Introduction
Monel K500 is a precipitation-hardenable nickel-copper alloy that combines the excellent corrosion resistance characteristic of Monel 400 with the added advantage of greater strength and hardness. These amplified properties, strength and hardness, are obtained by adding aluminum and titanium to the nickel-copper base and by a thermal processing used to effect precipitation, typically called age hardening or aging.
When in the age-hardened condition, Monel K-500 has a greater tendency toward stress-corrosion cracking in some environments than Monel 400. Alloy K-500 has approximately three times the yield strength and double the tensile strength when compared with alloy 400. Plus, it can be further strengthened by cold working prior to precipitation hardening. The strength of this nickel steel alloy is maintained to 1200° F but stays ductile and tough down to temperatures of 400° F. Its melting range is 2400-2460° F.
This nickel alloy is spark resistant and non-magnetic to -200° F. However, it is possible to develop a magnetic layer on the surface of the material during processing. Aluminum and copper may be selectively oxidized during heating, leaving a magnetic nickel rich film on the outside. Pickling or bright dipping in acid can remove this magnetic film and restore the non-magnetic properties.
Composition
| Element |
Min % |
Max % |
| Ni |
63.00 |
70.00 |
| Co |
- |
2.00 |
| Cu |
27.00 |
33.00 |
| Fe |
- |
2.00 |
| Al |
2.30 |
3.20 |
| C |
- |
0.25 |
| Si |
- |
1.00 |
| Mn |
- |
1.50 |
| Ti |
0.35 |
0.85 |
| S |
- |
0.01 |
| Grade |
UNS |
DIN |
EN |
AMS |
ASTM |
JIS |
| Monel K500 |
N05500 |
|
2.4375 |
|
ASTM B865
|
- |
Characteristic
Corrosion resistance in an extensive range of marine and chemical environments. From pure water to non-oxidizing mineral acids, salts and alkalis.
Excellent resistance to high velocity sea water
Resistant to a sour-gas environment
Excellent mechanical properties from sub-zero temperatures up to about 480C
Non-magnetic alloy
Mechanical & Physical Properties
| Property |
-200°C |
-157°C |
-130°C |
-70°C |
21.1°C |
100°C |
204.4°C |
315.6°C |
400°C |
537.8°C |
648.9°C |
| Ultimate Tensile Strength /MPa |
- |
- |
- |
- |
1100 |
1040 |
1020 |
980 |
890 |
750 |
620 |
| 0.2% Yield Strength /MPa |
- |
- |
- |
- |
690 |
670 |
640 |
620 |
600 |
570 |
490 |
| Elongation % |
- |
- |
- |
- |
24 |
- |
- |
- |
- |
- |
- |
| Coefficient of Thermal Expansion /µm/m°C |
11.2 |
11.7 |
12.2 |
13 |
13 |
13.7 |
14.6 |
14.9 |
15.3 |
15.7 |
16.4 |
| Thermal Conductivity /kcal/(hr.m.°C) |
- |
10.6 |
11.3 |
12.64 |
14.79 |
16.68 |
19.09 |
21.84 |
24.25 |
27 |
29.41 |
| Modulus of Elasticity / GPa |
- |
- |
- |
- |
179 |
- |
- |
- |
- |
- |
- |
Workability
Heat Treatment
Annealing is performed both for softening of the matrix after working and for solutioning of the age-hardening phase. Adequate softening may be achieved with temperatures as low as 1400-1600°F, but heating at 1800°F for hot-finished products and 1900°F for cold-drawn products is recommended for optimum response to subsequent age hardening. Grain growth becomes fairly rapid above 1800°F, and if a fine-grained structure is desired heating time should be kept to a minimum at these higher temperatures.
For optimum aging response and maximum softness, it is important to obtain an effective water quench from the heating temperature without delay. A dely in quenching or a slow quench can result in partial precipitation of the age-hardening phase and subsequent impairment of the aging response. Addition of about 2% by volume of alcohol to the water will minimize oxidation and facilitate pickling.
Machining
Heavy machining of alloy K-500 is best accomplished when the material is in the annealed condition or hot-worked and quenched condition. Age-hardened material, however, can be finish-machined to close tolerances and fine finished. The recommended practice, therefore, is to machine slightly oversize, age-harden, then finish to size. During aging, a slight permanent contraction (about 0.0002 in/in) takes place, but little warpage occurs because of the low temperatures and slow cooling rates involved.
Applications
Nickel alloy Monel K500 has many different industrial applications, some of which include:
- Pump shafts and impellers
- Doctor blades and scrapers
- Oil-well drill collars and instruments
- Electronic components
- Springs
- Valve trim
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