Research of the rheological and casting properties of alumina slips and samples from them containing a new dispersing addition and its combination with a hardening addition
The corundum ceramics technology has been developed and implemented at JSC “The URIR named after A. S. Berezhnoy”, which involves the production of high refractory corundum high density products using different methods of forming. A slip casting in gypsum form is one of the often used for forming a corundum ceramics production. The advantage of this method is the simplicity of the equipment, the relatively low cost of forms, as well as the possibility of manufacturing products of various shapes, sizes and weights.
In depending of the wall thickness of the product using two methods of slip casting: bulk method with using a slip with a density of 2.5 g/cm3 of alumina MARTOXID brand with a dispersing addition (based on an aqueous solution of an ammonium salt of an acrylic copolymer) in an amount of 0.4 % for casting products of complex configuration, insulators, rods, plates, mortars, pestles, and for casting thick-walled products (4—5 mm and more) and a drain method with using a slip with a density of 2.1 g/cm3 of alumina MARTOXID brand with a dispersing addition in an amount of 0.3 % and a hardening addition in an amount of 0.2 % for casting hollow articles in the form of crucibles, covers, pipes, a ditch, boats, etc. for casting thin-walled products (1—3 mm).
The researches of rheological properties of alumina slips from alumina MARTOXID brand which contain a new dispersing addition based on carboxylic acid and its combination with a hardening addition were carried out in this work.
The optimum values of rheological and casting properties of the slips, ensuring the production of castings with a maximum density, are achieved with the introduction of 0.3 and 0.2 % dispersing addition into the slips with a density of 2.5 and 2.1 g/cm3 respectively were established.
It was established that, at use of the dispersing addition based on carboxylic acid the apparent density of green body corundum ceramics lower than with the dispersing addition based on an aqueous solution of an ammonium salt of an acrylic copolymer, but it is sufficient to produce the same high-quality products after firing at 1580 оC (open porosity is not > 0.8 %) with a slightly higher shrinkage during firing, i. e. the use of this addition, if necessary, is possible.