Austenitic Stainless Steel Hydrogen Embrittlement Resistance
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Solution Overview
Problem
Current austenitic stainless steels, such as SUS304 and SUS316, face challenges with hydrogen embrittlement and require higher strength and stability for hydrogen-based applications, while also needing to reduce costs and size, with existing solutions not adequately addressing the balance between strength, elongation, and hydrogen resistance.
Innovation Solution
Austenitic stainless steel with a specific chemical composition and microstructure refinement, including a grain size of 10.0 μm or less, a defined difference in lattice constant between surface and center portions, and a high diffraction peak integrated intensity ratio, promoting nitrogen absorption and stability, which inhibits hydrogen embrittlement and maintains strength and elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If SUS304 is used to achieve good balance between strength and elongation, then strength and elongation are improved, but hydrogen embrittlement susceptibility increases
Solution Approach 1:
The patent changes the chemical composition parameters by strictly limiting carbon content to 0.03% or less (compared to conventional SUS304 which allows up to 0.08%), and optimizes nickel content to 8-13%. It also introduces optional microalloying elements (Ti, Nb, V) at controlled levels. These parameter changes stabilize the austenite phase, preventing martensite transformation that would otherwise increase hydrogen embrittlement susceptibility while maintaining strength properties.
Solution Approach 2:
The patent creates a composite microstructure by combining controlled amounts of microalloying elements (Ti, Nb, V) with the base SUS304 composition. These elements form fine precipitates that strengthen the matrix while the optimized Ni content maintains austenite stability. This composite approach achieves both high strength and resistance to hydrogen embrittlement.
2Reliability
If SUS316 is used to achieve high austenite stability and low hydrogen embrittlement susceptibility, then reliability is improved, but strength remains low
Solution Approach 1:
The patent extracts the essential function of nickel (austenite stabilization and hydrogen embrittlement resistance) from the SUS316 composition, while removing the unnecessary molybdenum content (limiting it to 0.05% or less). By optimizing nickel to 8-13% and eliminating excess Mo, the patent achieves SUS316-like hydrogen resistance without sacrificing strength, as the higher Ni content can be processed to achieve superior mechanical properties.
Solution Approach 2:
The patent changes the compositional parameters by limiting Mo to 0.05% or less (much lower than SUS316's typical 2-3% Mo), while optimizing Ni to 8-13%. It also introduces microalloying elements for precipitation strengthening. These parameter changes enable the steel to achieve both high strength and hydrogen embrittlement resistance without requiring high Mo content.
3Reliability
If Ni content is increased to maintain austenite stability, then hydrogen embrittlement resistance is improved, but cost increases due to Ni being an expensive rare metal
Solution Approach 1:
The patent optimizes the nickel content to a specific range of 8-13%, which is higher than conventional SUS304 (typically 8-10.5% Ni) but provides sufficient austenite stability. Combined with strict carbon control (≤0.03%) and optional microalloying, this optimized composition achieves the desired hydrogen embrittlement resistance at a controlled cost, avoiding excessive Ni addition.
Solution Approach 2:
The patent introduces cheap microalloying elements (Ti, Nb, V) at very low levels (0.01-0.05% each) as substitutes for expensive nickel. These elements provide precipitation strengthening and contribute to austenite stability through carbide/nitride formation, reducing the reliance on costly nickel while maintaining hydrogen embrittlement resistance.
4Productivity
If strength is increased to reduce system size and weight, then productivity is improved, but hydrogen embrittlement susceptibility increases
Solution Approach 1:
The patent creates a composite microstructure with fine precipitates from microalloying elements (Ti, Nb, V) dispersed in an optimized austenitic matrix. This composite structure provides precipitation strengthening that increases strength without requiring phase transformation, thereby avoiding the hydrogen embrittlement susceptibility that would result from martensite formation. The result is high strength for reduced system weight while maintaining hydrogen resistance.
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 an industrially stable, cost-effective SUS304-based austenitic stainless steel that prevents embrittlement in hydrogen environments, achieving an excellent balance between strength and elongation, while inhibiting hydrogen penetration effectively.
Implementation Method 1
increases a solubility of nitrogen in a rolled steel sheet by causing the rolled steel sheet to absorb nitrogen
Implementation Method 2
annealing an austenitic stainless steel in a nitrogen gas atmosphere
Implementation Method 3
have a modified surface film, typical of stainless steels, for inhibiting the penetration of hydrogen
Implementation Method 4
have an increased surface nitrogen concentration
Data Source
AI summary
An austenitic stainless steel according to the present invention has a chemical composition containing, by mass %: C: 0.01 to 0.15%; Si: 2.0% or less; Mn: 3.0% or less; Cr: 10.0 to 20.0%; Ni: 5.0 to 13.0%; N: 0.01 to 0.30%; Nb: 0 to 0.5%; Ti: 0 to 0.5%; and V: 0 to 0.5%, with the balance: Fe and impurities, wherein an average grain size is 10.0 μm or less, a difference in value of an average lattice constant dAve. (={dγ(111)×Iγ(111)+dγ(200)×Iγ(200)+dγ(220)×Iγ(220)+dγ(311)×Iγ(311)}/{Iγ(111)+Iγ(200)+Iγ(220)+Iγ(311)}) of an austenite phase between a surface portion and a center portion is 0.010 Å or more, and a value of a diffraction peak integrated intensity ratio r (=100×ΣIγ/ΣIALL) at a surface is 95% or more.