ASTM A789 UNS S31200 Duplex Stainless Steel Pipe
ASTM A789 UNS S31200 Duplex Stainless Steel Pipe Data & Properties
Complete material data for ASTM A789 UNS S31200 duplex stainless steel pipe including chemical composition, mechanical and physical properties, equivalents, and application in chemical, oil & gas industries.
Hot forming, cold forming, welding, machining, solution annealing
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ASTM A789 UNS S31200 Duplex Stainless Steel Pipe Introduction
ASTM A789 UNS S31200 is a duplex (ferritic-austenitic) stainless steel offering high strength and excellent resistance to pitting, crevice corrosion, and stress corrosion cracking. With a typical composition of 25% Cr, 6% Ni, 1.5% Mo, and controlled nitrogen addition, it delivers superior mechanical properties compared to standard austenitic grades and is frequently used in aggressive chloride environments. It is supplied as seamless and welded pipe for general corrosive service in the solution-annealed condition.
ASTM A789 UNS S31200 Duplex Stainless Steel Pipe Chemical Composition
The chemical composition limits for UNS S31200 as specified in ASTM A789 ensure a balanced duplex microstructure. Key alloying elements:
- High chromium (24–26%) for corrosion resistance
- Nickel (5.5–6.5%) to stabilize austenite
- Molybdenum (1.2–2.0%) to improve pitting resistance
- Nitrogen (0.14–0.20%) to enhance strength and corrosion resistance
| Chemical Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | 0.03 max | Max limit |
| Manganese (Mn) | 2.00 max | Max limit |
| Phosphorus (P) | 0.030 max | Max limit |
| Sulfur (S) | 0.030 max | Max limit |
| Silicon (Si) | 1.00 max | Max limit |
| Chromium (Cr) | 24.0 – 26.0 | Typical aim 25% |
| Nickel (Ni) | 5.5 – 6.5 | Austenite former |
| Molybdenum (Mo) | 1.20 – 2.00 | Pitting resistance |
| Nitrogen (N) | 0.14 – 0.20 | Interstitial strengthening |
ASTM A789 UNS S31200 Duplex Stainless Steel Pipe Thermal and Electrical Physical Properties
Physical properties of UNS S31200 duplex stainless steel are typical values from published data for similar duplex grades; ASTM A789 does not specify these. Characteristics:
- Density similar to carbon steel
- Lower thermal expansion than austenitic stainless steels
- Higher thermal conductivity than austenitic grades
| Property | Typical Value | Unit | Test Condition / Temperature |
|---|---|---|---|
| Density (ρ) | 7.80 | g/cm³ | At 20°C |
| Modulus of Elasticity (E) | 200 | GPa | At 20°C |
| Shear Modulus (G) | 77 | GPa | At 20°C |
| Poisson's Ratio (ν) | 0.30 | — | At 20°C |
| Thermal Expansion Coefficient (α) | 13.0 / 13.5 / 14.0 | 10⁻⁶/K | 20–100°C / 20–200°C / 20–300°C |
| Thermal Conductivity (λ) | 15.0 / 17.0 / 19.0 / 21.0 | W/(m·K) | 20°C / 100°C / 200°C / 300°C |
| Specific Heat Capacity | 500 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρ_e) | 0.80 | μΩ·m | At 20°C |
ASTM A789 UNS S31200 Duplex Stainless Steel Pipe Mechanical and Physical Properties
Minimum tensile properties required by ASTM A789 for UNS S31200 pipe at room temperature in the solution-annealed condition. Note: Actual values are typically higher; typical yield strengths of 550 MPa are common. Hardness may be specified by agreement.
| Property | Standard Requirement Value | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | 690 min | MPa | Room temperature, longitudinal |
| Yield Strength (ReH), 0.2% offset | 485 min | MPa | Room temperature, longitudinal |
| Elongation (A), 50 mm (2 in.) | 25 min | % | Room temperature |
| Hardness | 290 max (HBW) | HBW | Or equivalent Rockwell scale |
ASTM A789 UNS S31200 Duplex Stainless Steel Pipe Full Equivalent Material Standards and Directly Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| United States | ASTM A789/A789M | UNS S31200 | Primary standard grade; no identical international equivalent exists |
ASTM A789 UNS S31200 Duplex Stainless Steel Pipe Application Introduction
UNS S31200 pipes are selected for demanding corrosive environments where high mechanical strength, good weldability, and resistance to stress corrosion cracking, pitting, and crevice corrosion are essential. Typical usage includes:
Product Applications: Seamless and welded pipe (ASTM A789), Heat exchanger tubes, Process piping for acids and chlorides, Subsea umbilicals and flowlines, Structural piping in corrosive atmospheres
Processed into products: Pipe fittings (elbows, tees, reducers), Flanges and gaskets, Valve bodies and stems, Pump shafts and impellers, Welded assemblies, Instrumentation tubing
Application industries: Chemical processing equipment (reactors, storage tanks), Oil and gas production (flowlines, gathering lines), Marine and offshore platforms, Pulp and paper digesters and bleaching equipment, Desalination plants (reverse osmosis piping), Heat exchangers and condensers, Pressure vessels for corrosive media
ASTM A789 UNS S31200 Duplex Stainless Steel Pipe Similar/Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A789 | UNS S31803 | Leaner duplex (22Cr-5Ni-3Mo) with lower strength but widely available |
| USA | ASTM A789 | UNS S32205 | Improved 2205 duplex; higher N gives similar strength but higher Mo (3.1%) – more corrosion resistant |
| USA | ASTM A789 | UNS S32750 | Super duplex 2507 (25Cr-7Ni-4Mo) – superior pitting resistance and strength |
| USA | ASTM A789 | UNS S32550 | Ferralium 255 with 3.5% Mo and Cu – higher corrosion resistance |
| Europe | EN 10216-5 | 1.4462 (X2CrNiMoN22-5-3) | European duplex 2205, not identical to S31200 but often used in similar applications |
Notes:
For welding, low heat input (0.5–2.5 kJ/mm) and matching filler metal (e.g., ER2594 or ER2209) are recommended. Post-weld heat treatment is not normally required. ASTM A789 requires either a hydrostatic or nondestructive electric test per lot. For sour service per NACE MR0175, hardness in the weld HAZ should not exceed 32 HRC.
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