1. What are the key features of Inconel 686 / 690 (UNS N06690) round bars and tubes?
Answer:
Inconel 686 and 690 are nickel-chromium-molybdenum alloys designed for high-temperature and corrosive environments. Key features include:
Exceptional resistance to stress corrosion cracking, pitting, and crevice corrosion
High strength at elevated temperatures (up to ~1050°C / 1920°F)
Excellent oxidation resistance
Superior weldability and formability for bars and tubes
Long service life in chemical, petrochemical, marine, and nuclear applications
These features make them ideal for critical components in harsh environments.
2. What is the typical chemical composition of Inconel 686 / 690 (UNS N06690)?
Answer:
| Alloy | Ni (%) | Cr (%) | Fe (%) | Mo (%) | C (%) | Other Elements |
|---|---|---|---|---|---|---|
| Inconel 686 / N06690 | 60–65 | 21–23 | ≤5 | 8–10 | ≤0.10 | Nb+Ta: 1.5–2.5%, Cu: 1–2% |
The combination of nickel, chromium, molybdenum, and niobium provides exceptional corrosion resistance and mechanical strength.
3. What are the typical applications of these round bars and tubes?
Answer:
Common applications include:
Heat exchanger tubes and piping in chemical and petrochemical plants
Reactor components in nuclear power and high-temperature furnaces
Marine engineering and seawater equipment
Oil and gas processing equipment, including offshore platforms
Aerospace and high-temperature industrial machinery
Bars and tubes can be machined, bent, or welded into critical components requiring both strength and corrosion resistance.
4. Which standards apply to Inconel 686 / 690 round bars and tubes?
Answer:
ASTM B444 – Nickel Alloy Bar, Sheet, and Tube
UNS N06690 – Alloy designation
ASME SB444 – Nickel Alloy Bars and Tubes for high-temperature applications
ISO and ASTM specifications for chemical composition, mechanical properties, and dimensional tolerances
Compliance ensures quality, performance, and reliability in critical industrial applications.
5. What are the mechanical properties of Inconel 686 / 690 round bars and tubes?
Answer:
Typical mechanical properties (annealed condition):
| Property | Inconel 686 / 690 |
|---|---|
| Tensile Strength | 827–965 MPa |
| Yield Strength (0.2% offset) | ≥414 MPa |
| Elongation | 30–40% |
| Hardness | 90–105 HRB |
Properties may vary slightly depending on bar/tube diameter, heat treatment, and manufacturing process.
