What are the characteristics of cast iron and carbon steel? What media can be used?
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The earliest material combination for mechanical seal friction pairs in China’s refining industry was cast iron against graphite. Cast iron has the advantages of low cost and easy processing and manufacturing. Although its hardness is not very high, its wear resistance is comparable to that of hardfaced cemented carbide; no cracks or the like occur during use. The reason is its high thermal conductivity, which is 3-4 times that of cemented carbide. The cast iron structure is relatively porous, allowing it to absorb trace amounts of liquid and form an oil-containing friction surface, thereby improving the lubrication conditions. Its drawback is poor corrosion resistance, so it can only be used in neutral media and in situations where the PV value is not high. To improve its corrosion resistance, alloyed cast iron is used; by adding appropriate elements such as aluminum, nickel, and chromium, its service life can be significantly extended at a very low cost. British company Crane Sealing has used alloy cast iron for the static ring, with good results. Commonly used carbon steels include grades 45 and 50; after quenching, their hardness and wear resistance are increased, making them suitable for use as sealing rings in neutral media.
Cast iron and carbon steel are two common materials, each with distinct characteristics and suitable applications. The main characteristics of cast iron include low cost, easy machinability, high thermal conductivity, and good wear resistance. The structure of cast iron is relatively porous, allowing it to absorb trace amounts of liquid, thereby creating an oil-containing friction surface that improves the lubrication conditions. However, its drawback is poor corrosion resistance; it is mainly suitable for neutral media with a low PV value. Alloy cast iron made by adding elements such as aluminum, nickel, and chromium can improve its corrosion resistance, thereby extending its service life at a relatively low cost. Carbon steels such as 45 and 50 steel can have their hardness and wear resistance increased through quenching treatment, making them suitable for sealing rings in neutral media. Carbon steel’s high hardness and strength enable its wide use in mechanical structures and components. In summary, cast iron is suitable for applications where low cost, wear resistance, and resistance to moderately corrosive media are required ； Carbon steel, on the other hand, is suitable for neutral environments where high hardness and wear resistance are required. .