Aluminium Brazing Sheet Fluxless CAB
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Solution Overview
Problem
Conventional brazing sheet materials for heat exchangers lack sufficient post-braze strength and corrosion resistance, particularly when brazed in a fluxless controlled atmosphere, and often require costly vacuum brazing processes.
Innovation Solution
A brazing sheet material comprising a core alloy layer with a significant Mg content, bonded to a 4000-series aluminium brazing clad layer, allowing for fluxless controlled atmosphere brazing (CAB) without the need for interlayers, resulting in enhanced post-braze strength and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional brazing sheet materials are used for fluxless controlled atmosphere brazing, then the brazing process can be simplified, but the post-braze strength and corrosion resistance are insufficient
Solution Approach 1:
The core alloy composition is modified by specifying precise ranges for Mg (1.0-3.0%), Mn (0.0-1.8%), Cu (0.0-0.1%), Si (0.0-0.7%), and Fe (0.0-0.7%), along with optional additions of Zr, Cr, Hf, Ti, and Zn. These compositional parameter changes enable the material to achieve both fluxless brazability and enhanced post-braze strength without requiring vacuum brazing processes
Solution Approach 2:
The invention uses a composite structure consisting of a core alloy layer with specific composition bonded to a 4000-series aluminium brazing clad layer containing 6-14% Si. This composite material design allows the core to provide mechanical strength while the clad layer facilitates fluxless brazing, resolving the contradiction between ease of manufacture and strength
2Ease of manufacture
If conventional brazing sheet materials are used, then manufacturing cost may be lower, but corrosion resistance in brackish and sea water environments is inadequate
Solution Approach 1:
The core alloy composition is optimized with Mg content of 1.0-3.0% and controlled levels of Mn, Cu, Si, and Fe, which collectively enhance corrosion resistance in marine environments. This compositional adjustment maintains manufacturing feasibility while dramatically improving reliability in corrosive conditions
Solution Approach 2:
The composite structure of a corrosion-resistant core alloy layer bonded to a 4000-series aluminium brazing clad layer provides both economic manufacturability and superior corrosion resistance. The specific composition ranges ensure the material can withstand brackish and sea water environments without requiring expensive alternative materials or additional protective coatings
3Strength
If vacuum brazing is used to achieve high post-braze strength, then strength is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The invention extracts and eliminates the requirement for vacuum brazing equipment and complex process controls by developing a core alloy composition that enables fluxless controlled atmosphere brazing. The specific alloying elements and their ranges allow the material to achieve high post-braze strength through simpler, more economical brazing processes
Solution Approach 2:
By modifying the core alloy composition with specific ranges of Mg, Mn, Cu, Si, and Fe, along with optional additions, the material achieves enhanced post-braze strength that previously required vacuum brazing. This compositional parameter change allows the use of simpler controlled atmosphere brazing equipment while maintaining or improving strength
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 provides increased post-braze strength and corrosion resistance, eliminating the need for flux residues and costly vacuum brazing, while maintaining high performance in brackish and sea water environments.
Implementation Method 1
a core alloy layer bonded on at least one side with an aluminium brazing clad layer or layers
Implementation Method 2
the aluminium clad layer is made of a 4xxx-series alloy comprising silicon in an amount in the range of 4% to 20% by weight, and preferably in the range of about 6% to 14% by weight. The aluminium clad layer has a liquids temperature typically in the range of about 540°C to 615°C
Data Source
AI summary
The invention relates to a brazing sheet material comprising of a core alloy layer bonded on at least one side with an aluminium brazing clad layer or layers forming a filler material of a 4000-series aluminium alloy, wherein the core layer is made from an aluminium alloy having (in wt.%): Mg 1.0 to 3.0, Mn 0 to 1.8, Cu 0 to 0.8, Si 0 to 0.7, Fe 0 to 0.7, optionally one or more elements selected from the group (Zr, Cr, Hf, T), Zn 0 to 0.5, impurities and aluminium, and wherein the filler material forms a 4000-series aluminium alloy further comprising one or more wetting elements selected from the group consisting of: Bi 0.03-0.5, Pb 0.03-0.5, Sb 0.03- 0.5, Li 0.03-0.5, Se 0.03-0.5, Y 0.03-0.05, Th 0.03-0.05, and the sum of these elements being 0.5% or less.