What Is a Seamless 254SMO/31254 Stainless Steel Tube?
1. What is a Seamless 254SMO Stainless Steel Tube?
254SMO UNS S31254 Seamless Stainless Steel Tube is supplied for 6Mo super-austenitic chemistry for high pitting and crevice-corrosion resistance. The size range shown (OD 6–257 mm; WT 0.5–35 mm) is the overall capability across this product family, not a per-grade commitment. Confirm the specific OD × WT × length combination for the ordered grade in the quotation. The governing specification must be stated on the purchase order: Confirm ASTM A269/A213 applicability and UNS S31254 against the purchase order. Chemistry, mechanical properties, heat treatment, dimensional tolerance, NDT and certification must be reported against the ordered standard and material heat; do not treat typical values as guaranteed acceptance limits.
Manufactured from a solid billet using a seamless hot-piercing and cold-finishing process, 254SMO tube provides:
- No longitudinal weld seam, reducing weld-related corrosion risk
- Uniform microstructure and consistent corrosion performance
- High pressure integrity for critical heat-transfer and process systems
The grade is characterized by:
- Approximately 20% chromium and 18% nickel
- High molybdenum content of approximately 6%
- Controlled additions of nitrogen and copper
- Very low carbon content (maximum 0.020%)
This balanced composition gives UNS S31254 excellent resistance to pitting, crevice corrosion and chloride-induced stress corrosion cracking while maintaining good weldability and mechanical strength.
2. Key Features & Technical Advantages
Outstanding Pitting and Crevice Corrosion Resistance
The high chromium, molybdenum and nitrogen content provides a typical PREN of at least 42.5, supporting reliable service in seawater and other chloride-bearing media.
Strong Resistance to Chloride Stress Corrosion Cracking
Its high nickel content and super-austenitic structure improve resistance to chloride-induced stress corrosion cracking compared with conventional 300-series stainless steels.
High Mechanical Strength
Nitrogen strengthening gives 254SMO substantially higher strength than standard austenitic stainless steels, supporting demanding pressure and heat-transfer applications.
Resistance to Process Acids
Molybdenum and copper improve performance in sulfuric acid, phosphoric acid and other aggressive chemical environments, subject to concentration and temperature.
Good Weldability and Fabricability
The low carbon content minimizes sensitization and helps retain corrosion resistance in properly controlled welded assemblies.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for Seamless 254SMO/31254 Stainless Steel Tube.
- The specific role of each key element is critical to understanding the alloy’s overall performance:
- Chromium (Cr): At 19.5% to 20.5%, chromium is the primary element responsible for forming the passive oxide layer on the steel’s surface, which provides foundational corrosion resistance.
- Nickel (Ni): With a high content of 17.5% to 18.5%, nickel stabilizes the austenitic crystal structure. This imparts the material with exceptional ductility, toughness, and, most importantly, provides superior resistance to chloride-induced stress corrosion cracking (SCC) compared to standard 300-series grades.
- Molybdenum (Mo): The”super”element, with its high content of 6.0% to 7.0%, is the single most important factor for enhancing pitting and crevice corrosion resistance. This is particularly effective in halide environments, such as those with high concentrations of chlorides.
- Nitrogen (N): The addition of nitrogen (0.18% to 0.25%) serves a dual purpose. It works synergistically with molybdenum to significantly boost pitting resistance, and it also contributes to the material’s high mechanical strength.
- Copper (Cu): The addition of copper (0.50% to 1.00%) improves the alloy’s resistance to sulfuric acid and other non-oxidizing acids.The low carbon content (<0.020%) is also a vital feature, as it minimizes the risk of carbide precipitation during heating, which could otherwise lead to intergranular corrosion, especially in the heat-affected zone of welds.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| S31254 | 254 SMO | 1.4547 | X1CrNiMoCuN20-18-7 | SUS312L | 015Cr20Ni18Mo6CuN |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. Approximate or unconfirmed correspondences retain their qualification. See the grade designation index.
Chemical Composition
| C | Si | Mn | P | S | Cr | Ni | Mo | N | Cu |
|---|---|---|---|---|---|---|---|---|---|
| ≤0.020 | ≤0.80 | ≤1.00 | ≤0.030 | ≤0.010 | 19.50–20.50 | 17.50–18.50 | 6.00–6.50 | 0.180–0.220 | 0.50–1.00 |
Data source: ASTM A213-25 / ASME SA213 Table 1, 254SMO row ≤ heat-analysis acceptance limits. Confirm the values against the ordered edition and the MTC.
- 254SMO stainless steel (UNS S31254 / EN 1.4547) is designed to maintain high strength and reliable corrosion resistance in demanding chloride-rich and acidic environments.
| Tensile Strength | Yield Strength | Elongation | Hardness |
|---|---|---|---|
| ≥ 655 MPa (wall > 5 mm); ≥ 675 MPa (wall ≤ 5 mm) | ≥ 310 MPa | ≥ 35% | ≤ 220 HBW / 230 HV / 96 HRB |
- These physical properties highlight the material’s ability to perform reliably under a wide range of conditions.
| Density | Melting Point | Thermal Expansion | Thermal Conductivity | Modulus of Elasticity | Electrical Resistivity |
|---|---|---|---|---|---|
| 8.0 g/cm³ | 1300 – 1390 °C approx. | 16.5 μm/m·°C (20-100°C) | 13.9 W/m·K (20°C) | 195 GPa | 0.85 × 10⁻⁶ Ω·m (20°C) |
- ASTM A1016/A1016M Tube Size Tolerance Chart
Size Tolerance Chart (mm)
| Specified Outside Diameter (OD) (Inches) | Permissible Variations in OD (± Inches) |
|---|---|
| 1⁄2 to 1 | ±0.005 |
| Over 1 to 1-1⁄2 | ±0.008 |
| Over 1-1⁄2 to 2 | ±0.010 |
| Over 2 to 2-1⁄2 | ±0.012 |
| Over 2-1⁄2 to 3-1⁄2 | ±0.014 |
| Over 3-1⁄2 to 5 | ±0.020 |
Tolerance basis: permitted variations per the governing specification stated on this page and the applicable general-requirements standard (ASTM A1016 / ASME SA1016) for the ordered product form; the wall-thickness and length variations in this section follow the same basis.
| Specified Outside Diameter (OD) (Inches) | Specified Wall Thickness (WT) (Inches) | Permissible Variation (± Inches) |
|---|---|---|
| 1⁄2 to 1 (Inclusive) | 0.025 to 0.065(Inclusive) | ±0.010 |
| Over 0.065to 0.134 (Inclusive) | ±0.012 | |
| Over 1 to 1-1⁄2 (Inclusive) | 0.025 to 0.065 (Inclusive) | ±0.010 |
| Over 0.065 to 0.134 (Inclusive) | ±0.012 | |
| Over 1-1⁄2 to 2 (Inclusive) | 0.025 to 0.049 (Inclusive) | ±0.011 |
| Over 0.049 to 0.083 (Inclusive) | ±0.012 | |
| Over 0.083 to 0.148 (Inclusive) | ±0.014 | |
| Over 2 to 2-1⁄2 (Inclusive) | 0.032 to 0.065 (Inclusive) | ±0.013 |
| Over 0.065 to 0.109 (Inclusive) | ±0.015 | |
| Over 0.109 to 0.165 (Inclusive) | ±0.017 | |
| Over 2-1⁄2 to 3-1⁄2 (Inclusive) | 0.032 to 0.165 (Inclusive) | ±0.020 |
| Over 0.165 to 0.220 (Inclusive) | ±0.025 | |
| Over 3-1⁄2 to 5 (Inclusive) | 0.083 to 0.165 (Inclusive) | ±0.025 |
| Over 0.165 to 0.220 (Inclusive) | ±0.030 |
Length Tolerance
- For Specific Cut Lengths, the standard tolerance is +1⁄8 in. [3 mm], -0 in. [0 mm].
Important Note: The values presented here are based on the dimensional tolerance tables in ASTM A1016/A1016M (General Requirements for Ferritic Alloy Steel, Austenitic Alloy Steel, and Stainless Steel Tubes), contains other essential requirements like straightness and details for tubes with ODs outside of this range. Always consult the latest official standard for design and procurement.
Common Industrial Applications
TP317 seamless stainless steel tubes are widely used in:
Chemical & Acid Processing
- Sulfuric acid production systems
- Phosphoric and acetic acid equipment
- Heat exchangers and reactors
Oil & Gas / Refinery
- Sour gas handling systems
- Gas scrubbing equipment
- Corrosion-resistant piping
Environmental Engineering
- Flue Gas Desulfurization (FGD) systems
- Scrubbers and exhaust treatment systems
Pulp & Paper Industry
- Bleaching systems
- Chemical washing units
Pharmaceutical & Food Industry
- High-purity, corrosion-free process systems
Advanced Manufacturing Process
- Raw Material Selection & Billet Heating
High-quality alloy billets ensure consistent composition and performance. - Hot Piercing & Seamless Forming
Produces hollow tubes with no longitudinal weld seam. - Cold Drawing / Cold Rolling
Achieves precise dimensions and superior surface finish. - Solution Annealing
Restores corrosion resistance and mechanical properties. - Full Non-Destructive Testing (NDT)
- Ultrasonic Testing (UT)
- Eddy Current Testing (ET)
- Hydrostatic Testing
100% Quality Assurance & Certification
We provide full quality control and certification to meet global project requirements:
- EN 10204 3.1 Material Test Certificate (MTC) as standard; EN 10204 3.2 on arrangement
- 100% PMI (Positive Material Identification)
- NDT: UT, ET or Hydrostatic Test, as specified on the order
Frequently Asked Questions
What sizes are available for 254SMO seamless tube?
Which specification governs 254SMO seamless tube?
What inspection documents are provided?
Technical review: page data reviewed by the Xinzhe technical desk on 2026-09-27. Chemistry acceptance limits are compiled from the governing ASTM/ASME specification stated on this page; mechanical and physical values are typical reference data and are not acceptance guarantees. Values must be confirmed against the standard edition in force at order time and the material test certificate.
Ready to Request a Quotation?
Send the size (OD and wall or schedule), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
For the same grade in pipe form, see the 254SMO seamless pipe. To compare other grades and size combinations, browse the Stainless Steel Seamless Pipe category. Minimum order quantity and lead time are confirmed on enquiry against the ordered grade, size and quantity.
