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.
| Chemical Composition Wt.% | % | Ni | Cr | Fe | C | Mn | Si | Mo | V | P | S | Co | W |
| Min | Bal. | 20 | 2 |
| | | 12.5 | | | | | 2.5 |
| Max | Bal. | 22.5 | 6 | 0.015 | 0.5 | 0.08 | 14.5 | 0.35 | 0.02 | 0.02 | 2.5 | 3.5 |
| Physical Constants | Density(g/cm³) | 8.9 |
| Melting Range(℃) | 1325-1370 |
| Minimum mechanical properties of alloy at room temperature | Typical mechanical properties | Tensile strength Rm N/mm² | Yield strength RP 0.2 N/mm² | Elongation A5 % |
| Solution treatment | 690 | 283 | 40 |
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.
