KR19990052248A - Scale generation suppression apparatus and method of hot rolling mill - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for suppressing scale generation of a strip hot rolling mill. The present invention relates to a strip hot rolling mill (11-17) and a surface cooling device (41, 42, 43) installed at an entrance thereof. It is an object of the present invention to provide an apparatus and method for suppressing scale generation of a hot rolling mill, which is capable of improving the product quality by cooling the surface temperature of the strip and simultaneously suppressing the generation of scale by repeatedly surface cooling and finishing rolling. .

The present invention relates to a strip surface scale generation suppression apparatus and method of a finishing mill group 10 in which a plurality of finishing mills 11-17 are arranged in parallel, wherein the mapping of the first rolling mill 11 of the finishing mill group to a predetermined number is performed. Scale generation suppression apparatuses of hot rolling mills, each of which is provided with surface cooling devices 41, 42, and 43 connected to the control device 51 and cooling the upper and lower surfaces of the strip, on each inlet side of the rolling mill; And by using this, the first mapped rolling mill 11 by a 4000l / min.m ² or more cooling water between the spirit of the rolling mill up to a predetermined number from the inlet repeated cooling and finishing-rolling the strip in order to inhibit the production of hot-scale A method for suppressing scale generation of the finishing mill is the main point.

Description

Scale generation suppression apparatus and method of hot rolling mill

The present invention relates to an apparatus and method for suppressing scale generation of a hot rolling mill. More particularly, the present invention relates to a hot rolling mill for suppressing generation of scale on the surface of a strip in rolling a strip S using a finishing mill. A scale generation suppression apparatus and method are provided.

In the rolling process of the strip, when iron comes into contact with a gas such as oxygen or air at high temperatures, a film of the reactive product, i.e. scale, is formed on the surface thereof. This scale may have adverse effects such as surface defects on the strip and needs to be removed. Conventionally, as a method of removing the scale generated on the strip, high pressure water is sprayed on the strip surface.

8 is a schematic diagram of a descaling apparatus of a conventional hot rolling mill, in which a plurality of first to seventh rolling mills (11, 12, 13, 14, 15, and 17) are arranged in parallel in the conveying direction of a strip; Each finishing mill consists of a finishing mill group 10 provided with a pair of upper and lower work rolls (21, 22, 23, 24, 25, 26, 27, respectively). The scale breaker device 31 which removes the scale produced | generated on the strip is provided in the entrance side of this finishing mill group, and this apparatus is equipped with the injection nozzle 32 in the up-down direction of a strip, and this nozzle From the upper and lower surfaces of the strip, the scale can be removed by, for example, spraying high pressure water of 200 kgf / cm ² .

Therefore, when the slab is roughly rolled by the rough rolling machine and conveyed to the inlet side of the finishing mill group 10, the scale generated on the surface is first removed by the scale breaker device 31 before finishing rolling. In other words, for example, 200 kgf / cm ² of high pressure water is injected from the upper and lower injection nozzles 32 on the upper and lower surfaces of the conveyed strip to remove the scale. And the strip from which the scale was removed is conveyed to the finishing mill group, and is roll-processed by each work roll of the 1st-7th rolling mill, and is sequentially rolled to predetermined sheet thickness.

By the way, in the hot rolling mill, it is necessary to convey the strip at high speed in order to improve the processing efficiency, but if the strip is conveyed at high speed, the end roll hits the outer circumferential surface of the work roll when entering the finishing mill and the work roll is There was a problem of being deformed and damaged.

Therefore, the conventional hot rolling mill had no choice but to convey the strip at a low speed. As a result, the contact time between the strip and the work roll was increased, and the thickness of the scale exceeded the limit of 5 μm, and the scale was blown to the surface of the strip during finishing rolling. There was a problem that the quality is reduced, such as a defect occurs.

Therefore, in order to solve the problems of the prior art, the present invention provides surface cooling devices 41, 42, and 43 connected to the control device 51 above and below a predetermined finishing mill, and sequentially cools the surface of the strip. And it is an object of the present invention to provide a scale generation suppression apparatus and method for hot rolling mill that can improve the product quality by suppressing the scale thickness to 5㎛ or less by repeating the finishing rolling.

1 is a schematic diagram of a scale generation suppression apparatus of a hot rolling mill according to the present invention;

2 is a graph showing the relationship between the amount of cooling water and the scale thickness.

3 and 4 are graphs showing the relationship between strip temperature and scale thickness during rolling removal and hot rolling using the scale generation suppression apparatus according to the present invention according to rolling time.

5 is a graph showing the relationship between scale thickness and scale defects in general rolling;

6 and 7 are graphs showing the relationship between strip temperature and scale thickness during rolling in accordance with rolling time.

8 is a schematic diagram of a descaling device of a conventional hot rolling mill;

Explanation of symbols on the main parts of the drawings

10 ... Three rolling mills 11 ... 1st rolling mill

12 ... 2nd rolling mill 13 ... 3rd rolling mill

14 ... Fourth rolling mill 15 ... Fourth rolling mill

16 ... 6th rolling mill 17 ... 7th rolling mill

21 ... 1st Workroll 22 ... 2nd Workroll

23 ... 3rd Workroll 24 ... 4th Workroll

25 ... 5th Workroll 26 ... 6th Workroll

27 ... 7th Workroll 31 ... Scale Breaker Device

41 ... first surface cooling unit 42 ... second surface cooling unit

43 3rd surface cooling unit 44 1st injection nozzle

45 ... 2nd nozzle No. 46 ... 3rd injection nozzle

51 ... controller S ... rolled material (strip)

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

According to the present invention, in the finishing mill group 10 in which a plurality of finishing mills 11-17 for finishing rolling the strip S are arranged in parallel, the mapping from the first sand mill 11 of the finishing mill group to a predetermined number is performed. Surface cooling devices 41, 42, and 43 are respectively provided at the entrance side of the rolling mill to cool the upper and lower surfaces of the strips; A control device 51 is connected to each of these surface cooling devices, and the scale generation suppression device of a hot rolling mill is characterized in that it is connected.

In addition, the present invention provides a method for suppressing scale generation on the surface of a strip by using a scale generation suppression apparatus of a finishing mill group 10 in which a plurality of finishing mills 11-17 are paralleled. a rolling mill (11) between a rolling mill thought to a predetermined number from the inlet 4000l / min.m cooling the strip with at least ^two cooling water and spirit of the hot-rolled scale generated suppressed spirit mill, characterized in that the step of repeating in sequence It is about a method.

Hereinafter, the present invention will be described in detail with reference to the drawings.

First, Fig. 5 is a graph showing the relationship between scale thickness and scale defects in a third rolling mill of a general finishing mill, and all three test materials? Regardless of scale thickness, scale defects occur (i.e. scale rating 2.5 to 4.5) at 5 µm or more, whereas scale defects do not occur (ie scale rating 0) at 5 µm or less.

6 and 7 are graphs showing the relationship between strip temperature and scale thickness during rolling in accordance with rolling time. FIG. 6 is an evaluation of scale defects in the graph of FIG. In the EDGE part (○) and the center part (●), the scale thickness is 5 µm or less, whereas in FIG. 7, the evaluation of the scale defect is " there is a scale defect " (○) and the center portion (●) have a thickness of 5 µm or more.

From this fact, it can be seen that on the entry side of the third rolling mill, scale defects occur when the scale thickness is 5 µm or more, but when the scale thickness is suppressed to 5 µm or less, a rolled material without scale defects is obtained.

1 is a schematic view of a scale generation suppression apparatus of a hot rolling mill according to the present invention, in which a plurality of first to seventh rolling mills 11-17 are installed in parallel according to a conveying direction of a strip S, Each rolling mill is comprised from the finishing mill group 10 provided with the upper and lower pair of work rolls 21-27. The scale breaker device 31 which removes the scale produced | generated on the strip is provided in the entrance side of this finishing mill group. The scale brake device is provided with a pair of injection nozzles 32 in the vertical direction of the strip so that the scale is removed by spraying, for example, 180 kgf / cm ² of high pressure water from the injection nozzles to the upper and lower surfaces of the strip. .

In addition, a first surface cooling device 41 and a second surface cooling device cooling the upper and lower surfaces of the strip at the inlet sides of the first sand mill 11, the second sand mill 12, and the third sand mill 13, respectively. (42) and a third surface cooling device (43) are provided. Each of the surface cooling devices 41, 42, and 43 is provided with a pair of spray nozzles (44, 45, 46, respectively) in the vertical direction of the strip to cool the strip by injecting cooling water from the spray nozzles to the upper and lower surfaces of the strip. To lower the strip surface temperature.

A control device 51 is connected to each of the surface cooling devices 41, 42, and 43, and a predetermined amount of cooling water is injected into the strip from the respective injection nozzles 44, 45, and 46 according to the command of the control device. do. FIG. 2 is a graph showing the thickness of the scale with respect to the amount of cooling water, and it can be seen that it is preferable to set the cooling water amount to 4000 l / min.m ² or more in order to suppress the scale thickness to 5 μm or less.

Therefore, in the case of finishing rolling the strip by the hot rolling mill, the slab is roughly rolled in the rough mill, and then the conveyed strip is conveyed to the inlet side of the finishing mill group 10 before the rolling mill. Thereby removing the scale created on the surface. That is, the scale adhered is removed by, for example, spraying high pressure water of 180 kgf / cm ² from the injection nozzles 32 above and below the scale breaker apparatus with respect to the upper and lower surfaces of the conveyed strip.

The strip with the scale removed is conveyed to the finishing mill group, and each work roll 21 such as the first rolling mill 11, the second rolling mill 12, the third rolling mill 13, the fourth rolling mill 14, and the like. , 22, 23, 24, and the like, while being cooled by each surface cooling device 41, 42, 43, in turn, is mapped to a predetermined plate thickness.

That is, a command of the amount of cooling water is transmitted from the control device 51 to each of the surface cooling devices 41, 42, and 43 before the rolling process by the first rolling mill 11, and the first surface cooling device 41 is transmitted to the strip. Cooling water is injected from the injection nozzle 44 in the water in a quantity of 4000 l / min.m ² or more to cool the strip. The cooled strip is then rolled by the work roll 21 of the first sand mill, and then coolant is injected from the injection nozzle 45 of the second surface cooling apparatus 42 for the strip to cool the strip. Then, the cooled strip is rolled by the work roll 22 of the second rolling mill 12, and again coolant is sprayed from the injection nozzle 46 of the third surface cooling apparatus 43 with respect to the strip to form a strip. Is cooled. The cooled strip is then rolled by the work roll 23 of the third sand mill 13, and then the work roll 24 of the fourth sand mill 14 and the work roll 25 of the fifth sand mill 15. Rolled in order) and processed to a predetermined plate thickness.

FIG. 3 is a graph showing the relationship between strip temperature and scale thickness during rolling removal and hot rolling in accordance with the scale generation suppression apparatus of the present invention, according to rolling time, when the scale is removed by the scale breaker device 31. FIG. When the finishing rolling is performed by the first to seventh rolling mills 11-17, respectively, B, C, D, E, F, G, H, and the first to third surface cooling devices 41, 42, 43), X, Y, and Z are respectively cooled.

As can be seen from the above graph, the plate surface temperature of the strip drops to 420 ° C in A where the scale is removed by the scale brake device, so that the scale is almost removed, but the plate surface temperature is reduced to the original temperature by the internal sensible heat. Rise and scale is regenerated. However, in X cooled by the first surface cooling device 41, the surface temperature of the strip drops to 530 ° C, and the thickness of the scale is suppressed to 7-10 mu m. Afterwards, the inner surface of the strip is returned to its original temperature by sensible heat, but in B, which is rolled by the first sand mill 11, the plate surface temperature of the strip drops to 470 ° C, and the thickness of the scale decreases to 4-6 µm. . Then, in Y cooled by the second surface cooling device 42, the plate surface temperature of the strip drops to 630 ° C, and the thickness of the scale is suppressed to 6-8 mu m. The temperature then rises again, but at C, which is rolling in the second rolling mill 12, the plate surface temperature of the strip drops to 610 ° C, reducing the thickness of the scale to 3-4 m. In the Z cooled by the third surface cooling device 43, the plate surface temperature of the strip drops to 610 ° C., the scale thickness is suppressed to 3-5 μm, and then the scale thickness increases as the temperature increases, but 5 μm is increased. It doesn't work.

As described above, it can be seen that by repeating cooling and rolling, the scale thickness of the strip S can be finally suppressed to 5 µm or less to eliminate scale defects.

In the above description, the cooling conditions of each of the surface cooling devices 41, 42, and 43 are the cooling water amount of 4000 l / min.m ² and the cooling range of 1 m X plate width. C / sec) were compared. In other words, between the scale breaker device 31 and the first sand mill 11, it is 10.4 ° C / sec at the time of operation but 19.9 ° C / sec at the time of non-operation. Moreover, between 1st rolling mill 11 and the 2nd rolling mill 12, it is 19.3 degrees C / sec at the time of operation, and is 31.3 degrees C / sec at the time of non-operation. In addition, between the second sand mill 12 and the third sand mill 13, it is 13.9 degrees C / sec at the time of operation, but is 41.6 degrees C / sec at the time of non-operation. In addition, between the third sand mill 13 and the fourth sand mill 14, it is 24.5 degrees C / sec at the time of operation, and is 53.5 degrees C / sec at the time of non-operation. Therefore, it turns out that a cooling effect is large.

FIG. 4 is a graph showing the relationship between the rolling material temperature and the scale thickness during strip removal and hot rolling for the strip under different operating conditions, according to the rolling time, and is cooled by the third surface cooling device 43. As shown in FIG. Since the plate surface temperature of the strip drops to 820 DEG C in Z, and the thickness of the scale is suppressed to 5 mu m, the scale thickness also increases with the temperature rise thereafter, but does not become more than 5 mu m. Therefore, it can be seen that the scale thickness of the strip can be finally suppressed to 5 µm or less by repeating cooling and rolling by the first to third surface cooling devices 41, 42 and 43. FIG.

In addition, as shown in Fig. 5, by the scale generation suppression apparatus in accordance with the present invention, the scale thickness is improved from about 5 to about 5 μm and the scale defects are eliminated, so that the defects of the scale are eliminated. It turns out that this is suppressed appropriately.

On the other hand, in the above, it was mentioned that the first, second, and third surface cooling devices 41, 42, and 43 are installed only at the entrance sides of the first, second, and third slit mills 11, 12, and 13, respectively. The number of installations is not limited to this, and cooling is preferably performed until the plate surface temperature of the strip is lowered to 900 ° C. or lower, so that it may be provided after the fourth rolling mill 14 as necessary.

As described above, in the present invention, the control apparatus 51 is provided at each inlet side of the finishing mill 11 up to a predetermined number of the finishing mill 11 of the finishing mill group 10 in parallel with a plurality of finishing mills for finishing rolling the strip. ), Surface cooling devices (41, 42, 43) are connected to repeat the surface cooling and finishing rolling of the strip in sequence to finally maintain the surface temperature of the strip below 900 ℃ and to scale the thickness below 5㎛. It can be suppressed to improve product quality.

Claims (3)

In the finishing mill group 10 in which a plurality of finishing mills 11-17 for finishing rolling the strip S are arranged in parallel, Surface cooling devices (41, 42, 43) for cooling the upper and lower surfaces of the strip are respectively provided at the entrance of the finishing mill from the first rolling mill (11) of the finishing mill group to a predetermined number; A control device (51) is connected to each of said surface cooling devices. Scale generation suppression apparatus of hot rolling mill. In the method of suppressing scale generation on the surface of a strip by using a scale generation suppression apparatus of the finishing mill group 10 in which a plurality of finishing mills 11-17 are paralleled, Cooling the strip with the amount of cooling water of 4000l / min.m ² or more between the inlet of the first rolling mill (11) of the finishing mill group to a predetermined number, characterized in that to repeat the step of sequentially rolling Scale generation suppression method of hot rolling mill. The method of claim 2, And the surface temperature of the strip is maintained at 900 ° C. or lower to maintain the surface temperature of the strip.