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Valve material selection recommendations

Selection of the main parts of the valve material, the first should take into account the physical properties of the working medium (temperature, pressure) and chemical properties (corrosive) and so on. Also be aware of the degree of cleanliness of the media (with or without solid particles). In addition, we must also refer to the relevant provisions and requirements of the State and the use of the department.
Many kinds of materials can meet the requirements of the valve in a variety of different conditions. However, the correct, reasonable choice of valve material, you can get the most economical life of the valve and the best performance.
In the division of the valve part material, the most common method is to use the material used in the shell: such as cast iron valve, shell material with gray cast iron, malleable cast iron or ductile iron made of valves; Steel, alloy steel or stainless steel made of stainless steel; titanium valve, shell made of titanium alloy valve; copper valve, shell made of copper alloy valve; aluminum valve, shell made of aluminum Valves; plastic valves, shells made of plastic valves; ceramic valves, housings lined with ceramic valves, and so on.

1, cast iron valve
Cast iron valve with its low price, simple manufacturing process, good corrosion resistance, widely used in various sectors of the national economy, waterways, construction equipment, gas equipment, ships, fire equipment, petrochemical equipment, iron equipment, food Processing equipment and other indispensable pipe accessories. The operating temperature range of the cast iron valve is usually from ambient (room temperature) to below 225 ° C. However, due to gray cast iron is a brittle material, limiting the use of cast iron valve range.
In the cast iron valve, due to malleable cast iron and cast iron within the microstructure changes, malleable cast iron near the surface of the ferrite, the center of the pearlite, and soft steel is roughly the same organization. Ductile iron is added by adding elements and metamorphic treatment, and in the casting process to obtain spherical graphite, therefore, its mechanical properties than ordinary gray cast iron is much better, the use of work pressure can be higher.
In general, the use of cast iron valves is defined as follows:
(1) When used for nominal pressure PN ≤ 1.0MPa, the working temperature is -10 ~ 200 ℃, the working medium is water, sea water, steam, air, gas, oil, etc., usually selected grades HT200, HT250, HT300, HT350 Gray cast iron valve.
(2) When used for nominal pressure PN ≤ 2.5MPa, the working temperature is -30 ~ 300 ℃, the working medium is water, sea water, steam, air, gas, oil, etc., usually selected grades KTH300-06, KTH330-08 , KTH350-10 malleable cast iron valve.
(3) When used for nominal pressure PN ≤ 4.0MPa, the working temperature is -30 ~ 350 ℃, the working medium is water, sea water, steam, air, gas, oil, etc., usually selected grades QT400-15, QT450-10 , QT500-7 ductile iron valve.

2, steel valve
Due to the different types of steel, steel valves are also very different medium, although the price of steel valves are more expensive,
but because steel is a plastic material, for a wide range, which can be used in a variety of media, such as tungsten, Saturated steam and
hot steam, high temperature and low temperature oil, liquefied gas, corrosive media, etc., so the application is very extensive.
Carbon steel, due to its excellent mechanical properties and comprehensive performance, so its use of a wider range, usually also includes cast iron valves and bronze valves (widely used in -180 ℃ below) the use of working conditions. Generally in the important equipment, devices and pipes are used solid and reliable steel valves. Steel valves must be used for pipes with combustible gases, liquids, toxic gases, liquids, flammable and explosive media, compressed gases, liquefied gases, power plants, and other similar applications.
Special steel and low nickel alloy steel can be used for operating temperature below zero, but can not be used to the deep cold area. Valves made with these materials may be suitable for use in seawater, carbon dioxide, acetylene, propylene and ethylene.
Corrosion resistant steel includes stainless steel, special stainless steel, "Monel" alloy, Hastelloy "B", Hastelloy "C", stainless steel and so on.
Stainless steel acid-resistant steel valves can be widely used in chemical and food industries. Such as acetic acid, nitric acid, sulfuric acid, alkali, West bleach, food, fruit juice, carbonic acid, tanning fluid and many other chemical products on the pipeline. Ultra-low carbon austenitic stainless acid resistant steel valves are commonly used to deliver liquid gases at low temperatures, such as natural gas, biogas, oxygen and hydrogen. Special stainless steel valves have good corrosion resistance and are commonly used to deliver various temperatures and concentrations of sulfuric acid on pipes and devices. "Monel" alloy valves are mainly used for conveying alkali, salt solutions, food and many inorganic acids, especially sulfuric acid and hydrofluoric acid on pipelines and devices. In addition, this type of valve can also be used for steam and sea water pipes. Nickel valve, for alkaline and salt solution has a strong corrosion resistance, usually used in product delivery, to ensure high purity conditions. "Hastelloy" alloy valve, mainly used for conveying ammonium chloride, zinc chloride, aluminum sulfate, ammonium sulfate, hydrochloric acid and other corrosive media pipes and devices.
Corrosion-resistant materials made of the valve, due to the complexity of the process, expensive, therefore, in the selection, there should be sufficient basis in order to obtain the most economical use of the price even.
In general, the use of various steel valves is defined as follows:
(1) for the nominal pressure PN ≤ 32.00MPa, the working temperature of -30 ~ 450 ℃, the working medium for water, steam, air, ammonia, hydrogen, nitrogen and petroleum products, usually selected grades WCA, WCB, WCC Carbon steel; grades of 20,25,30,35 of high-quality carbon structural steel forgings; or grades of 16Mn low-alloy structural steel forgings.
(2) for the working pressure PN ≤ 17.00MPa, the working temperature is less than or equal to 550 ℃, the working medium for the steam and petroleum products, usually selected for the grade ZG15Cr5Mo chrome molybdenum steel castings; grades ZG20Cr1Mo1V, ZG15Cr1Mo1V chrome molybdenum vanadium steel Castings; grade 1Cr5Mo chrome molybdenum steel forgings, or grades 12Cr1Mo1V, 12Cr1Mo1VA chrome molybdenum vanadium steel forgings.
(3) for the nominal pressure PN ≤ 6.4MPa, the working temperature at or equal to -196 ℃, the working medium for ethylene, propylene, liquid natural gas and liquid nitrogen. Commonly used grades ZG0Cr18Ni19, ZG1Cr18Ni9Ti, ZG1Cr18Ni9Ti austenitic stainless steel steel castings, or grade 0Cr18Ni9,1Cr18Ni9, 00Cr18Ni9Ti austenitic stainless steel steel forgings.
(4) for the nominal pressure PN ≤ 6.4MPa, the working temperature is less than or equal to 200 ℃, the working medium for nitric acid, etc., usually selected grades ZG0Cr18Ni9, ZGCr18Ni9, ZG0Cr18Ni9Ti, and ZG1Cr18Ni9Ti austenitic stainless steel steel castings, grades 0Cr18Ni9 , 1Cr18Ni9,0Cr18Ni9Ti, 1Cr18Ni9Ti austenitic stainless steel steel forgings.
(5) for the nominal pressure PN ≤ 6.4MPa, the working temperature is less than or equal to 200 ℃, the working medium for acetic acid, etc., usually selected grades ZG0Cr18Ni12Mo2Ti, austenitic stainless steel steel castings, grades 0Cr18Ni12Mo2Ti, 1Cr18Ni12Mo3Ti austenite Stainless steel resistant steel forgings.
Many brands of steel used in the manufacture of valves, procurement personnel in the choice of valves, should be based on working conditions, a reasonable choice of different materials, valves.
3, non-ferrous metals and their alloy valves
Non-ferrous metals and their alloys include copper alloys, aluminum alloys, and titanium and titanium alloys. Titanium and titanium alloy valves are suitable for corrosive media and valves with special requirements.
(1) copper alloy valve: for the nominal pressure PN ≤ 2.5MPa of water, sea water, oxygen, air, oil and other media. When the working temperature of -40 ~ 250 ℃ steam, often used for grades ZCuSn3Zn11Pb4, ZCuSn10Zn2 cast bronze; grades H62, HPb59-1 brass; grades QA19-2, QA19-4 aluminum bronze.
(2) aluminum alloy valve: for the nominal pressure PN ≤ 1.0MPa corrosive media conditions, commonly used brands ZL7, ZL10.
(3) titanium and titanium alloy valve: industrial titanium and titanium alloy has good corrosion resistance, its relative density is small, high strength, low temperature and high temperature performance are more stable, is a good corrosion-resistant valve. However, due to the relatively high cost of titanium and titanium alloy valve, casting process is not good, only the current high-pressure valve factory in Xi'an production.
4, plastic valves, ceramic valves
Both valves are nonmetallic valves. Non-metallic materials, the biggest feature of the valve is strong corrosion resistance, and even metal materials can not have the advantages of the valve. Non-metallic materials, more varieties of the valve, its performance is also very different, generally used for nominal pressure PN ≤ 1.6MPa, the working temperature does not exceed 60 ℃ corrosive media.