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Classification Of Cast Iron Butterfly Valve

1. Gray iron valve
It is suitable for water, steam, petroleum products and ammonia, and it can work in the most corrosive media such as alcohol, aldehyde, ether, ketone and grease. It is not suitable for hydrochloric acid, nitric acid and other media. But it can be used in concentrated sulfuric acid, because concentrated sulfuric acid can produce a passive film on its metal surface. In order to prevent the corrosion of cast iron by concentrated sulfuric acid.

2. Ductile iron valves
Strong corrosion resistance, can work in a certain concentration of sulfuric acid, nitric acid, sulfuric acid, acid salt. But it is not resistant to the corrosion of fluoric acid, strong alkali, hydrochloric acid and ferric chloride hot solution. Avoid sudden heat and cold when using, otherwise it will crack.

3. Nickel cast iron valve
The alkali resistance is better than that of gray cast iron and nodular cast iron valves; Nickel cast iron is an ideal material for valves used in dilute sulfuric acid, dilute hydrochloric acid and caustic soda.

Advantages Of Cast Iron Butterfly Valve

The carbon content of cast iron and ductile iron is at least 3%. The low carbon content in cast steel makes the carbon existing as free graphite not form structural flakes. The natural form of carbon in cast iron is free graphite flake. In ductile iron, the graphite flake is changed into tiny spheres by special treatment. The improved spheroid makes ductile iron have more excellent physical properties than cast iron and steel. It is the spherical microstructure of carbon that makes ductile iron have better ductility and impact resistance, while the internal flake form of cast iron leads to no ductility. The best ductility can be obtained by ferrite matrix. Therefore, the spherical structure of ductile iron can also eliminate the crack phenomenon of flake graphite in ductile iron after Ferritization annealing. In the micrograph of ductile iron, it can be seen that the cracks March to the graphite ball and terminate. In the ductile iron industry, these graphite balls are called “crack terminators” because of their ability to prevent fracture. Compared with cast iron, ductile iron has absolute advantage in strength. The tensile strength of ductile iron is 60K, while that of cast iron is only 31k. The yield strength of ductile iron is 40K, but the cast iron does not show yield strength, and finally fracture occurs. The strength cost ratio of ductile iron is much better than that of cast iron. The strength of ductile iron is comparable to that of cast steel. Nodular cast iron has higher yield strength, the lowest of which is 40K, while the yield strength of cast steel is only 36K. In most municipal applications, such as water, brine, steam, etc., the corrosion resistance and oxidation resistance of ductile iron are better than that of cast steel. Due to the spheroidal graphite microstructure of ductile iron, ductile iron is better than cast steel in reducing vibration capacity, so it is more conducive to reducing stress. One of the important reasons for choosing ductile iron is that the cost of ductile iron is lower than that of cast steel. The low cost of ductile iron makes this material more popular, casting efficiency is higher, and machining cost of ductile iron is less.