Monel K-500/UNS N05500/W.Nr. 2.4375/Alloy 500 bar

Monel K-500 bar, designated as UNS N05500, material number W.Nr. 2.4375, and commonly known as Alloy K-500 or Alloy 500, is a precipitation-hardenable nickel-copper alloy that combines the excellent corrosion resistance of Monel 400 with significantly higher strength and hardness. This bar stock form achieves its enhanced properties through the addition of aluminum and titanium, which form strengthening gamma prime precipitates during aging heat treatment. It is a critical material for machining high-strength, corrosion-resistant components such as pump shafts, valve stems, fasteners, and marine propulsion components.

Introduction to Monel K-500 (Alloy K-500)

Monel K-500 is an age-hardenable version of Monel 400. While maintaining the excellent general corrosion resistance of its predecessor, the addition of aluminum and titanium allows it to be strengthened to levels comparable to many steels, while retaining good ductility and toughness. The bar stock is typically supplied in the solution-annealed condition for fabrication and then age-hardened to achieve its final high strength. It is indispensable for applications requiring both the corrosion resistance of nickel-copper alloys and the mechanical strength to withstand high stress, such as in offshore, marine, and chemical processing equipment.

Chemical Composition of Monel K-500 Bar

The composition of Monel K-500 bar builds upon Monel 400 with specific additions for precipitation hardening. Supplied by Shanghai NC Metal Materials Co., Ltd., the bar stock is produced to precise specifications to ensure proper response to heat treatment.

Mechanical Properties of Monel K-500 Bar (Heat Treated)

The mechanical properties of Monel K-500 bar are highly dependent on its heat treatment condition. The standard treatment involves solution annealing followed by aging.

Typical Value (Aged Condition – Temper H)

Physical Properties of Monel K-500 Bar

The physical properties of Alloy K-500 are similar to Monel 400, with slight variations due to the different composition.

Standard Specifications, Bar Forms, and Available Sizes

Shanghai NC Metal Materials Co., Ltd. supplies Monel K-500 bar in various conditions, from annealed for fabrication to pre-aged for direct machining of high-strength parts.

Primary Applications of Monel K-500 Bar Stock

Machined or forged components from Monel K-500 bar are used in demanding applications requiring strength and corrosion resistance: Marine & Offshore: High-strength propeller shafts, pump shafts, valve stems, fasteners (bolts, studs), and mooring system components for ships and offshore platforms. Oil & Gas: Drill collars, tool joints, valve trim, and components for sour service (H2S) wells. Chemical Processing: Agitator shafts, mixer blades, and pump components handling corrosive media under high stress. Aerospace: High-strength fasteners and components for engine controls. Power Generation: Bolting, springs, and wear parts in turbines and other equipment.

Heat Treatment

The properties of Monel K-500 are developed through a two-step heat treatment: Solution Treatment: Heating to 980°C (1800°F), holding, and rapidly cooling (water quench). This dissolves the aluminum and titanium into the matrix. Aging Treatment: Heating to 595-620°C (1100-1150°F) for a specified time (typically 16 hours), then air cooling. This causes the precipitation of fine, coherent gamma prime (Ni3Al) particles, which impart high strength. Bar is often supplied in the solution-annealed condition (Condition A) for fabrication, with aging performed after machining.

Machining and Fabrication

Machining Monel K-500 bar is most efficiently done in the softer, solution-annealed condition before final aging. In this state, it machines similarly to Monel 400, though it is somewhat tougher. Recommendations include sharp tools, moderate speeds/feeds, and good coolant. Machining in the fully aged condition is difficult due to high strength and hardness, requiring rigid setups, positive-rake carbide tools, slow speeds, and careful technique. The alloy can be cold-worked in the annealed state but requires re-solution treatment if heavily deformed before aging.

Welding of Monel K-500 Bar

Monel K-500 is weldable, but the process requires caution. Welding should only be performed in the solution-annealed condition. Post-weld heat treatment is critical and must include a full solution anneal followed by the standard aging cycle to restore corrosion resistance and mechanical properties in the heat-affected zone. Matching filler metals (e.g., ERNiCu-7) are used. Due to the complexity of post-weld heat treatment, welding is often avoided for critical high-strength components; mechanical fastening is preferred.

Reference Pricing and Key Purchasing Factors

The price of Monel K-500 bar from Shanghai NC Metal Materials Co., Ltd. reflects its higher alloying content (Al, Ti) and the additional processing involved in heat treatment compared to Monel 400.