Brazing Alloy Blend for Pore-Free Plate Heat Exchanger Joints
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Solution Overview
Problem
Brazing materials used in plate heat exchangers often result in either porous joints or erosion of the base material due to melting point depressants, which can lead to 'burn-through' and reduced joint strength, especially when using nickel or stainless steel with Silicon, Boron, and Phosphorous as melting point depressants.
Innovation Solution
A brazing material comprising a blend of grains with solidus and liquidus temperatures lower than the brazing temperature and grains with temperatures above the brazing temperature, where the ratio of melting to non-melting materials ensures a solidus temperature below and liquidus temperature above the brazing temperature, respectively, reducing porosity and erosion by controlling the migration of melting point depressants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a stainless steel based brazing material with melting point depressants (Silicon, Boron, Phosphorous) is used, then the brazing temperature can be lowered, but the melting point depressants migrate into the base material causing erosion and burn-through
Solution Approach 1:
The brazing material is divided into two distinct components: melting grains (stainless steel with melting point depressants) and non-melting grains (stainless steel without or with minimal melting point depressants). This segmentation allows the melting grains to lower the brazing temperature while the non-melting grains remain stationary to absorb migrating depressants and prevent base material erosion
Solution Approach 2:
Different regions of the brazing material have different properties: the melting grains provide localized melting and flow to fill joints at lower temperatures, while the non-melting grains provide localized stability and act as sinks for migrating melting point depressants, preventing harmful migration to the base material
2Object-affected harmful factors
If the amount of melting point depressants is reduced so the brazing material does not melt, then erosion is minimized, but the joint becomes porous and weak
Solution Approach 1:
The brazing material is segmented into melting and non-melting components, where the melting grains (even in small amounts) provide sufficient liquid phase to create strong joints without requiring high overall depressant content, while non-melting grains maintain joint density and strength
Solution Approach 2:
The invention changes the parameter of melting point depressant concentration by creating a bimodal distribution: some grains have high depressant content (melting grains) while others have low or no depressants (non-melting grains), allowing the system to achieve both low erosion and high joint 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 strong, pore-free brazing joints with minimal erosion of the base material, as the melting point depressants primarily migrate into non-melting grains, preventing the base material from melting and maintaining joint integrity.
Implementation Method 1
grains of a melting brazing material having solidus and liquidus temperatures lower than a brazing temperature
Implementation Method 2
the melting point depressants primarily migrate into non-melting grains
Data Source
AI summary
A brazing material for brazing a brazed plate heat exchanger comprising a number of heat exchanger plates being provided with a pressed pattern of ridges and grooves adapted to provide contact points between neighbouring heat exchanger plates, such that the heat exchanger plates are kept on a distance from one another and such that interplate flow channels for media to exchange heat are formed between the heat exchanger plates comprises a brazing alloy comprising at least one melting point depressing element and metals resembling the composition of the heat exchanger plates. The brazing material comprises a mixture between grains of a melting brazing material having solidus and liquidus temperatures lower than a brazing temperature and a non-melting brazing material having solidus and liquidus temperatures above the brazing temperature. The ratio between the melting and non-melting brazing materials is such that an alloy formed by the melting and non-melting brazing materials has a solidus temperature lower than the brazing temperature and a liquidus temperature higher than the brazing temperature.