Abstract: An enlarged and generally cup-shaped front section of the central passageway of the main body of the electrode has a rearwardly and inwardly sloping wall that extends at an angle within the range of approximately twenty to forty degrees relative to a plane perpendicular to the central axis of the electrode. The front section of the passageway has a readily replaceable and forwardly disclosed choke member having a central opening of a diameter within the range of 1.25 to 1.9 times the diameter of a rear section of the passageway. The rear section of the electrode passageway increases in diameter along a forward part of its length. The choke member comprises one of a set of similar choke members that differ from each other in the diameter of their central openings and/or in the electrically conductive material of which they are formed.

Abstract: A method and apparatus is disclosed for removing chevron cracks from the corner edges of a steel billet as it advances in a hot condition from a continuous casting operation. The apparatus includes a framework which mounts four plasma arc torches which are adapted to operate in the non-transfer arc mode, and with the torches being positioned so that the heated plasma engages respective ones of the four corner edges of the billet, to melt and heal any cracks. The framework is cyclically advanced rearwardly and forwardly along the path of travel of the billet, so as to permit effective control of the level of heating and so as to assure all longitudinal portions of the advancing billet are effectively treated.

Abstract: An apparatus for eliminating chevron cracks or other imperfections in the surface of elongate billets as billets pass vertically downwardly through a heating chamber, including a plurality of plasma arc torches. The heating chamber contains a billet mold having an opening complementary in size and shape to the cross-sectional shape of the billet. Heat imparted to the billet in the upper portion of the chamber melts surface portions of the billet. Molten material discharged from the surface portions of the billet forms a pool in an area above the mold opening. As the billet passes through the pool, some of the molten material reattaches itself to the billet surfaces. Billet conveyors pivotally movable between horizontal and vertical positions transport billets to and from the heating chamber, and control the rate at which the billets move through such chamber and through a cooling chamber located beneath the heating chamber.

Abstract: Mixed refuse containing organic and inorganic material forms a column-like mass within a furnace chamber. The column of material is heated by a plasma torch having a forward plasma-emitting end disposed within the lower portion of the column and surrounded by the refuse therein. The height of the stack is maintained at a preselected elevation above the forward end of the torch. Gases produced by pyrolytic conversion of organic components of the refuse are discharged through ports of the chamber. Melted metallic and other inorganic refuse forms a pool upon a hearth of the furnace chamber. The plasma torch imparts circulatory movement to the pool. An injector downstream from the torch directs steam onto material adjacent the surface of the pool. Excess molten material is drained from the pool and the furnace chamber.

Abstract: An assembly for the recovery of aluminum metal from aluminum dross comprising a rotary furnace, a plasma arc torch, and a supervisory control system for tying together and automatically controlling the operation of the rotary furnace and plasma arc torch is described. The invention provides recovery of aluminum metal from dross in an efficient and economical process.

Abstract: A process for recovering free aluminum and aluminum compounds such as aluminum oxide from aluminum dross in a rotary furnace heated with a plasma arc torch wherein air is preferably utilized as the arc gas is described. The use of the rotary furnace heated with plasma energy eliminates the need for a salt flux, providing a process which is ecologically safe and cost effective. A process of converting non-metallic aluminum compounds to substantially pure aluminum oxides by heating the compounds with a plasma torch operating with an oxidizing gas as the plasma torch arc gas is also described.

Abstract: A method and apparatus for heating molten steel in a steel making operation is disclosed, and which includes a refractory lined vessel having an open top, a removable cover adapted to overlie the top, and at least one plasma arc torch mounted so as to extend through the cover at an angle of about 60.degree.. The arc gas for the torch includes a substantial percentage of nitrogen, which permits a higher power level as compared to conventionally used argon, and the mass flow rate of the arc gas is maintained at a sufficiently high level to produce a continuous blast of gas which impinges at an angle upon any slag formed on the surface of the molten steel with sufficient force to move the slag and expose the underlying molten steel. As a result, the attachment of the arc to the underlying molten steel is facilitated, and the impingement of the gas contributes to the mixing of the steel to avoid heat stratification.

Abstract: A process for recovering free aluminum and aluminum compounds such as aluminum oxide from aluminum dross and aluminum scrap in a furnace heated with a plasma arc torch wherein air is utilized as the arc gas is described. The use of air as the arc gas provides greater heat output per kilowatt hour of electricity and provides for greater dross throughput. Moreover, the process is ecologically safe.

Abstract: A method and apparatus for heating molten steel in a steel making operation is disclosed, and which includes a refractory lined vessel having an open top, a removable cover adapted to overlie the top, and at least one plasma arc torch mounted so as to extend through the cover at an angle of about 60.degree.. The arc gas for the torch includes a substantial percentage of nitrogen, which permits a higher power level as compared to conventionally used argon, and the mass flow rate of the arc gas is maintained at a sufficiently high level to produce a continuous blast of gas which impinges at an angle upon any slag formed on the surface of the molten steel with sufficient force to move the slag and expose the underlying molten steel. As a result, the attachment of the arc to the underlying molten steel is facilitated, and the impingement of the gas contributes to the mixing of the steel to avoid heat stratification.

Abstract: An apparatus and method is disclosed which is adapted to consolidate and melt reactive metallic materials, and to produce a "first ingot" which is suitable for subsequent evaluation and qualification under existing specifications for such materials in the aerospace industry. The apparatus comprises an enclosed heating chamber adapted to be substantially evacuated of air, and a hearth is positioned within the chamber for supporting the metallic material to be melted. Also, a plasma arc torch is mounted to the heating chamber, which is operable in the transfer arc mode wherein an arc extends from the rear electrode of the torch to the hearth. The rear electrode of the torch is of elongate tubular configuration, which permits a major portion of the length of the arc to be located within the torch itself, which permits the torch to deliver a high level of power in the vacuum environment within the heating chamber.

Abstract: An apparatus and method for heating a metallic melt with plasma torches is disclosed which is characterized by its ability to reduce the amount of contamination that is introduced into the metallic melt during the heating process. The apparatus and method includes a furnace chamber having a hearth for receiving a metallic melt. Mounted to the furnace chamber are a pair of plasma torches and an external electrode that is adapted to contact the metallic melt contained in the hearth. A separate direct current power supply is provided to operate such plasma torch. During operation of the apparatus, two separate circuits of opposite polarity are established through the metallic melt utilizing the plasma torches and the external electrode in contact with the melt. While these circuits are maintained, the external electrode is withdrawn from contact with the melt, thereby establishing a single series circuit which includes both plasma torches, both power supplies and the metallic melt.

Abstract: An apparatus for starting and maintaining a plasma arc is disclosed, which comprises a plasma arc torch composed of a rear electrode and a front tubular member, with the tubular member acting as a collimator in transfer arc operation or as an electrode in non-transfer arc operation. The power circuit includes a main DC power supply, an electrical pulse generator in series with the plasma torch, and a protective capacitor connected between the main power supply and pulse generator. To initiate the arc, a high voltage pulse is generated by the pulse generator, which has sufficient power to strike an arc which extends from the rear electrode to an external workpiece in the case of transfer arc operation. The main power supply is used only to maintain the established arc, and thus may have a relatively small voltage capacity.

Abstract: As apparatus and method is disclosed which is adapted to melt metallic fines, and which is useful for processing metallic fines into a useful form. The apparatus may also be used in the smelting of metallic oxides, and in combining metals in an alloying process. The disclosed embodiment of the apparatus includes a furnace having a hearth, a pair of tubular residence chambers each extending upwardly from the hearth, a first plasma torch mounted at the upper end of each residence chamber, and a second plasma torch mounted for heating the material on the hearth. The powdered or granular material is fed into the upper end of each residence chamber, such that the material is at least partially melted from the heat of the first torch while falling through the residence chamber, and the material is further heated and completely melted on the hearth by the second torch.

Abstract: A plasma arc heating apparatus is disclosed which is adapted for heating large quantities of air for commercial and industrial uses, and which comprises a housing including an elongate heating chamber, a tubular front electrode mounted at one end of the housing, and a plasma arc torch mounted at the other end of the housing. The torch is mounted for movement toward and away from the front electrode and a power supply system is provided for establishing an arc which extends from a rear electrode in the torch through the heating chamber and to the front electrode at the opposite end of the housing. Structure are also provided for introducing a gas to be heated into the chamber between the torch and the front electrode, and such that the gas is heated by the arc and flows outwardly through the front electrode.

Abstract: A plasma arc torch is disclosed which comprises front and rear coaxially aligned electrodes, and vortex generator for generating a vortical flow of gas, such as air, between the two electrodes. A power supply system is operatively connected to the two electrodes for generating an arc which is adapted to extend axially from the rear electrode through the vortical flow of gas and to an attachment point located on the front electrode. The bore of the front electrode includes a cup-shaped outer end portion which defines a forwardly facing radial shoulder. By proper coordination of the power and gas delivery systems, the arc may be made to attach to the radial shoulder of the front electrode, and such that the erosion of the front electrode occurs along an axial direction rather than a radial direction.

Abstract: A plasma arc torch is disclosed which has the ability to be configured for operation in either the transfer arc mode or the non-transfer arc mode. The torch includes a rear housing section which mounts a rear electrode, a gas vortex generator, and releasable mounting means. The releasable mounting means is adapted to mount either an electrode assembly for operation of the torch in the non-transfer arc mode, or a collimating nozzle assembly for operation in the transfer arc mode. The torch also includes a coolant passageway which is constructed and arranged so as to mate with cooperating passageways in either the electrode assembly or the collimating nozzle assembly, for removing heat from the internal components of the torch.