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ASTM A182 F51 S31803 Duplex Steel Forged Weldneck Flange 150#-2500# B16.5

This product is a Weld Neck Flange forged and solution-annealed from Duplex Stainless Steel alloy ASTM A182 Grade F51 (UNS S31803), which contains 22% chromium, 5% nickel, 3% molybdenum, and nitrogen. Its dual-phase microstructure (approximately 50% ferrite and 50% austenite) provides an outstanding combination of properties: approximately double the yield strength of standard austenitic stainless steels (e.g., 316L), along with excellent resistance to chloride stress corrosion cracking, pitting, and crevice corrosion, as well as good weldability and toughness.

The tapered hub of the weld neck design ensures facilitating superior stress distribution and making it ideal for high-pressure and high-cycle duty under demanding conditions. Due to its high strength, superior corrosion resistance, and cost-effectiveness, this flange is the preferred solution for critical piping connections in industries such as Oil & Gas (particularly offshore and sour service), Chemical & Petrochemical Processing, Seawater Desalination & Cooling Systems, Pulp & Paper Bleaching Plants, and Flue Gas Desulfurization (FGD) Systems, where handling chloride-containing, acidic, or corrosive media is required.

Chemical & Mechanical Properties

Mechanical Properties

Key Adventages

• Yield strength is approximately double that of 316 stainless steel, allowing for lightweight design. Maintains good impact resistance and ductility.
• Far superior to 316L in chloride-containing environments. Resistant to pitting, crevice corrosion, and general corrosion.
• High hardness and strength provide resistance to erosion and wear in particle-laden media.
• Can be welded with standard procedures, typically without post-weld heat treatment.
• More economical than super duplex steels and nickel alloys for applications requiring both high strength and chloride corrosion resistance.
• Suitable for use from -50°C to +300°C.

Key Applications

• Offshore & Marine Engineering (seawater systems, subsea pipelines)
• Oil & Gas Industry (production and transportation of corrosive fluids)
• Chemical & Petrochemical (process piping, heat exchangers)
• Pulp & Paper Industry (bleaching sections)

Stainless steel flanges Test Certificates

• EN 10204/3.1B,
• Raw Materials Certificate
• 100% Radiography Test Report
• Third Party Inspection Report, etc

Material Testing

• Mechanical Testing Such as Tensile of Area
• Hardness Test
• Chemical Analysis – Spectro Analysis
• Positive Material Identification – PMI Testing
• Flattening Test
• Micro and MacroTest
• Pitting Resistance Test
• Flaring Test
• Intergranular Corrosion (IGC) Test