Search results

Electro‐magnetic stirrers, applied to the mold of a continuous caster, induces electromagnetic forces that influence the steel flow pattern modifying the casting parameters. The steel quality has been highly improved by the application of this magneto‐hydro‐dynamic (MHD) technique. Anyway, the complexity of the MHD interaction made difficult the complete comprehension of the factors that contribute to eliminate the defects due to the inclusions in the cast products. The optimization of the MHD techniques is still the object of a large research effort, which utilizes both experimental activity and numerical simulation. In this paper, the numerical simulation of the 2D flow pattern of the molten steel in a mold for billets has been done. The attention is focused on the gradient of the velocity of the molten steel near the wall and on the effects that the gradient change determines on the inclusions, which are present in the metallic pool. Actually the increase of the velocity gradient corresponds to the increase of the forces that can clean the solidifying shell from the inclusions.

To investigate the feasibility of a novel scheme of high‐efficiency induction heater for nonmagnetic metal billets which use superconducting coils.

The idea is to force the billet to rotate in a static magnetic field produced by a DC superconducting magnet. Since a static superconducting magnet has no losses, the efficiency of the system is the efficiency of the motor used. In order to evaluate the temperature distribution arising from the field profile produced by a given SC coil configuration, a numerical model, based on an equivalent electric network with temperature‐dependent parameters, is developed.

A substantial independence of the shape of the temperature profile on the angular velocity and the value of the uniform magnetic field applied, is observed. A strong temperature gradient is observed in the radial direction in the proximity of the penetration front and in the axial direction at the top and bottom surface of the billet. Small temperature gradient was observed in the central part of the billet.

The reported temperature profile is inadequate for an actual extrusion process which is desired to happen at a constant temperature. The appropriate profile along the billet length can be achieved by a suitable axial shaping of the magnetic field, through the optimization of the coil layout, whereas the undesired radial gradient can be reduced by interspacing the rotation with temperature smoothing intervals.

The investigation of the profile of applied magnetic field and the heating procedure which allow to achieve the distribution of temperature suitable for the extrusion process can be carried out by using the present model.

A high‐efficiency induction heater for nonmagnetic metal billets using superconducting coils in a novel scheme is investigated.

The analysis of particles trajectories in a vertical cylindrical coil shows that the magnetization force acting on paramagnetic particles has predominantly axial component which aims upwards and opposite to the gravitational force. In case of superconducting coil and depending on the value of the particle susceptibility, the axial force component can exceed several times the force of gravity. As a result, a motion of the particles in vertical upward direction appears. This effect was utilized to realize a magnetic separator, the main advantage of which is the high effectivity of separation process. A NbTi SC coil generates the magnetization force with a flux density field up to 12 T. Experiments with SiC inclusions in molten Aluminium have been performed to confirm the feasibility of this segregation concept.

This paper describes how Italy addressed the first Coronavirus disease 2019 (COVID-19) wave and analyzes the possible causes of the current second wave.

Descriptive analysis of critical points and differences in the containment strategies between the first and the second waves in Italy.

Italy's strict lockdown has been credited with getting the initial major outbreak under control. Furthermore, the way Italy handled the first wave was considered a lesson for other countries. On the contrary, a decentralized and highly bureaucratic political system with low coordination and political conflicts between government, regions and stakeholders led to a relaxation of individual health behaviors, poor and conflicting communication to the general public, poor management of the public transport and the reopening of schools and companies after the summer, that in turn generated the second wave, which is showing signs of becoming worse than the first.

This is a commentary piece.