Monel Alloy Round Bars

Product Description

Monel alloys are nickel-copper solid-solution and precipitation-hardenable alloys engineered for extreme corrosion resistance and mechanical strength. Across international standards, the most widely specified round bar materials are Monel 400 (UNS N04400 / DIN Werkstoff Nr. 2.4360), Monel K-500 (UNS N05500 / DIN Werkstoff Nr. 2.4375), and free-machining Monel R-405 (UNS N04405 / DIN Werkstoff Nr. 2.4361).

Standards and Chemical Limits

Monel 400 and Monel R-405 are governed by ASTM B164 and ASME SB164 specifications, while Monel K-500 is governed by ASTM B865, ASME SB865, and AMS 4676 specifications. All three grades comply with NACE MR0175 and ISO 15156 standards for sour gas environments.

Chemically, Monel 400 contains a minimum of 63.0 percent nickel and 28.0 to 34.0 percent copper, with maximum impurity limits of 2.5 percent iron, 2.0 percent manganese, 0.50 percent silicon, 0.30 percent carbon, and 0.024 percent sulfur.

Monel R-405 matches this chemical baseline but intentionally adds 0.025 to 0.060 percent sulfur to enhance chip breaking during high-speed machining.

Monel K-500 modifies the base nickel-copper matrix by adding 2.30 to 3.15 percent aluminum and 0.35 to 0.85 percent titanium, with maximum limits of 2.0 percent iron, 1.5 percent manganese, 0.50 percent silicon, 0.25 percent carbon, and 0.01 percent sulfur.

Physical Characteristics

Monel 400 has a density of 8.80 grams per cubic centimeter (0.318 pounds per cubic inch), a melting range of 1300 to 1350 degrees Celsius, an elastic modulus of 179 gigapascals, and thermal conductivity of 21.8 watts per meter-kelvin. It is non-magnetic when fully annealed, though heavy cold work can raise its Curie point into the 20 to 50 degrees Celsius range, causing slight magnetic permeability at room temperature.

Monel K-500 has a slightly lower density of 8.44 grams per cubic centimeter (0.305 pounds per cubic inch), a melting range of 1315 to 1350 degrees Celsius, an elastic modulus of 179 gigapascals, and thermal conductivity of 17.5 watts per meter-kelvin. Monel K-500 remains non-magnetic down to cryogenic temperatures below minus 100 degrees Celsius.

Mechanical Properties and Thermal Conditions

Monel 400 and Monel R-405 cannot be hardened by heat treatment; their mechanical strength is developed solely through cold work. In the hot-finished or annealed state, Monel 400 bars exhibit a minimum tensile strength of 550 megapascals (80 ksi), a minimum 0.2 percent yield strength of 240 megapascals (35 ksi), a minimum elongation of 35 percent, and a typical hardness of 110 to 150 Brinell. Cold-drawn stress-relieved Monel 400 bars increase to a minimum tensile strength of 620 megapascals (90 ksi), a minimum yield strength of 415 megapascals (60 ksi), an elongation of 15 percent, and a hardness between 160 and 220 Brinell.

Monel K-500 gains superior strength through precipitation age-hardening heat treatments. In the solution-annealed condition, Monel K-500 displays a tensile strength of 620 to 760 megapascals (90 to 110 ksi), a yield strength of 275 to 415 megapascals (40 to 60 ksi), an elongation of 25 to 50 percent, and a hardness of 140 to 180 Brinell. Following precipitation age-hardening, gamma prime sub-microscopic particles form within the matrix, raising the minimum tensile strength to 965 to 1100 megapascals (140 to 160 ksi), minimum yield strength to 690 to 790 megapascals (100 to 115 ksi), elongation to 20 to 30 percent, and hardness to 28 to 35 Rockwell C (280 to 330 Brinell). Cold-drawn and aged Monel K-500 round bars reach tensile strengths up to 1310 megapascals (190 ksi), yield strengths up to 965 megapascals (140 ksi), and hardness levels up to 38 Rockwell C.