S31803 Duplex Stainless Steel WNRF Flange
Product Overview
Forged Duplex Stainless Steel Flanges for High-Integrity Piping Systems
S31803 Welding Neck Raised Face (WNRF) Flanges are manufactured from duplex stainless steel combining an approximately balanced ferritic-austenitic microstructure. Compared with conventional austenitic stainless steels, UNS S31803 offers higher yield strength together with improved resistance to chloride-induced pitting, crevice corrosion and stress corrosion cracking.
The welding neck design provides gradual stress distribution between the flange hub and pipe, making it suitable for cyclic pressure and elevated mechanical loading. Raised Face (RF) sealing surfaces are precision machined to achieve reliable gasket compression and leak-tight flange joints across a wide range of industrial piping systems.
Available in accordance with ASME B16.5, EN 1092-1 and project-specific requirements, flanges can be supplied with complete material traceability and inspection documentation.
Technical Specifications
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Item
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Specification
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Product Name
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S31803 Duplex Stainless Steel WNRF Flange
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Material Grade
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UNS S31803 / ASTM A182 F51
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Standard
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ASME B16.5, EN 1092-1, MSS SP-44
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Flange Type
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Welding Neck Raised Face (WNRF)
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Pressure Rating
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Class 150–2500 / PN10–PN100
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Facing
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RF (Raised Face), FF, RTJ Available
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Manufacturing Process
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Open Die Forging + CNC Machining
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Heat Treatment
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Solution Annealed
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NPS Range
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1/2"–48"
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Inspection
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PMI, UT, PT, Hardness, Dimensional Inspection
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Certification
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EN 10204 3.1 / 3.2
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Chemical Composition
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Element
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Requirement (%)
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Chromium
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21.0–23.0
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Nickel
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4.5–6.5
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Molybdenum
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2.5–3.5
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Nitrogen
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0.08–0.20
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Carbon
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≤0.03
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Mechanical Properties
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Property
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Typical Requirement
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Tensile Strength
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≥620 MPa
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Yield Strength
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≥450 MPa
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Elongation
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≥25%
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Hardness
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≤290 HB
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Product Features
- Duplex Microstructure for Enhanced Mechanical Performance
The dual-phase ferritic-austenitic structure delivers higher strength than conventional 300-series stainless steels while maintaining good toughness.
- Superior Resistance to Chloride-Induced Corrosion
Suitable for chloride-containing media where pitting, crevice corrosion and stress corrosion cracking are design considerations.
- Optimized Welding Neck Geometry
The tapered hub minimizes stress concentration and improves fatigue resistance under cyclic loading.
- Precision Machined Raised Face
Controlled facing dimensions ensure reliable gasket seating and sealing integrity.
- Full Material Traceability
Each flange can be supplied with heat number traceability and inspection records to support project documentation.
Typical Applications
Equivalent Material Grades
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Standard
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Grade
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ASTM
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A182 F51
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UNS
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S31803
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EN
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1.4462
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DIN
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X2CrNiMoN22-5-3
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AFNOR
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Z3 CrNi 22.05 Az
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GB/T
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022Cr22Ni5Mo3N
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Inspection & Testing
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Positive Material Identification (PMI)
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Ultrasonic Testing (UT)
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Liquid Penetrant Testing (PT)
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Ferrite Content Measurement
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Hardness Testing
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Dimensional Inspection
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EN 10204 3.1 / 3.2 Documentation
FAQ
1. Why choose S31803 instead of 316L?
S31803 provides higher strength and improved resistance to chloride-induced pitting, crevice corrosion and stress corrosion cracking, making it suitable for more demanding service environments.
2. What pressure classes are available?
Class 150 to Class 2500 and equivalent PN ratings can be supplied according to ASME or EN standards.
3. Can customized flange dimensions be manufactured?
Yes. Special drilling patterns, non-standard thicknesses and project-specific dimensions can be produced based on customer drawings.
4. What inspection documents are available?
EN 10204 3.1 or 3.2 certificates, PMI reports, UT/PT reports and dimensional inspection records are available upon request.
① PREN Comparison
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Material
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Typical PREN
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316L
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24–26
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S31803 (2205)
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35–38
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S32750 (2507)
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≥40
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② S31803 vs S32205
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Item
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S31803
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S32205
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Chemical Composition
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ASTM Minimum Requirements
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Narrower Chemistry Range
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Mechanical Properties
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Equivalent
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Equivalent
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Typical Supply
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Widely Used
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Often Dual Certified (S31803/S32205)
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③ Flange Facing Types
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Facing Type
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Typical Application
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RF
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General Process Piping
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FF
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Flat Face Connections
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RTJ
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High Pressure & High Temperature Service
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Technical Terminology
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PREN (Pitting Resistance Equivalent Number)
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Ferrite Content Control
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Sigma Phase Prevention
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Solution Annealing
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Heat Number Traceability
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Butt-Weld Transition
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Gasket Seating Stress
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Stress Corrosion Cracking (SCC) Resistance
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Crevice Corrosion Resistance
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Hydrogen Sulfide (H₂S) Service
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NACE MR0175 / ISO 15156 Compatibility
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