KR101498843B1 - Hot rolled steel sheet cooling device - Google Patents

Abstract

A hot-rolled steel sheet cooling apparatus of the present invention comprises: a thermometer for measuring a temperature of a hot-rolled steel sheet; A shape measuring device for measuring the shape of the hot-rolled steel sheet; An upper cooling device for cooling the upper surface of the hot-rolled steel sheet in a cooling section; A lower cooling device for cooling the lower surface of the hot-rolled steel sheet in a cooling section; A control device for controlling at least one of an upper surface cooling heat generation amount and a lower surface cooling heat generation amount of the hot-rolled steel sheet in the cooling section by controlling the upper cooling device and the lower cooling device based on the temperature measurement result and the shape measurement result; Respectively.

Description

[0001] HOT ROLLED STEEL SHEET COOLING DEVICE [0002]

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.

For example, hot-rolled steel sheets used for automobiles and industrial machines are generally manufactured through rough rolling and finish rolling. 18 is a diagram schematically showing a conventional method of manufacturing a hot-rolled steel sheet. In the manufacturing process of the hot-rolled steel sheet, first, the slab S obtained by continuously casting molten steel adjusted to a predetermined composition is rolled by the roughing mill 201, and thereafter, the finish made up of a plurality of rolling stands 202a to 202d And hot rolled by a rolling machine 203 to form a hot-rolled steel sheet H having a predetermined thickness. The hot-rolled steel sheet H is cooled by the cooling water injected from the cooling device 211, and then wound in a coil shape by a winding device 212.

The cooling device 211 is a facility for performing so-called lamina cooling on the hot-rolled steel sheet H conveyed from the finishing mill 203 in general. The cooling device 211 injects cooling water from the upper side of the hot-rolled steel sheet H moving on the run-out table from the upper side in the vertical direction as cooling water through the cooling nozzle, The hot-rolled steel sheet H is cooled by spraying cooling water through the lamina as a classification water.

Conventionally, for example, Patent Document 1 discloses a technique for preventing surface defects of the steel sheet by reducing the surface temperature difference between the upper and lower surfaces of the steel sheet. According to the technique disclosed in Patent Document 1, on the basis of the surface temperature difference obtained by simultaneously measuring the surface temperatures of the upper and lower surfaces of the steel sheet with the thermometer during cooling by the cooling device, the number of cooling water supplied to the upper and lower surfaces of the steel sheet Adjust the ratio.

In addition, for example, in Patent Document 2, γ-α transformation of a pressurized medium is started and completed by cooling the pressurized steel material by using an injection spray between two adjacent stands of the finishing mill, Discloses a technique for preventing deterioration of mail order.

Further, for example, in Patent Document 3, the steepness of the steel plate front end is measured by a steepness meter installed on the side of the rolling mill outlet, and the flow rate of the cooling water is changed in the width direction according to the measured steepness, To prevent the penetration of foreign matter.

For example, Patent Document 4 discloses a technique for solving a plate thickness distribution of a wave shape in the plate width direction of a hot-rolled steel sheet and for uniforming the plate thickness in the plate width direction, And controlling the difference between the heat transfer rate and the minimum heat transfer rate to fall within a predetermined value range.

Here, the hot-rolled steel sheet H to be manufactured by the manufacturing method shown in Fig. 18 has a run-out table (hereinafter sometimes referred to as " ROT " In the rolling direction (arrow direction in Fig. 19) on the conveying roll 220 of the conveying rollers 220. [ In this case, the upper and lower surfaces of the hot-rolled steel sheet H are cooled unevenly. That is, there is a problem in that uniform cooling can not be performed in the rolling direction due to the cooling deviation due to the wave shape of the hot-rolled steel sheet H itself.

Thus, for example, in Patent Document 5, in order to equalize cooling of a steel sheet in which a wave shape is formed in the rolling direction, influence of the distance between the upper water on the steel sheet and the lower table roller The cooling capacity of the upper cooling and that of the lower cooling are made equal to each other.

Japanese Patent Application Laid-Open No. 2005-74463 Japanese Patent Application Laid-Open No. 5-337505 Japanese Patent Application Laid-Open No. 2005-271052 Japanese Patent Application Laid-Open No. 2003-48003 Japanese Patent Application Laid-Open No. 6-328117

However, the cooling method of Patent Document 1 does not consider the case where the hot-rolled steel sheet has a wave shape in the rolling direction. In the hot-rolled steel sheet H having the wave shape described above, as shown in Fig. 19, there is a case where it locally contacts with the transport roll 220 at the bottom of the wave shape. The hot-rolled steel sheet H is also in contact with the apron (not shown in Fig. 19) provided as a support for preventing the hot-rolled steel sheet H from sinking between the conveying rolls 220 in the wave- . In the hot rolled steel sheet H of the wave shape, the portion locally contacting with the transport roll 220 or the apron becomes easier to cool than other portions due to contact heat generation. As a result, the hot-rolled steel sheet H is unevenly cooled. That is, in Patent Document 1, it is not considered that the conveying roll or the apron and the hot-rolled steel sheet are locally brought into contact with each other because the hot-rolled steel sheet has a wave shape, and the contact portion is easily cooled by contact heat generation. Therefore, there are cases where the hot-rolled steel sheet having such a wave shape can not be uniformly cooled.

In addition, the technique described in Patent Document 2 is for the purpose of γ-α transformation of the extremely low hardness (loose) extremely low carbon steel between the stands of the finishing mill, and does not aim at uniform cooling. The invention of Patent Document 2 is not concerned with cooling in the case where the rolled material has a wave shape in the rolling direction or when the material to be rolled is a steel material called so-called high-tensile steel having a tensile strength (TS) of 800 MPa or more. There is a possibility that uniform cooling may not be performed when the rolled material is a hot rolled steel sheet having a wavy shape or when it is a steel material having relatively high hardness.

Further, in the cooling method of Patent Document 3, the steepness in the width direction of the steel sheet is measured, and the flow rate of the cooling water in the portion where the steepness is high is adjusted. However, if the flow rate of cooling water in the direction of the width of the steel plate is changed, it becomes difficult to make the temperature in the direction of the width of the steel plate uniform. Also in Patent Document 3, there is no consideration of the case where the hot-rolled steel sheet has a wave shape in the rolling direction, and the hot-rolled steel sheet may not be uniformly cooled as described above.

In addition, since the cooling of the hot-rolled steel sheet immediately before the finishing mill roll bite is performed, the cooling of the patent document 4 can not be applied to the hot-rolled steel sheet which has been finished and has a predetermined thickness. Also in Patent Document 4, there is no consideration of the case where a wave shape 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 not only the cooling by the cooling water supplied from the upper injection nozzle to the steel sheet, but also cooling by the water on the upper side of the steel sheet. This loading number is influenced by the wave-like steepness formed on the steel sheet and the passing speed of the steel sheet, and therefore the cooling ability of the steel sheet due to the mounting number can not be precisely specified. Then, it is difficult to precisely control the cooling ability of the upper cooling. Therefore, it is difficult to make the cooling capacities of the upper cooling and the lower cooling the same. In addition, while one example of a method for determining these cooling capacities is exemplified when the cooling capacities of the upper cooling and the lower cooling are the same, a universal determination method is not disclosed. Therefore, the cooling method of Patent Document 5 may not uniformly cool the hot-rolled steel sheet.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems described above, and its object is to uniformly cool a hot rolled steel sheet hot-rolled by a finishing mill.

The present invention solves the above problems and adopts the following means in order to achieve these objects.

In other words,

(1) A hot-rolled steel sheet cooling apparatus according to one aspect of the present invention is a hot-rolled steel sheet cooling apparatus for cooling a hot-rolled steel sheet hot-rolled by a finishing rolling machine in a cooling section provided on a path of the hot- A thermometer for measuring the temperature of the hot-rolled steel sheet in the hot-rolled steel sheet; A shape measuring device for measuring the shape of the hot-rolled steel sheet on the downstream side of the cooling section; An upper cooling device for cooling the upper surface of the hot-rolled steel sheet in the cooling section; A lower cooling device for cooling the lower surface of the hot-rolled steel sheet in the cooling section; And the upper cooling device and the lower cooling device are controlled 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- And a control device for controlling at least one of an upper surface cooling heat generation amount and a lower cooling heat generation amount of the hot-rolled steel sheet on the downstream side of the cooling section based on the temperature measurement result, As an average temperature; A fluctuation speed calculating section for calculating a fluctuation speed of the hot rolled steel sheet on the downstream side of the cooling section based on the shape measurement result; When the temperature of the hot-rolled steel sheet is lower than the average temperature in the range of one cycle or more of the wave shape of the hot-rolled steel sheet in the region where the fluctuation speed is constant, Wherein at least one of a direction in which the upper surface cooling heat generation amount is decreased and a direction in which the lower surface cooling heat generation amount is increased is determined as a control direction and when the temperature of the hot rolled steel sheet is higher than the average temperature, And a direction in which the cooling heat generation amount is lowered as the control direction, and when the temperature of the hot-rolled steel sheet is lower than the average temperature in the region where the fluctuation speed is not greater, the upper surface cooling heat generation amount is increased Direction and the direction in which the cooling heat generation amount is decreased is referred to as " And a control direction in which at least one of a direction in which the upper surface cooling heat generation amount is decreased and a direction in which the lower surface cooling heat generation amount is increased is determined as the control direction when the temperature of the hot- A determination unit; And a cooling heat value total value adjusting unit for adjusting a total value of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot rolled steel sheet in the cooling section based on the control direction determined by the control direction determination unit.

(2) In the hot-rolled steel sheet cooling apparatus according to (1), it is preferable that the positional deviation between the temperature measurement point of the thermometer and the shape measurement point of the thermo-sensitive steel sheet on the hot-rolled steel sheet is within 50 mm.

(3) In the hot-rolled steel plate cooling apparatus according to (1) or (2), the passing speed of the hot-rolled steel sheet in the cooling section is set within a range of 550 m / min or more to a mechanical limit speed or less .

(4) In the hot-rolled steel sheet cooling apparatus according to (3), the tensile strength of the hot-rolled steel sheet is preferably 800 MPa or more.

(5) In the hot-rolled steel sheet cooling apparatus according to (3), the finish rolling mill is constituted by a plurality of rolling stands, and an auxiliary cooling apparatus for performing auxiliary cooling of the hot-rolled steel sheet is provided between the adjacent rolling stands .

According to this aspect of the present invention, it is possible to adjust the upper cooling capacity and the lower cooling capacity by detecting the phase of the temperature of the hot-rolled steel sheet and comparing it with the wave shape of the hot-rolled steel sheet, Can be adjusted. Therefore, the hot-rolled steel sheet can be cooled uniformly by cooling the hot-rolled steel sheet with the adjusted cooling capacity thereafter.

1 is an explanatory view showing a hot rolling apparatus 1 having a hot-rolled steel sheet cooling apparatus according to an embodiment of the present invention.
Fig. 2 is an explanatory diagram showing an outline of the configuration of the cooling device 14 in the present embodiment. Fig.
Fig. 3 is an explanatory view showing an outline of the configuration in the vicinity of the cooling device 14 in the hot rolling equipment 1. Fig.
4 is a graph showing the relationship between the temperature variation and the steepness of the hot-rolled steel sheet H in the cooling of the ROT of a typical strip in a normal operation, and the graph on the upper side shows the temperature fluctuation with respect to the distance from the coil tip, And the graph on the lower side shows the steepness with respect to the distance from the tip of the coil or the elapsed time of the vertex.
5 is a graph showing the relationship between the temperature variation and the steepness level of the hot-rolled steel sheet H in cooling the ROT of a typical strip in a normal operation.
6 is a graph showing the relationship between the upper surface cooling heat generation amount and the upper surface cooling heat generation amount when the temperature of the hot-rolled steel plate H is lower than the average temperature of the hot-rolled steel sheet H in the region where the fluctuation speed H of the hot- And the relationship between the temperature variation of the hot-rolled steel sheet H and the steepness level when the cooling heat generation amount is increased. The steepness degree of the wave shape of the hot-rolled steel sheet H, the amplitude of the wave shape, Divided by the length.
7 is a graph showing an increase in the amount of heat generation on the upper surface of the hot-rolled steel sheet H when the temperature of the hot-rolled steel sheet H is lower than the average temperature of the hot-rolled steel sheet H in the region where the fluctuation speed of the hot- A graph showing the relationship between the temperature variation of the hot-rolled steel sheet H and the steepness level when the cooling heat generation amount is reduced.
Fig. 8 is an explanatory view showing the arrangement of the thermometer 40 and the mold surface 41 in the hot rolling equipment 1. Fig.
Fig. 9 is an explanatory view showing a modified example of the cooling device 14 in the hot rolling equipment 1. Fig.
10 is a graph showing the relationship between the steepness and the temperature standard deviation of the hot-rolled steel sheet H. Fig.
11 is a graph showing the relationship between the sheet speed and the temperature standard deviation of the hot-rolled steel sheet H. Fig.
12 is an explanatory view showing a state in which a temperature standard deviation is formed in the direction of the width of the hot-rolled steel sheet H. Fig.
13 is an explanatory view showing a hot rolling apparatus 2 for realizing a cooling method for hot-rolled steel sheet H in another embodiment;
Fig. 14 is an explanatory view showing an outline of the configuration of the cooling device 114 disposed in the hot rolling facility 2. Fig.
Fig. 15A is an explanatory view showing a state in which the lowermost point of the hot-rolled steel sheet H is in contact with the conveying roll 132; Fig.
15B is an explanatory view showing a state in which the lowermost point of the hot-rolled steel sheet H is in contact with the transport roll 132 and the apron 133;
16A is a graph showing a change with time in the temperature of the hot-rolled steel plate H when the passing speed of the hot-rolled steel plate H is low.
16B is a graph showing a change with time of the temperature of the hot-rolled steel sheet H when the hot-rolled steel sheet H has a high passing speed.
17 is an explanatory diagram of a finish rolling mill 113 capable of cooling between stands.
18 is an explanatory view showing a conventional method of manufacturing a hot-rolled steel sheet H. Fig.
Fig. 19 is an explanatory view showing a cooling method of a conventional hot-rolled steel sheet H. Fig.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as an embodiment of the present invention, a hot-rolled steel sheet cooling apparatus for cooling a hot-rolled steel sheet used for automobiles and industrial machines, for example, will be described in detail with reference to the drawings.

Fig. 1 schematically shows an example of a hot rolling equipment 1 having a hot-rolled steel sheet cooling apparatus according to the present embodiment. The hot rolling equipment 1 is a facility for rolling a continuously heated slab S between upper and lower rolls, thinning the slab S to a minimum of 1 mm, and winding it.

The hot rolling equipment 1 includes a heating furnace 11 for heating the slab S, a widthwise rolling mill 16 for rolling the slab S heated in the heating furnace 11 in the width direction, A roughing mill 12 for rolling and straightening the slab S rolled up and down in a vertical direction, a finishing mill 13 for continuously performing hot rolling at a predetermined thickness up to a predetermined thickness, and a finishing mill 13 A cooling device 14 for cooling the hot-rolled steel sheet H hot-finished and rolled by the cooling device 14 by cooling water, and a winding device 15 for winding the hot-rolled steel sheet H cooled by the cooling device 14 into a coil shape .

In the heating furnace 11, a side burner, an axial flow burner, and a loop burner for heating the slab S by spraying a flame are arranged on the slab S carried in from the outside through the entry port. The slabs S conveyed into the heating furnace 11 are heated uniformly in the respective heating zones formed in the respective zones and the slab S is uniformly heated using the loop burner in the crack zone formed in the final zone, Heat treatment is performed so as to be able to be transported to the optimum temperature. When all of the heat treatment in the heating furnace 11 is finished, the slab S is conveyed out of the heating furnace 11, and the process proceeds to the rolling step by the roughing mill 12. [

The rough rolling mill 12 passes the gap of the cylindrical rotary rolls disposed over the plurality of stands to the slab S that has been conveyed. For example, in the roughing mill 12, the slab S is hot-rolled only by the work rolls 12a arranged on the upper and lower sides in the first stand to form a rough bar. Subsequently, the coarse bar passed through the work roll 12a is further continuously rolled by a plurality of quadruple rolling machines 12b constituted by a work roll and a backup roll. As a result, at the end of this rough rolling process, the roughing is rolled to a thickness of about 30 to 60 mm, and is then conveyed to the finish rolling mill 13.

The finishing mill 13 finish-rolls the rough bar conveyed from the roughing mill 12 until its thickness becomes several millimeters. These finish rolling mills 13 pass the joining bar through the gap of the finish rolling roll 13a arranged in the upper and lower straight lines over 6 to 7 stands and gradually lower it. The hot-rolled steel sheet H which is finely rolled by the finishing mill 13 is conveyed to the cooling device 14 by a conveying roll 32 to be described later.

The cooling device 14 is a facility for performing so-called lamina cooling on the hot-rolled steel sheet H conveyed from the finish rolling mill 13. As shown in Fig. 2, the cooling device 14 is provided with an upper cooling device (not shown) for ejecting cooling water from the upper cooling hole 31 to the upper surface of the hot-rolled steel sheet H moving on the conveying roll 32 of the run- And a lower cooling device 14b for spraying cooling water from the lower cooling hole 31 to the lower surface of the hot-rolled steel sheet H. A plurality of cooling holes 31 are provided for each of the upper cooling device 14a and the lower cooling device 14b.

Further, a cooling header (not shown) is connected to the cooling port 31. The cooling capacity of the upper cooling device 14a and the lower cooling device 14b is determined by the number of the cooling holes 31. [ Further, the cooling device 14 may be constituted by at least one of upper and lower spiral lamina, pipe lamina, spray cooling and the like. The section in which the hot-rolled steel sheet H is cooled by the cooling device 14 corresponds to the cooling section in the present invention.

3, on the downstream side of the cooling section (that is, the cooling device 14), a thermometer 40 for measuring the temperature of the measurement position determined in the rolling direction of the hot-rolled steel sheet H, a thermometer 40 And a shape measuring device 41 for measuring the wave shape of the hot-rolled steel sheet H at the same measurement position.

The thermometer 40 and the mold surface 41 are electrically connected to the control device 50 through a cable or the like. The control device 50 is electrically connected to the upper cooling device 14a and the lower cooling device 14b through 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 form system 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 cooling device 14a and the lower cooling device 14b based on the temperature measurement result obtained from the thermometer 40 and the shape measurement result obtained from the shape measuring device 41, At least one of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-

The control device 50 is a function realized by execution of a program and includes an average temperature calculation section 51, a variation speed calculation section 52, a control direction determination section 53 and a cooling heat value total value adjustment section 54 Respectively. The role of each of these functional units will be described later.

The winding device 15 winds the hot-rolled steel sheet H cooled by the cooling device 14 at a predetermined winding temperature as shown in Fig. The hot-rolled steel sheet H wound in a coil shape by the winding device 15 is conveyed out of the hot rolling equipment 1. [

The upper cooling device 14a, the lower cooling device 14b, the thermometer 40, the form system 41 and the control device 50 in the hot rolling apparatus 1 constructed as described above are used in the present embodiment The hot-rolled steel plate cooling apparatus of the present invention is constituted.

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

In the following description, the hot-rolled steel sheet H hot-rolled by the finishing mill 13 has a wave shape that changes its surface height (wave height) in the rolling direction, as shown in Fig. In the following description, when the hot-rolled steel sheet H is cooled, the influences of the stored water stored on the hot-rolled steel sheet H are ignored. In fact, as a result of the investigation by the inventor of the present invention, it can be seen that there is almost no influence of the load water stored on the hot-rolled steel plate H.

First, before cooling the hot-rolled steel sheet H with the cooling device 14, the cooling capability (upper cooling capability) of the upper cooling device 14a and the cooling capability of the lower cooling device 14b Ability). The upper cooling capacity and the lower cooling capacity are set such that the heat transfer coefficient of the upper surface of the hot-rolled steel sheet H cooled by the upper cooling device 14a and the lower heat transfer coefficient of the lower surface of the hot-rolled steel sheet H cooled by the lower cooling device 14b .

Here, a calculation method of the heat transfer coefficient between 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 amount of heat of cooling (thermal energy) per unit time from the unit area by the temperature difference between the heat transfer medium and the heat medium (heat transfer coefficient = cooling calorific value / temperature difference). The temperature difference here is a difference between the temperature of the hot-rolled steel sheet H measured by the thermometer at the inlet side of the cooling device 14 and the temperature of the cooling water used in the cooling device 14. [

The cooling calorific value is a value obtained by multiplying the temperature difference of the hot-rolled steel sheet H by the specific heat and the mass, respectively (cooling calorific value = temperature difference x specific heat x mass). That is, the cooling calorific value is the cooling calorific value of the hot-rolled steel plate H in the cooling device 14, and the difference between the temperatures of the hot-rolled steel sheet H measured by the thermometer on the inlet side and the outlet side of the cooling device 14, The specific heat of the hot-rolled steel sheet H and the mass of the hot-rolled steel sheet H cooled by the cooling device 14, respectively.

The heat transfer coefficient of the hot-rolled steel sheet H calculated as described above is divided by the heat transfer coefficient of the upper and lower surfaces of the hot-rolled steel sheet H. The heat transfer coefficients of these upper and lower surfaces are calculated using, for example, the ratio previously obtained as follows.

That is, the heat transfer coefficient of the hot-rolled steel sheet H when the hot-rolled steel sheet H is cooled only by the upper-side cooling device 14a and the heat-transfer coefficient of the hot-rolled steel sheet H when the hot-

At this time, the cooling water from the upper cooling device 14a and the cooling water from the lower cooling device 14b are made equal. The reciprocal of the ratio of the heat transfer coefficient when the measured upper cooling device 14a is used and the heat transfer coefficient when the lower cooling device 14b is used is larger than the ratio of the upper and lower heat transfer coefficient ratios of the upper cooling device 14a And the cooling water amount from the lower cooling device 14b.

The upper and lower ratios of the cooling water thus obtained are multiplied by the cooling water from the upper cooling device 14a or the cooling water from the lower cooling device 14b at the time of cooling the hot-rolled steel sheet H, The ratio of the heat transfer coefficient between the upper surface and the lower surface.

In the above description, the heat transfer coefficient of the hot-rolled steel sheet H cooled by only the upper cooling device 14a and the lower cooling device 14b is used. However, the heat transfer coefficient of the hot-rolled steel sheet H cooled by both the upper cooling device 14a and the lower cooling device 14b The heat transfer coefficient of the steel sheet H may be used. That is, the heat transfer coefficient of the hot-rolled steel sheet H when the cooling water quantity of the upper cooling device 14a and the lower cooling device 14b is changed is measured, and the heat transfer coefficient of the upper and lower surfaces of the hot- The ratio of the coefficient may be calculated.

As described above, the heat transfer coefficient of the hot-rolled steel sheet H is calculated and the heat transfer coefficient of the upper and lower surfaces of the hot-rolled steel sheet H is calculated on the basis of the above-mentioned ratio (the upper and lower heat transfer coefficient ratios) of the heat transfer coefficients of the upper and lower surfaces of the hot- .

Here, in order to uniformly cool the hot-rolled steel sheet H, the cooling capacity of the upper cooling device 14a and the lower cooling device 14b is adjusted (the upper surface cooling heat generation amount of the hot-rolled steel plate H and the lower cooling heat generation amount are controlled) As a result of intensive studies by the present inventors, the following knowledge has newly been obtained.

The present inventors have made intensive investigations on the characteristics of the temperature standard deviation caused by cooling in the state where the wave shape of the hot-rolled steel sheet H is generated, and as a result, made the following clear.

The temperature measurement of the hot-rolled steel plate H in the passing plate is performed by the temperature gauge 40 and the measuring unit 41 at a measurement position determined in the rolling direction of the hot-rolled steel plate H (hereinafter, this measurement position may be referred to as a fixed point) And shape measurement are performed at a constant time interval (sampling interval) to obtain time-series data of the temperature measurement result and the shape measurement result.

The temperature measuring area by the thermometer 40 includes the entire width direction of the hot-rolled steel sheet H. The shape is a steepness obtained by the line integral of the height or the fluctuation component of the pitch of the wave by using the amount of movement of the hot-rolled steel plate H in the direction of the sheet in the heightwise variation of the hot- At the same time, the variation per unit time, that is, the variation speed is also obtained. The shape measurement area includes the entire width direction of the hot-rolled steel sheet H, similarly to the temperature measurement area. In addition, by multiplying the sampling time of each measurement result by the delivery speed (delivery speed) of the hot-rolled steel plate H, the position of the hot-rolled steel sheet H in which the measurement results are obtained can be calculated in the rolling direction. That is, when time series data of each measurement result is sampled, the time series data of each measurement result can be related to the position in the rolling direction.

Using this time series data, firstly, the sum of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet H is adjusted. Specifically, the sum of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel plate H is adjusted so that the time-series average value of the temperature measured by the thermometer 40 is equal to the predetermined target value.

When the sum of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount is adjusted, an error with the actual operating performance is corrected with respect to a theoretical value obtained in advance, for example, by using an experimental formula expressed by the formula of Mitsuzuka On / off control of the cooling header connected to the cooling device 14 may be performed on the basis of the learning value set to be set. Alternatively, on / off of the cooling header may be feedback-controlled or feed-forward-controlled based on the temperature measured by the thermometer 40 in practice.

Next, the cooling control of the conventional ROT will be described using the data obtained from the thermometer 40 and the mold surface 41 described above. Fig. 4 shows the relationship between the temperature fluctuation and the steepness of the hot-rolled steel sheet H in cooling the ROT of a typical strip in a normal operation. The vertical heat transfer coefficient ratio of the hot-rolled steel sheet H in Fig. 4 is 1.2: 1, and the upper cooling capacity is higher than the lower cooling capacity. The graph on the upper side of Fig. 4 shows the temperature fluctuation with respect to the distance from the tip of the coil or the elapsed time of the peak, and the lower graph in Fig. 4 shows the steepness with respect to the distance from the coil tip or the elapsed time.

The area A in Fig. 4 is a region (a region having a bad shape because there is no tension) before the leading end portion of the strip shown in Fig. 3 is engaged with the coiler of the winding device 15. Fig. The region B in Fig. 4 is a region (a region in which the wave shape is flatly changed by the influence of the unit tension) after the strip end portion is engaged with the coil. It is desired to improve a large temperature fluctuation (i.e., a temperature standard deviation) occurring in a region where the shape of the hot-rolled steel sheet H is not flat.

Therefore, the inventors of the present invention have conducted extensive experiments aiming at suppressing an increase in temperature standard deviation in the ROT, and as a result, the following knowledge has been obtained.

Fig. 5 shows the temperature fluctuation component for the same shape steepness in cooling in the ROT of a typical strip in normal operation as in Fig. This temperature fluctuation component is a residual value obtained by subtracting a time series average of temperature from the actual steel sheet temperature (hereinafter sometimes referred to as "average temperature"). For example, the average temperature may be an average of a range of one cycle or more of the wave shape of the hot-rolled steel sheet H.

Also, the average temperature is, in principle, the average of the range in the cycle unit. It is confirmed by the operation data that the average temperature in the range of one cycle does not have a large difference from the average temperature in the range of two or more cycles.

Therefore, it is sufficient to calculate the average temperature at least in the range of one cycle of the wave shape. The upper limit of the range of the wave shape of the hot-rolled steel sheet H is not particularly limited, but preferably an average temperature of sufficient accuracy can be obtained by setting it to five cycles. Even if the averaging range is not in the range of the cycle unit, an acceptable average temperature can be obtained if the range is 2 to 5 cycles.

Here, assuming that the upward direction in the vertical direction of the hot-rolled steel sheet H (the direction orthogonal to the upper and lower surfaces of the hot-rolled steel sheet H) is positive, in the region where the variation rate measured at the apex is positive, At least one of the direction in which the upper surface cooling heat generation amount decreases and the direction in which the lower surface cooling heat generation amount increases is determined as the control direction when the temperature of the hot-rolled steel sheet H (temperature measured at the apex) is lower than the average temperature When the temperature of the hot-rolled steel sheet H is high, at least one of the direction in which the amount of the upper surface cooling heat generation increases and the direction in which the lower surface cooling heat generation amount decreases is determined as the control direction.

When the temperature of the hot-rolled steel sheet H is low relative to the average temperature in the non-denominator region where the fluctuation speed measured at the apex is low, at least one of the direction in which the amount of surface- And when at least one of the direction in which the amount of the upper surface cooling heat generation decreases and the amount in which the lower surface cooling heat generation amount increases is determined as the control direction when the temperature of the hot-rolled steel plate H is higher than the above average temperature.

As shown in Fig. 6, if the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet H in the cooling section are adjusted based on the determined control direction as described above, It was found that the temperature fluctuation occurring in the region A where the shape of the steel sheet H is not flat can be reduced.

The case where the operation opposite to the above is performed will be described below. When the temperature of the hot-rolled steel sheet H is low relative to the average temperature of the hot-rolled steel sheet H in the region where the variation rate measured at the apex is constant, at least one of the direction in which the upper- And when at least one of the direction in which the amount of the upper surface cooling heat generation decreases and the amount in which the lower surface cooling heat generation amount increases is determined as the control direction when the temperature of the hot-rolled steel plate H is higher than the above average temperature.

When the temperature of the hot-rolled steel sheet H is low relative to the above-described average temperature, at least one of the direction in which the upper surface cooling heat generation amount is decreased and the direction in which the lower surface cooling heat generation amount is increased is set in the control direction And if the temperature of the hot-rolled steel sheet H is higher than the above-mentioned average temperature, at least one of the direction in which the upper surface cooling heat generation amount increases and the lower surface cooling heat generation amount decreases is determined as the control direction.

As shown in Fig. 7, as compared with Fig. 5, when at least one of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet H in the cooling section is adjusted based on the determined control direction as described above, It was found that the temperature fluctuation occurring in the region A where the shape of the steel sheet H is not flat expanded. It is not assumed that the cooling stop temperature can be changed even in the example described herein.

Using this relationship, it is clarified which cooling capacity of the upper cooling device 14a and the lower cooling device 14b of the cooling device 14 should be adjusted in order to reduce the temperature fluctuation, that is, the temperature standard deviation . Table 1 is a table summarizing the above relationships.

The hot-rolled steel sheet cooling apparatus of the present embodiment realizes the cooling method described above. That is, the average temperature calculation unit 51 of the control device 50 calculates the time series average value of the temperature measurement results obtained from the thermometer 40 in a time-series manner as the average temperature. The fluctuation speed calculating section 52 calculates the fluctuation speed of the hot-rolled steel sheet H based on the result of the shape measurement obtained in a time-wise manner from the form system 41. [

The control direction determining section 53 determines the upward direction in the vertical direction of the hot-rolled steel sheet H so that the hot-rolled steel sheet H is hot rolled with respect to an average temperature in the range of one cycle or more of the wave shape of the hot- At least one of the direction in which the amount of cooling of the upper surface is decreased and the direction in which the amount of heat in the lower surface of the lower surface is increased is determined as the control direction when the temperature of the hot- At least one of the direction in which the amount of the upper surface cooling heat generation increases and the direction in which the lower surface cooling heat generation amount decreases is determined as the control direction.

When the temperature of the hot-rolled steel sheet H is low relative to the average temperature in the region where the fluctuation speed measured at the apex is low, the control direction determining unit 53 determines that the direction in which the top- At least one of the directions is determined as the control direction, and when the temperature of the hot-rolled steel plate H is higher than the average temperature, at least one of the direction in which the upper surface cooling heat generation amount decreases and the lower surface cooling heat generation amount increases is set as the control direction .

The total amount of cooling heat adjustment value adjuster 54 adjusts the sum of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet H in the cooling section based on the determined control direction as described above.

In order to adjust the cooling capacity of the upper cooling unit 14a and the cooling capacity of the lower cooling unit 14b, for example, a cooling header connected to the cooling hole 31 of the upper cooling unit 14a and a cooling header 14b may be on / off-controlled, respectively. Alternatively, the cooling capability of each cooling header in the upper cooling device 14a and the lower cooling device 14b may be controlled. That is, at least one of the water density, pressure, and water temperature of the cooling water jetted from each of the cooling holes 31 may be adjusted.

The number of cooling heads (cooling ports 31) of the upper cooling device 14a and the lower cooling device 14b is adjusted so that the flow rate of the cooling water jetted from the upper cooling device 14a and the lower cooling device 14b The pressure may be adjusted. For example, when the cooling capacity of the upper cooling unit 14a before the adjustment of the number of cooling headers is higher than the cooling capacity of the lower cooling unit 14b, the number of cooling headers constituting the upper cooling unit 14a is adjusted .

Cooling water is sprayed from the upper cooling device 14a to the upper surface of the hot-rolled steel plate H and the cooling water is sprayed to the lower surface of the hot-rolled steel plate H from the lower cooling device 14b by the adjusted cooling capacity, And is uniformly cooled.

Thereafter, the hot-rolled steel sheet H cooled by the cooling device 14 is subjected to apex measurement at the same temperature and shape by the thermometer 40 and the contouring device 41, and measured as time-series data. The temperature measuring area includes the entire width direction of the hot-rolled steel sheet H. The shape indicates the amount of change in the height direction of the hot-rolled steel sheet H observed by the peak measurement. The measurement region of the shape includes the entire region in the width direction of the hot-rolled steel sheet H like the temperature measurement region. By multiplying these sampled times by the passing speed, it is possible to relate the time series data of the measurement results such as the temperature and the variation speed to the position in the rolling direction.

As described with reference to Figs. 4, 5, 6 and 7, when the temperature at the apex of the hot-rolled steel sheet H is low relative to the average temperature at the apex in the region where the fluctuation rate at the apex of the hot- , The temperature standard deviation can be reduced by decreasing the cooling capability of the upper side (the amount of cooling heat on the upper side). Likewise, by increasing the lower cooling ability (lower cooling heat generation amount), the temperature standard deviation can be reduced. Using this relationship makes it clear that the cooling capacity of the upper cooling device 14a and the lower cooling device 14b of the cooling device 14 should be adjusted in order to reduce the temperature standard deviation.

In other words, by grasping the fluctuating position of the temperature related to the wave shape of these hot-rolled steel sheets H, it is possible to identify which of the upper and lower cooling standard temperature deviations is occurring. Therefore, the increasing / decreasing direction (control direction) of the upper cooling ability (upper surface cooling heat generation amount) and the lower cooling ability (lower cooling heat generation amount) for decreasing the temperature standard deviation can be determined and the upper and lower heat transfer coefficient ratios can be adjusted.

Further, based on the magnitude of the temperature standard deviation, the upper and lower heat transfer coefficient ratios can be determined such that the temperature standard deviation falls within a permissible range, for example, within a range from a minimum value to a minimum value + 10 ° C. By making the temperature standard deviation fall within the range from the minimum value to within the minimum value + 10 占 폚, variations in yield stress, tensile strength, and the like can be suppressed within the manufacturing permissible range and the hot-rolled steel sheet H can be uniformly cooled . Although there is a considerable variation, if the cooling water density ratio is within ± 5% with respect to the cooling water density ratio at which the temperature standard deviation becomes the minimum value, the temperature standard deviation falls within the range from the minimum value to the minimum value + 10 ° C. That is, when the cooling water density is used, it is preferable to set the vertical ratio (cooling water density ratio) of the cooling water density to within ± 5% with respect to the cooling water density ratio at which the temperature standard deviation becomes the minimum value. However, this allowable range does not necessarily include the upper and lower densities.

According to the above embodiment, the cooling capacity of the upper cooling unit 14a and the lower cooling unit 14b is adjusted in advance to cool the hot-rolled steel sheet H, and furthermore, the temperature of the cooled hot- The cooling capacity of the upper cooling unit 14a and the cooling capacity of the lower cooling unit 14b are adjusted on the basis of the cooling capacity of the lower cooling unit 14a. Thus, the cooling capacity of the upper cooling unit 14a and the lower cooling unit 14b can be controlled by feedback control to qualitatively and quantitatively appropriate cooling capacity, which can further improve the uniformity of the hot-rolled steel sheet H cooled thereafter .

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 the shape of the hot-rolled steel sheet H are vertically measured at the same measurement position by the thermometer 40 and the shaping system 41. However, the inventors of the present invention have found that the thermometer 40, It is found that the measurement positions of the measurement points are not strictly the same. Specifically, as shown in Fig. 8, the positional deviation (distance) L of the temperature measurement point P1 of the thermometer 40 on the hot-rolled steel plate H and the shape measurement point P2 of the shape system 41 is 50 mm And more preferably 30 mm or less, the temperature and shape of the hot-rolled steel sheet H can be appropriately grasped.

8, the direction of the positional deviation L between the temperature gauge 40 and the measurement position of the mold surface 41 may be the direction of the plate of the hot-rolled steel plate H, the direction of the plate width of the hot-rolled steel plate H, to be. 8, the thermometer 40 is disposed on the upstream side of the mold surface 41. Alternatively, the mold surface 41 may be disposed on the upstream side of the thermometer 40. In this case,

Here, the reason why it is desirable to set the positional deviation L of the measurement points of the thermometer 40 and the shape measuring device 41 within 50 mm will be described. Table 2 shows the positional deviation L of the measurement points of the thermometer 40 and the mold surface 41 under the conditions of the upper and lower heat transfer coefficient ratios, the steepness degrees and the passing speeds when the present invention is applied to the actual machine (Standard deviation from the minimum value) from the temperature standard deviation of the hot-rolled steel sheet H and the difference between each temperature standard deviation and the minimum value (the minimum value in Table 2 = 10.0) when the temperature is varied in the range of -200 to +200 mm with respect to the rolling direction The difference between the two values is represented by the following expression.

In Table 2, the positional deviation L in the case where the shape measurement point P2 of the shape system 41 is set on the downstream side of the temperature measurement point P1 of the thermometer 40 is shown as a positive value, And the positional deviation L in the case where the shape measurement portion P2 of the shape system 41 is set on the upstream side is shown as a negative value. When the temperature measurement point P1 of the thermometer 40 and the shape measurement point P2 of the mold surface 41 are set the same, the positional deviation L becomes zero.

As shown in Table 2, if the positional deviation L of the measurement points of the thermometer 40 and the mold surface 41 is within 50 mm regardless of the unit, the difference in standard deviation from the minimum value is reduced to +10 DEG C or less You can see what you can do.

Therefore, when the positional deviation L of the measurement points of the thermometer 40 and the mold surface 41 is within 50 mm, the upper and lower cooling capacities for decreasing the temperature standard deviation and the lower cooling capacity Direction can be determined and feedback control of the cooling capacity of the upper cooling device 14a and the lower cooling device 14b can be performed.

In the above embodiment, as shown in Fig. 9, the cooling section in which the hot-rolled steel sheet H is cooled may be divided into a plurality of, for example, two divided cooling sections Z1 and Z2 in the rolling direction. A cooling device 14 is provided in each of the divided cooling sections Z1 and Z2. A thermometer 40 and a mold surface 41 are provided downstream of the boundaries of the divided cooling sections Z1 and Z2, that is, downstream 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 to this and can be set arbitrarily. For example, the cooling section may be divided into one to five divided cooling sections.

In this case, the temperature and the wave shape of the hot-rolled steel sheet H on the downstream side of the divided cooling sections Z1 and Z2 are measured by the respective thermometers 40 and the respective shape systems 41, respectively. Based on these measurement results, the cooling capability of the upper cooling unit 14a and the lower cooling unit 14b in each of the divided cooling zones Z1 and Z2 is controlled. At this time, the cooling ability is controlled so that the standard deviation of the temperature of the hot-rolled steel sheet H falls within the allowable range, for example, within the minimum value + 10 ° C from the minimum value as described above. Thereby, at least one of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet H in each of the divided cooling sections Z1 and Z2 is adjusted.

The cooling capacity of the upper cooling unit 14a and the cooling capacity of the lower cooling unit 14b is determined based on the measurement results of the thermometer 40 and the mold surface 41 on the downstream side of the divided cooling zone Z1, And at least one of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount is adjusted.

In the divided cooling section Z2, the cooling capacity of the upper cooling device 14a and the lower cooling device 14b is lower than the cooling capacity of the lower cooling device 14b based on the measurement results of the thermometer 40 and the mold- Forward control, or feedback control. In either case, at least one of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount is adjusted in the divided cooling section Z2.

The method of controlling the cooling capacity of the upper cooling device 14a and the lower cooling device 14b based on the measurement results of the thermometer 40 and the mold surface 41 is the same as the method Is the same as that of the above-described embodiment, and thus a detailed description thereof will be omitted.

In this case, since at least one of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet H is adjusted in each of the divided cooling sections Z1 and Z2, more precise control is possible. Therefore, the hot-rolled steel sheet H can be cooled more uniformly.

In the above embodiment, at least one of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet H is adjusted in each of the divided cooling sections Z1 and Z2, in addition to the measurement results of the thermometer 40 and the shape- At least one of the steepness of the wave shape of the hot-rolled steel sheet H and the passing speed of the hot-rolled steel sheet H may be used. For example, since the steepness or the sheet passing speed of the hot-rolled steel sheet H may not always be constant for each coil, the steepness or the passing speed is also considered.

For example, as shown in Fig. 10, when the degree of steepness of the wave shape of the hot-rolled steel sheet H becomes large, the temperature standard deviation of the hot-rolled steel sheet H becomes large. 11, the temperature standard deviation of the hot-rolled steel sheet H becomes large as the passing speed of the hot-rolled steel plate H becomes high.

If the steepness or the plate speed of the hot-rolled steel sheet H is not constant, the change in the temperature standard deviation with respect to the vertical heat transfer coefficient ratio can be evaluated qualitatively, but it can not be evaluated quantitatively accurately. Thus, for example, the temperature standard deviation according to the steepness or the conveying speed of the hot-rolled steel sheet H is obtained in advance, at least the steepness or the passing speed of the hot-rolled steel sheet H is measured, and the temperature standard deviation is corrected. Based on the corrected temperature standard deviation, the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet H in each of the divided cooling sections Z1 and Z2 are corrected. Thereby, the hot-rolled steel sheet H can be cooled more uniformly.

Further, according to the present embodiment, it is possible to finish the hot-rolled steel sheet H so as to have a uniform shape or a material in the panel width direction. Fig. 12 shows an example of a wave shape in which a different amplitude is generated in the plate width direction by the central portion extension. Thus, even when a temperature standard deviation occurs due to a wave shape having different amplitudes generated in the panel width direction, according to the above-described embodiment, the temperature standard deviation in the panel width direction can be reduced.

As a result of intensive studies by the present inventors, it has been found that the hot-rolled steel sheet H can be made more uniform by setting the passing speed of the hot-rolled steel sheet H within a range from 550 m / min or more to a mechanical limit speed or less.

It was found that the influence of the number of mounts on the hot-rolled steel sheet H remarkably decreased even if the cooling water was sprayed to the hot-rolled steel plate H by setting the passing speed of the hot-rolled steel plate H to 550 m / min or more. As a result, uneven cooling of the hot-rolled steel sheet H due to the number of mounts can be avoided.

13 schematically shows an example of the hot rolling equipment 2 in another embodiment. The hot rolling equipment 2 is a facility for rolling a continuously heated slab S between upper and lower rolls, thinning the slab S to a minimum of 1.2 mm, and winding it.

The hot rolling equipment 2 includes a heating furnace 111 for heating the slab S, a widthwise rolling mill 116 for rolling the slab S heated in the heating furnace 111 in the width direction, A roughing mill 113 for roughly rolling the slab S rolled up and down from the vertical direction to a predetermined thickness, a finish rolling mill 113 for continuous hot rolling to a predetermined thickness, A cooling device 114 for cooling the hot rolled steel sheet H subjected to the hot finish rolling by cooling water and a winding device 115 for winding the hot rolled steel sheet H cooled by the cooling device 114 into a coil shape.

In the heating furnace 111, a side burner, an axial flow burner, and a loop burner for heating the slab S by spraying a flame are disposed on the slab S that has been brought in from the outside through the entry port. The slabs S brought into the heating furnace 111 are uniformly heated by the loop burners in the crack zones formed in the final zone by successive heating in the respective heating zones formed in the respective zones, Heat treatment is performed so as to be able to be transported to the optimum temperature. When all of the heat treatment in the heating furnace 111 is completed, the slab S is conveyed out of the heating furnace 111 and is moved to the rolling step by the roughing mill 112.

In the rough rolling mill 112, the slab S conveyed from the heating furnace 111 passes through a clearance of a cylindrical rotary roll disposed over a plurality of stands. For example, the roughing mill 112 hot-rolls the slab S only by the work rolls 112a disposed at the top and bottom in the first stand.

Subsequently, the coarse bar having passed the work roll 112a is continuously and continuously rolled by a plurality of quadruple rolling mills 112b constituted by a work roll and a backup roll. As a result, at the end of the rough rolling process, the roughing is rolled to a thickness of about 30 to 60 mm, and is then conveyed to the finish rolling mill 113. The configuration of the rough rolling mill 112 is not limited to that described in this embodiment, and the number of rolls and the like can be arbitrarily set.

The finishing mill 113 finish-rolls the rough bar conveyed from the roughing mill 112 until its thickness becomes about several millimeters. These finishing rolling mills 113 pass the joining bar through the gap of the finish rolling roll 113a arranged in the upper and lower straight lines over 6 to 7 stands and gradually lower it. The hot-rolled steel sheet H which is finely rolled by the finishing rolling machine 113 is conveyed to the cooling device 114 by the conveying roll 132 (see Fig. 14). Further, the rolling mill having a pair of finish rolling rolls 113a arranged in the above-mentioned upper and lower straight lines is also called a so-called rolling stand.

A cooling device 142 (auxiliary cooling device) for performing interstand cooling (auxiliary cooling) during finish rolling is provided between the rolling rolls 113a arranged between 6 to 7 stands (that is, between rolling stands) Respectively. A detailed description of the configuration and the like of the cooling device 142 will be described later with reference to Fig. 13 shows a case where the cooling device 142 is disposed in two places in the finishing mill 113. The cooling device 142 may be provided between all the rolling rolls 113a, But may be a configuration in which only a part is installed.

The cooling device 114 is a device for cooling the hot-rolled steel sheet H conveyed from the finisher 113 by means of a laminar spray or a nozzle. As shown in Fig. 14, this cooling device 114 is provided with an upper cooling device 131 for ejecting cooling water from the upper cooling hole 131 to the upper surface of the hot-rolled steel sheet H moving on the conveying roll 132 of the run- And a lower cooling device 114b for spraying cooling water from the lower cooling hole 131 to the lower surface of the hot-rolled steel sheet H.

A plurality of cooling holes 131 are provided for each of the upper cooling device 114a and the lower cooling device 114b. Further, a cooling header (not shown) is connected to the cooling port 131. The cooling capacity of the upper cooling unit 114a and the lower cooling unit 114b is determined by the number of the cooling holes 131. [ In addition, the cooling device 114 may be constituted by at least one of upper and lower spiral lamina, pipe lamina, spray cooling, and the like.

When adjusting the cooling capacity of the upper cooling unit 114a and the cooling capacity of the lower cooling unit 114b in the cooling unit 114, for example, the cooling unit 114a is connected to the cooling unit 131 of the upper cooling unit 114a The cooling header connected to the cooling port 131 of the lower cooling device 114b may be controlled to be on / off, respectively. Alternatively, the operating parameters of the cooling headers in the upper cooling device 114a and the lower cooling device 114b may be controlled. That is, at least one of the water density, pressure, and water temperature of the cooling water sprayed from each of the cooling holes 131 may be adjusted. The number of cooling headers (cooling holes 131) of the upper cooling device 114a and the lower cooling device 114b is adjusted so that the flow rate of the cooling water jetted from the upper cooling device 114a and the lower cooling device 114b The pressure may be adjusted. For example, if the cooling capacity of the upper cooling unit 114a is higher than the cooling capacity of the lower cooling unit 114b before the adjustment of the number of cooling headers, It is desirable to adjust the number.

The winding device 115 winds the hot-rolled steel sheet H cooled by the cooling device 114 at a predetermined winding temperature, as shown in Fig. The hot-rolled steel sheet H wound in a coil shape by the winding device 115 is conveyed out of the hot rolling equipment 2.

When cooling of the hot-rolled steel sheet H in which the wave shape having the surface height (wave height) fluctuates in the rolling direction is performed in the cooling device 114 of the hot rolling apparatus 2 having the above-described configuration, The hot-rolled steel sheet H can be uniformly cooled by appropriately adjusting the water density, pressure, water temperature, etc. of the cooling water injected from the upper cooling device 114a and the cooling water injected from the lower cooling device 114b. However, especially when the conveying speed of the hot-rolled steel sheet H is slow, the time during which the hot-rolled steel sheet H is in contact with the conveying roll 132 or the apron 133 locally becomes long, and the conveying roll 132 and the apron 133 are likely to be cooled by contact heat generation, resulting in uneven cooling. The factors of the nonuniformity of the 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, there is a possibility that the bottom of the wave shape of the hot-rolled steel sheet H comes into contact with the transport roll 132 locally. Further, as shown in Fig. 15B, there is a case where an apron 133 is provided as a support for preventing the hot-rolled steel sheet H from sinking between the adjacent conveying rolls 132 along the rolling direction. In this case, there is a possibility that the bottom of the wave shape of the hot-rolled steel sheet H comes into contact with the transport roll 132 and the apron 133 locally. As described above, in the hot-rolled steel sheet H, the portion that locally contacts the transport roll 132 or the apron 133 is more likely to be cooled than the other portions by contact heat generation. As a result, the hot-rolled steel sheet H is cooled unevenly.

Particularly, when the passing speed of the hot-rolled steel sheet H is low, the time during which the hot-rolled steel sheet H is locally contacted with the conveying roll 132 or the apron 133 becomes long. As a result, as shown in Fig. 16A, the portion where the hot-rolled steel sheet H is locally contacted with the conveying roll 132 or the apron 133 (the portion surrounded by the dotted line in Fig. 16A) The hot-rolled steel sheet H is cooled unevenly.

On the other hand, if the passing speed of the hot-rolled steel sheet H is made high, the contact time becomes short. The hot rolled steel sheet H in the transferring plate is moved from these conveying rolls 132 and the apron 133 by the repulsion due to the contact between the hot rolled steel plate H and the conveying roll 132 or the apron 133 Floating state.

When the speed of the hot-rolled steel sheet H is increased, the hot-rolled steel sheet H is floated from the conveying roll 132 or the apron 133 by the repulsion due to the contact, Or the number of contact times of the apron 133 decreases, the temperature drop due to the contact becomes negligibly small.

Therefore, by increasing the passing speed, the contact heat generation can be suppressed, and the hot-rolled steel sheet H can be cooled more uniformly as shown in Fig. 16B. In addition to the above-described control of the upper and lower heating values, the inventors have found that the hot-rolled steel sheet H can be sufficiently uniformly cooled by setting the throughput rate to 550 m / min or more.

This knowledge is obtained for the cooling of the hot rolled steel sheet H in which the wave shape is formed, but the lowest point of the hot rolled steel sheet H is contacted with the conveying roll 132 or the apron 133 regardless of the height of the wave shape Therefore, it is effective to achieve uniform cooling by increasing the speed of the conveying plate regardless of the height of the wave shape.

If the passing speed of the hot-rolled steel sheet H is set to 550 m / min or more, the hot-rolled steel sheet H is floated from the conveying roll 132 or the apron 133, There is no mounting number on the hot-rolled steel sheet H as in the prior art. Therefore, the hot-rolled steel sheet H can be prevented from being unevenly cooled due to the number of mountings.

As described above, by setting the passing speed of the hot-rolled steel sheet H in the cooling section to 550 m / min or more, it is possible to cool the hot-rolled steel sheet H having the wave shape periodically fluctuating in the rolling direction more uniformly.

It is also possible that the passing speed of the hot-rolled steel sheet H is higher, but it is impossible to exceed the mechanical limit speed (for example, 1550 m / min). Therefore, the passing speed of the hot-rolled steel sheet H in the substantially cooling section is set within a range from 550 m / min or more to a mechanical limit speed or less. When the upper limit value of the conveying speed (working upper limit speed) is predetermined in actual operation, the conveying speed of the hot-rolled steel sheet H is changed from 550 m / min or more to a working upper limit speed (for example, 1200 m / min) And the like.

It is needless to say that the hot-rolled steel plate cooling apparatus described with reference to Fig. 3 is applied to the hot-rolling apparatus 2 to control the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot- Set within a range up to the limit speed or lower limit speed).

Further, in general, in the case of a hot-rolled steel sheet H having a large tensile strength (particularly, a so-called high-tensile steel sheet having a tensile strength TS of 800 MPa or more and an actual upper limit of 1,400 MPa) It is known that the heat generated during rolling in the hot rolling equipment 2 due to the high hardness of H is increased. Therefore, conventionally, the cooling speed of the hot-rolled steel sheet H in the cooling device 114 (that is, the cooling section) is suppressed to be low, thereby cooling sufficiently.

However, when the conveying speed of the hot-rolled steel sheet H in the cooling device 114 is reduced to a low level, when the hot-rolled steel sheet H is formed in a wave shape, the hot-rolled steel sheet H, the conveying roll 132, 133, the contact portion is easily cooled by contact heat generation, and uneven cooling is performed.

The inventors of the present invention have found that a pair of finish rolling rolls 113a (i.e., rolling stands) installed over 6 to 7 stands in the finishing mill 113 of the hot rolling mill 2 (So-called interstand cooling), it is possible to suppress the processing heat generation, and to set the passing speed of the hot-rolled steel sheet H in the cooling device 114 to 550 m / min or more. Hereinafter, the inter-stand cooling will be described with reference to Fig.

FIG. 17 is an explanatory diagram of a finish rolling mill 113 capable of cooling between stands. For the sake of explanation, a part of the finish rolling mill 113 is enlarged and shown for three rolling stands. In Fig. 17, the same elements as those in the above-described embodiment are denoted by the same reference numerals. 17, a plurality of (three in Fig. 17) rolling stands 140 provided with a pair of finish rolling rolls 113a arranged in the upper and lower straight lines are provided in the finish rolling mill 113 have. Between the rolling stands 140, there is provided a cooling device 142 that is a facility for cooling the nozzles by laminar or spraying, and between the rolling stands 140, the hot- It is possible to perform inter-cooling.

17, the cooling device 142 includes an upper cooling device 142a for ejecting cooling water from the upper side by a cooling hole 146 to the hot-rolled steel sheet H conveyed by the process rolling mill 113, And a lower cooling device 142b for ejecting cooling water from the lower side to the lower surface of the hot-rolled steel plate H. A plurality of cooling holes 146 are provided for each of the upper cooling device 142a and the lower cooling device 142b. Further, a cooling header (not shown) is connected to the cooling mouth 146. Further, the cooling device 142 may be constituted by at least one of upper and lower spiral lamina, pipe lamina, spray cooling and the like.

In the finishing mill 113 having the structure shown in Fig. 17, particularly when the tensile strength TS of the hot-rolled steel sheet H is 800 MPa or more, the inter-stand cooling is performed to suppress the heat generation of the hot- Thereby, it becomes possible to maintain the passing speed of the hot-rolled steel sheet H in the cooling device 114 at 550 m / min or more. Therefore, the contact portion is likely to be cooled by contact heat generation due to local contact between the hot-rolled steel sheet H and the conveying roll 132 or the apron 133, which has been a problem in the case of cooling at a conventional low- It is possible to cool the hot-rolled steel sheet H sufficiently uniformly.

In the above embodiment, it is preferable that cooling of the hot-rolled steel sheet H by the cooling device 114 is performed within a range of the temperature of the hot-rolled steel sheet H up to 600 ° C from the temperature of the exit side of the finishing mill. The temperature region where the temperature of the hot-rolled steel sheet H is 600 占 폚 or higher is the so-called film boiling region. That is, in this case, a so-called transition boiling region can be avoided and the hot-rolled steel sheet H can be cooled in the film boiling region. In the transition boiling region, when the cooling water is sprayed on the surface of the hot-rolled steel plate H, the portion covered by the vapor film and the portion directly sprayed with the cooling water on the hot-rolled steel sheet H coexist on the surface of the hot- As a result, the hot-rolled steel sheet H can not be uniformly cooled.

On the other hand, in the film boiling region, since the hot-rolled steel sheet H is cooled while the entire surface of the hot-rolled steel sheet H is covered with the vapor film, the hot-rolled steel sheet H can be uniformly cooled. Therefore, the hot-rolled steel sheet H can be cooled more uniformly when the temperature of the hot-rolled steel sheet H is in the range of 600 占 폚 or more as in the present embodiment.

While the preferred embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the above embodiments. Those skilled in the art will recognize that various changes and modifications within the spirit and scope of the appended claims will be apparent to those skilled in the art without departing from the technical scope of the invention.

Example

The inventor of the present invention conducted a cooling experiment of a hot-rolled steel sheet as an example in order to demonstrate that the hot-rolled steel sheet is uniformly cooled by setting the passing speed of the hot-rolled steel sheet at 550 m / min or more.

(Example 1)

For 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 steepness of 2% and a central portion of the corrugation formed thereon, cooling was performed by changing the passing speed in the cooling device. More specifically, the passing speed was changed to 400 m / min, 450 m / min, 500 m / min, 550 m / min, 600 m / min and 650 m / min, and cooling of the hot-

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 evaluation results of the calculated CT temperature fluctuation amount are shown in Table 3 below. As evaluation criteria, it was evaluated that the CT temperature fluctuation amount was not uniformly cooled when the CT temperature fluctuation amount was larger than 25 DEG C, and when the CT temperature fluctuation amount was 25 DEG C or less, it was evaluated as being uniformly cooled.

No cooling between stands in all conditions

Evaluation C: CT> 25 占 폚 B: 25? CT? 10 A: 10> CT

As shown in Table 3, when the passing speed is 500 m / min or less, the CT temperature fluctuation amount is not sufficiently reduced (higher than 25 deg. C) and uniform cooling of the hot-rolled steel sheet is not sufficiently performed. On the other hand, when the passing speed was 550 m / min or more, the CT temperature fluctuation amount was suppressed to 25 占 폚 or less, and it was found that the hot-rolled steel sheet was uniformly cooled. In particular, in the case where the passing speed is 600 m / min or more, since the CT temperature is suppressed to less than 10 ° C (8 ° C, 6 ° C), this condition is more preferable in realizing uniform cooling of the hot- .

(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 steepness level of 2% was hot-rolled so as to have a temperature of 880 캜 at the outlet side of the finish rolling. And cooling was performed by changing the speed. More specifically, the passing speeds of the hot-rolled steel sheets at the respective passing speeds were changed 20 times by changing the passing speeds to 400 m / min, 450 m / min, 500 m / min, 550 m / min, 600 m / min and 650 m / min.

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 the evaluation of the calculated CT temperature fluctuation amount are shown in Table 4 below. The evaluation criteria were the same as in the case of Example 1, and no interstand cooling was performed only when the throughput rate was 400 m / min.

And cooled to a stand temperature of 880 DEG C on the exit side after finish rolling.

Evaluation C: CT> 25 占 폚 B: 25? CT? 10 A: 10> CT

As shown in Table 4, when the passing speed is 500 m / min or less, even when interstand cooling is performed, the CT temperature fluctuation amount is not sufficiently reduced (higher than 25 DEG C) and uniform cooling of the hot- I did. On the other hand, when the passing speed was 550 m / min or more, the CT temperature fluctuation amount was suppressed to 25 占 폚 or less, and it was found that the hot-rolled steel sheet was uniformly cooled.

Further, in the case of cooling between the stands (that is, in the case shown in Table 4), the CT temperature fluctuation amount is suppressed also for the hot-rolled steel sheet having relatively high hardness (tensile strength 800 MPa). That is, it has been found that by uniformly cooling all the steels, particularly the steels having a high hardness, by performing the interstand between the steels by means of the finishing mill in addition to the passing speed of the hot- I could.

≪ Industrial applicability >

INDUSTRIAL APPLICABILITY The present invention is useful for cooling a hot rolled steel sheet which is hot-rolled by a finishing mill and has a wave shape whose surface height fluctuates in the rolling direction.

1, 2: Hot rolling equipment
11, 111: heating furnace
12, 112: rough rolling mill
12a, 112a: work roll
12b, 112b: a quadruple rolling mill
13, 113: Finishing mill
13a, 113a Finishing rolling roll
14, 114: cooling device
14a and 114a:
14b, 114b: Lower cooling device
15, 115: retractor
16, 116: width direction rolling mill
31, 131: cooling holes
32, 132: conveying roll
40: Thermometer
41:
50: Control device
51: average temperature calculation unit
52: Variable speed calculation unit
53: Control direction determination unit
54: Total amount of cooling heat adjustment unit
H: Hot-rolled steel plate
S: Slab
Z1, Z2: split cooling section

Claims (5)

A hot-rolled steel sheet cooling apparatus for cooling a hot-rolled steel sheet hot-rolled by a finishing mill in a cooling section provided on the path,
A thermometer for measuring the temperature of the hot-rolled steel sheet on the downstream side of the cooling section;
A shape measuring device for measuring the shape of the hot-rolled steel sheet on the downstream side of the cooling section;
An upper cooling device for cooling the upper surface of the hot-rolled steel sheet in the cooling section;
A lower cooling device for cooling the lower surface of the hot-rolled steel sheet in the cooling section;
And the upper cooling device and the lower cooling device are controlled 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- And a control device for controlling at least one of an upper surface cooling heat generation amount and a lower surface cooling heat generation amount of the cooling water,
The control device includes:
An average temperature calculation unit for calculating a time series average value of the temperature of the hot rolled steel sheet on the downstream side of the cooling zone as an average temperature based on the temperature measurement result;
A fluctuation speed calculating section for calculating a fluctuation speed of the hot rolled steel sheet on the downstream side of the cooling section based on the shape measurement result;
When the temperature of the hot-rolled steel sheet is lower than the average temperature in the range of one cycle or more of the wave shape of the hot-rolled steel sheet in the region where the fluctuation speed is constant, Wherein at least one of a direction in which the upper surface cooling heat generation amount is decreased and a direction in which the lower surface cooling heat generation amount is increased is determined as a control direction and when the temperature of the hot rolled steel sheet is higher than the average temperature, And a direction in which the cooling heat generation amount is reduced as described above is determined as the control direction,
When the temperature of the hot-rolled steel sheet is low with respect to the average temperature, at least one of a direction in which the upper surface cooling heat generation amount increases and a direction in which the lower surface cooling heat generation amount decreases is determined as the control direction A control direction determination section that determines at least one of a direction in which the upper surface cooling heat generation amount decreases and a direction in which the lower surface cooling heat generation amount increases as the control direction when the temperature of the hot rolled steel sheet is higher than the average temperature;
And a cooling heat value total value adjusting unit for adjusting a total value of the upper surface cooling heat generation amount and the lower surface cooling heat generation amount of the hot-rolled steel sheet in the cooling section based on the control direction determined by the control direction determination unit. Hot-rolled steel plate cooling apparatus. The method according to claim 1,
Wherein a positional deviation between a temperature measurement point of the thermometer and a shape measurement point of the form system on the hot-rolled steel sheet is within 50 mm. 3. The method according to claim 1 or 2,
And the passing speed of the hot-rolled steel sheet in the cooling section is set within a range of 550 m / min or more to 1550 m / min or less. The method of claim 3,
Wherein the hot-rolled steel sheet has a tensile strength of 800 MPa or more. The method of claim 3,
The finishing mill is composed of a plurality of rolling stands,
Further comprising an auxiliary cooling device for performing auxiliary cooling of the hot-rolled steel sheet between the adjacent rolling stands.

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