What Is a Seamless Alloy 120 Tube?
Seamless Alloy 120 Tube — UNS N08120 — is a nitrogen-strengthened Fe-Ni-Cr heat-resistant alloy (35.0–39.0% Ni, 23.0–27.0% Cr, balance iron) produced to ASTM B163 from a solid billet with no weld seam. Note that ASTM B729 covers only N08020/N08024/N08026 — B163-22 is the governing specification for N08120 tube.
Alloy 120 provides the highest strength of the widely used Fe-Ni-Cr materials at temperatures up to 2200 °F (1095 °C), combined with excellent resistance to carburizing and sulfidizing environments and oxidation resistance comparable to other Fe-Ni-Cr grades. The controlled nitrogen, niobium and tungsten additions deliver creep strength approaching nickel-base alloys at roughly half the cost, making it the economical choice for furnace and petrochemical heat-transfer tubing.
Key Features and Advantages
Seamless UNS N08120 tube delivers Fe-Ni-Cr economy with strength to 2200 °F and carburization resistance:
Highest Strength in Its Class to 2200 °F (1095 °C): nitrogen plus niobium and tungsten solid-solution strengthening outperforms conventional 800-series alloys at temperature.
Excellent Carburizing and Sulfidizing Resistance: the balanced 23–27% chromium level with controlled silicon stands up to carbon- and sulfur-bearing furnace atmospheres.
Oxidation Resistance of Fe-Ni-Cr Materials: protective oxide scale forms and re-heals through repeated thermal cycling.
Creep Strength Near Nickel-Base Alloys: approaches alloy 617-class performance at roughly half the material cost thanks to its 33%+ iron balance.
Weldable with Standard Filler: commonly welded using ER3556 (Haynes 556) filler wire; no age-hardening response to complicate fabrication.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for UNS N08120 seamless tube.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N08120 | HR 120 | 2.4854 | NiFe33Cr25Co | Not listed in grade index | NS1502 |
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
UNS N08120 seamless tube chemistry is tightly controlled so the corrosion and mechanical performance below is repeatable:
| Grade | Ni | Cr | Fe | Mo | W | Nb | Co | Cu | Al | Ti | Mn | Si | C |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UNS N08120 | 35.0–39.0 | 23.0–27.0 | remainder | ≤2.50 | ≤2.50 | 0.4–0.9 | ≤3.0 | ≤0.50 | ≤0.40 | ≤0.20 | ≤1.5 | ≤1.0 | 0.02–0.10 |
Chemical requirements per ASTM B163-22, Table 1. Single values are maximum content unless a range is indicated; iron is determined arithmetically by difference. The table also limits P to 0.04%, S to 0.03%, boron to 0.010%, and requires 0.13–0.30% nitrogen — the nitrogen plus niobium and tungsten is what gives Alloy 120 its solid-solution strength at extreme temperature.
Typical Mechanical Properties
Values below are specification minimums for the delivery condition; they define the acceptance basis for UNS N08120 seamless tube.
| Condition | TS, min, ksi (MPa) | YS (0.2% Offset), min, ksi (MPa) | Elongation min, % | Hardness |
|---|---|---|---|---|
| Annealed | 90 (620) | 40 (276) | 30 | … |
Mechanical properties per ASTM B163-22, Table 3, in the annealed condition; B163 sets no stress-relieved requirement for this grade. Each tube is hydrostatically or nondestructive electrically tested per the general requirements of ASTM B829. Strength is retained to 2200 °F (1095 °C) — significantly higher than conventional Fe-Ni-Cr heat-resistant grades.
Typical Physical Properties
These physical properties highlight the material’s ability to perform reliably across a range of environments.
| Density | Melting Range | Thermal Expansion | Thermal Conductivity | Modulus of Elasticity | Electrical Resistivity |
|---|---|---|---|---|---|
| 8.07 g/cm3 | 1300 – 1425 °C (est.) | 14.3 μm/m·°C (25–100°C) | 11.4 W/m·K (20°C) | 197 GPa | 1.05 μΩ·m (20°C) |
Size Tolerance Chart (mm)
Permissible variations for seamless nickel alloy tube in accordance with ASTM B163-22, Table 4:
| Nominal Outside Diameter, in. (mm) | Permissible Variation in OD, mm | Average Wall, % | Minimum Wall |
|---|---|---|---|
| 1/2 to 5/8 (12.7 to 15.9), excl | ±0.13 | ±12.5 | +25% / −0 |
| 5/8 to 1-1/2 (15.9 to 38.1), incl | ±0.13 | ±10 | +20% / −0 |
| over 1-1/2 to 3 (38.1 to 76.2), incl | ±0.25 | ±10 | +22% / −0 |
Notes (dimensions per ASTM B163-22, Table 4, UNS N08825/N06845/N08120 group): tolerances apply to individual measurements and include out-of-roundness (ovality). For thin-wall tubes with a nominal wall of 3% or less of the outside diameter, the mean OD shall comply with the table and individual measurements are increased by 0.5% of the nominal OD. Eccentricity: wall variation in any one cross section shall not exceed ±10% of the actual average wall of that section. For small-diameter and light-wall converter sizes, see Appendix X2 (Table X2.2).
Length Tolerance
- When tube is ordered cut-to-length, the length shall not be less than that specified; a variation of +3.2 mm (1/8 in.) is permitted, and for lengths over 30 ft (9.1 m) a variation of +6.4 mm (1/4 in.) is permitted (ASTM B163-22, 7.2).
- Tube is normally supplied in mill lengths or specific cut lengths as agreed in the order.
Disclaimer: Data above are summarized from ASTM B163-22 (Standard Specification for Seamless Nickel and Nickel-Alloy Condenser and Heat-Exchanger Tubes). The full and most current specification documents must always be consulted for official design and procurement purposes.
Common Industrial Applications
The combination of corrosion resistance, mechanical strength and manufacturing quality makes UNS N08120 seamless tube a preferred choice for:
Heat-Treat Furnaces and Fixtures
Radiant tubes, muffles, retorts, baskets and fixtures in carburizing and sulfidizing atmospheres.
Petrochemical Heater Tubes
Transfer lines and ethylene quench boilers in 900–1050 °C service.
Waste Incineration
Afterburner chambers and kiln components under cyclic oxidation with moderate sulfidation.
Power Generation Boilers
Tube hangers and combustion liners requiring creep strength toward 1000 °C.
Ordering Guide
When specifying UNS N08120 seamless tube, please include: quantity, outside diameter and wall (nominal or minimum), delivery condition, length, and any third-party inspection or supplementary requirements — our sales team will confirm the production schedule and send a formal quotation.
Frequently Asked Questions
What sizes are available for Alloy 120 seamless tube?
The overall range is OD 6–257 mm; WT 0.5–35 mm. Requirements outside this range are reviewed against mill capability on request.
Which specification governs Alloy 120 seamless tube?
ASTM B163 / ASME SB163 is the governing specification for Alloy 120 seamless tube. 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.
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.
