Fabrication of Carbon-Bonded Alumina Filters by Additive-Manufactured, Water-Soluble Polyvinyl Alcohol Filter Templates and Alginate-Based Slips

Since solid, nonmetallic inclusions considerably impair the mechanical properties of cast steel products, the removal of inclusions within micrometer range constitutes a major challenge. A new approach for the production of carbon-bonded alumina filters is investigated. Water-soluble polyvinyl alcohol (PVA) filter templates are fabricated with the aid of additive manufacturing and coated with alginate-based slips. The coated filter templates are placed in an aqueous solution enriched with Ba2+ ions, triggering the gelation of the alginate-based slip and the dissolution of the template. The hollow filters are subsequently coated twice with an alginate-free slip and fired once at 800 degrees C. To evaluate the coating procedure, the filter samples are analyzed with regard to the filter structure and the mechanical properties after the coating steps. The results reveal that carbon-bonded alumina filter with a sufficient dimensional filter stability can be produced without a thermal template removal. Thereby, a cold crushing strength of 0.13 MPa is achieved using additive-manufactured PVA filter templates and an alginate-based coating slip with a solid content of 55.6 wt% and an alginate content of 0.65 wt%.