Monel 400 and Monel K-500 are both nickel-copper alloys, but they serve different roles depending on the mechanical and environmental demands of the application.
Monel 400 (UNS N04400) is the standard grade containing approximately 67% nickel and 30% copper. It delivers excellent corrosion resistance in seawater, hydrofluoric acid, and alkaline environments. Monel 400 flanges are widely used in marine piping systems, chemical processing plants, and oil refinery applications where corrosion resistance is the primary concern.
Monel K-500 (UNS N05500) builds on the base Monel 400 composition by adding small amounts of aluminum and titanium. These additions allow the alloy to be age-hardened, producing significantly higher strength and hardness than Monel 400. K-500 flanges are preferred in applications that require both corrosion resistance and high mechanical strength, such as pump shafts, valve stems, and high-pressure marine systems.
Key differences between the two alloys include tensile strength (Monel 400 ranges from 70-85 ksi while K-500 reaches 100-130 ksi after age hardening), hardness (K-500 achieves Rockwell C 25-35 versus Monel 400 at Rockwell B 60-80), and cost (K-500 carries a premium due to the additional alloying and heat treatment).
Both alloys are manufactured to ASTM B564 and are available in all standard flange types including weld neck, slip-on, blind, socket weld, threaded, and lap joint configurations. Pressure classes range from 150 through 2500.
For most marine and chemical processing applications where corrosion resistance is the primary requirement, Monel 400 flanges provide the best value. When the application demands higher strength or hardness alongside corrosion resistance, Monel K-500 is the better choice.
Contact us at 281-484-8325 for help selecting the right Monel alloy for your specific application requirements.