Alloy 330 (RA330) Fasteners: The Ultimate High‑Temperature, Carburization‑Resistant Bolts

For the most extreme furnace and heat‑treatment environments—where temperatures approach 1150°C and both oxidation and carburization threaten fastener integrity—Alloy 330 stands apart. Also known as RA330 or UNS N08330, this high‑nickel, high‑chromium austenitic alloy provides exceptional resistance to carburization, thermal shock, and scaling, making it the definitive choice for heat‑treat baskets, radiant tubes, and industrial furnace bolting. RAYCHIN LIMITED, a specialist global manufacturer and supplier of high‑temperature alloy fasteners with decades of in‑house experience, produces the complete range of Alloy 330 bolts, studs, nuts, and custom parts. This guide explains the material, its chemistry, properties, and why it is irreplaceable in extreme thermal applications.

1. What Is Alloy 330 Material?

What is Alloy 330 material? Alloy 330 (UNS N08330), commonly known as RA330 (Rolled Alloys 330), is a high‑nickel (35%), high‑chromium (19%) austenitic stainless steel specifically engineered for extreme high‑temperature service in carburizing and oxidizing atmospheres. The high nickel content provides outstanding resistance to carburization—the diffusion of carbon into the metal that embrittles lower‑grade alloys—while the chromium content ensures oxidation resistance up to approximately 1150°C (2100°F). The alloy is also known as Alloy 330 nickel chromium alloy because of its unique Ni‑Cr balance, which provides a stable austenitic structure without the sigma‑phase embrittlement that plagues standard 310 stainless steel at intermediate temperatures.

2. Alloy 330 Chemical Composition (UNS N08330)

The Alloy 330 chemical composition is carefully balanced to resist both oxidation and carburization. The typical RA330 alloy composition per ASTM B511 is presented below.

3. Alloy 330 Properties — Mechanical, Physical, and High‑Temperature

Alloy 330 properties in the solution‑annealed condition combine good strength with outstanding high‑temperature stability. Typical room‑temperature mechanical properties are:

• Tensile Strength: ≥ 550 MPa (80 ksi)
• Yield Strength (0.2% offset): ≥ 240 MPa (35 ksi)
• Elongation: ≥ 30%
• Hardness: ≤ 95 HRB

Key physical properties include a density of 8.05 g/cm³, a melting range of 1370–1425°C, and a mean coefficient of thermal expansion of 16.0 µm/m·°C (20–100°C). Alloy 330 high temperature bolts retain approximately 70% of their room‑temperature strength at 870°C and resist scaling and carburization up to 1150°C.

4. Alloy 330 Equivalent Grade and RA330 Fasteners

Alloy 330 equivalent grade designations include UNS N08330, RA330 (Rolled Alloys tradename), and EN 1.4864 / 1.4876 (though the EN grades have slightly different compositions). RA330 fasteners is the common commercial designation, and RAYCHIN manufactures to the UNS N08330 specification with full traceability. The alloy is often compared to 310 stainless steel, but its higher nickel content provides superior carburization resistance and structural stability at extreme temperatures.

5. RAYCHIN's Alloy 330 Fastener Product Range

RAYCHIN LIMITED supplies the complete line of UNS N08330 fasteners for global high‑temperature furnace and heat‑treatment applications:

• Hex bolts – ASME B18.2.1, DIN 931/933, M6–M48, 1/4″–2″
• Stud bolts and threaded rod – ASME B16.5, DIN 976, M6–M64, 1/4″–2‑1/2″
• Socket head cap screws – ASME B18.3
• Heavy hex nuts and washers
• Custom parts – per your drawings; flanged bolts, stepped studs, furnace hardware

All products are solution‑annealed, with full material certification, PMI testing, and EN 10204 3.1 as standard (3.2 available).