Method and apparatus for heating molten steel utilizing a plasma arc torch

A method of heating molten steel utilizing a steel heating apparatus which comprises a refractory lined vessel having an open top, a removable cover adapted to overlie said top, and at least one plasma arc torch mounted so as to extend through said cover, said torch including a housing defining a forward end positioned on the under side of said cover, a rear electrode mounted within the housing, said rear electrode comprising a tubular metal member having a closed inner end and an open outer end, a front electrode comprising a tubular metal member mounted in coaxial alignment with said rear electrode and adjacent said open outer end thereof, and gas vortex generating means disposed intermediate said rear and front electrodes for generating a vortical flow gas which exits from the forward end of the torch, said method including the steps of

• substantially filling the vessel with molten steel,
• placing the cover so as to overlie said open top, and including positioning the forward end of the torch in spaced relation above the surface of the molten steel in the vessel, and
• operating said torch to produce a plasma arc having one end thereof attached to said rear electrode, and the other end to said molten steel, and including connecting said rear electrode as the anode to a direct current power supply and connecting said molten steel as the cathode thereof, while supplying a gas which includes at least about 80% nitrogen to said gas vortex generating means such that said vortical flow of gas contains a substantial percentage of nitrogen and such that the torch may be operated at a relatively high power level, and wherein the mass flow rate of the gas supplied to said gas vortex generating means is greater than about 10 scfm and so that the gas impinges upon the surface of the molten steel.