Project Description
SUS429 (UNS S42900) Stainless Steel Seamless Tube
SUS429, also designated as UNS S42900, AISI 429, or DIN 1.4001, is a ferritic stainless steel grade containing 14–16% chromium. As a leaner variant of the widely used SUS430, SUS429 delivers moderate corrosion resistance at a more economical price point while offering improved weldability compared to many standard ferritic grades.
At Fushun Steel Tube, we manufacture SUS429 stainless steel seamless tubes through hot-rolling and cold-drawing processes, ensuring tight dimensional control and consistent mechanical performance. The ferritic microstructure provides excellent resistance to chloride stress corrosion cracking — an advantage over austenitic stainless steels in many service environments. Combined with good thermal conductivity and a lower coefficient of thermal expansion than 300-series grades, SUS429 seamless tubes are a practical choice for heat exchanger tubing, automotive exhaust components, and general engineering applications where cost efficiency and reliable corrosion resistance are both required.
Our SUS429 tubes are produced under an ISO 9001-certified quality management system, with full traceability from steelmaking to final inspection. Whether you need standard stock sizes or custom specifications, contact us for a free quote to discuss your requirements.
SUS429 Stainless Steel Seamless Tube Product Image
Applications of SUS429 Seamless Tubes
The balanced combination of moderate corrosion resistance, good formability, enhanced weldability, and competitive cost makes SUS429 seamless tubes suitable for a wide range of industrial applications:
- Automotive exhaust systems — mufflers, tailpipes, catalytic converter shells, and exhaust manifolds where moderate temperature and corrosion resistance is needed
- Heat exchangers and condensers — tube bundles for low- to medium-temperature heat transfer in mildly corrosive media
- Kitchen equipment and food processing — countertops, sinks, shelving, and food handling components in dry or mildly acidic environments
- Architectural and decorative trim — handrails, balustrades, cladding, and interior design elements requiring a bright or polished surface finish
- Fasteners and cold-formed parts — bolts, screws, rivets, and cold-headed components produced from wire or small-diameter tube stock
- General mechanical engineering — bushings, spacers, rollers, and structural tubular components in mildly corrosive or indoor environments
- Water treatment and plumbing — piping and fittings for potable water, cooling water circuits, and low-chloride industrial water systems
For applications requiring higher chromium content and enhanced corrosion resistance, explore our full range of stainless steel tubes. Tell us your specifications and our engineering team will recommend the optimal grade for your operating conditions.
Specifications & Standards for S42900 Stainless Steel Tubes
SUS429 (UNS S42900) is covered by multiple international standards. The following table summarizes the key tube, pipe, and flat-product standards applicable to this grade:
| Standard | Scope | Product Form |
|---|---|---|
| ASTM A268/A268M | Seamless and welded ferritic and martensitic stainless steel tubing for general service | Seamless & welded tube |
| ASTM A554 | Welded stainless steel mechanical tubing | Welded tube |
| JIS G 4304 | Hot-rolled stainless steel plate, sheet and strip | Plate, sheet, strip |
| JIS G 4305 | Cold-rolled stainless steel plate, sheet and strip | Plate, sheet, strip |
| EN 10297-1 | Seamless circular steel tubes for mechanical and general engineering purposes — technical delivery conditions | Seamless tube |
| EN 10297-2 | Seamless circular steel tubes for mechanical and general engineering purposes — dimensions and tolerances | Seamless tube |
| DIN 17440 | Stainless steels — technical delivery conditions (superseded by EN standards, reference use) | Plate, sheet, strip, tube |
For seamless tube orders, EN 10297-1 and EN 10297-2 are the primary European delivery standards. ASTM A268/A268M serves as the benchmark for North American markets. Our quality team can certify SUS429 tubes to customer-specified standards upon request.
Available Sizes & Delivery
Fushun Steel Tube supplies SUS429 stainless steel seamless tubes in the following dimensional ranges, with both hot-rolled and cold-drawn options available:
| Parameter | Hot-Rolled Seamless | Cold-Drawn / Cold-Rolled Precision |
|---|---|---|
| Outer Diameter (OD) | 16 mm – 530 mm | 6 mm – 219 mm |
| Wall Thickness (WT) | 2 mm – 30 mm | 0.5 mm – 20 mm |
| Length | 5,800 mm – 12,000 mm | 1,000 mm – 12,000 mm (cut to length) |
Delivery Information
- Ready stock for common SUS429 sizes: approximately 7 days from order confirmation
- Custom / non-standard specifications: MOQ 2–3 tons, delivery within 25–35 days
- Small trial orders accepted for special grades and first-time qualification
- Volume orders: negotiable pricing and delivery schedules based on annual contract quantities
Contact us for a free quote with your OD, WT, length, and quantity requirements for a prompt delivery estimate.
Chemical Composition of SUS429 (UNS S42900)
The chemical composition of SUS429 is specified under JIS G 4304, ASTM A268, and related standards. As a ferritic stainless steel, its corrosion resistance is primarily derived from chromium content, with the alloy designed to balance performance and cost. Note that nickel is restricted to a maximum rather than being an intentional addition.
| Element | C (max) | Si (max) | Mn (max) | P (max) | S (max) | Cr | Ni (max) |
|---|---|---|---|---|---|---|---|
| JIS G 4304 (SUS429) | 0.12 | 1.00 | 1.00 | 0.040 | 0.030 | 14.00 – 16.00 | 0.60 |
| ASTM A268 (TP429 / S42900) | 0.12 | 1.00 | 1.00 | 0.040 | 0.030 | 14.00 – 16.00 | 0.75 |
The primary difference between the JIS and ASTM specifications lies in the nickel limit: JIS G 4304 restricts nickel to 0.60% maximum, while ASTM A268 allows up to 0.75%. In practice, residual nickel in SUS429 is typically well below both limits. The chromium range of 14–16% positions this grade as a cost-effective alternative to SUS430 (16–18% Cr) when service conditions do not require the higher chromium content.
Manufacturing Process
Fushun Steel Tube produces SUS429 seamless tubes through an integrated manufacturing route. Steelmaking begins in our EAF with LF refining and VD treatment, ensuring precise control of chemical composition and low inclusion content. For applications demanding exceptional cleanliness, ESR is available as an optional upgrade.
Pipe-making follows two primary routes: hot-rolled seamless for larger diameters and standard wall thicknesses, and cold-drawn / cold-rolled precision processing for tight-tolerance, small-diameter tubes with superior surface finish. After forming, tubes undergo annealing at 780–850 °C to achieve a fully recrystallized ferritic microstructure, followed by pickling and passivation to remove scale and restore the passive chromium oxide layer. Every production batch undergoes chemical verification, mechanical testing, and non-destructive examination before release.
Mechanical Properties
The mechanical properties of SUS429 seamless tubes are evaluated in the annealed condition. Values below represent minimum requirements per JIS G 4304 for hot-rolled plate and ASTM A268 for tubing products. Typical properties from Fushun Steel Tube production often exceed these minimums.
| Property | JIS G 4304 (SUS429) | ASTM A268 (S42900) | Typical Values |
|---|---|---|---|
| Tensile Strength (min) | 450 MPa | 450 MPa (65 ksi) | 480 MPa (69 ksi) |
| Yield Strength / Proof Stress (min) | 205 MPa | 205 MPa (30 ksi) | 260 MPa (38 ksi) |
| Elongation (min) | 22% | 22% (in 50 mm or 2 in.) | 25% |
| Hardness — Brinell (max) | 183 HB | — | 160 HB |
| Hardness — Rockwell B (max) | 88 HRB | — | 78 HRB |
| Hardness — Vickers (max) | 200 HV | — | — |
| Elastic Modulus | — | — | 200 GPa |
| Density | — | — | 7,700 kg/m³ |
The ferritic structure of SUS429 provides good ductility in the annealed condition, with typical elongation values of 25% enabling cold bending, flaring, and moderate forming operations without cracking. Request a sample and we will provide a full mill test report with your order.
Heat Treatment
SUS429 is a non-hardenable ferritic stainless steel — its mechanical properties cannot be increased by quenching. The standard heat treatment is annealing, which relieves stresses from forming and restores a fully recrystallized ferritic microstructure for optimal corrosion resistance and ductility.
| Treatment | Temperature Range | Holding Time | Cooling Method |
|---|---|---|---|
| Annealing | 780 – 850 °C (1436 – 1562 °F) | Based on section thickness (typically 30–60 min per 25 mm) | Air cool or water quench |
| Stress Relieving | 200 – 300 °C (392 – 572 °F) | 1–2 hours | Air cool |
Post-annealing pickling and passivation are critical process steps: they remove surface oxide scale formed during heat treatment and re-establish the passive chromium oxide film responsible for corrosion resistance. For cold-drawn precision tubes, a final bright anneal in a controlled atmosphere furnace can be specified to achieve a clean, scale-free surface without the need for pickling.
Note that SUS429, like all ferritic stainless steels, is susceptible to grain growth if overheated above 900 °C or held at annealing temperatures for excessive durations. Precise furnace control at Fushun Steel Tube ensures consistent grain size and mechanical properties across production lots.
Surface Finish & Tolerances
SUS429 seamless tubes are available in a range of surface finishes to meet diverse application requirements. The standard delivery condition for hot-rolled tubes is pickled and passivated, providing a clean, matte gray surface with the passive oxide layer intact. For applications demanding a higher-quality surface, we offer the following options:
- Pickled & Passivated (Mill Finish) — standard finish for hot-rolled seamless tubes; uniform matte appearance with restored corrosion resistance
- Bright Annealed (BA) — annealed in a controlled atmosphere furnace; mirror-like reflective surface; ideal for decorative and clean-room applications
- Mechanically Polished — available in 180, 320, 400, and 600 grit finishes; used for architectural trim, handrails, and food-grade equipment
- Custom Finishes — electropolishing, bead blasting, and satin brushing available on request
Dimensional tolerances for cold-drawn seamless tubes are held to OD ±0.1 mm and WT ±10% as standard, with tighter tolerances achievable for precision applications. Hot-rolled tubes are supplied to OD ±1.0% and WT ±12.5%, meeting the requirements of ASTM A268 and EN 10297-2. Tell us your specifications and we will confirm the achievable tolerance band for your order.
Quality Assurance & Testing
Every SUS429 seamless tube shipped by Fushun Steel Tube undergoes a rigorous quality control workflow, from raw material inspection to final dispatch. Our ISO 9001-certified quality system ensures consistency and traceability across all production stages:
- Raw Material Inspection
- Incoming billet verification via optical emission spectrometry (OES) for full chemical profile confirmation. Surface quality and dimensional checks of starting billets before charging.
- In-Process Controls
- Continuous monitoring of rolling/drawing parameters, furnace temperatures for annealing, and intermediate dimensional gauging at each forming stage.
- Mechanical Testing
- Room-temperature tensile testing per ASTM A370 / ISO 6892-1; hardness testing (Brinell, Rockwell B, or Vickers); flattening and flaring tests to verify ductility and tube integrity.
- Non-Destructive Testing (NDT)
- 100% eddy current or ultrasonic testing of seamless tubes per ASTM E426 / EN 10246-3 to detect surface and sub-surface defects. Hydrostatic pressure testing available upon request.
- Dimensional Inspection
- OD, WT, length, straightness, and end-squareness verified with calibrated instruments. Surface roughness measurement for precision-grade tubes.
- Metallographic Examination
- Grain size measurement, ferritic microstructure verification, and inclusion rating per ASTM E45 when specified. Intergranular corrosion testing (ASTM A763 practice Z) available for critical applications.
All test results are documented on EN 10204 3.1 certificates issued with each shipment. EN 10204 3.2 certificates with third-party inspection agency endorsement are available at the customer's request.
Packing & Shipping
Proper packaging is essential to preserve the surface quality and dimensional accuracy of SUS429 stainless steel tubes during transit. Fushun Steel Tube applies the following packing standards according to product size and customer requirements:
- Large-diameter tubes (OD ≥ 219 mm) — bundled with steel straps, tube ends fitted with plastic protective caps, and wrapped in waterproof woven fabric
- Medium-diameter tubes (OD 60–219 mm) — hexagonal bundling with steel straps, plastic end caps, and polyethylene shrink wrap for moisture protection
- Small-diameter precision tubes (OD < 60 mm) — packed in plywood cases or heavy-duty corrugated cartons with internal separators to prevent surface-to-surface contact
- Cold-drawn bright tubes — individually wrapped in VCI (Vapor Corrosion Inhibitor) paper before case packing to preserve the bright surface finish
We ship worldwide via ocean freight (FCL/LCL) and air freight for urgent orders. Each shipment carries clear markings with heat number, grade, specification, size, and weight for full traceability. Standard export documentation includes commercial invoice, packing list, certificate of origin, and mill test certificates.
Frequently Asked Questions
What is the difference between SUS429 and SUS430 stainless steel tubes?
SUS429 contains 14–16% chromium, while SUS430 has 16–18%. The lower chromium content makes SUS429 more economical for applications where the full corrosion resistance of SUS430 is not required. SUS429 also offers improved weldability compared to standard 430 grades due to its balanced composition, making it a practical choice for welded fabrications.
Can SUS429 tubes be used for heat exchanger applications?
Yes. SUS429 seamless tubes perform well in heat exchangers operating in mildly corrosive environments at temperatures up to 400 °C. The ferritic structure provides higher thermal conductivity than austenitic stainless steels (approximately 26 W/m·K vs. 15–16 W/m·K for 304/316 grades) and excellent resistance to chloride stress corrosion cracking, a common failure mode in heat exchanger tubing.
What testing and certification does Fushun Steel Tube provide?
All SUS429 tubes are supplied with EN 10204 3.1 mill test certificates as standard, covering chemical analysis, tensile properties, hardness, dimensional inspection, and NDT results. EN 10204 3.2 certificates with third-party witness testing by Lloyd's Register, Bureau Veritas, SGS, or TUV are available upon request.
What is the minimum order quantity for SUS429 seamless tubes?
For standard stock sizes, there is no fixed MOQ — we fulfill orders from a single tube upward. For custom sizes manufactured to your specification, the minimum order quantity is 2–3 tons. Small trial orders for first-time qualification of special grades are welcomed.
Is SUS429 magnetic?
Yes. As a ferritic stainless steel, SUS429 is ferromagnetic in all conditions, unlike austenitic grades (304, 316) which are non-magnetic in the annealed state. This property can be an advantage in applications where magnetic detection or fixturing is used.
