Rheological Evolution of Ti-Bearing Slag with Different Volume Fractions of TiN
- PDF / 3,210,250 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 69 Downloads / 147 Views
CTION
VISCOSITY is one of the important factors in controlling the slag tapping in the blast furnace. It is generally accepted that the viscosity must be sufficiently fluid for the slag-tapping operation. Ti-bearing slag, dispersed with high melting solid phases of TiC, TiN, and their solid solution Ti(C, N), is composed of solid–liquid dual phases at the smelting temperature.[1,2] Various investigations have been carried out on Ti-bearing slag to study the flow behaviors. Many reports[3–5] treated Ti-bearing slag as a Newtonian fluid and measured the viscosity neglecting the effect of the shear rate. In fact, it has been proven[6] that the shear rate also has an important but easily neglected influence on the viscosity of Ti-bearing slag. Although the non-Newtonian behaviors of molten slag are very complex phenomena, they are recommended to be characterized since they are responsible for the fluidity properties.
In consideration of the importance of the viscosity for metallurgical slags, considerable attention has been paid to measure and model the viscosity. Some models are based on the Arrhenius law as given in Eq. [1]. Mills[7] proposed the NPL model to relate the viscosity through the corrected optical basicity, and suggested that the optical basicity was a better parameter than the ratio of nonbridging oxygen to tetragonally bonded oxygen to describe the viscosity. Zhang[8] proposed a model that used the numbers of three different types of oxygen ions to express the activation energy and the viscosity. Other models are based on the Weymann-Frenkel kinetic theory of liquids as given in Eq. [2]. Riboud[9] derived the parameters in the model by dividing the chemical constituents into five groups depending on their ability to break or form polymeric chains in the molten slag. Urbain[10] paid more attention on the activation energy dependence on the composition, and a polynomial expression of the composition containing three terms was suggested to describe the activation energy. EA g ¼ Aexp ½1 RT
HONGRUI YUE, ZHANWEI HE, TAO JIANG, PEINING DUAN, and XIANGXIN XUE are with the School of Metallurgy, Northeastern University, Shenyang 110819, China. Contact e-mails: [email protected], [email protected] Manuscript submitted July 3, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
g ¼ ATexp
EA ; RT
½2
where g is the viscosity; A is the pre-exponent factor; EA is the activation energy; R is the gas constant; T is the absolute temperature.
All these models discussed above are qualified to estimate the viscosities of certain kinds of metallurgical slags. However, they are not appropriate for predicting the viscosities of Ti-bearing slag with two phases. For a solid–liquid dual-phase mixture, Roscoe[11] developed the following theoretical relation between the solid-free and the solid–liquid mixture viscosity for a dilute solution of spheres, which is based on a previous study by Einstein.[12] g ¼ g0 ð1 afÞn ;
½3
where g0 is viscosity of the solid-free mixture; f is the volume fraction of solid particles
Data Loading...
