Shear Thinning Behavior of Calcium Silicate‐Based Mold Fluxes at 1623 K

Abstract

There have been consistent efforts on understanding rheological behavior of molten mold flux, used in continuous casting of steels. It is prevalent view that molten mold flux shows non‐Newtonian behavior, meaning that the viscosity varies with shear rate history. Hence, the present study attempts to evaluate shear thinning, which is one of the characteristic non‐Newtonian behaviors, by measuring its viscosity with a rotating type viscometer at 1623 K. Furthermore, Raman spectroscopy analysis is used to appreciate the structure of molten mold flux and shear thinning. Mold fluxes tested reveal definite shear thinning characteristic of decreasing viscosity with increasing shear rate. The degree of shear thinning has been well quantified by Oswald‐De Waele power law model. Lastly, the degree of polymerization, obtained from Raman spectroscopic data has proportional relationship with degree of shear thinning in the range of 1–5 s−1 shear rate. Also, it has a downward parabolic relationship with degree of shear thinning at entire shear rate ranges up to 100 s−1. This study also verifies possibility to use shear thinning behavior on actual continuous casting process.

Controlling the shear thinning property of calcium silicate melts by addition of Si3N4

“…A calcium silicate melt is predominantly used as a lubricant for continuous casting which produces greater than 500 million ton of steel per year [1]. For an ideal casting condition, the viscosity of a liquid form of calcium silicate melts has to be high enough to avoid entrainment of mold flux at a mold top surface where shear rates roughly correspond to 10 to 40 1/s.…”

Control of Crystal Morphology for Mold Flux During High-Aluminum AHSS Continuous Casting Process

“…In addition, the driving forces, i.e., constitutional supercooling, for precipitating cuspidine in melt increase with the slag basicity decrease, and thus the corresponding Jackson a factor increases. On the other hand, our previous viscosity measurements have verified that the melt viscosity increases obviously with the basicity decrease for slag B, C, and D. [37] Therefore, it suggests the cuspidine crystal growth in lower basicity mold flux, slag B, is more likely to be controlled by the element diffusion, while that in the slag D is likely controlled by interface chemical reaction. This explains why cuspidine appears with different morphologies in the foregoing mold fluxes.…”

“…Many investigations [14,16,[39][40][41] have confirmed the supercooling of crystallization is related to the activation energy of crystallization. Our previous works have investigated their relations both in lime-silica-based [16,37] and lime-alumina-based [14] mold fluxes. Here, it would not be discussed in detail any more.…”

Development and in vivo evaluation of the moisturising potential of cosmetic formulations containing Babassu (Orbignya phalerata Martius) oily extract

“…Pseudoplastic behavior is ideal for products to be applied topically, since after overcoming the initial resistance to flow, viscosity decreases enabling easy application of the product on the skin (32). The flow curves obtained show similar decreasing viscosity when the rotational speed (shear rate) is increased (33,34). For all formulations, viscosity decreasing when rotational speed increases could be associated to thixotropy, a time-dependent shear thinning property.…”

“…O comportamento pseudoplás-tico é ideal para que os produtos sejam aplicados topicamente, uma vez que após a superação da resistência inicial ao fluxo, a viscosidade diminui permitindo a fá-cil aplicação do produto sobre a pele (32). As curvas de fluxo obtidas mostraram uma viscosidade decrescente semelhante quando a velocidade de rotação (taxa de cisalhamento) é aumentada (33,34 (32,35). Regarding the droplet size, according to Robins and coworkers (30) and Merryweather (31), an O/W emulsion should present a dispersed phase of small oil droplets with diameters ranging from 1 to 10 µm.…”