The thin slab casting (TSC) of steel is a type of the continuous casting (CC) with a narrow funnel-shaped mold, characterized by the rapid solidification and fast production rates. A highly turbulent flow impacts on a growing solid shell due to the constant feeding of the fresh hot melt. That strongly affects the solidification profiles and final quality of the TSC slabs. The presented work numerically investigates the solidification inside the TSC mold with the asymmetric flow pattern caused by the misalignment (tilting) of the submerged entry nozzle (SEN). These effects were considered with and without the applied electromagnetic brake (EMBr). The influence of the adjustable EMBr on the asymmetric flow and solidification profiles including turbulent and magnetohydrodynamic (MHD) effects were studied. During consistent series of simulations, the EMBr was varied between the magnetic poles and the time-averaged velocity and temperature fields were collected. The results showed that symmetric EMBr of a local type could partially improve the asymmetry. An optimal braking scenario was found for the casing speed of 5.5 m/min and maximum EMBr value of 180 mT. The solidification and MHD models including turbulence were developed using OpenFOAM®.
A funnel-type mold is commonly used to provide necessary clearance for the submerged entry nozzle in the thin slab casting (TSC). The partially solidified shell is subjected to the mechanical deformations, which can lead to the defects formation and, as a results, to a breakout. Traditionally, the results of the flow simulation, performed by the finite volume method (FVM), are fed to the external package for the finite element analysis of stress and strain. A coupled model was assembled using “creeping solid” approach by blending the Norton-Hoff viscoplastic stress for the solidifying shell with the Newtonian viscous stress of the liquid melt. The FVM was used to combine both liquid and solid stress models within a single solver. The iterative procedure based on the improved both side diffusion method was introduced to treat the nonlinear relation between the viscoplastic stress and the strain rate. The modeled shell thickness was verified by previously published breakout measurements and the simulation results. Temperature distribution, obtained during the TSC simulation, dominantly corresponds to the viscoplastic range. Developed numerical approach is robust and has direct industrial application.
In an indoor pulse-jet bagfilter plant, erroneous activation of individual valves is to be detected. The present approach uses data of a microphone array to localize the source of sound originated by the valve. Since the valves are all installed in a horizontal layer, a two-dimensional (2D) microphone array can be used. Multipath (constructive and destructive interference) and reverberation effects due to the presence of considerable obstructions make the use of timedelay-based approaches impossible. Thus, the problem was encountered by an energy-based concept. With additional use of a kernel classifier, proper feature selection, and adaptive training, the density of microphones can be reduced, keeping a high probability of correct detection.
The kinetics of dolime dissolution containing 20 and 50 pct of magnesium oxide in steelmaking slags has been studied in a high-temperature experiment. The dissolution tests were carried out under static conditions at temperatures of between 1573 K and 1873 K (1300 °C to 1600 °C). Cylindrical samples of dolime were introduced into pre-melted slag at predetermined time intervals. The changes in mass and geometrical parameters of the samples, as well as CaO and MgO concentrations in the melt, were determined to calculate mass transfer and diffusion coefficients. The results revealed that the rate-limiting step in the process of dolime dissolution is diffusion. The increase in MgO content in the initial sample caused a drop in dolime dissolution rate and diffusion coefficients. The prediction of MgO solubility in steel slag, as well as the effect of slag basicity, was carried out using the thermodynamic software FactSage 7.1. In addition, the activation energy of diffusion has been calculated using the dependence of the logarithm of diffusion coefficients on the inverse temperature.
The world steel market is in a phase of maturity. Worldwide growth in steel demand is expected to be in the range of 1% per year and the world’s biggest market, China, is facing a phase of stagnating or even diminishing steel demand. The situation has changed from a supplier driven to a customer driven market meaning that customer demands are increasing and margins are dropping. Besides increasing levels of digitization and service orientation as well as the development of new sales channels the delivery of higher quality, introduction of new steel grades and further customization of high-end products to cover niche markets are of prime importance to keep or increase market shares. Besides efficient organization and execution of the daily business ranging from production to quality management and customer services paired with data-based insight, highly efficient research and development (R&D) with increasingly limited amount of resources is a must. This paper addresses the latter topic regarding trends for future steel grade demands and strategies for efficient R&D.
