Material Family

Nickel-Copper Alloy (Free-Machining, Sulfur-Bearing)

The free-machining version of Monel 400 bar stock.

Distinguishing Feature

Enhanced Machinability for high-speed automatic screw machine and CNC lathe operations.

This is the primary reason to specify R-405 over standard Monel 400 bar for machined parts.

Common Forms (Bar)

Cold Drawn or Hot Rolled Rounds, Hexagons, Squares. Also supplied as Wire Rod for screw machining.

Typically supplied as cold drawn rounds for precision machining with excellent surface finish.

Chemical Composition (Typical wt.%)

Ni: ≥ 63.0 (Balance)
Cu: 28.0 - 34.0
Fe: 2.5 max
Mn: 2.0 max
C: ≤ 0.30
Si: ≤ 0.50
S: 0.025 - 0.060

The key difference from Monel 400 is the intentional addition of Sulfur (S). This forms manganese sulfide inclusions that act as chip breakers, enabling smooth, fast machining.

Mechanical Properties (Cold Drawn, Room Temp)

Tensile Strength (Rm): 550 - 860 MPa
Yield Strength (Rp0.2): 240 - 690 MPa
Elongation (A): 15 - 35% (varies with temper)

Can be supplied in various cold worked tempers (e.g., 1/4 Hard, 1/2 Hard, Full Hard) to achieve specific strength levels post-machining.

Physical Properties

Density: 8.80 g/cm³
Melting Range: 1300 - 1350 °C

Identical to Monel 400.

Machinability Rating

Excellent. Typically rated at 70% on the free-machining brass scale (where 100% is C36000 brass). Similar machinability to free-machining stainless steel 303.

Allows for high production speeds, excellent surface finish, and extended tool life compared to Monel 400.

Corrosion Performance Note

The sulfur addition can marginally decrease corrosion resistance in certain severe, hot acid environments and slightly reduce ductility compared to low-sulfur Monel 400. Performance in seawater and most typical marine/chemical applications remains excellent.

For critical welded structures or the most severe HF service, Monel 400 bar is preferred. For machined parts, R-405 is standard.

Key Standards (Bar)

ASTM B164 / ASME SB-164 (Standard Specification for Nickel-Copper Alloy Rod and Bar - Grade UNS N04405)

The sulfur-controlled chemistry (UNS N04405) is the critical procurement requirement.

Weldability

Not recommended for welding. The sulfur content increases the risk of hot cracking in the weld zone.

For welded assemblies, fabricate from Monel 400 bar and machine components from R-405 bar separately.

Typical Bar Applications

• Mass-produced Fasteners: Screws, nuts, bolts, studs, washers for marine and chemical applications.
• Valve Components: Stems, seats, bushings, fittings, plugs.
• Pump & Shaft Components: Sleeves, shafts, impeller nuts, small gears.
• Electrical & Connector Parts: Terminals, contacts, spacers.
• General Machined Parts for seawater systems.

The dominant bar material for corrosion-resistant, free-machining components where Monel 400's base properties are required.