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Alloy 330 (UNS N08330) Butt Weld Fittings
Alloy 330 UNS N08330 high temperature pipe and fittings to ASME SB-366 and SB-535. Ni-Fe-Cr-Si grade for furnace parts, heat treating and carburising service.
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Alloy 330, supplied to UNS N08330, is a nickel-iron-chromium-silicon alloy developed for heat-resisting service rather than for general corrosion. The silicon addition is what distinguishes it: roughly 1–1.5% silicon promotes a protective silica scale, which is why Alloy 330 appears in furnace internals, radiant tubes, heat-treating fixtures and continuous-annealing lines where plain 304L or 310s will eventually creep or distort. It is also used in carburising atmospheres and in the handling of molten salts. If your service is seawater or acid, Alloy 330 is the wrong choice — this grade is a heat grade.
Product range and dimensions
Available forms are seamless pipe and tube to ASME SB-535, wrought butt weld fittings to ASME SB-366/SB-366M, and forged or rolled flanges and fittings to ASME SB-462. Fitting types include 90° and 45° long-radius elbows, 180° return bends, equal and reducing tees, concentric and eccentric reducers, and caps, all dimensioned to ASME B16.9. Socket weld and threaded fittings to B16.11 are available on request. Sizes run NPS 1/2 through NPS 12 as standard, with larger sizes and special wall thicknesses subject to review. For elevated-temperature service, wall thickness should be ordered against the pipe schedule rather than a pressure calculation, and we will advise on the minimum usable wall for your design temperature.
Material specifications
| ASME specification | Form | Grade | UNS |
|---|---|---|---|
| SB-535 | Seamless pipe and tube, hot-finished and cold-finished | — | N08330, N08332 |
| SB-366 / SB-366M | Wrought butt weld fittings | WP330 / CR330 | N08330 |
| SB-462 | Forged or rolled flanges, forged fittings and parts | Forgings | N08330 |
Grade comparison
| Element | Alloy 330 (N08330) | 310S (UNS S31000) | Incoloy 800 (N08800) |
|---|---|---|---|
| Nickel | 34.0–37.0 % | 19.0–22.0 % | 30.0–35.0 % |
| Chromium | 17.0–20.0 % | 24.0–26.0 % | 19.0–23.0 % |
| Silicon | 0.75–1.50 % | ≤1.50 % (typical) | ≤1.0 % |
| Carbon, max | 0.08 % | 0.25 % | 0.10 % |
| Manganese, max | 2.00 % | 2.00 % | 1.5 % |
| Copper, max | 1.00 % | — | 0.75 % |
| Primary design basis | Oxidation / carburisation resistance | General heat resistance | High-temperature strength |
Composition per ASME SB-535 Table 1 for N08330; SB-407 Table 1 for N08800. The key difference is that Alloy 330 is selected for scale adherence and oxidation life, while Incoloy 800 is selected for creep strength.
Heat treatment and mechanical properties
SB-366 specifies solution annealing for N08330 at 1900 °F [1038 °C] minimum with rapid air or water cooling. Forged and rolled products to SB-462 Table 2 require:
| Property | Minimum | Specification |
|---|---|---|
| Tensile strength | 95 ksi (655 MPa) | SB-462 Table 2 |
| Yield strength | 45 ksi (310 MPa) | SB-462 Table 2 |
| Elongation in 2 in. (50 mm) | 30.0 % | SB-462 Table 2 |
Note that this is a minimum tensile requirement for forgings; age-hardened or heavily cold-worked material will be stronger. Because Alloy 330 is normally used for its oxidation behaviour rather than its room-temperature strength, most buyers specify condition (hot-finished, cold-finished, or annealed) rather than an allowable stress.
Applications
Heat treating furnace retorts and radiant tubes, continuous annealing and pickling line components, carburising and nitriding furnace parts, radiant burners, heat exchanger components in high-temperature gas streams, and radiant-tube repair couplings.
Certification and inspection
EN 10204 3.1 certification with full heat analysis, PMI verification, dimensional inspection against ASME B16.9, hydrostatic or eddy-current testing where applicable, and intergranular corrosion testing to ASTM A262 on request. For assembly into ASME Section VIII construction, we can supply test specimens cut from forgings as required by the governing clause.
Ordering information
Please specify nominal size, wall thickness or schedule, product form (pipe, tube, butt weld fitting, or forged flange), quantity, service temperature and atmosphere, and destination port. Stating whether the service is oxidising, carburising, or vacuum will let us confirm whether N08330 or a different grade is the correct choice — we would rather flag a mismatch before the order than after delivery.
