Melting and casting process and combined melting and casting furnace plant

Abstract

A process for melting metal parts and casting the melt in at least one mould and a corresponding combined melting and casting furnace plant are described. In the process, metal parts to be melted are brought into a crucible furnace, and a molten metal is produced therein and made ready for casting. A riser tube integrated in a lid of the crucible furnace is heated in a position remote from the crucible furnace, and the lid with heated riser tube is brought into a position closing the crucible furnace, in which the riser tube projects into the molten metal. A mould is arranged on the lid in a casting position above the riser tube, and the molten metal is introduced into the mould from below by pressurising the melt in the crucible furnace. The combined melting and casting furnace plant is designed to carry out such a process.

Claims

1. Process for melting metal parts and casting a molten metal from melting the metal parts into at least one mould for receiving the molten metal, comprising the following steps: a. placing the metal parts in a crucible furnace with a device for bringing the metal parts to be melted into the crucible furnace; b. producing the molten metal and making the molten metal ready for casting in the crucible furnace; c. heating a riser tube, with a heating device, arranged on a pressure-tight crucible furnace lid of the crucible furnace, which forms a unit with the crucible furnace lid, at a position remote from the crucible furnace; d. moving, with a lifting and traversing device, the lid with the heated riser tube to a position closing the crucible furnace, in which position the riser tube projects into the molten metal; e. moving the at least one mould to a casting position on the lid and above the riser tube with a device for bringing the at least one mould into the casting position on the crucible furnace; and f. pouring, with a device for pouring the produced molten metal, the molten metal through the riser tube from below into the at least one mould by pressurising the molten metal in the crucible furnace and feeding the molten metal into the at least one mould.

2. Process according to claim 1, characterised in that, during the pouring of the molten metal through the riser tube, negative pressure is applied in the at least one mould with a device for applying negative pressure to the at least one mould.

3. Process according to claim 1, characterised by a step of flooding a space, with a device for flooding the space, between a molten metal bath surface and the furnace lid with inert gas, wherein the pouring of the molten metal through the riser tube from below into the at least one mould occurs by pressurising the molten metal in the crucible furnace by means of the inert gas.

4. Process according to claim 1, characterised in that the crucible furnace is covered by a part, designed as a hood, of a device for bringing the metal parts into the crucible furnace during production of the molten metal and preparation of the molten metal for casting.

5. Process according to claim 1, characterised in that fumes produced during production of the molten metal are extracted above the crucible furnace with an extraction device for removing the fumes.

6. Process according to claim 1, characterised in that the lid with riser tube is moved back and forth between a waiting position, in which the riser tube is heated, and a closing position of the crucible furnace.

7. Process according to claim 1, characterised in that two crucible furnaces are used in a double furnace plant, wherein one is operated in melting mode and one in casting mode alternately.

8. Process according to claim 7, characterised in that both crucible furnaces are operated with a single lid with riser tube.

9. Process according to claim 1, characterised in that the molten metal is prepared in the melting crucible furnace ready for casting with regard to temperature, chemical analysis and deslagging.

10. Process according to claim 1, characterised in that useful contents of the casting crucible furnace are poured successively into a plurality of moulds until the useful contents are emptied.

11. Process according to claim 1, characterised in that a temperature of the molten metal is kept constant with devices for keeping the temperature constant.

12. Process according to claim 1, characterised in that the riser tube has a temperature resistance and is suitable for casting FE-based alloys and consists of inorganic-chemically or hydraulically bonded refractory concrete of one of the following compositions, wherein the percentages in the following are percentages by weight: composition having at least 75% Al2O3, up to 23% SiO2, up to 1.0% Fe2O3, up to 0.25% MgO and optionally further residual components CaO and SiC; or composition having at least 70% Al2O3, up to 25% SiO2, up to 1.1% Fe2O3, up to 1.0% CaO and optionally further residual components MgO and SiC; or composition having at least 72.0% SiC, up to 18% Al2O3, up to 10% SiO2, up to 0.1% Fe2O3, up to 0.15% MgO, and optionally further residual components CaO; wherein in these compositions, the further residual components may optionally be present in an amount of up to 3%.

13. Combined melting and casting furnace plant having a crucible furnace for producing and making a molten metal ready for casting, a device for bringing metal parts to be melted into the crucible furnace, at least one mould for receiving the molten metal, a device for bringing the at least one mould into a casting position on the crucible furnace, a pressure-tight crucible furnace lid and a riser tube arranged thereon, which forms a unit with the crucible furnace lid, a heating device for the riser tube, a lifting and traversing device for the crucible furnace lid with the riser tube, and a device for pouring the produced molten metal by pressurising the crucible furnace and feeding the molten metal into the mould from below by means of the riser tube of the crucible furnace.

14. Plant according to claim 13, characterised by a device for applying negative pressure to the at least one mould during pouring of the molten metal through the riser tube.

15. Plant according to claim 13, characterised in that the plant is provided with a moveable charging device for charging material for producing the molten metal.

16. Plant according to claim 13, characterised in that the plant has an extraction device for removing fumes produced during melting above the crucible furnace.

17. Plant according to claim 13, characterised in that the device for bringing the metal parts into the crucible furnace is provided with a hood for covering the crucible furnace.

18. Plant according to claim 13, characterised in that the plant is designed as a double furnace plant.

19. Plant according to claim 18, characterised in that the double furnace plant is set up in such a way that one crucible furnace is in melting mode and the other crucible furnace is in casting mode.

20. Plant according to claim 13, characterised in that the plant has devices for keeping the temperature in the casting furnace constant.

21. Plant according to claim 13, characterised by a device for flooding a space between a molten metal bath surface and the furnace lid with inert gas, wherein pouring of the molten metal through the riser tube from below into the at least one mould occurs by pressurising the molten metal in the crucible furnace by means of the inert gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in detail below using an exemplary embodiment in conjunction with the drawing. Here are shown:

(2) FIG. 1 a spatial representation of a double furnace plant;

(3) FIG. 2 a side view of part of the plant of FIG. 1 with a charging device and crucible furnace;

(4) FIG. 3 a vertical section through a crucible furnace of the plant in the casting process; and

(5) FIG. 4 a part of the plant in spatial representation.

DETAILED DESCRIPTION

(6) The combined melting and casting furnace plant depicted in the figures is a double furnace plant which has two crucible furnaces 1 and 2 arranged adjacent to each other. Here, the crucible furnace 1 depicted in FIG. 1 on the left is a casting process in which moulds 10 are charged with the molten metal melted in the crucible furnace 1, while the crucible furnace 2 depicted in FIG. 1 on the right is in a melting process in which metal parts are melted in the crucible furnace 2. The plant preferably has a single crucible furnace lid 8 which is used alternately by one furnace 1 and the other furnace 2. A centrally downwardly extending riser tube 9 is arranged on the crucible furnace lid 8, which is required for the casting process described below. In FIG. 1, two crucible furnace lids 8 are depicted for better illustration, one of which is located on the crucible furnace 1, while the other lid 8 is depicted above a heating device 7 for the riser tube 9.

(7) Each crucible furnace 1, 2 is provided with a suitable charging device 3, 4, which can be conventionally designed and provided with a suitable vibratory conveyor for feeding metal parts to be melted into the crucible furnace. The respective charging device 3, 4 comprises a hood 5, 6 arranged at its front end, which covers the upper side of crucible furnace during the conveying of the metal parts to be melted into the crucible furnace. In this way, during the melting of the metal parts (melting process), escape of fumes into the surrounding atmosphere is prevented. For this purpose, the charging device 3 is further provided with a suitable exhaust device.

(8) The moulds to be filled with the molten metal are denoted by 10. The moulds 10 are successively guided onto the lid 8 of a crucible furnace, as shown for the left furnace in FIG. 1. After the mould has been filled, it is guided away to the left of the lid in the figure.

(9) The combined melting and casting furnace plant depicted in FIG. 1 is operated in the following manner:

(10) The charging device 4 is filled with metal parts (scrap metal) to be melted in a position spaced apart from the crucible furnace, and the metal parts are fed into the crucible furnace which is open at the top. During this process, the hood 6 covers the top of the crucible furnace. This state is depicted in FIG. 1 with the crucible furnace 2 on the right in the depiction.

(11) The metal parts are now melted in a suitable manner in the crucible furnace 2, such that it results in a metal melt located in the furnace. The exhaust gases produced during the melting process are prevented from escaping into the atmosphere by the hood 6 and are drawn off via a suitable exhaust device. After completion of the melting process, the molten metal is made ready for casting by suitable known means.

(12) While the crucible furnace 2 is in the melting process described above, the crucible furnace 1 is in the casting process. For this purpose, after completion of the melting process, the charging device 3 is removed from the furnace and a crucible furnace lid 8 with a centrally downward projecting riser tube 9 is placed on the crucible furnace 1. This crucible furnace lid 8 with a riser tube 9 has been located separately from the furnace in a suitable heating device 7 to reduce the temperature difference between the riser tube 9 and the molten metal. After the riser tube 9 has been suitably heated, the lid 8 with the riser tube 9 is removed from the heating device 7 and placed on the crucible furnace 1 such that it is closed in this way in a pressure-tight manner A suitable mould 10 for receiving the molten metal is then arranged on the lid in a suitable casting position. This state is depicted in FIG. 1 for the crucible furnace 1 on the left.

(13) The molten metal is then introduced through the riser tube 9 from below into the mould 10 by pressurising the molten metal in the crucible furnace via a gas introduced into the crucible furnace. This low-pressure casting process is known as such. The filled mould 10 is then withdrawn from the crucible furnace 1 and transferred to its position in the heating device 7. The charging device 3 with the hood 5 can then be moved back to the crucible furnace to fill it again with metal parts.

(14) It is understood that suitable moulds 10 are filled with the molten metal until the crucible furnace has been emptied.

(15) In the depicted double furnace plant, therefore, one crucible furnace is always in the melting process, while the other is in the casting process. A single crucible furnace lid 8 with integrated riser tube 9 is used by both crucible furnaces 1, 2 and is fed alternately to each crucible furnace by a heating device 7 arranged between the furnaces for heating the riser tube 9.

(16) FIG. 2 shows the crucible furnace 1 in the melting position, in which the charging device 3 introduces the metal parts to be melted into the crucible furnace 1 from above, wherein the provided hood 5 covers the crucible furnace from above. In this position, the melting process then takes place in the crucible furnace 1, wherein the resulting fumes are collected by the hood and discharged via a suitable exhaust device. The charging device 3 is designed in the shape of a trough and is provided with a suitable vibratory conveyor, which can be designed in the conventional manner.

(17) FIG. 3 shows the crucible furnace 1 in vertical section. The furnace is in the casting position here, in which a crucible furnace lid 8 with integrated riser tube 9 is arranged on the crucible furnace and closes it in a pressure-tight manner. On the lid 8, there is a corresponding mould 10 into which the molten metal to be cast is introduced by pressurising the inside of the furnace with a pressurised gas.

(18) FIG. 4 shows the crucible furnace 1 in the casting position, in which the crucible furnace lid 8 with integrated riser tube 9 is located on the crucible furnace and closes it in a pressure-tight manner A mould 10 to be filled with the molten metal is arranged on the lid.

(19) Furthermore, it can be seen in FIG. 4 how the crucible furnace lid 8 with integrated riser tube 9 is located above a heating device 7 for the riser tube. The lid 8 is moved from this position to the position depicted on the left on the crucible furnace 1. After completion of the melting process, the lid 8 with integrated riser tube 9 is moved back into the heating device 7 so that the riser tube 9 can be heated for the next casting process. This casting process then takes place with the second crucible furnace 2 not depicted in FIG. 4.