Bbc Brown, Boveri & Company, Limited

Karl Buhler

Anton Menth

Heinz Baltensperger

Enrico Borinelli

Karl Oldani

Werner Schott

To assure a high degree of operating reliability during operation of pot furnaces, their bath electrode (2, 14, 17, 20) in the pot (1) must be cooled intensively by external cooling. If the pot (1) is in the pot furnace station, cooling of the bath electrode (2, 14, 17, 20) is not a problem. But the case is different when the pot (1) is transported to various stations which can be geographically far apart--e.g., on the one hand, to a melting furnace and, on the other hand, to a continuous casting machine. In the latter case, feed and removal devices for a coolant have been constantly carried with the pot (1). However, this makes a considerable expense necessary. By the dimensioning according to the invention of the bath electrode (1, 14, 17, 20) and/or by attachment of additional cooling bodies (15, 18, 22, 14), the bath electrode (2, 14, 17, 20) can be successfully uncoupled from external cooling (8, 9, 10) over the relatively long handling period that is necessary for operational requirements. By the steps according to the invention, the bath electrode (2, 14, 17, 10) can be kept under the critical temperature during the period of uncoupling from the cooling (8, 9, 10), e.g., in the area of its electric connection (11). Moreover, by said steps the liquid/solid boundary layer between the melt (4) and the front surface of the bath electrode (2, 14, 17, 20) can be kept stable in position at the end of the preset time of the uncoupling in comparison with the beginning of the uncoupling.

Bath electrode for pot furnace

Bottom electrodes (6) of direct current arc furnaces, especially during the overheating phase of the melting process, are subjected to very high thermal stresses. As a result of a melting bath flow brought about by electromagnetic forces, the heat supply from the overheated melting bath (13) to the bottom of the electrode(s) (6) is increased still further. This is manifested in a melting back of the metallic component (6') of the bottom electrode in the direction of the furnace crucible base (4). When both the metallic component (6') and the non-metallic refractory component (7') of the bottom electrode (6) are arranged in the direction of the electromagnetic field, that is, in the peripheral direction of the bottom electrode (6), the length (l) of the electrode component is greater than its width (b). Moreover, two zones form in the operating condition of the furnace; namely, an upper, non-metallic zone (7'), which is formed by the apex (7') of dams (7) projecting into the melting bath (13), and a lower zone, which is formed by the slightly melted-back, metallic component (6'). In this way, the metallic component (6') of the bottom electrode (6) is directly protected from the bath flow, and the intensive heat exchange between the melting bath (13) and the bottom electrode (6) is reduced. By inserting non-metallic, refractory components (7) into the bottom electrode, the periphery or diameter of the latter is increased. This measure reduces the electromagnetic field strength in the transition area from the bottom electrode (6) into the melting bath (13), and consequently an additional reduction in the melting bath flow is achieved at the same time.

Bottom electrode for a direct current arc furnace

The shape of the furnace hearth (20) in the area of the bottom electrode (6) is defined within limits given by exponential functions, with minimum and maximum values being given for the ratio of the cross section (A.sub.L) of the melting bath (13) to the cross section (A) of the bottom electrode (6) in its melting bath contact surface (6', 7'). The electrode is designed in the shape of a truncated cone, with the cone surface enclosing an angle of at least 20.degree. with the melting bath contact surface. The trumpet-shaped or conical widening of the furnace hearth surface (20) in the area of the bottom electrode makes possible a continuous transition of the current and of the electromagnetic field in this area, by which means the bath movement near to the melting bath contact surface (6', 7') of the bottom electrode (6) is also reduced. The arrangement of the bottom electrode (4) in a protuberance of the furnace hearth (20) protects the bottom electrode (6) from the flow spreading throughout the entire melting bath (13). Moreover, only one metal sump is required in the protuberance in order to initiate a subsequent melting process, and not, as in normal practice, a metal sump which extends over the entire furnace hearth surface (20).

Bottom electrode arrangement for an electric furnace

To counteract the danger of the penetration of coolant in the use of a liquid-cooled device for cooling of vessel walls (27) for arc furnaces (1) and the serious consequences resulting therefrom, a pressure is created in the coolant in the thermally highly burdened cooling elements (36) which is lower than that of the ambient atmospheric pressure.

Process and device for the cooling of furnaces

An apparatus for converting an arc furnace installation from three-phase operation to d.c. operation wherein in order to ensure optimum d.c. operation after converting the three-phase arc furnace installation to d.c. operation, while retaining the three-phase furnace transformer and the high-voltage switchgear, there is connected an adaptation member (2, 7) for adjusting the arc voltage and/or for increasing the inductive reactance, in addition to the actual rectifier arrangement. This adaptation member is formed of a transformer, preferably an autotransformer, and/or a choke circuit.

Apparatus for converting a three-phase arc furnace to d.c. operation

A direct-current electric arc furnace for melting metals, including a furnace vessel and at least a pair of electrodes, wherein a bottom electrode is mounted in the bottom of the furnace vessel. In order to be able to remove the bottom electrode, the cross-section of which tapers towards the interior of the furnace vessel, from the outside in the direction of the furnace vessel interior, the bottom electrode is provided with a molded body of a refractory material. The molded body envelopes the bottom electrode and in combination therewith forms an electrode unit. This electrode unit in turn has a cross-section which expands in the direction of the furnace vessel interior or at the most remains the same. In this way, extensive work can be saved by removing the bottom electrode from outside into the interior of the furnace. Removal of the bottom electrode is also facilitated by the fact that neither a connecting piece for applying power to the electrode and for cooling thereof nor the electric feedlines thereto need be removed.

Bottom-electrode arrangement for a direct-current arc furnace

A direct-current electric arc furnace for melting metals including a furnace vessel and at least a pair of electrodes, wherein a bottom electrode is mounted in the bottom of the furnace vessel. In order to be able to provide good cooling for the bottom electrode, a connecting piece directly or indirectly cooled is provided in contact with the bottom electrode and serves as a contact sleeve. The contact surfaces of the connecting piece expand conically in the direction of the furnace vessel bottom. By pairing the external truncated cone of the bottom electrode with the internal truncated cone of the connecting part, a proper electric and thermal contact is made between the two parts. In addition, the contact sleeve is provided with cooling ducts for a liquid cooling system which further enhances the cooling effect.

Cooling arrangement of a bottom electrode for a direct-current arc

A direct-current electric arc furnace for melting metals, including a furnace vessel and a bottom electrode mounted in the bottom of the furnace vessel. To prevent molten metal from contacting with current-carrying and liquid-cooled parts of the bottom electrode in the event of an unforeseen break-out of the furnace vessel bottom of the electric furnace, a shielding roof is provided as a guard between the furnace vessel bottom and the current-carrying and liquid-cooled parts. The shielding roof is formed in the shape of a truncated cone and is open downwards. The shielding roof is preferably rigidly joined to the furnace vessel bottom and is formed at least in part with a roof made of refractory material.

Guard arrangement for a bottom electrode of a direct-current arc furnace

Arc furnace has a furnace shell, a furnace lid with lid ring and a lid lifting and swivelling means as well as a lid opening in the furnace lid for exhausting the flue gas from the interior of the furnace and a flue gas exhaust nozzle for removing the flue gases above the lid opening, the nozzle being supported on the furnace lid ring. By means of this design feature as well as a guide arrangement and a locking means the flue gas exhaust nozzle can be completely integrated into the operating steps of the arc furnace in a simple and economical fashion.

Gas exhaust nozzle for arc furnaces

A tiltable arc furnace with a platform (5) supported on rolling-contact cradles (10) is designed so that the furnace shell (2) resting on a mobile carriage (6) can be moved approximately one furnace length on the platform (5) transversely to the pouring direction. The platform (5) is prolonged at one end and provided with appropriate travelling lines (8) comprising rails (9). As a result, a structure of unitary design is achieved, the tilting moments are limited to low values and expensive blocking and stopping systems can be omitted.

Tiltable arc furnace

A method and apparatus for lifting and swivelling a cover of a furnace away from a cauldron of the furnace is disclosed. The apparatus includes a longitudinally moveable and rotatable column housed in a cylinder. A bar, having a longitudinal axis which is substantially parallel to a longitudinal axis of the column, is spaced apart from, and connected to, the column. A plate with an aperture is connected to an upper end of the cylinder. The bar may move through the aperture in the plate when the longitudinal axis of the bar is aligned with a center of the plate. A double-acting hydraulic cylinder is mounted on the plate. The cylinder includes a piston rod which is connected to a pivot head. The pivot head encircles the bar.

Lifting and swivelling device

In order to move a furnace body (1) and a furnace lid (2) relative to one another by approximately one furnace body width, the separating surfaces of the furnace body (1) and furnace lid (2) are inclined relative to the horizontal. The direction of movement when the furnace body (1) is moved then runs in the direction of the angle opening and, when the furnace lid (2) is moved, the movement is in the opposite direction. In order to reduce the frictional forces between the separating surfaces (4, 5) of the furnace body (1) and furnace lid (2) and to ensure that the relative movement of the furnace body (1) and the furnace lid (2) occurs under defined conditions, the furnace lid (2) is supported on at least two support points on the furnace body (1) on which roller tracks (6) are arranged together with support rollers (7) which roll on the tracks for a certain travel. When opening the furnace body (1) and furnace lid (2), the weight of the furnace lid (2) is by this mechanism first partially, then completely transferred to the lid carrying and swivelling device (10, 42) and, when closing the furnace body (1) and furnace lid (2), the weight of the furnace lid (2) is similarly first transferred partially and then completely transferred to the furnace body (1).

Inclined arrangement of the support surfaces of a furnace body and

A liquid cooling system for thermally highly stressed parts of an industrial furnace consists of cooling channels, arranged essentially vertically and through which liquid flows and by-pass openings arranged at the upper end of the cooling channels for the direct passage of cooling liquid, by-passing the cooling channels. According to the dimensions of the by-pass openings, steam or gas bubbles are removed from the cooling system in a simple fashion and, at the same time, the cooling liquid which passes through the cooling channels and is heated is cooled by the cooling liquid flowing directly through the by-pass openings, before it again enters the next cooling channels. The by-pass opening(s) are formed by connecting tubes, or they are arranged in a cooling liquid distribution chamber, into which the cooling channels pass. With this liquid cooling arrangement, a practically unlimited number of cooling channels can be arranged in series, the cooling channels being formed in various fashions and being adaptable to the respective shape fo the furnace parts to be cooled, depending on the intended application.

Liquid cooling arrangement for industrial furnaces

A liquid cooled cover for an electric furnace, wherein in order to lengthen the service life of the thermally highly stressed cover, cooling pipes are located essentially parallel and approximately vertically to the furnace tipping direction at a predetermined distance from each other. The cooling pipes are embedded in a fireproof construction material (57, 57') and constitute its reinforcement. The cooling liquid is supplied and removed exclusively via a cover ring, which is constructed as a cooling liquid distributing conduit in the periphery of the cover and which provided with integrated bypass openings. The composite construction of cooling pipes and fireproof construction material achieves a high thermal and mechanical stability of the furnace cover and the cooling system is largely removed from altering temperature stresses.

Liquid-cooled cover for arc furnaces

An electric furnace including a furnace vessel having modular thermally stressed wall parts, wherein in order to lengthen the service life of the thermally stressed wall parts of furnaces, cooling pipe layers are provided with the cooling pipes of the inner layer located in a fireproof construction material (35). These cooling pipes form the reinforcement for the fireproof construction material. The inner layer of cooling pipes face the inside of the vessel and are made in one piece, U-shaped at the upper and the lower and lead into the outer layer of cooling pipes. The outer layer of cooling pipes empty into a liquid distributing conduit provided with at least one integrated bypass openings whereby cooling liquid is at least partially short-circuited between pipes in the outer layer. The cooling pipe is thermally stressed and relieved in a homogeneous manner by the one-piece construction of the cooling pipes facing the inside of the vessel, by U-shaped transitions to the outer cooling pipe and by the avoidance of welding seams and other material connections in the cooling pipe, so that thermal stresses in the cooling system are almost excluded and the cooling system is largely freed from the effects of alternating temperature stresses.

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Nussbaumen, Switzerland

Karl Buhler