EP2677046A1 - Furnace and method for electroslag refining - Google Patents

Abstract

The furnace (37) has a base frame (38) comprising supports (39) that bear a furnace head (41). An electrode is arranged at the furnace head such that the electrode is melted in a crucible arranged below the furnace head. A transformer (42) is fixedly arranged at the furnace head and supplies electric power for melting the electrode. The supports are formed in a column-shape to form a bearing plane (40) of the furnace head together with horizontal bearings. A contact device (44) is arranged at the furnace head for transmitting the electric power to the electrode. An independent claim is also included for a method for electroslag remelting.

Description

The invention relates to a furnace and a process for electroslag remelting (ESR), wherein the furnace comprises a frame, wherein the frame supports having a furnace head, wherein on the furnace head, an electrode can be arranged, wherein the electrode in a below the furnace head arranged crucible can be melted, wherein the furnace comprises a transformer which can provide electrical energy for melting the electrode.

In the so-called electroslag remelting process, material electrodes are remelted for the production of blocks of material, the latter being used as semifinished product for producing components of high material quality. With regard to the systems or methods used, a distinction is made between so-called sliding-block systems in which the crucibles, in which the blocks produced by the burning of the electrodes solidify, are provided with a moveable crucible bottom in order to produce such blocks as a continuous strand. In the so-called vertical crucible method, the remelting of the material electrode takes place in one of its length dimensions fixed block, wherein the thereby used crucible is provided with a solid bottom of the crucible. The material electrode is then fed continuously to the crucible by a feed movement. The advancing movement of the material electrode is performed by a furnace head of the furnace, such that the furnace head, on which the material electrode is held, can be moved in the direction of the crucible. Regularly, a movable material electrode is also provided in a sliding-block system. Furthermore, the material electrode can be held on a so-called electrode rod, via which the feed movement takes place.

The electrical energy needed to melt the material electrodes is provided by one or more transformers that can convert a high line voltage and low current into a low voltage at high current. In particular, several transformers can be connected in series one behind the other, in which case only the last transformer which is connected to the electrodes provides the electrical energy or the required current intensity for melting the electrode. These transformers are regularly placed firmly in a transformer house remote from the furnace or in a separate space spaced from the frame of the furnace. It is also known to arrange a transformer on a purpose-built frame or a floor of a building, which surrounds the frame of the furnace, so that the transformer is approximated to the frame of the furnace. Next, the transformer has a relatively large weight, which must also be considered when choosing a location for the transformer. In particular, by a specially designed for the transformer room can be taken into account.

Further, the transformer, which provides the electrical energy for reflowing the electrode, must be connected to the furnace head by a plurality of cables. The cables are at the furnace head in turn connected to a contact device which is connected to the electrode and a bottom plate of the crucible or a generated block so that the electrical energy can be passed through the electrode and the block. The contact device may comprise coaxially arranged rails or tubes relative to the block, which have a comparatively large cross section, so that they do not significantly heat at a passage of the electrical energy. Since the furnace head is moved by a possible movement of the electrode relative to the fixed transformer, the cables between the transformer and the furnace head must be flexible. In particular, a horizontal movement of the cable in a change of the electrode by a horizontal pivoting of the furnace head or the electrode relative to the crucible and also a vertical movement is possible in this context. In particular, in the described, horizontal movement, the cables are twisted in itself. The cables therefore have a comparatively small cross-section, as a result of which the cables heat up considerably during operation of the furnace. It is therefore used a plurality of cables, each equipped with a jacket, which is flowed through by cooling water. Such water-cooled high-current cables have a number of disadvantages in addition to high procurement costs. Thus, the electrical losses are increased by the use of the flexible high-current cables, which deteriorates the efficiency of the furnace due to the increased energy consumption. Furthermore, the water-cooled high-current cables are subject to wear due to the relative movement of the frame and the transformer. Also, the cables, due to the magnetic fields surrounding the cables, can move and beat independently. It is therefore necessary to maintain the cables regularly and replace them if necessary. The same applies to the system required to cool the cables.

The present invention is therefore based on the object of proposing a furnace and a process for electroslag remelting, the more cost-effectively manufactured or can be carried out.

This object is achieved by a furnace having the features of claim 1 and a method having the features of claim 11.

In the electroslag remelting (ESR) furnace of the present invention, the furnace comprises a frame, the frame having supports supporting a furnace head, wherein an electrode may be disposed on the furnace head, the electrode being fusible in a crucible disposed below the furnace head, wherein the furnace comprises a transformer capable of providing electrical energy for reflowing the electrode, the transformer being fixedly attached to the furnace head.

The transformer is defined in particular as a transformer that provides the electrical energy with the appropriate current, which is suitable for melting the electrode. The fixed location of the transformer on the furnace head involves direct placement of the transformer on the furnace head. Consequently, the transformer is located in the immediate vicinity of the electrode and can also follow a possible movement of the furnace head. It is therefore possible to dispense with the use of flexible and thus necessarily water-cooled high-current cables. A power supply to the furnace head is thereby greatly simplified and reduced by the high-current cable electrical losses, resulting in an improvement in the efficiency of the furnace by reducing energy consumption. Also, it is no longer necessary to provide a space specially designed for the installation of the transformer. Although initially incurred increased costs for a design of the frame, as this must carry the transformer, but these costs are offset by the abandonment of the high current cable and the reduced operating costs of the furnace. Overall, this means lower investment and operating costs.

The supports of the frame may be formed pillar-shaped and form together with horizontal supports of the frame at least one supporting plane of the furnace head. Thus, it is possible to form one or more support levels by means of horizontal support, each of which can be committed in the manner of a projectile of service personnel. Further, means of the furnace can be formed on the horizontal supports. Consequently, the furnace head itself may be formed by one or more support levels above the crucible.

Thus, it is particularly advantageous if the transformer is fixedly arranged on the supporting plane. Preferably, the transformer can be arranged on the supporting plane, via which the electrode and the bottom plate of the crucible are supplied with electrical energy. Even with a vertical movement of the electrode relative to the transformer then it no longer requires an insert of flexible cables.

Rather, a contact device for transmitting the electrical energy to the electrode, an electrode rod and / or the bottom plate of the crucible may be formed on the furnace head, wherein the transformer may be arranged immediately adjacent to the contact device. The contact device may have a sliding contact, via which the electrical energy from the transformer can be introduced directly into the electrode. Alternatively, it is also possible to connect an electrode rod with which the electrode can be held on the frame to the contact device. Further, the bottom plate of the crucible via busbars or pipes with a relatively large cross-section may be firmly connected to the contact device.

Also, the transformer may be fixed relative to the contact device. Thus, it is possible to dispense with the development of technically complex current-carrying devices between transformer and contact device.

The transformer can then be connected to the contact device by means of a rigid busbar device. An example formed from simple busbars with a comparatively large cross-section busbar device is particularly easy and inexpensive to produce, in which case a distance of the transformer to the contact device would not even be particularly small.

In one embodiment of the furnace, the furnace head may be designed to be stationary for carrying out the process of electro-slag remelting and the crucible may have a base plate movable relative to the furnace head. The electrode could then still be arranged movably on the furnace head.

On the other hand, the bottom plate may be formed stationary, and the furnace head may be formed to be horizontally movable relative to the crucible.

Alternatively, the crucible may have a stationary bottom plate and the furnace head may be stationary relative to the bottom plate. In a melting of the electrode then the electrode would have to be lowered continuously in the direction of the bottom plate. However, this does not exclude that the electrode may also be movable relative to the furnace head. A relative mobility of the electrode to the furnace head, in particular in the horizontal direction, may always be required when the furnace is equipped with the electrode and this must be introduced, for example, from above into the crucible.

The furnace may be an electric slag remelting furnace under vacuum, under inert gas, under an air atmosphere or under pressure. Thus, it becomes possible to use the advantageous arrangement of the transformer for various furnaces for electroslag remelting.

In the inventive method for electroslag remelting (ESR) with an oven, the oven comprises a rack, the rack having supports supporting a furnace head, the oven head being an electrode is arranged, wherein the electrode is melted in a crucible arranged below the furnace head, wherein the electrode is melted by a feed movement of the electrode into the crucible, wherein the furnace comprises a transformer which provides electrical energy for melting the electrode, wherein the Transformer is moved together with the furnace head.

In particular, the fact that the transformer is moved together with the furnace head, there is the advantage that can be dispensed with flexible high-current cable. For the resulting advantages, reference is made to the preceding description of the furnace according to the invention.

Further advantageous embodiments of the method will become apparent from the feature descriptions of the dependent claims back to the device claim 1.

Hereinafter, a preferred embodiment of the invention will be explained in more detail with reference to the accompanying drawings.

Fig. 1:

ein Ofen zum Elektroschlackeumschmelzen in einer Seitenansicht nach dem Stand der Technik;

Fig. 2:

ein Ofen zum Elektroschlackeumschmelzen in einer Seitenansicht nach einer Ausführungsform der Erfindung.

Show it:

Fig. 1:

an electric slag remelting furnace in a side view of the prior art;

Fig. 2:

an electric slag remelting furnace in a side view according to an embodiment of the invention.

Fig. 1 FIG. 10 shows an electroslag remelting (ESU) furnace 10 under inert gas according to the prior art. A frame 11 forms a support plane 12 of a furnace head 13, wherein the support plane 12 and the furnace head 13 is mounted on supports 14. The furnace head 13 comprises a feed drive 15 for an electrode 16 with a spindle 17 and an electrode suspension 18 and an electrode rod 19 which connects the electrode 16 to the electrode suspension 18. Continue to be formed by the frame 11, two accessible platforms 20 and 21. Below the furnace head 13, a crucible 22 is arranged, in which an ingot 23 and a molten bath 24 are already located. A bottom plate 25 of the crucible 22 is stationary, that is, fixedly arranged on a foundation 26. Next, a protective gas chamber 27 is formed above the crucible 22, which allows melting of the electrode 16 under inert gas. In a separate space 28 shown here only in sections, a transformer 29 for providing electrical energy is arranged, which is connected via a passage opening 30 in a wall 31 with a mounting space 32 for the frame 11. In particular, the transformer 29 is connected by means of water-cooled high-current cable 33 via a contact device 34 with the electrode 16 and the crucible 22. On the crucible 22 busbars 35 are arranged coaxially thereto. Further, located on the electrode rod 19, a sliding contact 36 of the contact device 34 for transmitting the electrical energy to the electrode 16. Lowering of the electrode 16 in the crucible 22 is now at least partially effected by lowering the electrode suspension 18, so that the electrode 16 relative to Transformer 29 is moved. For fitting the furnace head 13 with a new electrode 16, it is necessary to pivot the frame 11 horizontally relative to the transformer 29. This is done by a rotation about one of the supports 14, whereby the high-current cable 33 are also rotated.

Fig. 2 shows an embodiment of an electroslag remelting furnace (ESU) 37 according to the invention. In particular, however, neither a crucible nor an electrode is shown here. The furnace 37 corresponds in its essential structure to that in the Fig. 1 above-described oven. In contrast, a supporting plane 40 is formed on a frame 38 of the furnace 37 above supports 39. On the support plane 40 and thus on a furnace head 41 of the furnace 37, a transformer 42 is arranged directly and rigid busbars 43 with a comparatively large cross-section with a Contact device 44 is connected, which in turn is connected to the electrode and the crucible, not shown here. The known from the prior art high-current cable can thus be replaced inexpensively by simply trained busbars 43. This is possible only by the arrangement of the transformer 42 on the furnace head 41.

Claims (11)

Electric-wire-melting furnace (37), the furnace comprising a frame (38), the frame having supports (39) carrying a furnace head (41), wherein an electrode can be arranged on the furnace head, the electrode being in a below can be melted, the furnace comprising a transformer (42), which can provide electrical energy for melting the electrode,
characterized,
that the transformer is fixed to the furnace head. Oven according to claim 1,
characterized,
in that the supports (39) are of pillar shape and together with horizontal supports form at least one support plane (40) of the furnace head (41). Oven according to claim 1 or 2,
characterized,
that the transformer (42) on the support plane (40) is fixedly arranged. Oven according to one of the preceding claims,
characterized,
in that a contact device (44) for transmitting the electrical energy to the electrode, an electrode rod and / or a bottom plate of the crucible is formed on the furnace head (41), wherein the transformer (42) is arranged immediately adjacent to the contact device. Oven according to claim 4,
characterized,
in that the transformer (42) is fixed relative to the contact device (44). Oven according to claim 4 or 5,
characterized,
in that the transformer (42) is connected to the contact device (44) by means of a rigid busbar device (43). Oven according to one of the preceding claims,
characterized,
that the furnace head is stationary, and the crucible has a bottom plate movable relative to the furnace head. Oven according to one of claims 1 to 6,
characterized,
that the bottom plate is stationary, and the furnace head (41) is designed to be horizontally movable relative to the crucible. Oven according to one of claims 1 to 6,
characterized,
that the crucible has a stationary bottom plate, and the furnace head is stationary relative to the bottom plate. Oven according to one of the preceding claims,
characterized,
in that the furnace (37) is designed for electroslag remelting under vacuum, under inert gas, under air atmosphere or under pressure. A process for electroslag remelting with a furnace (37), the furnace comprising a frame (38), the frame having supports (39) carrying a furnace head (41), wherein an electrode is placed on the furnace head, the electrode being in a crucible arranged below the furnace head is melted, wherein the electrode is melted by a feed movement of the electrode into the crucible, the furnace comprising a transformer (42) which provides electrical energy for melting the electrode,
characterized,
that the transformer is moved together with the furnace head.

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