ERNiCu-7 MIG WIRE

ERNiCu-7 is a nickel-copper alloy welding wire that conforms to the classification in the American Welding Society (AWS) A5.14 standard. Its nominal composition is approximately 65% ​​nickel (Ni) and 30% copper (Cu), with small amounts of iron (Fe), manganese (Mn), titanium (Ti), and other elements added to optimize performance. This welding wire is specifically designed for welding nickel-copper alloys (such as Monel 400, Monel K500, etc.) and can also be used for dissimilar metal joining (such as welding nickel-copper alloys to carbon steel and stainless steel). Its core advantages lie in its excellent corrosion resistance, high-temperature stability, and crack resistance, making it widely used in marine engineering, chemical equipment, nuclear industry, and high-temperature and high-pressure vessel manufacturing.

Typical Chemical Composition (%)

Ni: ≥63.0

Cu: 28.0-34.0

Fe: ≤2.5

Mn: ≤2.0

Ti: ≤0.5

C: ≤0.15

Total other impurities: ≤0.5

Core Performance

• Corrosion Resistance: Exhibits excellent corrosion resistance to media such as seawater, sulfuric acid, and hydrofluoric acid, especially outstanding in chloride stress corrosion environments.
• High-Temperature Performance: Maintains stable mechanical properties below 538℃ and has excellent oxidation resistance.
• Crack Resistance: Low thermal expansion coefficient and good ductility reduce the tendency for welding hot cracking.
• Process Adaptability: Suitable for various welding methods (GTAW, GMAW, SAW), with moderate weld metal fluidity.

Preparation Before Welding

Base Metal Treatment: Thoroughly clean the welding area to remove oil and oxides. Acetone or alcohol is recommended for cleaning.

Groove Design: V-groove or U-groove, angle 60°-70°, root face 1-2mm, gap 2-3mm.

Preheating Control: When the base metal thickness is >12mm, preheating to 100-150℃ is required to prevent cracking due to rapid cooling.

Welding Parameter Selection

Gas Shielded Arc Welding (GTAW/GMAW):

Shielding Gas: Pure Ar or Ar+He (He≤25%) mixed gas, flow rate 15-20 L/min.

Current Range: GTAW DCEN (Direct Current Electrode Negative) 80-150A, GMAW 160-220A.

Welding Wire Diameter: Commonly 1.2mm (GMAW), 2.4mm (SAW).

Interpass Temperature: Control below 150℃ to prevent grain coarsening.

Operating Techniques

Short Arc Welding: Use low voltage and low current short arc operation to reduce weld pool oxidation.

Oscillation Control: Narrow weld bead, no oscillation or slight oscillation to avoid excessively wide weld pool.

Arc Termination Treatment: Fill the crater to prevent crater cracking; use the current decay function if necessary.

Post-Weld Treatment

Heat Treatment: Generally not mandatory, but if stress relief is required, it is recommended to hold at 600-650℃ for 1 hour followed by slow cooling.

Surface Cleaning: Remove slag and oxide layer; stainless steel wire brush or pickling and passivation can be used.

Marine Engineering: Seawater desalination equipment, marine pumps and valves, subsea pipeline welding.

Chemical Equipment: Sulfuric acid storage tanks, hydrofluoric acid reactors, chlor-alkali industry heat exchangers.

Energy Sector: Nuclear power plant cooling systems, geothermal well casings, high-temperature steam valves.

Dissimilar Material Joining: Monel alloy and carbon steel transition joints, stainless steel and nickel-copper alloy composite structures.

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