Heat treating

Apparatus for melting metal comprising:

• i. a crucible for containing metal to be melted therein
• ii. a plurality of plasma-forming nozzle devices positioned in fixed relationship with respect to said crucible, each device having means for forming a plasma jet, each such jet forming means being positioned so as, when there is metal in the crucible to be melted, to be directed towards a respective one of a plurality of distinct surface portions of said metal
• iii. a first source of direct electric current having two poles, one said pole being electrically connected to each of said nozzle devices, the other said pole being electrically connected to said metal in said crucible
• iv. means for generating a magnetic field across said surface portions of said metal in a direction extending at an inclination to the direction in which a respective plasma jet is formed by each said plasma jet forming means, whereby said magnetic field will act on each plasma jet to deflect it,
• v. a second source of electric current connected to said magnetic field generating means for supplying current thereto, and
• vi. means for controlling the electric current supplied by said second source independently of said direct current, thereby to control said magnetic field to oscillate said plasma jets.