Alloy 31 Pipe Fittings
Alloy 31 Pipe Fittings (UNS N08031 / WNR 1.4562)
Alloy 31 Pipe Fittings (UNS N08031 / WNR 1.4562) are premium austenitic nickel-iron-chromium-molybdenum stainless steel fittings designed for extreme corrosion resistance in highly aggressive industrial environments. Often referred to as a “super-austenitic stainless steel,” Alloy 31 offers outstanding resistance to sulfuric acid, phosphoric acid, organic acids, chloride-induced corrosion, and stress corrosion cracking (SCC).
Due to its high chromium, molybdenum, and nitrogen content, Alloy 31 delivers exceptional strength and durability in both oxidizing and reducing conditions. It is widely used in chemical processing, fertilizer plants, mining, flue gas desulfurization, and seawater applications.
Key Features
Exceptional resistance to pitting and crevice corrosion
Ideal for sulfuric acid, phosphoric acid, and chloride media
High mechanical strength with excellent fatigue resistance
Superior resistance to stress corrosion cracking (SCC)
Excellent weldability without risk of sensitization
High resistance to both oxidizing and reducing chemicals
Long service life in harsh and corrosive environments
Outstanding thermal stability and high-temperature strength
Specification
| Specification | Details |
|---|---|
| Material | Alloy 31 |
| UNS | N08031 |
| Werkstoff Nr. | 1.4562 |
| Standard | ASTM B366, ASME SB366 |
| Dimensions | ASME B16.9, B16.28, MSS-SP-43 |
| Types | Seamless, Welded, Buttweld, Fabricated |
| Size Range | ½” to 48” |
| Schedule | SCH 5S to SCH XXS |
| Forms | Elbow, Tee, Reducer, Cap, Stub End, Cross |
| Testing | PMI, IGC Test, Hydro Test, NDT |
Equivalent Grades
| Alloy | UNS | WNR |
|---|---|---|
| Alloy 31 | N08031 | 1.4562 |
Available Sizes
Buttweld Pipe Fittings: ½” – 48”
Forged Fittings: ⅛” – 4”
Schedule: SCH 5S, 10S, 40, 80, 160, XXS
Customized dimensions on request
Chemical Composition
| Element | % Composition |
|---|---|
| Nickel (Ni) | 30 – 32 |
| Chromium (Cr) | 26 – 28 |
| Molybdenum (Mo) | 6 – 7 |
| Nitrogen (N) | 0.15 – 0.20 |
| Iron (Fe) | Balance |
| Carbon (C) | ≤ 0.015 |
| Manganese (Mn) | ≤ 2.0 |
| Silicon (Si) | ≤ 0.8 |
| Phosphorus (P) | ≤ 0.03 |
| Sulfur (S) | ≤ 0.01 |
| Copper (Cu) | 1.0 – 1.4 |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 650 MPa (min) |
| Yield Strength (0.2% offset) | 300 MPa (min) |
| Elongation | 35% (min) |
| Hardness | 290 HB (max) |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.10 g/cm³ |
| Melting Point | 1340 – 1380°C |
| Thermal Conductivity | 11 W/m·K |
| Electrical Resistivity | 1.15 µΩ·m |
| Modulus of Elasticity | 195 GPa |
Types of Alloy 31 Pipe Fittings
Buttweld Fittings
Alloy 31 Elbows (45°, 90°, 180°)
Equal & Reducing Tee
Concentric & Eccentric Reducer
Long & Short Stub Ends
Pipe Caps
Crosses
Forged / Threaded / Socket Weld Fittings
Couplings
Bushings
Plugs
Unions
Elbows
Tees
Reducers
Corrosion Resistance
Alloy 31 offers superior corrosion resistance against:
Sulfuric acid (H₂SO₄) – excellent performance in all concentrations
Hydrochloric & phosphoric acids
Pitting & crevice corrosion in chloride environments
Stress corrosion cracking (SCC)
Marine & seawater exposure
Harsh chemical solvents and organic media
Flue gas desulfurization (FGD) environments
The high chromium, molybdenum, and nitrogen contents significantly improve its resistance to localized corrosion compared to traditional stainless steels.
Heat Resistance
Extremely stable at temperatures up to 600°C
Maintains mechanical strength at elevated temperatures
Excellent oxidation resistance
Suitable for high-temperature chemical processing applications
Heat Treatment
Solution annealing at 1150 – 1200°C
Rapid quenching to maintain corrosion resistance
Stress relief recommended after heavy forming or welding
Avoid prolonged exposure in 600–900°C range to limit sigma phase formation
Welding
Excellent weldability using GTAW, GMAW, SMAW
Use filler metal: ERNiCrMo-13 / Alloy 59 welding consumables
No pre-heating required
Low carbon content prevents intergranular corrosion
Control heat input to maintain weld metal integrity
Fabrication
Suitable for hot and cold forming
Hot working temperature: 1100 – 900°C
Cold working increases strength
Excellent machinability compared to other super-austenitics
Clean tools and working surfaces recommended to avoid contamination
Applications
Chemical & Petrochemical Processing
Sulfuric Acid Manufacturing Plants
Flue Gas Desulfurization (FGD) Systems
Fertilizer Industry
Offshore & Marine Engineering
Mining & Metallurgical Processing
Pharmaceutical and Food Processing
Heat Exchangers, Reactors, Storage Tanks
Pulp & Paper Industry
Desalination Plants & Seawater Systems