Machining of Rotary Valve Seal Surface

The processing steps of the cemented carbide seal surface are as follows: wire cutting is used to process the rotary feeding valve to the coarse grinding size; the grinding machine is used to fine grinding the seal surface; the manual grinding method is used to lapping the valve seat with the impeller seal surface to the required surface finish. While wire cutting the cemented carbide, if not properly controlled, it can easily lead to cracking of hard alloys, especially when cutting the large pieces of cemented carbides. The cause of this phenomenon is the uneven distribution of the particles in the hard alloy, leading to the inhomogeneous of the "internal energy" of the hard alloy. In the process of processing, the stress is caused by the action of molybdenum wire, and the stress is released locally in a short time, which directly cause the cracking of the cemented carbide. Therefore, in order to avoid the damage of the seal surface of the mechanical seals in the process of wire cutting, it is necessary to pay attention to the following conditions: because of the low thermal conductivity of the hard alloy, the internal stress is difficult to release in a short time during the production process. When the cemented carbide is fired and wire cut, it need to slow down the temperature and cooling rate and extend the holding time of high temperature as far as possible. After the completion of cemented carbide seals, put it in the open air or indoor surface for a period time.

Before wire cutting, we should first grind the large cylindrical surface of the hard alloy, and then cut it after putting aside for a few days. If we can make coarse grinding before natural aging, it will be more stable. When grinding the cemented carbide with diamond wheels, we need to adopt both rough grinding and fine grinding. In a word, the key point is to release the internal energy evenly to the least before cutting the hard alloy, and reduce the stress concentrated to the work piece when the hard alloy is cut on line.

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