Pasty Aluminum Brazing Composition for Dimensional Accuracy
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Solution Overview
Problem
Conventional aluminum brazing methods using brazing sheets or powders face challenges with dimensional accuracy, surface roughness, and manufacturing costs, as well as limitations in achieving uniform thickness and stable quality.
Innovation Solution
A pasty composition for aluminum brazing is developed, comprising an aluminum-containing powder with specific particle size distribution, a fluoride-based flux, and a binder, which provides excellent coating properties and flowability, allowing for favorable dimensional accuracy and external appearance of brazed portions without requiring additional equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If brazing sheet (clad metal) is used for brazing aluminum-containing members, then the brazing filler metal is applied to portions to be brazed, but the brazing filler metal is also joined on portions other than those which should be brazed, causing manufacturing cost to increase
Solution Approach 1:
The invention applies local quality by using powder brazing filler metal that can be precisely applied only to the specific portions requiring brazing, rather than having filler metal on entire sheets. This localized application prevents unwanted brazing in non-target areas and reduces overall filler metal consumption while maintaining effective brazing at required locations.
Solution Approach 2:
The invention extracts the brazing filler metal from a continuous sheet form and converts it to discrete powder form. This extraction allows the filler metal to be applied only where needed, eliminating the waste associated with sheet-based methods where filler metal is present across entire surfaces but only required at specific joints.
2Reliability
If brazing sheet (clad metal) is used for brazing aluminum-containing members, then brazing can be conducted, but the clad metal has to have a thickness of at least approximately 60 μm due to manufacturing limitations
Solution Approach 1:
The invention changes the form parameter of the brazing filler metal from thick sheet (minimum 60 μm) to fine powder with controlled particle size distribution (D10: 5-20 μm, D50: 20-50 μm, D90: 50-100 μm). This parameter change enables the use of much thinner effective filler metal layers while maintaining brazing reliability, as the powder can be applied in controlled amounts and distributed uniformly.
Solution Approach 2:
The invention uses a composite material system consisting of aluminum-containing powder (90-99 wt%), silicon powder (0.1-10 wt%), and zinc powder (0.1-10 wt%). This composite composition provides reliable brazing performance while allowing for much thinner effective filler metal application compared to conventional sheet materials, as the fine particles can be densely packed and distributed at low total thickness.
3Manufacturing precision
If conventional brazing filler metal powders are used for aluminum brazing, then brazing can be conducted, but dimensional accuracy of products obtained after brazing is insufficient and erosion (deterioration in surface roughness) is caused
Solution Approach 1:
The invention changes the particle size distribution parameters of the brazing filler metal to achieve optimal flowability and coating properties. By controlling D10 (5-20 μm), D50 (20-50 μm), and D90 (50-100 μm) within specific ranges, the powder achieves good flowability (15-80 seconds/50g) that enables uniform application and controlled melting, thereby improving dimensional accuracy and reducing surface erosion caused by poor flow characteristics.
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 composition achieves favorable fillet formation without black-tarnishing or white residues, ensuring a smooth work environment and reducing manufacturing costs by utilizing existing equipment, while maintaining dimensional accuracy and evenness in the brazing process.
Implementation Method 1
In a case where on a cumulative grading curve plotted in a graph in which Q volume % showing a percentage of a volume of particles, in the aluminum-containing powder, whose particle diameter is each less than or equal to D μm is represented with a horizontal axis showing D μm and a vertical axis showing Q volume %, the particle diameter D μm which corresponds to the Q volume % is indicated as D(Q) μm, D(50) μm is greater than or equal to 20 μm and less than or equal to 150 μm; and D(90) μm/D(10) μm is less than or equal to 5
Implementation Method 2
EP 1127653 A2 discloses a flux-containing composition for brazing aluminum comprising a) a fluoride flux
Implementation Method 3
EP 1127653 A2 discloses a flux-containing composition for brazing aluminum comprising... b) at least one binder selected from the group consisting of an alkyd resin, a mixture of an alkyd resin and a butyl rubber
Data Source
Figure 1~2
AI summary
Provided are a pasty composition for aluminum brazing which has excellent coating properties, is capable of attaining favorable dimensional accuracy of products obtained after brazing, causes less erosion, and allows favorable external appearances of brazed portions (fillets); an aluminum-containing member coated with the pasty composition for aluminum brazing; and a method, using the pasty composition for aluminum brazing, for brazing the aluminum-containing members. The pasty composition for aluminum brazing contains an aluminum-containing powder. In a case where on a cumulative grading curve of the aluminum-containing powder, a particle diameter D µm which corresponds to a Q volume % is indicated as D(Q) µm, D(50) µm is greater than or equal to 20 µm and less than or equal to 150 µm; and D(90) µm/D(10) µm is less than or equal to 5. A mass percentage of particles, in the aluminum-containing powder, which pass through a screen mesh having an opening of 45 µm is less than or equal to 50 %. A flowability of the aluminum-containing powder is less than or equal to 80 seconds/50 g.