Select the main parts of the valve material, first of all, the work should take into account the physical properties of the medium (temperature, pressure) and chemical properties (corrosion resistance) and so on. At the same time should also be aware of the cleanliness of the media (with or without solid particles). In addition, the country would also like to refer to and use of sector-related regulations and requirements. Many types of valves in a variety of materials to meet the conditions of the use of different requirements. However, the correct, reasonable choice of material valve, the valve can be the life of the most economical and best performance. Valve parts in the division of materials, the most general method is used by the shell material into: such as cast iron valve, cast iron shell material can be made of malleable iron or ductile iron valve; steel valve, the shell with carbon steel, alloy steel or stainless steel made of acid-resistant flash; titanium valves, made of shell with titanium valves; copper valve, made of copper alloy shell with the valve; aluminum valve, shell with valve aluminum alloy system; plastic valves, plastic shell made of the valve; ceramic valve, ceramic shell valves lining there, and so on. 1, cast iron valve cast iron valve with its low cost, simple manufacturing process, better corrosion resistance, widely used in various sectors of the national economy is a channel, construction equipment, gas equipment, ships, fire-fighting equipment, petrochemical equipment, smelting Rail equipment, food processing equipment pipeline indispensable annex. Cast iron valve operating temperature range is usually from the environment (room temperature) below the temperature to 225 ℃. However, as the gray cast iron is a brittle material, limiting the use of cast iron valves. Valves in cast iron, because of malleable iron and cast iron ball change in the internal microstructure, the organization of malleable iron near the surface for the ferrite, the center for the pearlite, and mild steel similar to the organization. Nodular cast iron is to add elements and modification, and in the casting process to obtain spherical graphite, so its mechanical properties than ordinary gray cast iron are much better, the use of the working pressure may be higher. Typically, the use of cast iron valves are as follows: (1) When used for nominal pressure PN ≤ 1.0MPa, working temperature of -10 ~ 200 ℃, working media for the water, water, steam, air, gas, oil, etc. Grades are usually selected for HT200, HT250, HT300, HT350 gray cast iron valve. (2) When the nominal pressure for the PN ≤ 2.5MPa, working temperature of -30 ~ 300 ℃, working media for the water, water, steam, air, gas, oil, etc., are usually chosen for the brand KTH300-06, KTH330-08 , KTH350-10 of malleable iron valves. (3) When used for nominal pressure PN ≤ 4.0MPa, working temperature of -30 ~ 350 ℃, working media for the water, water, steam, air, gas, oil, etc., are usually chosen brand for the QT400-15, QT450-10 , QT500-7 iron valve. 2, steel valve as a result of the use of different types of steel, steel valves are also very different from the application of the medium, even though the price of steel valve is more expensive, but because steel is a kind of plastic material, the application of a wide range of media in a variety of applications , such as tungsten, saturated steam and hot steam, high temperature and low-temperature oil, liquefied gases, corrosive media, such as strong, so a wide range of applications. Carbon steel, due to its mechanical properties and the integrated use of performance, so its wider use, usually also includes a bronze cast iron valves and valve (-180 ℃ widely used in the following) the use of the working conditions. General in the important equipment, installations and pipelines on the soundness of the use of steel valves. In the media for the combustible gases, liquids, toxic gases, liquids, flammable and explosive medium, compressed gases, liquefied gases, power plant on the pipeline, and other similar occasions, must use steel valves. Special carbon steel and low-nickel alloy can be used to work at temperatures below the freezing conditions, but can not be used to the cryogenic region. These materials are manufactured valves, may be applied to water, carbon dioxide, acetylene, propylene and ethylene and other media. Corrosion-resistant steel, including stainless steel, special stainless steel, "Monel" alloy,哈斯特洛according to "B",哈斯特洛according to "C", acid-resistant stainless steel. Acid-resistant stainless steel valves can be widely used in chemical and food industries. Such as customs lose acetic acid, nitric acid, sulfuric acid, alkali, West bleach solution, food, fruit juice, carbonated, liquid leather and many other chemical products on the road of the tube. Acid-resistant ultra-low carbon austenitic stainless steel valves, typically used in low temperature liquid gas carrier, such as natural gas, methane, oxygen and hydrogen and so on. Special stainless steel valves have a very good corrosion resistance, usually used to transport a variety of temperature and concentration of sulfuric acid on the pipe and fittings. "Monel" alloy valves, mainly for transportation base, salt solution, food and many inorganic acid, especially sulfuric acid and hydrofluoric acid on the pipe and fittings. In addition, these valves can also be used for steam and water pipes. Nickel-valve, for the alkali and salt solution is highly corrosion-resistant, usually used in product transportation, the requirements to ensure that the condition of high purity. "Hastelloy" alloy valves, mainly for transport chloride, zinc chloride, aluminum sulfate, ammonium sulfate, hydrochloric acid and other strong corrosive medium on the pipe and fittings.
