Alloy 690 features excellent resistance to intergranular corrosion and intergranular stress‑corrosion cracking, and is mainly used as heat‑transfer tube material for steam generators in pressurized‑water‑reactor nuclear power plants. Materials for steam‑generator heat‑transfer tubes of pressurized‑water reactors have gone through an evolutionary development, including 304 austenitic stainless steel, Alloy 600, Alloy 800 and Alloy 690. Studies on corrosion‑related failures of Alloy 600 in service indicate that intergranular corrosion and intergranular stress‑corrosion cracking constitute its primary failure modes. Since being put into service in the 1990s, Alloy 690 applied as heat‑transfer tube material for steam generators in pressurized‑water‑reactor nuclear power plants has had no reported service‑induced damage cases.
Inconel 690 Bolt UNS N06690 / NiCr30Fe / NS3105
Inconel 690 (UNS N06690) bolts are high‑performance fasteners manufactured from nickel‑base superalloy Inconel 690. Benefiting from outstanding corrosion resistance, high‑temperature strength and stress‑corrosion‑cracking resistance, they are widely adopted in harsh environments such as nuclear industry, chemical processing and energy‑generation sectors. Below is the core information:
Parameters:
- Type: Hex Bolt
- Head Style: External Hex Thread
- Tolerance: 6G
- Material: Inconel 690
- Performance Class: 8.8
- Thread Size: M6~M100
- Across‑flat Dimension: 10‑120(mm)
- Head Thickness: 6.6‑60(mm)
- Overall Length: 30~800(mm)
1. Material Characteristics
- Chemical Composition (Typical Values):
- Nickel (Ni) ≥58%, Chromium (Cr) 27‑31%, Iron (Fe) balance, Carbon (C) ≤0.05%, Molybdenum (Mo) ≤0.5%, Aluminum (Al) ≤0.5%, Titanium (Ti) ≤0.5%.
- Strengthening Mechanism: Solid‑solution strengthening. Dense Cr₂O₃ oxide film is formed by high chromium content to improve oxidation and corrosion resistance.
- High‑temperature Performance: Operating temperature up to 1000°C, short‑term temperature tolerance up to 1200°C. Maintains high strength and creep resistance under high‑temperature conditions.
2. Core Advantages
- Corrosion Resistance
- Resistant to oxidizing acids (nitric acid, sulfuric acid), chlorides, seawater and sulfur‑bearing atmospheres. Especially resistant to stress‑corrosion cracking (SCC), suitable for primary‑loop and secondary‑loop systems of nuclear reactors.
- High‑temperature Stability
- Retains high tensile strength (≥586 MPa) and fatigue resistance above 700°C, suitable for long‑term high‑temperature loading.
- Machinability & Weldability
- Formable by hot forging and hot rolling. TIG or MIG welding is recommended with ENiCrMo‑3 filler wire. Post‑weld heat treatment is not required.
3. Application Fields
- Nuclear Industry: Bolts for steam‑generator heat‑transfer tubes and core‑support structural connections of pressurized‑water reactors.
- Chemical Industry: Equipment for nitric‑acid production, nuclear‑fuel reprocessing units, flange bolts for high‑temperature reactors.
- Energy & Environmental Protection: Flue‑gas‑desulfurization components for coal‑fired power plants, radioactive‑waste‑treatment equipment.
- Marine Engineering: Seawater‑desalination equipment, bolts for deep‑sea oil‑production platforms.
4. Standards & Certifications
- International Standards:
- ASTM B446 (bar stock), ASTM F467 (bolts), ISO 4014 (hex bolts), DIN 931 (German‑standard bolts).
- Certifications:
- PED Certification (Pressure‑equipment directive), EN 10204 3.1/3.2 material test certificates, compliant with NACE MR0175 standard for sulfide‑stress‑cracking resistance.
5. Manufacturing Process
- Raw Material: VIM (Vacuum Induction Melting) + ESR (Electro‑Slag Remelting) process to guarantee high purity and homogeneity.
- Forming Methods:
- Hot Forging: Heated to 1050‑1150°C to avoid grain coarsening.
- Cold Working: Solution treatment (1095‑1120°C) is required after cold drawing or cold rolling to restore ductility.
- Surface Treatment: Zinc plating, nickel plating, PTFE coating and other options are available to enhance corrosion resistance and anti‑seizure performance.
6. Typical Mechanical Properties (Room Temperature)
7. Global Grade Equivalents
8. Notes
- Hot‑working Control: Avoid dwelling within the sensitive temperature range of 900‑1000°C to prevent grain coarsening.
- Environmental Compatibility: Keep away from molten metals (e.g. lead, zinc) to prevent hot brittleness.
- Installation Torque: Pre‑tension force shall be precisely controlled to avoid cracking induced by stress concentration.
Summary