Measurement of viscosity and melting characteristics of mould powder slags by ultrasonics
TL;DR: In this article, the authors present an attempt to find the possibility of measuring high temperature properties of mold powder slags such as viscosity, break temperature, liquidus temperature during heating as well as solidification start and solidification end temperatures during cooing using ultrasonics.
Abstract: The paper presents an attempt to find the possibility of measuring high temperature properties of mould powder slags such as viscosity, break temperature, liquidus temperature during heating as well as solidification start and solidification end temperatures during cooing using ultrasonics. These powders are used in continuous casting of steel and the abnormality in their properties can impact the productivity and quality of the steel products. These properties are in general measured by high temperature rotational viscometers, hot stage microscopes and DTA instruments. Here, the fundamental flexural guided wave mode F(1,1) in a ceramic buffer rod was employed in experiments. The results show the possibility of measuring all the above properties in single experiment by measuring ultrasonic reflection factors during continuous heating and cooling of the mould powders. The advantage of the ultrasonic system is that it can be installed in the plant for online monitoring of these properties. The ultra...
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01 Feb 2014-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the effect of B2O3 on the viscosity and structure in the calcium-aluminate melt flux system containing Na2O was studied, and the results showed that B23 additions decreased the [AlO4]-tetrahedral structural units and transformed the 3-dimensional complex network structures such as pentaborate and tetraborate into 2-dimensional isolated network structures, resulting in lower viscosities.
Abstract: The effect of B2O3 on the viscosity and structure in the calcium-aluminate melt flux system containing Na2O was studied. An increase in the B2O3 content at fixed CaO/Al2O3 ratio lowered the viscosity. Higher CaO/Al2O3 ratio at fixed B2O3 content also decreased the viscosity. The alumino-borate structures were confirmed through Fourier transformed infrared (FTIR) and Raman spectroscopy and consisted of [AlO4]-tetrahedral structural units, [BO3]-triangular structural units, and [BO4]-tetrahedral structural units, which could be correlated to the viscosity. At fixed CaO/Al2O3 ratio, B2O3 additions decreased the [AlO4]-tetrahedral structural units and transformed the 3-D network structures such as pentaborate and tetraborate into 2-D network structures of boroxol and boroxyl rings by breaking the bridged oxygen atoms (O0) to produce non-bridged oxygen atoms (O−) leading to a decrease in the molten flux viscosity. At fixed B2O3 contents and higher CaO/Al2O3 ratio, 3-D complex network structures become 3-D simple and 2-D isolated network structures, resulting in lower viscosities. The apparent activation energy for viscous flow varied from 132 to 249 kJ/mol according to the composition of B2O3 and CaO/Al2O3 ratio.
105 citations
TL;DR: In this paper, the authors proposed a new constitutive model for coal ash, where the stress tensor not only has a yield stress part but also has a viscous part with a shear rate dependency of the viscosity, along with temperature and concentration dependency, while allowing for the possibility of the normal stress effects.
Abstract: The viscosity of slag and the thermal conductivity of ash deposits are among two of the most important constitutive parameters that need to be studied. The accurate formulation or representations of the (transport) properties of coal present a special challenge of modeling efforts in computational fluid dynamics applications. Studies have indicated that slag viscosity must be within a certain range of temperatures for tapping and the membrane wall to be accessible, for example, between 1,300 °C and 1,500 °C, the viscosity is approximately 25 Pa·s. As the operating temperature decreases, the slag cools and solid crystals begin to form. Since slag behaves as a non-linear fluid, we discuss the constitutive modeling of slag and the important parameters that must be studied. We propose a new constitutive model, where the stress tensor not only has a yield stress part, but it also has a viscous part with a shear rate dependency of the viscosity, along with temperature and concentration dependency, while allowing for the possibility of the normal stress effects. In Part I, we reviewed, identify and discuss the key coal ash properties and the operating conditions impacting slag behavior.
33 citations
TL;DR: A novel technique for simultaneously measuring the moduli of elastic isotropic material, as a function of temperature, using two ultrasonic guided wave modes that are co-generated using a single probe is presented here.
Abstract: A novel technique for simultaneously measuring the moduli of elastic isotropic material, as a function of temperature, using two ultrasonic guided wave modes that are co-generated using a single probe is presented here. This technique can be used for simultaneously measuring Young's modulus (E) and shear modulus (G) of different materials over a wide range of temperatures (35 °C-1200 °C). The specimens used in the experiments have special embodiments (for instance, a bend) at one end of the waveguide and an ultrasonic guided wave generator/detector (transducer) at the other end for obtaining reflected signals in a pulse-echo mode. The orientation of the transducer can be used for simultaneously generating/receiving the L(0,1) and/or T(0,1) using a single transducer in a waveguide on one end. The far end of the waveguides with the embodiment is kept inside a heating device such as a temperature-controlled furnace. The time of flight difference, as a function of uniform temperature distribution region (horizontal portion) of bend waveguides was measured and used to determine the material properties. Several materials were tested and the comparison between values reported in the literature and measured values were found to be in agreement, for both elastic moduli (E and G) measurements, as a function of temperature. This technique provides significant reduction in time and effort over conventional means of measurement of temperature dependence of elastic moduli.
25 citations
TL;DR: In this article, the authors used a bank of straight ultrasonic waveguide temperature sensors attached to a single ultrasonic pulser-receiver instrument for the measurement of temperature at multiple levels.
24 citations
TL;DR: Novel multiple bent waveguide method proposed to measure temperature in a chamber using two configurations of bent wires used with single transducer and electronics to improve upon the earlier reported studies using straight waveguides.
21 citations
References
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01 Jan 1973
TL;DR: In this article, the authors apply the material developed in the Volume One to various boundary value problems (reflection and refraction at plane surfaces, composite media, waveguides and resonators).
Abstract: This work, part of a two-volume set, applies the material developed in the Volume One to various boundary value problems (reflection and refraction at plane surfaces, composite media, waveguides and resonators). The text also covers topics such as perturbation and variational methods.
5,211 citations
TL;DR: In this article, it is shown that the L(0, 1) mode, which is comparable to the A0 Lamb wave mode in flat plate, can be generated with acceptable efficiency.
309 citations
TL;DR: In this article, a model based on the optical basicity corrected for the cations required for the charge balance of AlO5-4 is investigated, which has the advantage of being generally applicable and not limited to slags of a certain composition.
Abstract: A model based on the optical basicity corrected for the cations required for the charge balance of AlO5-4 is investigated. This model has the advantage of being generally applicable and not limited to slags of a certain composition. The calculated results were in reasonable agreement with traceable experimental data for a range of synthetic slags and industrial iron- and steelmaking slags. The latter included mould fluxes and blast furnace, steelmaking and coal slags. For most slag compositions here, the viscosities predicted with the present model were in better agreement with the measured values than those predicted by the Riboud and Urbain models; coal slags were the only exception. In the case of CaF2 containing slags, the results indicate that an optical basicity of CaF2 of 1·2 provided the best fit to the viscosity data.
252 citations
229 citations