What Is a Seamless Hastelloy C-4 Pipe?
Hastelloy C-4 Seamless Pipe is supplied for nickel-molybdenum-chromium alloy performance in reducing and thermally cycled service. Available size range: OD 6–1016 mm; WT 0.5–65 mm. The governing specification must be stated on the purchase order: ASTM B622 / ASME SB622, UNS N06455. 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.
The “C-4″(UNS N06455) designation is renowned for its exceptional high-temperature stability. Its ultra-low carbon and silicon content prevents the formation of grain-boundary precipitates in the heat-affected zone (HAZ), making it the gold standard for applications involving long-term exposure to temperatures between 1200°F and 1900°F (650-1040°C). Unlike other nickel alloys, C-4 maintains its ductility and corrosion resistance even after significant thermal cycling.
Key Features and Advantages
- Ultimate High-Temperature Stability: The optimized chemistry minimizes embrittlement, ensuring the pipe remains tough and corrosion-resistant after processing or welding.
- Versatile Corrosion Resistance: Outstanding performance in a wide array of aggressive media, including hot contaminated mineral acids, solvents, and chlorine-bearing environments.
- Localized Corrosion Protection: High molybdenum content ensures superior resistance to pitting and crevice corrosion.
- Stress Corrosion Cracking (SCC) Resistance: Inherently resistant to chloride-induced SCC, outperforming standard austenitic stainless steels.
- Seamless Integrity: Provides a uniform wall thickness and no longitudinal weld seam. Pressure capability is not set by the word “seamless”; it is established by wall thickness, tolerance and the applicable design code.
Technical Specifications & Standards
We provide C-4 pipes compliant with global industrial specifications to ensure seamless integration into your infrastructure.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N06455 | Hastelloy C-4 | 2.4610 | NiMo16Cr16Ti | NW6455 | NS3305 / NS335 (legacy) |
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. See the grade designation index.
Chemical Composition
The composition of C-4 is carefully balanced to achieve its superior corrosion resistance and high-temperature stability.
| Cr | Ni | P | S | Mo | Cu | Co | Fe | Ti | Mn | Si | C |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 14.00 – 18.00 | Bal. | ≤ 0.04 | ≤ 0.03 | 14.00 – 17.00 | ≤ 0.50 | ≤ 2.00 | ≤ 3.00 | ≤ 0.70 | ≤ 1.00 | ≤ 0.08 | ≤ 0.015 |
Data source: ASTM B622 / ASME SB622, UNS N06455 ≤ heat-analysis acceptance limits per the governing standard. Confirm the values against the ordered edition and the MTC.
Typical Mechanical Properties
Hastelloy C-4 is specifically designed to maintain its strength and shape in high-stress, corrosive environments.
| Tensile Strength | Yield Strength | Elongation | Hardness |
|---|---|---|---|
| ≥ 690 MPa | ≥ 276 MPa | ≥ 40% | Not an acceptance limit in ASTM B622-23; measured value reported on the MTC |
Note: Typical values for reference only — not acceptance limits. Mechanical properties are reported on the MTC against the ordered standard, product form, condition and test temperature.
Typical Physical Properties
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 |
|---|---|---|---|---|---|
| 8.64 g/cm³ | 1335 – 1380 °C | 10.8 μm/m·°C | 10.1 W/m·K | 208 GPa | 1.25 μΩ·m |
Note: Typical values for reference only — not acceptance limits. Physical and mechanical properties are reported on the MTC against the ordered standard, product form and condition.
Size & Schedule Chart (ASTM B622)
ASTM B622-23 Dimensional Requirements
- ASTM B622-23 covers seamless nickel and nickel-cobalt alloy pipe and tube, including the C-4 grade covered by this page.
- Tube orders specify outside diameter, minimum or average wall thickness, and length.
- ASTM B622-23 is limited to tubes up to and including 3.5 in. (88.9 mm) outside diameter.
- Pipe orders use standard pipe size and schedule in accordance with Appendix X2.
Table X2.1 – Pipe Schedules (Inches)
| Nominal Pipe Size, in. | Outside Diameter, in. | Schedule 10 Wall, in. | Schedule 40 Wall, in. | Schedule 80 Wall, in. |
|---|---|---|---|---|
| 1/4 | 0.540 | 0.065 | 0.088 | Not listed |
| 3/8 | 0.675 | 0.065 | 0.091 | 0.126 |
| 1/2 | 0.840 | 0.083 | 0.109 | 0.147 |
| 3/4 | 1.050 | 0.083 | 0.113 | 0.154 |
| 1 | 1.315 | 0.109 | 0.133 | 0.179 |
| 1 1/4 | 1.660 | 0.109 | 0.140 | 0.191 |
| 1 1/2 | 1.900 | 0.109 | 0.145 | 0.200 |
| 2 | 2.375 | 0.109 | 0.154 | 0.218 |
| 2 1/2 | 2.875 | 0.120 | 0.203 | 0.276 |
| 3 | 3.500 | 0.120 | 0.216 | 0.300 |
Tolerance basis: permitted variations in outside diameter and wall thickness per the ASTM B622 / ASME SB622 permitted-variations tables for seamless nickel-alloy pipe and tube; dimensions in this chart are nominal reference sizes, not acceptance limits.
Table X2.1 – Pipe Schedules (Millimetres)
| Nominal Pipe Size, in. | Outside Diameter, mm | Schedule 10 Wall, mm | Schedule 40 Wall, mm | Schedule 80 Wall, mm |
|---|---|---|---|---|
| 1/4 | 13.72 | 1.65 | 2.24 | Not listed |
| 3/8 | 17.14 | 1.65 | 2.31 | 3.20 |
| 1/2 | 21.34 | 2.11 | 2.77 | 3.73 |
| 3/4 | 26.67 | 2.11 | 2.87 | 3.91 |
| 1 | 33.40 | 2.77 | 3.38 | 4.55 |
| 1 1/4 | 42.16 | 2.77 | 3.56 | 4.85 |
| 1 1/2 | 48.26 | 2.77 | 3.68 | 5.08 |
| 2 | 60.32 | 2.77 | 3.91 | 5.54 |
| 2 1/2 | 73.02 | 3.05 | 5.16 | 7.04 |
| 3 | 88.90 | 3.05 | 5.49 | 7.62 |
Dimensional Tolerances
ASTM B622-23 requires material to conform to the applicable general requirements of ASTM B829 unless otherwise provided. Permissible dimensional tolerances must therefore be verified against the current ASTM B829 edition and the purchase order; ASTM A790/A999 tolerances do not apply to this nickel-alloy product — those specifications cover duplex stainless steel pipe.
Note: Appendix X2 is nonmandatory information. The listed pipe schedules are regularly available and conform to standards adopted by the American National Standards Institute.
Common Industrial Applications
Due to its unique metallurgical stability, C-4 seamless pipe is the preferred choice for:
Chemical Processing
Reactors, agitators, and piping systems handling hot acids and chlorides.
Pharmaceuticals
High-purity environments where intergranular corrosion resistance must be confirmed against the specified test method and acceptance criteria.
Waste Treatment
Incineration scrubbers and hazardous waste processing.
Pulp & Paper
Bleaching plants and chlorine dioxide stages.
Frequently Asked Questions
What sizes are available for C-4 seamless pipe?
Continuous supply covers OD 6–1016 mm; WT 0.5–65 mm. Requirements outside this range are reviewed against mill capability on request.
Which specification governs C-4 seamless pipe?
ASTM B622 / ASME SB622, UNS N06455 is the governing specification for C-4 seamless pipe. The edition in force at order time is stated on the quotation and purchase order; chemistry, mechanical properties, heat treatment, dimensions and testing are reported against the ordered standard and material heat.
What inspection documents are provided?
Each order is documented with a mill test certificate stating heat chemistry and mechanical test results. EN 10204 3.1 certification, hydrostatic testing, eddy-current or ultrasonic inspection and PMI are performed when specified in the purchase order.
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 NPS and schedule (or actual OD and wall), 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.
