Method and device for continuous treatment of a metal strip

Abstract

This is a device for the continuous treatment of a metal strip (1), in particular a metal strip made of aluminum or an aluminum alloy, or of non-ferrous metal or a non-ferrous metal alloy, comprising at least one temperature control device (2) through which the metal strip (1) is suspended, and a strip position control device (7) with which the position of the metal strip (1) in the strip-travel plane and transversely to the strip-travel direction can be controlled or regulated. The temperature control device (2) has at least one inlet-side heating section (3) and one outlet-side cooling section (4). According to the invention, the strip position control device (7) is arranged within the cooling section (4).

Description

[0001] The invention relates to a device for the continuous treatment of a metal strip, in particular a metal strip made of aluminum (or an aluminum alloy) or of non-ferrous metal (or a non-ferrous metal alloy), comprising at least one tempering device designed as a strip floating furnace through which the metal strip is passed in a floating manner, and comprising a strip travel control device with which the position of the metal strip in the strip travel plane and transversely to the strip travel direction can be controlled or regulated. The strip floating furnace has at least one heating section on the inlet side and one cooling section on the outlet side. The metal strip preferably has a thickness of 0.1 mm to 6 mm.

[0002] The tempering device is a strip floatation furnace that has a heating section and a cooling section. The heating section usually consists of several heating zones (heating or holding zones), and the cooling section usually consists of several cooling zones. In such a tempering device, the metal strip is heated to a specific (target) temperature, held at this temperature for a specific time if necessary, and then cooled again. The passage through the furnace is contactless, with the strip being floated between nozzles (air nozzles) subjected to the appropriate air pressure. Cooling in the cooling zones can be achieved with air, water, or a combination of air and water. Such strip floatation furnaces with a heating section on the one hand and a cooling section on the other are known (see, for example, DE 198 04 184 A1).

[0003] DE 103 26 071 discloses a device for the continuous treatment of a metal strip, comprising at least one tempering device through which the metal strip is guided in a suspended manner and comprising a strip position control device with which the position of the metal strip in the strip travel plane and transversely to the strip travel direction can be controlled or regulated, wherein the tempering device has at least one heating section on the inlet side and one cooling section on the outlet side.

[0004] Such a device of the type described above for the continuous treatment of a metal strip with a tempering device or with a strip floatation furnace can, for example, be an annealing line or continuous annealing line in which the metal strip undergoes heat treatment for metallurgical reasons, e.g., to achieve specific strength and deformation properties. Alternatively, the device can also be a strip coating system or a strip coating line in which the heat treatment of the metal strip is not carried out in the sense of annealing, but rather to dry a coating on the strip, so that the furnace is then designed as a continuous dryer.

[0005] The metal strip is preferably aluminum or non-ferrous metal strip in a thickness range of 0.1 mm to 6 mm.

[0006] Since the metal strip is heated to temperatures close to its melting point, for example, in annealing lines, it is generally necessary to set a relatively low strip tension within the tempering device to avoid strip breakage. To this end, the strip tension is reduced, for example, on the inlet side in a set of tension rollers and, after cooling, is increased again on the outlet side in another set of tension rollers. In the tempering device (strip floatation furnace), the specific strip tension is, for example, 0.5 to 1 MPa. Since the strip can "run off" in the furnace, particularly at low strip tension, e.g., due to possible strip sabering, it is necessary to position the strip appropriately using a strip position control device, preferably to the strip center. Positioning therefore takes place in the strip travel plane, transverse to the strip travel direction. Such a strip travel control device typically has at least one control roller and suitable position measuring devices, e.g., a position sensor.Strip edge detection. In the systems known from practice, the strip tracking control device is located behind the tempering device, i.e. after the cooling section. In practice, the control roller is usually designed as a so-called PI strip center control, i.e. with a proportional P and an integral I component. The I component acts back on the furnace section and prevents the strip from wandering too far in the furnace. The control roller is usually located on a movable base frame. This rotates the roller about an imaginary pivot point or about an imaginary axis of rotation which lies in the furnace section and is perpendicular to the strip travel plane. The extent to which the roller is shifted from the center axis of the furnace section is the proportional component, and the extent to which the roller is misaligned is the integral component of the strip center control. If the roller is misaligned, the strip moves back towards the center of the strip due to the so-called winding effect.Such systems known from practice have generally proven themselves.

[0007] A system of the type described above is known, for example, from DE 103 37 502 B4. A furnace with heating and cooling zones is connected to a deflection roller for strip center control.

[0008] Furthermore, DE 103 26 071 A1 discloses a system in which a deflection device is arranged on the outlet side behind a strip floatation furnace, beneath which a water cup acts as a fluid seal. The deflection device can also simultaneously serve as a strip center control, with the strip position being detected by sensors arranged above and below the strip, and the movement of the strip center control for returning a strip running from the center position is carried out by means of a cylinder.

[0009] In practice, the rapidly growing demand for aluminum car body strips is creating a need to build increasingly powerful continuous annealing lines. To achieve higher production capacities, the strip runs through the treatment section at higher speeds. However, since only a limited amount of heat can be introduced into the strip per furnace zone, the tempering device would have to be longer for higher production capacities. Since the strip runs more easily due to the low strip tension in the furnace section, there is a risk with long furnace lengths that the conventional strip position control devices will no longer be sufficient to keep the strip running stable in the furnace. There is a risk that the strip will run sideways or hit the furnace structure. This can lead to undesirable strip damage or strip breakage, meaning that plants with increased production capacities cannot easily be implemented in this way.- This is where the invention comes in.

[0010] The invention is based on the object of creating a device for the continuous treatment of a metal strip of the type described above, which is characterized by an improved strip position control and which guarantees a perfect strip run, especially in long furnace sections.

[0011] To solve this problem, the invention teaches Device having the features of claim 1.The cooling section is divided into at least a first cooling section and a subsequent, spaced-apart second cooling section, wherein the strip position control device is arranged between the first cooling section and the second cooling section. According to the invention, the strip position control device is therefore no longer arranged on the output side behind the temperature control device and thus no longer after the last cooling zone, but is integrated into the cooling section by dividing it into two cooling section sections. In a first section, the strip is cooled down to such an extent that it can easily pass the strip position control device. The strip position control device is therefore located downstream of the first cooling section.The strip then passes through the second cooling section and subsequently the second section of the cooling zones, where it is cooled to the desired final temperature. This allows for a long furnace section and consequently long heating and cooling sections, increasing production capacity without having to significantly increase the free strip length in the low-tension zone. This reliably prevents impermissible strip path in the furnace.

[0012] The strip position control device itself can be designed in a conventional manner, thus allowing the use of conventional solutions. According to the invention, the specific positioning of the strip guide device within the furnace section or within the cooling section is crucial.

[0013] For example, the strip position control device for strip position control can have a conventional, adjustable deflection roller, e.g. a 90° deflection roller, or be designed as such. However, it is recommended that the deflection roller be provided with a suitable (high-)temperature-resistant coating, since the strip temperature between the first cooling section and the second cooling section is preferably 100°C to 200°C, particularly preferably 120°C to 150°C. As an alternative to a 90° control roller, another known type of strip center control can also be used, e.g. using a multi-roller control device, e.g. a three-roller control device or a control driver (e.g. as a pair of rollers). Suitable coatings are also preferably provided in this case. Preferably, the strip position control or strip center control is designed in a basically known manner as PI control. The control roller orThe multi-roller assembly is therefore mounted on a movable base frame in a generally familiar manner. This rotates the roller(s) around an imaginary pivot point, which in turn is located in the furnace section. The degree of displacement of the roller from the center axis of the furnace section is the proportional component, and the degree of inclination of the roller is the integral component of the belt center adjustment.

[0014] The strip processing system preferably has a first set of tension rollers on the inlet side, which is arranged upstream of the tempering device to reduce the strip tension. Furthermore, it is expedient to provide another set of tension rollers on the outlet side and consequently downstream of the tempering device, with which the strip tension is increased again, so that further process steps can follow, such as stretch leveling, cleaning, or edge trimming.

[0015] Optionally, it is within the scope of the invention for a (further) set of tensioning rollers to be arranged between the first cooling section and the second cooling section downstream of the strip position control device in order to increase the strip tension at this point. This has the advantage that the strip can pass through the second part of the cooling zones with a slightly increased strip tension. In this case, too, it is expedient to provide the rollers of such a roller set with appropriate temperature-resistant coatings. According to the invention, it is important that strip position control takes place between the first cooling section and the second cooling section. Optionally, it may be expedient to provide a further strip position control downstream of the second cooling section.This can be particularly useful if no additional tension roller set is provided between the first cooling section and the second cooling section, and consequently, the strip tension is also lower in the second cooling section. If a tension roller set is provided between the two cooling sections, and consequently the strip tension is already increased at this point, a second strip position control system may be omitted after the second cooling section.

[0016] Dividing the cooling section into two cooling sections results in both sections being (significantly) shorter than a single cooling section. Compared to conventional systems, this allows the entire temperature control system to be extended, meaning both the heating section and the entire cooling section can be extended.

[0017] The invention also relates to a method according to claim 7 for the continuous treatment of a metal strip with a device of the type described, wherein the metal strip is guided in a suspended manner through the heating section and the cooling section for thermal treatment. This method is characterized by that the position of the metal strip (within the strip travel plane and transversely to the strip travel direction) is controlled or regulated by a strip position control device arranged within the cooling section.

[0018] As already described, such a strip position control device is preferably equipped with suitable measuring devices and a feedback loop, so that true control of the strip position is achieved. However, the invention also encompasses embodiments that operate without measurement and / or feedback, so that the strip position is not regulated but merely controlled.

[0019] The length of the first cooling section is preferably dimensioned such that the metal strip has a temperature of up to 200 °C, e.g. 100 °C to 200 °C, between the first cooling section and the second cooling section, and consequently in the region of the strip position control device. The temperature is particularly preferably up to 150 °C, e.g. 120 °C to 150 °C. The length of the second cooling section can then be dimensioned, for example, such that the strip exits at a temperature of up to 70°, preferably up to 60 °C, e.g. 40 °C to 60 °C, so that further process steps, such as stretch straightening, cleaning or edge trimming, can follow without any problems.

[0020] The system according to the invention can, for example, be designed as an annealing line or be a component of an annealing line. The tempering device is then designed as an annealing furnace. Alternatively, the system can be designed as a strip coating system or be a component of a strip coating system. The tempering device is then designed as a dryer or drying furnace. In both cases, the furnaces / dryers are preferably designed as strip floatation furnaces.

[0021] The invention will be explained in more detail below with reference to drawings which merely represent exemplary embodiments. Fig. 1 shows a known strip treatment device according to the prior art in a simplified schematic representation, Fig. 2 shows a strip treatment device according to the invention in a simplified schematic representation and Fig. 3 shows a modified embodiment of the object according to Fig. 2 .

[0022] In order to clarify the inventive concept, it is advisable to first review the state of the art according to Fig. 1 to consider. Fig. 1shows a known strip treatment device for the continuous treatment of a metal strip, namely a thermal treatment. This device has a tempering device 2, which is designed as a strip floatation furnace. The metal strip 1 passes through this strip floatation furnace 2 without contact, as the strip is floated between upper and lower nozzles, which are subjected to appropriate air pressure. Details are not shown. The strip floatation furnace 2 has a heating section 3 on the inlet side and a cooling section 4 on the outlet side. The heating section is generally composed of several heating zones 3', while the cooling section is generally composed of several cooling zones 4', whereby the individual zones can be controlled individually or separately. In the heating zones, the metal strip is generally heated using air, so that the nozzles, e.g., the lower nozzles, can also perform temperature control in addition to their supporting function.In the cooling zones, cooling is usually also achieved by air or by a combination of air and water. In the case of an annealing line for aluminum strip for automotive bodywork purposes, the target temperature in the heating zone is, for example, approximately 550 °C to 570 °C. The heating zones therefore form heating and holding zones. It can be seen that the system has a set of tension rollers 5 on the inlet side, with which the strip tension is reduced, e.g. to a specific strip tension of, for example, 0.5 to 1 MPa. After the strip floatation furnace 2 or after the last cooling zone, the metal strip 1 is center-controlled by means of a strip position control device 7, i.e. the position of the metal strip is controlled in the strip travel plane and transversely to the strip travel direction. The strip tension is then increased again to the usual line level of, for example, a specific 10 to 20 MPa using a set of tension rollers 6 on the outlet side.Due to the low specific strip tension within the strip floatation furnace, it is necessary to bring the metal strip 1 to the strip center using the strip position control device 7.

[0023] If one wants to increase the production capacity of such a Fig. 1 To increase the capacity of the system shown, it is generally necessary to extend the strip flotation furnace. Fig. 1 In the state-of-the-art system shown, beyond a certain length of the strip floatation furnace, there is a risk that the strip position control device 7, e.g., the control roller 8, will no longer be sufficient, so that the strip path in the furnace may become unstable, i.e., the strip may run sideways or run into the furnace structure. This could lead to undesirable strip damage or strip breakage, so simply extending the strip floatation furnace is not advisable without additional measures.

[0024] According to the invention, the strip position control device 7 is therefore no longer arranged behind the tempering device 2 and consequently no longer behind the cooling section 4, but within the cooling section 4 itself. This is shown by the Fig. 2 and 3 which show embodiments of the invention. The Fig. 2 and 3 show again a strip treatment device with a tempering device 2, which has an inlet-side heating section 3 and an outlet-side cooling section 4. On the inlet side, a tension roller set 5 is provided and on the outlet side, another tension roller set 6 can be provided, which only in Fig. 3 , but not in Fig. 2is shown. The heating section 3 is in turn composed of several heating zones 3', while the cooling section 4 is composed of several cooling zones 4'. According to the invention, the cooling section 4 is divided into two cooling section sections, namely a first cooling section section 4a and a subsequent second cooling section section 4b. The strip position control device 7 is now arranged according to the invention between the first cooling section section 4a and the second cooling section section 4b. The metal strip is heated in the heating section 3 with the heating and holding zones 3' in a basically known manner to the desired temperature and the temperature can be maintained for a desired time. The heating section 3 therefore does not need to be modified compared to the prior art - apart from an extension.The heating section 3 is then followed by the first cooling section 3a, with which the metal strip is cooled down in a first stage, preferably to a temperature of 100 °C to 200 °C, e.g. 120 °C to 150 °C. After leaving the first cooling section 4a, the strip center control takes place with the aid of the strip center control device 7. In the embodiment according to . Fig. 2 This has a 90° control roller 8. In the embodiment according to Fig. 2Another tension roller set 9 is connected to increase the strip tension. The strip then passes through the second cooling section 4b, where it is cooled to the desired final temperature of, for example, 40 °C to 60 °C. This allows production capacity to be increased without significantly increasing the free strip length, thus preventing an impermissible strip path in the furnace. A further strip position control device and / or another tension roller set can be connected to the second cooling section 4b. This is shown in Fig. 2 not shown.

[0025] Fig. 3 shows a modified embodiment of the invention, in which the strip center control device 7 is designed as a three-roller strip center control with three rollers 10. Furthermore, in Fig. 3It is indicated that a further strip center control device 11 and a further tension roller set 6 can be arranged behind the second cooling section 4b. The additional strip center control device 11 behind the second cooling section 4b is useful because, in this embodiment, no tension roller set is arranged between the cooling sections 4a, 4b and therefore the second section 4b also operates with a lower strip tension.

[0026] If you compare, for example, the Fig. 1 and 2 , it can be seen that the furnace zones 3', 4' in the embodiment according to the invention have a total length which is greater than the length in the known embodiment according to Fig. 1Nevertheless, the free strip length is not increased, since the strip center control 7 is already connected to the first cooling section 4a. This allows both the heating section 3 and the cooling section 4 to be significantly extended compared to the prior art. However, by dividing the cooling section 4, cooling section sections 4a and 4b are created, each of which is (significantly) shorter than the heating section 3.

Claims

1. Device for continuous processing of a metal strip (1), particularly a metal strip made of aluminium or an aluminium alloy, or of non-ferrous metal or a non-ferrous metal alloy, having at least one thermal treatment apparatus, which is in the form of a strip flotation furnace (2) through which the metal strip (1) is floated, and having a strip position adjustment device (7), with which the position of the metal strip (1) can be controlled or adjusted in the strip running plane and transversely to the direction of advance of the strip, wherein the strip flotation furnace (2) has at least one heating line (3) on the infeed side and one cooling line (4) on the outfeed side, characterised in that the strip position adjustment device (7) is arranged in the cooling line (4) wherein the cooling line (4) is divided into at least a first cooling line section (4a) and a second cooling line section (4b) downstream therefrom, wherein the strip position adjustment device (7) is arranged between the first cooling line section (4a) and the second cooling line section (4b), wherein the strip adjustment device comprises a movable deflection roller or has the form of such or is in the form of a multi-roller assembly.

2. Device according to claim 1, characterised in that a further strip position adjustment device (11) is arranged after the second cooling line section.

3. Device according to claim 1 or 2, characterised in that the strip position adjustment device (7, 11) comprises a movable deflection roller (8), for example a 90° deflection roller, or has the form of such for adjusting the position of the strip.

4. Device according to claim 1 or 2, characterised in that the strip position adjustment device (7, 11) is in the form of a three-roller device.

5. Device according to any one of claims 1 to 4, characterised in that a tension roller assembly (11) located downstream from the strip position adjustment device (7) is arranged between the first cooling line section (4a) the second cooling line section (4b).

6. Device according to any one of claims 1 to 5, characterised in that the rollers (8, 9) of the strip position adjustment device (7) and / or of the tension roller assembly (11) are furnished with a thermally resistant coating.

7. Method for continuous processing of a metal strip using a device according to any one of claims 1 to 6, wherein the metal strip is passed in floating manner through the heating line and the cooling line to undergo thermal processing, characterised in that the position of the metal strip is controlled or adjusted with a strip position adjustment device arranged in the cooling line, wherein the strip position adjustment device is arranged between a first cooling line section and a second cooling line section.

8. Method according to either claim 7, characterised in that strip position is adjusted with a PI control having a proportional P-component and an integral I-component.

9. Method according to claim 7 or 8, characterised in that the strip position adjustment device is arranged in an area of the cooling line between the first cooling line section and the second cooling line section, in which the temperature of the metal strip reaches up to 200°C, for example 100°C to 200°C, preferably up to 150°C, for example 120°C to 150°C.

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