Project Description
444 (UNS S44400 / SUS444 / 1.4521) Stainless Steel Seamless Tube
Grade 444 is a low-carbon, molybdenum- and titanium-stabilized ferritic stainless steel that delivers exceptional resistance to SCC in chloride-containing environments — a failure mode that conventional stainless steel tubes in the 300-series austenitic family cannot reliably withstand. With a PREN of approximately 25, 444 matches the pitting resistance of 316L while eliminating the risk of chloride SCC entirely.
Known under multiple international designations — UNS S44400 in the ASTM system, SUS444 per JIS, and 1.4521 / X2CrMoTi18-2 per EN — this grade is engineered for applications where hot water, steam, and mildly acidic chloride media make traditional stainless grades unreliable. The titanium stabilization locks carbon and nitrogen into stable carbides and nitrides, preventing intergranular corrosion after welding without the need for post-weld heat treatment.
Fushun Steel Tube produces 444 seamless tubes through a controlled melting and hot-working route, backed by EAF + LF + VD steelmaking with optional ESR refinement for the most demanding applications. Every heat is traceable to its mill certificate. Contact us for a free quote with your OD, wall thickness, and length requirements.
Applications
Thanks to its immunity to chloride SCC and competitive cost profile, 444 stainless steel seamless tube is the preferred material for the following product-level applications:
- Solar water heater absorber tubes and header pipes
- Hot water storage tank heat exchanger coils
- Condenser and evaporator tubes in desalination plants
- Shell-and-tube heat exchangers for chemical processing
- Brewery wort coolers and dairy pasteurizer tubes
- Food-grade processing lines for acidic products (fruit juices, vinegar)
- Automotive exhaust manifold and catalytic converter tubing
- Boiler and superheater tubes in moderate-temperature service
- Geothermal heat pump ground-loop heat exchangers
Tell us your specifications and our engineers will recommend the optimal grade and size for your application.
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Specifications & Standards
Grade 444 seamless tubes are manufactured and supplied in compliance with the following international standards. Fushun Steel Tube also accommodates customer-specific technical specifications and supplementary requirements.
ASTM / ASME Standards
- ASTM A268/A268M — Standard Specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service
- ASTM A213/A213M — Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes
European (EN) Standards
- EN 10216-5 — EN 10216-5 Seamless steel tubes for pressure purposes — Stainless steel tubes (grade 1.4521)
- EN 10297-2 — EN 10297-2 Seamless circular steel tubes for mechanical and general engineering purposes — Stainless steel (grade 1.4521)
- EN 10305-4 — EN 10305-4 Steel tubes for precision applications — Seamless cold-drawn tubes for hydraulic and pneumatic power systems
Japanese (JIS) Standards
- JIS G3463 — Stainless steel boiler and heat exchanger tubes (grade SUS444)
Available Sizes & Delivery
Fushun Steel Tube supplies 444 stainless steel seamless tubes in an extensive dimensional range covering both hot-rolled and cold-drawn/cold-rolled production routes. Our manufacturing capabilities allow us to meet tight tolerances for precision applications.
| Production Route | OD Range | WT Range | Length |
|---|---|---|---|
| Hot-Rolled Seamless | 25 mm – 325 mm (0.984 in – 12.8 in) | 2.5 mm – 30 mm (0.098 in – 1.18 in) | Up to 12 m |
| Cold-Drawn / Cold-Rolled Seamless | 6 mm – 120 mm (0.236 in – 4.72 in) | 0.5 mm – 12 mm (0.020 in – 0.472 in) | Up to 12 m (coil for small OD) |
| Precision Cold-Drawn | 6 mm – 80 mm (0.236 in – 3.15 in) | 0.5 mm – 8 mm (0.020 in – 0.315 in) | Fixed lengths or cut-to-length |
Delivery Information
- Ready stock (common sizes): Approximately 7 days
- Custom / non-standard specifications: MOQ 2–3 tons, approximately 25–35 days
- Trial orders: Small trial orders accepted for special grades and first-time qualification
- Volume orders: Negotiable pricing and delivery scheduling
Request a sample or trial quantity to qualify our material for your production line.
Chemical Composition
The chemical composition of 444 stainless steel is tightly controlled to achieve its characteristic ferritic microstructure and the Ti-stabilization that prevents intergranular corrosion. The table below compares the requirements under ASTM and EN standards.
| Element | ASTM A268 (UNS S44400) | EN 10216-5 (1.4521) |
|---|---|---|
| Carbon (C) | ≤ 0.025 | ≤ 0.025 |
| Manganese (Mn) | ≤ 1.00 | ≤ 1.00 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.040 | ≤ 0.040 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.015 |
| Chromium (Cr) | 17.50 – 19.50 | 17.00 – 20.00 |
| Nickel (Ni) | ≤ 1.00 | ≤ 1.00 |
| Molybdenum (Mo) | 1.75 – 2.50 | 1.80 – 2.50 |
| Nitrogen (N) | ≤ 0.035 | ≤ 0.030 |
| Titanium (Ti) | Ti+Nb: 0.20+4×(C+N) min, 0.80 max | 4×(C+N)+0.15 to 0.80 |
The key to 444's performance is the combined addition of approximately 2% molybdenum and titanium stabilization. Molybdenum significantly elevates resistance to pitting and crevice corrosion in chloride-bearing solutions, while titanium preferentially combines with carbon and nitrogen, preventing chromium depletion at grain boundaries during welding and high-temperature service.
Manufacturing Process
Fushun Steel Tube's manufacturing route for 444 seamless tubes begins with EAF melting of carefully selected raw materials, followed by LF refining and VD treatment to achieve ultra-low carbon and nitrogen levels — essential for maximizing titanium stabilization efficiency. For critical applications, ESR or VIM+VAR routes are available to produce exceptionally clean steel with minimized inclusion content.
The ingot or continuously cast billet is heated and hot-pierced on a modern mandrel mill to produce the hollow shell. For cold-drawn and cold-rolled precision tubes, the hot-rolled mother tube undergoes multiple cold reduction passes with intermediate annealing at 900–1050 °C, followed by bright annealing in a protective atmosphere for a clean, scale-free surface. The final tube is straightened, cut to length, and subjected to comprehensive non-destructive testing. Cold-drawn precision tubes and cold-rolled precision tubes are available with enhanced dimensional accuracy and surface finish.
Mechanical Properties
The mechanical properties below represent the minimum guaranteed values for 444 stainless steel seamless tube in the annealed condition. Cold-worked tempers are available for applications requiring higher strength.
| Property | ASTM A268 (S44400) | EN 10216-5 (1.4521) |
|---|---|---|
| Tensile Strength, Rm | ≥ 415 MPa (60 ksi) | 420 – 640 MPa |
| Yield Strength, Rp0.2 | ≥ 275 MPa (40 ksi) | ≥ 300 MPa |
| Elongation, A | ≥ 20% (in 2 in.) | ≥ 20% (longitudinal) |
| Hardness | ≤ 90 HRB | ≤ 217 HB |
| Modulus of Elasticity | ~200 GPa (29 × 10⁶ psi) | |
| Density | ~7.70 g/cm³ (0.278 lb/in³) | |
As a ferritic stainless steel, 444 is not hardenable by heat treatment. Strength can be increased through cold working, but this is typically not required given the grade's as-annealed properties already exceed those of many standard austenitic grades. The higher yield strength compared to 304/304L makes 444 an attractive option where thinner walls and reduced material weight are design objectives.
Heat Treatment
| Treatment Type | Temperature | Holding Time | Cooling Method |
|---|---|---|---|
| Annealing (Solution) | 900 – 1050 °C (1650 – 1925 °F) | Per section thickness (typically 1 min/mm) | Air cool or water quench |
| Bright Annealing | 950 – 1050 °C (1740 – 1925 °F) | Per section thickness | Rapid cool in protective atmosphere (H₂/N₂) |
| Stress Relieving | 200 – 300 °C (390 – 570 °F) | 1 – 2 hours | Air cool |
Annealing is the standard delivery condition for 444 seamless tubes. The annealing temperature range is broad enough to accommodate different section sizes while ensuring full recrystallization of the ferritic structure. Unlike martensitic grades, 444 does not undergo phase transformation during cooling; rapid cooling from the annealing temperature is recommended primarily to prevent the precipitation of undesirable phases such as sigma or chi at intermediate temperatures (typically 500–900 °C). Bright annealing in a controlled atmosphere yields a clean, oxide-free surface ideal for applications where internal cleanliness is critical. Stress relieving at low temperature may be applied after cold forming without degrading corrosion resistance.
Surface Finish & Tolerances
Fushun Steel Tube supplies 444 seamless tubes in a range of surface conditions to match downstream fabrication and end-use requirements. The standard hot-rolled finish is pickled and passivated to remove mill scale and restore the passive chromium oxide layer. For precision applications, cold-drawn and cold-rolled tubes are available with bright annealed or polished surfaces.
- Hot-rolled + pickled: Matte gray finish, suitable for general industrial service
- Cold-drawn + bright annealed: Smooth, bright metallic surface, ideal for heat exchanger and food-contact applications
- Cold-rolled + polished: Ra ≤ 0.8 µm, available for hygienic and pharmaceutical tubing
- Honed / skived: ID finishing for hydraulic cylinder and precision mechanical applications
Dimensional tolerances follow the applicable product standard: ASTM A268 / EN ISO 1127 for general service, or DIN 2391 / EN 10305-4 for precision cold-drawn tubes. Tighter-than-standard tolerances are available on request. Contact us for a free quote with your specific tolerance requirements.
Quality Assurance & Testing
Every heat of 444 stainless steel undergoes a comprehensive quality control workflow at Fushun Steel Tube, from incoming raw material verification through finished product certification. Our ISO 9001-certified quality management system ensures full traceability and consistent product quality.
Inspection & Testing Regimen
- Raw Material Inspection
- Chemical analysis by optical emission spectrometry (OES) on every heat; verification of all alloying elements and residuals against the applicable standard.
- In-Process Inspection
- Dimensional checks at each production stage; surface quality monitoring; online eddy current testing during pilgering or cold drawing for early defect detection.
- Finished Product Testing
-
- NDT: 100% eddy current or ultrasonic testing per EN 10246-1 / ASTM E426
- Hydrostatic pressure test per applicable standard
- Tensile testing at room temperature (each batch)
- Hardness testing (each batch)
- Flattening test and flaring test for ductility verification
- Intergranular corrosion test per ASTM A262 Practice E or EN ISO 3651-2
- Dimensional inspection: OD, WT, straightness, ovality
- Surface roughness measurement for precision tubes
- Metallographic examination: grain size, microstructure, inclusion content
EN 10204 Type 3.1 certificates are issued as standard. Type 3.2 certificates with third-party inspection by LR, BV, DNV, TÜV, or SGS are available upon request at the time of order placement.
Packing & Shipping
All 444 stainless steel seamless tubes are packed to prevent mechanical damage and contamination during transit. Standard packing consists of bundling tubes by size and heat number, with end caps or plastic plugs to protect tube ends and prevent ingress of foreign matter. Each bundle is secured with steel strapping and clearly labeled with grade, heat number, dimensions, and quantity.
- Small-diameter precision tubes: Packed in wooden cases or plywood crates with VCI paper interleaving
- Standard seamless tubes: Bundled with end protection, wrapped in waterproof material for sea freight
- Export shipments: Fumigated wooden pallets/crates per ISPM 15
Shipping is arranged via sea freight (FCL/LCL), air freight for urgent orders, or rail for destinations across Eurasia. Fushun Steel Tube works with major shipping lines to provide competitive freight rates and reliable delivery schedules to ports worldwide. Documentation packages include commercial invoice, packing list, mill test certificates, and certificate of origin.
Frequently Asked Questions
- What size range do you supply for 444 stainless steel seamless tubes?
- We supply 444 seamless tubes from OD 6 mm to 325 mm with wall thickness 0.5 mm to 30 mm, in lengths up to 12 meters. Cold-drawn precision tubes are available in smaller diameters with tighter tolerances for heat exchanger and instrumentation applications.
- How does 444 compare to 316L stainless steel for corrosion resistance?
- 444 is immune to chloride stress corrosion cracking (SCC), a failure mode to which 316L is susceptible above approximately 60 °C. 444's PREN of roughly 25 provides pitting resistance comparable to 316L. For hot water, steam condensate, and mildly acidic chloride environments, 444 frequently outperforms 316L while costing less due to its nickel-free composition.
- What standards and certifications apply to 444 stainless steel tubes?
- Our 444 tubes comply with ASTM A268, EN 10216-5, EN 10297-2, and JIS G3463. EN 10204 3.1 certificates are issued for every shipment; Type 3.2 with third-party inspection is available on request. Manufacturing is performed under our ISO 9001-certified quality management system.
- What is the typical delivery time for 444 seamless tubes?
- Ready stock items ship in approximately 7 days. Custom-sized orders with an MOQ of 2–3 tons typically deliver in 25–35 days. We welcome small trial orders for new customers to qualify our material before committing to volume production.
- Can 444 stainless steel tubes be used in high-temperature service?
- 444 offers good oxidation resistance in air up to approximately 950 °C (1742 °F). The titanium stabilization prevents sensitization and intergranular attack after welding, making it suitable for heat exchanger tubes, automotive exhaust components, and moderate-temperature boiler service where chloride SCC risk rules out austenitic grades.
