Corrosion Resistant Hastelloy Alloy C-22 UNS N06022 W.Nr.2.4602 Welding Bolts for Chemical Processing and Marine Applications

Welding Hastelloy C-22 (UNS N06022, W.Nr. 2.4602) bolts requires expertise due to its high corrosion resistance and alloy composition. This nickel-based alloy, containing chromium, molybdenum, and tungsten, offers excellent resistance to pitting, crevice corrosion, and stress corrosion cracking. For welding, GTAW (TIG) is preferred, using matching filler metals like ERNiCrMo-10. Cleanliness is crucial to prevent contamination, and low heat input minimizes distortion and carbide precipitation. Preheating is unnecessary, and post-weld heat treatment is typically not required. Shielding gas, such as argon or argon-helium mixtures, ensures a stable arc and prevents oxidation. Proper technique results in durable, corrosion-resistant welds suitable for harsh chemical environments, making Hastelloy C-22 bolts reliable in demanding applications.

Welding Hastelloy C-22 (UNS N06022, W.Nr. 2.4602) bolts requires careful consideration due to the material’s composition and properties. Here are the key features to keep in mind:

1. Corrosion Resistance

• Exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking.
• Withstands harsh environments, including oxidizing and reducing agents, making it ideal for chemical processing, marine, and aerospace applications.

2. Weldability

• Highly weldable using common techniques like GTAW (TIG), GMAW (MIG), and SMAW (stick welding).
• Low risk of carbide precipitation, reducing susceptibility to intergranular corrosion.
• Autogenous welding (fusion welding without filler) is possible but may not be ideal for thicker sections.

3. Recommended Filler Material

• Use ERNiCrMo-10 (AWS A5.14) filler wire for GTAW/MIG processes.
• For stick welding (SMAW), ENiCrMo-10 electrodes are recommended.

4. Preheat & Post-Weld Treatment

• No preheating required due to low carbon content.
• Post-weld heat treatment (PWHT) is typically not necessary, but stress-relief annealing at 1100–1150°C (2012–2102°F) may be performed for specific applications.

5. Welding Challenges & Precautions

• Maintain a low heat input to prevent grain growth and hot cracking.
• Use argon shielding gas (pure or Ar-He mix) to avoid oxidation.
• Avoid contamination from iron-based tools or grinding dust to prevent embrittlement.

Applications:

Welding Hastelloy C-22 (UNS N06022, W.Nr. 2.4602) bolts requires special attention due to its high nickel content and excellent corrosion resistance. Here’s what you need to know:

1. Material Characteristics

• Hastelloy C-22 is a nickel-chromium-molybdenum alloy with exceptional resistance to oxidizing and reducing environments.
• Used in harsh chemical processing, marine, and aerospace applications.
• Prone to hot cracking and segregation if not welded correctly.

2. Welding Process Selection

• GTAW (TIG) Welding – Preferred for precision and low heat input.
• GMAW (MIG) Welding – Used for larger weldments but requires pulsed spray transfer.
• SMAW (Stick) Welding – Possible but not commonly used for bolt applications.
• PAW (Plasma Arc Welding) – Effective for automated processes.

3. Filler Material Selection

• Use ERNiCrMo-10 (AWS A5.14) for the best compatibility.
• Alternative: ERNiCrMo-4, but it may have slightly different composition.

4. Pre-Weld Preparation

• Clean the surface thoroughly to remove oil, grease, or oxide layers.
• Use a carbide burr or mechanical cleaning (avoid iron-contaminated tools).
• Maintain sharp edge preparation to avoid porosity.

5. Welding Parameters

• Low heat input to prevent excessive grain growth.
• Interpass temperature: Maintain below 93°C (200°F).
• Use Argon or Argon-Helium shielding gas to prevent oxidation.
• Avoid weaving; use stringer beads instead.

6. Post-Weld Treatment

• Solution annealing at 2050°F (1121°C) and rapid quenching may be needed for optimal corrosion resistance.
• Pickling and passivation with nitric acid to restore corrosion resistance.

7. Application Considerations

• Used in chemical plants, desalination, and high-temperature oxidizing environments.
• Bolt welding should be done with minimal distortion to maintain mechanical properties.
• If possible, consider using mechanical fastening over welding for better reliability.