Rheological study on cordierite paste during extrusion

A cordierite compound used in the catalytic converter was synthesised with commercial materials (kaolin, ball clay and magnesite) by heat treatment at 1350°C. For increasing the open porosity of sintered body 40 wt-% of raw materials were mixed with 60 wt-% of the same calcined batch (heated at 1350°C). A paste rheology of the above mentioned body was studied with a ram extruder and extrusion was done under two different conditions, i.e.constant force and constant velocity. The rheological parameters were obtained by the Benbow–Bridgwater model. The pastes were found to have the Bingham behaviour. The effects of extrusion velocity and die geometry on the extrudated surface defects were also investigated. The results showed that while the increase in the die length reduces the surface defects of the specimen, the extrusion velocity increases the popularity of the surface flaws.