Development of Viscometer Based on Single Sphere Pulling Method for Application to High Temperature Melts

抄録

To evaluate the viscosities of molten slags that are suitable for capillary refining, a viscometer has been developed based on the single sphere pulling method that enables high accuracy viscosity measurement of high temperature melts. Viscosity measurements using the sphere pulling method generally carry experimental uncertainties attributed to shear stress on the wire suspending the sphere, which is not taken into account in the conventional Stokes’ law when deriving the liquid viscosity from the viscous force applied to a moving sphere in a liquid. In this study, we first considered a modified Stokes’ law equation that describes the balance between the external force and the sum of forces applied to the sphere and the suspension wire including shear stress, ascending force and the surface tension of a liquid applied to the wire, and then determined the liquid viscosity from movement of a single sphere by measuring the external force when the sphere passed through a set position. Second, we designed a new viscometer that controls the liquid container’s velocity using an electrical actuator and measures viscous force on a single sphere statically suspended from an electrical valance. We confirmed that relative sphere velocity in the liquid reaches terminal velocity immediately. These treatments improved the viscosity evaluation accuracy using the single sphere pulling method, and this viscometer enables the viscosity of the standard reference material (SRM2) for high temperatures to be measured to within ±5% relative errors from the recommended values, which is adequate for viscosity measurement of high temperature melts.