Monel alloy for corrosion resistant valve
The current American technical standards of Monel alloy include ASTM, SAE, AMS, MII, ANSI, ASME. For Monel alloy of the same brand, different technical specification systems are adopted, not only the expression method of the brand is different, but also the code and content of the specification are not exactly the same.
Monel alloy is a Ni Cu solid solution, in which Cu is used as a non oxidizing corrosion inhibitor to improve the corrosion resistance of nickel alloy and strengthen the alloy. However, only 0.15% C can be dissolved in the alloy at room temperature, and the excess C will precipitate as graphite phase. The addition of 1.5% ～ 3.5% Fe can also improve the castability of the alloy. The addition of Mn and Si can improve the mechanical properties of the alloy, especially the content of Si has an important influence on the mechanical and physical properties of monel alloy.
Monel alloys can be divided into cast alloys and wrought alloys (rolled products).
Table of Contents
There are 10 kinds of deformed Monel alloys in America. Such as MONEL400, monelc, monel403, monel404, monel405, monel406, monel411, monelk500, monel501 and monel502. Because Monel has its own expression methods in different American standard systems, there are five kinds of deformed Monel alloys in UNS, including solution strengthened no4404 (MONEL400), no4404 (monel404) and no4405 (monelr-405), precipitation hardened no5500 (monelk500) and no5502 (mone1502) (Table 1). Among them, Monel 400 and Monel K500 are commonly used in the manufacture of corrosion-resistant valves.
Monel alloy pumps, valves and accessories for refining. However, the B-grade (3.5% Si) Monel alloy with high Si content is mainly used for manufacturing shafts and wear rings with good wear resistance due to its high strength, corrosion resistance and wear resistance. Class D (4.0% Si) Monel alloy is used to manufacture parts requiring higher wear resistance and corrosion resistance.
Monel alloy valve has two types: integral and internal.
Integral Monel alloy valve means that the shell and internals of the valve are monel, which is mainly used in HF acid regeneration tower of alkylation unit in refinery. Due to the high regeneration temperature (149 ℃) and high water content of HF acid, integral Monel alloy valve is needed. In addition, integral Monel alloy valve is also used in the production of ashless additive for catalyst in refinery and high concentration chlor alkali liquid system in chlor alkali plant.
Monel alloy trim valve means that the shell material of the valve is carbon steel or stainless steel, while the trim material of the valve is Monel alloy. Monel alloy valve with carbon steel as shell is mainly used in the low temperature area of HF acid system in refinery alkylation unit. It uses carbon steel to control anhydrous hydrofluoric acid at low temperature (≤ 71 ℃) (HF) has good corrosion resistance, but when carbon steel is used in this condition for a long time, it will form a film on its surface due to corrosion. If carbon steel is used in the sealing part of the valve, the film formed after corrosion will affect the sealing performance of the valve.
Cr13 type sealing material commonly used in carbon steel valve can not resist HF acid corrosion, and Monel alloy can ensure the sealing performance of the valve. Moreover, the cost of Monel alloy inner valve is much cheaper than that of integral Monel alloy valve. Monel alloy valve with carbon steel shell can also be used in seawater and other media. Monel alloy trim valve with stainless steel shell is used in ethylene, propylene, liquid oxygen, pure oxygen, seawater and other alloy conditions. For the integral Monel alloy valve and Monel alloy trim valve used in alkylation unit, from the safety point of view, it is required to select the pressure class cl300, and for Monel alloy trim valve used in other working conditions, the pressure classes are ci150 and ci300, or pn1.6 ~ 6.4Mpa, etc.
Source: China Valve Supplier: www.epowermetals.com
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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