EP0212072B1 - Induction furnace with a body and a top - Google Patents

Description

The invention relates to an induction furnace with a furnace base containing a crucible, an induction coil and a gas-tight jacket, furthermore with a cover which can be placed on the furnace base and which has at least one gas connection, a charging valve and a pouring device, the furnace base and cover being detachable but gas-tight via a flange connection connected to each other and in the connected state by means of an articulated bearing and a drive tiltable about a tilt axis in a furnace frame.

In such gas-tight induction furnaces, which can be operated both under protective gas and under vacuum, such materials are regularly melted and kept ready for casting which are subject to oxidation and / or gas absorption when they are melted in the atmosphere. Such furnaces are preferably used for melting metals which are highly reactive at the melting temperature.

Such induction furnaces require a whole series of additional devices, which are usually attached to the lid or can be connected to the lid, such as charging devices, purification devices, measuring and observation devices, pouring devices etc. Also the gas connections required for the introduction of a protective gas or the evacuation by vacuum pumps are usually attached to the lid.

In the previously known induction furnaces of the type described at the outset, the articulated bearing for the tilting movement is located on the lower part of the furnace, and the tilt drive also acts on the lower part of the furnace. For this purpose, the lower part of the furnace has a support frame which is mounted in a furnace frame by means of pivot pins. However, this principle of construction leads to a number of problems:

The crucible used in induction furnaces, which is made of a ceramic material in a conventional manner and is often also referred to as "lining", is subject to more or less severe wear, namely due to thermal and mechanical stress. The mechanical stresses also include the regular movement of the melt by inductive bath stirring, which is used both to form alloys and to intensify gas exchange. In many cases, after melting several batches, it is necessary to check the lower part of the furnace including the induction coil and, if necessary, to replace the crucible or the lining.

In the previously known induction furnaces described above, the procedure was such that the freely movable lid was removed and the necessary inspection and repair work was carried out on the lower part of the furnace. Here, however, the existing cover, which is a relatively expensive component due to its numerous attachments and internals, could no longer be used unless the user had a second complete induction furnace of the known design. If the lower part of the furnace remained in the furnace frame for carrying out the inspection and repair work, this, too, was condemned to a standstill with the associated vacuum pumps, so that the cost-effectiveness the entire induction melting plant was severely restricted. It should be noted here that the furnace lid with all fittings and attachments, as well as the furnace frame with the supply facilities for the induction melting system, must be inspected or serviced at much longer intervals.

The invention is therefore based on the object of specifying an induction furnace of the type described at the outset, in which the inspection and repair work on the lower part of the furnace can be carried out much more easily and in which the furnace cover with its complex fittings and attachments also continues during the inspection and repair work is usable.

The object is achieved according to the invention in that the articulated bearing is attached to the cover, that the tilt drive engages the cover and that the lower furnace part can be removed from the cover compared to the cover remaining in the furnace frame after loosening the flange connection.

With the solution according to the invention, the lid basically has the function of a reference platform, which remains permanently in the furnace frame via the specified articulated bearing, and all additional devices such as gas connections, charging valve, pouring device, measuring and observation devices can also remain on the lid. The gas connections include in vacuum induction furnaces also the suction lines, which have a considerable cross section and are connected to the vacuum pumps by means of rotary joints.

For the further use of the lid, furnace frame, supply facilities (power supply, cooling water and gas treatment plants) and vacuum pumps, it is only necessary to have at least one further furnace base available, which is exchanged for the furnace base to be inspected or repaired. To remove the lower part of the furnace from the system, it is then only necessary to disconnect the power and cooling water connections to the lower part of the furnace or the induction coil and to connect them to the connections of the new lower part of the furnace. The entire smelting plant is then ready for operation again at short notice, while the lower part of the furnace which is in need of repair can be made ready for use elsewhere. As a result, the capital investment required for a certain melting capacity is greatly reduced, and the economy of the entire melting plant is increased accordingly, without resulting in a significant increase in cost compared to the known design principle.

It is advantageous according to a further development of the invention if the cover is provided in the region of the tilt axis with a pouring tube which is essentially tangential to the cover wall, is connected gas-tight to the cover and is open to the interior of the cover and if the crucible has a pouring spout which projects into the pouring tube and ends in the tilting axis.

The pouring tube, in which there is usually a ceramic pouring trough, leads - preferably via a gas-tight rotating coupling - to a distributor tube, via which the melt can be fed to different pouring stations. Since the pouring tube is located in the area of the articulated bearing connected to the cover, the connection between the pouring tube and the distributor tube also remains in place when the lower part of the furnace is removed, so that no dismantling work is required at this point either.

According to a further embodiment of the invention, it is again particularly advantageous if the lid is provided with a gas-tight extension on the side diametrically opposite the pouring tube, in which there is a slag collecting container, and if the crucible on the side diametrically opposite the pouring spout a pouring lip is provided, via which the slag can be transferred into the slag collecting container at an inclination of the crucible opposite to the pouring position.

This device, which can be simply referred to as a "detoxification device", remains permanently connected to the furnace lid and also to the furnace frame via the rotary bearing according to the invention and is still ready for use in connection with a new furnace base.

It is also advantageous if the cover is provided with a gas connection for a protective gas, if this gas connection also opens into the flange of the cover and communicates at the opening point with a gas line located in the flange of the lower part of the furnace, which in a between the jacket and the crucible located cavity opens in which the induction coil is located.

In this way it is possible, for example, to remove moisture escaping from the crucible or the brickwork from the lower part of the furnace, so that the otherwise occurring entry of water vapor into the melt gas atmosphere is prevented (gas purging).

The removal of the released moisture is then further promoted if there is a further gas line and a suction line on the side of the flange connection opposite the mouth, which likewise communicate with one another via the flange connection. In this case, an additional blower or a pump is preferably arranged in the suction line, which generates an additional negative pressure compared to the melt gas atmosphere. This has the following effect:

In the case of protective gas operation, the incoming main gas stream is divided into a gas stream for purging the melting chamber and a secondary gas stream for purging the cavity in which the induction coil is located. The one in the suction line, i.e. The fan arranged at the outlet of the secondary gas flow now generates a pressure difference between the melting chamber and the cavity mentioned. Due to the low absolute pressure in the cavity, the water desorbed from the crucible material is removed in the bypass gas stream, and the entry of water into the melt gas atmosphere is effectively prevented.

Due to the specified design, the supply line and the discharge line for the bypass flow of the protective gas are located in the cover, so that the connection to a gas processing system for drying and cleaning the protective gas can remain. The necessary connection to the lower part of the furnace is made automatically by attaching it to the lid, without the need for additional connections.

Finally, in a further embodiment of the invention, it is particularly advantageous if the tilt drive consists of at least one first pressure medium cylinder, which is connected at its upper end to the frame structure of the cover via a first joint and at its lower end End is mounted on a rocker arm via a second joint, the opposite end of which is mounted on the furnace frame via a third joint, the first, second and third joint lying on the corners of a triangle and all joint axes running parallel to the tilt axis. If the rocker can also be moved from at least one second pressure medium cylinder from a first swivel range, which is decisive for casting, to a second swivel range, which is decisive for detoxification, the interaction of the first pressure medium cylinder with the second pressure medium cylinder via the rocker allows the induction furnace to tilt from the horizontal The position of the flange connection in one direction of rotation (e.g. for detoxification) and in the opposite direction of rotation (e.g. for pouring) enable without the need for bulky drive elements that would require a pit in the area of the furnace frame.

Further refinements of the subject matter of the invention result from the remaining subclaims.

An embodiment of the subject matter of the invention is explained in more detail below with reference to FIGS. 1 to 8.

Figur 1

eine Seitenansicht des Induktionsofens in Chargier- bzw. Schmelzstellung, d.h. bei horizontaler Lage der Flanschverbindung,

Figur 2

einen Vertikalschnitt durch das Ofenunterteil und den Deckel in einer Position gemäß Figur 1 im Zusammenwirken mit einem Transportwagen für das Ofenunterteil,

Figur 3

den oberen Teil von Figur 2 mit einem geringfügig hochgeschwenkten Deckel, um das seitliche Einfahren (oder Ausfahren) des Ofenunterteils zu ermöglichen,

Figur 4

einen Vertikalschnitt durch ein Ofenunterteil mit aufgesetztem Deckel in einer gegenüber Figur 2 um 90 Grad verdrehten Schnittebene,

Figur 5

den Induktionsofen nach Figur 1 (jedoch ohne Chargierbehälter) in der Entschlackungsposition,

Figur 6

den Induktionsofen nach Figur 1 (jedoch ohne Chargierbehälter) in seiner Endstellung nach Beendigung des Abgusses,

Figur 7

eine Draufsicht von oben auf den Gegenstand von Figur 1 (jedoch ohne Chargierbehälter), und

Figur 8

eine Draufsicht analog Figur 7 nach Weglassung einiger die Sicht versperrender Details mit teilweise gestrichelt dargestellten inneren Einbauten.

Show it:

Figure 1

a side view of the induction furnace in charging or melting position, ie with the flange connection in a horizontal position,

Figure 2

2 shows a vertical section through the lower furnace part and the cover in a position according to FIG. 1 in cooperation with a transport carriage for the lower furnace part,

Figure 3

the upper part of Figure 2 with a slightly pivoted lid to allow the lateral retraction (or extension) of the lower furnace part,

Figure 4

3 shows a vertical section through a lower part of the furnace with a lid attached in a section plane rotated by 90 degrees compared to FIG. 2,

Figure 5

the induction furnace according to Figure 1 (but without charging container) in the detox position,

Figure 6

the induction furnace according to Figure 1 (but without charging container) in its end position after completion of the casting,

Figure 7

a plan view from above of the object of Figure 1 (but without charging container), and

Figure 8

a plan view analogous to Figure 7 after omitting some details obstructing the view with internal fittings shown partially in dashed lines.

In Figure 1, a furnace frame 1 is shown, which has a base frame 2 and two vertical supports 3, at the upper ends of which a joint bearing 4 is arranged. This articulated bearing conventionally consists of a bearing housing and a bearing journal and is arranged twice in succession in the direction of view. The other part of the articulated bearing 4 is attached to a cover 6 of an induction furnace 7, which also includes a lower furnace part 8, via a bracket 5. Cover 6 and lower furnace part 8 are connected to one another in a gas-tight manner via a flange connection 9.

On the cover 6, a pouring device 10, a gas connection 11 and a charging valve 12 are also arranged, which in addition to the articulated bearing 4 belong to the essential components of the cover. The joint bearing 4 defines a tilt axis A, which is perpendicular to the plane of the drawing.

An essential part of the pouring device 10 is a pouring tube 13, which extends tangentially to the cover wall in the region of the tilt axis A, is connected gas-tight to the cover 6 and is open to the interior of the cover. The pouring tube 13 is closed on its end facing the viewer and can be closed on the opposite side by a slide valve 14 (see also FIG. 8).

On the side diametrically opposite the pouring tube 13, the cover 6 is provided with a gas-tight extension 15, in which there is a slag collecting container 16 (FIG. 2). The extension 15 is connected via a discharge valve 17 to a removal chamber 18 into which the slag collecting container 16 can be inserted (FIG. 8). In the area of the extension 15 and the removal chamber 18, a work platform 19 is fastened to the cover 6 via a joint 20, the work platform 19 being supported on a boom 22 by means of a drive 21, which is also fastened to the cover 6. The function of the drive 21 will be discussed in more detail in connection with FIG. 5.

The charging valve 12 is arranged on the top of the cover 6 and has a horizontal connecting flange 23 (FIG. 7) for connection to a Charging container 24 movable above the furnace. This charging container, which can likewise be evacuated via a suction line 25, rests on a carriage 26, which in turn can be moved parallel to the plane of the drawing on rails 27 which extend across the induction furnace 7 and to one (not shown) lead station in which the charging container 9 can be loaded. The charging container carries in its interior (not shown) a charging basket with a closable bottom opening which can be lowered into the induction furnace 7 through the charging valve 12 through the charging valve 12.

The tilting movement of the induction furnace 7 is of course only possible after the charging container 24 has been moved sideways. To bring about this tilting movement about the tilting axis A, a tilting drive 28 is provided, to which a first pressure medium cylinder 29 belongs, the upper end of which engages on the cover 6, which for this purpose is surrounded by a frame structure 31 in the region of its flange 30 (FIG. 3) on which the tilt drive 28 engages by means of a first joint 32 (FIG. 6). The lower end of the pressure medium cylinder 29 is fastened to a rocker 34 via a second joint 33, the opposite end of which is fastened to the furnace frame 1 via a third joint 35. All joint axes run parallel to the tilt axis A and lie towards the corners of a triangle, so that by changing the Length of one side of this triangle, that is to say: the induction furnace 7 can be tilted by extending the piston rod 36 out of the pressure medium cylinder 29 (FIG. 6).

The rocker 34 is held in its position shown by the piston rod 37 of a second pressure medium cylinder 38 which is mounted on a fourth joint 39. The joints 33, 35 and 39 lie on the corners of a triangle, so that by changing the length of one side of this triangle, that is: by moving the piston rod 37 into the pressure medium cylinder 38, a pivoting movement of the induction furnace 7 can be brought about, namely in the opposite direction Direction according to FIG. 5. The pressure medium cylinder 38 advantageously engages the rocker in the area of the joint 33; however, it is possible to provide an additional joint for this.

It can also be seen from FIG. 1 that the charging container 24 is supported on the carriage 26 by means of four lifting cylinders 40, so that the lower flange 41 of the charging container 24 can be lifted off the connecting flange 23 before a transverse movement of the charging container takes place. A geared motor 42 is used to drive the carriage 26.

The internal structure of the induction furnace 7 is additionally shown in FIGS. The lower furnace part 8 contains a gas-tight jacket 43, in which a crucible 44 made of ceramic material is arranged at a radial distance. Between the jacket 43 and the crucible 44 there is a cavity 45 in which an induction coil 46 is accommodated. The jacket 43 is surrounded slightly below its upper edge by a frame structure 47 which is closed on the top by a flange 48 which can be assembled with the flange 30 of the cover to form the gas-tight flange connection 9. It can be seen from FIG. 2 that the crucible 44 and the induction coil 46 protrude to a certain extent into the cover 6. On one side, the crucible 44 has a pouring spout 49 which projects into the pouring tube 13 and ends in the tilting axis A. Below the end of the pouring spout 49 there is also a ceramic channel 50, which will be discussed in more detail in connection with FIG. 8. It is evident from FIGS. 2 and 3 that the end of the pouring spout 49 lies in the tilting axis A in every position of the crucible 44.

On the diametrically opposite side of the pouring spout 49, the crucible 44 is provided with a pouring lip 51, via which the slag can be transferred into the slag collecting container 16 at an inclination of the crucible opposite to the pouring position according to FIG is. In order to scrape off the slag, there is also a sliding passage 52 in the cover 6, through which the actuating rod 53 of a scratch 54 is passed.

In FIG. 2 there is a transport carriage 55 with lifting devices 56 under the lower furnace part 8, by means of which the lower furnace part can be lowered by a dimension "s" before the cover 6 is raised into a position according to FIG. 3 by means of the tilting drive 28. In this position of the cover 6, the lower furnace part 8 can be moved laterally out and in again in the direction of the double arrow 57 by means of the transport carriage 55. Although the crucible 44 projects upward beyond the flange 48 by a not inconsiderable amount, there is no mutual obstruction of the parts which are movable relative to one another or even damage to the pouring spout 49.

From Figure 4 it can be seen that the cover 6 is provided with a (further) gas connection 58 for a protective gas. This gas connection opens into the flange 30 of the cover 6 and communicates at the outlet 59 with a gas line 60 located in the flange 48 of the lower furnace part 8, which opens into the cavity 45 located between the jacket 43 and the crucible 44. On the side of the flange connection 9 opposite the outlet 59 there is a further gas line 61 in the lower part of the furnace and a suction line 62 in the cover, the two lines also communicate with each other via the flange connection 9. In the further course of the suction line 62 there is a blower 63, by means of which a negative pressure is generated in the cavity 45 with respect to the melting chamber 64, through which the effect of the removal of water vapor described above occurs. The gases are discharged from the melting chamber 64 through a suction line 65 which is connected to the gas connection 11 (FIG. 1). The pressure side of the blower 63 also opens into the suction line 65 via a line 66.

Figure 5 now shows the induction furnace 7 in the detoxification position. The tilting movement about the tilt axis A required for this was brought about by retraction of the piston rod 37 into the pressure medium cylinder 38, as a result of which the rocker arm 34 and the lower joint 33 for the pressure medium cylinder 29 have assumed the position of FIG. 5 which is self-explanatory. Here, the upper joint 32 has followed the displacement of the lower joint 33, as a result of which the induction furnace 7 has been brought into the purification position shown. At the same time, the piston rod 67 of the drive 21 was extended and the work platform 19 was held in a precisely horizontal position, so that the detoxification process can be observed and controlled by the operator through a sight glass 68.

Figure 6 shows the end position already described for casting, i.e. the joint 33 is in the position shown in FIG. 1 when the piston rod 37 is extended, and only the piston rod 36 has been continuously extended from the pressure medium cylinder 29 in order to carry out the pouring process. It is understood that the charging valve 12 is closed in all these measures.

In FIG. 7, the same parts as before are provided with the same reference symbols. The stable mounting of the cover 6 via the two brackets 5 in the articulated mounting 4 and the coaxial alignment of a rotary coupling 69, through which the pouring tube 13 is connected to a distributor tube 70 beyond the slide valve 14, and the coaxial arrangement of a rotary coupling are also clearly visible 71 in the suction line 65. Finally, rails 72 for the trolley 55 are shown in FIG.

The retention of the reference numerals also applies to FIG. 8, in which the following is also shown. In the pouring tube 13 or in the distributor tube 70 there is the channel 50, which can be moved in the direction of the double arrow between the two positions shown in broken lines by means of a motor 73. The cross section of the slide valve 14 is released by moving the channel into the distributor pipe 70 so that it can be closed. From the manifold 70, the melt is in a Transfer channel 74 directed, which leads to a pouring device, not shown here. A cable and hose swiveling device 75, which is only shown schematically here and which is likewise arranged coaxially to the tilting axis A, is used for the (movable) supply of electricity and cooling water to the lower furnace part 8. In the furnace cover 6 there is also a temperature measuring lance 76, which is also shown here only schematically.

Claims (14)

1. Induction furnace having a furnace bottom comprising a crucible, an induction winding and a gas-tight casing, having also a lid which fits on the furnace bottom, which has at least one gas connection, a charging valve and a pouring arrangement, in which the furnace bottom and the lid are connected releasably but in gas-tight fashion by a flange joint and tiltably supported about a pivot axis in the connected state in a furnace stand by a pivot bearing and a tipping mechanism, characterised in that the pivot bearing (4) of the induction furnace is secured to the lid (6), the tipping mechanism (28) engages the lid (6) and the furnace bottom (8) is separable from the lid by unfastening the flange connection (9), the lid (6) remaining in the furnace stand (1).
2. Induction furnace according to claim 1, characterised in that the lid (6) is surrounded by a frame structure (31) in the region of its flange (30), on which the tipping mechanism (28) engages.
3. Induction furnace according to claim 1, characterised in that the lid (6) is provided with pouring tube (13) in the region of the tipping axis (A) which runs substantially tangentially to the wall of the lid, which is in gas-tight connection with the lid and which is open to the interior of the lid, and that the crucible (44) has a pouring spout (49) which extends into the pouring tube and terminates at the tipping axis (A).
4. Induction furnace according to claim 3, characterised in that the pouring tube (13) is in gas tight connection with a distributor tube (70) by means of a rotary coupling (69).
5. Induction furnace according to claim 3, characterised in that the lid (6) is provided on the side diametrically opposite the pouring tube (13) with a gas-tight projection (15) in which is located a slag collecting vessel (16), and in that the crucible (44) is provided, on the side diametrially opposite the pouring spout (49), with a pouring lip (51), over which the slag can be run into the slag-collecting vessel (16) by tipping the crucible oppositely to the pouring position.
6. Induction furnace according to claim 5, characterised in that the gas-tight projection (15) is connected by an air lock (17) with a removal chamber into which the slag-collecting vessel can be taken.
7. Induction furnace according to claim 5, characterised in that the lid (6) is pivotally connected in the region of the projection (5) for the slag-collecting vessel (16) with a working platform (19), which can be held in the horizontal position at all times during the tipping movement of the furnace into the slag run-off position by means of a mechanism (21).
8. Induction furnace according to claim 1, characterised in that the induction winding (46) is arranged within the gas-tight casing (43) of the furnace bottom (8).
9. Induction furnace according to claim 8, characterised in that the lid (6) is provided with a gas connection (58) for a shielding gas, in that this gas connection opens into the flange (30) of the lid (6) and communicates at the opening position (59) with a gas conduit (60) located in the flange (48) of the furnace bottom (8), which opens into a space (45) in between the cover (43) and crucible (44) in which the induction winding (46) is located.
10. Induction furnace according to claim 9, characterised in that a further gas conduit (61) and an extraction conduit (62) are located at the side of the flange connection (9) opposite the opening position (59) which are likewise in communication via the flange joint.
11. Induction furnace according to claim 1, characterised in that the cover (6) has an upper charging valve (12) which is provided with a horizontal connecting flange (23) for connection to a charge hopper which can be brought up above the furnace.
12. Induction furnace according to claim 2, characterised in that the tipping mechanism (28) comprises at least a first pressure cylinder (29) which is connected at its upper end to the frame structure (31) of the lid (6) by a first connector (32) and at its lower end is connected by a second connector (33) to a link (34) of which the opposite end is connected to the furnace stand (1) by a third connector (35), of which the first, second and third connectors (32, 33, 35) lie at the apices of a triangle and all have pivot axes parallel to the tipping axis (A), and in that the link (34) is movable by at least a second pressure cylinder (38) from a first pivotal region for melt to pouring to a second pivotal region for slag removal.
13. Induction furnace according to claim 1, characterised in that the lid (6) is raisable from a horizontal position of its flange (30) about the tipping axis into a slightly inclined position relative thereto, in which the furnace bottom (8) can be removed to the side from underneath the lid (6) after unfastening the flange joint (9).
14. Induction furnace according to claim 13, characterised in that a transport carriage (55) with a jacking mechanism (56) is provided for moving the furnace bottom (8).

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