Upright die pressing of refractory hollowware for steel ingot casting with reduced clay content

This phenomenological study investigated alumina-mullite refractories with a large height–diameter ratio bonded by 3 wt% clay and temporary additives. The temporary additives were categorized into binders, plasticizers, pressing aids and lubricants. The influence of the additive mixes on apparent and bulk density, open porosity, bending strength and exemplary density gradients was determined. Due to improved lubrication, one of the highest strengths (19 MPa) and lowest open porosities (18%) was achieved by combining a polysaccharide binder, a high-viscous cellulose derivative plasticizer, a fatty acid lubricant and a wax dispersion pressing aid. Mainly the polysaccharide and the fatty acid improved the lubrication due to their functional groups. Hence, upright die pressing was successful. The density gradient, however, was unaffected by the regarded additives.