N04400 welding process technology

N04400 (commercially known as Monel 400) is a nickel-copper alloy renowned for its exceptional corrosion resistance and mechanical stability in aggressive environments. Its composition balances nickel (63–70%) and copper (28–34%), with trace elements including iron (≤2.5%), manganese (≤2.0%), silicon (≤0.5%), carbon (≤0.3%), and sulfur (≤0.024%)39. This alloy is widely used in marine engineering, chemical processing, and aerospace due to its ability to withstand seawater, acids (e.g., hydrofluoric acid), alkalis, and high-temperature vapors110.

Mechanical Properties at Room Temperature:

: ≥480 MPa

: ≥195 MPa

: ≥35%

: 135–179 HB

: 8.80 g/cm³

: 1,300–1,350°C36

N04400 stands out from other nickel alloys (e.g., Inconel, Hastelloy) due to its unique nickel-copper matrix and exceptional performance in reducing environments:

: Unlike chromium-dominated alloys (e.g., Inconel 600), N04400 excels in neutral-to-reducing media, particularly resisting chloride stress corrosion cracking and hydrofluoric acid—a weakness for many stainless steels310.

: At 21.8 W/m·K, it surpasses most nickel-chromium alloys (e.g., Inconel 600: ~14 W/m·K), enabling efficient heat dissipation in heat exchangers36.

: Lower nickel content (vs. pure nickel alloys) and no costly additions like molybdenum (e.g., Hastelloy C276) make it economical for large-scale marine applications9.

: Surfaces must be cleaned with acetone to remove oils, oxides, and sulfur residues to prevent porosity and cracking410.

: ERNiCu-7 (AWS A5.14) or ENiCu-7 (AWS A5.11) wires/electrodes are mandatory to match base metal composition and avoid segregation-induced cracks46.

: High-purity argon (99.99%) with 8–12 L/min flow rates to block O₂/N₂ contamination during TIG/MIG welding410.

: Low currents (70–120 A for TIG) and interpass temperatures <100°C prevent grain coarsening and hot cracking4.

: Preferred for precision; DCEN polarity, Ø3mm tungsten electrode, and narrow bead profiles minimize heat-affected zone (HAZ) defects14.

: Suitable for high-deposition projects but requires stringent gas shielding1.

: Used for field repairs; requires pre-dried ENiCu-7 electrodes (350°C × 1hr)4.

: Sulfur/phosphorus impurities form low-melting eutectics, causing cracks in weld craters. Strict control of S/P content (<0.024%) is critical410.

: Trapped gases (O₂, H₂) due to inadequate shielding result in voids. Solution: Double-purge assemblies with argon10.

: Rapid cooling induces residual stresses. Preheating (thick sections >10mm) and controlled cooling rates mitigate this14.

: Annealing at 700–900°C reduces residual stresses and restores ductility710.

: Radiography (X-ray) or ultrasonic inspection detects cracks/porosity; bend tests (180° angle) validate joint integrity4.

: Grinding/polishing removes oxide layers and enhances corrosion resistance1.

Kherlyn specializes in manufacturing thin-walled N04400 welded tubes (10–450mm diameters) with zero minimum order quantity (MOQ). Our laser-welded tubes feature:

: Achieved via automated TIG with real-time argon shielding.

: Tailored for corrosive/ high-stress environments.

 Ø325mm × 35mm tubes for brine heaters. Withstood 90°C saline water (Cl⁻: 40,000 ppm) for 5+ years without leaks69.

Ø150mm tubes for HF vapor lines; passed 10,000-hour corrosion tests (0.01mm/yr erosion rate)36.