Apparatus and method for heat treating metal strip

Abstract

The subject of the invention constitutes a strip treatment installation for the continuous heat treatment of a metal strip (6) having an annealing furnace and a subsequent heatable over-aging chamber (11), in which the metal strip (6) is guided via a number of vertically spaced deflection rollers (12, 12', 13, 13') so that the metal strip passes through the over-aging chamber (11) in a serpentine manner. According to the invention, at least one deflection roller (12', 13') is vertically movable, so that the length or the residence time of the metal strip (6) in the over-aging chamber (11) can be set. The invention also relates to a method for heat treatment of a metal strip (6).

Description

[Technical Field]

[0001] The subject of the present invention is a strip treatment installation for the continuous heat treatment of metal strip, comprising an annealing furnace followed by a heatable over-aging chamber, in which the metal strip is guided via vertically spaced rollers, so that the metal strip passes through the over-aging chamber in a serpentine manner. [Background technology]

[0002] Conventional strip processing equipment consists of several chambers in which the metal strip is first heated to an annealing temperature and held at this temperature for a predetermined time, possibly according to a predetermined temperature curve. Such annealing furnaces are well known. The metal strip is then cooled at a predetermined cooling rate to a predetermined overaging temperature (overaging temperature) and held at this temperature for a predetermined period of time. So-called overaging chambers are used to hold the metal strip at a predetermined temperature (overaging temperature) for a precisely defined time. These chambers are often also called "holding chambers," "soaking chambers," or "partitioning chambers." The temperature should be as constant as possible in the overaging chamber and ranges from 150°C to 500°C, depending on the metal strip alloy. A protective gas atmosphere or a reducing atmosphere, such as a hydrogen-nitrogen mixture, usually prevails in these overaging chambers. The metal strip can then be cooled to room temperature or brought to the coating temperature in an electroplating installation, such as a galvanizing installation.

[0003] All these heat treatment steps affect the mechanical properties of the metal strip. In this case, it is important that the metal strip is not only heated to a specific temperature, but also held at that temperature in the overaging chamber for a precisely defined period of time. Similarly, the heating and cooling rates affect the strip properties. In addition, metal strips of different thicknesses or compositions also require different heat treatment parameters.

[0004] The residence time of the metal strip in the overaging chamber is determined by the strip speed and strip length in the overaging furnace. The strip length in a conventional overaging chamber is set by the arrangement of the deflection rollers, so that the residence time can only be adjusted via the strip speed. However, the strip speed can only be changed to a very limited extent, since each speed change naturally affects the production capacity, heating rate, and cooling rate.

[0005] DE 10 2015 001 438 A1 describes an installation for heat treatment in which a strip is guided through the loop, with an upper roller bridge being vertically movable to set different strip passing times.

[0006] US Patent Application Publication No. 20200131598 describes a vertical strip accumulator that is optionally heatable and is located between two annealing furnaces.

[0007] Korean Patent Publication No. 101951945 describes a vertical strip accumulator that can be placed before or after a furnace and is equipped with a device that prevents the strips from touching each other inside the strip accumulator. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] German Patent Application Publication No. 102015001438 [Patent Document 2] US Patent Application Publication No. 20200131598 [Patent Document 3] Korean Patent No. 101951945 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to provide a strip processing line in which the residence time of the metal strip in the overaging chamber can be set within a wide range, so that completely different metal strips can be processed on the same strip processing equipment and the optimum residence time in the overaging chamber can always be set. [Means for solving the problem]

[0010] This problem is solved by a strip processing installation according to claim 1, in which at least one deflecting roller is vertically movable in the overaging chamber, so that the length of the metal strip in the overaging chamber and thus the residence time of the metal strip in the overaging chamber can be set.

[0011] Therefore, the residence time can be set independently of the strip speed and by changing the strip length within the chamber, allowing one and the same strip processing equipment to meet different production requirements and be flexibly adapted to new conditions.

[0012] According to the invention, one or more movable deflection rollers are supported or fixed at predetermined positions to which they are moved to achieve a predetermined strip length. The roller support device is accommodated in a housing and can be advanced into the overaging chamber.

[0013] For the processing of a given metal strip, the deflecting roller remains in this predetermined position anyway. By supporting or fixing, the lifting mechanism for the deflecting roller can be unloaded.

[0014] Ideally, for a given strip format (strip thickness, strip composition, strip width) and a given thermal cycle (annealing temperature, cooling temperature, cooling rate, etc.), the strip speed is determined with respect to the maximum production capacity. Based on this strip speed, the required strip length in the overaging chamber is set, thereby achieving the optimal or thermal cycle-defined residence time of the metal strip in the overaging chamber.

[0015] The overaging chamber described here should not be confused with a conventional strip accumulator (looper). Loopers also have movable rollers and can accommodate different strip lengths. However, loopers are used to compensate for different strip speeds within the equipment. For example, if a new strip introduced into the equipment must be welded to the end of the previous strip and the strip must therefore be stopped, the strip accumulator releases the stored strip, thereby ensuring that the strip speed in the subsequent processing equipment does not change. However, such loopers are operated in ambient air at ambient temperature. Loopers are only used to compensate for different strip speeds and do not perform heat treatment.

[0016] It is advantageous if, in the overaging chamber according to the invention, the deflecting rollers are vertically movable, so that the accommodated strip length can be varied considerably.

[0017] Advantageously, one or more of the upper deflection rollers are vertically movable.

[0018] The overaging chamber is preferably heated electrically, for example by radiation, however the gas present in the overaging chamber can be sucked out, heated electrically and re-injected.

[0019] The overaging chamber according to the invention is arranged, for example, before the coating installation.

[0020] It is advantageous if a cooling section is arranged between the annealing furnace and the overaging chamber, since such a cooling step is necessary for many heat treatments.

[0021] The present invention, besides the device, also includes the following claims: 8 The present invention also relates to a method for continuously heat treating metal strip according to the present invention.

[0022] In this case, for the heat treatment of the metal strip in the overaging chamber, a residence time is determined and then by the movement of at least one deflecting roller, the strip length and therefore the residence time is set. In this case, the movable deflecting roller or the movable deflecting rollers are supported or fixed in a predetermined position by a roller support device, which is housed in a housing and can be advanced into the overaging chamber.

[0023] In this case, it is advantageous if the metal strip in the overaging chamber is heat treated in a hydrogen-nitrogen atmosphere.

[0024] In the following, several exemplary embodiments of the invention are explained with the aid of the drawings, in which the same reference numerals in the individual figures respectively denote the same parts of the installation. [Brief explanation of the drawings]

[0025] [Figure 1] Schematic diagram of a conventional overaging chamber [Figure 2] Example of an overaging chamber according to the invention with one movable upper deflection roller [Figure 3] Another embodiment of the overaging chamber according to the invention with one movable lower deflection roller [Figure 4] Example of an overaging chamber according to the invention with movable deflection rollers [Figure 5] Schematic of a possible roller movement system [Figure 6] Three different roller positions in the overaging chamber 11 [Figure 7] Example of a roller movement system [Figure 8] Example of a roller movement system [Figure 9] Schematic of heating or cooling of the overaging chamber [Figure 10] Schematic of heating or cooling of the overaging chamber DETAILED DESCRIPTION OF THE INVENTION

[0026] FIG. 1 illustrates a conventional overaging chamber 1. In this case, a metal strip 6 enters the overaging chamber 1 from the left and is deflected vertically upward by a lower fixed deflection roller 2. In the upper region of the overaging chamber 1, the metal strip 6 is then deflected 180° downward by an upper fixed deflection roller 3. The metal strip 6 thus snakes through the overaging chamber 1 until it is finally deflected horizontally by the final lower deflection roller 2 and leaves the overaging chamber 1. The interior of the overaging chamber 1 is typically regulated to a predetermined temperature between 150°C and 500°C. It is important that the interior of the overaging chamber 1 be maintained at as constant a temperature as possible. To reduce heat loss, the housing 4 of the overaging chamber 1 is equipped with thermal insulation 5. The overaging chamber is heated by an electrically heated radiant tube 7.

[0027] To achieve optimum material properties, the metal strip 6 should spend a certain period of time (dwell time) in the over-aging chamber 1 .

[0028] Since the lower and upper rollers 2, 3 of the overaging chamber 1 according to Figure 1 are fixed, the length of the strip accommodated is always the same, and therefore the residence time can only be varied by changing the strip speed.

[0029] FIG. 2 shows the construction of an over-aging chamber 11 according to the invention. The housing 14 is again equipped with a thermal insulation 15, and the metal strip 6 is again guided in a serpentine manner via the lower fixed deflection roller 12 and the upper fixed deflection roller 13. However, in this case the upper deflection roller 13' is vertically movable (movable). In this example, this upper deflection roller is lowered to half its height. The over-aging chamber in this example is heated by electrically heated radiant tubes 17. These radiant tubes 17 are not arranged in this case in the region of the movable deflection rollers 13', as this would prevent the latter from moving freely. Naturally, it is also conceivable that this over-aging chamber 11 is heated by a supplied hot gas, as will be explained further below.

[0030] Since the deflecting roller 13' is vertically movable, the strip length of the metal strip 6 in the over-aging chamber 11 can be changed by this means, and the residence time of the metal strip 6 in the over-aging chamber 11 can therefore be set without having to change the strip speed.

[0031] Usually, the optimum residence time for a given metal strip 6 is determined in advance. In that case, setting a given strip speed, the required strip length in the over-aging chamber 11 is calculated and set by the movement of the upper deflection roller 13' or upper deflection rollers 13'. Preferably, the movable upper deflection roller 13' is no longer moved (moved) during the processing of a given metal strip 6 but is fixed in its position.

[0032] FIG. 3 shows an overaging chamber 11 in which the lower deflection roller 12' is vertically movable.

[0033] 4 shows an embodiment in which several upper deflection rollers 13' are vertically movable, in which case the upper deflection rollers 13' are movable independently of one another.

[0034] FIG. 5 shows a possible embodiment for a mechanism that allows the deflection roller 12' or 13' to be moved vertically.

[0035] The bearing housings 23 of the movable upper deflection rollers 13' are each suspended on a chain 25 which is deflected by a gear 21 in the upper region of the over-aging chamber 11. A counterweight 20 is fixed to the other end of the chain 25. Both gears 21 are connected to each other via a shaft 22 and to a drive 18. Thus, by rotating the shaft 22, the upper deflection roller 13' can be moved vertically. If the lower deflection roller 12' is to be moved, the arrangement looks similar.

[0036] Next to the wall, here at different heights, roller support devices 19, 19' are provided. On these roller support devices, the deflecting rollers 13' or 12' can be arranged or fixed. Thus, during the heat treatment of a given metal strip 6, the chain 35 and the drive 18 can be unloaded. The fixed lower deflecting roller 12 and the shaft 22 are now supported outside the over-aging chamber 11. Therefore, their bearings 46 do not have to withstand high temperatures. The lower deflecting roller 12 has a drive 45.

[0037] FIG. 6 illustrates three different strip lengths in the over-aging chamber 11.

[0038] In the middle illustration, both upper deflection rollers 13' are in their uppermost position, so the strip length in the over-aging chamber 11 is at its maximum and the residence time at a given strip speed is longest.

[0039] In the left illustration, both movable upper deflection rollers 13' have been lowered somewhat, thus reducing the strip length and therefore the residence time at a given strip speed.

[0040] In the right image, both upper deflection rollers 13' are in their lowest position, where the strip length in the over-aging chamber 11 is shortest and therefore the residence time at a given strip speed is also minimized.

[0041] 7 and 8 show in more detail the adjustment mechanism for the movable deflection roller 12' or 13'. As the deflection roller 12' or 13' is located in the heated over-aging chamber 11, where temperatures of up to 500°C can prevail, the deflection roller is supported by high-temperature bearings 31. For the support of the shaft 22, a normal roller bearing 27 accommodated in a bearing housing 16 is sufficient. The bearing housing 26 is connected via a bearing support 29 to a support structure 30, on which the motor support 28 and the drive 18 are also mounted.

[0042] In order to be able to better compensate for possible thermal expansions, an expansion bellows 24 is arranged between the housing 14 of the overaging chamber 11 and the bearing housing 26 as a dust protection device.

[0043] 8 illustrates the function of the roller support devices 19, 19'. The roller support devices 19, 19' are housed in a housing 32 and can extend into the overaging chamber 11. The housing 32 here rests on a steel structure 44 via a substructure 33. Typically, several roller support devices 19, 19' are arranged at different heights across the chamber height, so that the deflecting rollers 12' or 13' can be supported at different heights.

[0044] FIG. 9 illustrates possible heating options for the overaging chamber 11. For a given metal strip 6, the overaging chamber 11 should have a temperature that is as constant as possible within it, which can be between 150°C and 500°C depending on the material and process. Because heat losses occur constantly, the chamber must be heated to maintain a temperature that is as constant as possible. Naturally, smaller temperature differences can exist within the overaging chamber 11, but these differences are usually only a few degrees Celsius. For heating, hot gas, e.g., an inert gas or a reducing gas such as a nitrogen-hydrogen mixture, is blown into the overaging chamber 11 via a laterally located supply box 34 and then sucked back in by a blower 36 via a suction box 35 on the opposite side. The gas is then fed either to an electric heater 40 or a heat exchanger 39 and re-entered into the overaging chamber 11 via a recirculation line 37. Via valves 38 and 41, the hot gas can be fed either to the heat exchanger 39 or to the electric heater 40. The gas temperature is increased again by means of an electric heater 40. If the gas is guided through a heat exchanger 39, it can also be cooled. This is necessary, for example, when switching from one steel grade to another. If, for example, the subsequent steel grade requires a lower over-aging temperature, the gas is cooled so that the optimum temperature is reached as quickly as possible in the over-aging chamber 11. At the same time, by moving the deflecting rollers 12' and 13', the strip length in the over-aging chamber 11 can be adapted to optimally heat treat the subsequent steel grade.

[0045] In Figure 10 the heating or cooling device of Figure 9 is again shown. Here it can be seen that the heat exchanger 39 is supplied with cooling water 43. The motor 42 for the blower 36 is also shown. In this figure a hydrogen-nitrogen mixture (HNX) is used as the heating medium. The present application relates to the invention described in the claims, but may also include the following as other aspects. 1. A strip treatment installation for the continuous heat treatment of a metal strip (6) having an annealing furnace followed by a heatable over-aging chamber (11), in which the metal strip (6) is guided through a plurality of vertically spaced deflection rollers (12, 12', 13, 13') so that the metal strip (6) passes through the over-aging chamber (11) in a serpentine manner, At least one deflection roller (12', 13') is vertically movable, thereby making it possible to set the length of the metal strip (6) accommodated in the over-aging chamber (11), and thereby making it possible to set the residence time of the metal strip (6) in the over-aging chamber (11). 2. 2. The strip processing equipment according to claim 1, wherein the deflecting rollers (12', 13') are vertically movable. 3. 3. Strip processing installation according to claim 1 or 2, characterized in that one or more upper deflection rollers (13') are vertically movable. 4. 4. The strip processing facility according to any one of 1 to 3 above, characterized in that one movable deflection roller (12', 13') or multiple movable deflection rollers (12', 13') can be supported or fixed at a predetermined position by a roller support device (19'). 5. 5. The strip processing facility according to any one of the above items 1 to 4, wherein the over-aging chamber (11) is electrically heatable. 6. 6. The strip treatment facility according to any one of the above items 1 to 5, wherein the over-aging chamber (11) can be heated by injecting heated gas. 7. 7. The strip treatment facility according to any one of the above items 1 to 6, wherein the overaging chamber (11) is arranged before the coating facility, preferably before the electroplating facility. 8. 8. The strip processing facility according to any one of 1 to 7 above, characterized in that a cooling section is disposed between the annealing furnace and the overaging chamber (11). 9. 1. A method for the continuous heat treatment of a metal strip (6) through an annealing furnace and a subsequent overaging chamber (11), in which the metal strip (6) is guided in a serpentine manner through vertically spaced deflection rollers (12, 12', 13, 13'), comprising: 1. A method according to claim 1, characterized in that for the heat treatment of the metal strip (6) in the over-aging chamber (11), a residence time is determined and that by moving at least one deflection roller (12', 13') in the over-aging chamber (11), the strip length of the metal strip (6) in the over-aging chamber (11) and therefore the residence time is set. 10. 10. The method according to claim 9, characterized in that the gas or gas mixture present in the over-aging chamber (11) is sucked in, heated and fed back into the over-aging chamber (11). 11. 11. The method according to claim 10, wherein the gas or gas mixture is heated electrically. 12. 12. The method according to any one of items 9 to 11 above, wherein the metal strip (6) in the over-aging chamber (11) is heat-treated at a temperature of 150°C to 500°C, preferably 400 to 500°C. 13. 12. The method according to any one of claims 9 to 11, characterized in that the metal strip (6) in the over-aging chamber (11) is heat-treated in a hydrogen-nitrogen atmosphere. [Explanation of symbols]

[0046] 1. Conventional overaging chamber 2 Lower fixed deflection roller 3 Upper fixed deflection roller 4. Housing 5. Insulation 6 metal strips 7 Radiation tube 11 Overaging chamber 12 Lower deflection roller (fixed) 12' Lower deflection roller (movable) 13 Upper deflection roller (fixed) 13' Upper deflection roller (movable) 14 Housing 15. Insulation 17 Radiation tube 18 Drive unit 19 Roller support device (exit) 19' Roller support device entering overaging chamber 11 20 Counterweight 21 Gears 22 axes 23 Bearing housing 24 Expansion Bellows 25 Chain 26 Bearing housing 27 Roller bearings 28 Motor Support 29 Bearing support 30 Support structure 31 High-temperature bearings 32 Housing for roller support device 19 33 Substructure 34 Supply Box 35 Suction Box 36 Blower 37 Recirculation Line 38 valves 39 Heat exchanger 40 Electric heater 41 Valve 42 Motor 43 Cooling water 44 Steel structure 45 Drive for deflection roller 12 46 Bearings for fixed deflection rollers

Claims

1. A strip treatment installation for the continuous heat treatment of a metal strip (6) having an annealing furnace and a subsequent heatable over-aging chamber (11), in which the metal strip (6) is guided through a plurality of vertically spaced deflection rollers (12, 12', 13, 13') so that the metal strip (6) passes through the over-aging chamber (11) in a serpentine manner, at least one of the deflection rollers (12', 13') being vertically movable so that the length of the metal strip (6) accommodated in the over-aging chamber (11) can be set, and thus the residence time of the metal strip (6) in the over-aging chamber (11) can be set, A strip processing facility characterized in that one movable deflecting roller (12', 13') or a plurality of movable deflecting rollers (12', 13') can be supported or fixed at a predetermined position by a roller support device (19, 19'), the roller support device (19, 19') is accommodated in a housing (32), and the roller support device (19, 19') can enter an over-aging chamber (11).

2. 2. Strip processing installation according to claim 1, characterized in that the deflecting rollers (12', 13') are vertically movable.

3. 3. Strip processing installation according to claim 1 or 2, characterized in that the upper deflecting roller or rollers (13') are vertically movable.

4. Strip treatment installation according to any one of claims 1 to 3, characterized in that the over-aging chamber (11) is electrically heatable.

5. Strip treatment installation according to any one of claims 1 to 4, characterized in that the over-aging chamber (11) is heatable by injection of heated gas.

6. Strip treatment plant according to any one of claims 1 to 5, characterized in that an over-aging chamber (11) is arranged before the coating plant.

7. 7. A strip treatment plant according to any one of claims 1 to 6, characterized in that a cooling section is arranged between the annealing furnace and the overaging chamber (11).

8. 1. A method for the continuous heat treatment of a metal strip (6) through an annealing furnace and a subsequent over-aging chamber (11), in which the metal strip (6) is guided in a serpentine manner through vertically spaced deflection rollers (12, 12', 13, 13'), a residence time for the heat treatment of the metal strip (6) in the over-aging chamber (11) is determined, and the strip length and therefore the residence time of the metal strip (6) in the over-aging chamber (11) is set by the vertical movement of at least one deflection roller (12', 13') in the over-aging chamber (11), The method is characterized in that one movable deflecting roller (12', 13') or a plurality of movable deflecting rollers (12', 13') can be supported or fixed at a predetermined position by a roller support device (19'), the roller support device (19, 19') is accommodated in a housing (32), and the roller support device (19, 19') can enter the over-aging chamber (11).

9. 9. A method according to claim 8, characterized in that the gas or gas mixture present in the overaging chamber (11) is sucked in, heated and fed back into the overaging chamber (11).

10. 10. The method of claim 9, wherein the gas or gas mixture is heated electrically.

11. A method according to any one of claims 9 to 10, characterized in that the metal strip (6) in the over-aging chamber (11) is heat treated at a temperature between 150°C and 500°C.

12. Method according to any one of claims 9 to 10, characterized in that the metal strip (6) in the over-aging chamber (11) is heat treated in a hydrogen-nitrogen atmosphere.

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