1. Grade and Standards
International Grade: Nickel 200, UNS N02200, W.Nr. 2.4066
Pipe Standards:
(1) ASTM B161 / ASME SB161: Seamless pure nickel pipe (main standard for pressure piping)
(2) ASTM B725: Welded pure nickel pipe
2. Chemical Composition (wt%)
Ni ≥99.0, C ≤0.15, Fe ≤0.40, Mn ≤0.35, Si ≤0.35, Cu ≤0.25, S ≤0.01
Key difference between Ni200 and Ni201: Carbon content
• Ni200: C ≤0.15%; suitable for long-term service up to 315°C; prolonged exposure above 315°C may lead to graphitization embrittlement, where carbon precipitates as graphite at grain boundaries, causing brittleness and cracking
• Ni201: Low carbon content (C ≤0.02%); preferred for high-temperature, strong alkaline environments above 315°C; excellent resistance to intergranular embrittlement at elevated temperatures
3. Physical and Mechanical Properties (Annealed Condition)
• Density: 8.89 g/cm³; Melting point: 1435–1446°C
• Thermal conductivity: 70.2 W/m·K; excellent electrical conductivity; ferromagnetic
• Mechanical properties: Tensile strength ≥345 MPa, yield strength ≥103 MPa, high elongation and good ductility; suitable for bending, flanging, and stamping
• Service temperature range: Continuous use from cryogenic to 315°C; excellent toughness at low temperatures (liquid nitrogen/liquid oxygen), no risk of low-temperature brittle fracture
4. Corrosion Characteristics (Core Material Selection Criteria)
Suitable Media:
(1) Various caustic alkalis (NaOH, KOH): effective across all concentrations and high-temperature caustic conditions; highly resistant to stress corrosion cracking; preferred material in chlor-alkali industry; standard choice for caustic evaporation and alkali transfer lines
(2) Reducing media, neutral salts, distilled water, organic compounds, anhydrous HF; resistant to chloride-induced stress corrosion cracking (SCC); unlike 304/316 stainless steel, it does not suffer from chloride-induced SCC
(3) Food and pharmaceutical applications: complies with FDA contact standards; non-contaminating to process materials
Inapplicable Media: Strong oxidizing acids (nitric acid, concentrated hypochlorous acid), wet chlorine gas, systems containing oxidizers, ammonia solutions; oxidative environments rapidly degrade the passive film on nickel surfaces
Selection guideline: Use Ni200 for strong alkalis and reducing environments; switch to Ni201 for long-term operation above 315°C in strong alkaline conditions; avoid pure nickel in oxidizing environments
5. Product Forms, Manufacturing, and Inspection
(1) Product Types
Seamless Pipes: Extruded and cold-rolled; ideal for small-diameter, thin-walled, high-pressure, and corrosive pipelines; standard wall thicknesses Sch40/Sch80; custom thick-wall options available
Welded Pipes: Plate rolled and welded; suitable for large diameters; lower cost than seamless; weld zone is a potential corrosion weak spot; post-weld solution annealing required in corrosive service
(2) Factory Testing: Hydrostatic test, flattening test; additional tests including ultrasonic testing (UT), eddy current inspection, PMI material identification, and metallographic examination for high-pressure or corrosive applications
6. Welding and Processing Guidelines
(1) Welding: GTAW (TIG welding) is preferred; use ERNi-1 pure nickel filler wire; strictly prohibit mixing with stainless steel filler wires
(2) Characteristics: Poor fluidity of pure nickel welds; molten pool is viscous and prone to porosity; parent material surface must be thoroughly cleaned of oil and sulfur; sulfur can cause hot cracking
(3) Heat Treatment: Supplied in annealed condition; stress relief annealing at 600–800°C recommended after heavy cold working; avoid prolonged holding within 315–600°C range to prevent graphitization embrittlement
(4) Bending: Good cold bending performance; recommend annealing for large deformation bends
7. Typical Industry Applications
(1) Chlor-alkali Chemical Industry: Caustic evaporators, caustic transfer pipelines, caustic storage systems (largest application area)
(2) Chemical Industry: Hydrogenation reaction lines, fluorine chemistry, alkaline organic compounds, anhydrous hydrofluoric acid piping
(3) Pharmaceutical and Food Industry: Food oil hydrogenation, sugar solutions, pharmaceutical intermediate transfer-avoiding metal ion contamination
(4) Battery Industry: Alkaline electrolyte (KOH) piping
(5) Special Heat Exchange: Heat exchanger tubes for strong alkaline media; low-temperature equipment
