⚡ Quick Specs: Alloy 330
What Is Alloy 330?
Alloy 330 (UNS N08330 / W.Nr. 1.4886, also known as RA330) is an austenitic nickel-iron-chromium-silicon alloy engineered specifically for high-temperature industrial heating applications. With 34–37% nickel and 17–20% chromium, plus a deliberate 0.75–1.5% silicon addition, Alloy 330 combines exceptional oxidation resistance, outstanding carburization resistance, and excellent resistance to thermal shock and cycling — making it the material of choice for furnace fixtures, heat treatment baskets, radiant tubes, retorts, and muffles operating continuously at temperatures up to 1200 °C.
What truly distinguishes Alloy 330 from conventional 310 stainless steel is the synergy between its high nickel content and silicon addition. The nickel provides austenite stability and resistance to sigma-phase embrittlement, while silicon promotes the formation of a tenacious, self-healing silica (SiO₂) sub-scale beneath the chromium oxide layer — dramatically improving resistance to carburization, nitriding, and thermal cycling. As an Alloy 330 manufacturer and supplier, Hangbo Alloy Group offers the grade in sheet, plate, bar, pipe, and custom fabricated furnace components.
Chemical Composition
Nominal composition of Alloy 330 per UNS N08330. All values in weight percent (wt%).
| Element | Min (wt%) | Max (wt%) |
|---|---|---|
| Nickel (Ni) | 34.0 | 37.0 |
| Chromium (Cr) | 17.0 | 20.0 |
| Iron (Fe) | Balance | Balance |
| Silicon (Si) | 0.75 | 1.50 |
| Manganese (Mn) | — | 2.00 |
| Carbon (C) | — | 0.08 |
| Phosphorus (P) | — | 0.030 |
| Sulfur (S) | — | 0.030 |
| Copper (Cu) | — | 1.00 |
Physical Properties
| Property | Value | Unit |
|---|---|---|
| Density | 8.08 | g/cm³ |
| Melting Range | 1340 – 1400 | °C |
| Specific Heat (20 °C) | 460 | J/kg·K |
| Thermal Conductivity (20 °C) | 12.5 | W/m·K |
| Electrical Resistivity (20 °C) | 1.02 | μΩ·m |
| Young's Modulus (20 °C) | 196 | GPa |
| Mean CTE (20–100 °C) | 14.4 | μm/m·°C |
Mechanical Properties
| Property | Typical Value |
|---|---|
| Tensile Strength (Rm, mill annealed) | 550 – 700 MPa |
| Yield Strength (Rp0.2, mill annealed) | 240 – 350 MPa |
| Elongation (A%, mill annealed) | 35 – 45% |
| Hardness (mill annealed) | ≤ 92 HRB |
| Creep Rupture (1000 h at 870 °C) | ~24 MPa |
High-Temperature Performance
- Oxidation resistance: Forms a dual-layer Cr₂O₃/SiO₂ protective scale that resists spalling under severe thermal cycling. Rated for continuous service to 1200 °C in air and combustion gases — equivalent to many nickel-base alloys at lower cost.
- Carburization resistance: The silicon-rich sub-scale acts as an effective carbon diffusion barrier. Alloy 330 resists carbon absorption in endothermic gas, methane, and hydrocarbon-rich atmospheres at temperatures where 310 stainless steel suffers rapid carburization.
- Nitriding resistance: The high nickel content and SiO₂ sub-scale provide excellent resistance to nitrogen absorption in ammonia dissociation, nitriding, and nitrocarburizing furnace environments.
- Thermal shock resistance: The balanced Ni-Cr-Fe composition and stable austenite structure give Alloy 330 outstanding resistance to cracking and distortion during rapid heating/cooling cycles — critical for heat treatment baskets regularly quenched with their loads.
- Sigma phase resistance: The 34–37% nickel content suppresses sigma-phase formation during prolonged exposure at 600–900 °C, preventing the room-temperature embrittlement that limits the useful life of 310 stainless steel fixtures.
Corrosion Resistance
- High-temperature oxidation: Excellent resistance up to 1200 °C in air, flue gas, and mildly oxidizing atmospheres thanks to the Cr₂O₃ + SiO₂ dual-layer scale. Outperforms 310/310S by 50–100 °C in maximum continuous service temperature.
- Carburization environments: The SiO₂ sub-scale blocks carbon ingress in endothermic gas carburizing, carbonitriding, and case-hardening furnaces. Fixture life is typically 2–3× that of 310 stainless steel.
- Nitriding atmospheres: Resists nitrogen absorption during gas nitriding and nitrocarburizing, maintaining ductility and preventing the embrittlement that affects lower-nickel alloys.
- Reducing sulfur gases: Moderate resistance to H₂S and SO₂ at elevated temperatures. For high-sulfur reducing environments, nickel-base alloys such as Alloy 600 or Haynes 556 are preferred.
- Molten salt baths: Good resistance to chloride and carbonate salt baths used in heat treatment, provided the salt chemistry is controlled.
Applications
| Application Area | Typical Components & Notes |
|---|---|
| Heat Treatment Baskets & Fixtures | Furnace baskets, trays, grids, posts, and support frames for carburizing, carbonitriding, hardening, tempering, and annealing operations |
| Radiant Tubes | Gas-fired and electrically heated radiant tubes for indirect heating in controlled-atmosphere furnaces |
| Retorts & Muffles | Fabricated retorts and muffles for batch and continuous furnaces, including bell, pit, and box-type designs |
| Furnace Rolls & Roller Rails | Roller hearth rolls, skid rails, and walking beam components in continuous heat treatment lines |
| Burner Components | Burner nozzles, flame holders, and combustion chamber liners in high-temperature gas and oil burners |
| Petrochemical Furnace Tubes | Reformer tubes, cracking tubes, and pyrolysis coils in ethylene, hydrogen, and ammonia plants |
Available Product Forms
| Product Form | Typical Dimensions & Specifications |
|---|---|
| Sheet & Plate (ASTM B511/ASTM A240) | Thickness 0.5 – 50 mm, hot-rolled or cold-rolled, annealed and pickled |
| Round Bar & Rod (AMS 5730) | φ 6 – φ 300 mm, hot-finished or cold-drawn, solution annealed |
| Seamless Pipe & Tube (ASTM B535) | OD 6 – 168 mm, wall 0.5 – 20 mm, annealed and descaled |
| Welded Tube | OD 10 – 114 mm, wall 0.8 – 6 mm, bright annealed or as-welded |
| Wire & Welding Consumables | φ 0.5 – φ 8.0 mm, bare wire for GTAW/GMAW of matching Alloy 330 components |
| Forgings (AMS 5730) | Custom flanges, rings, and tube sheets per customer specification |
Heat Treatment
| Step | Temperature | Cooling | Purpose |
|---|---|---|---|
| Solution Annealing | 1120 – 1175 °C | Water quench or rapid air cool | Fully solution carbide phases; restore ductility after welding or forming |
| Stress Relieving | 870 – 980 °C | Air cool | Reduce residual stresses from fabrication without reducing corrosion resistance |
Related Standards & Specifications
| Standard | Product Scope / Notes |
|---|---|
| UNS | N08330 |
| DIN / W.Nr. | 1.4886 |
| ASTM B511 | Nickel-Iron-Chromium-Silicon alloy bars and shapes |
| ASTM B535 | Nickel-Iron-Chromium-Silicon seamless pipe and tube |
| ASTM B536 | Nickel-Iron-Chromium-Silicon plate, sheet, and strip |
| AMS 5592 | Sheet, strip, and plate (aerospace) |
| AMS 5716 | Bars, forgings, and rings |
Frequently Asked Questions (FAQ)
1. What is Alloy 330?
Alloy 330 (UNS N08330 / W.Nr. 1.4886, also known as RA330) is an austenitic nickel-iron-chromium-silicon alloy with 34–37% nickel, 17–20% chromium, and 0.75–1.5% silicon. It is designed for continuous high-temperature service up to 1200 °C with exceptional resistance to oxidation, carburization, nitriding, and thermal shock — making it the standard material for industrial furnace fixtures and heat treatment equipment.
2. What is the chemical composition of Alloy 330?
Nominal Alloy 330 composition (wt%): Ni 34.0–37.0, Cr 17.0–20.0, Fe balance, Si 0.75–1.50, Mn ≤2.00, C ≤0.08. The high nickel content ensures austenite stability and sigma-phase resistance, while the deliberate silicon addition creates a protective SiO₂ sub-scale beneath the chromium oxide — the key to its superior carburization endurance.
3. What is the density and melting range of Alloy 330?
Alloy 330 has a density of approximately 8.08 g/cm³ (0.292 lb/in³) and a melting range of about 1340–1400 °C (2445–2550 °F). Its density is slightly lower than pure nickel alloys, giving a modest weight advantage in large furnace fabrications.
4. What is the maximum service temperature of Alloy 330?
Alloy 330 is rated for continuous service up to 1150–1200 °C (2100–2190 °F) in air and oxidizing atmospheres. In carburizing or nitriding environments, the practical maximum is around 1100 °C due to the gradual breakdown of the protective scale. This is 50–100 °C higher than 310 stainless steel for equivalent service life.
5. How does Alloy 330 compare to 310 stainless steel?
Alloy 330 contains significantly more nickel (34–37% vs 19–22%) and adds deliberate silicon (0.75–1.5%). These differences give it: (1) 50–100 °C higher maximum service temperature; (2) dramatically better carburization and nitriding resistance; (3) superior sigma-phase resistance (no room-temperature embrittlement); (4) 2–3× longer fixture life in case-hardening furnaces. The trade-off is higher material cost, offset by longer service life.
6. What makes Alloy 330 resistant to carburization?
The 0.75–1.5% silicon addition forms a dense, adherent silica (SiO₂) sub-scale beneath the chromium oxide layer. This SiO₂ film acts as an effective diffusion barrier against carbon, preventing carbon ingress into the base metal where it would form embrittling chromium carbides. Standard 310 stainless steel lacks this silica barrier and carburizes much faster.
7. Can Alloy 330 be welded?
Yes, Alloy 330 has good weldability using GTAW, GMAW, and SMAW with matching AWS A5.14 ERNiCr-3 (Inconel 82) or matching Alloy 330 filler. Controlled heat input and minimal interpass temperature are recommended. Post-weld solution annealing at 1120–1175 °C restores full carburization resistance in the heat-affected zone.
8. Does Alloy 330 become brittle after prolonged high-temperature exposure?
Unlike 310 stainless steel, which forms embrittling sigma phase after prolonged exposure at 600–900 °C, Alloy 330's 34–37% nickel content suppresses sigma formation. This means Alloy 330 fixtures remain ductile (not brittle) at room temperature even after years of furnace service — a critical safety and handling advantage.
9. What product forms are available for Alloy 330?
Hangbo Alloy supplies Alloy 330 in sheet, plate, bar, seamless and welded pipe/tube, wire, forgings, and custom fabricated furnace components such as baskets, retorts, radiant tubes, and muffles. Standard specifications include ASTM B511 (bar), ASTM B535 (pipe), and ASTM B536 (sheet/plate).
10. How much does Alloy 330 cost and what is typical lead time?
Alloy 330 is priced between 310 stainless steel and full nickel-base alloys such as Alloy 600. Standard mill products (sheet, plate, bar) are available from stock or with 2–4 week lead times. Custom fabricated furnace fixtures require engineering review; contact Hangbo Alloy at hangbo@nickel-alloy.com for a project quotation.
11. What is the difference between Alloy 330 and Inconel 600?
Both are high-nickel, high-chromium alloys, but Alloy 330 (34–37% Ni, 17–20% Cr) contains significantly more iron and adds deliberate silicon, while Inconel 600 (~72% Ni, ~15.5% Cr) is nickel-dominant. Alloy 330 offers better carburization resistance and a slightly higher oxidation ceiling, while Inconel 600 provides superior aqueous corrosion resistance and chloride SCC resistance. Alloy 330 is more cost-effective for furnace fixtures; Inconel 600 is preferred for chemical/nuclear environments.
12. Is Alloy 330 magnetic?
Alloy 330 is fully austenitic and non-magnetic in the annealed condition. Some slight magnetic response may develop after heavy cold working, but service in furnace applications does not produce magnetic transformation.
Need Alloy 330 for Furnace Fixtures or High-Temperature Equipment?
Hangbo Alloy Group is a trusted global manufacturer and supplier of Alloy 330 (UNS N08330 / 1.4886) in sheet, plate, bar, pipe, and fabricated components. Mill test certificates, full traceability, custom fabrication, and competitive pricing.