Patent Application
20130336353
This application claims the priority benefit of German Patent Application No. 10 2012 210 281.7 filed on Jun. 19, 2012, which is fully incorporated herein by reference.
Not applicable.
The invention relates to a furnace and method for electroslag remelting (ESR), wherein the furnace comprises a base frame, wherein the base frame comprises supports which bear a furnace head, wherein at the furnace head, an electrode can be disposed, wherein the electrode can be melted on in a crucible disposed below the furnace head, wherein the furnace comprises a transformer which can supply electric power for melting on the electrode.
With the so-called electroslag remelting process, material electrodes are remelted for producing material blocks, wherein the latter serve as semi-finished products for producing components having a high material quality. With respect to the installations or methods used in this context, so-called sliding crucible installations are distinguished with which the crucibles, in which the blocks generated by burning down the electrode solidify, are provided with a displaceable crucible bottom in order to produce such blocks, so to speak, as a continuous strand. With the so-called stationary crucible method, remelting of the material electrode is effected in a block whose longitudinal dimensions are fixed, wherein the crucible used here is equipped with a fixed crucible bottom. Subsequently, the material electrode is continuously fed to the crucible by means of a feed movement. The feed movement of the material electrode is performed by a furnace head of the furnace in such a manner that the furnace head, at which the material electrode is mounted, can be moved toward the crucible. With sliding crucible installations, too, a movable material electrode is provided on a regular basis. Furthermore, the material electrode can be mounted at a so-called electrode rod, via which the feed movement is effected.
The electric power required for melting on the material electrodes is subsequently supplied by one or more transformers which can transform a high network voltage and a low amperage into a low voltage with a high amperage. For this, multiple transformers can be connected in series in particular, wherein only the last transformer, which is connected to the electrodes, supplies the electric power or the required amperage for melting on the electrode. Said transformers are regularly fixedly installed in a transformer station separate from the furnace or in a room spaced apart and detached from the base frame of the furnace. It is also known to dispose a transformer in such a way on a base frame formed specially for this purpose or on a level of a building, which surrounds the base frame of the furnace, that the transformer is brought closer to the base frame of the furnace. Furthermore, the transformer has a comparatively high weight, which also has to be taken into account when selecting an installation site for the transformer. In particular by means of a room specially formed for the transformer, this can be taken into account.
Furthermore, the transformer which supplies the electric power for melting on the electrode has to be connected to the furnace head by means of a plurality of cables. At the furnace head, the cables are again connected to a contact device which is connected to the electrode and a bottom plate of the crucible or of a generated block in such a way that the electric power can be conducted through the electrode and the block. Here, the contact device can comprise bars or tubes which are disposed coaxially relative to the block and which have a comparatively large cross-section, such that they do not heat up significantly when the electric power is conducted through. Since the furnace head is moved relative to the fixedly installed transformer by means of a potential movement of the electrode, the cables between the transformer and the furnace head have to be formed flexible. In particular, a horizontal movement of the cables is effected when the electrode is exchanged by means of a horizontal swiveling of the furnace head or of the electrode relative to the crucible, and a vertical movement is also possible in this context. In particular with the described horizontal movement, the cables are twisted. Therefore, the cables have a comparatively small cross-section, whereby the cables heat up considerably during operation of the furnace. Therefore, a plurality of cables is used which each feature a coating through which cooling water flows. Apart from high acquisition costs, such water-cooled high-current cables have a number of disadvantages. For instance, the electrical losses are increased by using the flexible high-current cables, which impairs the efficiency of the furnace as a consequence of the higher power consumption. Furthermore, the water-cooled high-current cables are subject to wear and tear due to the relative movement of the base frame and the transformer. The cables can also move on their own due to magnetic fields surrounding the cables and can knock against each other. Therefore, it is necessary to maintain the cables regularly and, if necessary, to exchange them. The same applies for the installation required for cooling the cables.
The present invention is based on the task to propose a furnace as well as a method for electroslag remelting which can be produced and performed, respectively, in a more cost-effective way.
With the furnace for electroslag remelting (ESR) according to the invention, the furnace comprises a base frame, wherein the base frame has supports which bear a furnace head, wherein at the furnace head, an electrode can be disposed, wherein the electrode can be melted on in a crucible disposed below the furnace head, wherein the furnace comprises a transformer which can supply electric power for melting on the electrode, wherein the transformer is fixedly disposed at the furnace head.
Here, the transformer is in particular defined as a transformer which supplies the electric power with the corresponding amperage which is suitable for melting on the electrode. Disposing the transformer at the furnace head in a fixed manner includes directly disposing the transformer at the furnace head. Consequently, the transformer is disposed in close proximity to the electrode and can also follow a potential movement of the furnace head. Therefore, flexible and consequently necessarily water-cooled high-current cables do not have to be used. A current supply to the furnace head is considerably simplified in this way and the losses caused by the high-current cables are reduced, which results in an improvement in the efficiency of the furnace due to a reduction of the power consumption. Neither is it still necessary to provide a room specially formed for installing the transformer. Although, initially, there are higher costs for forming the base frame since it has to bear the transformer, these costs are outweighed by sparing the high-current cables and by the reduced operating costs. All in all, thus lower investment and operating costs are incurred.
The supports of the base frame can be formed column-shaped and can form at least one bearing plane of the furnace head together with horizontal bearings of the base frame. In this way it becomes possible, by means of horizontal bearings, to form one or more bearing planes which can be walked on by service personnel like levels. Furthermore, devices of the furnace can be formed at the horizontal bearings. Consequently, the furnace head itself can be formed by one or more bearing planes above the crucible.
Thus, it is particularly advantageous if the transformer is fixedly disposed on the bearing plane. Preferably, the transformer can be disposed on the bearing plane via which the electrode and the bottom plate of the crucible are supplied with electric power. Even with a vertical movement of the electrode relative to the transformer, it is not necessary anymore to use flexible cables.
Instead, at the furnace head, a contact device for transmitting the electric power to the electrode, an electrode rod and/or the bottom plate of the crucible can be formed, wherein the transformer can be disposed directly adjacent to the contact device. The contact device can include a sliding contact via which the electric power can be conducted from the transformer directly into the electrode. Alternatively, it is also possible to connect an electrode rod, by means of which the electrode can be mounted at the base frame, to the contact device. Furthermore, the bottom plate of the crucible can be fixedly connected to the contact device via busbars or tubes with a comparatively large cross-section.
The transformer can also be fixedly disposed relative to the contact device. In this way, it is not necessary to form technically complex current conducting devices between the transformer and the contact device.
Subsequently, the transformer can be connected to the contact device by means of a rigid busbar device. For instance, a busbar device formed from simple busbars with a comparatively large cross-section can be produced particularly easily and inexpensively, wherein in this case, a distance of the transformer to the contact device would not even have to be particularly small.
In one embodiment of the furnace, the furnace head for performing the method for electroslag remelting can be formed stationary, and the crucible can have a bottom plate which is movable relative to the furnace head. Here, the electrode could be movably disposed at the furnace head nevertheless.
In contrast, the bottom plate can be formed stationary, and the furnace head can be formed horizontally movable relative to the crucible.
Alternatively, the crucible can have a stationary bottom plate and the furnace head can be formed stationary relative to the bottom plate. When the electrode is melted off, the electrode would then have to be lowered continuously toward the bottom plate. This does not preclude, however, that the electrode can also be movable relative to the furnace head. A relative movability of the electrode with respect to the furnace head, in particular in the horizontal direction, can be required in such cases when the furnace is fitted with the electrode and the latter has to be inserted into the crucible from above, for instance.
The furnace can be a furnace for electroslag remelting under vacuum, under inert gas, under air atmosphere or under pressure. In this way, it becomes possible to use the advantageous disposition of the transformer for different furnaces for electroslag remelting.
With the method for electroslag remelting (ESR) with a furnace according to the invention, the furnace comprises a base frame, wherein the base frame comprises supports which bear a furnace head, wherein at the furnace head, an electrode is disposed, wherein the electrode is melted on in a crucible disposed below the furnace head, wherein the electrode is melted on into the crucible by means of a feed movement of the electrode, wherein the furnace comprises a transformer which supplies electric power for melting on 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 has the advantage that flexible high-current cables are not required. Regarding the advantages resulting therefrom, reference is made to the preceding description of the furnace according to the invention.
Further advantageous embodiments of the device and method arise from the descriptions of the features of the device disclosed herein.
In the following, a preferred embodiment of the invention is described in more detail with reference to the attached drawing.
In the figures:
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 210 281.7 | Jun 2012 | DE | national |
