Two-Phase Stainless Steel Diaphragm for High Strength and Corrosion Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional metal diaphragms in pressure sensors face challenges in achieving high strength, excellent corrosion resistance, and maintaining a smooth surface condition, especially in non-oxidizing and strongly oxidizing environments, which affects their accuracy and durability.
Innovation Solution
A diaphragm made of two-phase stainless steel with a composition of 24 to 26% Cr, 2.5 to 3.5% Mo, 5.5 to 7.5% Ni, 0.03% or less C, 0.08 to 0.3% N, 1.5% or less Mn, and 1.0% or less Si, subjected to cold working and aging heat treatment at 350 to 500°C, achieving a 0.2% proof stress of 1288 MPa or higher and fracture elongation of 6% or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal diaphragm materials (Co based alloy, Ni based alloy, precipitation-hardened stainless steel) are used, then corrosion resistance is improved, but strength and surface smoothness deteriorate in non-oxidizing and strongly oxidizing environments
Solution Approach 1:
The invention uses a two-phase stainless steel composite material consisting of austenite and ferrite phases. This composite structure combines the corrosion resistance of stainless steel with enhanced strength through the dual-phase microstructure, achieving both high strength and excellent corrosion resistance in challenging environments.
Solution Approach 2:
The invention optimizes specific compositional parameters (Cr: 18-30%, Ni: 3-8%, Mo: 0.1-3%, N: 0.01-0.05%) and microstructural parameters (austenite-ferrite phase ratio) to achieve the desired balance between strength and corrosion resistance. The controlled composition and phase distribution enable the material to maintain both properties simultaneously.
2Strength
If precipitation-hardening treatment is performed to increase strength, then strength is improved, but surface smoothness and corrosion resistance deteriorate
Solution Approach 1:
The invention changes the material composition parameters (specific Cr, Ni, Mo, and N content ranges) and heat treatment parameters (aging temperature and time) to achieve high strength through age hardening rather than precipitation hardening. This alternative hardening mechanism maintains surface smoothness while providing the required strength.
Solution Approach 2:
The invention creates local microstructural quality differences through the dual-phase structure, where the austenite and ferrite phases are distributed at the microscale to provide both strength and surface integrity, avoiding the surface degradation associated with conventional precipitation hardening.
3Strength
If cold working of 20% or higher is performed to increase strength, then strength is improved, but surface smoothness and ductility deteriorate
Solution Approach 1:
The invention optimizes the composition parameters (particularly Cr: 18-30% and Ni: 3-8%) to enable the material to achieve high strength through controlled age hardening at 350-500°C with minimal cold working. This reduced cold working preserves both surface smoothness and ductility while achieving the required strength level.
Solution Approach 2:
The dual-phase austenite-ferrite microstructure acts as a composite that provides both strength and ductility. The ferrite phase contributes to strength while the austenite phase maintains ductility and surface quality, allowing the material to withstand minimal cold working without significant loss of properties.
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 two-phase stainless steel diaphragm provides higher strength, excellent corrosion resistance, and a smooth surface, ensuring accurate pressure sensing performance even in corrosive environments and maintaining mechanical integrity under high pressures.
Implementation Method 1
performing aging heat treatment at a temperature from 350°C to 500°C for at least 0.5 hours to provide a 0.2% proof stress of 1288 MPa or higher
Implementation Method 2
The two-phase stainless steel diaphragm provides higher strength, excellent corrosion resistance, and a smooth surface
Implementation Method 3
a transpassive potential in an 0.2 mol/l phosphoric acid solution is 1.2 V (v.s RHE) or higher
Data Source
Figure 1
Figure 2
Figure 3
AI summary
It is an object of the present invention to provide a metal diaphragm capable of achieving a higher strength, excellent corrosion resistance, and a smooth surface condition, and a pressure sensor including the diaphragm. The diaphragm according to the present invention includes a two-phase stainless steel having a composition of 24 to 26 mass% Cr, 2.5 to 3.5 mass% Mo, 5.5 to 7.5 mass% Ni, 0.03 mass% or less C, 0.08 to 0.3 mass% N, and the balance Fe and inevitable impurities, and having a 0.2% proof stress of 1300 MPa or higher.