| 摘要 |
A method of treating high melting point metals in the form of a moving stream with a plasma arc is disclosed. The method has particular application to the superheating and/or microalloying of molten steel at the tertiary stage i.e., during teeming from the ladle (12) into a tundish (16), prior to its entry into a continuous casting machine. The transferred plasma arc (23) is struck between the cathode (28) [and microalloy (40, 42, 44)] and the teeming stream (22), thus superheating the molten steel. If added, the microalloy is dispersed as a fog, by melting, partial vapourisation and condensation and drawn down by the teeming stream (22) into the bath of molten steel in the tundish (16), where it is alloyed by the intense mixing that occurs. Microalloying with a transferred plasma arc and microalloy (52, 56, 58) submerged below the surface of the turbulent molten steel is also disclosed as an alternative. Apparatus for carrying out the method consists of a tundish (16), a ladle nozzle (13) which defines the teeming stream (22), a cathode (28) mounted adjacent to the teeming stream (22)/bath and associated electrical circuitry, as shown in Figure 3. A protective refractory hood (50, 56) for the cathode is required for a submerged plasma arc. A return electrode is positioned in the tundish, (so as to dip into the molten steel), downstream from the cathode. |
