Rotary vacuum pump in sintering of application
Vacuum sintering is a kind of sintering method of ceramic billet under vacuum condition (using rotary vacuum pump). Steam, hydrogen, oxygen and other gases contained in the pores of oxide ceramic billet can escape from the pores by dissolving and diffusing along the grain boundary of the billet or through grains in the sintering process. But the carbon monoxide, carbon dioxide, especially nitrogen, due to the lower solubility, not easy to escape from the stomatal, resulting in products containing stomatal, send density down. If the billet is sintered under vacuum condition, all gases will escape from the air hole before the billet is fully sintered, so that the product does not contain air hole, thus improving the density of the product.
The advantages of vacuum sintering with rotary vane vacuum pump are as follows
1. It is easy to control the carbon content of the alloy under the condition of vacuum sintering with rotary plate vacuum pump. At the sintering temperature, the pressure in the furnace is only tens of Pa, or even lower. O2, N2, H2 and H2O molecules are very few. Many reactions can be ignored, and the influence of the medium is very small. As long as the dewaxing process is strictly controlled, the carbon content of the alloy changes very little in the vacuum sintering process, and its properties and microstructure are quite stable.
2. Under vacuum sintering condition, the purity of cemented carbide can be improved. Rotary plate vacuum pump for vacuum sintering is beneficial to metal oxide reduction. There is no need to open the furnace door during the whole sintering cycle, and no air is allowed to enter.
3. Under the condition of vacuum sintering, there are fewer impurities adsorbed on the surface of the hard phase, which can improve the wettability of the drill to the hard phase and enhance the strength of the alloy, especially the alloy containing TiC.
4. Under the condition of vacuum sintering, the process is simple to operate. Because no filler can be used in vacuum sintering, it not only simplifies the operation, but also avoids the adverse effect of filler on the surface of sintered body.
5. The integration of dewaxing and sintering can reduce product oxidation and reduce the difficulty of carbon control; Reduce floor space, reduce labor intensity.
6. Multi-atmosphere dewaxing and sintering integration, which can control the temperature, atmosphere and pressure in the furnace in different temperature sections, can achieve isothermal sintering (heat preservation) at any temperature and complete various functions, such as gradient alloy sintering.