In foundry steelmaking, filtration is a common practice to lower the concentration of non-metallic inclusions in steel castings. Removal of non-metallic inclusions reduces the scrap rate and improves machinability, casting appearance and mechanical properties. Non-metallic inclusions are captured by different types of ceramic filters, the choice of which depends on the specific application and location in the process. Ceramic foam filters are commonly utilized in multiple positions in the gating system of sand molds and are effective by a deep bed filtration mechanism. Inclusions can be formed during the melting, pouring and casting and are separated into two main categories of endogenous and exogenous inclusions. Exogenous inclusions come from sources outside the refining process, such as worn refractories, slag, sand, or by reoxidation of the melt and are often much larger than endogenous inclusions. Endogenous inclusions are formed as consequence of the steelmaking and refining process and can be modified at different stages of steelmaking operation for effective removal. Depending on the deoxidizer used, the physical state of the inclusions can be both solid and liquid. Filtration of both solid (alumina) and liquid (manganese silicate) inclusions have been reported by several authors, however, the differences in the capture method have not been well documented. The equilibrium reactions during deoxidization of molten steel using aluminum and silicomanganese can be represented by equations 1 and 2.
- Non-metallic inclusions,
- Ceramic foam filter,
- Filtration mechanism,
- Filter micropore saturation
Available at: http://works.bepress.com/laura-bartlett/22/