Alginate-based robo gelcasting of cellular ceramics for steel melt filtrationThursday (08.10.2020) 11:30 - 11:50
Due to their favorable tribological, thermal, chemical and mechanical resistance, porous cermaics are applied in many industries. Besides the meterial selcetion, the manufacturing process has a major influence on the property profile of the final component. Common manufacturing processes such as the replication technique are popular due to their cost efficiency and simplicity, however, they also may have some major drawbacks. The burnout of the polymer template during the firing process leads to the formation of characteristic triangular, sharp-edged voids within the filter struts, which lead to local (thermo-)mechanical stress concentration. Furthermore, the variation of possible pore structures is mimited due to the availability of commercially available and cost-effcient replication templates. In 2006, Essock et al. already investigated an alternative process for the manufacturing of so-called "spaghetti" filters for the application in metal melt filtration. The process is based on the plastic shaping via extrusion and the random stacking of a contious strand over a moveable base plate.
In order to allow for the fast-speed manufacturing of periodic, ordered cellular structures, a novel gelcasting process was developed and investigated. Thereby, a ceramic suspension with < 1 wt% sodium alginate is pumped into a calcium chloride solution. At contact, the suspension gels instantly and retains the cross section of the applied nozzle. In a continuous process, the gelled strand is stacked in periodic patterns by means of a cartesian portal robot system.
Using the example of carbon-bonded alumina, the influence of the solid content and the alginate content on the process regarding workability, dimensional stability, mechanical strength and shrinkage was investigated. Furthermore, the filters were upscaled and tested in conact with molten steel.