15th WCIC Agenda MONDAY, AUGUST 22, 2022, CON’T...
1:00 p.m. – 1:30 p.m. Advanced Analysis Techniques of Slurry Stability Utilising Zeta Potential Testing of Colloidal Silica Gavin Dooley, REMET UK, Booth No. 217 Zeta
potential
using the zeta potential equipment. Samples were shown to have different charges when subjected to freezing conditions within the lab. This offers the opportunity to assess if a colloid has been frozen during its lifecycle during transport and storage.
testing is a common measurement
technique of colloidal dispersions. The test can be used to quantify the charge on the particle of colloidal silica at different states. The stability of a colloidal silica can affect many aspects of a slurry within the shell room including binder viscosity, shell strength, gelling of the slurry and slurry life. The longevity of the slurry and replacement costs are directly related to this important property within the colloid and therefore, should be understood further. REMET® UK has recently acquired a zeta potential measurement kit to understand the effect of this property on slurry performance. First, a defined test method was established and is presented within this paper, which reduces error within the test and allowed for repeatable tests. A review of the effect of pH on colloids was also conducted. Furthermore, binders resistant to pH changes are presented within this paper. Following this, the lifecycle of the binder was measured
over time utilizing accelerated aging tests within the REMET® UK Laboratory. Finally, the effect of freezing was conducted
1:30 p.m. – 2:00 p.m. Viscosity Control for Consistent Casting Shell Building Dr. Sunil Kumar, Rheonics, Booth No. 222 Quality assurance of casting shells depends on the viscosity of the shell-building slurry. This has two principal reasons. First, the viscosity is directly related to the solids content of the slurry and reflects shifts in its composition through evaporation of the liquid component. And second, the performance of the slurry is directly related to its flow characteristics. The thicker the slurry – the higher its viscosity – the slower it runs off the form and the thicker the layer that it deposits. If the viscosity is too low – the slurry is too thin – it flows off the form too quickly, and the deposited layer is too thin. If too high, it can produce too thick a layer, which may not dry or harden quickly enough, or may fail because of drying-induced stress. Since shells are formed from multiple layers, any deviations of slurry viscosity can contribute to failures of quality and performance of the shells, which can, in turn, lead to defects in the parts cast in the shells. In order to control viscosity, it is necessary to measure
it. The accuracy of control – how well the viscosity of a slurry can be set and maintained throughout the casting process – depends on the accuracy and repeatability, but also the ease of use, of the chosen measurement instrument. The traditional measurement method is the flow cup, which measures viscosity as the number of seconds required by the slurry to run out of the cup. This measurement is not suited for continuous, repetitive monitoring of viscosity, nor is it particularly accurate.
A robust balanced torsional resonator-based inline viscometer enables accurate, repeatable and continuous monitoring of slurry viscosity during shell building. An integrated slurry viscosity tracking and control system is used to apply the viscometer’s measurements toward maintaining constant slurry viscosity during slurry preparation and shell building, despite evaporation losses, temperature changes and other influences that can cause unwanted changes to the shell quality. The inline viscometer and the integrated control system can, in addition, support the growing trend toward full shell-room automation, by reducing an important source of variability in the otherwise highly automated shell- building process.
2:00 p.m. – 6:00 p.m. EXPO – Disneyland Exhibit Hall & Disneyland North Ballroom
26 ❘ August 2022 ®
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