JP6897609B2 - Hot rolling equipment and hot-rolled steel sheet manufacturing method - Google Patents

Description

The present invention relates to a hot rolling apparatus and a method for manufacturing a hot-rolled steel sheet.

In order to adjust the temperature quality of the steel sheet during rolling and the shape of the steel sheet, water or the like may be injected onto the steel sheet during hot rolling to cool it (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 8-309424

In the conventional cooling method, it is mainly important to make the temperature distribution of the steel sheet during rolling uniform, and the plate thickness deviation of the steel sheet is controlled by controlling the roll shape and the rolling mill.

Control by roll shape leads to high production cost because the rolls need to be prepared individually for each rolling material size, mechanical properties, and rolling schedule, and the rolls need to be replaced frequently.

Further, in the control by the rolling mill, it is necessary to introduce an apparatus for shape control (for example, a roll bender), and this method also causes a high production cost.

In the technique described in Patent Document 1, the shape of the steel sheet is adjusted by uniform cooling in the plate width direction, but the swelling (blistering) of the oxide film (scale) on the surface of the steel sheet that occurs during hot tandem rolling is caused. The resulting defects on the surface of the steel sheet cannot be improved.

The present invention is to solve the above problems, and an object of the present invention is to provide a technique for simultaneously improving surface defects caused by scale blistering and suppressing steel plate thickness deviation in a cooling device. It is in.

The present inventors have conducted extensive research in order to solve the above problems. As a result, it has been found that the above-mentioned problems can be solved by localizing the steel sheet cooling generally performed in hot rolling in the width direction as necessary and controlling the temperature. Specifically, the present invention provides the following.

[1] A rough rolling machine for rough rolling the conveyed steel sheet, a descaling device for descaling the steel sheet after rough rolling, and a finishing rolling machine equipped with a plurality of rolling rolls for rolling the descaled steel sheet. A cooling device having a plurality of cooling headers extending in the width direction of the steel sheet and having a plurality of cooling nozzles attached in the longitudinal direction of the steel sheet, and injecting cooling water from the cooling nozzles onto the upper surface of the steel sheet, and at least one cooling device. A hot rolling apparatus provided on a header and having a water amount adjusting unit for adjusting the amount of cooling water injected from a cooling nozzle of the cooling header.

[2] The output side plate thickness deviation measuring unit that measures the plate thickness deviation of the steel sheet on the outlet side of the finish rolling mill, and the output side temperature that measures the temperature distribution in the width direction of the steel plate on the outlet side of the finish rolling mill. The hot rolling apparatus according to [1], further comprising a distribution measuring unit.

[3] An entry-side plate thickness deviation measuring unit that measures the plate thickness deviation of the steel sheet on the entry side of the finish rolling mill, and an entry-side temperature that measures the temperature distribution in the width direction of the steel plate on the entry side of the finish rolling mill. The hot rolling apparatus according to [1] or [2], further comprising a distribution measuring unit.

[4] A first storage unit that stores the correlation between the temperature on the entry side of the finishing rolling mill, the residence time from immediately after descaling after rough rolling to cooling by the cooling water, and the presence or absence of blister defects. It has a residence time determination unit that determines the residence time at which blister defects do not occur based on the correlation stored in the first storage unit from the temperature distribution measured by the inlet temperature distribution measurement unit [3]. The hot rolling apparatus according to.

[5] A second storage unit that stores the correlation between the temperature during rolling, the rolling reduction rate, and the amount of change in plate thickness during rolling, and the temperature distribution measured by the inlet temperature distribution measuring unit. It has a cooling water amount determining unit that determines the cooling water amount based on the plate thickness deviation measured by the entry side plate thickness deviation measuring unit and the correlation stored in the second storage unit [3] or [ 4] The hot rolling apparatus according to.

[6] Based on the plate thickness deviation and temperature distribution of the steel sheet surface before finish rolling, the desired plate thickness deviation after hot rolling, the temperature on the entry side of the finish rolling mill, and the temperature after rough rolling. The amount of cooling water injected is changed according to the position of the steel sheet in the width direction so that blister defects do not occur based on the correlation between the residence time from immediately after descaling to cooling by cooling water and the presence or absence of blister defects. A method for manufacturing a hot-rolled steel sheet that is rolled while cooling the steel sheet.

[7] A method for manufacturing a hot-rolled steel sheet in which a descaled steel sheet is finish-rolled after rough rolling, and the first measurement for measuring the plate thickness deviation and the temperature distribution in the plate width direction on the entry side of hot rolling. It has a step and a first hot rolling step of hot rolling while cooling the steel sheet after the first measurement step, and the cooling in the first hot rolling step is performed by cooling water on the upper surface of the steel sheet. Is cooling to cool the steel sheet by injecting, and at the time of the cooling, in the width direction of the steel sheet so as to obtain a desired plate thickness deviation after hot rolling based on the measurement result obtained in the first measurement step. The amount of cooling water injected is changed according to the position of to cool the steel sheet, and the cooling is the temperature distribution on the entry side of the finishing rolling mill and the retention from immediately after descaling after rough rolling to cooling by the cooling water. A method for producing a hot-rolled steel sheet, which is cooling performed at the residence time in which blister defects do not occur, based on the correlation between time and the presence or absence of blister defects, based on the temperature distribution obtained in the first measurement step.

[8] Based on the measurement results of the second measurement step of measuring the plate thickness deviation of the steel sheet and the temperature distribution in the plate width direction on the output side of the hot rolling after the first hot rolling step, and the measurement results of the second measurement step. The method for producing a hot-rolled steel sheet according to [7], further comprising a second hot-rolling step of changing the conditions of the amount of cooling water to perform hot-rolling.

Based on the plate thickness deviation of the steel sheet on the entry side of the rolling mill and the temperature distribution in the plate width direction, the position of the steel plate in the plate width direction is set so that the plate thickness deviation is within the desired range and blister defects do not occur. Since the amount of cooling water injected is changed accordingly to cool the steel sheet, the plate thickness deviation of the steel sheet is adjusted to the desired range while suppressing the occurrence of steel sheet surface defects (blister defects) caused by scale blistering. It is possible to suppress the occurrence of defective products due to fluctuations in plate thickness.

It is a figure which shows typically the hot rolling apparatus of this embodiment. It is a schematic diagram for demonstrating the cooling apparatus and the water amount adjustment part of the hot rolling apparatus of this embodiment. It is a figure which shows an example of the correlation between the residence time from immediately after descaling after rough rolling to cooling by cooling water, and the presence or absence of the occurrence of a blister defect. It is a figure for demonstrating the effect of this invention.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

FIG. 1 is a diagram schematically showing a hot rolling apparatus of this embodiment. FIG. 2 is a schematic view for explaining a cooling device and a water amount adjusting unit of the hot rolling apparatus of the present embodiment.

The hot rolling apparatus 1 of the present embodiment includes a rough rolling mill 10, a descaling apparatus 11, a finishing rolling mill 12, a cooling device 13, a water amount adjusting unit 14, an input side plate thickness deviation measuring unit 15, and an input side plate thickness deviation measuring unit 15. Side temperature distribution measurement unit 16, exit side plate thickness deviation measurement unit 2, outlet side temperature distribution measurement unit 3, first storage unit 4, residence time determination unit 5, second storage unit 6, and cooling water amount determination It has a part 7.

The rough rolling mill 10 is a rolling mill that roughly rolls a steel plate M conveyed in the direction of the white arrow, and the number of rolling rolls is not particularly limited. In addition, in FIG. 1, only the output side roll of the rough rolling mill 10 is shown.

The descaling device 11 removes the scale formed on the surface of the steel sheet rolled by the rough rolling mill 10 with, for example, high-pressure water. The descaling device 11 is a device for removing scale on the surface of the steel sheet immediately after rough rolling, and the distance between the output roll of the rough rolling machine 10 and the descaling device 11 is usually 50 to 200 m.

The finish rolling mill 12 has a plurality of rolling rolls 121A to 121G for rolling the steel plate M. The rolling rolls 121E to 121G have intermediate rolls, and it can be appropriately determined whether the rolling rolls having the intermediate rolls are used or, if used, which rolling rolls are provided with the intermediate rolls. The distance between the finishing rolling mill 12 and the descaling device 11 is usually 2 to 20 m.

As shown in FIGS. 1 and 2, the cooling device 13 includes cooling headers 131A to 131H extending in the width direction of the steel plate on the upper surface side of the steel plate M, and cooling headers 131a to 131h extending in the width direction of the steel plate on the lower surface side of the steel plate. Each of the cooling headers has six cooling nozzles 132A to 132F provided in the plate width direction (steel plate width direction). In FIG. 2, the cooling header and the like on the lower surface side are omitted. The number of cooling nozzles may differ depending on the cooling header, and may be the same for all or partially the same.

A cooling header may be provided on either the upper surface side or the lower surface side, and the cooling header may not be provided on both the upper surface side and the lower surface side, but as in the present embodiment, both the upper surface side and the lower surface side may be provided. It is preferable that a cooling header is provided for cooling.

As shown in FIG. 1, the cooling headers 131A to 131H and the cooling headers 131a to 131h are provided in front of the rolling rolls 121A on the entry side, between the rolling rolls 121A to 121G, and immediately after the rolling rolls 121G on the exit side. Since a plurality of cooling headers may be provided in the longitudinal direction of the steel sheet, the number of cooling headers is not particularly limited, but cooling headers are provided between the rolls as in the present embodiment so that the cooling conditions can be finely adjusted. It is preferable to do so.

The number of cooling nozzles is not particularly limited, but is preferably 3 or more, and more preferably 6 or more. The larger the number of cooling nozzles, the finer the adjustment can be made. However, if the number of cooling nozzles is too large, not only the adjustment becomes complicated but also the effect is saturated, so 15 or less is preferable.

In the present embodiment, the two cooling nozzles 132C and 132D at the center in the plate width direction are provided at positions facing each other near the center in the plate width direction of the steel plate, and the cooling nozzles 132A and 132F at both ends in the plate width direction are formed on the steel plate. It is provided at positions facing both ends in the plate width direction. Further, as in the present embodiment, it is preferable that all the cooling headers 131A to 131h are provided with cooling nozzles at positions facing the center of the steel plate in the plate width direction and at positions facing both ends of the steel plate in the plate width direction.

In the present embodiment, the water amount adjusting unit 14 is provided in each cooling header and is composed of valves 141A to 141F attached to each of the cooling nozzles 132A to 132F. The water amount adjusting unit (valve in this embodiment) does not have to be provided in all the cooling nozzles, and may be provided in some cooling nozzles.

The entry side plate thickness deviation measuring unit 15 measures the plate thickness deviation of the steel plate on the entry side of the finishing rolling mill 12. Any device that can measure the thickness profile in the width direction of the steel plate may be used. For example, a commercially available surface shape measuring device may be used. The measurement result is obtained as the distribution of the plate thickness deviation on the surface of the steel plate. The location of the entry-side plate thickness deviation measuring unit 15 may be between the rough rolling mill 10 and the finishing rolling mill 12. The plate thickness deviation before finish rolling may be evaluated by an experiment, a simulation, or the like. In that case, the input side plate thickness deviation measuring unit 15 may be omitted.

The inlet temperature distribution measuring unit 16 measures the temperature distribution on the surface of the steel sheet on the inlet side of the finishing rolling mill 12. The temperature distribution measurement may be performed using, for example, a scanning radiation thermometer. The inlet temperature distribution measuring unit 16 measures the temperature distribution on the surface of the steel sheet after being descaled by the descaling device 11. In the present embodiment, the entry-side temperature distribution measuring unit 16 measures the temperature immediately before the finish rolling, but the installation location of the entry-side temperature distribution measuring unit 16 is not limited as long as the temperature immediately before the finish rolling can be evaluated. In particular, considering the time required for the surface of the steel sheet to reheat, it may be difficult to evaluate the temperature immediately before finish rolling after descaling. In this case, the temperature is measured before descaling and finish rolling. It is preferable to evaluate (predict) the temperature immediately before. If the temperature distribution on the surface of the steel sheet before finish rolling can be evaluated by an experiment, simulation, or the like, the inlet temperature distribution measuring unit 16 may be omitted.

The measurement point where the inlet temperature distribution measuring unit 16 measures the temperature distribution is between the descaling device 11 and the finishing rolling mill 12. When the cooling water is injected from the cooling nozzle of the cooling device 13 in front of the rolling roll on the entry side of the finishing rolling mill 12 as in the present embodiment, the temperature is measured before that. Since the temperature drop between the descaling device 11 and the finishing rolling mill 12 is small after the scale is removed by the descaling device 11, the same result can be obtained by measuring the temperature distribution between the descaling device 11 and the finishing rolling mill 12. Be done.

The output side plate thickness deviation measuring unit 2 measures the plate thickness deviation of the steel plate on the output side of the finishing rolling mill 12. For example, a commercially available surface shape measuring device may be used in the same manner as the entry side plate thickness deviation measuring unit 15. In the present invention, the output side plate thickness deviation measuring unit 2 may not be provided.

The output side temperature distribution measuring unit 3 measures the temperature distribution on the surface of the steel sheet on the output side of the finishing rolling mill 12. The temperature distribution measurement may be performed using, for example, a scanning radiation thermometer. In the present invention, the exit side temperature distribution measuring unit 3 may not be provided.

The first storage unit 4 stores the correlation between the temperature on the entry side of the finishing rolling mill 12, the residence time immediately after descaling after rough rolling until cooling with cooling water, and the presence or absence of blister defects. ing. The first storage unit 4 is, for example, a storage medium such as a hard disk.

FIG. 3 shows an example of the correlation between the temperature on the entry side of the finish rolling mill 12, the residence time from immediately after descaling after rough rolling to cooling by the cooling water, and the presence or absence of blister defects. The vertical axis of FIG. 3 is the inlet temperature (° C.) of the finishing rolling mill 12, and the horizontal axis is the residence time (s) from descaling by the descaling device 11 to cooling by cooling water. The above correlation may be obtained experimentally, or may be predicted by performing simulation or the like.

The residence time determination unit 5 is connected to the entry side temperature distribution measurement unit 16 and can receive the measurement result of the temperature distribution measured by the entry side temperature distribution measurement unit 16. Further, the residence time determination unit 5 is connected to the first storage unit 4. By connecting these, the residence time determination unit 5 specifies the residence time condition at which blister defects do not occur for each position on the surface of the steel sheet in consideration of the transfer speed based on the temperature distribution and the correlation. .. As shown in FIG. 3, since the conditions corresponding to the region where the blister defect does not occur are specified, the range of the conditions that can be adopted is specified here. The residence time determination unit 5 is, for example, a computer or the like.

Further, in the present embodiment, the residence time determination unit 5 is also connected to the outlet side plate thickness deviation measurement unit 2 and the outlet side temperature distribution measurement unit 3, and the plate thickness deviation and output measured by the outlet side plate thickness deviation measurement unit 2. The temperature distribution measured by the side temperature distribution measuring unit 3 can be received.

Further, in the present invention, the first storage unit 4 and the residence time determination unit 5 may not be provided.

The second storage unit 6 stores the correlation between the temperature during rolling, the rolling reduction rate during rolling, and the amount of change in plate thickness during rolling. The above correlation may be obtained experimentally, or may be predicted by performing simulation or the like. The second storage unit 6 is a storage medium such as a hard disk.

The cooling water amount determination unit 7 is connected to the inlet side plate thickness deviation measuring unit 15 and the inlet temperature distribution measuring unit 16 and can receive the measurement results of the temperature distribution and the plate thickness deviation. Further, the cooling water amount determination unit 7 is connected to the second storage unit 6. By connecting these, the cooling water amount determining unit 7 determines the cooling water amount in consideration of the transport speed based on the measurement result of the plate thickness deviation and the temperature distribution and the above correlation. The cooling water amount determination unit 7 is, for example, a computer or the like.

In the present embodiment, the cooling water amount determination unit 7 is also connected to the residence time determination unit 5, and the cooling under the conditions determined by the cooling water amount determination unit 7 also satisfies the residence time condition determined by the residence time determination unit 5. To judge. As described above, the residence time determination unit 5 specifies a range of cooling conditions that can be adopted, and those satisfying the range may be selected. However, if none of them are satisfied, it is necessary to determine the conditions to be satisfied, for example, by changing the transport speed.

Further, in the present embodiment, the cooling water amount determining unit 7 is connected to the valves 141A to 141F and controls the amount of cooling water injected from the valves 141A to 141F.

Further, in the present embodiment, the cooling water amount determination unit 7 is also connected to the outlet side plate thickness deviation measuring unit 2 and the outlet side temperature distribution measuring unit 3, and the plate thickness deviation and output measured by the outlet side plate thickness deviation measuring unit 2. The temperature distribution measured by the side temperature distribution measuring unit 3 can be received.

The present invention does not have to have the second storage unit 6 and the cooling water amount determination unit 7.

Next, the operation of the hot rolling apparatus shown in FIGS. 1 and 2 will be described.

The steel plate M is rolled by the rough rolling mill 10. The thickness of the rough-rolled steel sheet M is not particularly limited, but the thickness preferably used in the present invention is 20 to 50 mm.

The steel sheet M rolled by the rough rolling mill 10 is descaled by the descaling device 11. As a result, the scale on the surface of the steel sheet M is removed.

The plate thickness deviation and temperature distribution on the surface of the steel plate M from which the scale has been removed are measured by the entry-side plate thickness deviation measuring unit 15 and the entrance-side temperature distribution measuring unit 16. This measurement corresponds to the first measurement step. The measurement result of the temperature distribution is sent to the residence time determination unit 5 and the cooling water amount determination unit 7. Further, the measurement result of the plate thickness deviation is sent to the cooling water amount determination unit 7.

Based on the correlation stored in the first storage unit 4, the residence time determination unit 5 specifies the residence time condition in which blister defects do not occur for each temperature in the temperature distribution in consideration of the transport speed. From this residence time condition and the transport speed, which cooling header cooling nozzle should inject cooling water at the latest is determined.

In the cooling water amount determination unit 7, based on the correlation stored in the second storage unit 6, the temperature at the time of rolling for achieving the target plate thickness at each position on the steel plate surface is obtained from the measurement results of the plate thickness deviation and the temperature distribution. And determine the amount of cooling water for that purpose (determine the amount of cooling water at each cooling nozzle so that the temperature is specified during rolling). More specifically, the temperature of the cooling water is confirmed with a thermometer or the like, and the amount of cooling water in each cooling nozzle of each cooling header is determined.

Further, the cooling water amount determination unit 7 compares the determined cooling water amount condition with the residence time condition determined by the residence time determination unit 5, and when the cooling water amount condition is adopted, the residence time It is confirmed whether the condition of the residence time determined by the determination unit 5 is satisfied. If it is not satisfied, find a condition that satisfies it, such as by increasing the transport speed.

The residence time determination unit 5 and the cooling water amount determination unit 7 determine from which cooling nozzle the amount of cooling water should be injected, and the finish rolling machine 12 performs finish rolling under that condition. The determination of the above conditions and the above rolling correspond to the first hot rolling step.

The surface plate thickness deviation and temperature distribution of the finish-rolled steel sheet M are measured by the output side plate thickness deviation measuring unit 2 and the exit side temperature distribution measuring unit 3. The measurement results of the plate thickness deviation and the temperature distribution are sent to the residence time determination unit 5 and the cooling water amount determination unit 7. The measurement of the plate thickness deviation and the temperature distribution here corresponds to the second measurement step.

If the plate thickness deviation is different from the one predicted by the cooling conditions using the correlation stored in the first storage unit and the correlation stored in the second storage unit, the plate thickness deviation is different from the predicted plate thickness deviation. In consideration of the difference from the plate thickness deviation measured by the output side plate thickness deviation measuring unit 2 and the difference between the predicted temperature distribution and the temperature distribution measured by the exit side temperature distribution measuring unit 3, the residence time determination unit 5 is the third. The correlation stored in the 1 storage unit is corrected, and the cooling water amount determination unit 7 corrects the correlation stored in the second storage unit.

Cooling conditions are determined using the above-corrected correlation, and hot-rolled steel sheets are manufactured. Rolling using this corrected correlation corresponds to the second hot rolling step.

If the plate thickness deviation determined by the heating conditions and rough rolling conditions of the steel sheet before finish rolling becomes a problem, the plate thickness deviation can be derived experimentally or by simulation. Even if the measurement by the inlet side plate thickness deviation measuring unit 15 and the inlet side temperature distribution measuring unit 16 or the measurement by the outlet side plate thickness deviation measuring unit 2 and the outlet side temperature distribution measuring unit 3 is not performed, the above-derived plate thickness deviation and temperature are obtained. Based on the predicted value of the distribution, it is good to roll the steel sheet while cooling it by changing the amount of cooling water injected according to the position in the width direction of the steel sheet so that the desired sheet thickness deviation is obtained after hot rolling. A hot-rolled steel sheet can be obtained. Therefore, when the plate thickness deviation before finish rolling can be evaluated in advance in this way, a good hot-rolled steel sheet can be produced without measuring the plate thickness deviation and the temperature distribution at the time of production. Further, even in the above case where the plate thickness deviation can be evaluated in advance, the plate thickness deviation measuring unit and the outlet side temperature distribution measuring unit are provided on the exit side, and the plate thickness predicted to be the actually generated plate thickness deviation. It is preferable that the manufacturing conditions can be corrected according to the difference from the deviation. The hot rolling apparatus used in the above case in which the plate thickness deviation can be evaluated in advance includes an inlet side plate thickness deviation measuring unit, an inlet temperature distribution measuring unit, an outgoing side plate thickness deviation measuring unit, and an outgoing side temperature distribution measuring unit. You don't have to have it.

Next, the effect of the present invention will be described using the hot rolling apparatus 1 of the present embodiment.

In hot rolling, it is required to improve the flat shape of the steel sheet such as ear wave and medium elongation, and to set the plate thickness deviation within a desired range. Further, even if the scale is removed by descaling after rough rolling, the scale is generated again, so that a defect (blister defect) in which the scale swells may occur, and it is required to suppress this. Conventionally, in the production of hot-rolled steel sheets, a method of uniformly cooling the steel sheet has been preferable, but simply performing uniform cooling causes the plate thickness deviation to be within a desired range and causes the problem of blister defects. It cannot be resolved.

Since the hot rolling apparatus 1 of the present embodiment has valves 141A to 141F, as shown in FIG. 4B, each of the steel sheet surfaces is based on the plate thickness deviation and the temperature distribution of the steel sheet surface before finish rolling. Since the amount of cooling water can be changed according to the plate thickness at the position and the temperature at each position, the cooling conditions can be set so that the thickness at each position on the steel sheet surface becomes uniform. Then, considering the correlation as shown in FIG. 3, the residence time from descaling to cooling by the cooling water can be set for each position on the surface of the steel sheet, and blister defects can be suppressed.

Since the hot rolling apparatus 1 of the present embodiment has the input side plate thickness deviation measuring unit 15, the plate thickness deviation of the steel plate before finish rolling can be measured. This plate thickness deviation is the distribution of the plate thickness deviation, and by this measurement, the plate thickness can be specified for each position on the surface of the steel sheet. Further, since the hot rolling apparatus 1 of the present embodiment has the inlet side temperature distribution measuring unit 16, the temperature distribution of the steel sheet before finish rolling can be measured. By this measurement, the temperature can be specified for each position on the surface of the steel sheet.

The steel sheet after rough rolling has a plate thickness deviation even if it looks flat at first glance. When there is a plate thickness deviation, as shown in FIG. 4A, when the film is cooled uniformly, the plate thickness deviation remains even after finish rolling. However, in the present invention, since the valves 141A to 141F are provided, as shown in FIG. 4B, the thickness of each position of the steel plate surface is increased according to the plate thickness at each position of the steel plate surface and the temperature at each position. Cooling conditions can be set so that

Further, in the hot rolling apparatus 1 of the present embodiment, the timing of cooling at each position on the surface of the steel sheet can be individually set by the valves 141A to 141F. Therefore, considering the correlation as shown in FIG. 3, descaling The residence time from the later to cooling by the cooling water can be set for each position on the surface of the steel sheet, and blister defects can be suppressed.

As described above, the hot rolling apparatus 1 having the entry-side plate thickness deviation measuring unit 15 and the entry-side temperature distribution measuring unit 16 can cope with a plate thickness deviation that is difficult to predict.

In the hot rolling apparatus 1 of the present embodiment, since the cooling header is provided between each roll of the finish rolling mill 12, the cooling conditions can be finely adjusted at each position on the surface of the steel sheet, and the plate thickness deviation can be adjusted. It's easy to do.

Further, the hot rolling apparatus 1 of the present embodiment includes cooling headers 131A to 131H extending in the width direction of the steel sheet on the upper surface side of the steel sheet M, and cooling headers 131a to 131h extending in the width direction of the steel sheet on the lower surface side of the steel sheet. Therefore, cooling water can be sprayed from the cooling nozzles on both the upper surface and the lower surface of the steel sheet. As a result, the cooling conditions at each position on the steel sheet surface can be adjusted more accurately from both the upper surface side and the lower surface side, and as a result, the plate thickness deviation tends to be within a desired range.

Further, the hot rolling apparatus 1 of the present embodiment has a cooling header 131A and a cooling header 131a for injecting cooling water in front of the rolling roll on the entry side of the finishing rolling mill 12. As shown in FIG. 3, shortening the residence time is effective in suppressing blister defects, and cooling water can be injected from the front of the rolling roll on the entry side of the finishing rolling mill 12, so that earlier timing cooling can be started and transportation is performed. It is easy to eliminate blister defects by the residence time without changing the speed.

In the hot rolling apparatus 1 of the present embodiment, the two cooling nozzles 132C and 132D at the center in the plate width direction are provided at positions facing each other near the center in the plate width direction of the steel sheet, and the cooling nozzles 132A at both ends in the plate width direction. , 132F are provided at positions facing both ends of the steel plate in the plate width direction. In particular, since plate thickness deviations are likely to occur between the center and the edges in the plate width direction, according to the hot rolling apparatus 1 of the present embodiment capable of directly injecting cooling water into these, the plate thickness deviation is particularly set within a desired range. Easy to adjust.

The hot rolling apparatus 1 of the present embodiment can adjust the amount of cooling water in all the cooling nozzles. The hot rolling apparatus 1 of the present embodiment, which can adjust the amount of cooling water with a cooling nozzle of 90% or more, can finely adjust the cooling conditions.

The hot rolling apparatus 1 of the present embodiment has a first storage unit 4 and a residence time determination unit 5. As shown in FIG. 3, the correlation between the temperature on the entry side of the finishing rolling mill, the residence time from immediately after descaling after rough rolling to cooling by the cooling water, and the presence or absence of blister defects is the first. If there is this correlation and the temperature distribution measured by the inlet temperature distribution measuring unit 16 stored in the storage unit 4, the residence time at which blister defects do not occur can be specified for each position on the steel sheet surface. When the residence time determination unit 5 performs this identification, the appropriate residence time can be grasped more quickly and more accurately. In particular, if a normal computer (electronic computer) is used as the residence time determination unit 5, an appropriate residence time can be instantly specified.

Further, the hot rolling apparatus 1 of the present embodiment has a second storage unit 6 and a cooling water amount determining unit 7. The correlation between the temperature during rolling, the rolling reduction rate, and the amount of change in plate thickness during rolling is stored in the second storage unit 6, and the plate thickness deviation measured by the input side plate thickness deviation measuring unit 15 and the desired plate thickness deviation are desired. The required amount of change in plate thickness can be specified from the difference from the plate thickness, and the temperature before rolling at each position on the steel plate surface can be specified from the measurement results of the inlet temperature distribution measuring unit 16, so it is appropriate from these and the correlation. Cooling conditions can be specified. Specifically, the amount of cooling water for each nozzle may be adjusted so that a desired plate thickness variation occurs during each rolling. When the cooling water amount determining unit 7 determines the cooling water amount at each nozzle, the cooling water amount at each nozzle can be determined more quickly and more accurately. In particular, if a normal computer (electronic computer) is used as the cooling water amount determining unit 7, the appropriate cooling water amount can be instantly specified.

In particular, in the hot rolling apparatus 1 of the present embodiment, the residence time determined by the residence time determination unit 5 is sent to the cooling water amount determination unit 7. In the hot rolling apparatus 1 of the present embodiment, the cooling water amount determination unit 7 can determine the condition of the cooling water amount of each nozzle within the residence time in which blister defects do not occur, so that the plate thickness deviation can be suppressed. It is particularly effective in preventing the occurrence of blister defects.

Further, the hot rolling apparatus 1 of the present embodiment has an output side plate thickness deviation measuring unit 2 and an exit side temperature distribution measuring unit 3. When the intended result is not obtained, the correlation stored in the first storage unit 4 and the correlation stored in the second storage unit 6 are corrected based on the difference between the prediction and the actual measurement. Further, a hot-rolled steel sheet having a small variation in plate thickness and no blister defect can be obtained.

The hot rolling apparatus having the inlet side plate thickness deviation measuring unit 15 and the inlet side temperature distribution measuring unit 16 further has the outlet side plate thickness deviation measuring unit 2 and the outlet side temperature distribution measuring unit 3 so that blister defects are not generated. , It becomes easier to adjust to the desired plate thickness deviation.

The effects of the present invention are as described above. The correlation stored in the first storage unit 4 and the correlation stored in the second storage unit 6 differ depending on the component composition, but even if the correlation is different, the present invention can be used in the same manner. The effect of is obtained.

As an example of the invention, a hot-rolled steel sheet was manufactured using the hot rolling apparatus shown in FIGS. 1 and 2. As a comparative example, a hot-rolled steel sheet was manufactured so as to have uniform cooling. When the results of the invention example and the results of the comparative example were compared, the plate thickness variation of the invention example was smaller than that of the comparative example. Further, although no blister defect was observed in the invention example, a blister defect was confirmed in the comparative example.

1 Hot rolling machine 10 Rough rolling machine 11 Descaling machine 12 Finishing rolling machine 13 Cooling device 14 Water volume adjustment part 15 Input side plate thickness deviation measurement unit 16 Input side temperature distribution measurement unit 2 Outside plate thickness deviation measurement unit 3 Outside temperature distribution Measuring unit 4 1st storage unit 5 Resident time determination unit 6 2nd storage unit 7 Cooling water amount determination unit

Claims (5)

A rough rolling machine that roughly rolls the transferred steel sheet,
A descaling device that descales steel sheets after rough rolling,
A finishing rolling mill equipped with multiple rolling rolls for rolling descaled steel sheets,
A cooling device having a plurality of cooling headers extending in the width direction of the steel sheet and having a plurality of cooling nozzles attached in the longitudinal direction of the steel sheet, and injecting cooling water from the cooling nozzles onto the upper surface of the steel sheet.
A water amount adjusting unit provided on at least one cooling header and adjusting the amount of cooling water injected from the cooling nozzle of the cooling header.
An entry-side plate thickness deviation measuring unit that measures the plate thickness deviation of the steel plate on the entry side of the finishing rolling mill,
An inlet temperature distribution measuring unit that measures the temperature distribution in the width direction of the steel sheet on the inlet side of the finishing rolling mill.
A second storage unit that stores the correlation between the temperature during rolling, the rolling reduction rate, and the amount of change in plate thickness during rolling.
The amount of cooling water is determined based on the temperature distribution measured by the inlet temperature distribution measuring unit, the plate thickness deviation measured by the inlet plate thickness deviation measuring unit, and the correlation stored in the second storage unit. A hot rolling apparatus having a cooling water amount determination unit and a cooling water amount determination unit. A rough rolling machine that roughly rolls the transferred steel sheet,
A descaling device that descales steel sheets after rough rolling,
A finishing rolling mill equipped with multiple rolling rolls for rolling descaled steel sheets,
A cooling device having a plurality of cooling headers extending in the width direction of the steel sheet and having a plurality of cooling nozzles attached in the longitudinal direction of the steel sheet, and injecting cooling water from the cooling nozzles onto the upper surface of the steel sheet.
A water amount adjusting unit provided on at least one cooling header and adjusting the amount of cooling water injected from the cooling nozzle of the cooling header.
The output side plate thickness deviation measuring unit that measures the plate thickness deviation of the steel plate on the output side of the finishing rolling mill,
A temperature distribution measuring unit on the output side that measures the temperature distribution in the width direction of the steel sheet on the output side of the finishing rolling mill.
An entry-side plate thickness deviation measuring unit that measures the plate thickness deviation of the steel plate on the entry side of the finishing rolling mill,
An inlet temperature distribution measuring unit that measures the temperature distribution in the width direction of the steel sheet on the inlet side of the finishing rolling mill.
A second storage unit that stores the correlation between the temperature during rolling, the rolling reduction rate, and the amount of change in plate thickness during rolling.
The amount of cooling water is determined based on the temperature distribution measured by the inlet temperature distribution measuring unit, the plate thickness deviation measured by the inlet plate thickness deviation measuring unit, and the correlation stored in the second storage unit. A hot rolling apparatus having a cooling water amount determination unit and a cooling water amount determination unit. A first storage unit that stores the correlation between the temperature on the entry side of the finishing rolling mill, the residence time from immediately after descaling after rough rolling to cooling by the cooling water, and the presence or absence of blister defects.
Claim 1 or claim 1 having a residence time determination unit that determines a residence time at which blister defects do not occur based on the correlation stored in the first storage unit from the temperature distribution measured by the inlet temperature distribution measurement unit. 2. The hot rolling apparatus according to 2. Based on the plate thickness deviation and temperature distribution of the steel sheet surface before finish rolling, the desired plate thickness deviation after hot rolling, the temperature on the entry side of the finish rolling mill, and immediately after descaling after rough rolling. The amount of cooling water injected is changed according to the position in the width direction of the steel sheet so that blister defects do not occur based on the correlation between the residence time from to cooling by the cooling water and the presence or absence of blister defects. A method for manufacturing a hot-rolled steel sheet that is rolled while cooling. A method for manufacturing a hot-rolled steel sheet in which a descaled steel sheet is finish-rolled after rough rolling.
The first measurement step of measuring the plate thickness deviation of the steel plate and the temperature distribution in the plate width direction on the entry side of hot rolling, and
After the first measurement step, a first hot rolling step of hot rolling while cooling the steel sheet and a step of hot rolling.
After the first hot rolling step, a second measuring step of measuring the plate thickness deviation of the steel sheet and the temperature distribution in the plate width direction on the output side of the hot rolling,
Based on the measurement result of the second measurement step, it has a second hot rolling step of performing hot rolling by changing the condition of the amount of cooling water injected according to the position in the width direction of the steel sheet.
The cooling in the first hot rolling step is cooling by injecting cooling water onto the upper surface of the steel sheet to cool the steel sheet, and based on the measurement results obtained in the first measurement step during the cooling. The steel sheet is cooled by changing the amount of cooling water injected according to the position in the width direction of the steel sheet so that the desired sheet thickness deviation is obtained after hot rolling.
The cooling is first measured based on the correlation between the temperature distribution on the entrance side of the finishing rolling mill, the residence time from immediately after descaling after rough rolling to cooling by the cooling water, and the presence or absence of blister defects. A method for producing a hot-rolled steel sheet, which is cooling performed at the residence time without causing blister defects from the temperature distribution obtained in the process.

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