Plasma Behavior under Imposition of Alternating Magnetic Field Perpendicular or Parallel to the Plasma Arc Current

抄録

Thermal plasma has advantages such as clean energy, good controllability, high power density and so on. Therefore, it has been applied to the steel industry such as heat source of molten steel in a tundish and secondary refining. For these processes, precise control of the plasma is requested for high efficiency and for high-quality products. Because the plasma is electrically conductive fluid, a magnetic field is one of the powerful tools to control its behavior under non-contact operation. Therefore, investigations to control the plasma using the magnetic field have been done. In this investigation, a DC transferred plasma arc behavior has been investigated under imposition of an alternating magnetic field of frequency range between 5 Hz and 2 000 Hz in which the magnetic field direction is perpendicular or parallel to the plasma arc current. The forces governing the plasma behavior is estimated by the simple calculation of forces acting the plasma. Under the imposition of the perpendicular magnetic field to the plasma arc current, a plasma oscillation width is constant when the magnetic field frequency is less than 50 Hz, while it decreases with increase in the magnetic field frequency if the frequency is larger than the 50 Hz. Under the imposition of the parallel magnetic field of 1 000 Hz to the plasma arc current, a burned area on a copper block by the plasma is smaller than that without the magnetic field while the burned area with the low frequency magnetic field less than 1 000 Hz is larger than that without the magnetic field.