A Comprehensive Guide to Nickel-based Alloy: Monel K-500 (UNS N05500)

What is Monel K-500?

Monel K-500 (UNS N05500/DIN W.Nr. 2.4375/Alloy K-500) is a kind of corrosion resistance with the largest amount, the most extensive use and excellent comprehensive performance alloy. The alloy has excellent corrosion resistance in hydrofluoric acid and fluorine gas medium, as well as in hot concentrated alkali solution. Monel K-500 (UNS N05500) is mainly composed of 30% Cu and 63% Ni with a small amount of Fe (1% – 2%), compared with Monel 400, Al and Ti are added.
Monel K-500 is suitable for working under the geological exploitation conditions of high sulfur and high wax reservoirs. Since the alloy has no plastic brittle transition temperature, it is very suitable for all kinds of low temperature equipment. Monel K-500 alloy not only has excellent mechanical properties such as high strength, corrosion resistance and non-magnetic, but also has the same corrosion resistance as Monel 400. It can be used as pump shaft material.

ASTM B865 Monel K-500 Forged Elbow 1″ 3000#

Chemical Composition of Monel K-500 (UNS N05500)

C	Ni	Fe	Cu	Ti	Al	Mn	S	Si
≤0.25	≥63.0	≤2.0	27.0-33.0	0.35-0.85	2.30-3.15	≤1.5	≤0.01	≤0.5

Physical Properties of Monel K-500 (UNS N05500)

Density	Melting Range	Specific Heat		Electrical Resistivity
g/cm3	°F	J/kg.k	Btu/lb. °F	µΩ·m
8.44	2400-2460	419	0.100	615

Mechanical Properties of Monel K-500 (UNS N05500)

Tensile Strength, min.		Yield Strength, min.		Elongation, min.	Hardness, min.
Mpa	ksi	Mpa	ksi	%	HB
1100	160	790	115	20	300

The main features of Monel 500

Monel 500 is a nickel copper alloy with the following main characteristics:

The machinability of Monel K-500

The best machinability of this alloy is annealed. It can be processed in the aging state, but the best way is to be as close to finishing as possible in the annealed state. Then aging and final processing are carried out. A very slight shrinkage in size occurs during aging. In general, the processing of this alloy in the annealed state is similar to that of austenitic (300 Series) stainless steel.
Nickel and cobalt based corrosion, temperature and wear resistant alloys, such as Monel K500, are classified as moderate to difficult in machining, but it should be emphasized that these alloys can be processed at a satisfactory rate using conventional production methods. During machining, these alloys work hardening rapidly, generate high heat during cutting, weld to the tool surface, and have high resistance to metal removal due to their high shear strength.

Forming of Monel K-500

• The alloy has good ductility and is readily formed in the annealed condition by standard means.

Welding of Monel K-500

• All of the conventional welding techniques may be used on this alloy. However it is best to weld with the alloy in the annealed condition and the finished weldment should then be stress-relief annealed. Exposure to temperatures in the age-hardening range (900 F to 1100 F) should be avoided except when the final age-hardening treatment is to be accomplished.

Hot working of Monel K-500

• The hot work temperature range is 2100 F to 1600 F. Water quench immediately after hot working and do not allow to cool below 1600 F.

Cold working of Monel K-500

• The alloy has good ductility and may be cold worked by standard means.

Aging of Monel K-500

•  For annealed, or slightly cold-worked, material age-hardening is done at 1125 F for 16 hours and then furnace cooling at a rate of 15 F to 25 F per hour down to a temperature of 900 F. Cooling rate from 900 F to room temperature is not critical. For severely cold-worked material aging should be done at 1000 F for at least 6 hours and then furnace cooled to 900 F at the 15 F to 25 F per hour rate.

Annealing of Monel K-500

• Anneal at 1900 F and water quench.

Heat Treatment of Monel K-500

• The alloy may be annealed after cold working and also may be precipitation-hardened by an aging heat treatment.

Application areas of nickel-based alloy Monel K-500 (UNS N05500)

An Alloy K-500 90DEG Elbow 3″ SCH80S extruded from the UNS N05500 seamless pipe.

Monel K500 has the advantages of high strength and corrosion resistance. Its typical applications are pump shaft, impeller, propeller shaft, valve components of ship and offshore drilling tower, bolt connection, oil well drill collar and instrument components of oil and gas production. Due to its high strength and low corrosion rate in high-speed seawater, it is especially suitable for centrifugal pumps in marine industry.

Monel K-500 (UNS N05500) nickel base alloy has the same corrosion resistance as alloy 400, but has higher mechanical strength and hardness. It has good thermal corrosion resistance and long-term structural stability. It is mainly used to manufacture turbine blades and gas turbine blades with working temperature below 750 ℃ on aeroengines, fasteners and springs on ships, pump and valve parts on chemical equipment, and scraping blades on paper-making equipment.
Monel K500 is nonmagnetic. Monel K500 should be annealed during welding and then stress relieved before aging. Some of the more common uses of Monel K-500 include:

• Wire wound resistors.
• Bimetal contacts.
• Electric and electronic applications.
• Marine engineering.
• Chemical and hydrocarbon processing equipment.
• Gasoline and freshwater tanks.
• Crude petroleum stills.
• De-aerating heaters.
• Boiler feed water heaters and other heat exchangers.
• Pumps, shafts and fasteners.
• Industrial heat exchangers.
• Chlorinated solvents.
• Crude oil distillation towers.
• Meter and valve parts.
• Screw machine products.
• Oil refinery piping.
• Heat exchangers.
• Nuclear fuel production.
• Generator tubing.
• High temperature heating coils.
• Crude oil transfer piping.
• Propeller and pump shafts.
• Piping system.
• Heat exchange tubes.
• Pipe fittings.
• Flanges.
• Forgings.

Variety specifications and supply status of Nickel-based super alloy: Monel K-500 (UNS N05500)

Variety classification:

Yaang Pipe Industry can produce various specifications of Monel K-500 seamless pipe, Monel K-500 steel plate, Monel K-500 round bar, Monel K-500 forgings, Monel K-500 flange, Monel K-500 pipe fittings, Monel K-500 welded pipe, Monel K-500 steel strip, Monel K-500 wire and supporting welding materials. 

Delivery status:

• Seamless pipe: solid solution + acid white, length can be set;
• Plate: solid solution, pickling, trimming;
• Welded pipe: solid solution acid white + RT% flaw detection;
• Forging: annealing + car polish; Bars are forged and rolled, surface polished or car polished;
• Strips are delivered after cold rolling, solid solution soft state, and deoxidized;
• Wire rods are finely ground in solid solution pickled disk or straight strips, solid solution straight strips Delivery in light state.

Heating Performance Test of Monel K-500 Alloy

In response to the current problems in the hot working production of Monel K-500 alloy in China, experimental tests were conducted on its heating performance using different heating rates. The research results indicate that when a relatively fast heating rate is used, there is no obvious overburning phenomenon on the surface of the casting billet, and the overall heating time is short. Therefore, using a faster heating rate for Monel K-500 alloy casting billet can effectively improve production efficiency.

Monel K-500 alloy is an important nickel-based corrosion-resistant material with excellent comprehensive properties. Compared with ordinary stainless steel, other corrosion-resistant metals, and non-metallic materials, it can withstand various forms of corrosion damage (including comprehensive corrosion, local corrosion, and stress corrosion) in various corrosive environments (including electrochemical corrosion and chemical corrosion), and has excellent mechanical and processing properties. It has been widely used in aviation, navigation, and petroleum engineering both domestically and internationally. Monel K-500 alloy is a high-temperature sensitive material, and its properties are greatly affected by the heating system and hot working process. At present, the hot working process of Monel K-500 alloy, especially the heating process, has yet to form a stable production process in China. In order to gain a deeper understanding and mastery of the heating performance of Monel K-500 alloy and to provide a basis for establishing a reasonable and practical hot working process, the heating performance of Monel K-500 alloy was tested to obtain a reasonable heating system, improve production efficiency, and save production costs.

1. Test plan

1.1 Test specimens
Adopt ϕ 136mm × ϕ 165mm × 550mm Monel K-500 alloy casting billet provided by a factory in Tianjin. For the convenience of testing, the billet was sawn into 2 sections, and the dimensions of the part used for testing were ϕ 150mm × ϕ 165mm × 300mm. Test the heating system of the sample at different heating speeds and holding times using an SX-75-16 resistance heating furnace under different temperature conditions, and record the test data using a paperless recorder.
1.2 Thermocouple installation position
Five thermocouples are installed on the same circumference at distances of 15,30,45,60,75mm from the surface of the casting billet, as shown in Figure 1.

Figure.1 Installation Position of Test Piece and Thermocouple
1.3 Heating conditions
The target heating temperature is 1150 ℃. Three different heating rates were used, namely 20,15,10 ℃/min. To ensure the safety of the heating furnace, regardless of the heating rate used, the heating rate for the first 300 ℃ of the furnace temperature is 10 ℃/min.

2. Test data and analysis

2.1 The heating rate is 20 ℃/min
The heating curve is shown in Figure 2.

Figure.2 Heating curve at a heating rate of 20 ℃/min
After about 68 minutes of heating, the furnace temperature reached 1150 ℃, and after about 187 minutes of insulation time, the temperature inside and outside the casting billet basically reached uniformity, with a total heating time of 255 minutes. There is a relatively thin oxide layer on the surface of the billet, and there is no overburning phenomenon, as shown in Figure 3.

Figure.3 Surface state at a heating rate of 20 ℃/min
2.2 Heating rate of 15 ℃/min
The heating curve is shown in Figure 4.

Figure.4 Heating curve at a heating rate of 15 ℃/min
After about 86 minutes of heating the furnace temperature to 1150 ℃, and after about 174 minutes of holding time, the temperature inside and outside the billet has basically reached uniformity, with a total heating time of 260 minutes. There is a relatively thin oxide layer on the surface of the billet, and there is no overburning phenomenon, as shown in Figure 5.

Figure.5 Surface state at a heating rate of 15 ℃/min
2.3 Heating rate of 10 ℃/min
The heating curve is shown in Figure 6.

Figure.6 Heating curve at a heating rate of 10 ℃/min
After approximately 117 minutes of heating, the furnace temperature reached 1150 ℃. After approximately 158 minutes of holding time, the internal and external temperatures of the casting billet were basically uniform, with a total heating time of 275 minutes. There is a thick oxide layer on the surface of the billet, and there is no overburning phenomenon, as shown in Figure 7.

Figure.7 Surface state at a heating rate of 10 ℃/min

3. Conclusion

• 1) There is no obvious overburning phenomenon on the surface of the slab when heated at three different heating rates. Therefore, the Monel K-500 alloy slab can be heated at a faster heating rate. 
• 2) When the heating speed is faster, the corresponding holding time will be longer, but the total heating time is shorter; 
• 3) Tests show that the Monel K-500 alloy slab with the size of Φ136mm × Φ165mm × 550mm can effectively improve the production efficiency by using a faster heating rate. 
• 4) The surface overburning phenomenon in the actual production process may be related to the structure of the heating furnace and the heating conditions. If the slab is heated unevenly during the heating process, it may lead to local overheating and overheating melting. In order to solve such problems, it is necessary to improve the heating conditions of the heating furnace so that the slab can be heated evenly during the heating process and the overburning can be eliminated.

Author: Zhang Xiaoping