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07
2022
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04
What are the main valve body materials?
Common valve body materials mainly include gray cast iron, black heart malleable cast iron, ductile iron, carbon steel, low-temperature carbon steel, and alloy steel. 1. Gray cast iron is a type of cast iron. It exists in cast iron in the form of carbon flake graphite. The fracture is gray. It has good casting and cutting performance and good wear resistance. It is used to manufacture shelves, boxes, etc.
Common valve body materials mainly include gray cast iron, black heart malleable cast iron, ductile iron, carbon steel, low-temperature carbon steel, and alloy steel.
1. Gray cast iron is a type of cast iron. It exists in the form of carbon flake graphite in cast iron. The fracture is gray. It has good casting and cutting performance and good wear resistance. It is used to manufacture shelves, boxes, etc. The graphite in gray cast iron is flaky, and its effective bearing area is relatively small. Stress concentration is likely to occur in the graphite, so the strength, plasticity, and toughness of gray cast iron are lower than those of other cast irons. However, it has excellent vibration damping, low notch sensitivity, and high wear resistance. It is suitable for low-pressure valves with a working temperature between -15℃ and +200℃ and a nominal pressure of PN≤1.6MPa.
2. Black heart malleable cast iron refers to parts with a certain impact and good strength, suitable for working under medium or static loads. Black heart malleable cast iron has high toughness and good comprehensive performance. Malleable cast iron is obtained by malleable annealing treatment of cast iron. Forging annealing takes a long time. By adding a certain amount of alloy, the forging annealing time can be shortened. The cast iron blank is heat-treated in a sealed annealing furnace. When annealing in a neutral furnace atmosphere, there is flocculent graphite in the cast iron structure. Although this graphite is not very round and dense, its splitting effect on the matrix is much smaller than that of flake graphite in gray cast iron, so it can give cast iron higher strength and good toughness. It is suitable for medium and low-pressure valves with a working temperature between -15℃ and +250℃ and a nominal pressure of PN≤2.5MPa.
3. Ductile iron is a high-strength cast iron material developed in the 1950s, and its comprehensive performance is close to that of steel. It is precisely because of its excellent performance that it has been successfully used to cast some parts with complex stress and high requirements for strength, toughness, and wear resistance. Ductile iron has rapidly developed into a widely used cast iron material second only to gray cast iron. The so-called 'replacing steel with iron' mainly refers to ductile iron.
Ductile iron obtains spherical graphite through spheroidization and inoculation treatment, which effectively improves the mechanical properties of cast iron, especially improves plasticity and toughness, thereby obtaining higher strength than carbon steel. It is suitable for medium and low-pressure valves with a working temperature between -30℃ and +350℃ and a nominal pressure of PN≤4.0MPa.
4. Carbon steel is an iron-carbon alloy with a carbon content of 0.0218%~2.11%. Also known as carbon steel. It generally also contains small amounts of silicon, manganese, sulfur, and phosphorus. Generally, the higher the carbon content in carbon steel, the higher the hardness and strength, but the lower the plasticity. It is suitable for medium and high-pressure valves with a working temperature between -29℃ and +425℃, of which 16Mn and 30Mn are between -40℃ and +450℃ and are often used to replace ASTMA105.
5. Low-temperature carbon steel (LCB), low-temperature steel refers to alloy steel suitable for applications below 0℃. Those that can be used below -196℃ are called low-temperature steel or ultra-low-temperature steel. It is suitable for low-temperature valves with a working temperature between -46℃ and +345℃.
6. Alloy steel (WC6, WC9), alloy steel is called alloy steel, in which other alloying elements are added in addition to iron and carbon. An iron-carbon alloy formed by adding one or more alloying elements on the basis of ordinary carbon steel. According to the different elements added and the appropriate processing technology, special properties such as high strength, high toughness, wear resistance, corrosion resistance, low-temperature resistance, high-temperature resistance, and non-magnetic properties can be obtained. It is suitable for high-temperature and high-pressure valves for non-corrosive media with a working temperature between -29℃ and +595℃; 5. WC12 is suitable for high-temperature and high-pressure valves for corrosive media with a working temperature between -29℃ and +650℃.
Valve body
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