Fuel Cell Controller Heat Treatment for Stainless Steel Embrittlement
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Solution Overview
Problem
High-temperature fuel cells, particularly solid oxide fuel cells, face issues with 475°C embrittlement in stainless steel components, leading to potential breakage due to Cr-rich Fe—Cr phase formation, which existing methods attempt to mitigate through additional components and surface polishing, increasing costs and reducing long-term embrittlement resistance.
Innovation Solution
A fuel cell system with a controller that adjusts the temperature of the fuel cell stack to a predetermined temperature higher than the embrittlement threshold for a set time, eliminating the Cr-rich Fe—Cr phase by transitioning it to a phase with suppressed Fe and Cr distribution, without adding components or performing surface polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Cr content in ferrite stainless steel is increased to suppress steam oxidation damage, then oxidation resistance is improved, but 475°C embrittlement susceptibility increases
Solution Approach 1:
The patent optimizes the Cr content parameter to a specific range (11-20 mass%) that balances oxidation resistance and embrittlement resistance. This parameter optimization resolves the contradiction by finding the optimal value that provides sufficient oxidation protection while limiting 475°C embrittlement susceptibility.
Solution Approach 2:
The patent creates a composite oxide film structure on the stainless steel surface containing Cr-based oxide and other metal oxides. This composite film provides both oxidation resistance and embrittlement resistance by combining the protective properties of different oxide components.
2Reliability
If additional components are added to stabilize the oxide film, then oxidation resistance is improved, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the composition parameters of the oxide film to achieve stable protection using primarily Cr-based oxide with controlled amounts of other metals. This compositional optimization provides effective oxidation resistance while controlling material costs.
Solution Approach 2:
The patent creates a localized oxide film structure on the surface of the stainless steel with specific compositional characteristics. This localized protective layer provides oxidation resistance at the surface without requiring expensive alloying of the bulk material.
3Reliability
If surface polishing is performed to stabilize the oxide film, then oxidation resistance is improved, but embrittlement resistance deteriorates over time
Solution Approach 1:
The patent creates a composite oxide film containing Cr-based oxide and other metal oxides that forms a stable, adherent protective layer. This composite structure provides both oxidation resistance and maintains embrittlement resistance by avoiding the surface alteration problems associated with mechanical polishing.
4Productivity
If the operating temperature is maintained at the first predetermined temperature for fuel cell operation, then power generation efficiency is optimized, but 475°C embrittlement occurs in stainless steel
Solution Approach 1:
The patent optimizes the Cr content parameter in the stainless steel composition to a range (11-20 mass%) that allows the material to maintain both embrittlement resistance and power generation efficiency at the operating temperature. This compositional parameter optimization enables operation at the optimal power generation temperature without suffering from 475°C embrittlement.
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
Prevents stainless steel members from breaking due to 475°C embrittlement by effectively eliminating the Cr-rich Fe—Cr phase, improving durability and maintaining embrittlement resistance without increasing costs or altering the surface, thus enhancing the fuel cell system's reliability and longevity.
Implementation Method 1
the controller controls such that the first temperature reaches a temperature higher than or equal to a second predetermined temperature for a predetermined time. The second predetermined temperature is a temperature at which 475° C. embrittlement that occurs on stainless steel is eliminated.
Implementation Method 2
The controller controls such that the first temperature reaches a temperature higher than or equal to a second predetermined temperature for a predetermined time. The second predetermined temperature is a temperature at which 475° C. embrittlement that occurs on stainless steel is eliminated.
Data Source
AI summary
A fuel cell system includes a fuel cell stack constituted by cells, each of the cells includes a fuel electrode, an air electrode, and an electrolyte, and generate electric power through a reaction of a fuel gas and air, a casing that houses the fuel cell stack, a temperature detector that detects a first temperature, the first temperature is a temperature of the fuel cell stack or inside the casing, and a controller. The controller controls based on the first temperature so as to allow an operation at a first predetermined temperature. The controller controls such that the first temperature reaches a temperature higher than or equal to a second predetermined temperature for a predetermined time. The second predetermined temperature is a temperature at which 475° C. embrittlement that occurs on stainless steel is eliminated. The first predetermined temperature is lower than the second predetermined temperature.