Heat Exchanger Diffusion Bonding Deformation Control
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Solution Overview
Problem
Diffusion bonding of stainless steel plates in heat exchangers faces challenges such as deformation due to heat expansion and reduced releasability of release members, which can lead to decreased corrosion resistance and surface roughness, especially when using carbon-based release members.
Innovation Solution
Employing release members with a steel material containing 1.5 mass% or more of Si, along with bonding members and release members with suitable high-temperature strength ratios and thermal expansion coefficients, and applying a parting agent to ensure easy detachment and minimize deformation during diffusion bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If carbon-based release members are used for diffusion bonding of stainless steel plates, then thermal resistance and anti-breakage properties are improved, but stainless steel reacts with carbon causing decreased releasability, corrosion resistance, and increased surface roughness
Solution Approach 1:
The patent introduces an intermediary release member made of oxide-free steel between the carbon-based pressurizing means and the stainless steel bonding members. This intermediary layer prevents direct contact and reaction between carbon and stainless steel, while still allowing effective heat and pressure transmission for diffusion bonding. The release member acts as a mediator that protects the stainless steel from carbon contamination.
2Strength
If stainless steel plates are subjected to diffusion bonding with high pressure and high temperature, then bonding strength is improved, but heat-deformation occurs causing expansion toward the flow path side
Solution Approach 1:
The patent applies counterbalancing pressure through the release member and pressurizing means to counteract the thermal expansion forces during diffusion bonding. By maintaining controlled pressure on both sides of the stainless steel plate, the system prevents unidirectional expansion toward the flow path side, thereby reducing heat-deformation while still achieving strong bonding.
3Productivity
If diffusion bonding is performed with carbon-based release members, then bonding efficiency is improved, but releasability of the release member from the plate member decreases
Solution Approach 1:
The oxide-free steel release member serves as an intermediary layer that prevents direct adhesion between the carbon-based pressurizing means and the stainless steel bonding members during diffusion bonding. This intermediary layer allows for efficient bonding while maintaining easy releasability after the bonding process, as the release member can be cleanly separated from both the carbon pressurizing means and the stainless steel plates.
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 method effectively suppresses deformation and maintains diffusion bonding properties while ensuring excellent releasability and corrosion resistance of stainless steel plates, even after diffusion bonding treatment.
Implementation Method 1
release members including a steel material containing 1.5 mass% or more of Si
Implementation Method 2
bonding method which takes advantage of interdiffusion of atoms of a base material occurring at a bonding interface at high temperature and high pressure
Implementation Method 3
heat-deformation may occur in which a plate member is expanded toward the side of a flow path at the portion of the non-bonded surface by heating
Data Source
Figure 1~2
Figure 3A~3B
Figure 4
AI summary
Provided is a method of manufacturing a heat exchanger by diffusion bonding in which deformation of bonding members as stainless steel plates is suppressed, and releasability (detachability of a bonding member from a release member) after diffusion bonding treatment is excellent. Provided is a method of manufacturing a heat exchanger, the method including layering a plurality of bonding members 1 made of stainless steel, and applying heat and pressure to effect diffusion bonding of the bonding members 1, in which release members 3 are arranged on the both surface sides of the bonding members 1, and holding jigs 4 are arranged so as to sandwich the bonding members 1 through the release members 3, and pressing is then performed through the holding jigs 4 with a pressure device, and in which the diffusion bonding is performed using a combination of the release members 3 and the bonding members 1, the release members 3 including a steel material containing 1.5 mass% or more of Si, and a ratio (Fr/Fp) of the high-temperature strength (Fr) of the release members 3 at 1000ºC to the high-temperature strength (Fp) of the bonding members 1 at 1000ºC being 0.9 or more.