MELTING UNIT FOR MELTING DOWN CASTING MATERIALS AND METHOD FOR PRODUCING MOLTEN MATERIAL FOR CASTINGS

Abstract

A melting unit for melting down casting materials and a method for producing molten material for casting.

Claims

1. A melting apparatus for melting casting materials, comprising: a first furnace vessel configured for melting casting materials and for accommodating melt formed by melting; and a second furnace vessel located downstream of the first furnace vessel such that melt formed from casting materials in the first furnace vessel can be conducted into the second furnace vessel; wherein the second furnace vessel his configured for accommodating the melt which can be conducted from the first furnace vessel into the second furnace vessel and for increasing the temperature of the accommodated melt to the casting temperature for this melt.

2. The melting apparatus as claimed in claim 1, wherein the first furnace vessel inductively heatable.

3. The melting apparatus as claimed in claim 1, wherein the second furnace vessel is inductively heatable.

4. The melting apparatus as claimed in claim 1, wherein the melting apparatus is configured for conducting the melt heated to casting temperature in the second furnace vessel into a treatment or casting device.

5. A process for producing a melt for casting using the melting apparatus of claim 1, wherein the process comprises: introducing solid casting material into the first furnace vessel; melting the casting material in the first furnace vessel; conducting the melt formed in the first furnace vessel into the second furnace vessel; and increasing the temperature of the melt accommodated in the second furnace vessel to the casting temperature for this melt.

6. The process as claimed in claim 5, wherein the process further comprises: producing a melt of a casting material; allowing the melt to cool to form a solid casting material; and providing the solid casting material for introducing the solid casting material into the first furnace vessel.

Description

[0040] In a preferred embodiment, the melting apparatus of the invention has a plurality of first furnace vessels. These can in each case be configured as described here. The advantage of a melting apparatus having a plurality of first furnace vessels is, in particular, that the latter can be charged with solid casting materials each having a different composition, so that the melts formed therefrom can be combined in the second furnace vessel to form a castable melt which represents a combination of the compositions of the melts from the first furnace vessels.

[0041] In one embodiment, the melting apparatus of the invention can have a plurality of second furnace vessels. These can each be configured as described here. The advantage of a melting apparatus having a plurality of second furnace vessels is, for example, that the latter can be charged with liquid casting materials each having a different composition from the first furnace vessels, and these liquid casting materials can, for example, be fed to different casting devices.

[0042] The second furnace vessel is preferably configured for conducting the melt which has been heated to casting temperature in the second furnace vessel into a downstream process stage, for example for conducting into at least one of the following process stages: a device for treating the melt or a casting device. For the present purposes, a treatment device is a device by means of which the melt can be treated according to the prior art For the present purposes, a casting device is a casting device having one or more casting molds.

[0043] The melting apparatus is preferably configured in such a way that the melt which has been heated to casting temperature in the second furnace vessel can be conducted without an intermediate process engineering step, i.e., in particular, without further heating of the melt, to a casting device. In a preferred embodiment, the melt which has been heated to casting temperature in the second furnace vessel can be conducted under the action of gravity into the casting device, for example via channels or tubes. As a result, possibly hazardous transport of the melt to the casting molds is not necessary.

[0044] To discharge the melt from the second furnace vessel, the second furnace vessel preferably has an outlet.

[0045] This outlet is preferably closeable, for example by means of a plug or a slide valve which can be configured like a slide valve or a plug for a ladle or a tundish in steel production. The melt can by this means be discharged from the outlet of the second furnace vessel without the melting process in the second furnace vessel having to be interrupted.

[0046] This has the particular advantage that tilting is not necessary in order to discharge the melt from the second furnace vessel, so that the continuous melting operation in the second casting facility does not have to be interrupted.

[0047] The process of the invention for producing a melt for casting using a melting apparatus according to the invention has the following features: [0048] introducing solid casting material into the first furnace vessel; [0049] melting the casting material in the first furnace vessel; [0050] conducting the melt formed in the first furnace vessel into the second furnace vessel; [0051] increasing the temperature of the melt accommodated in the second furnace vessel to the casting temperature for this melt.

[0052] The casting material used for the process of the invention and also the melt formed therefrom can be treated as indicated here by the melting apparatus of the invention.

[0053] For this purpose, the solid casting material can preferably be present in the form of cast iron or cast steel which is firstly heated to, for example, from 1000 C. to 1300 C. or to from 1400 C. to 1600 C. in the first furnace vessel, then is heated to from 1400 C. to 1600 C. or from 1600 C. to 1700 C. in the second furnace vessel and finally can be conveyed from the second furnace vessel to a downstream treatment or casting unit.

[0054] The process of the invention can be part of a more extensive process for producing the castable melt. A central inventive concept of this more extensive process according to the invention is that the melt is, in contrast to the processes known from the prior art, cooled between the initial melting of the casting material from the raw materials and the provision of a castable melt therefrom, so that a solid casting material is formed from the initially formed melt.

[0055] According to the prior art, a cast iron or cast steel melt having a desired composition is, as indicated above, firstly produced from the raw materials, in particular pig iron and scrap, and is either cast directly or subsequently fed in the liquid state to a downstream casting furnace from where it is fed to the casting units. According to the prior art, the melt formed from the raw materials therefore always remains in a molten state between melting and casting.

[0056] In the process of the invention, however, a melt of a casting material having a desired composition is first formed from the raw materials and is subsequently allowed to cool. This cooled casting material is subsequently melted in the first furnace vessel of the melting apparatus of the invention,

[0057] The more extensive process according to the invention accordingly has the following, further process steps preceding the above-described process: [0058] producing a melt of a casting material; [0059] allowing the melt to cool to form a solid casting material; [0060] providing the solid casting material for introducing the solid casting material into the first furnace vessel.

[0061] This process has the particular advantage that the melting of the casting material in the melting apparatus of the invention can be decoupled from the melting and production of the casting material having a desired composition.

[0062] In this respect, the solid casting materials with which the melting apparatus of the invention is supplied can, for example, be preproduced in any desired amount so that they can be fed when required to the melting apparatus of the invention without delay.

[0063] Furthermore, the invention allows the production of a solid casting material having a desired composition to be carried out separately in time and space from the melting of this casting material in the melting apparatus of the invention. The production of the solid casting material with which the melting apparatus of the invention is charged can thus be carried out, for example, in a different production facility than the melting of this casting material in the melting apparatus of the invention.

[0064] The melting apparatus of the invention can also be constructed with relatively small dimensions.

[0065] Further features of the invention can be derived from the claims, the fl r and the associated description of the figures.

[0066] All features of the invention can, individually combination, be combined with one another in any way.

[0067] A working example of the invention will be explained in more detail with the aid of the following description of the figure.

[0068] FIG. 1 shows a melting apparatus according to the invention in a sectional side view.

[0069] The melting apparatus denoted overall by the reference numeral 1 in FIG. 1 is depicted in a highly schematic embodiment in a sectional side view.

[0070] The melting apparatus 1 comprises a first furnace vessel 3 and a second furnace vessel 5,

[0071] The first furnace vessel 3 is configured as an induction furnace. The first furnace vessel 3 comprises a sheet metal shell 7 which is lined on the inside at the bottom and in the sections of the side walls adjacent to the bottom with a refractory material 9. The upper region of the side walls of the first furnace vessel 3 is not lined with refractory material 9. The refractory material 9 thus encloses the furnace space 13 on the first furnace vessel 3 only in the bottom region. On the outside, the sheet metal shell 7 is encompassed by an induction coil 11 so that casting material present in the furnace space 13 is inductively heatable. At the top, the first furnace vessel 3 has an inlet 12 through which solid casting material can be introduced into the furnace space 13. The inlet 13 can be closed by a flap 15. At the bottom, the first furnace vessel 3 has an outlet 17 for discharging melt which is composed of the casting material and has been formed in the furnace space 13 of the first furnace vessel 3. The outlet 17 can be closed by a plug 19. The furnace space 13 of the first furnace vessel 3 is configured so that a melt composed of casting material can be accommodated therein up to a bath height 21.

[0072] The throughput of the first furnace vessel 3 is about 10 t of cast iron per hour. To be able to melt this amount of solid cast iron per hour, the furnace space 13 or the cast iron present in the furnace space 13 can be supplied with about 4000 kW of power by the induction coil 11.

[0073] The second furnace vessel 5 is arranged beneath the first furnace vessel 3. In terms of its basic structure, the second furnace vessel 5 corresponds essentially to the first furnace vessel 3. In this respect, the second furnace vessel 5 has a sheet metal shell 23 which is lined on the inside with its refractory material 25. The refractory material 25 encloses the furnace space 27 of the second furnace vessel 5. To heat the second furnace vessel 5 or a melt present in the furnace space 27 of the second furnace vessel 5, the sheet metal shell 23 of the second furnace vessel 5 is enclosed by an induction coil 29 by means of which the furnace space 27 is inductively heatable. At the top, the second furnace vessel 5 has an inlet 31 through which melt formed in the first furnace vessel 3 can be conducted into the furnace space 27 of the second furnace vessel 5. Here, the inlet 31 of the second furnace vessel 5 is arranged vertically underneath the outlet 17 of the first furnace vessel 3, so that melt flowing out from the first furnace vessel 3 flows under the action of gravity in free fall through the inlet 31 of the second furnace vessel 5 into the furnace space 27 thereof. At the bottom, the second furnace vessel 5 has an outlet 33 which can be closed by means of a plug 35. Melt flowing out of the furnace space 27 on the second furnace vessel 5 through the outlet 33 can be fed to a distributor channel 37 which conducts the melt directly to a casting unit (not shown) located downstream in the process.

[0074] The capacity of the second furnace vessel 5 is about 1 t of molten cast iron which comes up to the bath level 36 when the second furnace vessel 5 is completely filled. The furnace space 27 of the second furnace vessel 5 can be supplied with about 1000 kW of power by the induction coil 29.

[0075] The process of the invention can be carried out as follows using the melting apparatus 1 shown in the working example:

[0076] A solid casting material in the form of solid cast iron is firstly introduced through the inlet 12 into the furnace space 13 of the first furnace vessel 3. In the furnace space 13, the initially solid cast iron is supplied with energy by the induction coil 11 so that the cast iron melts and its melt has a temperature of about 1120 C. The melt formed in this way is discharged through the outlet 17 of the first furnace vessel 3 by opening the outlet 17 by means of the plug 19, so that the melt flows under the action of gravity through the inlet 31 of the second furnace vessel 5 into the furnace space 27 thereof. In the furnace space 27 of the second furnace vessel 5, the melt is supplied with energy by the induction coil 29 so that the melt heats up to a temperature of about 1500 C. The temperature of 1500 C. corresponds to the casting temperature of the melt, so that after this temperature has been reached, the melt flows out of the outlet 33 of the second furnace vessel 5 as a result of opening the outlet 33 by means of the plug 35 and into the distributor channel 37 from where the melt is conducted to the casting molds of the casting unit.

[0077] In this process, a solid casting material having a known composition is used. This casting material has been obtained by the more extensive process of the invention, with a melt of the casting material firstly having been produced by raw materials being melted to form a melt of the casting material having a desired composition. The corresponding melt was subsequently allowed to cool, The cold casting material then formed was subsequently made available for introduction of this casting material into the first furnace vessel.