RU2844385C2 - Device and method for heat treatment of metal strip - Google Patents

Abstract

FIELD: performing operations.

SUBSTANCE: subject of the present invention is a strip processing device that serves for continuous heat treatment of a steel strip, as well as a method for continuous heat treatment of a steel strip. Device comprises an annealing furnace and located downstream of heated overageing chamber (11), wherein it is possible to guide steel strip (6) in overageing chamber (11) by a plurality of guide rollers (12, 12', 13, 13') spaced apart vertically so that steel strip (6) passes through overageing chamber (11) along meander path, wherein at least one guide roller (12', 13') is movable in the vertical direction so as to enable adjustment of the length of steel strip (6) in overageing chamber (11) and, consequently, the duration of stay of steel strip (6) in overageing chamber (11), wherein movable guide roller (12', 13') or movable guide rollers (12', 13') are installed or fixed in certain position on roller supports (19, 19'), wherein roller supports (19, 19') are arranged in case (32) and can be fitted into overageing chamber (11). Method comprises guiding steel strip (6) along a meander path in overageing chamber (11) by guide rollers (12, 12', 13, 13') spaced apart vertically, wherein for heat treatment of steel strip (6) preset duration of its stay in overageing chamber (11), and wherein by moving at least one guide roller (12', 13') in the vertical direction, adjusting the steel strip length and, consequently, steel strip (6) residence time in overageing chamber (11), wherein steel strip (6) is subjected to heat treatment in overageing chamber (11) at temperature of 150 °C up to 500 °C.

EFFECT: control of duration of metal strip stay in overageing chamber.

12 cl, 10 dwg

Description

Field of technology to which the invention relates

The subject of the present invention is a strip processing device which serves for continuous thermal processing of a metal strip, comprising an annealing furnace and a heated overaging chamber located after it. In this case, the metal strip is guided in the overaging chamber by several rollers located at a distance from each other vertically, and thus passes through the overaging chamber along a meander trajectory.

State of the art

Conventional strip processing devices consist of several chambers in which the metal strip is first heated to the annealing temperature and held at this temperature for a certain time. It is also possible to maintain a certain temperature curve. Such annealing furnaces are well known. The metal strip is then cooled at a specified cooling rate, brought to a certain over-aging temperature and held at this temperature for a specified period of time. The so-called over-aging chambers therefore serve to hold the metal strip at a certain temperature (over-aging temperature) for a precisely defined time. Such chambers are also often called "holding chambers" or "simmering chambers" or "separating chambers". The temperature in the over-aging chamber should be as constant as possible and, depending on the alloy from which the metal strip is made, ranges from 150°C to 500°C. These overaging chambers usually also have a protective gas atmosphere, i.e. a reducing atmosphere, such as a hydrogen-nitrogen mixture. The metal strip can then be cooled to ambient temperature or, for example, in galvanizing plants, in particular in galvanizing plants, it can be brought to the coating temperature.

All these heat treatment operations affect the mechanical properties of the metal strip. It is important that the metal strip is not only heated to a certain temperature, but also held in the overaging chamber at a given temperature for a precisely defined period of time. The properties of the strip are also affected by the heating and cooling rates. In addition, different thicknesses and different compositions of metal strips require different heat treatment parameters.

The residence time of the metal strip in the overaging chamber is determined by the speed of the strip and the length of the strip contained in the overaging furnace. The length of the strip in a traditional overaging chamber is determined by the arrangement of the guide rollers, so the residence time can only be adjusted by changing the speed of the strip. However, the speed of the strip can only vary to a very limited extent, since each change in speed naturally affects the productivity, heating rate and cooling rate.

DE 102015001438 A1 describes a heat treatment device through which a strip is passed in the form of a loop. The upper roller bridge is mounted so that it can be moved vertically to adjust the residence time of the strip.

US 2020/0131598 A1 describes a vertical loop accumulator, which is provided with a heating option and which is installed between two annealing furnaces.

KR 101951945 B1 describes a vertical loop accumulator which can be installed before or after the furnace and which contains a device which prevents the strip from touching each other in the loop accumulator.

The objective of the present invention is to provide a strip processing line in which the duration of the metal strip's stay in the overaging chamber can be adjusted within wide limits, which will make it possible to process completely different metal strips in one installation, while the optimal duration of the strip's stay in the overaging chamber can always be adjusted.

Disclosure of the essence of the invention

This task is solved by means of a strip processing device according to paragraph 1 of the invention formula. At least one guide roller is installed in the overaging chamber with the possibility of moving in the vertical direction, which allows adjusting the length of the metal strip contained in the overaging chamber. This provides the possibility of adjusting the duration of the metal strip's stay in the overaging chamber.

In this way, the strip dwell time can be set independently of the strip travel speed, namely by changing the length of the strip contained in the chamber. Thanks to this, the same strip processing device can meet different production requirements and flexibly adapt to new conditions.

According to the invention, one or more movable guide rollers are supported or fixed in a certain position in which they are installed to ensure a given strip length. The roller supports are located in the housing and can be introduced into the overaging chamber.

For processing a specific metal strip, the guide rollers remain in this predetermined position in any case. Since the guide rollers are supported or fixed on supports, their lifting device can be relieved.

Ideally, for a given strip format (thickness, composition and width of the strip) and a given temperature cycle (annealing temperature, cooling temperature, cooling rate, etc.), the strip travel speed is set to achieve maximum productivity. Based on this strip travel speed, the required length of the strip contained in the overaging chamber is adjusted to ensure an optimal, i.e., temperature cycle-determined, residence time of the metal strip in the overaging chamber.

The overaging chamber described here should not be confused with a traditional looper. Such accumulators also contain movable rollers and can receive strips of different lengths. However, they serve to equalize different speeds of movement of the strip in the device. If, for example, it is necessary to weld a new strip introduced into the device with the end of the previous strip, and for this it is necessary to stop the strip, the loop accumulator, despite such a stop, ensures an unchanged speed of movement of the strip in the following devices, giving up the accumulated strip. However, such accumulators operate at ambient temperature and in the ambient air. They serve only to equalize the speeds of movement of the strip and do not carry out any heat treatment. Preferably, in the overaging chamber according to the invention, several guide rollers are mounted with the possibility of movement in the vertical direction. This allows a significant variation in the length of the strip contained in the overaging chamber.

It is preferable that one or more upper guide rollers are mounted so as to be able to move in the vertical direction.

The overaging chamber is preferably provided with electrical heating, for example by means of tubular radiators. At the same time, the gas contained in the overaging chamber can also be pumped out, heated electrically and then pumped back in.

The overaging chamber according to the invention can be located, for example, before the coating application unit.

It is preferable that a cooling section be provided between the annealing furnace and the overaging chamber, since an appropriate cooling operation is required for many heat treatment variants.

The invention, along with the device, also relates to a method for continuous heat treatment of a metal strip according to paragraph 8 of the invention formula.

In this case, for the thermal treatment of the metal strip in the overaging chamber, the residence time is set, and then, using the method according to the invention, the length of the strip contained in the chamber and thus also the residence time is adjusted using at least one guide roller. After this, one or more movable guide rollers are mounted or fixed on roller supports. In this case, the said roller supports are arranged in a housing and can be introduced into the overaging chamber.

It is preferable that the heat treatment of the metal strip is carried out in an overaging chamber in a hydrogen-nitrogen atmosphere.

Brief description of the drawings

The following is a description of several embodiments of the invention with reference to the accompanying drawings, which show:

Fig. 1 - schematic view of the overaging chamber according to the state of the art;

Fig. 2 - an embodiment of the overaging chamber according to the invention with a movable upper guide roller;

Fig. 3 - another embodiment of the overaging chamber according to the invention with a movable lower guide roller;

Fig. 4 - an embodiment of the overaging chamber according to the invention with several movable upper guide rollers;

Fig. 5 - schematic view of a possible roller movement system;

Fig. 6 - three different positions of the rollers in the overaging chamber 11;

Fig. 7 and 8 - embodiment of the roller movement system;

Fig. 9 and 10 - schematic representation of heating or cooling of the overaging chamber 11.

In the drawings, identical parts of the device are designated by identical reference numbers.

Implementation of the invention

Fig. 1 shows a re-aging chamber 1 according to the state of the art. In this case, a metal strip 6 is introduced from the left into the re-aging chamber 1 and is turned vertically upwards by means of a lower, fixed guide roller 2. Then, in the upper part of the re-aging chamber 1, the metal strip 6 is turned downwards by 180° by means of an upper, fixed guide roller 3. In this way, the metal strip 6 passes through the re-aging chamber 1 along a meander path until it is finally turned horizontally by the last lower guide roller 2 and exits the re-aging chamber 1. A predetermined temperature is set inside the re-aging chamber 1, which is typically between 150°C and 500°C. It is important that the temperature in the re-aging chamber 1 is maintained as constant as possible. To reduce heat loss, the body 4 of the overaging chamber 1 is provided with thermal insulation 5. The overaging chamber is heated using tubular emitters 7 with electric heating.

To obtain optimal material properties, metal strip 6 must be kept in overaging chamber 1 for a specified period of time (duration of stay).

Since in the overaging chamber 1 according to Fig. 1 the lower and upper rollers 2, 3 are mounted fixedly, the processed strip length is always constant. Therefore the residence time can be changed only by changing the speed of movement of the strip.

Fig. 2 shows an embodiment of the overaging chamber according to the invention. In this case, the housing 14 is also provided with thermal insulation 15, and the metal strip 6 is also moved along a meander trajectory through the overaging chamber 11 by means of lower fixed guide rollers 12 and upper fixed guide rollers 13. However, in this case, an upper guide roller 13' is provided, mounted so that it can move in the vertical direction (movable roller). In the example shown, it is lowered to half the height. In this example, the overaging chamber is heated by means of tubular radiators 17 with electrical heating. In this case, the said tubular radiators 17 are located outside the range of movement of the guide roller 13', since they would create an obstacle to the freedom of movement of this guide roller 13'. Of course, it is also possible to heat the overaging chamber 11 with supplied heated gas, as described below.

The possibility of moving the guide roller 13' in the vertical direction makes it possible to change the length of the metal strip 6 contained in the overaging chamber 11.

Thus, the residence time of the metal strip 6 in the overaging chamber 11 can be adjusted without the need to change the speed of movement of the strip.

As a rule, the optimum residence time for a certain metal strip 6 is specified in advance. Then, at a given value of a certain speed of movement of the strip, the required length of the strip contained in the overaging chamber 11 is calculated, which is adjusted by moving one or more upper guide rollers 13'. It is preferable that these movable upper guide rollers 13' do not move during the processing of a certain metal strip 6, but are in a fixed position.

Fig. 3 shows a re-aging chamber 11, in which the lower guide roller 12' is mounted with the possibility of movement in the vertical direction.

Fig. 4 shows an embodiment in which several upper guide rollers 13' are mounted so as to be able to move in the vertical direction.

In this case, the upper guide rollers 13' can be moved independently of each other.

Fig. 5 shows a possible embodiment of a device for moving guide rollers 12' or 13' in the vertical direction.

The bearings 23 of the upper movable guide roller 13' are suspended on chains 25, which are turned by means of toothed wheels 21, installed in the upper part of the overaging chamber 11. Counterweights 20 are attached to the other end of the chains 25. Both toothed wheels 21 are connected to each other by a shaft 22 and are connected to a drive 18. Thus, by turning the shaft 22, the upper guide roller 13' can be moved in the vertical direction. The device for moving the lower guide roller 12' would look similar.

On the side wall at different heights, supports 19, 19' for rollers are provided. These supports allow the guide rollers 13' or 12' to be supported or fixed. Therefore, during the heat treatment of a certain metal strip 6, the chains 25 and the drive 18 can be unloaded. The fixed lower guide roller 12 and the shaft 22 are in this case located outside the overaging chamber 11. Therefore, the bearings 46 do not have to withstand high temperatures. The lower guide roller 12 has a drive 45.

Fig. 6 shows three different variants of the length of the strip contained in the overaging chamber 11.

In the middle image, both upper guide rollers 13' are in the extreme upper position, thereby ensuring the maximum length of the strip in the overaging chamber 11 and, consequently, the longest stay at a given strip travel speed.

In the left image, one of the two movable upper guide rollers 13' is slightly lowered, so that the strip length and, consequently, the residence time at a given strip travel speed are reduced.

In the right image, both upper guide rollers 13' are in the lowest position. In this case, the length of the strip contained in the overaging chamber 11 is the shortest, and therefore the residence time at a given strip travel speed is also minimized.

In Fig. 7 and 8 the adjusting device for the movable guide rollers 12' or 13' is shown in more detail. Since the guide rollers 12' or 13' are located in the heated overaging chamber 11, where the temperature can reach 500°C, they are mounted on high-temperature bearings 31. For mounting the shaft 22, a conventional roller bearing 27 is sufficient, which is located in the bearing housing 26. The bearing housing 26 is connected to the support structure 30 via the bearing support 29. The motor support 28 and the drive 18 also rest on this support structure 30.

In order to better equalize possible thermal expansion and provide protection against dust, a compensation bellows 24 is provided between the housing 14 of the overaging chamber 11 and the housing 26 of the bearing.

Fig. 8 shows the operation of the support 19, 19' for the roller. The support 19, 19' for the roller is located in the housing 32 and can be introduced into the overaging chamber 11. The housing 32 in this case is mounted on the steel structure 44 by means of the base 33. As a rule, several supports 19, 19' for the rollers are located at different heights along the height of the chamber, therefore the guide roller 12' or 13' can be fixed at different heights.

Fig. 9 shows a possible variant of heating the overaging chamber 11. For the processing of a certain metal strip 6, a constant temperature should be ensured in the overaging chamber, which, depending on the strip material and the processing parameters, is between 150°C and 50°C. Since heat losses always occur, it is necessary to heat the chamber in such a way as to maintain a constant temperature level, if possible. Of course, small temperature differences can occur in the overaging chamber 11, which, however, as a rule, are only a few degrees Celsius. For heating, a heated gas, for example an inert gas or a reducing gas, in particular a hydrogen-nitrogen mixture, is fed into the aging chamber 11 through a side supply box 34 and is again removed by a fan 36 through an exhaust box 35, installed on the opposite side. This gas then passes through the electric heater 40 or through the heat exchanger 39 (HE) and is again directed through the recirculation line 37 into the overaging chamber 11. By means of the valves 38 and 41 (TCV), the supply of heated gas into the heat exchanger 39 or into the electric heater can be regulated. The electric heater 40 (EH) makes it possible to increase the temperature of the gas again. If the gas passes through the heat exchanger 39, it can also be cooled. This is necessary, for example, in the case of a changeover from one grade of steel to another. If, for example, a lower overaging temperature is required for the next grade of steel, the gas is cooled in order to ensure the optimum temperature in the overaging chamber 11 as quickly as possible. At the same time, by moving the guide rollers 12' and 13', the length of the strip contained in the overaging chamber 11 can be adjusted in such a way as to ensure the optimum heat treatment of the next grade of steel.

Fig. 10 shows again the heating and cooling device of Fig. 9. It can be seen that the heat exchanger 39 is provided with a water cooling system 43. In addition, the motor 42 of the fan 36 is shown. In this embodiment, a hydrogen-nitrogen mixture (HNX) is used as a coolant.

LIST OF REFERENCE DESIGNATIONS

1. Aging chamber according to the state of the art

2. Lower fixed guide roller

3. Upper fixed guide roller

4. Body

5. Thermal insulation

6. Metal strip

7. Tubular emitter

11. Aging chamber

12. Lower guide roller (fixed)

12'. Lower guide roller (movable)

13. Upper guide roller (fixed)

13'. Upper guide roller (movable)

14. Body

15. Thermal insulation

17. Tubular emitter

18. Drive

19. Roller support (extended)

19'. Roller support inserted into the overaging chamber 11

20. Counterweight

21. Gear wheel

22. Shaft

23. Bearing housing

24. Compensating bellows

25. Chain

26. Bearing housing

27. Roller bearing

28. Engine support

29. Bearing support

30. Support structure

31. High temperature bearing

32. Support housing 19 for roller

33. Foundation

34. Supply box

35. Exhaust duct

36. Fan

37. Recirculation pipeline

38. Valve

39. Heat exchanger

40. Electric heater

41. Valve

42. Engine

43. Water cooling system

44. Steel structure

45. Guide roller drive 12

46. Bearing of fixed guide roller 12.

Claims (12)

1. A strip processing device for continuously heat treating a steel strip (6), comprising an annealing furnace and a heated overaging chamber (11) located after it, wherein the possibility of guiding the steel strip (6) in the overaging chamber (11) is provided by several guide rollers (12, 12', 13, 13') located at a distance from each other vertically, so that the steel strip (6) passes through the overaging chamber (11) along a meander trajectory, wherein at least one guide roller (12', 13') is mounted with the possibility of moving in the vertical direction in order to thus provide the possibility of adjusting the length of the steel strip (6) in the overaging chamber (11) and, consequently, the duration of stay of the steel strip (6) in the overaging chamber (11), characterized in that the movable guide roller (12', 13') or movable guide rollers (12', 13') are mounted or fixed in a certain position on the supports (19, 19') for the roller, wherein the supports (19, 19') for the roller are placed in the housing (32) and are designed with the possibility of being introduced into the overaging chamber (11). 2. The device according to item 1, characterized in that several guide rollers (12', 13') are installed with the possibility of movement in the vertical direction. 3. The device according to item 1 or 2, characterized in that at least one upper guide roller (13') is installed with the possibility of movement in the vertical direction. 4. A device according to any one of paragraphs 1-3, characterized in that the overaging chamber (11) is designed with the possibility of electrical heating. 5. A device according to any one of paragraphs 1-3, characterized in that the overaging chamber (11) is designed with the possibility of heating by supplying heated gas. 6. A device according to any one of paragraphs 1-3, characterized in that the overaging chamber (11) is located before the installation for applying a coating, preferably before the installation for applying a galvanic coating. 7. A device according to any one of paragraphs 1-6, characterized in that a cooling section is installed between the annealing furnace and the overaging chamber (11). 8. A method for continuous heat treatment of a steel strip using a strip treatment device according to any one of claims 1 to 7, wherein the steel strip (6) is guided along a meander trajectory in the overaging chamber (11) by guide rollers (12, 12', 13, 13') installed at a distance from each other vertically, wherein for the heat treatment of the steel strip (6) the duration of its stay in the overaging chamber (11) is set, and wherein by moving at least one guide roller (12', 13') in the vertical direction the length of the steel strip and, consequently, the duration of the stay of the steel strip (6) in the overaging chamber (11) is adjusted, wherein the steel strip (6) is subjected to heat treatment in the overaging chamber (11) at a temperature from 150°C to 500°C. 9. The method according to item 8, characterized in that the gas or mixture of gases located in the overaging chamber (11) is pumped out, heated and fed back into the overaging chamber (11). 10. The method according to paragraph 9, characterized in that the gas or gas mixture is heated electrically. 11. The method according to item 9 or 10, characterized in that the steel strip (6) is subjected to heat treatment in an overaging chamber (11) at a temperature of 400°C to 500°C. 12. The method according to item 9 or 10, characterized in that the steel strip (6) is subjected to heat treatment in an overaging chamber (11) in a hydrogen-nitrogen atmosphere.