Three-Layer Brazing Sheet for Flux-Free Inert Gas Brazing
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Solution Overview
Problem
Current brazing methods for vehicle heat exchangers face challenges such as the need for flux in Control Atmosphere Brazing (CAB) methods, which complicates the process and poses environmental risks, and the low productivity and high costs associated with Vacuum Brazing (VB) methods, while also struggling to achieve effective brazing without flux and maintaining core material strength.
Innovation Solution
A brazing sheet with a three-layer structure, comprising a core material, an intermediate layer, and a brazing material layer, optimized with specific alloy compositions and additions like Bi and Zn, allowing for flux-free brazing under inert gas atmospheres, with the intermediate layer acting as a sacrificial anode to inhibit corrosion and improve fillet formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flux is used in CAB methods to break down oxide film, then brazing can be achieved, but the process complexity increases and environmental risks arise from flux residue
Solution Approach 1:
The invention extracts and eliminates the flux component from the brazing process by developing a flux-free CAB method that uses controlled inert gas atmosphere and optimized brazing sheet composition to achieve oxide film breakdown without external flux agents
Solution Approach 2:
The invention introduces an intermediate layer between the core material and brazing material layer that acts as a mediator to facilitate oxide film breakdown and improve brazing quality without requiring flux, using controlled atmosphere and material composition
2Reliability
If flowability of brazing material is increased to enable flux-free brazing, then brazing can be achieved without flux, but erosion on core material increases and strength decreases
Solution Approach 1:
The invention applies local quality by creating distinct layers with different compositions and properties: the intermediate layer has specific composition to protect the core material from erosion while the brazing material layer has optimized flowability for effective bonding
Solution Approach 2:
The invention uses composite material structure with multiple layers (core material, intermediate layer, brazing material layer) where each layer has optimized composition to achieve overall system performance that balances flowability and erosion resistance
3Object-affected harmful factors
If VB methods are used to eliminate flux, then environmental risks are eliminated, but productivity decreases and manufacturing costs increase due to vacuum requirements
Solution Approach 1:
The invention uses controlled inert gas atmosphere (nitrogen or argon) at atmospheric pressure instead of vacuum conditions, eliminating the need for vacuum equipment while maintaining flux-free brazing and enabling higher productivity with simpler, more cost-effective manufacturing
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 enables clean, cost-effective, and high-productivity brazing with improved erosion resistance and brazing properties, eliminating the need for flux and achieving satisfactory bonding without vacuum conditions.
Implementation Method 1
the Mg breaks down the oxide film on the brazing material layer of the cladded material during the brazing processing in the high temperature environment within the vacuum furnace
Implementation Method 2
evaporated Mg captures traces of oxygen and moisture, which are brazing inhibitory substances which, exist near the surface
Implementation Method 3
evaporated Mg captures traces of oxygen and moisture
Implementation Method 4
the molten and flowed brazing material fills the gap between the adherend due to surface tension and causes a bond
Data Source
AI summary
A brazing sheet may be used for brazing under an atmosphere of an inert gas without flux. The brazing sheet may include at least three layers. The at least three layers may include a core material, a brazing material layer, and an intermediate layer. The at least three layers may be cladded by an outermost layer of the brazing material layer. The intermediate layer may be disposed on a face of the core material. The core material may be composed of a first aluminum alloy including at least one of (i) 0.20 weight % to 1.0 weight % of Cu, (ii) 0.8 weight % to 1.8 weight % of Mn, and (iii) 0.25 weight % to 1.5 weight % of Mg. The intermediate layer may be composed of a second aluminum alloy including 0.20 weight % or less of each of Si and Fe and 0.10 weight % or less of each of Cu, Mn, and Cr.