Welding Hastelloy Bar C-22 UNS N06022 W.Nr.2.4602 Suitable For Environments With Alternating Oxidizing And Reducing Conditions

Welding Hastelloy C-22 (UNS N06022, W.Nr. 2.4602) nuts requires careful control due to its high corrosion resistance and nickel-based composition. The material is highly resistant to oxidizing and reducing environments, making it ideal for chemical processing and marine applications. Gas Tungsten Arc Welding (GTAW/TIG) is preferred, using ERNiCrMo-10 filler metal for best compatibility. Proper shielding gas, such as argon or helium, prevents oxidation. Preheating is not required, but interpass temperatures should be kept below 93°C (200°F) to avoid carbide precipitation. Post-weld treatments are generally unnecessary, though solution annealing can restore corrosion resistance. Cleanliness is critical to prevent contamination. Proper technique ensures strong, defect-free welds, maintaining the nut’s mechanical properties and corrosion resistance.

Welding Hastelloy C-22 (UNS N06022, W.Nr. 2.4602) nuts requires special considerations due to the alloy's unique properties. Here are the key features to keep in mind:

1. Material Composition & Properties

• High Corrosion Resistance: Excellent resistance to oxidizing and reducing environments, making it ideal for harsh chemical processing applications.
• Nickel-Based Alloy: Contains Nickel (~56%), Chromium (~22%), Molybdenum (~13%), Iron (~3%), and small amounts of Cobalt, Tungsten, and others.
• Low Carbon Content: Minimizes carbide precipitation and intergranular corrosion.

2. Welding Considerations

• Filler Material: Use ERNiCrMo-10 (AWS A5.14) or a similar nickel-based filler wire to match the alloy’s corrosion resistance.
• Preheating & Post-Weld Treatment:
• No preheating is required.
• Post-weld heat treatment is usually unnecessary but can be considered in highly corrosive environments.
• Shielding Gas: Use pure argon or an argon-helium mix for GTAW (TIG) welding.
• Heat Input Control: Maintain low heat input to prevent grain growth and maintain mechanical properties.

3. Common Welding Processes

• GTAW (TIG): Preferred method for precise and clean welding of small components like nuts.
• GMAW (MIG): Can be used but requires careful heat control.
• PAW (Plasma Arc Welding): Used for automated and high-precision applications.

4. Challenges & Precautions

• Avoid Contamination: Clean surfaces thoroughly to prevent contamination from iron, sulfur, or other elements.
• Cracking Resistance: Hastelloy C-22 has good resistance to hot cracking but still requires careful weld bead placement.
• Weld Oxidation Control: Back purging with argon helps prevent oxidation in root passes

Applications:

Welding Hastelloy C-22 (UNS N06022, W.Nr. 2.4602) nuts or components requires careful consideration due to its high corrosion resistance, especially against pitting, crevice corrosion, and stress corrosion cracking. Here’s a detailed guide to welding applications for Hastelloy C-22 nuts:

1. Welding Considerations

• Filler Material: Use ERNiCrMo-10 (AWS A5.14) or ENiCrMo-10 (AWS A5.11) filler metal.
• Welding Process: Preferable methods include:
• GTAW (TIG) – Best for precise and clean welds.
• GMAW (MIG) – Used when speed is a priority.
• SMAW (Stick Welding) – Suitable for field applications.
• PAW (Plasma Arc Welding) – Used for high-quality fusion.
• Preheat & Post-Weld: No preheating is required, and post-weld heat treatment (PWHT) is usually not necessary, but stress relief annealing at 1100–1200°F (593–649°C) can be done if needed.
• Interpass Temperature: Maintain below 200°F (93°C) to prevent grain growth and sensitization.

2. Nut Application Welding

• Tack Weld Carefully: Avoid excessive heat input, which can cause distortion.
• Controlled Heat Input: Keep the heat input low to prevent carbide precipitation.
• Shielding Gas: Use pure argon or argon-helium mixtures to protect the weld pool.
• Back Purging: Recommended when welding critical applications to maintain corrosion resistance inside the nut.
• Cleaning: Remove oxides and contaminants before welding using mechanical or chemical cleaning.

3. Applications of Hastelloy C-22 Nuts

• Chemical Processing: Used in reactors, heat exchangers, and piping systems where extreme corrosion resistance is required.
• Marine & Offshore: Ideal for saltwater environments and harsh offshore conditions.
• Aerospace: Used in components that face extreme temperatures and corrosive environments.
• Pharmaceutical & Food Processing: Preferred due to high purity and resistance to contamination.
• Power Generation: Suitable for high-temperature and acidic environments in scrubbers and heat recovery systems.