US military military metal materials .(Monel)
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Look at the American war movies, such as the classic “Save the Great Ryan”, often see a metal card that must be carried by soldiers fighting each other. This small card can not be underestimated, not only represents his identity, but also is held by others. This means hanging, so the construction of this ID card is not ordinary steel, it is several times more expensive than stainless steel, highly corrosion-resistant Monel. This alloy, from small guitar strings to aerospace and nuclear weapons, allows us to unveil the veil of this alloy.
About Monel:
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Monel is a nickel-based alloy with a major chemical composition of up to 67% nickel (Ni). The other major chemical composition is copper (Cu), a small amount of iron (Fe), manganese (Mn) and carbon. (C), silicon (Si) and other elements.
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Monel is stronger than pure nickel and resists corrosion from a variety of media, including fast moving seawater. Monel is processed by hot working, cold working, machining and welding.
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In 1901, the international nickel company (INCO) metallurgist Robert Crooks Stanley created Monel.
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The source of the Monel alloy name was a tribute to the then chairman of the company, Ambrose Monel, who served as chairman of the International Nickel Corporation. Monel was patented in 1906.
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You may have noticed the lack of the letter L in the name because it is not allowed to use the last name as the registered brand name in this era. The Monel trademark is now owned by Special Metals Corporation.
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Monel is an expensive alloy that is 5 to 10 times more expensive than pure copper and pure nickel. Therefore, it is only used in applications that cannot be replaced with cheap alternatives.
Monel properties:
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Monel is a solid solution binary alloy. Since Ni and Cu are mutually solid solution, it is also a single phase alloy. Monel processing is difficult compared to steel, mainly due to its rapid work hardening characteristics. It needs to rotate at low speeds and low feed rates. -
The Monel400(UNS N04400) has a density of 8.80 gram/cm 3 , a melting temperature range of 1300 to 1350 ° C, an electrical conductivity of about 34% IACS (IACS refers to the internationally annealed copper standard conductivity), and an annealing hardness of 65 HRB. MonelAlloy 400 is known for its good toughness and maintains this toughness over a wide temperature range.
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It can withstand a variety of acid and alkali corrosion, and some Monel can even withstand pure oxygen combustion. It is commonly used in highly corrosive environments. The Monelalloy K-500(UNS N05500) formed by adding a small amount of aluminum (Al) and titanium (Ti) has the same corrosion resistance as Monelalloy 400, but has higher strength, which is mainly due to the formation of γ’s aging treatment stage. In general, Monelalloys are much more expensive than stainless steel.
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Although Monel400(UNS N04400) has increased strength and hardness, it still maintains excellent mechanical properties below zero, but the plasticity or toughness is only slightly lowered. Even in the cooling of liquid hydrogen, the alloy does not undergo a ductile-brittle transition, which is the most significant difference between Monel and low-temperature brittle iron materials (steel and iron).
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Monel has good corrosion resistance in many environments, but is prone to rust when exposed to salt water; it cannot withstand corrosion with nitric oxide, nitric acid, sulfur dioxide and hypochlorite media. Monelalloy may also undergo electrochemical corrosion . In other words, when aluminum, zinc or iron fasteners are in contact with Monel, in some cases (for example in fast flowing seawater), the metal fasteners will etch away quickly.
Application areas of Monel:
aerospace
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In the 1960s. Monel has received a large number of orders in the field of aerospace aircraft manufacturing. Particularly suitable for the construction of the fuselage and skin of experimental jets. For example, the North American X-15 can be used to withstand the large amounts of heat generated during aerodynamic friction during extreme flight. Monel maintains its strength at particularly high temperatures, maintaining a stable shape at high atmospheric flight speeds.
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In aircraft maintenance, Monel is used as a lock line in high temperature areas to ensure that the fasteners are locked; for economic reasons, other areas are usually made of stainless steel lock lines.
Oil recovery and refining
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Monel is used to make hydrocarbon fractions that are in direct contact with concentrated hydrofluoric acid. Monel’s excellent resistance to hydrofluoric acid corrosion is impressive. It can withstand all concentrations of hydrofluoric acid and can withstand temperatures up to the boiling point of hydrofluoric acid. This may be the best corrosion resistant material in commonly used engineered alloy materials. Monel is also resistant to corrosion by various sulfides and hydrochloric acids in a reducing environment.
Marine Engineering
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The corrosion resistance of Monelalloys makes it an ideal material for offshore applications such as piping systems, pump shafts, seawater valves, towline lines, and basket filters. Some Monelalloys are completely non-magnetic and are used in the manufacture of housings for anchors and magnetic field measuring devices for mine clearance. On the yacht, Monel wire is used to lock the anchor, Monel is also used in the manufacture of water tanks and fuel tanks and other underwater equipment such as propeller shafts and keel bolts.
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It is worth noting that it is important to isolate Monel from other metals (such as steel) during shipbuilding due to electrochemical corrosion (bimetallic corrosion) in seawater. The New York Times published on August 25, 1915. . An article about an accident in a 215-foot yacht: “The first hull made entirely of Monelalloy turned into a piece in just six weeks and was forced to scrap.” Due to electrochemical corrosion, the yacht The steel keel is quickly eroded after contact with Monel, eventually causing the bottom of the yacht to collapse.
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In the study of seabirds, especially in the selection of bird’s foot identification rings, the bird’s foot recognition ring made of Monel has been used in many species of seabirds, such as albatrosses living in corrosive seawater environments.
Musical instrument
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Monel is used to make certain high quality instrumentation valve pistons or rotors, such as small, large and French models. In 1962, RotoSound used Monelalloy to make electric guitar strings, which many artists use. In 2017, D’Adario Strings released a set of violin strings, which are also round-wound strings, winding Monelalloys around the D and G strings.
other
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ID card made with Monel (the dog tag of American soldiers during the Second World War). -
The ID card also lists the name and address of its wife below its information. The small “A” in the upper left corner represents blood type A, and the small “M” below it represents the size of the gas mask he uses.
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Excellent corrosion resistance to various acids and oxygen makes Monelalloy a high quality material for the chemical industry. Other usage scenarios such as:
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Uranium concentration, mostly used for large diameter uranium hexafluoride tubes made of Monel;
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High pressure and strong reactive bottled gas (such as HCl) regulating valve;
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At the beginning of the 20th century, Monel was widely used in the superheated steam system of steam generators;
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Monel is also often used to make kitchen sinks and frames;
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a combustion chamber for manufacturing a boiler ignition tube;
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The design life is 10,000 long clocks, no precious metals, and some parts of the clock are made of Monel based on corrosion problems.
