What material is used to make the ring seat of a hot-mounted seal ring?

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The hot-fit sealing ring involves heating the ring seat to expand it, then inserting the cemented carbide ring into the seat; upon cooling, an interference fit is achieved. This approach preserves the excellent properties of cemented carbide while reducing costs, which is why it is widely used. If the linear expansion coefficient of the ring seat is too high, a gap will appear in the interference fit at operating temperature, causing the cemented carbide ring to loosen and resulting in seal failure. Therefore, materials with a low coefficient of linear expansion should be chosen. At the same time, the ring seat material must be resistant to corrosion by the medium, possess sufficient strength and stiffness at high temperatures, and be inexpensive. Commonly used materials for ring seats at present include chromium steel (such as 3Cr13), 1Cr18Ni9Ti, and Cr18Ni12Mo2Ti; abroad, CAP42 alloy is also used. Titanium alloys are used in corrosive media. Although the linear expansion coefficients of these materials differ significantly from those of cemented carbide (YG6, YG8), resulting in a larger interference value, this is limited by the strength of the ring seat and the cemented carbide ring. At the same time, a large interference value causes changes in the flatness of the sealing surface, which is undesirable. The CAP42 (Carpenter 42) used abroad is equivalent to China’s 4J42; it is an Fe-Ni alloy containing 42% nickel. Its characteristic is that the linear expansion coefficient remains relatively constant over a wide temperature range, which is why it is called a constant-expansion alloy. It is an ideal material for manufacturing ring seats, can be used at temperatures above 400°C, but it is relatively expensive. Titanium and titanium alloy materials can be used in high-temperature corrosive media. They exhibit excellent corrosion resistance in oxidative media, and can withstand corrosion from sulfides, chlorides, seawater, acetic acid, and other substances. A large amount of titanium is also used in the production of caustic soda and urea.