Alloy 330 (RA330) Fasteners: Complete Technical Data – Tensile, Temperature, Torque, Creep & More

When designing bolted connections for the most extreme high‑temperature environments—furnace hardware, heat‑treat fixtures, radiant tubes, and carburizing atmospheres—engineers need precise data on Alloy 330 fastener performance. RAYCHIN LIMITED, a specialist global manufacturer and supplier of high‑temperature alloy fasteners with decades of in‑house experience, provides this authoritative technical reference. We cover Alloy 330 tensile strength, yield strength, hardness, maximum temperature limits, oxidation and carburization resistance, torque values, galling prevention, machining guidelines, heat treatment protocols, creep strength, and stress rupture properties. All data is drawn from ASTM B511 and our own production testing, giving you the confidence to design reliable joints for the hottest applications.

1. Mechanical Properties at Room Temperature

In the solution‑annealed condition per ASTM B511, the minimum mechanical properties of Alloy 330 tensile strength and Alloy 330 yield strength are as follows. The alloy is solid‑solution strengthened and achieves good ductility along with its outstanding high‑temperature capabilities.

Alloy 330 hardness is moderate, ensuring good ductility and resistance to brittle fracture. The alloy cannot be hardened by heat treatment, relying instead on its nickel‑chromium‑silicon matrix for both strength and environmental resistance.

2. Extreme High‑Temperature Capabilities

Alloy 330 maximum temperature for continuous service in oxidizing atmospheres is approximately 1150°C (2100°F). Under intermittent conditions, it can withstand even higher excursions. Its Alloy 330 oxidation resistance is provided by the 17–20% chromium and 1.0–1.5% silicon content, which forms a dense, adherent protective scale that resists flaking and further attack.

Where Alloy 330 truly excels is in carburization resistance. The 34–37% nickel content prevents the inward diffusion of carbon that embrittles standard stainless steels, making it the definitive choice for fasteners in carburizing furnaces, case‑hardening fixtures, and petrochemical pyrolysis equipment. Similarly, Alloy 330 nitriding resistance is excellent: in ammonia‑based nitriding atmospheres, the alloy resists the formation of hard, brittle surface layers that could compromise fastener integrity.

For design considerations, Alloy 330 thermal expansion is moderate. The mean coefficient of thermal expansion from 20–100°C is approximately 16.0 µm/m·°C, rising to about 18.0 µm/m·°C at 1000°C. This is close to that of many cast stainless steels and should be accounted for in bi‑metallic joints to minimize thermal stress.

3. Torque Values and Tightening Recommendations

Achieving the correct preload without damaging threads requires accurate Alloy 330 torque values. Due to its moderate yield strength, over‑torquing must be avoided. The Alloy 330 bolt tightening torque table below is based on 50% of the minimum yield strength (120 MPa effective stress) and a lubricated nut factor K = 0.18, which is typical for this alloy when assembled with a nickel‑based anti‑seize compound.

Always use clean, lubricated threads, a calibrated torque wrench, and a slow, steady application speed. RAYCHIN can provide customized torque charts for your specific geometry and lubrication condition upon request.

4. Galling Resistance and Assembly

Alloy 330 galling resistance is moderate, typical of austenitic stainless steels. The alloy can gall under high contact stress if assembled dry or at excessive speed. To ensure reliable assembly, RAYCHIN recommends:

• Using rolled threads for a smoother surface finish.
• Applying a high‑temperature anti‑seize compound, such as nickel‑based or cermet‑based lubricants.
• Pairing with a nut of slightly different hardness or a dissimilar compatible alloy.
• Avoiding impact tools; use slow, controlled torque wrenches.

5. Machining Alloy 330 Fasteners

Machining Alloy 330 fasteners requires techniques appropriate for high‑nickel austenitic alloys. The material work‑hardens rapidly and generates significant heat at the cutting edge. RAYCHIN's experienced machinists employ:

• Rigid CNC turning centers with positive‑rake carbide inserts.
• Moderate cutting speeds and aggressive feed rates to minimize work hardening.
• High‑pressure coolant delivery for chip evacuation and temperature control.
• Thread rolling after machining for superior fatigue life and surface finish.

6. Heat Treatment: Solution Annealed

Alloy 330 heat treatment consists of solution annealing at 1050–1120°C (1920–2050°F), followed by rapid water quenching. This dissolves any carbides that may have formed during processing and restores a fully austenitic microstructure with maximum ductility and corrosion resistance. RAYCHIN performs all solution annealing in‑house, with full furnace charts provided in the certification package. No subsequent aging or hardening is performed, as Alloy 330 is not a precipitation‑hardening alloy.

7. Creep and Stress Rupture Properties

For fasteners that must carry load at extreme temperatures over extended periods, Alloy 330 creep strength and stress rupture data are essential. At 870°C (1600°F), the 1000‑hour stress‑rupture strength is approximately 15 MPa (2.2 ksi). At 650°C (1200°F), this rises to approximately 55 MPa (8 ksi). While Alloy 330 provides adequate creep resistance for many furnace applications, designs requiring higher creep strength at temperatures above 900°C may require the upgrade to nickel‑base superalloys such as Inconel 601 or Nimonic 75.