Project Description
UNS S40900 (409 / SUH409 / X6CrTi12) Stainless Steel Seamless Tube
UNS S40900, commonly known as 409 stainless steel, is a titanium-stabilized ferritic stainless steel widely used for seamless and welded tubular products. Also designated as JIS SUH409 and DIN/EN X6CrTi12 (1.4512), this grade combines approximately 11% chromium with a controlled titanium addition that stabilizes the microstructure, prevents sensitization during welding, and ensures reliable intergranular corrosion resistance throughout the service life of the tube.
At Fushun Steel Tube, we manufacture S40900 seamless stainless steel tubes using an integrated steelmaking and pipe-forming process—from EAF + LF + VD refining through hot-rolled piercing and cold-drawing for precision dimensions. The result is a tube that delivers the oxidation resistance and thermal stability automotive and industrial buyers demand, at a cost point significantly below austenitic grades like 304. Whether you need standard-sized tube from ready stock or a custom run to your exact specifications, contact us for a free quote today.
409 Stainless Steel Seamless Tube — Product View
Shown below is a representative lot of 409 (UNS S40900) ferritic stainless steel seamless tubes in the pickled-and-passivated surface finish, ready for inspection and shipping from our facility. These tubes are manufactured to ASTM A268 and equivalent international standards, with NDT, hydrostatic testing, and dimensional verification completed before release.
Applications of 409 Stainless Steel Seamless Tube
The combination of moderate high-temperature oxidation resistance, good weldability, and cost efficiency makes S40900 the industry-standard material for automotive exhaust systems and a reliable choice for a broad range of industrial tubular applications:
- Automotive exhaust manifolds — Withstands cyclic thermal loading and exhaust gas corrosion at temperatures up to 675°C, far outperforming aluminized carbon steel.
- Catalytic converter shells and internal supports — Titanium stabilization prevents chromium carbide precipitation in weld zones, eliminating sensitization and intergranular attack at operating temperature.
- Muffler and silencer tubing — Readily formed and welded for complex exhaust system geometries; the naturally forming oxide layer provides sufficient corrosion protection in condensed exhaust environments.
- EGR cooler tubes — Used where moderate thermal conductivity and resistance to exhaust gas condensate are needed.
- Heat exchanger tubes — Suitable for moderate-temperature service in chemical processing, food equipment, and power generation where chloride levels are controlled.
- Industrial piping for mildly corrosive fluids — Handles organic acids, dilute sulfuric acid, and alkaline solutions at ambient to moderately elevated temperatures.
- Steam condenser tubing — Reliable performance in fresh water and low-chloride cooling water environments.
- Food processing equipment components — Accepted for applications not requiring the full corrosion resistance of Type 304, such as dry food handling and packaging machinery.
Have a specific application not listed here? Tell us your specifications and our engineering team will confirm suitability and recommend the optimal manufacturing route for your requirements.
Specifications & Standards
S40900 / 409 stainless steel is covered by multiple international standards for both seamless and welded tubular products. The table below summarizes the key standards applicable to this grade in tube form. Fushun Steel Tube manufactures to any of these standards depending on your market and certification requirements.
| Standard | Title / Scope | Tube Type | Grade Designation |
|---|---|---|---|
| ASTM A268/A268M | Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service | Seamless & Welded | TP409 / S40900 |
| ASTM A213/A213M | Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes | Seamless | TP409 |
| EN 10216-5 | Seamless Steel Tubes for Pressure Purposes — Stainless Steel Tubes | Seamless | X6CrTi12 / 1.4512 |
| EN 10297-2 | Seamless Circular Steel Tubes for Mechanical and General Engineering Purposes — Stainless Steel | Seamless | X6CrTi12 / 1.4512 |
| JIS G3463 | Stainless Steel Boiler and Heat Exchanger Tubes | Seamless & Welded | SUH409 / SUS409 |
| JIS G3459 | Stainless Steel Pipes | Seamless & Welded | SUS409 / SUH409 |
| JIS G4312 | Heat-Resisting Steel Plate, Sheet and Strip | — | SUH409 |
We also produce 409 tube to ASTM A519, EN 10305 (precision applications), and customer-specific proprietary specifications. All tubes are supplied with EN 10204 3.1 certificates as standard; EN 10204 3.2 with third-party inspection is available on request. For a complete discussion of your specification requirements, contact us for a free quote.
Available Sizes & Delivery
Fushun Steel Tube offers S40900 seamless tubes across a wide dimensional range through multiple manufacturing routes. Each route is selected to optimize tube quality and cost for the target application.
| Manufacturing Route | OD Range (mm) | Wall Thickness (mm) | Length (m) |
|---|---|---|---|
| Hot-Rolled Seamless | 32–426 | 2.5–40 | Up to 12 (random or fixed) |
| Cold-Drawn Seamless | 6–219 | 0.8–25 | Up to 12 (random or fixed) |
| Cold-Rolled Seamless | 6–114 | 0.5–12 | Up to 12 (random or fixed) |
Ready stock of common S40900 tube sizes is maintained for quick dispatch. For non-standard dimensions or custom chemistries, the minimum order quantity is typically 2–3 tons with a delivery lead time of approximately 25–35 days. Small trial orders are accepted for initial evaluation of special grades or processing routes. Volume orders benefit from negotiable pricing and production scheduling.
Chemical Composition
The chemical composition of S40900 / SUH409 / X6CrTi12 is tightly controlled to ensure consistent ferritic microstructure, weldability, and corrosion resistance across all production lots. The table below compares the composition ranges under the three principal international standards.
| Element | ASTM A240 S40900 | JIS G4312 SUH409 | EN 10088-2 X6CrTi12 / 1.4512 |
|---|---|---|---|
| Carbon (C) | ≤ 0.08% | ≤ 0.08% | ≤ 0.08% |
| Manganese (Mn) | ≤ 1.00% | ≤ 1.00% | ≤ 1.00% |
| Silicon (Si) | ≤ 1.00% | ≤ 1.00% | ≤ 1.00% |
| Phosphorus (P) | ≤ 0.045% | ≤ 0.040% | ≤ 0.040% |
| Sulfur (S) | ≤ 0.030% | ≤ 0.030% | ≤ 0.015% |
| Chromium (Cr) | 10.50–11.75% | 10.50–11.75% | 10.50–12.50% |
| Nickel (Ni) | ≤ 0.50% | ≤ 0.60% | ≤ 0.50% |
| Titanium (Ti) | 6×(C+N) min, 0.75% max | 6×C min, 0.75% max | 6×(C+N) min, 0.65% max |
The titanium-to-carbon ratio is the defining metallurgical feature of this grade. By maintaining a minimum Ti content of six times the total carbon-plus-nitrogen content, all free carbon is tied up as stable titanium carbides and carbonitrides. This leaves chromium uniformly distributed in the ferrite matrix, available for oxidation and corrosion resistance, and prevents chromium carbide precipitation at grain boundaries during welding or elevated-temperature service.
Manufacturing Process
Fushun Steel Tube employs an integrated manufacturing route for S40900 seamless tube production, controlling quality from molten steel to finished product:
- Steelmaking: Scrap and ferroalloys are melted in an Electric Arc Furnace (EAF), refined in a Ladle Furnace (LF) for precise composition and temperature control, then processed through Vacuum Degassing (VD) to reduce dissolved gases (hydrogen, nitrogen, oxygen). For demanding applications, Electroslag Remelting (ESR) or VIM + VAR routes are available to achieve superior cleanliness.
- Billet Casting & Conditioning: Continuously cast round billets are inspected, surface-conditioned, and cut to length for pipe mill charging.
- Hot Piercing & Rolling: Billets are heated to 1150–1250°C and rotary-pierced into hollow shells, which are then elongated and sized on a pilger mill or plug mill to the target hot-rolled dimensions.
- Cold Drawing / Cold Rolling: For precision tube requirements, hot-rolled hollows are cold-drawn through dies or cold-rolled on pilger mills to achieve tight OD and WT tolerances, improved surface finish, and enhanced mechanical properties.
- Heat Treatment: All tubes are annealed at 780–850°C followed by controlled cooling to restore the fully recrystallized ferritic microstructure and relieve cold-working stresses.
- Finishing: Tubes are straightened, cut to ordered lengths, end-finished (plain, beveled, or threaded), and surface-treated (pickled, passivated, or bright-annealed) per customer specification.
Mechanical Properties
Mechanical properties of S40900 seamless tube in the annealed condition, as specified by the principal tube standards:
| Property | ASTM A268 TP409 | JIS G3463 SUH409 | EN 10216-5 1.4512 |
|---|---|---|---|
| Tensile Strength, min | 380 MPa (55 ksi) | 360 MPa (52 ksi) | 390–560 MPa |
| Yield Strength (0.2%), min | 170 MPa (25 ksi) | 175 MPa (25 ksi) | 200 MPa (29 ksi) |
| Elongation in 50 mm, min | 20% | 22% | 20% |
| Hardness, max | 88 HRB | 80 HRB / 162 HBW | 180 HB |
| Density | 7.75 g/cm³ (0.280 lb/in³) | ||
| Melting Range | 1480–1530°C (2696–2786°F) | ||
| Modulus of Elasticity | 200 GPa (29 × 10⁶ psi) at 20°C | ||
| Thermal Conductivity | 25 W/m·K at 20°C | ||
| Mean Thermal Expansion (20–500°C) | 11.5 × 10⁻⁶ /K | ||
Actual as-delivered properties depend on the tube manufacturing route and final heat treatment condition. Cold-drawn tubes exhibit higher strength and hardness in the as-drawn condition; full annealing restores the properties listed above. For applications requiring specific strength, elongation, or hardness targets, contact us for a free quote with your property requirements.
Heat Treatment
As a ferritic stainless steel, S40900 cannot be hardened by martensitic transformation. All strengthening is achieved through cold working; heat treatment serves to soften, stress-relieve, and restore the equilibrium microstructure:
| Treatment Type | Temperature Range | Holding Time | Cooling Method | Purpose |
|---|---|---|---|---|
| Full Annealing | 780–850°C (1436–1562°F) | 30–90 min (depending on section) | Air cool or water quench | Recrystallize cold-worked structure; restore ductility and formability |
| Stress Relieving | 650–760°C (1202–1400°F) | 60–120 min | Air cool | Relieve residual stresses from forming or welding without grain growth |
Important: Avoid prolonged exposure above 900°C, as excessive grain growth in ferritic stainless steels can occur, leading to embrittlement and reduced toughness. For post-weld heat treatment, the stress-relieving range is recommended. Our in-house heat treatment furnaces are instrumented and calibrated to maintain temperature uniformity within ±10°C, ensuring consistent properties across every tube in the lot.
Surface Finish & Tolerances
409 stainless steel seamless tubes are available in the following surface finish and tolerance options:
Surface Finishes
- Hot-Rolled & Pickled
- Standard finish for hot-rolled seamless tubes. The dark oxide scale from hot forming is removed by acid pickling and passivation, leaving a matte gray surface suitable for most industrial applications.
- Bright Annealed (Cold-Drawn/Cold-Rolled)
- Cold-worked tubes annealed in a controlled-atmosphere (hydrogen or dissociated ammonia) furnace, producing a bright, oxide-free surface. Preferred for precision applications, stainless steel tube requiring clean internal surfaces, and applications where post-fabrication cleaning must be minimized.
- Polished
- Mechanical polishing to 180#, 320#, 400#, or 600# grit finish is available on the OD surface for architectural, food equipment, or aesthetic requirements.
- Shot Blasted
- Optional pre-treatment for hot-rolled tubes to remove heavy scale ahead of pickling or coating.
Dimensional Tolerances
Standard tolerances follow the applicable ASTM, EN, or JIS specification selected. For cold-drawn precision tubes manufactured to cold-drawn steel tube tolerances, OD can be held to ±0.10 mm and WT to ±10% of nominal. Tighter tolerances are achievable for specific requirements—please specify at inquiry.
Quality Assurance & Testing
Every lot of 409 stainless steel seamless tube undergoes a comprehensive quality control program from incoming raw material through finished product certification:
- Raw Material Verification: Incoming billets are verified by optical emission spectrometry (OES) for full chemical composition, tagged with heat number, and traceable through every production step.
- In-Process Inspection: Hot-rolling and cold-drawing parameters (temperature, reduction ratios, speeds) are monitored in real time. Dimensional checks are performed at each process stage.
- Non-Destructive Testing (NDT): 100% of tubes receive either eddy current testing (ET) or ultrasonic testing (UT) per the applicable standard (ASTM E426, EN 10246-1, or ISO 10893-1/2).
- Hydrostatic Pressure Testing: Performed to specification requirements, typically at 1.5× design pressure with prescribed hold times. Alternative pneumatic or underwater air testing is also available.
- Mechanical Testing: Tensile tests (room temperature and/or elevated temperature per customer requirements), hardness tests, and flattening/flaring tests on sample coupons from each heat treatment lot.
- Metallographic Examination: Microstructure verification for ferritic grain size, absence of martensite, and titanium carbide distribution. Intergranular corrosion testing (ASTM A763 Practice X or equivalent) is available on request.
- Dimensional & Visual Final Inspection: 100% dimensional check on OD, WT, length, straightness, and end condition plus visual surface inspection before packing.
Our quality management system is ISO 9001 certified. All test results are documented in the EN 10204 3.1 inspection certificate supplied with every shipment. For critical applications requiring independent verification, EN 10204 3.2 certificates with third-party inspection by SGS, BV, LR, or your nominated agency are available.
Packing & Shipping
S40900 stainless steel seamless tubes are packed to prevent mechanical damage, corrosion, and contamination during transit and storage:
- Cold-drawn precision tubes: Individual tubes wrapped in anti-rust paper, bundled with steel straps, and packed in seaworthy plywood cases with end protectors.
- Hot-rolled tubes: Bare bundles secured with steel straps, with plastic end caps on beveled or threaded ends. For export orders, bundles are wrapped in water-resistant fabric.
- Small-diameter tubes (OD ≤ 25 mm): Packed in wooden crates with separators to prevent surface contact and fretting during transit.
Shipping is available by sea freight (FCL / LCL), air freight (urgent / small-volume orders), rail, or express courier. Standard shipping marks include heat number, specification, dimensions, and bundle weight. Custom labeling and bar-coding for inventory integration is available for volume buyers. Our logistics team coordinates shipping to all major ports worldwide, including documentation support for customs clearance.
Frequently Asked Questions
- What sizes of 409 stainless steel seamless tube do you supply?
- We supply stainless steel seamless tube in grade 409 in OD 6–426 mm with wall thickness 0.8–40 mm, in lengths up to 12 m. Hot-rolled, cold-drawn, and cold-rolled routes are all available. Custom dimensions outside standard ranges can be produced — MOQ is typically 2–3 tons.
- What is the maximum service temperature for 409 stainless steel tube?
- 409 stainless steel provides reliable oxidation resistance up to 675°C (1250°F) in intermittent service and approximately 815°C (1500°F) in continuous service. Above these temperatures, scaling rates increase and mechanical strength declines. For sustained exposure above 750°C, consider a higher-chromium ferritic grade or an austenitic stainless steel.
- Can 409 tubing be welded? Does it require post-weld heat treatment?
- Yes, 409 is designed for weldability. The titanium stabilization prevents chromium carbide precipitation in the heat-affected zone, so it generally does not require post-weld solution annealing for most applications. Standard TIG, MIG, and resistance welding processes work well. A 409Cb or 309L filler metal is recommended for fusion welding. Stress relieving at 650–760°C may be applied after heavy forming or welding if dimensional stability or residual stress reduction is required.
- How does 409 compare to 304 stainless steel in terms of cost and performance?
- 409 contains approximately 11% chromium with no nickel (or trace nickel only), while 304 contains 18% chromium and 8% nickel. The absence of nickel gives 409 a significant raw-material cost advantage — typically 30–40% lower than 304. In automotive exhaust environments, 409 actually outperforms 304 in thermal fatigue resistance due to its lower thermal expansion coefficient. However, 304 offers superior general corrosion resistance, especially in chloride-containing environments. For boiler tube applications requiring broad chemical resistance, select 304 or 316; for exhaust and moderate-temperature applications, 409 delivers the best value.
- What certifications and documentation do you provide?
- Every shipment includes an EN 10204 3.1 mill test certificate documenting chemical composition, mechanical properties, NDT results, hydrostatic test results, and dimensional verification for the specific heat and lot. EN 10204 3.2 certificates with third-party witness inspection are available on request. Our facility is ISO 9001 certified, and we can support customer-specific quality documentation packages including PPAP, FAI, and material traceability reports.