Monel Alloys: Grades, Properties & Supply

MONEL is a registered trademark of Special Metals Corporation. Sagiant Piping Industries is an independent supplier and stockist, not the alloy producer. Identify the exact UNS number, specification edition and condition on enquiry.

Producer limiting composition. Ni + Co is a combined quantity with a 63% minimum (no fixed upper limit). A dash means not separately specified, not zero. R-405 differs from 400 only by a controlled sulphur range for free machining. These are not heat analyses or a substitute for the purchase specification — the ordered specification edition and heat/product certificate control acceptance.

“Core” grades have completed technical records; “Reference” and “Historical” names are quoted until chemistry, form, specification and availability are confirmed — a listing is not a stock statement. Related boundary items are tracked separately: alloy 400L (N04402, VDM) is distinct from 400; welding consumables such as 60/67/190 belong in the welding section, not the base-alloy register; cast nickel-copper grades need their own casting specification. UNS cross-references are not substitution approvals.

Indicative values only; a figure valid for one diameter, condition or form can be misleading as a family minimum. Contractual minima, specification maxima and typical producer measurements are different datasets. Confirm grade, UNS, product form, manufacturing route, size interval, temper/heat treatment, specification edition and test method on the certificate. K-500 weld metal may not develop the strength of aged base material — treat joint performance separately. Elevated-temperature, fatigue, impact, creep and design-code allowable stresses are taken from the applicable code/specification, not derived from room-temperature tensile strength.

Split density by grade — a single family value misstates K-500 mass estimates; use the grade-specific density in the weight calculator. Melting ranges are not service temperatures. Thermal conductivity, specific heat, electrical resistivity, thermal-expansion coefficient (with its interval) and permeability with temperature/condition are provided per grade on enquiry. 400’s magnetic behaviour is temperature-dependent near room temperature, so it is not categorically “weakly magnetic”. R-405 may reference 400 for certain physical constants, but that does not make its mechanical or welding behaviour identical.

A routing matrix for specification review, not a universal certification. ASTM B165 covers N04400 seamless pipe/tube and B865 covers N05500 bar, rod, wire, forgings and forging stock. ASTM and ASME SB adoption editions are not automatically identical; legacy federal/aerospace/EN references are confirmed against current or contractually specified documents. Rename designation “equivalents” as cross-references — matching designations do not prove identical limits, heat treatment, dimensions or code acceptance.

Availability is confirmed per enquiry with stocked / sourced / made-to-order status — the ranges below are indicative, not a statement that every grade is held in every size, schedule and condition.

Class 2500 is a flange pressure class, not “2500 psi”, and B16.5 Class 2500 extends only to NPS 12. STD/XS do not always equal Sch 40/80, and 40S/80S differ from 40/80 at some sizes. Keep dimensional standards (B36.10 / B36.19) separate from material specifications. See the schedule chart and weight calculator.

• Seawater: 400 resists flowing seawater well, but performance depends on velocity, aeration, crevices, deposits and biofouling. K-500 shows different environmental-cracking behaviour from 400, and stagnant or slow-moving seawater conditions warrant specific review — a general marine statement is not unrestricted suitability.
• Hydrofluoric acid: resistance depends on HF concentration, water content, aeration and contaminants; suitability is condition-specific, not universal.
• Acids/alkalis: strong in reducing conditions and many alkalis; oxidising acids and oxidising species (for example ferric/cupric ions, aerated oxidising media) attack nickel-copper alloys — confirm with data.
• Sour service: qualification follows the applicable ISO 15156 / NACE MR0175 route with product condition, hardness and environment; high-strength aged K-500 needs particular attention. An MTC/PMI report does not establish it.
• Published corrosion rates require concentration, temperature, aeration, velocity, duration and method — avoid a single “excellent” rating across all conditions.

Temperature guidance distinguishes continuous/intermittent exposure, air versus process fluid, pressure/stress, thermal cycling and heat-treatment stability. “Useful to ~540°C” is not an allowable pressure-design temperature; hydrogen / cathodic-protection effects on aged K-500 need specialist review.