Melting plant and method

Abstract

Melting plant having a melting chamber which by way of a gas protection hood is separated from the environment, wherein the gas protection hood or another part of the melting chamber encasement has a lead through in which an electrode rod for moving an electrode to be melted is guided in a gas-tight manner by way of a sealing means. Hydraulic or pneumatic equalisation means, for exerting on the electrode rod equalisation forces which are in a proportional correlation with the gas pressure prevailing within the melting chamber are provided so as to compensate for the gas-pressure forces acting on the electrode rod.

Claims

1. A melting plant having a melting chamber which by way of a gas protection hood is separated from the environment, wherein the gas protection hood has a lead through in which an electrode rod for moving an electrode to be melted is guided in a gas-tight manner by way of a sealing means, wherein hydraulic or pneumatic equalization means, for exerting on the electrode rod equalization forces which are in a proportional correlation with the gas pressure prevailing within the melting chamber are provided so as to compensate for the gas-pressure forces acting on the electrode rod, wherein a drive unit for moving the electrode rod is connected to the upper end of the electrode rod, wherein the drive unit comprising a drive spindle which engages with the electrode rod and wherein the drive spindle is provided with an external thread and engages with a corresponding internal thread of the electrode rod.

2. The melting plant according to claim 1, wherein the equalization means are specified such that compensation forces which correspond to a positive pressure as well as to a negative pressure in the melting chamber are capable of being exerted.

3. The melting plant according to claim 1, wherein the drive unit by way of at least one guide is connected to a lower traverse, and the lower traverse is connected to stationary cylinder portions of the equalization means, and an upper traverse is connected to both the electrode rod as well as to movable piston portions of the equalization means.

4. The melting plant according to claim 1, wherein the drive unit for driving the electrode rod is coupled to a frame and forces or momentums which result from weights of the electrode rod and from a received electrode are capable of being dissipated to the environment by way of the frame, the frame being embodied so as to be independent of the gas protection hood.

5. The melting plant according to claim 1, wherein a plurality of equalization means are disposed so as to be offset radially from the central axis of the electrode rod and so as to be symmetrically disposed such that the generation of the tilting momentum or of a torque on the electrode rod is avoidable in the activation of the equalization means.

6. The melting plant according to claim 1, wherein the equalization means have a piston/cylinder arrangement, and the sum of the effective cross sections of the individual pistons of the equalization means is largely identical to the cross-section of the electrode rod.

7. The melting plant according to claim 1, wherein an oil container communicates pneumatically with the melting chamber and is hydraulically connected to the equalization means.

8. A method for operating an electrode melting plant, in which an electrode rod moves an electrode in a melting chamber and the melting chamber is sealed in a gas-tight manner in relation to the environment, a drive unit is disposed outside the melting chamber and drives the electrode rod, the resulting forces on the electrode rod that result both at a positive pressure as well as negative pressure in the melting chamber being equalized by at least one equalization cylinder which in terms of fluid technology communicates with the melting chamber, wherein a drive unit for moving the electrode rod is connected to the upper end of the electrode rod, wherein the drive unit comprising a drive spindle which engages with the electrode rod and wherein the drive spindle is provided with an external thread and engages with a corresponding internal thread of the electrode rod.

Description

DESCRIPTION OF THE FIGURE

(1) An advantageous embodiment of the plant is illustrated in the appended FIG. 1.

(2) The construction shown in FIG. 1 comprises a frame 10, a gas protection hood 20 in the form of a gas-tight cylinder, a lead through 30 in the upper end of the gas protection hood 20, an electrode rod 40 which by way of the lead through 30 is introduced into the gas protection hood 20 in a pressure-tight or vacuum-tight manner, respectively, a drive unit 50 which can move the electrode rod 40 vertically upwards or downwards in the gas protection hood 20, a melting station 60 in which the re-melting process of the electrode 70 that is suspended from the electrode rod 40 takes place, and a weighing installation 80 which is provided for regulating the process.

(3) The drive unit 50 is disposed directly above the electrode rod 40 and by way of the guides 41 and 42 is vertically connected to the weighing installation 80, wherein a drive spindle 130 is suspended inside the interior 40.1 of and coaxially to the electrode rod 40. The drive unit 50 is supported in an articulated manner laterally on the frame 10. The frame 10 is embodied so as to be pivotable and can transfer the entire system of the gas-tight gas protection hood 20 conjointly with the electrode rod 40, the drive unit 50, and the weighing installation 80, from the melting station 60 shown to a further melting station (not shown).

(4) Two equalization cylinders 140 are disposed on either side of the electrode rod 40, the piston-rod chambers 200 of said equalization cylinders 140 by way of lines 150 and an oil container 160 being connected to the gas chamber 190 of the gas-tight hood 20. The gas chamber 190 hereunder is also referred to as the melting chamber 190.

(5) The electrode rod 40 in an upper region as well as in a lower region and in each case by way of one traverse 170 and 180 is connected in an articulated manner to the equalization cylinders 140, wherein the piston rods 210 of said equalization cylinders 140 are connected in an articulated manner directly to the upper traverse 170 at the upper end of the electrode rod 40, and the equalization cylinders 140 are also connected in an articulated manner to the lower traverse 180 such that the lower traverse 180 comprises the upper end of the gas-tight lead through 30 and, on the other hand, is fastened in an articulated manner to a weighing frame of the weighing installation 80.

(6) The functioning of the plant is described as follows. As soon as a pressure differential is created between the interior chamber of the vessel, that is to say the melting chamber 190, and the atmosphere, for example by way of an intake or a discharge of gas, said pressure differential by way of the gas lines 150 is transmitted into the oil tank 160. Oil from the oil tank flows into the equalization cylinders 140 and, on account of the sum of the piston-ring areas of the two equalization cylinders 140 being equal to the sealed cross-sectional area of the electrode rod 40, two mutually cancelling forces are created. Said two forces are the compressive force on the electrode rod 40 in the case of pressure in the vessel in the direction from the inside to the outside, that is to say from the bottom to the top, and the compressive force on the piston faces of the cylinders in the direction from the top to the bottom. An equalization force from the electrode rod 40 is transmitted by way of the two traverses 170 and 180 into the piston rods 210 of the cylinders 140, and the injection force of the electrode rod 40 is compensated for by the two laterally acting cylinder forces. On account thereof, the remainder of the plant construction remains unstressed by the forces that are created by the pressure differential.

(7) The advantages of this arrangement are as follows: All forces which are initiated by the pressure differential between the atmospheric pressure and the vessel interior are enclosed in the electrode rod system and do not have any effect on the remainder of the plant. The drive spindle of the electrode rod can be conceived as is the case in a conventional plant which operates only under atmospheric conditions. All melting regulators of the plant controller can remain unchanged in the case of application conditions at a variable melting-chamber pressure since the forces that are initiated by pressure do not act on the drive of the electrode rod and on account thereof, do not play any part in the output of the drive. The system functions in an identical manner in both directions, i.e. at an internal pressure (positive pressure) the same as at a negative pressure (for example also a vacuum) in the melting chamber 190. On account of the gas pressure not being induced directly into the equalization cylinders 140 but first into the oil tank 160 which is interdisposed between the melting chamber 190 and the equalization cylinders 140, said gas pressure is converted to an oil pressure. Since the friction conditions for the application in both cylinders are relatively similar, no additional synchronization or equalization of the friction forces existing therein is required. The slag dust that is created in the plant is caught in the oil and is only disposed of by an oil change; there is no risk of the poisonous slag and metal dust being inadvertently dispersed into the environment. The construction of the equalization system is simple and can be implemented without sizeable modification measures in almost all plants that have already been built.

(8) The equalization cylinders 140 are aligned vertically such that the piston rods 210 thereof are offset radially from the electrode rod 40. The cylinders of the equalization cylinders overlap at least partially in the radial direction in relation to the electrode rod 40. Alternatively, to the two equalization cylinders 140 shown, a larger number of equalization cylinders of this type can be used, the latter preferably being distributed uniformly about the central axis of the electrode rod 40 so as to avoid unequal momentums on the electrode rod 40.

(9) As has been described above and schematically illustrated in FIG. 1, the frame 10 is preferably rotatable about the vertical axis thereof. Proceeding from the frame 10, a further melting station (not shown) can be disposed so as to be opposite the melting station 60 shown. On account thereof, the restocking time for the plant after an electrode 70 has been melted down can be significantly reduced.

(10) On account of the embodiment shown in which the drive spindle 130 is located within the electrode rod 40 it is possible for the (cylindrical) external surface of the electrode rod 40 to be designed so as to be largely flat and smooth. Since the sealing in relation to the gas protection hood 20 takes place on this face, the complexity in terms of sealing is reduced significantly, or the quantity of the gas that exits or enters, respectively, through the seal is significantly reduced. Tightness is important specifically in the operation of the plant at negative pressure since disadvantageous oxidation processes can otherwise arise on the melt.

LIST OF REFERENCE SIGNS

(11) 10 Frame 20 Gas protection hood 30 Lead through 40 Electrode rod 41, 42 Guides 50 Drive unit 60 Melting station 70 Electrode 80 Weighing installation 130 Drive spindle 140 Equalization means 150 Lines 160 Oil container 170 Upper traverse 180 Lower traverse 190 Melting chamber 200 Piston rod chamber 210 Piston