JP2002011502A - Method and device for manufacturing hot-rolled steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a hot-rolled steel sheet by which the temperature of the steel sheet at the outlet of a finishing mill is adjusted to the target temperature while avoiding the trouble in equipment at the outlet of the finishing mill, and a manufacturing device used therefor. SOLUTION: The whole in the width direction of a rough rolled stock is heated with a heating device installed between a roughing mill and the finishing mill and also water cooling is performed with at least one cooling device provided between stands of the finishing mill consisting of plural stands.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a slab manufactured by a continuous casting machine, which is heated in a heating furnace, rough-rolled by a rough rolling machine, and finish-rolled by a finishing rolling machine. The present invention relates to a method and an apparatus for producing a hot-rolled steel sheet, and a method and apparatus for producing a hot-rolled steel sheet so that the temperature of the steel sheet at the exit of the finishing mill can be set to a target temperature while avoiding equipment trouble at the exit of the finishing mill.

[0002]

2. Description of the Related Art As described above, a slab manufactured by a continuous casting machine is heated in a heating furnace as described above, and then roughly rolled by a rough rolling machine to form a roughly rolled material. From the rolling mill to the finishing mill, the sheet is transported by a transport table in a predetermined transport pattern, and is finally rolled by the finishing mill to finish to a predetermined thickness.

At this time, the target value of the temperature of the steel sheet at the outlet of the finishing mill is, for example, a lower limit of 830 ° C. due to the restriction of the mechanical properties of the steel sheet, and an upper limit from the viewpoint of preventing the roughening of the rolling roll of the finishing mill. When the value is 880 ° C., a temperature range of 830 ° C. to 880 ° C., for example, 860 ° C. is set.

[0004] In the conventional rolling method, the sheet thickness is thin (1.8 mm or less) and the sheet width is wide (1250 mm or more).
In a high-strength steel sheet (referred to as “thin high-tensile steel”), the target temperature at the finish rolling mill outlet is, for example, 83% lower than that of the low-carbon steel.
Since the temperature is as low as 0 ° C., there is a problem that the rolling load, that is, the rolling load and the rolling torque of the preceding stands such as the first stand and the second stand, which have a particularly high rolling reduction, are increased in the finish rolling mill. Also, from the viewpoint of ensuring the temperature at the exit of the finishing mill, when the rolling speed needs to be increased, there is a problem that the motor power increases from the intermediate stand to the subsequent stand of the finishing mill.

[0005] Further, the leading end of the steel sheet is generally rolled at a lower speed than the central part in the longitudinal direction of the steel sheet when passing through the finish rolling mill. The finishing mill is accelerated for the purpose of increasing the efficiency and increasing the exit temperature of the finishing mill, and thereafter is rolled at a high speed.
The steel sheet is decelerated from the time when the rear end portion has passed the first stand of the finishing mill, and after passing through the finishing mill, it is wound by a coiler.

[0006] As described above, particularly at the leading end and the trailing end of the steel sheet, since the rolling speed is low, the temperature drop due to the increase in the amount of heat removed from the steel sheet is so severe that the target temperature cannot be obtained. At the center of the steel sheet, there is a problem that it is difficult to control the steel sheet temperature in the longitudinal direction to a target value, for example, the finishing outlet temperature is higher than a target temperature due to high-speed rolling of the finishing mill.

[0007] Japanese Patent Application Laid-Open No. 10-156404 discloses that the rolling load and rolling power of each stand of a finishing mill are constantly measured, and the rolling load and rolling power are set on the entrance side of a rough rolling material heating apparatus so that the rolling load and the rolling power do not exceed the equipment limit value. A method of heating a steel plate by the heating device based on thermometer measurement values is shown.

Japanese Patent Application Laid-Open No. 9-225517 discloses a method in which a rough-rolled material is heated by a heating device so that the temperature of the rough-rolled material on the entrance side of the finishing mill is kept constant, and the rough-rolled material having a constant temperature in the longitudinal direction is heated. There has been proposed a method in which the steel sheet temperature at the outlet of the finishing mill is made constant by rolling at a constant speed by the finishing mill.

[0009]

In the method described in Japanese Patent Application Laid-Open No. H10-156404, since the heating device is located in front of the finishing mill, the values are measured after measuring the rolling load and the rolling power of the finishing mill. It turned out that it was close to the limit value of the equipment, and even when the steel sheet was heated, there was a portion that was already heated and supplied to the finishing mill. Therefore, when this portion passes through the finishing mill, the rolling load may exceed the equipment limit value and damage the equipment.

Further, when the target temperature of the steel sheet at the outlet of the finishing mill is high, such as low carbon steel, only heating is required. However, when the target temperature is low, such as high-tensile steel, the steel sheet is heated above the target temperature. There is also a problem in that it is heated and a predetermined mechanical property cannot be obtained.

The method described in Japanese Patent Application Laid-Open No. 9-225517 discloses a method in which, in order to make the rolling speed of a finishing mill constant, a thin steel plate having a very long elongation, such as a thin steel plate, has a leading end portion that is passed through. When rolling is performed over the entire length of the steel sheet at a low rolling speed similar to that at the time of rolling, there is a problem that rolling becomes inefficient and productivity is lowered.

The rough rolled material is heated from the front end and supplied to the finishing mill. While the front end is being heated, the rear end is air-cooled and the temperature is lowered. If the heating amount of the heating device is increased from the front end to the rear end in order to suppress this temperature drop, a very large heating amount may be required at the rear end, and power consumption may be reduced. There is a problem that the manufacturing cost increases due to the increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and an object of the present invention is to reduce the temperature of the steel sheet at the outlet of the finishing mill while avoiding equipment trouble in the finishing mill. It is an object of the present invention to provide a rolling method for adjusting the temperature and an apparatus used therefor.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and the gist thereof is as follows.

(1) In the method for producing a hot-rolled steel sheet according to the present invention, a continuous cast slab is rolled into a rough rolled material by a rough rolling machine, and then heated by a heating device over the entire width of the steel sheet. The finish rolling is performed while the steel plate is water-cooled by a cooling device provided between at least one of the stands of the finishing mill.

(2) In the method for producing a hot-rolled steel sheet according to the present invention, the heating device is configured to control the first stand and / or the second stand of the finish rolling mill based on the measured or calculated temperature of the rough rolled material on the entry side. The rough rolling material is heated so that the rolling load of the two stands is equal to or less than the limit value of the equipment, and the cooling device is preferably water-cooled so that the temperature of the steel sheet at the outlet of the finishing mill becomes a target value. .

(3) In the method for producing a hot-rolled steel sheet according to the present invention, the heating amount of the heating device and / or the cooling water amount of the cooling device
On the basis of the measured value of the temperature of the steel sheet at the outlet of the finishing mill and / or at least one of the stands of the finishing mill, the temperature of the steel sheet at the outlet of the finishing mill becomes the target value. It is desirable to control.

(4) In the method for producing a hot-rolled steel sheet according to the present invention, the cooling device is provided between the first stand and the second stand and / or between the second stand and the third stand of the finishing mill. Is desirable.

(5) The apparatus for manufacturing a hot-rolled steel sheet according to the present invention comprises: a rough rolling machine; a heating device for heating the rough rolled material rolled by the rough rolling machine over the entire width direction of the steel sheet; A finish rolling mill having a plurality of stands for rolling the roughed rolled material is a device sequentially arranged, comprising a cooling device between at least one stand between each stand constituting the finishing rolling mill, a heating device Having a function of heating the rough-rolled material based on a temperature measurement value or a calculated value of the temperature of the rough-rolled material on the upstream side of the heating device; It has a function of water-cooling the steel sheet based on the temperature measurement value of the rough rolled material and / or the steel sheet at the location.

(6) The method for producing a hot-rolled steel sheet according to the present invention comprises a roughing mill, a heating device for heating the rough rolled material rolled by the rough rolling machine over the entire width direction of the steel sheet, and a heating device for heating. A finishing mill having a plurality of stands for rolling the rough-rolled material, and disposed between at least one of the stands constituting the finishing mill, and water-cooling the steel sheet rolled by the finishing mill. A cooling device and a thermometer for measuring the temperature of the steel sheet between at least one of the outlets of the finishing mill and / or between the stands of the finishing mill;

Here, the present invention includes a descaler as the cooling device, and a case where another device is installed between each device of the present invention or before and after the device row of the present invention, and other processes. Needless to say, it includes the case where it is added.

The present invention is also effective in so-called endless rolling, in which the tail of the preceding material and the tip of the succeeding material are joined and continuously rolled at the entry side of the finishing mill.

[0023]

FIG. 1 is a schematic diagram showing an embodiment of a hot-rolled steel sheet manufacturing apparatus according to the present invention. Using FIG.
The content of the present invention will be described in detail for thin materials for which it is difficult to secure the exit temperature of the finishing mill.

As a thin material, the steel composition is C: 0.09%,
Si: 0.07%, Mn: 1.40%, plate thickness: 1.6m
m, high width steel plate of 1550mm width (thin and wide high tensile material)
The effect was verified by numerical simulation for the target.

In FIG. 1, reference numeral 1 denotes a rough rolling mill, which rolls a slab heated by a heating furnace (not shown) provided on the well into a rough rolled material. Reference numeral 2 denotes a finishing rolling mill, which is a tandem rolling mill having six stands, which are simultaneously rolled by the six stands. Reference numeral 3 denotes a run-out table, and 31 denotes a water-cooling device installed on the run-out table, and cools the finish-rolled steel sheet to a predetermined temperature. 4
Is a down coiler, which winds a finish-rolled steel sheet into a coil.

Reference numeral 5 denotes a heating device that raises the temperature of the rough rolled material to a predetermined temperature over the entire width direction of the sheet by a method such as induction heating, gas combustion heating, or electric heating. The gas combustion heating method has a problem that combustion efficiency is low, and the electric heating method has a problem that a flaw is easily generated. Therefore, an induction heating type combustion device is desirable. As the induction heating method, a solenoid coil heating method (axial magnetic flux heating) or a transverse heating method (transverse magnetic flux heating) can be used. In the solenoid coil heating method, an induction heating coil is formed into a solenoid (wire tube), a material to be heated is inserted into the coil, and the material to be heated is heated by the action of an alternating magnetic field generated in the solenoid coil. is there. On the other hand, in the transverse heating method, an induction heating coil with an iron core is arranged above and below a material to be heated, and the material to be heated is heated by the action of an alternating magnetic field generated in the coil core. Preferably, a solenoid coil heating method having high heating efficiency is used. The heating capacity of the induction heating method is determined by the size of the material to be heated and the heating conditions.
More than W is sufficient.

Numerals 6 and 6 denote cooling devices for water-cooling the steel sheet to a predetermined temperature over the entire width of the steel sheet (hereinafter simply referred to as cooling). In the present embodiment, between the first stand (F1 stand) and the second stand (F2 stand), and
Although the cooling devices 6 and 6 are provided between the fourth stand (F4 stand) and the fifth stand (F5 stand), the present invention is not limited to this mode, and the cooling devices 6 and 6 are provided between the stands constituting the finishing mill 2. Between at least one of the stands. Preferably, between the first stand and the second stand and / or between the second stand and the third stand, or between the first stand and the second stand and between the fourth stand and the fifth stand. It is. One cooling device may be provided between the stands, or a plurality of cooling devices may be provided. 7 is a rough rolled material, 8 is a steel plate.

Reference numeral 9 denotes a thermometer at the outlet of the rough rolling mill, and 10 denotes a measuring roll for measuring the length of the rough rolled material. Reference numeral 11 denotes a finish rolling mill outlet thermometer installed at the outlet of the finishing rolling mill, and 12 denotes a finishing stand thermometer installed between stands of the finishing rolling mill (for example, installed between the third stand and the fourth stand). ), 13 is a heating / cooling setting device, and 14 is a temperature control device. In the present embodiment, the thermometer 12 between the finishing stands is provided between the third stand and the fourth stand. However, the present invention is not limited to this embodiment. Between at least one of the stands. Further, in the present embodiment, the finish rolling mill thermometer and the inter-stand thermometer are provided, but the present invention is not limited to this embodiment, and either one may be used.

The present invention is characterized in that the rough rolled material is heated over the entire width of the sheet so that the rolling load is equal to or less than the limit value of the equipment. Rolling load means rolling load, rolling torque, and rolling power. The rolling load affects the strength of the stand, and the rolling torque and the rolling power are important factors in determining the capacity of the motor that drives the roll used for rolling. These rolling loads are determined by the deformation resistance, sheet thickness, sheet width, rolling reduction, and the like of the steel sheet.

The limit value of the equipment is selected from the minimum value from the allowable value of the stand load that can withstand the rolling load, the allowable value of the motor torque and the motor power for generating the rolling torque and the rolling power, and the like. Is the value determined by For example, the equipment limit of the rolling load is set between 80% and 100% of the withstand load value in consideration of a sudden load change. In addition, although the equipment limit of the motor torque and the motor power is different depending on the characteristics of the motor, usually, a value for overload of 150 to 175% is set under a continuous load state time constraint (for example, 1 minute). You.

Next, the effects of the present invention, ie, the effect of reducing the load on the front stand of the finishing mill and the effect of making the exit temperature of the finishing mill, that is, the uniformity of the finishing exit temperature, will be described. Since the target steel sheet is a thin steel sheet and the elongation is about 2000 m, it is not possible to perform the rolling at a constant rolling speed of the finishing mill, so the finish rolling speed pattern as shown in FIG. The case of accelerated rolling was verified.

Table 1 shows the rolling schedule. In Table 1, the plate thickness of each stand is a value at the exit of each stand.

[0033]

[Table 1]

The other rolling conditions are as follows. [Rolling conditions] Slab extraction temperature from heating furnace: 1250 ° C Coarse-rolled material temperature at outlet of coarse-rolling machine: 1100 ° C Finish rolling speed: Threading at tip: 650 m / mim, Maximum speed: 1050 m / min Coarse-rolled material Heating amount by heating device: 50 ° C. Sheet width: 1500 mm In the case of the method not using the rough-rolled material heating device (Case 1), in the case of the method described in JP-A-9-225517 using only the rough-rolled material heating device ( Simulations were performed for Case 2) and a method (Case 3) using the rough rolled material heating device of the present invention and a cooling device installed between the first stand and the second stand of the finishing mill.

Of the results of the rolling simulation, the results for the rear end portion where the rolling load is high and the steel sheet temperature is low are particularly important. FIG. 3 shows the temperature drop at the rear end of the steel sheet from the exit of the rough rolling mill to the exit of the finishing mill.
The simulation results by two methods are shown.

FIG. 4 shows a simulation result of the rolling load at the rear end of the steel sheet in the case of rolling by the above three methods. For these reasons, in Case 1, the target temperature cannot be achieved at the finish rolling mill outlet because the temperature of the steel sheet is too low. In Case 2, the temperature of the rough-rolled material was excessively increased due to heating, and exceeded the target temperature. This is because, as described later, the steel sheet was heated so that the rolling temperature of the steel sheet was increased in order to reduce the rolling load of the former stand of the finishing mill.

The case of the present invention in Case 3 is the same as in Case 2 in that the rough rolled material is heated, but the steel sheet is cooled between the first stand and the second stand to control the temperature to the target temperature. be able to.

Next, the rolling load of the former stand will be described. In Case 1, the rolling load increases because the deformation resistance of the steel sheet increases due to the temperature drop, and as a result, the rolling load exceeds the equipment limit value. Case 2 and
In Case 3, since the rough rolled material is heated, the deformation resistance of the steel sheet is reduced, and as a result, the rolling load is also reduced and does not exceed the equipment limit value.

As described above, according to the present invention, the rolling load of the former stand of the finishing mill is reduced by heating the rough rolled material. In order to prevent the outlet temperature from exceeding the target value, cool at the front stage of the finishing mill,
The steel sheet temperature is adjusted to the target value.

In this simulation, the cooling device is provided between the first stand and the second stand. However, the cooling device may be provided between at least one of the stands of the finishing mill. However, for example, when rolling a steel sheet having a small thickness, cooling between the subsequent stands where the sheet thickness is small increases the rolling load, and the shape of the steel sheet may be disturbed. desirable. Further, when rolling a steel plate having a large thickness, it is desirable to cool the steel plate between the subsequent stands where the thickness is reduced.

Next, a description will be given of a method of controlling the outlet temperature of the finishing mill with higher accuracy in the practice of the present invention. First, the temperature fluctuation in the longitudinal direction of the rough rolled material is measured at the outlet of the rough rolling mill, and the temperature at each position of the coarse rolled material in the longitudinal direction is set as an initial value, and from the rough rolling mill outlet at each position to the finish rolling mill outlet. Is calculated based on the speed pattern of the transfer table and the speed pattern of the finishing mill (see FIG. 2), and the heating pattern of the heating device is determined such that the calculated outlet temperature of the finishing mill reaches the target temperature. And heat the rough rolled material.

Further, cooling is performed by the cooling device so that the outlet temperature of the finishing mill becomes a target value. At this time, there may be a case where an error occurs in the steel sheet temperature from the target value due to the temperature calculation error described above. Accordingly, the temperature of the steel sheet is measured with a thermometer between the exit of the finishing mill and / or the stand of the finishing mill, and the cooling water amount of the cooling device is corrected in accordance with an error between the measured value and the target value, so that the temperature control accuracy is improved. Improve. If this modification of the cooling control alone is not enough, the rolling load of the preceding stand of the finishing mill must be within the equipment limit,
The accuracy of temperature control is improved by correcting the amount of temperature rise of the heating device.

FIG. 5 is a flowchart showing the procedure for determining the amount of temperature rise of the heating device and the amount of cooling water of the cooling device. This will be described in more detail with reference to FIG. S1: As the material information and rolling information of the steel sheet, the thickness, width, target temperature, rolling speed pattern, and the like of the rough-rolled material and the product are set by the heating-cooling setting device 13 (FIG.
Refer to).

S2: Initial values of the amount of temperature rise of the heating device 5 (see FIG. 1) and the amount of cooling water of each of the cooling devices 6 and 6 (see FIG. 1) are set. S3: Based on the rolling speed pattern of the finish rolling mill, using the rough rolling mill outlet temperature measured in a form corresponding to each sampling point over the entire length in the longitudinal direction of the rough rolling material as an initial temperature,
Calculate the temperature drop from the rough rolling mill outlet to the finishing rolling mill outlet at each sampling point based on equation (1), and subtract this from the rough rolling mill outlet temperature to calculate each stand outlet temperature of the finishing mill. I do.

S4: Based on the calculation result of the outlet temperature of each stand of the finishing mill, the rolling load of each stand is calculated by using equation (2). S5: Check whether the rolling load of the finishing mill is within the equipment limit value.

S6: If the temperature exceeds the equipment limit value, the heating amount of the heating device is further increased, and the heating amount is corrected so as to be within the equipment limit. S7: If the temperature does not exceed the equipment limit value, it is confirmed whether or not the finish rolling mill outlet temperature has reached the target value.

S8: If the outlet temperature of the finishing mill is higher than the target value, the cooling water amount of the cooling device is increased, and the cooling water amount is corrected so that the outlet temperature of the finishing mill becomes the target value. If it is lower than the target value, the cooling water amount is reduced, and the cooling water amount is corrected so that the finish rolling mill outlet temperature becomes the target value.

S9: The heating amount and the cooling water amount for each sampling point are set and controlled in the heating device and the cooling device, respectively.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
The target material is a high-strength steel plate (thin high-tensile steel) having the same steel composition and dimensions as those described above.

The slab having a thickness of 250 mm heated by a heating furnace (not shown) located upstream of the rough rolling machine is rolled by the rough rolling machine 1 to a rough rolled material 7 having a thickness of 30 mm, which is an intermediate product. At the stage of the rough rolling, the temperature of the rough rolled material is measured by the rough thermometer outlet thermometer. The measured temperature of the rough rolled material is sampled by a sampling device at a constant pitch in the longitudinal direction of the bar in a form corresponding to each sampling point. From the time when the rough rolled material 7 reaches the measuring roll 10 installed immediately before the heating device 5, the timing at which each sampling point of the rough rolled material reaches the heating device 5 and the cooling devices 6, 6 is sequentially tracked. The timing at which each sampling point arrives immediately below the heating device 5 and the cooling devices 6, 6 is calculated. At the timing when each sampling point of the rough rolled material arrives immediately below the heating device 5 and the cooling devices 6, 6, the heating device 5 performs heating based on the amount of temperature increase calculated by the heating / cooling setting device 13 and performs cooling. Apparatus 6, 6
Performs cooling based on the cooling amount calculated in the same manner.

The heating / cooling setting device 13 monitors the outlet temperature of the rough rolling mill at each sampling point sent from the tracking device (measuring roll) 10 and a rolling line general computer (not shown). Material information to be sent, rolling information, etc.) and the transfer table speed pattern between the rough rolling mill and the finishing rolling mill sent from the finishing rolling mill, based on the speed pattern of the finishing rolling mill, the rough rolling mill outlet temperature as an initial value The temperature at the finish rolling mill outlet is predicted based on the following equation (1).

[0052]

(Equation 1)

Here, T is the steel sheet temperature, T0 is the initial temperature of the steel sheet, ΔT is the temperature drop of the steel sheet, ΔTw is the temperature drop by water cooling, ΔTa is the temperature drop by air cooling, and ΔTr is the roll contact. Is the temperature drop due to Also, tw, ta, t
m is the time required for water cooling, air cooling, and rolling, respectively, and is determined from the speed pattern of the rolling mill and the transfer table. Tw is the temperature of the cooling water, Ta is the temperature of the air, Tr is the surface temperature of the roll, and hw, ha, and hr are water cooling, air cooling, respectively.
Heat transfer coefficient due to roll contact. C, ρ, and H represent the specific heat, density, and thickness of the steel sheet, respectively.

The rolling load is calculated based on the calculated value of the temperature, based on the following rolling load calculation formula (2).

[0055]

(Equation 2)

Here, P is the rolling load, b is the sheet width, Kmf is the average deformation resistance, R 'is the flat roll radius, H is the inlet sheet thickness,
h is the outlet plate thickness, and Qp is the rolling force function. Based on the calculated temperature value and the rolling load, the heating amount and the cooling amount of the heating device 5 and the cooling device 6 are set in accordance with the calculation flow shown in FIG.

First, it is confirmed whether the rolling load of the first stand (here, the first and second stands) of the finishing mill is within the equipment limit value based on the above-mentioned calculated temperature value and the rolling load. If so, the heating amount of the heating device is further increased and the heating amount of the heating device is set so as to be within the equipment limit value.

In the above method, the temperature at the outlet of the finishing mill is predicted on the basis of the temperature measured by the thermometer on the exit side of the rough rolling mill. However, the present invention is not limited to this method. The temperature at the outlet of the mill is calculated by calculation, and the temperature at the outlet of the finishing mill can be calculated from the calculated temperature in the same manner as in the equation (1). The calculated temperature at the outlet of this rough rolling mill is:
Temperature control points are provided as sampling points in the longitudinal direction of the slab at the time of heating furnace extraction, for each temperature control point,
Calculate the temperature drop from the heating furnace extraction to the rough rolling mill outlet,
It can be obtained from the calculated temperature drop and the slab temperature at the time of heating furnace extraction.

Next, the temperature is further calculated based on the temperature increase, and it is confirmed whether or not the finishing outlet temperature reaches a target value. If the finishing outlet temperature is higher than the target value, increase the amount of water in the cooling device, and if it is lower than the target value, decrease the amount of water in the cooling device to repeatedly calculate until the finishing outlet temperature reaches the target value. And set the amount of water in the cooling device. By rolling the steel sheet in this way, it is possible to perform rolling so that the finishing outlet temperature of the steel sheet can be stably set at the target temperature without operating the finishing mill at or above its capacity.

However, since the above setting calculation is a prediction control based on a calculation model, an error in the prediction model may occur. In this case, the target temperature cannot be controlled at the finish rolling mill outlet.

Therefore, while the steel sheet is being rolled based on the above set values, the temperature of the steel sheet is measured every moment by the finishing outlet thermometer 11 and / or the thermometer 12 between the finishing stands, and the temperature deviation from the target value (measured value) The target value) is calculated, and when the temperature deviation is positive, the water amount of the cooling device is increased, and when the temperature deviation is negative, the water amount of the cooling device is decreased so that the finishing outlet temperature becomes the target value so that the finishing outlet temperature becomes the target value. Is controlled by. However, when the temperature cannot be controlled only by the cooling device, that is, when the finishing outlet temperature falls below the target value and the amount of water rise in the cooling device is insufficient, the temperature rise amount of the heating device is reduced. Control the temperature of the steel sheet by increasing it.

That is, in the temperature control method using the finish-rolling mill outlet thermometer 11, when the finish-rolled steel sheet 8 reaches the finish-rolling mill outlet thermometer 11, the temperature of the steel sheet is measured, and the measured temperature and the target value are measured. Is calculated (measured value−target value), and when the temperature deviation is positive, the cooling devices 6 and 6 are set based on the temperature deviation so as to lower the steel sheet temperature.
It is possible to control the temperature at the outlet of the finishing mill to a target value by calculating the amount of change in the amount of water by the temperature control device 14 and changing the amount of water in the cooling devices 6, 6 based on the amount of change in the amount of water obtained by the calculation. it can.

On the other hand, when the temperature deviation is negative, the temperature controller 14 calculates the amount of change in the heating amount of the heating device 5 based on the temperature deviation so as to increase the temperature of the steel sheet. By changing the heating amount of the heating device 5 based on the changed amount, the temperature at the outlet of the finishing mill can be controlled to the target value. This control is performed from the time when the leading end of the steel sheet 8 reaches the thermometer at the exit of the finishing mill until the steel sheet 8 passes through the cooling device.

In the temperature control method using the thermometer between finishing stands 12 (installed between the third stand and the fourth stand), the temperature is controlled every time the temperature control point reaches directly below the thermometer between finishing stands 12. Measured temperature deviation from preset 3rd station exit temperature (set value) (measured value-set value)
When the temperature deviation is positive, the amount of change in the water amount of the cooling device 6 (also referred to as a downstream cooling device) provided downstream of the thermometer 12 between the finishing stands is set to the temperature so that the temperature deviation becomes zero. It is provided upstream of the thermometer 12 between the finishing stands by the feed-forward control which calculates the control device 14 and adjusts the water amount of the downstream cooling device 6 based on the water amount change amount or so that the temperature deviation becomes zero. The amount of change in the amount of water in the cooling device 6 (also referred to as the upstream cooling device) is calculated by the temperature control device 14, and the temperature at the outlet of the finishing mill is adjusted by feedback control in which the amount of water in the upstream cooling device 6 is adjusted based on the amount of change in water. It can also be controlled to the target value.

On the other hand, when the temperature deviation (measured value−set value) between the temperature measured by the thermometer 12 between the finishing stands and the set temperature of the outlet of the third stand is minus, the temperature is increased so as to increase the steel plate temperature. The temperature controller 14 calculates a change in the amount of temperature rise of the heating device 5 based on the deviation, and changes the amount of change in the temperature of the heater 5 based on the change in temperature obtained by the calculation. The temperature can be feedback-controlled to the target value. The set value of the outlet temperature of the third stand is the third set value obtained when calculating the heating amount of the heating device.
Although the calculated value of the stand exit temperature can be used, the set value may be determined from the viewpoint of mechanical characteristics.

Instead of the above-mentioned rolling load, a rolling torque or a rolling power may be used as a criterion as a rolling load. Also, two or more of the rolling load, rolling torque and rolling power may be used as the criteria.

In a rolling mill in which a descaler is installed between stands of a finishing mill, it goes without saying that a descaler may be used instead of the cooling device.

FIG. 6 shows the finishing outlet when the temperature control is performed by correcting the setting values of the cooling device and / or the heating device based on the actually measured values of the finishing outlet thermometer and / or the thermometer between the finishing stands. It is a simulation result which shows transition of temperature.

FIG. 7 is a simulation result showing the transition of the finishing outlet temperature when only heating is performed based on the method described in JP-A-10-15464. Thus, in the case of the present invention, the finishing outlet temperature can be controlled to the target temperature, but in the case of the method of performing only heating, the finishing outlet temperature is deviated higher than the target temperature due to a prediction model error. It is clear that.

[0070]

According to the method and the manufacturing apparatus of the present invention,
By setting the rolling load in the finish rolling mill within the limit value of the equipment, it is possible to control the steel sheet temperature at the finish rolling mill outlet to the target temperature while avoiding equipment trouble at the finish rolling mill outlet.

Therefore, the present invention greatly contributes to a reduction in operating costs and an improvement in hot-rolled steel sheet quality. Further, the temperature of the steel sheet is measured by a thermometer between the finishing outlet and / or the finishing stand, and the cooling water amount of the cooling device is corrected according to an error between the measured value and the target value, thereby further improving the temperature control accuracy. Thus, a greater effect of the present invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a hot-rolled steel sheet manufacturing apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a rolling speed pattern of a finishing mill.

FIG. 3 is a diagram showing a simulation result of a temperature drop at a rear end portion of a steel sheet from a rough rolling mill outlet to a finishing rolling mill outlet.

FIG. 4 is a diagram showing a simulation result of a rolling load at a rear end portion of a steel plate.

FIG. 5 is a diagram showing a calculation flow for setting a heating amount and a cooling amount of a heating device and a cooling device, respectively.

FIG. 6 is a simulation result showing the transition of the finishing outlet temperature when the setting value of the cooling device and / or the heating device is corrected and controlled based on the actual measurement value of the finishing outlet thermometer and / or the thermometer between the finishing stands. .

FIG. 7 is a simulation result showing the transition of the finishing outlet temperature when only heating is performed based on the method described in JP-A-10-15464.

[Explanation of symbols]

 1. Rough rolling mill 2. Finishing mill 3 Runout table 31. 3. Water cooling device installed on the run-out table Down coiler 5. Heating device 6. Cooling device 7. Rough rolled material 8. Steel plate 9. Rough mill outlet thermometer 10. Measuring roll 11. Finishing mill outlet thermometer 12. 12. Thermometer between stands of finishing mill Heating / cooling setting device 14. Temperature control device

Claims (6)

[Claims] 1. A continuous cast slab is rolled into a rough rolled material by a rough rolling machine, and then heated by a heating device over the entire width of the plate, and at least one of the stands of a finishing mill comprising a plurality of stands is provided. A method for producing a hot-rolled steel sheet, wherein the steel sheet is finish-rolled while being cooled by water using a cooling device provided between one stand. 2. The heating device, based on a temperature measurement value or a temperature calculation value of the rough rolled material at an entrance side of the heating device,
The rough rolling material is heated so that the rolling load of the first stand and / or the second stand of the finishing mill is equal to or less than the limit value of the equipment, and the cooling device controls the temperature of the steel sheet at the outlet of the finishing mill to a target value. The method for producing a hot-rolled steel sheet according to claim 1, wherein the steel sheet is water-cooled so as to satisfy the following condition. 3. The steel plate between at least one of the outlets of the finishing mill and / or between the stands of the finishing mill, wherein the amount of temperature rise of the heating device and / or the amount of cooling water of the cooling device is adjusted. The method for producing a hot-rolled steel sheet according to claim 1, wherein the temperature of the steel sheet at the outlet of the finishing mill is controlled to be a target value based on the measured value of the temperature. 4. The cooling device according to claim 1, wherein the cooling device is provided between a first stand and a second stand of the finishing mill and / or between a second stand and a third stand. The method for producing a hot-rolled steel sheet according to any one of the above. 5. A rough rolling machine, a heating device for heating the rough rolled material rolled by the rough rolling machine over the entire width direction of the sheet, and a plurality of stands for rolling the rough rolled material heated by the heating device. A finishing mill having a cooling device between at least one of the stands that constitute the finishing mill, wherein the heating device is an upstream side of the heating device. Having a function of heating the rough-rolled material based on a measured temperature value or a calculated temperature value of the rough-rolled material, wherein the cooling device includes a rough-rolled material at at least one position between an entrance side, an exit side, and a stand of a finishing mill. And / or a function of water-cooling the steel sheet based on the measured temperature value of the steel sheet. 6. A rough rolling machine, a heating device for heating the rough rolled material rolled by the rough rolling machine over the entire width direction of the sheet, and a plurality of stands for rolling the rough rolled material heated by the heating device. Finishing mill, a cooling device arranged between at least one of the stands constituting the finishing mill, and a water cooling device for the steel sheet rolled by the finishing mill, and the finishing mill And / or a thermometer for measuring the temperature of the steel sheet between at least one of the stands of the finishing mill.