Application of Non-Arrhenius Models to the Viscosity of Mold Flux

Abstract

The mold flux in continuous casting mold experiences a significant temperature gradient ranging from more than 1773 K (1500°C) to room temperature, and the viscosity of the mold flux would therefore have a nonArrhenius temperature dependency in such a wide temperature region. Three non-Arrhenius models, including Vogel-Fulcher-Tammann (VFT), Adam and Gibbs (AG), and Avramov (AV), were conducted to describe the relationship between the viscosity and temperature of mold flux in the temperature gradient existing in the casting mold. It found that the results predicted by the VFT and AG models are closer to the measured ones than those by the AV model and that they are much better than the Arrhenius model in characterizing the variation of viscosity of mold flux vs temperature. In addition, the VFT temperature and AG temperature can be considered to be key benchmarks in characterizing the lubrication ability of mold flux beyond the break temperature and glass transition temperature.Viscosity is one of the most important properties of mold flux as it determines the powder consumption and therefore the lubrication of the shell; [1,2] it also affects the formation of the slag rim in the vicinity of the meniscus, [3] the slag entrapment, [4] as well as the erosion of the nozzle. [5] Early models for predicting the viscosity of mold flux were developed by using viscosity measurements that spanned relatively small ranges of temperature and viscosity. The data, derived from these restricted ranges of experimental conditions, were generally linear in reciprocal of temperatures; thus, the early models follow Arrhenius formulation strictly. [6][7][8] But, the mold flux in a continuous casting mold experiences a wider temperature gradient from more than 1773 K (1500°C) to room temperature. [9,10] For the mold flux on top of the molten steel, its temperature is close to the molten steel, while its temperature decreases to break temperature after the liquid mold flux infiltrates into the gap between the mold wall and the shell; its temperature further decreases to room temperature as the mold flux comes out with the slab from the bottom of the mold. The mold flux viscosity does not show strong Arrhenius dependency over such wide temperature variation.There are three models developed for description of the non-Arrhenius temperature-dependent viscosity in silicate melts, including Vogel-Fulcher-Tammann (VFT), Adam and Gibbs (AG), and Avramov (AV).The Vogel-Fulcher-Tammann (VFT) model was proposed by Vogel, Fulcher, and Tammann, [11][12][13] and it has been widely used to estimate the variation of viscosity of magma, [14,15] glass-forming liquids, [16] polymers, [17] ceramics, [18] ionic liquids, [19] etc. It was expressed as:where g is the viscosity in Pa s and T is the absolute temperature (K). The variables A VFT , B VFT , and C VFT are adjustable parameters representing the pre-exponential factor, the pseudo-activation energy, and the VFT temperature, respectively.The Adam-Gibbs model [20] is the result of a generalization and a...

A Review of Fluorine-free Mold Flux Development

“…It can effectively increase the thickness of the solid crystalline layer of slag film to reduce the heat transfer and make the reduction of the longitudinal cracking occurs. Subsequently, Wang et al 42,49,50) . 8.…”

Effect of ZrO2 on the Melting, Viscosity, and Crystallization Behaviors of Fluorine‐Free Mold Flux for Casting Medium Carbon Steels

“…The viscosity tests were conducted through the rotating cylinder method by using a Brookfield DV‐II+ viscometer (Brookfield Inc., USA), which is schematically shown in Figure a. The viscometer was calibrated by using the standard oil with known viscosity at room temperature before the viscosity test …”

New Mold Slag Compositions for the Continuous Casting of Soft Steels

“…[17][18][19][20][21] Moreover, the effect of basicity on the structure and viscosity of boron-containing slags differs from its effect on F-containing slags. Zhou et al [22][23][24] designed mold slag compositions for the casting of medium-carbon steels. They focused on the investigation of the crystallization behavior and compared it to a conventional F-containing mold flux.…”