JP2006307244A - Sealing unit and sealing method for cooling process in continuous heat treatment facility for steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing unit and sealing method for cooling process in a continuous heat treatment facility for steel strip, wherein the lowering of quality in the steel strip and the lowering of cooling accuracy can be prevented at low cost by preventing the blowing-out of mist and generated steam from a cooling zone during cooling with the cooling water. <P>SOLUTION: A sealing body 19 forming a passing gap 21 for sealing fluid is arranged in between the passed steel strip 11 at a front process side near the hole in the cooling zone 5a, and a sealing space 22 is formed between the sealing body 19 and the cooling zone 5a, and a suction circulating unit 24 for sucking atmospheric gas. is arranged in the cooling space 22. In the circulating passage 25 for atmospheric gas sucked with the suction circulating unit 24, a mist removal unit 26 for atmospheric gas and a gas dispersing unit 27 for adjusting the atmospheric pressure in the sealing space with the atmospheric pressure in the cooling zone 5a and a circulation supplying passage for supplying the atmospheric gas after removing the mist with the mist removal unit 26 as the sealing fluid into the sealing unit are arranged. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sealing device and a sealing method for a cooling process in a steel strip continuous heat treatment facility, which includes a cooling process using water as a cooling medium, and more specifically, cooling in a cooling process in a steel strip continuous heat treatment facility. The present invention relates to a sealing device and a sealing method in a cooling process for preventing a mist and a generated steam from blowing out from the cooling process to the previous process.

For example, as shown in FIG. 3, the steel strip 11 unwound from the payoff reel 1 passes through the cleaning device 2 and is heated in a heating process 3 and a soaking process 4. The primary cooling process 5, the recuperation process 6, the overaging process 7, and the secondary cooling process 8 are passed through the post-treatment process 9 and wound around the tension reel 10. In the primary cooling step 5, gas, cooling water, or air is used as a cooling medium.
In this primary cooling step 5, a steel strip having a temperature of 500 to 700 ° C. is to be cooled and cooled at a cooling rate of 200 ° C./sec or less. Therefore, mist and generated water vapor (hereinafter referred to as “mist or the like” from the cooling space during cooling are used. Etc.)) may blow out. These have a dew point raising action, for example, between the soaking step immediately before the cooling step and the slow cooling step and the cooling step, the steel strip 11 is oxidized to directly reduce the surface quality of the steel strip 11, A build-up of the in-furnace roll due to oxidation of the steel strip 11 may occur, causing a problem of indirectly reducing the surface properties of the steel strip 11. Moreover, this mist etc. causes the temperature measurement field of the plate thermometer which measures the temperature of the steel strip 11 on the cooling process entrance side to be interrupted, resulting in a decrease in the temperature measurement accuracy, and thus causing a variation in the cooling accuracy. Therefore, it becomes difficult to stably achieve the uniform cooling of the steel strip 11, and the yield of the steel strip 11 cannot be secured stably at a high level.

As a countermeasure, for example, a method is known in which a sealing gas is injected at a right angle to the steel strip at the inlet of the cooling process to prevent mist and water vapor from blowing out from the cooling process. However, in this case, there is a problem that a large amount of sealing gas is required to ensure sufficient sealing performance.
Further, for example, in Patent Document 1, a seal body made of a seal roll or a partition plate is disposed so as to sandwich a steel strip at the boundary between the cooling process and the preceding and following processes, and gas is discharged into the gap between the steel strip and the seal body. Disclosed is a sealing device in which a nozzle is installed so that a seal gas jet can be sprayed across the entire width of the steel strip. Further, the seal gas jet velocity is made larger than the speed of the cooling medium from the opposing cooling process. Is also disclosed.
However, in the invention described in Patent Document 1, for example, nitrogen gas from another system is used as the seal gas in the embodiment, but in order to improve the sealing performance, a flow rate larger than the flow rate of the cooling medium is ensured. Therefore, there is a problem that a large amount of sealing gas is required to increase the cost. Further, in this case, a large amount of the sealing gas enters the cooling process and increases the pressure in the cooling process, and it is necessary to further increase the supply amount of the sealing gas to ensure the sealing performance. There is a concern that the cooling may become unstable (decreased) due to the sealing gas entering the cooling process.

In recent years, for example, in the automobile industry, the need for high-strength steel sheets with a tensile strength of 780 MPa or higher, for example, has been increasing in order to improve fuel efficiency by reducing the weight of the vehicle body and ensure safety during a collision. Requests are also increasing.
In order to obtain such a high-strength steel sheet, the cooling rate is usually higher in the rapid cooling process (primary cooling process) after the soaking process or after the soaking annealing process of the continuous heat treatment equipment than in the case of a general steel strip. The desired strength is ensured by significantly increasing the size and quenching.
For rapid cooling to obtain such a high-strength steel sheet, water is used as a cooling medium such as air-water cooling, water spray cooling, or water dip / quenching (quenching) cooling in order to obtain a large cooling rate. Since the cooling load is large, it is necessary to increase the amount of cooling water, and the amount of spray water and generated water vapor is much higher than when cooling ordinary general steel strips, and the blowout flow rate is also significantly higher. .

For this reason, the cooling water and the generated steam are likely to blow out from the rapid cooling process to the slow cooling process or the soaking process immediately before the rapid cooling process, which has a remarkable dew point raising action and oxidizes the steel sheet. The degree of obstruction of the visual field of the plate thermometer is large, and the temperature measurement of the plate thermometer tends to vary.
This variation in the plate temperature on the entry side of the rapid cooling process also affects the cooling accuracy in the rapid cooling process, resulting in variations in the steel strip temperature on the exit side of the rapid cooling process, leading to variations in steel strip quality and product yield. The degree of impact on the steel strip is much more remarkable than that of general steel strips, so it is necessary to prevent mist from the rapid cooling process and the generation of generated steam to prevent steel plate oxidation and improve cooling accuracy. .

Although the application of the sealing device of the invention described in Patent Document 1 can be considered in the cooling process of the continuous heat treatment equipment for obtaining the TS1470 MPa class high-strength steel sheet, when this is used, it is described in Patent Document 1 above. Since the problem of applying the sealing device of the present invention becomes more prominent, it is difficult to apply it as it is.
The current countermeasure is to increase the pressure in the slow cooling process and soaking process just before the rapid cooling process, but the controllable pressure has an operational upper limit, so it has not been fully resolved. .
Japanese Patent Laid-Open No. 10-298667

  The present invention is cooling in the cooling process of a continuous heat treatment equipment for steel strip using cooling water (herein, water and a mixture of water and gas, hereinafter also simply referred to as “cooling water”) as a cooling medium. In addition, mist and generated steam are prevented from blowing out to the soaking process and slow cooling process before the cooling process, and due to the deterioration of the surface quality due to the oxidation of the steel strip in the soaking process and the slow cooling process. Prevents deterioration of steel strip quality (surface properties) due to build-up of in-furnace rolls, and prevents low cost cooling due to variations in temperature measurement accuracy of the thermometer on the inlet side of the cooling process The present invention provides a sealing device and a sealing method for a cooling process in a continuous heat treatment facility for a steel strip.

In order to solve the above-described problems, the present invention has the following (1) to (5).
(1) In a continuous heat treatment facility for a steel strip having a cooling structure using a cooling water as a cooling medium and having a sealing structure with a sealing gas that prevents mist and steam from blowing out from the cooling process to the previous process side, A seal space is formed between the seal body and the cooling zone so that a sealing body is formed between the sealing plate and the cooling zone. A seal gas injection device is disposed on the upstream side of the seal space at a pre-process side to inject the seal gas obliquely toward the plate steel strip and to enter the seal space through the insertion gap. A suction circulation device for sucking the atmosphere gas composed of the seal gas and the mist and water vapor from the cooling zone, the atmosphere gas mist removal device disposed in the circulation path of the atmosphere gas sucked by the suction circulation device, and the seal Space pressure A pressure adjusting device having a gas diffusing device for adjusting the gas, and a circulation supply path for supplying the gas after mist removal by the mist removing device as a seal gas to the seal gas injection device, Sealing device for cooling process in continuous heat treatment equipment.
(2) A sealing device for a cooling process in a continuous heat treatment facility for steel strips, characterized in that, in (1), the sealing body forming the seal space is a roll disposed opposite to the sheet steel strip.
(3) In (1) or (2), the seal gas injection device is connected to an inert gas supply device from another system via a mixing device or a switching device, and the inert gas is used as a sealing fluid. A sealing device for a cooling process in a continuous heat treatment facility for steel strip, characterized in that it is configured.

(4) In the sealing method of the cooling process of the continuous heat treatment equipment for the steel strip, which prevents the blowing of water mist and water vapor from the cooling process using the cooling water as the cooling medium to the previous process side by the seal gas jet flow. A seal space is formed on the front process side in the vicinity of the inlet of the cooling zone of the process and has a gap between the sheet metal strip and the seal gas to communicate with the cooling zone, and the seal gas is slanted toward the plate steel strip. Is injected into the seal space via the inlet gap, and the atmosphere gas consisting of the inlet seal gas in the seal space and the mist and water vapor from the cooling zone is sucked from the seal space, and the pressure in the seal space is reduced. Adjusting the pressure in the cooling zone to a pressure range that does not cause an excessive rise, removing the mist in the suction atmosphere gas and circulating it as a seal gas, sealing the cooling process in the continuous heat treatment equipment for the steel strip Law.
(5) In (4), an inert gas is used in combination as a seal gas, and the sealing method for the cooling step in the steel strip continuous heat treatment facility.

In the present invention, the sealing gas sucked from the sealing space and the atmospheric gas consisting of mist and water vapor from the cooling zone are circulated and used as the sealing gas after mist removal, greatly reducing the amount of inert gas used from other systems. This can greatly reduce the sealing gas cost.
Also, because the atmospheric gas pressure in the sealing space (or cooling zone) is adjusted so that the cooling accuracy of the cooling zone is not hindered, the pressure is adjusted by sucking the atmospheric gas (for example, by diffusion or inert gas replenishment). Thus, it is possible to stably seal the sealing space without hindering the cooling accuracy in the cooling zone.
In addition, it can prevent the temperature measurement visibility from deteriorating due to the mist from the cooling process and the generation of generated water vapor, and reduce the variation in the temperature measurement accuracy of the plate temperature at the inlet side of the cooling process, ensuring stable cooling accuracy. When cooling either general steel strips or high-tensile steel strips, it is possible to reduce the temperature variation of the steel strip obtained by cooling, and to produce a good quality product with excellent surface properties and little variation in tensile strength. Can ensure stability.

In the cooling process of the steel strip continuous heat treatment equipment, the present invention forms, for example, a roll on the front side near the inlet of the cooling zone to form a seal space, and a low dew point seal gas is injected into the seal space. Then, an atmosphere gas (hereinbelow referred to as “atmosphere gas”) consisting of water, water vapor and seal gas blown from the cooling zone being cooled into the seal space flows into the soaking process side, for example, from the seal space. It is to be sealed so that it does not.
In this case, the atmospheric gas is sucked from the seal space and the pressure in the seal space is adjusted to the optimum range so that the atmospheric gas does not excessively flow back from the seal space to the cooling zone and impair the cooling accuracy in the cooling zone.
The atmospheric gas sucked from the seal space is circulated and used as the seal gas. Therefore, the mist (herein, “micro mist”, hereinafter referred to as “mist”) is removed and the dew point is lowered before the seal gas is injected into the seal gas injection device. High dew point atmosphere by supplying and injecting into the seal space obliquely from the outside near the inlet of the cooling zone toward the sheet steel strip while considering the combined use of inert gas from another system It is configured to prevent the gas from flowing from the cooling process to the previous process.
Since sufficient sealing performance can be ensured even when the pressure in the cooling zone is large, it can be applied to a cooling process of a continuous heat treatment facility for cooling from a general steel strip to a high-strength steel strip.

Hereinafter, when the present invention is applied to a primary cooling process using air and water as a cooling medium in a continuous heat treatment facility for a high-strength steel strip (hereinafter abbreviated as “steel strip”). Will be described more specifically with reference to FIG.
In FIG. 1, 5a is a cooling zone of the cooling step 5, and the steel strip 11 which has been soaked from 500 to 700 ° C. from the soaking step 4 is passed downward, and the diagonally upward air disposed on both sides thereof. A plurality of steam nozzles (slit nozzles) 14 having water jets are sprayed with steam 15 to cool both sides of the steel strip 11 at a cooling rate of 200 ° C./s or less and quench, and the next step (not shown). Pass through. Most of the air after cooling rises to steam 17 which is a high dew point and rises (partly falls as water and is collected and circulated). The pressure in the cooling zone 5a during cooling is about 200 Pa.

Here, the steel strip 11 in the soaking step 4 and the cooling step 5 passes through the plate space 16 that is blocked from the outside air. The cooling zone 5a has a cooling space 12 wider than the passage space 16 from the soaking step 4, but the steam 17 fills the cooling space 12 and flows out of the cooling zone 5a to the soaking step 4 side. And
When the high dew point water vapor 17 flows through the plate passing space 16 to the soaking process 4 side, as described above, the steel strip 11 passed through the soaking process 4 is oxidized to reduce the quality, or the furnace roll There is a great concern that the quality of the steel strip 11 is further deteriorated due to the occurrence of build-up.
In addition, the degree of obstruction of the temperature measuring field of the plate thermometer 18 on the inlet side of the cooling process is increased, the temperature measurement of the plate thermometer 18 is likely to vary, and the cooling accuracy in the cooling zone 5a is improved due to the deviation of the cooling start point. Variations may occur and cooling accuracy may be reduced.

Therefore, in the present invention, the sealing body is arranged so that the plate steel strip 11 is sandwiched and opposed to the plate plate space 16 near the inlet of the upper end portion of the cooling zone 5a (the upper portion of the air-water collision region to the steel strip 11). The seal roll 19 is disposed close to the sheet steel strip 11 so as to form a gap 21 for the jet of the seal gas 20 and communicates with the cooling zone 5a on the outside near the inlet of the cooling zone 5a. A seal space 22 is formed.
The seal gas 20 is injected obliquely (in this case, an angle of about 30 degrees) from the slit nozzle 23 a bent downward to the seal gas injection device 23 and sealed through the insertion gap 21. It is made to pass into the space 22 and the inflow of the water vapor 17 from the cooling zone 5a to the soaking process 4 side is prevented by this jet of the seal gas 20.
The seal roll 19 used here is effective to rotate the jet of the seal gas 20 in the direction of pushing into the seal space 22, but it may be a roll that does not rotate, and a seal body other than the roll (for example, a seal plate). Can also be used.

In the case where the seal space 22 is filled with the jet gas of the seal gas 20 and the atmospheric gas due to the water vapor 17 from the cooling zone 5a, and the pressure in the seal space 22 becomes excessively higher than the atmospheric pressure in the cooling zone 5a. Since the atmospheric gas tends to flow into the cooling zone 5a and the cooling accuracy in the cooling zone 5a cannot be secured stably, the pressure in the seal space 22 is managed.
Specifically, a suction circulation device (blower) 24 that sucks atmospheric gas from the side wall portion of the seal space 22 on the seal roll 19 side is arranged, and the pressure is adjusted by adjusting the suction amount or radiating the seal space 22. By reducing the internal pressure to be lower than the set pressure in the cooling zone 5 a and circulating and using the atmospheric gas sucked from the seal space 22 as the seal gas 20, the cost of the seal gas 20 is reduced.

  Here, the atmospheric gas is sucked from the side wall in the vicinity of the seal roll 19 in the seal space 22 as shown in FIGS. 2 (a) and 2 (b). In order for the injected seal gas 20 jet to flow toward the side wall of the seal space 22 in the region near the seal roll 19 while effectively blocking the rising flow of the water vapor 17 blown out from the cooling zone 5a into the seal space 22. This is due to the finding that it is advantageous to suck the atmospheric gas at the side wall of this region.

The atmospheric gas sucked from the seal space 22 contains a large amount of mist and has a high dew point. When the gas is circulated as it is as it is, the oxidation of the steel strip 11 on the inlet side of the cooling process or the plate thermometer 18 is performed. Therefore, the mist removal device 26 provided in the suction circulation path 25 by the suction circulation device 24 removes the mist, lowers the dew point, and supplies it to the seal gas injection device 23 in a circulating manner. .
A diffusion device 27 is provided in the circulation supply path 25 for circulation supply, and a pressure gauge 28 is provided in the seal space 22 (and the cooling zone 5a), so that the pressure in the seal space 22 (and the cooling zone 5a) is excessive. If there is a concern that the amount of atmospheric gas after mist removal will be dissipated, the pressure of the jet of the seal gas 20 passing through the seal space 22 is adjusted, and the inflow of the seal gas 20 into the cooling zone 5a (excess penetration) ) To ensure stable cooling accuracy in the cooling zone 5a.

  As the mist removing device 26, for example, a device such as a finned heat exchanger is disposed in the suction circulation path 25, the sucked atmospheric gas is cooled, the mist is removed, the dew point is lowered, and the seal gas 20 is circulated and used. . In order to reduce the capacity of the suction circulator 24, this mist removal is advantageously performed before the suction circulator 24 in the vicinity of the seal space 22.

The suction port (nozzle) for sucking the atmospheric gas from the seal space 22 can be provided in the seal roll 19 when the seal roll 19 is not rotated. In this case, the space is saved and the installation cost is low. it can.
It is also effective to use the seal roll 19 as a cooling body through the refrigerant, cool the atmospheric gas by its cooling action, remove the mist in the seal space 22 and discharge it.
Further, as the sealing gas 20 to be used, the atmospheric gas sucked from the sealing space 22 is circulated and used by removing the mist. However, there is a case where sufficient sealing performance cannot be ensured by this alone, or a low dew point may be desired. . In this case, a non-oxidizing gas (hereinafter referred to as “inert gas”) having a low dew point such as a mixed gas of N ₂ + H ₂ or N ₂ gas generally used as a non-oxidizing atmosphere gas from another system is used in combination. Therefore, it is considered to lower the dew point of the seal gas 20.
Therefore, a supply path of an inert gas supply device (not shown) is connected to the seal gas injection device 23 through a switching supply or mixed supply device 29 of an inert gas from another system.

In the continuous heat treatment equipment for the steel strip as shown in FIG. 3, the sealing device of the present invention configured as shown in FIG. ) And a TS1470 MPa grade steel strip 11 having a thickness of 0.2 to 3 mm and a width of 600 to 1800 mm soaked at a temperature of 500 to 700 ° C. from the soaking step 4 at a speed of 50 to 400 m / min. A flow rate of 2 to ³⁰ Nm ³ / min from a plurality of air-water nozzles (slit nozzles) 14 passing through the cooling zone 5 a and having obliquely upward air-water injection ports arranged on both sides thereof, the injection pressure of water 0.5 MPa, In the case where the steel strip 11 is cooled on both sides at a cooling rate of 0 to 200 ° C./s and quenched by injecting air 10 kPa of air 10 kPa, and passing through the next step (not shown), the cooling step The sealing method (example) was implemented. The injection angle α of the seal gas 20 was set to 30 degrees, and the penetration gap 21 between the seal rolls 19 was set to 120 mm.

In this embodiment, the pressure of the cooling zone 5a during cooling is set to 200 Pa that can ensure stable cooling, and the sealing gas 20 by an inert gas is sealed at a flow rate of 100 to 300 Nm ³ / min and the injection pressure is ³ kPa from the start of cooling. The space 22 is passed through and sealed so that the atmospheric gas is not blown back in the soaking process, and then the pressure in the sealing space 22 rises so that the atmospheric gas does not flow back to the cooling zone 5a. Atmospheric gas is sucked and the pressure of the seal space 22 is adjusted to 200 Pa. The sucked gas is mist removed and circulated to obtain a seal gas 20 with a flow rate of 100 to 300 Nm ³ / min and an injection pressure of ³ kPa. The seal was continued and kept in the seal space 22. During this time, the use of inert gas was stopped.
As a result,
(1) During cooling in the cooling zone 5a, the atmospheric gas from the seal space 22 is not blown out to the soaking process 4 side, and no deterioration in quality due to oxidation is observed in the steel strip 11 passing through the seal space 22 It was.
(2) Since there is no deterioration in the visibility of the inlet side thermometer 18 in the cooling step 5, temperature measurement accuracy can be secured stably, and the inflow of atmospheric gas to the cooling zone 5a can be prevented, and the pressure in the cooling zone 5a can be secured stably. Thus, the cooling accuracy was ensured stably, and the steel strip 11 having desired characteristics was stably obtained.

The present invention is not limited to the above-described sealing device and sealing method example. For example, in the above example, the sealing device of the present invention is applied to a cooling process using air / water as a cooling medium after the soaking process, but is also applied to a cooling process using cooling water as a cooling medium. It can also be applied to a cooling step subsequent to the slow cooling step.
Further, the structure, arrangement, sealing gas, and injection conditions of the sealing device of the present invention are within the range satisfying the claims of the present invention, depending on the steel strip conditions to be cooled, the type of cooling medium, the cooling conditions, and the like. There are some changes.

Cross-sectional explanatory drawing which shows the principal part structural example in the example of the sealing device of the cooling process in the continuous heat treatment equipment of the steel strip of this invention. 1A is a cross-sectional explanatory view showing an example of a flow state of seal gas and water vapor from a cooling zone in the seal space in the seal apparatus example of FIG. 1, and FIG. 2B is an Aa-Ab arrow in FIG. FIG. Side surface explanatory drawing which shows the example of arrangement | positioning of the continuous heat treatment equipment of the steel strip which has a cooling process to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pay-off reel 2 Cleaning apparatus 3 Heating process 4 Soaking process 5 Primary cooling process 5a Cooling zone 6 Reheating process 7 Overaging process 8 Secondary cooling process 9 Post-processing process 10 Tension reel 11 Steel strip 12 Cooling space 13 No. 14 Air Water nozzle 15 Air water 16 Passing plate space 17 Water vapor 18 Plate thermometer 19 Seal roll 20 Seal gas 21 Passing gap 22 Seal space 23 Seal gas injection device 23a Slit nozzle 24 Suction circulation device 25 Suction circulation path 26 Mist removal device 27 Radiation Device 28 Pressure gauge 29 Switching or mixing supply device

Claims (5)

  In a continuous heat treatment facility for a steel strip that has a cooling process using cooling water as a cooling medium and has a sealing structure with a seal gas that prevents mist and steam from blowing out from the cooling process to the previous process side, the cooling zone inlet of the cooling process A seal body that forms a gap for the seal gas between the sheet steel strip is disposed on the front side in the vicinity to form a seal space that communicates with the cooling zone between the seal body and the cooling zone. A seal gas injection device that injects the seal gas obliquely toward the sheet steel strip toward the front plate side of the seal space and enters the seal space through the insertion gap flows into the seal space. A suction circulator for sucking atmospheric gas consisting of seal gas and mist and water vapor from the cooling zone, an atmospheric gas mist removing device disposed in a circulation path of the atmospheric gas sucked by the suction circulator, and a pressure in the seal space Adjust A continuous heat treatment of a steel strip, characterized in that a pressure adjusting device provided with a gas diffusion device and a circulation supply path for supplying the gas after mist removal by the mist removal device as a seal gas to the seal gas injection device Sealing device for cooling process in equipment.   The sealing device for a cooling process in a continuous heat treatment facility for steel strips according to claim 1, wherein the seal body forming the seal space is a roll disposed oppositely across the sheet steel strip.   The seal gas injection device is connected to an inert gas supply device from another system via a mixing device or a switching device, and the inert gas can be used together as a sealing fluid. A sealing device for a cooling process in the continuous heat treatment equipment for steel strips according to 1 or 2.   In the sealing method of the cooling process of the continuous heat treatment equipment of the steel strip, which prevents the blowing of water and water vapor from the cooling process using the cooling water as the cooling medium to the previous process side by the seal gas jet flow, the cooling zone of the cooling process A seal space is formed on the front process side in the vicinity of the inlet of the steel plate and has a gap between the sheet metal strip and the seal gas to communicate with the cooling zone, and the seal gas is injected obliquely toward the sheet metal strip. The seal space is passed through the entrance gap, and the atmosphere gas consisting of the admitted seal gas in the seal space and the mist and water vapor from the cooling zone is sucked from the seal space, and the pressure in the seal space is changed to the pressure in the cooling zone. A method for sealing a cooling process in a continuous heat treatment facility for a steel strip, wherein the pressure is adjusted so as not to excessively increase, the mist in the suction atmosphere gas is removed, and the gas is circulated and used as a seal gas.   The sealing method of the cooling process in the continuous heat treatment equipment for steel strip according to claim 4, wherein an inert gas is used in combination as the sealing gas.

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