxygen that enters from the outside, thereby easily forming a MgO film
Implementation Method 3
the molten brazing material is less likely to get wet and spread over the surface
Data Source
AI summary
Provided is a brazing sheet that can exhibit excellent brazability in brazing an aluminum material without using flux in an inert gas atmosphere such as nitrogen gas atmosphere. An aluminum alloy brazing sheet to be used for brazing in an inert gas atmosphere is an aluminum alloy brazing sheet comprising: a core material; and a brazing material clad on one side or both sides of the core material, wherein the core material is made of an aluminum alloy comprising Mg at 0.10 to 0.50 mass % with the balance being aluminum and inevitable impurities, the brazing material is made of an aluminum alloy comprising Si at 6.00 to 13.00 mass % and Mg at a content limited to less than 0.05 mass % with the balance being aluminum and inevitable impurities, and a Mg integration value from a surface of the brazing material to a depth of 30 nm is 150 atm %×nm or less.