ASTM A240 904L (UNS N08904) Stainless Steel Pipe
ASTM A240 904L (UNS N08904) Stainless Steel Pipe - Premium Austenitic Alloy for Severe Corrosion
Complete material datasheet of 904L (UNS N08904) according to ASTM A240, including chemical, mechanical, thermal properties and international equivalents for pipe applications.
Hot/cold forming, machining, welding (TIG, MIG, SAW, SMAW), solution annealing (1050-1150°C, water quench)
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ASTM A240 904L Stainless Steel Pipe Introduction
ASTM A240 904L (correctly designated as UNS N08904, not N08804) is a high-alloy, low-carbon austenitic stainless steel with additions of molybdenum and copper. It delivers outstanding resistance to pitting and crevice corrosion in warm chloride environments and exhibits excellent performance in sulfuric, phosphoric, and organic acids. Originally developed for sulfuric acid service, 904L is widely used in chemical processing, pollution control, and seawater handling. Compared with conventional 316L/317L, its elevated nickel, chromium, and molybdenum content provides significantly better corrosion resistance. The material is non-magnetic in the solution-annealed condition and offers good formability and weldability using appropriate filler metals (e.g., ERNiCrMo-3). This data sheet provides accurate composition and property values per ASTM A240 and supplementary physical data for engineering design.
ASTM A240 904L Stainless Steel Pipe Chemical Composition
The chemical composition conforms strictly to ASTM A240/A240M for grade UNS N08904. These limits ensure the required combination of austenitic structure and corrosion resistance.
- The very low carbon content (<0.020%) minimizes sensitization during welding.
- High Mo (4.0-5.0%) and Cu (1.0-2.0%) improve resistance to reducing acids like sulfuric and phosphoric acid.
- High Ni (23.0-28.0%) stabilizes austenite and enhances chloride SCC resistance.
| Element | Specified Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.020 | |
| Manganese (Mn) | ≤2.00 | |
| Phosphorus (P) | ≤0.045 | |
| Sulfur (S) | ≤0.035 | |
| Silicon (Si) | ≤1.00 | |
| Chromium (Cr) | 19.0–23.0 | Key for passivity |
| Nickel (Ni) | 23.0–28.0 | Austenite stabilizer |
| Molybdenum (Mo) | 4.0–5.0 | Pitting resistance |
| Copper (Cu) | 1.0–2.0 | Acid resistance enhancement |
| Nitrogen (N) | ≤0.10 |
ASTM A240 904L Stainless Steel Pipe Thermal and Electrical Physical Properties
These physical constants are representative for 904L in the annealed condition and are useful for engineering calculations involving thermal expansion, heat transfer, and magnetic/electrical characteristics.
- Values are measured at the indicated temperature unless noted otherwise.
- The alloy is non-magnetic (relative permeability < 1.02) when annealed.
| Property | Typical Value | Unit | Temperature / Condition |
|---|---|---|---|
| Density (ρ) | 7.95 | kg/dm³ (g/cm³) | 20 °C |
| Modulus of Elasticity (E) | 200 | GPa | 20 °C |
| Shear Modulus (G) | 77 | GPa | 20 °C |
| Poisson's Ratio (ν) | 0.30 | 20 °C | |
| Thermal Expansion Coefficient (α) | 14.9 | 10⁻⁶·K⁻¹ (µm/m·°C) | 20–100 °C |
| Thermal Expansion Coefficient (α) | 15.8 | 10⁻⁶·K⁻¹ | 20–200 °C |
| Thermal Expansion Coefficient (α) | 16.7 | 10⁻⁶·K⁻¹ | 20–400 °C |
| Thermal Expansion Coefficient (α) | 17.5 | 10⁻⁶·K⁻¹ | 20–500 °C |
| Thermal Conductivity (λ) | 12.9 | W/(m·K) | 20 °C |
| Thermal Conductivity (λ) | 14.6 | W/(m·K) | 100 °C |
| Thermal Conductivity (λ) | 18.0 | W/(m·K) | 300 °C |
| Thermal Conductivity (λ) | 20.5 | W/(m·K) | 500 °C |
| Specific Heat Capacity (cp) | 500 | J/(kg·K) | 20 °C |
| Electrical Resistivity (ρe) | 0.95 | µΩ·m | 20 °C |
ASTM A240 904L Stainless Steel Pipe Mechanical Properties
The following tensile properties are minimum requirements at room temperature for plate, sheet, and strip in the solution-annealed condition. Pipe manufactured to ASTM A312 904L typically meets or exceeds these values.
- Elongation is measured in 50 mm (2 in.) gauge length for standard specimens.
- Hardness values are not mandatory in A240 but are commonly specified for reference.
| Property | Minimum/Maximum Value | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | ≥490 | MPa | Room temperature, solution annealed |
| Yield Strength (ReH, 0.2% offset) | ≥220 | MPa | Room temperature, solution annealed |
| Elongation (A) | ≥35 | % | Gauge length 50 mm (2 in.) |
| Hardness, Rockwell B | ≤90 | HRBW | Typical, for reference |
| Hardness, Brinell | ≤200 | HBW | Typical, for reference |
ASTM A240 904L Stainless Steel Pipe Fully Equivalent International Standards and Replaceable Grades
| Country/Region | Standard | Grade Designation | Remarks |
|---|---|---|---|
| USA | ASTM A240, A312, A182 | UNS N08904 / 904L | Original specification |
| European Union | EN 10028-7, EN 10216-5 | 1.4539 (X1NiCrMoCu25-20-5) | Identical chemical limits |
| Japan | JIS G4304, G3459 | SUS 904L | |
| China | GB/T 4237, GB/T 20878 | 015Cr21Ni26Mo5Cu2 (formerly 00Cr20Ni25Mo4.5Cu) | |
| International | ISO 15510 | X1NiCrMoCu25-20-5 | Corresponds to EN 1.4539 |
ASTM A240 904L Stainless Steel Pipe Application Introduction
904L is primarily selected for its exceptional resistance to reducing acids and chloride-induced pitting/crevice corrosion. It is widely used where 316L and 317L would suffer accelerated attack.
- Key environments: sulfuric acid at moderate concentrations and temperatures, phosphoric acid production, seawater and brackish water, organic acids, and chemical process streams.
- Limitations: Not recommended for hot, concentrated chlorides where high-nickel alloys (e.g., C-276) are required; susceptible to stress corrosion cracking above 60°C in magnesium/sodium chloride brines under high stress.
Product Applications: Seamless and welded pipe for corrosive fluid transport, Plate and sheet for pressure vessels, storage tanks, and reactors, Heat exchanger tubes and tube sheets, Fittings, flanges, and valves, Wire for welding consumables and screens
Processed into products: Sulfuric acid coolers and piping, Phosphoric acid evaporator tubes, Seawater intake pipe and condenser tubes, Scrubber internals and mist eliminators, Reaction vessels for organic acid synthesis, Bleach washer drums in pulp mills, Flexible metal hoses and expansion joints
Application industries: Chemical processing (sulfuric acid, phosphoric acid, acetic acid plants), Oil refining and petrochemical, Seawater and brackish water handling (cooling water pipe, desalination), Pollution control (FGD scrubbers, ducting, stacks), Pulp and paper (bleach plants, chemical recovery), Pharmaceutical and food processing (hygienic tubing, heat exchangers), Mining and hydrometallurgy
ASTM A240 904L Stainless Steel Pipe Similar / Alternative Super-Austenitic and High-Alloy Stainless Steels
| Country/Region | Standard | Grade Designation | Remarks |
|---|---|---|---|
| USA | ASTM A240 | UNS S31254 (254 SMO®) | Higher Mo (6.0-6.5%) and N; better pitting resistance but lower Cu |
| USA | ASTM A240 | UNS N08367 (AL-6XN®) | Ni 23.5-25.5, Mo 6.0-7.0, N 0.18-0.25; superior in chloride media |
| USA | ASTM A240 | UNS N08926 (1925hMo) | Mo 6.0-7.0, Ni 24-26, similar corrosion class |
| European | EN 10028-7 | 1.4529 (X1NiCrMoCuN25-20-7) | High Mo and N, often used as an upgrade to 904L |
| USA | ASTM B625 | UNS N08020 (Alloy 20) | Ni 32-38, Cr 19-21, Mo 2-3, Cu 3-4; excellent in sulfuric acid but less versatile for chlorides |
Notes:
Nomenclature note: The grade is universally known as 904L and has UNS number N08904. The designation N08804 is incorrect and corresponds to Incoloy® 800. Always use UNS N08904 when specifying 904L to ASTM A240.
Welding: Use over-alloyed fillers such as ERNiCrMo-3 (Alloy 625) or ERNiCrMo-4 (C-276) to maintain pitting resistance. Solution anneal after heavy forming or welding.
Surface condition: Bright annealed or pickled pipe is typical to ensure optimum corrosion resistance.
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