JP5776593B2 - Method and apparatus for cooling hot rolled coil - Google Patents

Description

  The present invention relates to a cooling method and a cooling device for cooling a hot-rolled steel sheet wound in a coil shape after hot rolling without causing rust.

  As shown in FIG. 1, in order to manufacture a hot-rolled steel sheet, a slab is heated to a predetermined temperature in a heating furnace 1, and the heated slab is rolled with a roughing mill 2 to form a rough bar. In a continuous hot finishing rolling mill 3 composed of a plurality of rolling stands, a hot rolled steel sheet 4 having a predetermined thickness is obtained. The hot-rolled steel sheet 4 coming out from the finish rolling mill 3 is cooled by supplying cooling water from above and below with a cooling device 5 installed on the run-out table, and then wound up with a winder 6 and coiled hot-rolled steel sheet. 7

  The coiled hot-rolled steel sheet after winding (hereinafter, also simply referred to as “coil”) has a temperature of about 500 to 650 ° C., and is therefore shipped after being cooled to room temperature in a coil place in a hot-rolling factory. A large amount of coils are cooled in the coil storage area, and since the high temperature coils are placed around the high temperature coils, the temperature around each coil becomes high and the cooling efficiency is lowered. It takes 5 days. For this reason, problems such as a shortage of places for placing the coils, a long period until shipment, and an increase in inventory occur.

  In order to shorten the coil cooling time, various methods for spraying cooling water have been proposed. However, if the cooling water is sprayed in a state where the coil surface temperature is 100 ° C. or lower, the cooling water is difficult to evaporate, so that the coil surface gets wet with water, and if left as it is, rust is generated on the steel sheet surface. If rust occurs, the appearance will be damaged and shipping will not be possible.

  For this reason, conventionally, as described in Patent Document 1, a water cooling method has been proposed in which the temperature and humidity around the coil are measured and the spray amount is controlled so that the steel sheet surface does not get wet. However, this method has a problem that cooling water is sprayed from a distance from the ceiling of the coil storage area and cooling efficiency is low, so that efficient cooling cannot be performed.

  Further, as described in Patent Document 2, a cooling method has been proposed in which one end of each width direction of one coil is cooled from both sides using a cooling nozzle. However, this method has a problem that the mist is not sufficiently spread, it is difficult to cool the entire coil, and the cooling efficiency is lowered.

JP-A-57-134207 Japanese Patent Application Laid-Open No. 5-177240

  That is, a mist having a small droplet particle size is effective in preventing wetting of the coil surface during water cooling. This is because the smaller the particle size of the droplet, the smaller the amount of heat necessary for evaporation, and the easier it is to evaporate. However, when the droplet particle diameter is reduced, there is a problem in that it is easily detached from the coil due to the influence of the surrounding wind, and the ejection distance is short.

  In order to improve the water cooling capacity, it is important to increase the injection flow rate per unit area of the mist (hereinafter referred to as “water density”). However, when a large volume object such as a coil is cooled, if the cooling capacity is high, the surface temperature is greatly lowered with respect to the central portion, and thus the surface is easily wetted. In particular, when the coil surface temperature is 100 ° C. or lower, the coil surface is easily wetted, and therefore it is important to suppress the decrease in the surface temperature.

  As described above, it has been difficult in the past to achieve both suppression of wetting of the coil surface and improvement of the cooling capacity. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cooling method and a cooling device that do not generate rust in a coil and perform cooling with high efficiency.

  In order to solve the above problems, the method for cooling a coiled hot-rolled steel sheet according to the present invention is a method for cooling a coiled steel sheet after being wound by a winder installed in a hot rolling line. It cools by spraying a cooling mist intermittently on the both ends of the width direction of this steel plate.

  In order to solve the above problems, a coiled hot-rolled steel sheet cooling device according to the present invention includes a mist nozzle that generates cooling mist in the cooling device used in the cooling method, and a coil that mounts the cooling mist on an air stream. And a blower that blows intermittently on the widthwise end of the steel plate.

  By using the cooling method and the cooling device of the present invention, water cooling that prevents wetting of the surface of the coiled steel sheet is possible. As a result, it is possible to prevent the occurrence of rust and highly efficient cooling, and the coil can be obtained in a short time. Can be shipped.

  In the cooling method and apparatus of the present invention, the cooling mist is preferably composed of droplets having a particle diameter of 20 μm or more and 40 μm or less. This is because, in order to prevent wetting of the coil surface during water cooling, a mist with a small droplet particle size is effective because it requires less heat and is easier to evaporate, but a liquid with a particle size of less than 20 μm is effective. Cooling mist consisting of droplets is easily removed from the coil due to the influence of the surrounding wind, and is difficult to spray over a wide area due to the short injection distance. Larger mist is effective because it takes a larger amount of heat to evaporate from the coil due to evaporation, and it is effective because it is sprayed over a wide area because the spray distance is long. This is because the coil surface is easily wetted.

  Further, in the cooling device of the present invention, the blower has a swing mechanism, and the cooling mist is sprayed widely and intermittently on a plurality of coiled steel plates by swinging the blower by the swing mechanism. Preferably there is. This is because the cooling mist can be sprayed widely and intermittently on many coiled steel plates with a small number of fans.

It is a block diagram which shows the outline of a normal hot rolling line. It is a perspective view which shows the outline of the movable cooling device of one Embodiment of the cooling apparatus of the coiled hot rolled steel plate of this invention used for one Embodiment of the cooling method of the coiled hot rolled steel plate of this invention. It is a perspective view which shows the outline of the coil group which consists of a plurality of coils stacked in two stages. It is a relationship diagram which shows the relationship between a droplet particle diameter and the wetting generation temperature of a coil. It is a relationship diagram which shows the temperature history of the low temperature part of a coil at the time of performing intermittent cooling and continuous cooling with a cooling mist, respectively, and a high temperature part, respectively. It is a figure which shows the outline of a non-movable and continuous cooling type cooling device. It is a figure which shows the outline of the movable cooling device of the said embodiment. It is a related line figure which shows the temperature history of the low temperature part of a coil, and the high temperature part at the time of cooling, respectively on the conditions of the Example of this invention, and Comparative Examples 1 and 3.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, FIG. 2 is an outline of the movable cooling device of one embodiment of the cooling device for the coiled hot-rolled steel sheet of the present invention, which is used in one embodiment of the method for cooling the coiled hot-rolled steel sheet of the present invention. FIG.

  As shown in FIG. 2, the cooling device 8 of the present embodiment includes, for example, a plurality of normal mist nozzles 10 at regular intervals in the circumferential direction, for example, around the blower opening of an axial flow type blower 9 in the blowing direction. (8 in the illustrated example) are arranged, and a water supply pipe (not shown) is connected to each mist nozzle 10. The reason why the mist nozzle 10 and the blower 9 are combined in this way is that the cooling mist having a small droplet particle diameter is light, so that it is difficult to reach far by receiving air resistance only with the momentum blown from the mist nozzle 10. This is because 9 can be carried far away on the air current blown out.

  In the cooling method of this embodiment, for example, as shown in FIG. 7, one cooling device 8 is installed on each side of the coil storage area on both sides of the mountain of the coils 7 stacked in two stages as shown in FIG. The cooling mist M is intermittently sprayed on both end faces in the steel plate width direction of the respective coils 7 of the two-stacked coil group to cool each coil 7. In order to ensure that the cooling mist M reaches the coils 7 stacked in two stages, depending on the size of the cooling device 8, for example, the diameter of the blower 9 is about 0.5 to 1 m and the center height is 0.1. In the case of about 5 to 1 m, it is preferable that the distance between the end faces in the steel plate width direction of the two stacked coils 7 and the cooling device 8 is, for example, about 1 to 2 m.

  The cooling device 8 here has a swing mechanism (not shown) such as a crank-type swing mechanism of a normal electric fan, for example, and, as shown by the arrow in FIG. A movable type capable of reciprocatingly swinging the blower 9 around the shaft. By the swing of the blower 9, a cooling mist M composed of water droplets as droplets over a wide range of coils stacked in two stages. Can be sprayed to cool the water.

  Here, when paying attention to the specific coil 7, the cooling mist M from the cooling device 8 does not hit the coil 7 because the blower 9 of the cooling device 8 swings the head in a direction deviating from the coil 7. The air cooling of the cooling device 8 and the water cooling while the cooling mist M from the cooling device 8 is hit are alternately performed by swinging the head in the direction in which the blower 9 of the cooling device 8 faces the coil 7. Hereinafter, this cooling method in which air cooling and water cooling are performed alternately is referred to as “intermittent water cooling method”.

  By the way, in the coil storage place, it is necessary to cool the coil 7 to 50 ° C., which is the coil cooling completion temperature, without wetting the coil surface. FIG. 4 shows the result of the investigation of the relationship between the droplet particle diameter of the cooling mist M and the wetting occurrence temperature of the coil surface by the inventor. As can be seen from this figure, in order to prevent wetting of the coil surface up to 50 ° C., the droplet diameter of the cooling mist M should be 40 μm or less. However, if the droplet particle diameter is less than 20 μm, the cooling mist M is easily detached from the coil 7 due to the influence of the surrounding wind, and it is difficult to spray over a wide range because the spray distance is short.

  When the coil 7 having a temperature of 600 ° C. and a weight of 25 ton per piece is subjected to intermittent cooling and continuous cooling with cooling mist M generated by using a mist nozzle 10 having a droplet particle diameter of 40 μm with cooling water having a water temperature of 30 ° C. The temperature history of the low temperature part and the high temperature part of the coil 7 is shown in FIG. In the figure, curve A shows intermittent cooling (low temperature part), curve B shows intermittent cooling (high temperature part), curve C shows continuous cooling (low temperature part), and curve D shows continuous cooling (high temperature part). However, water cooling is stopped when the lowest temperature portion of the coil 7 reaches 50 ° C. The cooling during intermittent cooling (A, B) is one in which water cooling for 1 minute in which the cooling mist M is sprayed on the coil 7 and air cooling for 1 minute in which the cooling mist M is not sprayed are alternately repeated. The cooling of (C, D) is to continuously blow the cooling mist M against the coil 7.

  When the lowest temperature portion of the coil 7 reaches 50 ° C., the temperature difference between the highest temperature portion and the lowest temperature portion of the coil 7 is 127 ° C. when continuous cooling is performed. On the other hand, it was 59 ° C. when intermittent cooling was performed. From this, it can be seen that by performing intermittent cooling, water cooling of the coil 7 can be performed until the temperature of the high temperature portion of the coil 7 is sufficiently lowered, and the cooling time can be short-circuited.

  Next, an example of the cooling method of the present embodiment is shown in FIG. 7 for the coil 7 of the coil group stacked in two stages as shown in FIG. One cooling device 8 is installed on each side of the mountain of the coil 7 and cooling mist M is intermittently sprayed on both end faces in the steel sheet width direction of each coil 7 of the two-stacked coil group. A case where cooling is performed will be described. The cooling start temperature of the coil 7 is 600 ° C., the weight per piece is 25 ton, the temperature of the cooling water generating the cooling mist M is 30 ° C., and the water cooling is performed when the lowest temperature of the coil 7 reaches 50 ° C. Stop.

  In the above example, when water cooling is performed using the movable cooling device 8 having a droplet diameter of the cooling mist M of 30 μm (intermittent cooling in which water cooling is performed for 1 minute and air cooling is performed for 1 minute), When air-cooling is performed without using 8, as Comparative Example 2, when water-cooling is performed using a non-movable cooling device 11 with a droplet diameter of the cooling mist M of 60 μm as shown in FIG. As Example 3, a comparison was made for each of the cases where water cooling was performed using a non-movable cooling device 11 having a droplet particle diameter of 30 μm as shown in FIG.

  The non-movable cooling device 11 has the same configuration as the movable cooling device 8 except that it does not have a swing mechanism and maintains the blower 9 and the mist nozzle 10 in a certain direction. .

  Table 1 shows the time until coil cooling is completed when cooling is performed under the conditions of the above-described example and comparative examples 1 to 3, and FIG. 8 shows cooling under the conditions of the above-described example and comparative examples 1 and 3. The temperature history of the low-temperature part and high-temperature part of a coil when each is performed is shown. In the figure, curve E is an example (low temperature part), curve F is an example (high temperature part), curve G is comparative example 1 (low temperature part), curve H is comparative example 1 (high temperature part), and curve I is a comparative example. 3 (low temperature part) and curve J indicate Comparative Example 3 (high temperature part), respectively. However, since the temperature history of Comparative Example 2 and Comparative Example 3 is the same, the temperature history of Comparative Example 2 is not shown.

  As shown in Table 1 and FIG. 8, in the cooling method of Comparative Example 1 (G, H), it took 87 hours to complete the cooling, and no rust was generated on the coil surface. In the cooling method of Comparative Example 2, it took 59 hours to complete the cooling, and rust was generated on the coil surface. Therefore, the coil 7 could not be shipped. In the cooling method of Comparative Example 3 (I, J), it took 59 hours to complete the cooling, and no rust was generated on the coil surface.

  On the other hand, in the cooling methods of the above Examples (E, F), it took 51 hours to complete the cooling, and no rust was generated on the coil surface. That is, according to the cooling method of the above embodiment, the cooling time of the coil 7 can be shortened by 8 hours as compared with the comparative example 3, the rust is not generated on the coil surface, and the number of cooling devices is also the comparative example 3. I was able to do it in half.

  As is apparent from the above description, according to the cooling device 8 of the present embodiment and the cooling method of the present embodiment using the same, the generation of rust during the cooling of the coil 7 in the coil storage area of the hot rolling factory. Prevention and shortening of the cooling time are possible.

  Although the present invention has been described based on the illustrated examples, the present invention is not limited to the above-described examples, and can be appropriately changed within the scope of the claims, for example, other embodiments of the present invention. In this cooling device, for example, a timer-controlled electromagnetic on-off valve is provided in the cooling water pipe connected to the mist nozzle 10 of the non-movable cooling device 11 used in the comparative examples 2 and 3, and the cooling mist M from the mist nozzle 10 is provided. For example, water cooling by continuous blowing for 1 minute and air cooling by blowing off for 1 minute may be repeated alternately.

  Further, for example, in the cooling method according to another embodiment of the present invention, the non-movable cooling device 11 arranged continuously facing each other without placing the coils 7 in the coil place of the hot rolling factory continuously blows out. The coil 7 may be intermittently cooled by passing the coil 7 back and forth between the cooling mists M on a conveyor.

  Further, for example, in the cooling device and the cooling method according to another embodiment of the present invention, the blower 9 of the movable cooling device 8 according to the above-described embodiment is supplied by, for example, feeding with a slip ring or supplying water to the mist nozzle 10 with a swivel joint. Alternatively, it may be configured so that it can be swung continuously instead of reciprocally swinging, and the coil 7 may be arranged around the movable cooling device 8 to perform intermittent cooling.

  And the length of the time of the water cooling and air cooling in the cooling device and cooling method of this invention may be suitably changed according to the temperature, humidity, etc. of a coil place.

  Thus, according to the cooling method and the cooling device of the present invention, water cooling that prevents wetting of the surface of the coiled steel sheet is possible, and as a result, it is possible to prevent the occurrence of rust and to achieve high efficiency cooling. Can be shipped.

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Coarse rolling mill 3 Finish rolling mill 4 Hot-rolled steel plate 5 Cooling device 6 Winding machine 7 Coiled hot-rolled steel plate 8 Movable cooling device 9 Blower 10 Mist nozzle 11 Non-movable cooling device M Cooling mist

Claims (5)

When cooling the coiled steel sheet after being wound by a winder installed in the hot rolling line,
A cooling method for a coiled hot-rolled steel sheet, wherein cooling is performed by spraying cooling mist intermittently on both ends in the width direction of the coiled steel sheet.   The method for cooling a coiled hot-rolled steel sheet according to claim 1, wherein the cooling mist comprises droplets having a particle size of 20 µm or more and 40 µm or less. In the cooling device used for the cooling method of Claim 1 or 2,
A mist nozzle for generating cooling mist,
A blower that intermittently blows the cooling mist on the end of the coiled steel plate in the airflow with the airflow,
An apparatus for cooling a coiled hot-rolled steel sheet.   The said cooling mist consists of a droplet with a particle diameter of 20 micrometers or more and 40 micrometers or less, The cooling apparatus of the coil-shaped hot-rolled steel plate of Claim 3 characterized by the above-mentioned. The blower has a swing mechanism,
The cooling apparatus for a coiled hot-rolled steel sheet according to claim 3 or 4, wherein a cooling mist is sprayed widely and intermittently on a plurality of coiled steel sheets by swinging the blower by the swing mechanism. .

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