Monel alloy has high strength and toughness, and has excellent resistance to reducing acid and strong alkali medium and seawater. Therefore, it is commonly used in the manufacture of hydrofluoric acid (HF), brine, neutral medium and alkali salt. And reducing acid medium equipment, also suitable for drying hydrogen, hydrogen chloride, high temperature chlorine (425 ° C) and high temperature hydrogen chloride (450 ° C) and other media, but not resistant to sulfur and oxidizing media (such as nitric acid, oxygen content Corrosion of high medium), because nickel reacts violently with sulfur and oxygen, it is easy to form Ni3S2 and NiO.
Monel alloys are available in both cast and deformed alloys. 1. Monel alloy deformed alloy There are 10 kinds of deformed Monel alloys in the United States, and there are different representation methods in different American standard systems. There are two kinds of deformed alloys commonly used in the manufacture of corrosion resistant valves: solid solution strengthening type MONEL400 (UNS N04400) and Precipitation hardening type MONEL K500 (UNS-NO5500).
Monel400 alloy is a high-strength single-phase austenite, which is the most used, most versatile, and comprehensive corrosion-resistant alloy. The alloy has excellent corrosion resistance in hydrofluoric acid and fluorine gas media, and excellent corrosion resistance to hot alkali liquor. At the same time, it is also resistant to corrosion of neutral solutions, water, sea water, atmosphere, organic compounds, etc. Another important feature of this alloy is that it does not generally produce stress corrosion cracks and has good machinability.
Monel K500, the alloy has the same chemical composition as 400, the biggest difference is Al2.3-3.15%, Ti0.35-0.85%. The precipitation strengthening phase in the Monel K500 alloy is an intermetallic compound Ni3 (Al, Ti) which precipitates when the solution annealed alloy is heated to about 1100F (594 ° C). In addition to the same corrosion resistance as Monel400 (Monel K500 is fully applicable to Monel K500), Monel K500 (UNS N05500) has high strength and non-magnetic properties, and because the alloy has no plastic-brittle transition temperature, it is very Suitable for the manufacture of various cryogenic equipment, welding can increase the strength of the alloy, but reduce the plasticity of the alloy.
Monel casting alloys are available in five grades in the A494 standard, but are primarily used on valves for the M35-1.
Casting alloy M35-1 chemical composition %