TWI477328B - Apparatus for cooling hot rolled steel sheet - Google Patents

Description

Hot rolled steel plate cooling device Field of invention

The present invention relates to a hot-rolled steel sheet cooling apparatus for cooling a hot-rolled steel sheet hot-rolled by a finishing mill.

Background of the invention

For example, a hot-rolled steel sheet used for automobiles, industrial machines, and the like is generally produced by a rough rolling step and a finishing rolling step. Fig. 18 is a view schematically showing a method of manufacturing a conventional hot-rolled steel sheet. In the manufacturing step of the hot-rolled steel sheet, first, the flat nail S obtained by continuously casting the molten steel adjusted to a predetermined composition is rolled by the rough rolling mill 201, and then the fine rolling table 202a to 202d is used. The rolling mill 203 is hot rolled to form a hot rolled steel sheet H having a predetermined thickness. Then, the hot-rolled steel sheet H is cooled by the cooling water injected from the cooling device 211, and then wound into a coil shape by the winding device 212.

The cooling device 211 is used to apply a so-called thin-layer cooling device to the hot-rolled steel sheet H that is generally conveyed from the finishing mill 203. The cooling device 211 sprays the cooling water as the jet water through the cooling nozzle from the vertical direction above the hot-rolled steel sheet H that is moved on the output stage, and for the hot-rolled steel sheet H Next, the cooling water is sprayed as the jet water through the tubular thin layer, thereby cooling the hot rolled steel sheet H.

Further, for example, Patent Document 1 discloses a technique for reducing the surface temperature difference between the upper and lower surfaces of a thick steel plate, thereby preventing the shape of the steel sheet from being defective. According to the technique disclosed in Patent Document 1, when the cooling device is cooled, the water temperature ratio of the cooling water supplied to the upper surface and the lower surface of the steel sheet is adjusted based on the surface temperature difference obtained by simultaneously measuring the surface temperature of the upper surface and the lower surface of the steel sheet with a thermometer. .

Further, for example, Patent Document 2 discloses a technique in which the sprayed spray is used to cool the rolled material between two rolling stands adjacent to the finishing mill, thereby starting and ending the γ-α transformation of the rolled material to prevent rolling. The board between the stations deteriorated.

Further, for example, Patent Document 3 discloses a technique of measuring the sharpness of the front end of the steel sheet by using a sharpness meter provided on the exit side of the rolling mill, and changing the flow rate of the cooling water in the width direction according to the severity of the measurement. Adjust to prevent the opening of the steel plate.

Further, for example, Patent Document 4 discloses a technique for eliminating the thickness distribution of the plate in the width direction of the hot-rolled steel sheet, uniformizing the thickness in the sheet width direction, and controlling the width direction of the hot-rolled steel sheet. The difference between the highest thermal conductivity and the lowest thermal conductivity may be within a predetermined range of values.

Here, the hot-rolled steel sheet H produced by the manufacturing method shown in FIG. 18 is, for example, as shown in FIG. 19, on the transport roller 220 of the output stage of the cooling device 211 (hereinafter referred to as "ROT"). Calendering direction (Figure 19 Arrow direction) The case where a waveform is generated. At this time, unevenness in cooling of the upper surface and the lower surface of the hot-rolled steel sheet H may occur. In other words, the cooling variation caused by the waveform of the hot-rolled steel sheet H itself may cause a problem that uniform cooling cannot be performed in the rolling direction.

Therefore, for example, Patent Document 5 discloses a technique in which a steel plate having a corrugated shape is formed in a rolling direction, and in order to uniformize the cooling of the steel sheet, the cooling capacity of the upper cooling portion and the lower cooling portion is set to be the same, and the upper portion of the steel sheet is made the same. The effect of the attached water and the distance from the lower roller table can be minimized.

Advanced technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-74463

[Patent Document 2] Japanese Patent Laid-Open No. Hei 5-337505

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2005-271052

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2003-48003

[Patent Document 5] Japanese Patent Laid-Open No. Hei 6-328117

Summary of invention

However, the cooling method of Patent Document 1 does not consider the case where the hot-rolled steel sheet has a waveform in the rolling direction. As shown in Fig. 19, in the hot-rolled steel sheet H having the above-described waveform, the bottom of the waveform may be partially in contact with the conveying roller 220. Further, the hot-rolled steel sheet H is partially in contact with the apron (not shown in Fig. 19) provided as a support for preventing the hot-rolled steel sheet H from falling between the transport rollers 220 at the bottom of the corrugated shape. The situation. Heat in the waveform The rolled steel sheet H, which is in partial contact with the conveying roller 220 or the skirt, is more easily cooled than other portions by contact with heat. Therefore, there is a problem that the hot-rolled steel sheet H is unevenly cooled. That is, in Patent Document 1, it is not considered that the hot-rolled steel sheet has a corrugated shape, and the transport roller or the skirt is partially in contact with the hot-rolled steel sheet, and the contact portion is easily cooled by contact with heat. Therefore, as described above, there is a case where the hot-rolled steel sheet having the waveform formed cannot be uniformly cooled.

Further, in the technique described in Patent Document 2, the extremely low carbon steel having a relatively low hardness (softness) is subjected to γ-α metamorphism between the rolling stands of the finishing mill, and the purpose is not to perform uniform cooling. Further, the invention of Patent Document 2 does not relate to the case where the rolled material has a wave shape in the rolling direction, or the rolled material is called a tensile strength (TS) of 800 MPa or more, that is, a so-called high-tensile steel sheet steel. Therefore, when the rolled material is a hot-rolled steel sheet having a corrugated shape or a steel having a relatively high hardness, uniform cooling cannot be performed.

Further, in the cooling method of Patent Document 3, the degree of sharpness in the width direction of the steel sheet is measured, and the flow rate of the cooling water in the portion having a high degree of steepness is adjusted. However, when the flow rate of the cooling water in the width direction of the steel sheet is changed, it is difficult to make the temperature in the width direction of the sheet of the steel sheet uniform. Further, even in Patent Document 3, the case where the hot-rolled steel sheet has a wave shape in the rolling direction is not considered, and as described above, the hot-rolled steel sheet may not be uniformly cooled.

Moreover, since the hot-rolled steel sheet before the hole diameter of the cooling-type finishing mill of Patent Document 4 is cooled, it cannot be applied to a hot-rolled steel sheet which has been subjected to finish rolling and has a predetermined thickness. Further, even in Patent Document 4, it is not considered that a waveform is formed in the rolling direction of the hot-rolled steel sheet, and as described above, the hot-rolled steel sheet may not be uniformly cooled in the rolling direction.

Further, in the cooling method of Patent Document 5, the cooling ability of the upper cooling includes cooling of the water adhered to the upper portion of the steel sheet in addition to the cooling water supplied to the steel sheet from the upper water injection nozzle. Since the adhered water is affected by the sharpness of the waveform formed on the steel sheet or the speed of the sheet passing through the steel sheet, it is strictly impossible to specify the cooling ability of the steel sheet to which the water adheres. As a result, it is difficult to properly control the cooling capacity of the upper cooling. Therefore, it is also difficult to make the cooling ability of the upper cooling and the lower cooling the same. Further, when the cooling ability of the upper cooling and the lower cooling is the same, an example of the method for determining the cooling ability is exemplified, but the general determination method is not disclosed. Therefore, the cooling method of Patent Document 5 may not uniformly cool the hot-rolled steel sheet.

The present invention has been made in view of the above problems, and an object thereof is to uniformly cool a hot-rolled steel sheet which is hot-rolled by a finishing mill.

In order to achieve the object of solving the above problems, the present invention employs the following means.

which is,

(1) A hot-rolled steel sheet cooling apparatus according to the present invention, which is characterized in that a hot-rolled steel sheet which is hot-rolled by a finishing mill is cooled in a cooling section provided on a path of the through-plate, and is characterized in that it has a thermometer and is measured. a temperature of the hot-rolled steel sheet on the downstream side of the cooling section; a shape measuring the shape of the hot-rolled steel sheet on the downstream side of the cooling section; and an upper cooling apparatus cooling the upper surface of the hot-rolled steel sheet in the cooling section; a cooling device that cools the underside of the hot-rolled steel sheet in the cooling zone; the control device, the root Controlling the upper side cooling device and the lower side cooling device by controlling the temperature measurement result of the hot-rolled steel sheet obtained from the thermometer and the shape measurement result of the hot-rolled steel sheet obtained from the shape meter, thereby controlling the aforementioned cooling section At least one of the cooling heat transfer amount and the lower cooling heat transfer amount of the hot-rolled steel sheet; the control device includes: an average temperature calculating unit that sets the temperature of the hot-rolled steel sheet on the downstream side of the cooling section based on the temperature measurement result The average value of the time series is calculated as the average temperature, and the fluctuation speed calculation unit calculates the fluctuation speed of the hot-rolled steel sheet on the downstream side of the cooling section based on the shape measurement result, and the control direction determining unit is configured to vertically extend the hot-rolled steel sheet. The upward direction is regarded as the timing, and in the region where the fluctuation speed is positive, the upper surface is cooled by the average temperature in the range of one or more cycles of the wave shape of the hot-rolled steel sheet, and when the temperature of the hot-rolled steel sheet is low. The direction in which the amount of heat transfer is reduced is at least the direction in which the amount of cooling heat transfer in the lower portion is increased. In order to control the direction, when the temperature of the hot-rolled steel sheet is high with respect to the average temperature, at least one of a direction in which the amount of cooling heat transfer increases and a direction in which the amount of cooling heat transfer in the lower surface are decreased is used as the control direction. When the temperature of the hot-rolled steel sheet is low with respect to the average temperature in the region where the fluctuation speed is negative, at least one of a direction in which the amount of the upper cooling heat transfer amount increases and a direction in which the lower surface cooling heat transfer amount decreases is determined. When the temperature of the hot-rolled steel sheet is high with respect to the average temperature, at least one of a direction in which the amount of cooling heat transfer amount decreases and a direction in which the amount of cooling heat transfer in the lower surface increases is determined as the control direction. The cooling heat transfer amount total value adjusting unit determines the control direction determined by the control direction determining unit. The total value of the aforementioned upper cooling heat transfer amount and the lower surface cooling heat transfer amount of the hot-rolled steel sheet in the cooling section is adjusted.

(2) The hot-rolled steel sheet cooling device according to (1) above, wherein The position difference between the temperature measurement portion of the thermometer and the shape measurement portion of the shape meter on the hot-rolled steel sheet is preferably within 50 mm.

(3) The hot-rolled steel sheet cooling device according to the above (1) or (2), wherein the through-plate speed of the hot-rolled steel sheet in the cooling section is set to be in a range from 550 m/min or more to a mechanical limit speed. Inside.

(4) The hot-rolled steel sheet cooling device according to the above (3), wherein the hot-rolled steel sheet has a tensile strength of preferably 800 MPa or more.

(5) The hot-rolled steel sheet cooling device according to the above (3), wherein the finishing mill is preferably composed of a plurality of rolling stands, and between the rolling stands adjacent to each other, preferably further comprising the hot-rolled steel sheet. Cooling auxiliary cooling unit.

According to the above aspect of the present invention, the phase of the temperature of the hot-rolled steel sheet is detected, and by comparing the waveform of the hot-rolled steel sheet, the upper side cooling capacity and the lower side cooling capacity can be adjusted, and the amount of cooling heat transfer on the hot-rolled steel sheet can be adjusted. Cool the amount of heat transfer with below. Therefore, the hot-rolled steel sheet can be uniformly cooled by cooling the hot-rolled steel sheet by adjusting the cooling capacity.

1, 2‧‧‧ hot rolling equipment

11, 111‧‧‧ heating furnace

12, 112, 201‧‧‧ rough rolling mill

12a, 112a‧‧‧Work rolls

12b, 112b‧‧‧4 re-rolling extension

13, 113, 203‧‧‧ finishing mill

13a, 113a‧‧‧ fine rolls

14, 114, 142, 211‧‧‧ □ cooling device

14a, 114a, 142a‧‧‧ upper cooling unit

14b, 114b, 142b‧‧‧ lower cooling equipment Set

15, 115, 212‧‧‧ winding device

16, 116‧‧‧width rolling machine

31, 131, 146‧‧ ‧ cooling port

32, 132, 220‧‧‧ transport rollers

40‧‧‧ thermometer

41‧‧‧ Shape meter

50‧‧‧Control device

51‧‧‧Average temperature calculation unit

52‧‧‧Variation speed calculation unit

53‧‧‧Control Direction Determination Department

54‧‧‧Cooling heat transfer total value adjustment unit

133‧‧‧ skirt

140‧‧‧Rolling and rolling platform

202a~202d‧‧‧ rolling table

H‧‧‧Hot rolled steel plate

L‧‧‧Location gap

S‧‧‧single embryo

P1‧‧‧ Temperature Measurement Division

P2‧‧‧ Shape Measurement Division

Z1, Z2‧‧‧ split cooling interval

Fig. 1 is an explanatory view showing a hot rolling facility 1 having a hot-rolled steel sheet cooling device according to an embodiment of the present invention.

Fig. 2 is a schematic view showing the configuration of the cooling device 14 of the embodiment. Figure.

Fig. 3 is a schematic explanatory view showing the configuration in the vicinity of the cooling device 14 in the hot rolling facility 1.

Fig. 4 is a graph showing the relationship between the temperature fluctuation and the steepness of the hot rolled steel sheet H cooled in the representative strip ROT of the usual operation, and the upper graph shows the temperature change from the front end of the coil or the elapsed time of the fixed point, The side chart shows the distance from the front end of the coil or the steepness of the fixed point elapsed time.

Fig. 5 is a graph showing the relationship between the temperature fluctuation and the steepness of the hot rolled steel sheet H cooled in the representative strip ROT of the usual operation.

Fig. 6 shows a region where the rate of change of the hot-rolled steel sheet is positive, and the temperature of the hot-rolled steel sheet H becomes lower with respect to the average temperature of the hot-rolled steel sheet H, and the temperature of the hot-rolled steel sheet H becomes higher in a region where the fluctuation speed is negative. In the case where the amount of cooling heat transfer is reduced, the relationship between the temperature change of the hot-rolled steel sheet H and the degree of urgency when the amount of cooling heat transfer is increased is increased. The steepness of the waveform of the hot-rolled steel sheet H is a value obtained by dividing the amplitude of the waveform by the length of the rolling direction of the one-cycle component.

Fig. 7 shows a region where the fluctuation speed of the hot-rolled steel sheet H is positive, and the temperature of the hot-rolled steel sheet H becomes lower with respect to the average temperature of the hot-rolled steel sheet H, and the temperature of the hot-rolled steel sheet H changes in a region where the fluctuation speed is negative. When it is high, the upper heat transfer amount is increased, and the relationship between the temperature change of the hot-rolled steel sheet H and the suddenness when the amount of cooling heat transfer is reduced is shown.

Fig. 8 is an explanatory view showing the arrangement of the thermometer 40 and the shape meter 41 in the hot rolling apparatus 1.

Figure 9 is a view showing a modification of the cooling device 14 in the hot rolling facility 1. Figure.

Fig. 10 is a graph showing the relationship between the sharpness of the hot-rolled steel sheet H and the standard deviation of temperature.

Fig. 11 is a graph showing the relationship between the plate speed of the hot-rolled steel sheet H and the standard deviation of temperature.

Fig. 12 is an explanatory view showing a state in which a temperature standard deviation is formed in the width direction of the hot-rolled steel sheet H.

Fig. 13 is an explanatory view showing a hot rolling facility 2 for realizing a method of cooling a hot rolled steel sheet H according to another embodiment.

Fig. 14 is a schematic explanatory view showing the configuration of a cooling device 114 provided in the hot rolling facility 2.

Fig. 15A is an explanatory view showing a state in which the lowest point of the hot-rolled steel sheet H is in contact with the conveying roller 132.

Fig. 15B is an explanatory view showing a state in which the lowest point of the hot-rolled steel sheet H is in contact with the conveying roller 132 and the skirt 133.

Fig. 16A is a graph showing changes in temperature of the hot-rolled steel sheet H when the sheet speed of the hot-rolled steel sheet H is low.

Fig. 16B is a graph showing changes in temperature of the hot-rolled steel sheet H over time when the sheet speed of the hot-rolled steel sheet H is high.

Fig. 17 is an explanatory view of a finishing mill 113 capable of performing inter-rolling cooling.

Fig. 18 is an explanatory view showing a manufacturing method of a conventional hot-rolled steel sheet H.

Fig. 19 is an explanatory view showing a conventional cooling method of the hot-rolled steel sheet H.

Form for implementing the invention

Hereinafter, as an embodiment of the present invention, for example, a hot-rolled steel sheet cooling device for cooling a hot-rolled steel sheet used in automobiles, industrial machines, and the like will be described in detail with reference to the drawings.

Fig. 1 is a view schematically showing an example of a hot rolling facility 1 having a hot-rolled steel sheet cooling device of the present embodiment. The hot rolling facility 1 is a device for the purpose of winding the heated slabs S up and down with a roller and continuously rolling them to a thickness of at least 1 mm and winding them.

The hot rolling apparatus 1 has a heating furnace 11 for heating the flat embryo S, and a width direction rolling mill 16 for rolling the heated flat embryo S in the width direction in the heating furnace 11; 12, the flat embryo S rolled in the width direction is rolled from the upper and lower directions and made into a thick rod; the finishing mill 13 is continuously hot-finishing the thick rod to a predetermined thickness; the cooling device 14 The hot-rolled steel sheet H hot-rolled by the finishing mill 13 is cooled by cooling water, and the winding device 15 winds the hot-rolled steel sheet H cooled by the cooling device 14 into a coil shape.

The heating furnace 11 is provided with a side burner, an axial flow burner, and a top burner that blows the flame to heat the flat nail S with respect to the flat embryo S that is carried in from the outside through the loading port. The heating belts that are carried into the heating furnace 11 are sequentially heated by the heating belts formed in each zone, and further formed in the uniform zone in the final zone, and the top burner is used to uniformly heat the fillers S, thereby making it possible to The optimum temperature to transport the heat treatment. When the heating process of the heating furnace 11 is completed, the flat embryo S is transported outside the heating furnace 11 and moved toward the rolling step of the roughing mill 12.

The roughing mill 12 is directed to the spheroidal S that has been transported, and passes through the gap of the cylindrical rotating roller disposed across the plurality of rolling stands. For example, the roughing mill In the first rolling station, the flat blank S is hot-rolled only by the work rolls 12a placed on the upper and lower sides to form a thick rod. Next, the plurality of re-rolling mills 12b composed of the work rolls and the backup rolls are continuously rolled by the thick rods of the work rolls 12a. As a result, at the end of the rough rolling step, the thick rod is rolled to a thickness of about 30 to 60 mm and conveyed to the finishing mill 13.

The finishing mill 13 hot-rolls the thick rod that has been transported from the roughing mill 12 until the thickness thereof becomes about several mm. These finishing mills 13 pass the thick rods through the gaps of the finishing rolls 13a which are arranged across the 6 to 7 rolling stages and arranged in the upper and lower straight lines, and are slowly pressed down. The hot-rolled steel sheet H formed by the finishing mill 13 is transported to the cooling device 14 by a transport roller 32 which will be described later.

The cooling device 14 is a device for applying so-called thin-layer cooling to the hot-rolled steel sheet H conveyed from the finishing mill 13. As shown in Fig. 2, the cooling device 14 has a cooling water upper side cooling device 14a sprayed from the upper side cooling port 31 on the upper side of the hot-rolled steel sheet H moving on the delivery table 32, and a lower surface for the hot-rolled steel sheet H. The lower side cooling port 31 injects the cooling water lower side cooling device 14b. Further, a plurality of cooling ports 31 are provided for each of the upper cooling device 14a and the lower cooling device 14b.

Further, a cooling head (not shown) is connected to the cooling port 31. The cooling capacity of the upper side cooling device 14a and the lower side cooling device 14b is determined based on the number of the cooling ports 31. Further, the cooling device 14 may be configured by at least one of a thin layer of the upper and lower slant rods, a tubular thin layer, spray cooling, or the like. Further, the section in which the hot-rolled steel sheet H is cooled by the cooling device 14 corresponds to the cooling section of the present invention.

Further, as shown in FIG. 3, on the downstream side of the cooling section (that is, the cooling device 14), a temperature set at a measurement position in the rolling direction of the hot-rolled steel sheet H is disposed. The thermometer 40 for measuring the degree and the shape meter 41 for measuring the waveform of the hot-rolled steel sheet H at the same measurement position as the thermometer 40.

These thermometers 40 and the shape meter 41 are electronically connected to the control device 50 via a cable or the like. Moreover, the control device 50 is electronically connected to the upper side cooling device 14a and the lower side cooling device 14b via a cable or the like.

The thermometer 40 outputs the temperature measurement result of the hot-rolled steel sheet H to the control device 50. The shape meter 41 outputs the shape measurement result of the hot-rolled steel sheet H to the control device 50.

The control device 50 controls the upper side cooling device 14a and the lower side cooling device 14b based on the temperature measurement result obtained from the thermometer 40 and the shape measurement result obtained from the shape meter 41, thereby controlling the upper surface cooling heat transfer of the hot rolled steel sheet H in the cooling section. The amount is at least one of the amount of cooling heat transfer below.

The control device 50 includes an average temperature calculation unit 51, a fluctuation speed calculation unit 52, a control direction determination unit 53, and a cooling heat transfer amount total value adjustment unit 54 as functions realized by the execution program. The role of each of these functional units will be described later.

As shown in Fig. 1, the winding device 15 winds the hot-rolled steel sheet H that has been cooled by the cooling device 14 at a predetermined winding temperature. The hot-rolled steel sheet H wound in a coil shape by the winding device 15 is transported to the outside of the hot rolling facility 1.

As described above, in the hot rolling facility 1 configured, the upper cooling device 14a, the lower cooling device 14b, the thermometer 40, the shape gauge 41, and the control device 50 are configured as a hot-rolled steel plate cooling device of the embodiment.

Next, a cooling method of the hot-rolled steel sheet H realized by the hot rolling facility 1 configured as described above will be described.

In the following description, as shown in FIG. 19, the hot-rolled steel sheet H hot-rolled by the finishing mill 13 has a waveform in which the surface height (wave height) in the rolling direction fluctuates. Moreover, in the following description, when the hot-rolled steel sheet H is cooled, the influence of the adhered water accumulated on the hot-rolled steel sheet H is ignored. In fact, as a result of investigations by the inventors, it can be seen that the influence of the adhered water accumulated on the hot-rolled steel sheet H is almost complete.

First, before cooling the hot-rolled steel sheet H by the cooling device 14, the cooling capacity (upper cooling capacity) of the upper cooling device 14a of the cooling device 14 and the cooling capacity (lower cooling capacity) of the lower cooling device 14b are individually adjusted. The upper side cooling capacity and the lower side cooling capacity are adjusted by the heat transfer coefficient of the upper surface of the hot-rolled steel sheet H cooled by the upper side cooling device 14a and the heat transfer coefficient of the hot-rolled steel sheet H cooled by the lower side cooling device 14b, respectively.

Here, a method of calculating the heat transfer coefficient on the upper surface and the lower surface of the hot-rolled steel sheet H will be described. The heat transfer coefficient is a value obtained by dividing the temperature difference (heat energy) equivalent to a unit time from the unit area by the temperature difference between the heat conductor and the heat medium (heat transfer coefficient = cooling heat transfer amount / temperature difference). The temperature difference here is the difference between the temperature of the hot-rolled steel sheet H measured by the thermometer on the inlet side of the cooling device 14 and the temperature of the cooling water used by the cooling device 14.

Further, the cooling heat transfer amount is a value obtained by multiplying the temperature difference between the hot-rolled steel sheet H and the specific heat and mass (cooling heat transfer amount = temperature difference × specific heat × mass). That is, the amount of cooling heat transfer is the amount of cooling heat transfer of the hot-rolled steel sheet H of the cooling device 14, and is the temperature difference between the hot-rolled steel sheet H measured by the thermometer on the inlet side of the cooling device 14 and the thermometer on the outlet side, respectively. Specific heat of hot rolled steel sheet H, And the value of the mass of the hot-rolled steel sheet H cooled by the cooling device 14 is individually multiplied.

The heat transfer coefficient of the hot-rolled steel sheet H calculated as described above is divided into the heat transfer coefficient of the upper surface and the lower surface of the hot-rolled steel sheet H. These upper and lower heat transfer coefficients are processed as follows, and are calculated using a ratio obtained in advance.

In other words, the heat transfer coefficient of the hot-rolled steel sheet H when the hot-rolled steel sheet H is cooled by the upper side cooling device 14a and the heat transfer coefficient of the hot-rolled steel sheet H when the hot-rolled steel sheet H is cooled only by the lower side cooling device 14b are measured.

At this time, the amount of cooling water from the upper side cooling device 14a is set to be the same as the amount of cooling water from the lower side cooling device 14b. The reciprocal of the ratio of the heat transfer coefficient when the upper side cooling device 14a is used to the heat transfer coefficient when the lower side cooling device 14b is used is the amount of cooling water of the upper side cooling device 14a when the ratio of the upper and lower heat transfer coefficients to be described later is "1". The ratio of the amount of cooling water to the amount of cooling water of the lower side cooling device 14b.

The upper and lower ratio of the amount of cooling water obtained in this manner is multiplied by the amount of cooling water of the upper side cooling device 14a or the amount of cooling water of the lower side cooling device 14b when cooling the hot-rolled steel sheet H, and the upper surface of the hot-rolled steel sheet H is calculated. The ratio of the thermal conductivity below (the ratio of the upper and lower heat transfer coefficients).

Further, although the heat transfer coefficient of the hot-rolled steel sheet H cooled only by the upper side cooling device 14a and only the lower side cooling device 14b is used, the above-described side cooling device 14a and the lower side cooling device 14b may be used for cooling. The heat transfer coefficient of the hot rolled steel sheet H. In other words, the heat transfer coefficient of the hot-rolled steel sheet H when the amount of cooling water of the upper side cooling device 14a and the lower side cooling device 14b is changed can be measured, and the ratio of the heat transfer coefficient can be used to calculate the heat conduction between the upper surface and the lower surface of the hot-rolled steel sheet H. The ratio of the coefficients.

The heat transfer coefficient of the hot-rolled steel sheet H is calculated as described above, and the heat transfer coefficient of the upper surface and the lower surface of the hot-rolled steel sheet H can be calculated from the above ratio (upper and lower heat transfer coefficient ratio) of the heat transfer coefficient of the upper surface and the lower surface of the hot-rolled steel sheet H.

Here, in order to uniformly cool the hot-rolled steel sheet H, the cooling ability of the upper side cooling device 14a and the lower side cooling device 14b (control of the amount of cooling heat transfer amount of the hot-rolled steel sheet H and the amount of cooling heat transfer below) is adjusted. The inventors of the present application have obtained the following knowledge in addition to the results of the positive review.

The inventors of the present application have repeatedly reviewed the results of the temperature standard deviation caused by the cooling in the state in which the hot-rolled steel sheet H is generated, and have revealed the following facts.

In the hot-rolled steel sheet H in the through-plate, the measurement position of the hot-rolled steel sheet H in the rolling direction is performed by the thermometer 40 and the shape meter 41 at a sampling interval of a certain time interval (the measurement position will be referred to below). For the case of the fixed point, the temperature measurement and the shape measurement are performed, and the time series data of the temperature measurement result and the shape measurement result are obtained.

Further, the temperature measurement region of the thermometer 40 includes the entire region in the width direction of the hot-rolled steel sheet H. In addition, the shape refers to the amount of fluctuation in the height direction of the hot-rolled steel sheet H observed by the fixed-point measurement, which is obtained by using the amount of movement of the hot-rolled steel sheet in the H-through direction and by the line height of the wave or the line integral of the variation component. The severity of the situation. Also, the amount of change per unit time, that is, the rate of change, is simultaneously determined. Further, the measurement region of the shape includes the entire region in the width direction of the hot-rolled steel sheet H in the same manner as the temperature measurement region. Further, when the sampling time of each measurement result is multiplied by the plate speed (transport speed) of the hot-rolled steel sheet H, the position in the rolling direction of the hot-rolled steel sheet H in which each measurement result can be obtained can be calculated. that is Yes, when the time of sampling the time series data of each measurement result is multiplied by the plate speed, the time series data of each measurement result can be connected with the position of the rolling direction.

Using this time series data, first, the total value of the amount of cooling heat transfer on the hot-rolled steel sheet H and the amount of cooling heat transfer below is adjusted. Specifically, the total value of the cooling heat transfer amount of the hot-rolled steel sheet H and the lower cooling heat transfer amount is adjusted so that the time-averaged value of the temperature measured by the thermometer 40 matches the predetermined target value.

Further, when the total value of the cooling heat transfer amount and the lower cooling heat transfer amount is adjusted, for example, the theoretical value obtained in advance can be obtained with respect to the experimental theoretical formula represented by the three-dimensional equation or the like, and the correction and the actual operation can be performed according to the setting. The learning value of the actual performance error is used to perform switching control of the cooling head connected to the cooling device 14. Alternatively, the switch of the cooling head may be fed back or feed forward controlled according to the temperature actually measured by the thermometer 40.

Next, the information obtained from the thermometer 40 and the shape meter 41 described above will be described with respect to the cooling control of the conventional ROT. Fig. 4 is a graph showing the relationship between the temperature variation and the steepness of the hot-rolled steel sheet H cooled in the representative strip ROT of the usual operation. The upper heat transfer coefficient ratio of the hot-rolled steel sheet H of Fig. 4 is 1.2:1, and the upper side cooling capacity is higher than the lower side cooling capacity. The graph on the upper side of Fig. 4 shows the temperature variation from the front end of the coil or the elapsed time of the fixed point. The graph on the lower side of Fig. 4 shows the distance from the front end of the coil or the steepness of the elapsed time of the fixed point.

The area A of Fig. 4 is the area before the end portion of the strip shown in Fig. 3 is bitten by the coiler of the winding device 15 (the area where the shape is poor due to no tension). Area B of Figure 4 is the area after the front end of the strip is bitten by the coiler (The waveform changes to a flat area due to the influence of the unit tension). It is expected to improve a large temperature variation (that is, a temperature standard deviation) which is generated in a region where the shape of the hot-rolled steel sheet H is not flat.

Therefore, the inventors of the present invention have obtained the following knowledge by actively conducting experiments with the aim of suppressing an increase in the temperature standard deviation of ROT.

Fig. 5 is a view showing the temperature fluctuation component of the same shape steepness in the cooling of the representative strip ROT in the normal operation as in Fig. 4 . The temperature fluctuation component is a residual obtained by subtracting the time series of the temperature from the actual steel sheet temperature (hereinafter referred to as "average temperature"). For example, the average temperature can average the range of the waveform of the hot-rolled steel sheet H by one cycle or more.

However, in principle the average temperature is the average of the range of period units. Further, it was confirmed from the work data that the average temperature in the range of one cycle was not much different from the average temperature in the range of two cycles or more.

Therefore, it suffices to calculate at least the average temperature in the range of one cycle of the waveform. The upper limit of the range of the waveform of the hot-rolled steel sheet H is not particularly limited, but it is preferably set to 5 cycles to obtain an average temperature with sufficient accuracy. Further, even if the range of the average range is not in the range of 2 to 5 cycles, an average temperature which can be tolerated can be obtained.

Here, the upward direction of the hot-rolled steel sheet H in the vertical direction (the direction orthogonal to the upper and lower faces of the hot-rolled steel sheet H) is regarded as the positive direction, and the fluctuation speed measured at the fixed point is positive, and the hot-rolled steel sheet is opposed to the hot-rolled steel sheet. When the waveform of H has a range average temperature of one cycle or more, and the temperature of the hot-rolled steel sheet H (the temperature measured by the fixed point) is low, the direction of the decrease in the amount of cooling heat transfer and the amount of cooling heat transfer below are increased. At least one of the directions is determined as the control direction, and when the temperature of the hot-rolled steel sheet H is high with respect to the average temperature, at least one of the direction in which the amount of cooling heat transfer increases and the direction in which the cooling heat transfer amount decreases is controlled. Direction to decide.

Further, in a region where the fluctuation speed measured at the fixed point is negative, when the temperature of the hot-rolled steel sheet H is low with respect to the average temperature, at least the direction in which the amount of cooling heat transfer is increased and the direction in which the amount of cooling heat transfer in the lower portion is decreased is at least One of them is determined as the control direction. When the temperature of the hot-rolled steel sheet H is high with respect to the average temperature, at least one of the direction in which the amount of cooling heat transfer is decreased and the direction in which the amount of cooling heat transfer in the lower portion is increased is determined as the control direction.

Further, as described above, when at least one of the cooling heat transfer amount and the lower cooling heat transfer amount of the hot-rolled steel sheet H in the cooling section is adjusted according to the determined control direction, as shown in FIG. It is understood that the temperature variation occurring in the region A where the hot-rolled steel sheet H is not flat may be reduced.

The case where the operation opposite to the above is performed will be described below. In the region where the fluctuation speed measured at the fixed point is positive, when the temperature of the hot-rolled steel sheet H is lower than the average temperature of the hot-rolled steel sheet H, the direction in which the upper cooling heat transfer amount is increased and the lower cooling heat transfer amount is decreased. At least one of them is determined as the control direction, and when the temperature of the hot-rolled steel sheet H is high with respect to the average temperature, at least one of the direction in which the amount of cooling heat transfer is decreased and the direction in which the amount of cooling heat transfer in the lower portion is increased is determined as the control direction. .

Further, in the region where the fluctuation speed measured by the fixed point is negative, when the temperature of the hot-rolled steel sheet H is low with respect to the average temperature, at least one of the direction in which the amount of cooling heat transfer is decreased and the direction in which the amount of cooling heat transfer in the lower portion is increased is increased. As a control When the temperature of the hot-rolled steel sheet H is high with respect to the above-mentioned average temperature, at least one of the direction in which the amount of cooling heat transfer is increased and the direction in which the amount of cooling heat transfer in the lower portion is decreased is determined as the control direction.

Further, as described above, when at least one of the cooling heat transfer amount and the lower cooling heat transfer amount of the hot-rolled steel sheet H in the cooling section is adjusted according to the determined control direction, as shown in FIG. It is understood that the temperature fluctuation occurring in the region A where the hot-rolled steel sheet H is not flat is expanded. However, even in the case described here, it does not become a precondition for changing the cooling stop temperature.

When this relationship is utilized, in order to reduce the temperature variation, that is, the temperature standard deviation, it is necessary to adjust the cooling ability of either the upper cooling device 14a and the lower cooling device 14b of the cooling device 14. However, Table 1 has compiled the above relationship table.

The hot-rolled steel sheet cooling device of the present embodiment is a method for realizing the above-described cooling method. In other words, the average temperature calculation unit 51 of the control device 50 calculates the time-averaged value of the temperature measurement result obtained by the temperature measurement of the thermometer 40 as the average temperature. Moreover, the fluctuation speed calculation unit 52 calculates the fluctuation speed of the hot-rolled steel sheet H based on the shape measurement result obtained from the shape meter 41 in a time-series manner.

When the control direction determining portion 53 is oriented in the vertical direction of the hot-rolled steel sheet H When the upper direction is positive, the temperature at which the fluctuation speed measured at the fixed point is positive, and the temperature of the hot-rolled steel sheet H (the temperature measured at the fixed point) is lower than the average temperature in the range of one or more cycles of the hot-rolled steel sheet H. At least one of the direction in which the cooling heat transfer amount is decreased and the direction in which the cooling heat transfer amount is increased is determined as the control direction, and when the temperature of the hot-rolled steel sheet H is high with respect to the average temperature, the amount of cooling heat is increased. At least one of the direction of increase and the direction in which the amount of cooling heat transfer is reduced is determined as the control direction.

Further, the control direction determining unit 53 is in a region where the fluctuation speed measured at the fixed point is negative, and when the temperature of the hot-rolled steel sheet H is low with respect to the average temperature, the direction of the upper cooling heat transfer amount is increased and the cooling heat transfer is performed below. At least one of the directions in which the amount is reduced is determined as the control direction, and when the temperature of the hot-rolled steel sheet H is high with respect to the average temperature, at least one of the direction in which the amount of cooling heat transfer is decreased and the direction in which the amount of cooling heat transfer in the lower portion is increased is determined. To control the direction.

In addition, the cooling and heat transfer amount total value adjustment unit 54 adjusts the total value of the upper surface cooling heat transfer amount and the lower surface cooling heat transfer amount of the hot-rolled steel sheet H in the cooling section based on the control direction determined as described above.

Further, when the cooling capacity of the upper side cooling device 14a and the cooling capacity of the lower side cooling device 14b are adjusted, for example, the cooling head attached to the cooling port 31 of the upper side cooling device 14a and the cooling port 31 connected to the lower side cooling unit 14b can be connected. The cooling nozzles are individually controlled by switches. Alternatively, the cooling capacity of each of the cooling heads of the upper side cooling device 14a and the lower side cooling device 14b can be controlled. That is, at least one of the water amount density, the pressure, and the water temperature of the cooling water sprayed from each of the cooling ports 31 can be adjusted.

Further, the cooling heads (cooling ports 31) of the upper side cooling device 14a and the lower side cooling device 14b can be intermittently controlled to adjust the flow rate or pressure of the cooling water sprayed from the upper side cooling device 14a and the lower side cooling device 14b. For example, when the cooling capacity of the upper cooling device 14a exceeds the cooling capacity of the lower cooling device 14b before intermittently controlling the cooling nozzle, the cooling nozzles constituting the upper cooling device 14a are preferably intermittently controlled.

By the cooling capacity thus adjusted, the hot-rolled steel sheet H can be uniformly formed by spraying the cooling water onto the hot-rolled steel sheet H from the upper cooling device 14a and injecting the cooling water from the lower cooling device 14b to the lower surface of the hot-rolled steel sheet H. cool down.

Thereafter, the hot-rolled steel sheet H cooled by the cooling device 14 is subjected to fixed-point measurement at the same temperature and shape by the thermometer 40 and the shape meter 41, and measured as time series data. Further, the measurement range of the temperature includes the entire area in the width direction of the hot-rolled steel sheet H. In addition, the shape shows the amount of fluctuation in the height direction of the hot-rolled steel sheet H observed by the fixed-point measurement. Further, the measurement region of the shape includes the entire region in the width direction of the hot-rolled steel sheet H in the same manner as the measurement region of the temperature. When the time of the sampling is multiplied by the plate speed, the time series data of the measurement results such as the temperature and the fluctuation speed can be connected to the position of the rolling direction.

As described with reference to FIGS. 4, 5, 6, and 7, the temperature at the fixed point of the hot-rolled steel sheet H is positive, and the temperature at the fixed point of the hot-rolled steel sheet H is lower than the average temperature at the fixed point. At the time, the upper side cooling capacity (the amount of cooling heat transfer above) is made small, whereby the temperature standard deviation can be reduced. Similarly, the lower side cooling capacity (lower cooling heat transfer amount) is made larger, thereby reducing the temperature standard Quasi-bias. In order to reduce the temperature standard deviation by using this relationship, it is necessary to adjust the cooling ability of the cooling device 14a and the lower cooling device 14b on the upper side of the cooling device 14.

In other words, as long as the temperature fluctuation positions connected to the waveform of the hot-rolled steel sheet H are grasped, it can be understood that the temperature standard deviation which has occurred until now is caused by either the upper side cooling or the lower side cooling. Therefore, it is possible to adjust the ratio of the upper and lower heat transfer coefficients to reduce the temperature standard deviation by the increase and decrease direction (control direction) of the upper side cooling capacity (the upper cooling heat transfer amount) and the lower side cooling capacity (the lower cooling heat transfer amount). .

Further, depending on the magnitude of the temperature standard deviation, the ratio of the upper and lower heat transfer coefficients can be determined such that the temperature standard deviation is within an allowable range, for example, a range from a minimum value to a minimum value + 10 ° C. On the other hand, by setting the temperature standard deviation within a range from the minimum value to the minimum value + 10 ° C, the unevenness of the stress, the tensile strength, and the like can be suppressed within the manufacturing tolerance range, and the hot-rolled steel sheet H is uniform. Ground cooling. Moreover, although there is a considerable degree of unevenness, as long as the cooling water volume density ratio is within ±5% with respect to the cooling water volume density which becomes the minimum value of the standard deviation of the temperature, the standard deviation of the temperature may range from the minimum value to the minimum value + Within the range of 10 ° C. In other words, when the cooling water amount density is used, the ratio of the upper limit of the cooling water amount density (the cooling water amount density ratio) to within ±5% with respect to the cooling water amount density ratio which becomes the minimum value of the temperature standard deviation is expected. However, the allowable range does not necessarily include the same water volume density.

According to the above embodiment, the cooling capacity of the upper side cooling device 14a and the lower side cooling device 14b is adjusted in advance, and after cooling the hot-rolled steel sheet H, the temperature is adjusted based on the measurement result of the temperature and waveform of the hot-rolled steel sheet H to be cooled. The cooling capacity of the upper side cooling device 14a and the cooling capacity of the lower side cooling device 14b. As described above, since the cooling capacity of the upper side cooling device 14a and the lower side cooling device 14b can be feedback-controlled and qualitatively and quantitatively adjusted to an appropriate cooling capacity, the uniformity of the hot-rolled steel sheet H to be cooled later can be further improved.

As described above, according to the present embodiment, the temperature standard deviation of the hot-rolled steel sheet H can be minimized, and the hot-rolled steel sheet H can be uniformly cooled.

In the above embodiment, the temperature and shape of the hot-rolled steel sheet H are measured at the same measurement position by the thermometer 40 and the shape meter 41. However, after the investigation by the inventors of the present application, the measurement of the thermometer 40 and the shape meter 41 is known. The location is strictly different. Specifically, as shown in FIG. 8, it is found that the positional difference (distance) L between the temperature measurement portion P1 of the thermometer 40 on the hot-rolled steel sheet H and the shape measurement portion P2 of the shape gauge 41 is preferably within 50 mm, more preferably 30 mm. Within the inside, the temperature and shape of the hot rolled steel sheet H can be appropriately grasped.

As shown in Fig. 8, the direction of the position difference L between the thermometer 40 and the measuring portion 41 may be the direction of the plate passing through the hot-rolled steel sheet H, or may be the width direction of the hot-rolled steel sheet H, that is, any direction. In the example of FIG. 8, the thermometer 40 is disposed on the upstream side of the shape meter 41, but the shape meter 41 may be disposed on the upstream side of the thermometer 40 instead.

Here, the reason why the positional difference L between the thermometer 40 and the shape meter 41 should be within 50 mm is described. Table 2 shows that when the present invention is applied to an actual machine, under the conditions of the same upper and lower heat transfer coefficient ratio, the steepness, and the plate speed, the position difference L between the thermometer 40 and the shape meter 41 is measured for the rolling direction. -200~+200mm range change The relationship between the standard deviation of the temperature of the hot-rolled steel sheet H and the difference between the standard deviation of each temperature and the minimum value (minimum value in Table 2 = 10.0) (the difference between the standard deviations from the minimum values).

On the other hand, in Table 2, the position difference L when the shape measurement portion P2 of the shape gauge 41 is set on the downstream side is displayed with a positive value based on the temperature measurement portion P1 of the thermometer 40, and the shape is set on the upstream side. The positional difference L at the shape measurement position P2 of the gauge 41 is shown by a negative value. When the temperature measurement portion P1 of the thermometer 40 and the shape measurement portion P2 of the shape meter 41 are set to be the same, the position difference L becomes zero.

As shown in Table 2, when the positional difference L between the thermometer 40 and the shape meter 41 is within 50 mm regardless of the positive or negative, the difference between the standard deviations of the minimum values can be reduced to +10 ° C or less.

Therefore, when the position difference L between the thermometer 40 and the measurement unit 41 is within 50 mm, it is possible to determine the increase or decrease of the upper side cooling capacity and the lower side cooling capacity in order to reduce the temperature standard deviation as in the above embodiment. Direction (control direction), and feedback control of the cooling capacity of the upper side cooling device 14a and the lower side cooling device 14b can be performed.

As shown in Fig. 9, in the above embodiment, the cooling zone cooled by the hot-rolled steel sheet H can be divided into a plurality of rolling directions, for example, two divided cooling zones Z1 and Z2. A cooling device 14 is provided in each of the divided cooling sections Z1 and Z2. Further, a thermometer 40 and a shape meter 41 are separately provided on the boundary between the divided cooling sections Z1 and Z2, that is, on the downstream side of the divided cooling sections Z1 and Z2. In the present embodiment, the cooling section is divided into two divided cooling sections, but the number of divisions is not limited thereto, and can be arbitrarily set. For example, the cooling interval can be divided into one to five divided cooling sections.

At this time, the temperature and waveform of the hot-rolled steel sheet H on the downstream side of the divided cooling sections Z1 and Z2 are individually measured by the respective thermometers 40 and the respective shape gauges 41. Then, based on these measurement results, the cooling capacities of the upper side cooling device 14a and the lower side cooling device 14b of each divided cooling zone Z1, Z2 are controlled. At this time, the cooling capacity is controlled so that the temperature standard deviation of the hot-rolled steel sheet H is within an allowable range, for example, the range from the minimum value to the minimum value + 10 ° C as described above. Thereby, at least one of the upper surface cooling heat transfer amount and the lower surface cooling heat transfer amount of the hot-rolled steel sheet H of each of the divided cooling sections Z1 and Z2 can be adjusted.

For example, in the divided cooling zone Z1, based on the measurement results of the thermometer 40 and the shape meter 41 on the downstream side, the cooling capacity of the upper cooling device 14a and the lower cooling device 14b is feedback-controlled to adjust the cooling heat transfer amount and the lower cooling. At least one of the amount of heat transfer.

Further, in the divided cooling zone Z2, the upper side cooling device 14a and the lower side can be fed back based on the measurement results of the thermometer 40 and the shape meter 41 on the downstream side. The cooling capacity of the side cooling device 14b can also be fed forward control. In either case, at least one of the upper cooling heat transfer amount and the lower cooling heat transfer amount may be adjusted in the divided cooling zone Z2.

On the other hand, the method of controlling the cooling capacity of the upper side cooling device 14a and the lower side cooling device 14b is the same as that of the above-described embodiment described with reference to FIGS. 4 to 7 based on the measurement results of the thermometer 40 and the shape meter 41. Therefore, the detailed description is omitted. .

At this time, in each of the divided cooling sections Z1 and Z2, since at least one of the upper cooling heat transfer amount and the lower cooling heat transfer amount of the hot-rolled steel sheet H can be adjusted, finer control can be performed. Therefore, the hot rolled steel sheet H can be more uniformly cooled.

In the above embodiment, when at least one of the upper cooling heat transfer amount and the lower cooling heat transfer amount of the hot-rolled steel sheet H is adjusted for each of the divided cooling sections Z1 and Z2, the measurement of the thermometer 40 and the shape meter 41 is performed. In addition to the results, at least one of the sharpness of the hot-rolled steel sheet H waveform and the sheet speed of the hot-rolled steel sheet H can be used. For example, in each coil, since the steepness of the hot-rolled steel sheet H or the speed of the through-plate is also non-fixed, these steepness or plate speeds are also considered.

After investigation by the inventors of the present application, for example, as the sharpness of the H-wave shape of the hot-rolled steel sheet shown in Fig. 10 is increased, the temperature standard deviation of the hot-rolled steel sheet H is larger. Further, for example, when the sheet speed of the hot-rolled steel sheet H is changed to a high speed as shown in Fig. 11, the temperature standard deviation of the hot-rolled steel sheet H becomes large.

As described above, when the steepness or the plate speed of the hot-rolled steel sheet H is not fixed, the temperature standard deviation of the upper and lower heat transfer coefficient ratios may be changed. It is evaluated qualitatively, but it cannot be quantitatively and correctly evaluated. Therefore, for example, the temperature standard deviation corresponding to the steepness of the hot-rolled steel sheet H or the sheet speed is first determined, and at least the steepness or the sheet speed of the hot-rolled steel sheet H is measured to correct the temperature standard deviation. Then, the upper surface cooling heat transfer amount and the lower surface cooling heat transfer amount of the hot-rolled steel sheets H of the divided cooling sections Z1 and Z2 are corrected based on the corrected temperature standard deviation. Thereby, the hot-rolled steel sheet H can be cooled more uniformly.

Further, according to the present embodiment, even in the plate width direction of the hot-rolled steel sheet H, it is possible to finish rolling to obtain a uniform shape or material. Fig. 12 is a view showing an example of a waveform generated by different amplitudes in the width direction of the plate due to the central projection. As described above, even when a temperature standard deviation occurs due to a waveform having a different amplitude generated in the width direction of the sheet, the temperature standard deviation in the sheet width direction can be reduced by the above-described embodiment.

As a result of the positive review by the inventors of the present invention, it has been found that the plate speed of the hot-rolled steel sheet H is set to be in a range from 550 m/min or more to a mechanical limit speed, whereby the hot rolling can be more uniformly produced. Steel plate H.

When the plate speed of the hot-rolled steel sheet H is set to 550 m/min or more, even if the hot-rolled steel sheet H is sprayed with the cooling water, the influence of the adhered water on the hot-rolled steel sheet H is remarkably small. Therefore, uneven cooling of the hot-rolled steel sheet H due to adhesion of water can also be avoided.

Fig. 13 is a view schematically showing an example of the hot rolling facility 2 of another embodiment. The hot rolling apparatus 2 is an apparatus for the purpose of winding the heated slabs S up and down with a roll and continuously rolling them, and rolling them up to a minimum of 1.2 mm and winding them.

The hot rolling facility 2 has a heating furnace 111 for heating the flat embryo S, and a width rolling mill 116 for rolling the heated flat nail S in the width direction in the heating furnace 111, which is already in the width The rough rolling mill 112 in which the directionally rolled flat nail S is rolled from the upper and lower directions and is made into a thick rod, the finishing mill 113 which continuously heat-rolls the thick rod to a predetermined thickness, and the hot rolling mill 113 is used. The hot-rolled steel sheet H of the finish rolling is cooled by cooling water 114 and the hot-rolled steel sheet H cooled by the cooling device 114 is wound into a coil-shaped winding device 115.

The heating furnace 111 is provided with a side burner, an axial flow burner, and a top burner that blows the flame to heat the flat nail S with respect to the flat nail S that is carried in from the outside through the loading port. The heating belts formed in each zone by the flat embryos S carried into the heating furnace 111 are sequentially heated, and further, in the soaking zone formed in the final zone, the top burners are uniformly heated by the top burner to thereby make them Heat treatment that can be transported at the optimum temperature. When the heat treatment of the heating furnace 111 is all completed, the flat embryo S is transported outside the heating furnace 111 and moved toward the rolling step of the roughing mill 112.

In the rough rolling extension 112, the flat embryo S conveyed from the heating furnace 111 passes through a gap of a cylindrical rotating roll disposed across a plurality of rolling stands. For example, in the roughing mill 112, the flat blank S is hot-rolled by the work rolls 112a disposed on the upper and lower rolls, and is used as a thick rod.

Next, the plurality of four-roll rolling mills 112b composed of the work rolls and the backup rolls, which have passed through the work rolls 112a, are continuously rolled. As a result, at the end of the rough rolling process, the thick rod is rolled to a thickness of about 30 to 60 mm and conveyed to the finishing mill 113. However, the composition of the rough rolling extension 112 The number of rollers and the like can be arbitrarily set without being limited to those described in the embodiment.

The finishing mill 113 finishes the thick rod conveyed from the rough rolling extension 112 to a thickness of several mm. These finishing mills 113 pass the thick rods through the gaps of the finishing rolls 113a which straddle the 6 to 7 rolling stages and are arranged in the upper and lower straight lines, and gradually press them down. The hot-rolled steel sheet H that has been finish-rolled by the finishing mill 113 is transported to the cooling device 114 by the transport roller 132 (see FIG. 14). Further, the calender having the above-described one of the upper and lower straight lines to the finish roll 113a is also referred to as a so-called rolling stand.

Further, a cooling device 142 (assisted cooling) for performing inter-roll cooling (auxiliary cooling) during finish rolling is disposed between each of the rolling rolls 113a arranged between the 6 and 7 rolling stands (that is, between rolling and rolling) Device). A detailed description of the device configuration and the like of the cooling device 142 will be described later with reference to Fig. 17 . 13 is a view showing a case where the cooling device 142 is disposed at two places of the finishing mill 113, but the cooling device 142 may be configured to be disposed between all of the rolling rolls 113a, or may be provided only in a part.

The cooling device 114 is a device for applying a thin layer or a spray nozzle cooling to the hot-rolled steel sheet H conveyed from the finishing mill 113. As shown in FIG. 14, the cooling device 114 has an upper cooling device 114a that sprays cooling water from the upper cooling port 131 on the hot-rolled steel sheet H that is moved on the conveying roller 132 of the output table, and a lower surface for the hot-rolled steel sheet H. The lower side cooling device 114b that sprays the cooling water from the lower side cooling port 131.

A plurality of cooling ports 131 are provided for each of the upper cooling device 114a and the lower cooling device 114b. Further, a cooling head (not shown) is connected to the cooling port 131. According to the number of the cooling ports 131, the upper side cooling is determined. The cooling capacity of the device 114a and the lower cooling device 114b. Further, the cooling device 114 may be configured by at least one of a thin layer of the upper and lower slant rods, a tubular thin layer, spray cooling, or the like.

When the cooling device 114 adjusts the cooling capacity of the upper cooling device 114a and the cooling capacity of the lower cooling device 114b, for example, the cooling nozzle connected to the cooling port 131 of the upper cooling device 114a and the cooling nozzle 114b connected to the lower cooling device 114b can be connected. The cooling nozzles of the cooling port 131 are individually switched and controlled.

Alternatively, the operating parameters of the respective cooling nozzles of the upper cooling device 114a and the lower cooling device 114b can be controlled. That is, at least one of the water amount density, the pressure, and the water temperature of the cooling water sprayed from each of the cooling ports 131 can be adjusted.

Moreover, the cooling heads (cooling ports 131) of the upper side cooling device 114a and the lower side cooling device 114b can be intermittently controlled to adjust the flow rate or pressure of the cooling water sprayed from the upper side cooling device 114a and the lower side cooling device 114b. For example, when the cooling capacity of the upper cooling device 114a exceeds the cooling capacity of the lower cooling device 114b before intermittently controlling the cooling nozzle, the cooling nozzles constituting the upper cooling device 114a are preferably intermittently controlled.

As shown in FIG. 13, the winding device 115 winds the hot-rolled steel sheet H cooled by the cooling device 114 with a predetermined winding temperature. The hot-rolled steel sheet H wound in a coil shape by the winding device 115 is conveyed outside the hot rolling facility 2.

In the cooling device 114 of the hot rolling facility 2 configured as described above, when the hot-rolled steel sheet H having a waveform in which the surface height (wave height) fluctuates in the rolling direction is cooled, as described above, it can be appropriately adjusted The hot-rolled steel sheet H can be uniformly formed by the cooling water sprayed from the upper cooling device 114a and the water density, pressure, water temperature, and the like of the cooling water sprayed from the lower cooling device 114b. cool down. However, particularly when the speed of the hot-rolled steel sheet H is slow, since the time during which the hot-rolled steel sheet H partially contacts the conveying roller 132 or the skirt 133 becomes long, the conveying roller 132 or the skirt of the hot-rolled steel sheet H is used. The contact portion of 133 is easily cooled by contact with heat, so the cooling becomes uneven. The reason for this non-uniformity of cooling will be described below with reference to the drawings.

As shown in Fig. 15A, when the hot-rolled steel sheet H has a wave shape in the rolling direction, the bottom of the waveform of the hot-rolled steel sheet H may partially contact the conveying roller 132. Moreover, as shown in FIG. 15B, between the conveyance rollers 132 adjacent to the rolling direction, there is a case where the skirt 133 is provided as a support for preventing the hot rolled steel sheet H from falling. At this time, the bottom of the waveform of the hot-rolled steel sheet H may be partially in contact with the conveyance roller 132 and the skirt 133. As described above, in the hot-rolled steel sheet H, the portion which is in partial contact with the conveying roller 132 or the skirt 133 is more easily cooled by contact with heat than other portions. Therefore, the hot rolled steel sheet H is unevenly cooled.

In particular, when the plate speed of the hot-rolled steel sheet H is low, the time during which the hot-rolled steel sheet H partially contacts the conveyance roller 132 or the skirt 133 becomes long. As a result, as shown in Fig. 16A, the portion where the hot-rolled steel sheet H partially contacts the conveying roller 132 or the skirt 133 (the portion surrounded by the broken line in Fig. 16A) is easily cooled than the other portions, and the hot-rolled steel sheet H does not. Cool evenly.

On the other hand, when the plate speed of the hot-rolled steel sheet H is made high, the above contact time becomes short. Further, when the speed of the sheet is increased, the hot-rolled steel sheet H rebounds from the contact of the conveying roller 132 or the skirt 133, and the hot-rolled steel sheet H in the sheet becomes floated from the conveying roller 132 or the skirt 133. The state of the situation.

Moreover, when the speed of the plate of the hot-rolled steel sheet H is increased, except for the above In addition to the state in which the hot-rolled steel sheet H is lifted from the conveyance roller 132 or the skirt 133, the contact time or the number of contacts of the hot-rolled steel sheet H with the conveyance roller 132 or the skirt 133 is reduced, so the contact is made. The temperature drop will become smaller and can be ignored.

Therefore, by increasing the speed of the through-plate, the contact heat removal can be suppressed, and as shown in Fig. 16B, the hot-rolled steel sheet H can be more uniformly cooled. Further, the inventors have found that in addition to the above-described upper and lower heat transfer amount control, the hot-rolled steel sheet H can be sufficiently and uniformly cooled by setting the through-plate speed to 550 m/min or more.

However, the above knowledge is obtained for cooling of the corrugated hot-rolled steel sheet H, but regardless of the height of the waveform, since the lowest point of the hot-rolled steel sheet H is in contact with the conveyance roller 132 or the skirt 133, regardless of the waveform The height, the speed of the plate speed is very effective for uniform cooling.

In addition, when the plate speed of the hot-rolled steel sheet H is set to 550 m/min or more, since the hot-rolled steel sheet H is in a state of being floated from the conveyance roller 132 or the skirt 133, even in this state, even for the hot-rolled steel sheet H sprays the cooling water and does not have the presence of adhering water on the hot rolled steel sheet H as is conventional. Therefore, it is possible to avoid the case where the hot-rolled steel sheet H is unevenly cooled due to the adhesion of water.

As described above, when the plate speed of the hot-rolled steel sheet H in the cooling zone is set to 550 m/min or more, the hot-rolled steel sheet H having a waveform in which the wave height periodically fluctuates in the rolling direction can be more uniformly cooled. .

However, the higher the speed of the hot-rolled steel sheet H, the better, but it is impossible to exceed the mechanical limit speed (for example, 1550 m/min). Therefore, in essence, the through-plate speed of the hot-rolled steel sheet H in the cooling section can be set to be It is within the range of 550 m/min or more to the mechanical limit speed. When the upper limit value (operation upper limit speed) of the through-plate speed at the time of actual operation is set in advance, it is preferable to set the plate speed of the hot-rolled steel sheet H from 550 m/min or more to the upper limit of the working speed (for example, 1200 m/min). ) Within the range below.

As a matter of course, the hot-rolled steel sheet cooling device described using FIG. 3 can be applied to the hot rolling equipment 2, and the combination of the cooling heat transfer amount of the hot-rolled steel sheet H and the cooling heat transfer amount below, and the high speed of the sheet can be combined. Speed setting (set to a range from 550 m/min or more to mechanical limit speed).

Further, in general, it is known that a hot-rolled steel sheet H having a large tensile strength (especially a tensile strength (TS) of 800 MPa or more, and actually 1400 MPa is an upper limit, that is, a steel sheet called a so-called high-tensile steel sheet. When the hardness of the hot-rolled steel sheet H is increased, the heat generated during the rolling delay of the hot rolling equipment 2 is increased. Therefore, it is known that the speed of the sheet passing through the hot-rolled steel sheet H of the cooling device 114 (that is, the cooling section) is lowered, whereby the cooling is sufficiently performed.

However, when the plate speed of the hot-rolled steel sheet H of the cooling device 114 is lowered, and the hot-rolled steel sheet H is formed with a wave shape, the hot-rolled steel sheet H may be in partial contact with the conveying roller 132 or the skirt 133 as described above. Therefore, the contact portion is easily cooled by contact with heat, and uneven cooling is performed.

Therefore, the inventors of the present application have found a situation in which a finishing roll 113a (i.e., rolling and rolling stand) may be provided in the finishing mill 113 of the hot rolling facility 2, for example, across a 6 to 7 rolling stand. Cooling (so-called cooling between rolls) is performed to suppress the above-described processing heat, and the plate speed of the hot-rolled steel sheet H of the cooling device 114 is set to 550 m/min or more. In the following reference picture 17, for the above-mentioned cooling between the rolling mills.

Fig. 17 is an explanatory view of a finishing mill 113 capable of performing inter-rolling cooling, and is illustrated for expanding one of the rolling mills for the purpose of explaining one part of the finishing mill 113. In FIG. 17, the same components as those in the above embodiment are denoted by the same reference numerals. As shown in Fig. 17, the finishing mill 113 is provided with a plurality of (three in Fig. 17) rolling and rolling stations 140, and the rolling and rolling station has one of the upper and lower straight lines, the finishing rolls 113a and the like. A cooling device 142, which is a device for cooling a nozzle or a spray nozzle, is provided between each rolling and rolling table 140. The hot-rolled steel sheet H can be cooled between the rolling and rolling stations 140.

As shown in Fig. 17, the cooling device 142 has a hot-rolled steel sheet H that is transported by the finishing mill 113, and the cooling water is sprayed from the upper side to the upper side cooling device 142a, and the hot-rolled steel sheet H is from the lower side. The side causes the cooling water to be ejected from the lower side cooling device 142b. A plurality of cooling ports 146 are provided for each of the upper cooling device 142a and the lower cooling device 142b. Further, a cooling head (not shown) is connected to the cooling port 146. Further, the cooling device 142 may be configured by at least one of a thin layer of the upper and lower slant rods, a tubular thin layer, spray cooling, and the like.

In the finishing mill 113 having the configuration shown in Fig. 17, in particular, when the tensile strength (TS) of the hot-rolled steel sheet H is 800 MPa or more, the heat generation of the hot-rolled steel sheet H can be suppressed by performing the inter-rolling cooling. Thereby, the sheet speed of the hot-rolled steel sheet H of the cooling device 114 can be maintained at 550 m/min or more. Therefore, the hot-rolled steel sheet H can be sufficiently and uniformly cooled by releasing the following problem, and the problem is that the hot-rolled steel sheet H and the conveying roller 132 are protected by the conventional low-speed sheet passing speed. The skirt 133 is partially in contact with each other The contact portion is easily cooled by contact with heat.

In the above embodiment, the cooling of the hot-rolled steel sheet H of the cooling device 114 is preferably carried out in a range from the temperature at the exit of the finishing mill to the temperature at which the hot-rolled steel sheet H has a temperature of 600 °C. The temperature region of the hot-rolled steel sheet H having a temperature of 600 ° C or higher is a so-called film boiling region. That is, at this time, the so-called migration boiling region is avoided, and the hot-rolled steel sheet H can be water-cooled in the film boiling region. When the cooling water is sprayed on the surface of the hot-rolled steel sheet H in the migration boiling zone, the portion of the hot-rolled steel sheet H covered with the vapor film and the portion directly sprayed by the cooling water to the hot-rolled steel sheet H are mixed. Therefore, the hot rolled steel sheet H cannot be uniformly cooled.

On the other hand, in the film boiling region, since the entire surface of the hot-rolled steel sheet H is cooled by the vapor film coating, the hot-rolled steel sheet H can be uniformly cooled. Therefore, in the present embodiment, the hot-rolled steel sheet H can be more uniformly cooled in the range of the temperature of the hot-rolled steel sheet H of 600 ° C or more.

Hereinabove, the present invention has been described with reference to the accompanying drawings, but the present invention is not limited to the embodiments described above. It is obvious that various modifications and alterations are obvious to those skilled in the art within the scope of the patent application, and it is understood that these are naturally within the technical scope of the present invention.

[Examples]

In order to demonstrate that the hot-rolled steel sheet is uniformly cooled by setting the sheet speed of the hot-rolled steel sheet to 550 m/min or more, the inventors have conducted a cooling test of the hot-rolled steel sheet as an example.

(Example 1)

The hot-rolled steel sheet having a plate thickness of 2.5 mm, a width of 1200 mm, a tensile strength of 400 MPa, and a moderate degree of 2% wave was changed and cooled by the passing speed of the cooling device. Specifically, the through-plate speed is changed to 400 m/min, 450 m/min, 500 m/min, 550 m/min, 600 m/min, 650 m/min, and each of the hot-rolled steel sheets at each plate speed is cooled. The order was carried out 20 times.

Then, the temperature of the hot-rolled steel sheet at the time of winding was measured, and the average value (CT temperature fluctuation amount) of the standard deviation of the temperature fluctuation was calculated using the temperature measurement result. The results of evaluation of the calculated CT temperature fluctuation amount are shown in Table 3 below. On the other hand, when the CT temperature fluctuation amount is larger than 25 ° C as the evaluation criteria, it is evaluated as cooling unevenly, and when the CT temperature fluctuation amount is 25 ° C or lower, it is evaluated as uniform cooling.

As shown in Table 3, when the sheet speed was 500 m/min or less, the amount of fluctuation in the CT temperature was not sufficiently reduced (higher than 25 ° C), and uniform cooling of the hot-rolled steel sheet was not sufficiently performed. On the other hand, when the plate speed is 550 m/min or more, the CT temperature variation can be suppressed to 25 ° C or less, and the hot rolled steel sheet can be used. Uniform cooling. In particular, when the plate speed is 600 m/min or more, it is known that the CT temperature is suppressed to 10 ° C or less (8 ° C, 6 ° C), and it is known that the condition can achieve uniform cooling of the hot-rolled steel sheet. For better.

(Example 2)

The hot-rolled steel sheet having a plate thickness of 2.5 mm, a width of 1200 mm, a tensile strength of 800 MPa, and a moderate degree of 2% medium wave is cooled between the rolling mills so that the temperature at the outlet side of the finish rolling becomes 880 ° C, and is cooled. The plate speed of the device is changed and cooled. Specifically, the through-plate speed is changed to 400 m/min, 450 m/min, 500 m/min, 550 m/min, 600 m/min, 650 m/min, and each of the hot-rolled steel sheets at each plate speed is cooled. The order was carried out 20 times.

Then, the temperature of the hot-rolled steel sheet at the time of winding was measured, and the average value (CT temperature fluctuation amount) of the standard deviation of the temperature fluctuation was calculated using the temperature measurement result. The results of evaluation of the calculated CT temperature fluctuation amount are shown in Table 4 below. On the other hand, the evaluation criteria were the same as in the first embodiment described above, and the inter-rolling table cooling was not performed only when the plate speed was 400 m/min.

As shown in Table 4, even if the plate speed is 500m/min or less, even When the inter-rolling cooling is performed, the amount of fluctuation in the CT temperature is not sufficiently reduced (higher than 25 ° C), and uniform cooling of the hot-rolled steel sheet is not sufficiently performed. On the other hand, when the plate speed is 550 m/min or more, the amount of change in the CT temperature can be suppressed to 25 ° C or less, and uniform cooling of the hot-rolled steel sheet can be performed.

Further, in the case of cooling between the rolling stands (that is, in the case shown in Table 4), the amount of fluctuation in the CT temperature can be suppressed even for the hot-rolled steel sheet having a relatively high hardness (tensile strength of 800 MPa). In other words, it is found that all the steel materials, particularly the steel having a higher hardness, can be obtained by rolling between the rolling mills of the finishing mill, except that the through-plate speed is 550 m/min or more when the hot-rolled steel sheet is cooled. Uniform cooling.

Industrial availability

The present invention is useful in the case where a hot-rolled steel sheet which is hot-rolled by a finishing mill and has a waveform in which the surface height fluctuates in the rolling direction is cooled.

1‧‧‧ hot rolling equipment

13‧‧‧ Finishing mill

14‧‧‧Cooling device

14a‧‧‧Upside cooling unit

14b‧‧‧Bottom cooling unit

15‧‧‧Winding device

40‧‧‧ thermometer

41‧‧‧ Shape meter

50‧‧‧Control device

51‧‧‧Average temperature calculation unit

52‧‧‧Variation speed calculation unit

53‧‧‧Control Direction Determination Department

54‧‧‧Cooling heat transfer total value adjustment unit

H‧‧‧Hot rolled steel plate

Claims (5)

A hot-rolled steel sheet cooling device for cooling a hot-rolled steel sheet hot-rolled by a finishing mill in a cooling zone provided on a path of the through-plate, characterized by having a thermometer for measuring a downstream side of the cooling section The temperature of the hot-rolled steel sheet; the shape meter measures the shape of the hot-rolled steel sheet on the downstream side of the cooling section; the upper side cooling device cools the upper surface of the hot-rolled steel sheet in the cooling section; and the lower side cooling device is attached The cooling section cools the lower surface of the hot-rolled steel sheet; and the control device controls the upper side cooling based on the temperature measurement result of the hot-rolled steel sheet obtained from the thermometer and the shape measurement result of the hot-rolled steel sheet obtained from the shape meter The apparatus and the lower cooling device control at least one of a cooling heat transfer amount and a lower cooling heat transfer amount of the hot-rolled steel sheet in the cooling zone; and the control device includes an average temperature calculating unit according to the The temperature measurement result is a time-average value of the temperature of the hot-rolled steel sheet on the downstream side of the cooling section The average temperature is calculated; variation rate calculating unit, the system according to the shape of the measurement result of the change in speed of the downstream side of the hot rolled steel sheet cooling section calculated; The control direction determining unit is configured such that the upward direction of the vertical direction of the hot-rolled steel sheet is positive, and the average temperature in the range of one or more cycles of the wave shape of the hot-rolled steel sheet in the region where the fluctuation speed is positive is When the temperature of the hot-rolled steel sheet is low, at least one of a direction in which the amount of cooling heat transfer is reduced and a direction in which the amount of cooling heat transfer in the lower surface is increased is determined as a control direction, and the hot-rolled steel sheet is opposed to the average temperature. When the temperature is high, at least one of the direction in which the upper cooling heat transfer amount is increased and the direction in which the lower cooling heat transfer amount is decreased is determined as the control direction, and the region where the fluctuation speed is negative is the same as the average temperature. When the temperature of the hot-rolled steel sheet is low, at least one of the direction in which the amount of the above-described cooling heat transfer amount increases and the direction in which the cooling heat transfer amount decreases is determined as the control direction, and the hot-rolled steel sheet is opposed to the average temperature. When the temperature is high, at least one of the direction in which the above cooling heat transfer amount is decreased and the direction in which the lower cooling heat transfer amount is increased And a cooling heat transfer amount total value adjusting unit that adjusts the upper surface cooling heat transfer amount of the hot-rolled steel sheet in the cooling section and the lower surface according to the control direction determined by the control direction determining unit The total value of the cooling heat transfer amount. The hot-rolled steel sheet cooling device according to claim 1, wherein a difference in position between the temperature measurement portion of the thermometer and the shape measurement portion of the shape meter on the hot-rolled steel sheet is within 50 mm. For example, in the hot-rolled steel plate cooling device of claim 1 or 2, The through-plate speed of the hot-rolled steel sheet in the cooling section is set to be in a range from 550 m/min or more to a mechanical limit speed. A hot-rolled steel sheet cooling device according to claim 3, wherein the hot-rolled steel sheet has a tensile strength of 800 MPa or more. The hot-rolled steel sheet cooling device according to claim 3, wherein the finishing mill is composed of a plurality of rolling stands, and further has auxiliary cooling for performing auxiliary cooling of the hot-rolled steel sheet between the rolling stands adjacent to each other. Device.