EP1563112B1 - Device for hot-dip coating a metal bar - Google Patents

Abstract

The invention relates to a device for hot-dip coating a metal bar (1), particularly a steel strip, in which the metal bar (1) is vertically directed through a container (3) receiving the molten coating metal (2) and a directing channel (4) that is arranged upstream thereof. Said device comprises at least two inductors (5) which are disposed on both sides of the metal bar (1) in the zone of the directing channel (4) and generate an electromagnetic field for retaining the coating metal (2) within the container (3). In order to better control the coating process, the inventive device is characterized by a sealing means (7, 7') which is arranged above the directing channel (4) in the bottom area (6) of the container (3) and alternatively releases or interrupts the flow of molten coating metal (2) to the metal bar (1) and/or the directing channel (4).

Description

The invention relates to a device for hot dip coating a metal strand, in particular a steel strip, in which the metal strand is passed vertically through a container receiving the molten coating metal and through an upstream guide channel, with at least two on both sides of the metal strand in the region of the guide channel arranged inductors for generating an electromagnetic Field for retaining the coating metal in the container.

Conventional metal immersion coating systems for metal strips have a maintenance-intensive part, namely the coating vessel with the equipment located therein. The surfaces of the metal strips to be coated must be cleaned of oxide residues prior to coating and activated for connection to the coating metal. For this reason, the belt surfaces are treated in a reducing atmosphere prior to coating in heating processes. Since the oxide layers are previously removed chemically or abrasive, the reducing heat process activates the surfaces in such a way that they are metallically pure after the heat process.

With the activation of the strip surface but increases the affinity of these strip surfaces for the surrounding atmospheric oxygen. In order to prevent atmospheric oxygen from getting back to the belt surfaces before the coating process, the belts are introduced from above into the dip-coating bath in a plunger. Since the coating metal is in liquid form and one would like to use the gravitation together with blowers for adjusting the coating thickness, but the subsequent processes prohibit belt contact until complete solidification of the coating metal, the tape in the coating vessel in vertical Direction be redirected. This happens with a roller that runs in liquid metal. Due to the liquid coating metal, this roller is subject to heavy wear and is the cause of downtimes and thus failures in production.

Due to the desired low coating thickness of the coating metal, which can move in the micrometer range, high demands are placed on the quality of the strip surface. This means that the surfaces of the tape-guiding rollers also have to be of high quality. Disturbances on these surfaces generally lead to damage to the strip surface. This is another reason for frequent shutdowns of the plant.

In order to avoid the problems associated with the rollers running in the liquid coating metal, there have been attempts to use a downwardly open coating vessel which has a guide channel for vertical tape feed-through in its lower portion and an electromagnetic shutter for sealing use. These are electromagnetic inducers that work with backward, pumping or constricting electromagnetic alternating or Wanderfeldem that seal the coating vessel down.

Such a solution is known, for example, from EP 0 673 444 B1. An electromagnetic closure for sealing the coating vessel downwards is also employed by the solution according to WO 96/03533 or that according to JP 5086446.

Ensuring the tightness of the downwardly open guide channel of the coating vessel is an important and difficult task, especially when one thinks of the emergency, in which due to power failure, the electromagnetic closure can fail. For this purpose, various possibilities are disclosed in the prior art.

For this purpose, EP 0 630 421 B1 provides for a constriction below the guide channel, from which a pipeline leads to a reservoir for molten coating metal. Further details on the design of this designated as a backstop device are not apparent from this document.

JP 2000273602 A discloses below the guide channel a collecting trough, which is to receive coating metal, which runs down through the guide channel. This is led to a container, from where it is returned to the coating bath via a pump. Again, no specific and specific information is given as discontinued coating metal to be collected.

EP 0 855 450 B1 deals in more detail with the question of how the tightness of the lower region of the guide channel can be ensured. To ensure this, various alternative solutions are disclosed here. According to one embodiment, two slides, which are arranged on both sides of the metal strand, are moved perpendicular thereto to the surface of the metal strand. The sliders act as stoppers and are held in contact with the metal strand as needed to prevent liquid leakage down the guide channel. However, a relatively complex control of the slide is required to ensure its function. Another embodiment provides that a conveyor belt is used, which promotes exiting coating metal from the area below the guide channel into a collecting container. However, this solution is very expensive and involves the risk that the band clogged with coating metal over time and thus can no longer perform its function. A third alternative solution for preventing the escape of molten coating metal provides a gas nozzle system. In this case, a gas flow is directed from below onto the guide channel, the emerging coating metal tear up and thus seal the opening down. This solution is very complex and only partially practicable.

From FR 2 798 396 A, a hot-dip coating installation is known in which it is provided that a barrier is arranged in the bottom area of the coating vessel at the transition into the guide channel. This is to keep the flow in the liquid coating channel from the guide channel; For this purpose, it is provided that it is equipped with aerodynamically designed walls or baffles. However, the barrier disclosed in this document is not suitable for keeping the liquid coating metal from the region of the guide channel if necessary. In the same way, it is not possible for him to influence the coating process.

From EP 0 855 450 A1, a solution is known in which a temporary seal between the melt in the coating container and the guide channel is accomplished with a closure which consists of fusible material whose melting point is at most as high as that of the coating metal. After melting this closure, the fluidic connection between the melt in the coating container and guide channel is produced.

The invention is therefore based on the object to provide a device for hot dip coating of a metal strand, with which it is possible to perform the coating process optimally and also to ensure reliable operation of the system in critical operating conditions in a simple manner, for example, interrupted when the power supply of the inductors is.

The solution of this object by the invention is characterized by a above the guide channel in the bottom region of the container arranged closure means for selectively enabling or interrupting the flow of molten coating metal to the metal strand and / or the guide channel, wherein the closure means is designed as weir, relative to the bottom portion of the Container is movable.

Thus, according to the invention, the flow of the coating metal, in particular, can optionally be released or interrupted, in particular in the case of a malfunction, so that there is no danger of molten metal leaving the coating device via the guide channel.

With this embodiment, it is possible to avoid damage to the coating device or an economic loss in the case mentioned.

According to one embodiment, the weir has two cooperating parts which are each movable perpendicular to the surface of the metal strand. Alternatively or additionally, it can be provided that the weir is movable in the conveying direction of the metal strand.

In the latter case it can be provided that the weir is formed in one piece and has the shape of a box. In this way, both the production of the weir can be done inexpensively and the operation of the device can be ensured in a particularly simple manner.

Advantageously, the weir has cover means in its upper end region facing away from the bottom region of the container. With these it can be achieved that the coating bath, in which turbulences are introduced by the electromagnetic excitation by the inductors, calms down. According to one embodiment, it is provided that the covering means are designed as wall sections which extend parallel to the bottom region of the container.

Another embodiment provides that the cover means are formed as a plate having a gap-shaped recess for the passage of the metal strand.

The closure means, in particular the weir, preferably communicate with manual, pneumatic or hydraulic actuating means; the actuating means may be associated with a plant controller which causes the flow of molten coating metal to release or interrupt the flow of metal to the metal strand and / or guide channel.

In the drawings, embodiments of the invention are shown.

Fig. 1

schematisch den Schnitt durch eine Schmelztauch-Beschichtungsvorrichtung mit einem durch diese hindurch geführten Metallstrang,

Fig. 2

die perspektivische Ansicht eines zweiteilig ausgebildeten Wehres,

Fig. 3

die perspektivische Ansicht eines einteilig ausgebildeten Wehres,

Fig. 4

schematisch den Schnitt durch die Schmelztauch-Beschichtungsvorrichtung mit zweiteilig ausgebildetem Wehr, wobei dieses mit Abdeckmitteln ausgestattet ist, und

Fig. 5

die perspektivische Ansicht eines einteilig ausgebildeten Wehres mit Abdeckmitteln.

Show it:

Fig. 1

1 is a schematic section through a hot-dip coating device with a metal strand guided through it;

Fig. 2

the perspective view of a two-piece weir,

Fig. 3

the perspective view of a one-piece weir,

Fig. 4

schematically shows the section through the hot-dip coating device with two-part trained weir, this being equipped with cover means, and

Fig. 5

the perspective view of a one-piece weir with covering.

1 schematically shows a hot-dip coating device with a metal strand 1 guided through it.

The device has a container 3 which is filled with molten coating metal 2. This may be, for example, zinc or aluminum. To be coated metal strand 1 in the form of a steel strip passes through the container 3 in the conveying direction R vertically upwards. It should be noted at this point that it is also possible in principle that the metal strand 1, the container 3 passes from top to bottom. For the passage of the metal strand 1 through the container 3, this is open in the bottom area; Here is a guide channel. 4

So that the molten coating metal 2 can not flow down through the guide channel 4, located on both sides of the metal strand 1, two electromagnetic inductors 5, which generate a magnetic field, which counteracts the gravitational force of the coating metal 2 and thus seals the guide channel 4 downwards.

The inductors 5 are two oppositely disposed alternating field or traveling field inductors, which are operated in the frequency range from 2 Hz to 10 kHz and establish an electromagnetic transverse field perpendicular to the conveying direction R. The preferred frequency range for single-phase systems (AC field inductors) is between 2 kHz and 10 kHz, that for multi-phase systems (eg traveling field inductors) between 2 Hz and 2 kHz.

In the bottom region 6 of the container 3, a closure means 7 or 7 'designed in two parts as an embodiment according to FIG. 1 is arranged in the form of a weir. The two parts 7, 7 'of the weir are movable parallel to the bottom of the container 3 in the direction of the double arrow. For carrying out a movement actuation means 11 are provided, which are illustrated here only schematically as piston-cylinder units; just as any other type of actuator can be used.

The weir 7 or 7 'is presently designed as a divided into two parts box, the two halves 7 and 7' can cooperate so that they seal the region of the guide channel 4 in the bottom portion 6 of the container 3. This situation is sketched in FIG. Consequently, the coating metal 2 can not penetrate to the guide channel 4 or to the metal strand 1. This closed position of the weir 7 or 7 'is particularly important for two operating cases:

First, this position is taken before the coating system is started up. The metal strand 1 then moves - without that coating metal 2 can approach it - in the conveying direction R up, and the inductors 5 are activated. Only then are the two weir parts 7 or 7 'moved in the direction of the double arrow away from the metal strand 1, so that coating metal 2 can penetrate to the metal strand 1 and into the region of the guide channel 4 through the box opening thereby. Since the inductors 5 are activated, there is no escape of coating metal 2 down through the guide channel 4. The weir 7, 7 'thus encloses first the downwardly open guide channel 4 and thus the passing through this metal strand 1 to an optimized height the bottom portion 6 of the container 3, so that no coating metal 2 can flow in the direction of the guide channel 4. With the start of the coating process, the weir 7, 7 'is then opened, so that the coating metal 2 to the metal strand 1 and thus in the guide channel 4, which is now electromagnetically sealed by the inductors 5, can flow in time and volume optimized.

On the other hand, the weir 7, 7 'then has meaning, if there is a power failure and the inductors 5 (eg until the start of an emergency generator) can no longer perform their task, namely the guide channel 4 down through the built-up to seal electromagnetic field. In this case, the two weir parts 7, 7 'in the direction of the double arrow on the metal strand 1 to move until they touch and form the box-shaped cover around the metal strand 1 around. Consequently, no further coating metal 2 can get more to the metal strand 1 and the guide channel 4 more, whereby a mechanical seal of the coating channel 4 is ensured. As a result, no coating metal can escape downwards out of the guide channel 4.

In Fig. 2, the weir 7, 7 'again outlined in a perspective view, in the closed state. The double arrows indicate in which direction with respect to the conveying direction R of the metal strand 1, the two weir parts 7, 7 'can be moved, including the actuating means 11, s. Fig. 1, serve. It can be seen that in the bottom area of the weir 7, 7 'a Passage opening for the metal strand 1 is present; in the illustrated closed position of the weir 7, 7 'is nevertheless ensured that no coating metal 2 can enter the metal strand 1 and the guide channel 4.

Since the weir 7, 7 'is exposed to the coating metal, it is for a stable and reliable operation of the weir 7, 7' advantageous if it consists of as few individual parts. While the solution according to FIG. 1 or FIG. 2 provides for a two-part weir 7, 7 ', FIG. 3 shows that the weir 7 can also be formed in one piece. The box-shaped weir 7 then sets in the state in which it is closed, on the bottom 6 of the container 3 and thus seals the guide channel 4 from. To open the weir 7, it is vertically upwards, ie in the conveying direction R, moves, to which in turn the actuating means 11 are used.

For carrying out a coating process for producing a high-quality coated metal strand, it is advantageous if it is ensured that the surface of the coating bath remains as quiet as possible. This is therefore not guaranteed from home, because the electromagnetic inductors 5 induce a flow in the coating metal 2 by the generated magnetic fields.

In order to calm the surface of the coating bath, it is provided according to the exemplary embodiment according to FIG. 4 that cover means 9 are provided in the end region 8 of the weir 7, 7 ', with which care is taken that the currents generated by the inductors 5 do not continue to spread in the direction of the bathroom surface.

The turbulence caused by the electromagnetic seal in the guide channel 4 or in the container 3 of the liquid coating metal 2 can thus be kept away by the design of the weir 7, 7 'and in particular by the cover 9.

In the case that the weir 7 is integrally formed, the following is shown in Fig. 5 shown possibility: Here, the weir 7 is provided with a recess 10 in the upper region, which allows passage of the metal strand 1. The currents generated in the coating metal 2 by the inductors 5 are here by the covering means 9, which here almost a complete encapsulation of the inner region of the weir 7 to the rest of the coating bath held held. With this configuration, it is possible to optimally calm the bath surface and thus ensure a high-quality coating.

In the event of a malfunction and in particular in case of failure of the electromagnetic inductors 5, the weir 7 is closed by the actuating means 11, so that there is no danger that the coating metal 2 expires from the container 3.

LIST OF REFERENCE NUMBERS

1

Metal strand (steel strip)

2

coating metal

3

container

4

guide channel

5

inductor

6

Bottom area of the container

7

closure means

7 '

closure means

8th

End region of the closure means

9

covering

10

recess

11

actuating means

R

conveying direction

Claims (9)

1. Device for hot-dip coating of a metal strip (1), particularly a steel strip, in which the metal strip (1) is guided vertically through a container (3) receiving the molten coating metal (2) and through an upstream guide channel (4), with at least two inductors (5), which are arranged on either side of the metal strip (1) in the region of the guide channel (4), for producing an electromagnetic field for restraining the coating metal (2) in the container (3), characterised by a closure means (7, 7'), which is arranged above the guide channel (4) in the base region (6) of the container (3) and which is positionable in a first setting in which the flow of molten coating metal (2) to the metal strip (1) and/or to the guide channel (4) can be released and is positionable in a second setting in which the flow of molten coating metal (2) to the metal strip (1) and/or to the guide channel (4) can be interrupted, wherein the closure means (7, 7') is constructed as a weir movable relative to the base region (6) of the container (3).
2. Device according to claim 1, characterised in that the weir comprises two cooperating parts (7, 7') respectively movable perpendicularly to the surface of the metal strip (1).
3. Device according to claim 1, characterised in that the weir is movable in transport direction (R) of the metal strip (1).
4. Device according to claim 3, characterised in that the weir is of integral construction and has the form of a tank.
5. Device according to one of claims 1 to 4, characterised in that the weir (7, 7') has cover means (9) in its upper end region (8) remote from the base region (6) of the container (3).
6. Device according to claim 5, characterised in that the cover means (9) are constructed as wall sections extending parallel to the base region (6) of the container (3).
7. Device according to claim 5, characterised in that the cover means (9) are constructed as a plate which has a gap-shaped recess (10) for passage of the metal strip (1).
8. Device according to one of claims 1 to 7, characterised in that the closure means (7, 7'), particularly the weir, are connected with manual, pneumatic or hydraulic actuating means (11).
9. Device according to claim 8, characterised in that the actuating means (11) are connected with a plant control which allows release or interruption of the flow of molten coating metal (2) to the metal strip (1) and/or to the guide channel (4).

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