Inconel625 and Monel400

I. Inconel – a nickel-chromium-iron heat-resistant and corrosion-resistant alloy. Inconel is a registered trademark of the International Nickel Co. The INCONEL nickel-chromium alloy is an austenitic superheat-resistant alloy with nickel as its main component. Due to the solid solution strengthening effect of molybdenum and niobium contained in nickel-chromium alloys, it exhibits ultra-high strength and excellent fatigue resistance in the temperature range from low temperatures up to 1093°C. It is widely used in the aviation industry, and is suitable for manufacturing oxidation-resistant components that are subjected to low loads at temperatures below 1100°C. 　 　　It exhibits high tensile strength, fatigue strength, creep resistance, and fracture strength at 700°C; it has high oxidation resistance at 1000°C, stable chemical properties at low temperatures, good weldability, and ease of machining. Although this alloy was designed to provide strength in high-temperature environments, its high content of chromium and molybdenum confers excellent corrosion resistance against a wide range of corrosive agents, from highly oxidizing environments to normal corrosion conditions, giving it outstanding corrosion-resistant properties. It also exhibits exceptional corrosion resistance against media contaminated with chlorides such as seawater, geothermal water, neutral salts, and brine. At the same time, this alloy possesses high formability and is easier to weld than many nickel-based alloys. Under welded conditions, this alloy still retains its resistance to intergranular corrosion. It exhibits good tensile and fatigue properties from low temperatures up to 980°C, as well as resistance to stress corrosion in salt spray atmospheres. It can be used as components for aeroengine parts, jet engine components, aerospace structural parts, chemical processing equipment, bellows expansion joints, modern waste treatment equipment, in applications where it is exposed to seawater and subject to high mechanical stresses, for marine structures, and in saline environments. Chemical composition: (Examples) Inconel 625 – Ni (62%)–Cr (23%)–Mo (9%); Inconel 718 – Ni (55%)–Cr (21%)–Mo (2.8%). II. MONEL alloys MONEL is a registered trademark of Special Metals Corporation in the United States. MONEL alloy products possess excellent physical properties such as high strength, high corrosion resistance, and wear resistance. In various acidic and alkaline media, it boasts a long service life, which enables its widespread use in advanced industries such as petrochemicals, the nuclear industry, and the defense industry. Monel alloy is a Ni-Cu-based corrosion-resistant alloy; there are two types: work-hardening type, which includes grades such as Monel-400, 404, and R405 ； Precipitation-hardening type, including grades such as Monel K-500 and 502; Monel 400 and K-500 are commonly used. The mechanical properties of Monel K-500 are superior to those of Monel 400, but its corrosion resistance is slightly lower. 　　 Monel-400 is a single-phase austenitic alloy that is a Ni-Cu solid solution, featuring excellent corrosion resistance and strength at moderate temperatures; it particularly demonstrates good corrosion resistance in strong acids and strong bases at medium to high temperatures. Therefore, in recent years, this alloy has been increasingly used in China for the manufacturing of certain special equipment in industries such as petrochemicals and nuclear energy. Monel alloy exhibits excellent resistance to corrosion in reducing media; it maintains good stability in many corrosive substances such as hydrofluoric acid, alkalis, seawater, H2S, H2SO4, H3PO4, and organic acids. Its stability in hydrofluoric acid and alkaline solutions is particularly outstanding, second only to that of platinum and silver. The alloy has a certain sensitivity to SCC, with an operating temperature of <200°C. 　 The Monel 400 copper-nickel alloy exhibits high strength over a wide temperature range (up to 1000F). Springs made of Monel 400 can be used in corrosive environments at temperatures up to 450F. This alloy performs excellently in high-concentration saline environments. 　 Monel alloy can be used as corrosion-resistant components, elastic sensing elements, and protective tubes for corrosion-resistant thermocouples (operating temperature < 500°C). It is not recommended for use in oxidizing corrosive media.

This post was last edited by *aosh3242 on 2014-12-31 09:49. Basic requirements for the instrument control system of gasification furnaces: Multi-nozzle opposed water-coal slurry gasification furnaces have high demands on their automatic control systems; both operation and control must be carried out using advanced ESD systems and DCS systems. From the perspective of system safety, logical control is handled by an independent ESD system, while loop control is handled by the DCS system. The multi-nozzle opposed water-coal slurry gasification system relies heavily on the instrument control system, requiring high accuracy, stability, and controllability from the on-site instruments, automatic control valves, and control systems, as well as a range of additional functions. On-site instruments and valves are mostly equipped with process media such as gray water, black water, coal slurry – which are highly erosive and prone to deposition – as well as oxygen-based media; such media place special demands on the performance and quality of the instruments. (1) Black water medium: Black water media contain a high level of fine particulate suspended matter, which tends to settle. This leads to severe erosion of valves and throttling devices, and it can also cause blockages in these valves and pipes at the throttling points. Therefore, eccentric rotary valves or ball valves are generally used for such applications. Hard chromium is welded onto the valve cores, seats, and areas subject to erosion, in order to prevent erosion and blockages ； For level transmitters, remote differential pressure transmitters are used; the thickness of the diaphragm is increased, the diameter of the pressure tapping pipes is enlarged, and the flow rate of the flushing water is increased in order to prevent clogging and damage to the instruments ； Flow meters use throttling devices such as Venturi tubes or wedge flow meters, which have low resistance and are less prone to clogging; they are also treated to be wear-resistant. Measures such as enlarging the diameter of the pressure tapping pipes and installing flushing water are taken, in addition to the use of flanged remote-transmission meters. (2) Slurry medium: The coal concentration in the slurry medium is generally 60–65% (wt). In areas prone to drying and clogging, insert-type level transmitters are used for level measurement, while electromagnetic flow meters are employed for flow measurement. The valves used are ball valves coated, sprayed, or cladded with cemented carbide. (3) Greywater medium: Greywater is a medium with fewer particles, as the suspended solids in blackwater have settled. Compared to black water media, the requirements for instruments and valves are slightly lower, but it still possesses abrasive and corrosive properties. Pressure and differential pressure instruments for graywater (including blackwater and coal slurry) media use corrosion-resistant materials such as Hastelloy C for their measuring diaphragms. (4) Oxygen medium: The oxygen purity in such a medium is generally above 98%, and very high requirements are placed on the cleanliness of the pipes and throttling components (absence of any fatty or other flammable substances), their surface finish, and their electrical conductivity ； At the same time, there are also high requirements regarding the material of the valve, the selection of sealing materials, the treatment of the internal cavity, and the leakage rate. Valves and throttling elements are typically made of Monel 400 or Inconel 600/Inconel 625, while measuring instruments and pressure transfer tubes are made of 316L material and are treated for fire resistance and passivation.

Requirements for the selection of automatic control valves in gasification furnaces I. Slurry valves Slurry valves refer to the slurry shut-off valves and slurry circulation valves for each burner. The basic requirements for the valve are: a hard-sealed ball valve with a sealing grade of no less than Class V ； Hard alloy surfacing on valve balls and valve seats ； Valve actuation time

625 has a high hardness; the difference in hardness between the two is 100 Hb