Austenitic Stainless Steel Composition for Structural Strength
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Solution Overview
Problem
Austenitic stainless steels have lower yield strength and tensile strength compared to carbon steels, and their high alloy content and expensive elements like Ni and Mo limit their use in structural members due to cost and supply issues, while also being less productive in small quantity production.
Innovation Solution
An austenitic stainless steel composition with specific weight percentages of carbon, nitrogen, silicon, manganese, chromium, nickel, and copper, along with a manufacturing process involving hot rolling, hot annealing, cold rolling, and cold annealing, to achieve improved strength, elongation, and productivity, while reducing the content of expensive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high alloy content including expensive elements like Ni and Mo is used to improve corrosion resistance, then corrosion resistance is improved, but manufacturing cost increases and productivity decreases
Solution Approach 1:
The patent changes the chemical composition parameters by reducing expensive alloying elements (Ni: 0.3% or less, Mo: excluded) while increasing cheaper elements (Si: 1.0-2.0%, Mn: 5.0-7.0%, C: 0.06-0.15%). This parameter optimization achieves the desired corrosion resistance and strength without the high costs and supply instability associated with traditional high-Ni, high-Mo compositions
Solution Approach 2:
The patent replaces expensive, supply-unstable elements (Ni, Mo) with cheaper, more readily available elements (Si, Mn, C). This substitution reduces material costs by approximately 50% compared to STS304 and eliminates supply chain vulnerabilities associated with volatile prices of strategic metals
2Strength
If high alloy content is used to improve strength, then strength is improved, but manufacturing cost increases
Solution Approach 1:
The patent achieves high strength (yield strength ≥800 MPa, tensile strength ≥1200 MPa) through optimized composition parameters (C: 0.06-0.15%, Si: 1.0-2.0%, Mn: 5.0-7.0%) combined with specific processing parameters (cold rolling reduction ratio ≥50%, cold annealing temperature 800-1000°C). This approach reduces manufacturing cost by approximately 50% compared to STS304 while meeting structural steel strength requirements
Solution Approach 2:
The patent creates a composite microstructure consisting of austenite phase (≥90% volume fraction) with controlled grain size (≤5 μm). This microstructural design, achieved through the specific composition and processing, provides high strength and ductility without requiring expensive alloying elements
3Ease of operation
If traditional austenitic stainless steel composition is used to ensure formability, then formability is maintained, but strength is insufficient for structural members
Solution Approach 1:
The patent simultaneously achieves high strength (yield strength ≥800 MPa, tensile strength ≥1200 MPa) and excellent formability (elongation ≥20%) through optimized composition parameters (C: 0.06-0.15%, Si: 1.0-2.0%, Mn: 5.0-7.0%, Ni: 0.3% or less) and processing parameters (cold rolling reduction ratio ≥50%, cold annealing temperature 800-1000°C). This resolves the traditional trade-off between strength and formability for structural applications
Solution Approach 2:
The patent creates a composite microstructure of austenite phase (≥90% volume fraction) with fine grain size (≤5 μm). This microstructure provides both the ductility needed for formability (elongation ≥20%) and the strength required for structural members, achieving a balance that traditional single-phase structures cannot provide
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 austenitic stainless steel with a yield strength of 800 MPa or more, a tensile strength of 1200 MPa or more, and elongation of 20-30%, while reducing production costs by about 50% compared to STS304, making it suitable for structural members like vehicles.
Implementation Method 1
hot rolling the slab to a steel sheet
Implementation Method 2
hot annealing the hot-rolled steel sheet
Implementation Method 3
cold rolling the hot-rolled, annealed steel sheet
Implementation Method 4
cold annealing the cold-rolled steel sheet at a temperature of 800 to 1,000°C
Data Source
AI summary
Provided is an austenitic stainless steel having improved strength. This austenitic stainless steel includes, in percent (%) by weight, 0.06 to 0.15% of carbon (C), 0.3% or less (excluding 0) of nitrogen (N), more than 1.0% and equal to or less than 2.0% of silicon (Si), 5.0 to 7.0% of manganese (Mn), 15.0 to 16.0% of chromium (Cr), 0.3% or less (excluding 0) of nickel (Ni), 2.5% or less (excluding 0) of copper (Cu), and the remainder of iron (Fe) and inevitable impurities, and satisfies Expressions (1), (2), and (3) below:15≤0.2Mn+337C+1.2Cu−1.7Cr+3.3Ni+78N−3.5Si+3.0≤30 Expression (1):2.3≤[Cr+1.5Si]/[Ni+0.31Mn+22C+1Cu+14.2N]≤3.0 Expression (2):1.0≤((Cr+1.5Si+18)/(Ni+0.52Cu+30(C+N)+0.5Mn+36)+0.262)*161−161≤7.0 Expression (3):wherein C, N, Si, Mn, Cr, Ni, and Cu refer to contents of the elements, respectively.