Aluminum Alloy Brazing Sheet Composition for Oxide Film Breakup
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Solution Overview
Problem
Current methods for brazing aluminum alloys without flux in a nitrogen gas furnace face challenges such as high costs, uneven flux application, and maintenance issues due to vaporized Mg, leading to inferior brazing results and distorted fillets in practical joints.
Innovation Solution
An aluminum alloy brazing sheet with a core material and a brazing material containing Si and specific X atoms (Mg, Li, Be, Ca, Ce, La, Y, Zr) is used, where the X atoms break the oxide film during brazing, forming particulate oxides with a volume change ratio of 0.99 or lower, enabling effective exposure of the molten brazing material's surface in an inert gas atmosphere without flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flux is used in a nitrogen gas furnace to break the oxide film, then the oxide film can be effectively broken, but the cost increases and there is risk of inferior brazing when flux is unevenly applied
Solution Approach 1:
The invention extracts and eliminates the flux from the brazing process by using a vacuum heating furnace instead. The vacuum environment naturally breaks the oxide film through magnesium vaporization without requiring any flux material, thereby removing the source of manufacturing cost increase and application uniformity problems while maintaining reliable brazing quality
Solution Approach 2:
The invention uses a vacuum environment (inert atmosphere) to replace the nitrogen gas furnace with flux. The vacuum condition prevents oxide formation and allows magnesium to vaporize and break existing oxide films effectively, achieving reliable brazing without the costs and risks associated with flux application in nitrogen atmosphere
2Reliability
If a vacuum heating furnace is used to vaporize Mg and break the oxide film, then the oxide film can be broken without flux, but expensive vacuum equipment is required and high maintenance cost is needed to remove Mg adhering to the furnace
Solution Approach 1:
The invention changes the atmospheric parameters from vacuum to controlled nitrogen atmosphere with specific oxygen concentration (1-100 ppm). This parameter change allows the use of magnesium-containing brazing material to break oxide films through controlled chemical reaction rather than vaporization, eliminating the need for expensive vacuum equipment while maintaining reliable brazing quality
Solution Approach 2:
The invention uses a simple nitrogen gas furnace (much cheaper than vacuum equipment) with controlled oxygen concentration. The brazing material contains magnesium that reacts with trace oxygen to break oxide films, providing an inexpensive alternative to expensive vacuum equipment while achieving the same oxide film breaking effect
3Reliability
If Mg is included in the brazing material to break the oxide film, then surface joining can be enabled, but an MgO-based film is formed during brazing heating that obstructs fillet formation and causes break of the fillet
Solution Approach 1:
The invention changes the oxygen concentration parameter in the atmosphere from high levels to a controlled range of 1-100 ppm. This parameter change allows magnesium to react with trace oxygen to break oxide films without forming excessive MgO that would obstruct fillet formation, thereby maintaining both brazing capability and fillet uniformity
Solution Approach 2:
The invention uses controlled oxygen concentration (1-100 ppm) as a feedback mechanism to regulate the magnesium oxidation process. By precisely controlling the oxygen level, the system ensures that enough MgO is formed to break the oxide film but not so much that it obstructs fillet formation, achieving both reliable brazing and uniform fillets
4Ease of manufacture
If pickling is performed on the brazing material before brazing heating to remove MgO-based film, then brazing without flux can be enabled, but the method is not capable of sufficiently suppressing formation of MgO-based film during brazing heating
Solution Approach 1:
The invention performs preliminary action by controlling the oxygen concentration in the brazing atmosphere to 1-100 ppm before and during the brazing process. This preliminary control prevents excessive oxide film formation from the start, eliminating the need for pickling while maintaining the ability to brazing without flux and sufficiently suppressing MgO-based film formation
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
This approach provides excellent brazability by ensuring uniform exposure of the brazing material's surface, resulting in improved joint quality and reduced maintenance costs by eliminating the need for expensive vacuum equipment and flux application.
Implementation Method 1
Mg in the brazing material is vaporized by heating in vacuum, to break the oxide film on the surface of the material
Implementation Method 2
flux reacts with an oxide film during brazing heating, and breaks the oxide film
Data Source
AI summary
An aluminum alloy brazing sheet used for brazing in an inert gas atmosphere without using flux includes a core material of aluminum or aluminum alloy, and a brazing material of aluminum alloy including Si of 4.0 mass % to 13.0 mass % and cladding one side surface or both side surfaces of the core material. One or both of the core material and the brazing material includes any one or two or more types of X atoms (X is Mg, Li, Be, Ca, Ce, La, Y, and Zr). The aluminum alloy brazing sheet is a brazing sheet in which oxide particles including the X atoms and having a volume change ratio of 0.99 or lower with respect to an oxide film before brazing heating are formed on a surface thereof, by brazing heating.