JPH0763750B2 - Cooling control device for hot rolled steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention is characterized in that, when cooling a hot-rolled steel sheet by blowing cooling water from both the upper surface and the lower surface, the steel sheet causes a defective shape. So that the desired material is obtained,
The present invention relates to a cooling control device for hot-rolled steel sheets that optimally controls the amount of cooling water injected from both sides.

(Problems to be Solved by the Related Art and Invention) In recent years, a controlled cooling that gives a quenching effect by rapidly cooling (accelerated cooling) a high temperature steel sheet immediately after hot rolling by water cooling to give the steel sheet high strength characteristics A steel plate manufacturing apparatus equipped with a process called is operating.

With this steel plate manufacturing apparatus, it becomes possible to manufacture a steel plate having excellent use performance by performing controlled cooling immediately after rolling.

However, in such a conventional steel plate manufacturing apparatus, due to an imbalance of cooling from the upper and lower surfaces of the steel plate during accelerated cooling, a warp shape defect in the plate width direction is more likely to occur than that in the conventional air cooling. There is a drawback that. The occurrence of this shape defect is due to the difference in cooling rate due to the difference in behavior of the cooling water sprayed from the upper surface and the lower surface of the steel sheet.
When the upper and lower surfaces of the steel sheet are cooled at different cooling rates in this way, asymmetric internal stress is generated in the sheet thickness direction, which deteriorates the shape of the product.

In order to prevent the occurrence of such a shape defect, conventionally, the temperature of the steel plate upper and lower surfaces during water cooling is measured, and the steel plate deformation amount is predicted from the temperature difference. There is a technology to control the amount of water injection. This method, when the cooling conditions are the same, namely, the plate size, the cooling start temperature,
The effect is predicted when the cooling end temperature and the cooling water amount are constant, but cannot be said to be effective when they are different.

However, no method for controlling the amount of water injection is posted, and the influence on the cooling end temperature when changing the amount of water injection to the upper and lower surfaces is not considered.

The present invention has been made in view of such conventional problems, and a function of controlling the amount of cooling water injected from the upper and lower surfaces so that the warp amount of the hot steel sheet during and after water cooling is minimized. An object of the present invention is to provide a cooling control device for hot-rolled steel sheet having a certain temperature.

(Means for Solving the Problem) The present invention for achieving the above-mentioned object is a finishing rolling mill that rolls a hot steel sheet to a predetermined plate thickness, and is arranged in a post-process of the finishing rolling mill and conveyed. A steel plate on which a cooling device that cools while transporting the hot steel plate by injecting cooling water from a plurality of nozzles arranged in the width direction of the hot steel plate from both directions of the hot steel plate with respect to the hot steel plate In the manufacturing apparatus, a plurality of pairs of temperature detecting means for detecting the temperature of the upper and lower surfaces of the hot steel sheet conveyed in the cooling device, and a warp amount detecting means for detecting the warp amount of the hot steel sheet after being cooled by the cooling device. A first calculation means for obtaining a relationship between the amount of cooling water sprayed from nozzles arranged on the upper and lower surfaces of the cooling device and the heat transfer coefficient of the hot steel plate based on various physical property values of the hot steel plate given in advance. Detected by the temperature detection means From the relationship between the actual temperature of the hot steel sheet at the inlet of the cooling device and the amount of cooling water obtained by the first computing means and the heat transfer coefficient of the hot steel sheet, the temperature distributions during cooling of the upper and lower surfaces of the hot steel sheet are respectively calculated. The temperature distribution calculating means independently calculated, and the temperature distribution of the upper and lower surfaces of the hot steel sheet calculated by the temperature distribution calculating means are obtained from the actual temperature of the upper and lower hot steel sheets in water cooling detected by the temperature detecting means. The correction value calculating means for calculating the correction value of the heat transfer coefficient of the hot steel plate to match the temperature distribution, and the relationship between the heat transfer coefficient of the hot steel plate and the cooling water amount obtained by the first calculating means, The stress inside the hot steel plate is corrected by the correction value calculated by the correction calculating means, and from the temperature distribution in the plate thickness direction obtained based on the relationship between the heat transfer coefficient and the cooling water amount of the hot steel plate after the correction. And a warp amount calculating means for calculating the warp amount of the hot steel sheet after being cooled by the cooling device based on the stress strain calculated by the stress strain calculating device, and the warp amount calculating device. Comparing the amount of warp of the hot steel plate calculated by means and the actual amount of warp of the hot steel plate detected by the amount of warp detection means, of the stress strain calculated by the stress strain calculation means based on the comparison result. By the correction value calculating means for calculating the correction value and the correction value obtained by the stress-strain property value calculating means, the amount of warpage of the plate obtained from the stress-strain value obtained by the corrected stress-strain calculating means is minimized. In addition, it has a cooling water amount control means for controlling the amount of cooling water injected from each of the nozzles arranged on the upper and lower surfaces.

(Operation) The present invention having the above-described configuration operates as follows.

The first computing means is provided with various physical property values of the hot steel plate which are given in advance, such as material, plate thickness, plate width, plate length, cooling start temperature,
Based on the cooling stop temperature and the like, the relationship between the amount of cooling water injected from the nozzles arranged on the upper and lower surfaces and the heat transfer coefficient of the hot steel plate is obtained. The temperature distribution calculating means is calculated from the relationship between the actual temperature of the hot steel plate at the cooling device inlet detected by the temperature detecting means, the cooling water amount obtained by the first calculating means, and the heat transfer coefficient of the hot steel plate. It The temperature distribution in the thickness direction of the hot steel plate is calculated from the heat transfer coefficient at the actual amount of cooling water. The correction value calculating means is the heat for matching the temperature distribution of the upper and lower surfaces of the hot steel sheet calculated by the temperature distribution calculating means with the temperature distribution obtained from the actual temperature of the hot steel sheet detected by the temperature detecting means. A correction value for the heat transfer coefficient of the steel plate is calculated. Then, the stress-strain calculation means corrects the relationship between the heat transfer coefficient of the hot steel plate and the amount of cooling water obtained by the first calculation means by the correction value calculated by the correction calculation means, and after the correction, The stress strain inside the hot steel plate is calculated from the temperature distribution in the plate thickness direction obtained based on the relationship between the heat transfer coefficient of the hot steel plate and the amount of cooling water. Further, the warp amount calculating means calculates the warp amount of the hot steel sheet after being cooled by the cooling device, based on the stress strain calculated by the stress strain calculating means. The calculated warp amount and the actual warp amount of the hot steel sheet detected by the warp amount detecting means are relatively calculated, and the stress strain correction value obtained by the stress strain calculating means is calculated based on the comparison result. To do. Then, the cooling water amount control means is such that the warp amount in the latter half of the heat obtained from the stress strain value obtained by the stress strain calculation means that is generated by the correction value obtained by the stress strain correction value calculation means is minimized. The amount of cooling water sprayed from each of the nozzles arranged on the upper and lower surfaces is controlled.

Therefore, the stress inside the hot steel plate during cooling can be minimized, and the temperature accuracy of the upper and lower surfaces of the hot steel plate and the cooling temperature accuracy during the cooling process can be improved.

(Example) FIG. 1 shows a part of a steel plate production line equipped with a cooling control device for hot-rolled steel plates according to the present invention.

As shown in the figure, in the steel plate production line, there is a heating furnace 2 for maintaining the temperature of the hot steel plate 1 to be conveyed, and a scale breaker 3 for removing the scale formed on the surface of the hot steel plate 1.
And the rough rolling machine 4 for performing tenter rolling to the target plate width are sequentially arranged, and the hot steel plate 1 is roughly scaled to a predetermined width and thickness while the scale is removed in the steps up to this point. . Then, in the post-process of the rough rolling mill 4, a finish rolling machine 5 that rolls the hot steel sheet 1 to a target plate thickness, a hot straightening machine 6 that straightens the shape of the hot steel sheet 1 after finish rolling, and a post-shape straightening mill The cooling device 7 for accelerating and cooling the hot steel plate 1 is sequentially arranged, and the hot steel plate 1 after the accelerated cooling is a product having a desired shape and a desired material.

FIG. 2 is a diagram showing an arrangement state of measuring equipment for measuring the temperature and shape of the hot steel sheet 1 to be conveyed and an internal structure of the cooling device.

On the rear surface of the finishing rolling mill 5, a finishing rear surface thermometer 11 is provided,
The temperature of the hot rolled steel sheet 1 to be finish rolled is measured. Further, a cooling device front surface thermometer 13 is provided on the front surface of the cooling device 7, and measures the temperature of the hot steel plate 1 immediately before being conveyed to the cooling device 7. Further, a cooling device rear surface thermometer 14 and a shape meter 15 are provided on the rear surface of the cooling device 7, and the temperature and shape of the hot steel plate 1 after cooling by the cooling device 7 are measured.

Further, inside the cooling device 7, as shown in the drawing, a large number of nozzle groups 7c, 7c, ... Which inject cooling water to the upper surface 7A and the lower surface 7B of the route through which the hot steel plate 1 is conveyed are arranged. The injection of cooling water from the nozzle group 7c is controlled by the flow control valves 8,8, ...
Is divided into six cooling zones Z1 to Z6. That is, the hot steel sheet 1 to be cooled
Since the number of zones to be used differs depending on various factors such as the plate thickness and plate length, cooling start temperature, cooling stop temperature, etc.,
It is divided into six zones, and the number of zones used can be adjusted according to these factors. The amount of water in each cooling zone can be adjusted to each of the upper surface and the lower surface. Also, the cooling device 7
Radiation thermometer pair (hereinafter optical fiber thermometer pair) that uses optical fiber on the upper and lower surfaces of the central part in the plate direction between the entrance side of, between 3 and 4 zones, between 4 and 5 zones, and between 5 and 6 zones , 21,22,2
3 is provided to detect the upper and lower surface temperatures of the hot steel plate 1 in the cooling process.

FIG. 3 is a diagram showing an arrangement state of thermometers and an arrangement state of nozzles in the cooling device 7.

As described above, the optical fiber thermometer pair 20 is the cooling device 7.
Near the entrance of the fiber optic thermometer pair 21, between the 3 and 4 zones, fiber optic thermometer pair 22 between the 4 and 5 zones, fiber optic thermometer pair 23 between the 5 and 6 zones, respectively. It is arranged. Control of the amount of cooling water injected from the nozzles 7c in each zone is performed by the flow rate control valves 8 described above.

FIG. 4 is a schematic configuration diagram of a control system of the cooling control device for a hot rolled steel sheet according to the present invention.

The cooling control computer 30 that performs overall control of cooling in the cooling device 7 (control of water amount from each nozzle arranged on the upper and lower surfaces) includes a rolling control computer 31 that performs overall control of the rolling mill. , Mainly inputs and displays various data output from the business computer 32 that performs production control and the cooling control computer 30, and outputs control correction data and the like from the operator to the cooling control computer 30 The data input / output device 33 is connected, and the cooling control computer 30 operates various control devices described later based on the data from these computers 31 and 32 and the data input / output device 33. Further, a cooling data learning calculation computer 36 is connected to the cooling control computer 30 and learns a method of setting the amount of cooling water to be jetted from each nozzle when cooling the hot steel plate 1 and a method of setting a strip running speed. The result is output to the cooling control computer 30. Then, the cooling control computer 30 corrects the cooling rate which is different between the peripheral edge portion and the central portion when cooling the hot steel plate 1, and when cooling the hot steel plate 1. As shown in FIG. 2, the rotation speeds of the cooling water amount control device 38 for controlling the flow rate control valve 8 arranged in each zone and the steel plate feeding motor 39 driven when the hot steel plate 1 is conveyed are shown. A cooling speed control computer 40 is connected, and a cooling control computer 30 is connected.
Calculates and controls the mask amount, the cooling water amount, and the strip passing speed. Further, the cooling data learning calculation computer 36,
A shape data processing computer 34 for processing the shape data of the hot steel plate 1 output from the shape meter 15 is connected, and the processed shape data is a cooling data learning calculation computer.
Will be output to 36. In the shape data processing computer 34, each data after the shape data processing (amount of warp in the plate width direction (C warp), amount of warp in the plate length direction of the light plate optical tail end (L warp), the end of the wave plate side) A display device 35 for displaying the wave height and pitch of the side corrugations generated in the plate length direction, and the wave height and pitch of the central corrugation generated in the plate length direction inside the steel plate is connected.
The final shape of the steel sheet to be commercialized is displayed. The cooling data learning calculation computer 36 includes a rolling control computer 31, a business computer 32, a cooling device front surface thermometer 13, a cooling device rear surface thermometer 14, and an optical fiber thermometer arranged in the cooling device 7. The pairs 20 to 23, the cooling water amount control device 38, and the strip passage speed control device 40 are connected, and the learning calculation for performing the cooling control is performed based on the actual data output from the thermometer or the device of these computers.

FIG. 5 is a diagram showing the overall schematic operation of the cooling control device for a hot-rolled steel sheet according to the present invention.

The operation of this device is roughly divided into two operations. For the purpose of obtaining a predetermined material without causing a defective shape of the hot steel plate, it is necessary to set the cooling device until the cooling target material reaches the cooling device and improve the accuracy of the setting operation. The purpose is learning after cooling.

First, the setting of the cooling device will be described.

The rolling control computer 31 uses the hot steel plate 1 to be cooled.
Of actual rolling, that is, the temperature before the final finishing rolling entered by the finishing rear surface thermometer 11 (hereinafter abbreviated as finishing temperature)
The actual results such as actual results, plate thickness, plate width, etc. are output, and the cooling control computer 30 performs estimation calculation for estimating the temperature of each part of the hot steel plate 1 immediately before the cooling device 7. This estimation calculation uses the upper surface temperature (finishing temperature) of the hot-rolled steel sheet 1 immediately before the start of the final finishing rolling input by the rolling control computer 31 or the target finishing temperature input by the business computer 32, which will be described later, as an initial value. 10 divisions of the total thickness at the representative point
From the final finishing rolling to the cooling device 7 with 11 points as calculation points
The temperature transition to the entry side of is carried out by solving the one-dimensional heat conduction difference equation. The representative point is performed for one point in the longitudinal direction of the plate. However, considering the plate length, a difference is set in the calculated predicted arrival time of each part, and three points are set: the leading end, the center, and the tail end in the transport direction. is doing. In addition, when performing this calculation, the temperature change due to heat conduction, the effect of the temperature change due to the final finishing rolling of the finish rolling mill 5, the transformation, the effect of the temperature change due to the hot straightening device 6 and the like are taken into consideration.

Further, the business computer 32 instructs the cooling, that is, the lower surface water amount for each zone in the target finishing temperature cooling device 7, the target cooling start temperature when the hot steel plate 1 enters the cooling device 7, the hot steel plate 1 is the cooling device 7. Outputs the target cooling stop temperature, the number of used zones, the information on the material composition regarding the plate, the plate thickness, the plate width, the plate length, etc. when the data is output from the computer, and the cooling control computer 30 inputs these data, Predetermined standard operating values are determined for each strip width, cooling stop temperature, average bottom surface water volume, and usage zone.

This operation standard value is composed of an initial value when calculating an appropriate water and sewer ratio that keeps the amount of warp of the steel sheet in the width direction after cooling to an allowable value or less, and various mask amounts. In addition, the water quantity ratio of sewage is defined by the following formula, and the water quantity of the upper surface can be determined by determining the water quantity of the lower surface and the water quantity ratio of the lower surface.

This is based on the following concept. In order to control the material properties of the coolant (tensile strength, yield strength, elongation, etc.), temperature control is necessary.
Determine the plate temperature drop characteristics in the cooling device. On the other hand, in order to make the plate shape flat, it is desirable to make the temperature distribution in the plate thickness direction vertically symmetrical during cooling, and it is necessary to determine the upper surface water amount according to the lower surface water amount. Therefore, the ratio of sewage volume was adopted as a parameter.

Then, the cooling control computer 30 performs the cooling device inlet side temperature estimation calculation, the learning result obtained by the initial value of the water and sewage ratio given by the calculation result and the operation standard value determined and the temperature learning calculation described later. Based on the result, plate temperature estimation calculation is performed. Then, the stress-strain estimation calculation is performed based on the calculation result of the plate temperature estimation calculation and the learning result of the stress-strain learning calculation described later. Since this stress-strain estimation calculation is complicated, details of this calculation will be described later. Next, the cooling control computer 30 calculates the optimum up-down ratio of the amount of cooling water injected from the nozzles arranged on the upper and lower surfaces of the cooling device 7, based on the result obtained by the stress-strain estimation calculation. The amount of water to be jetted from the nozzles arranged on the upper surface of the cooling device 7 is determined by determining the optimum ratio, and the calculation result is output to the cooling water amount control device 38. Further, based on the result obtained by the plate temperature estimation calculation, the setting calculation of the optimum plate passing speed when the hot steel plate 1 is passed through the cooling device 7 is performed. The calculation result of the optimum strip passing speed is output to the strip passing speed control device 40, and the hot steel plate 1 is transported inside the cooling device 7 at a speed based on the calculation result.

On the other hand, the cooling control computer 30, based on the operation standard value, determines the mask amount of the steel plate front end, tail end and side end,
This mask amount is output to the mask control device 37. The control of the mask amount is performed to correct the difference in the cooling condition between the peripheral portion of the hot steel plate 1 and the other portions, and by this correction, the same applies to any portion of the hot steel plate 1. Will be cooled. Since the determination of the mask device and the mask amount is not a control closely related to the present invention, the detailed description of the determination will be omitted hereinafter.

Next, the learning performed after cooling the hot steel plate 1 will be described.

The cooling data learning computer 36 sends information about the plate such as components and the finishing rear surface thermometer 11 from the business computer 32.
The actual temperature of the hot steel plate 1 on the rear surface of the finishing rolling mill 5 detected by the rolling control computer 31 is input, and the inlet plate temperature measurement calculation of the cooling device 7 is performed. Also,
The computer 36 for cooling data learning calculation uses the optical fiber thermometer pair 20 at the inlet of the cooling device 7 to detect the actual upper and lower surface temperature difference of the hot steel plate 1 at the inlet side of the cooling device 7 and the cooling detected by the thermometer 13 at the front face of the cooling device. The inlet side temperature learning is calculated based on the upper surface temperature of the hot steel plate 1 on the inlet side of the device 7 and the measured value of the above-mentioned plate temperature setting calculation, and the learning result is obtained by the cooling control computer 30 at the time of setting. It will be used when setting calculation.

Next, the cooling data learning computer 36 uses the actual strip speed set by the strip speed control device 40, the actual water amount on the upper and lower surfaces set by the cooling water amount control device, and the cooling detected by the cooling device front surface thermometer 13. The actual temperature of the hot steel plate 1 on the inlet side of the device 7 and the actual temperature difference between the upper and lower surfaces of the hot steel plate 1 on the inlet side of the cooling device 7 detected by the optical fiber thermometer 20 at the inlet of the cooling device are input, and the plate under water cooling is input. Perform temperature estimation calculation. In addition, the cooling data learning calculation computer 36 uses the actual temperature of the hot steel plate 1 on the outlet side of the cooling device 7 detected by the cooling device rear surface thermometer 14 and the optical fiber thermometer 21 to 21 arranged inside the cooling device 7. Temperature learning calculation is performed based on the actual difference between the upper and lower surface temperatures of the hot-rolled steel sheet 1 during cooling between the 23 zones and the estimated value of the above-described sheet temperature estimation calculation. This learning result will be used for the plate temperature estimation calculation when the cooling setting is performed by the cooling control computer 30. Then, the cooling data learning control computer 36 performs stress strain estimation calculation based on the temperature estimation result during cooling obtained by the temperature learning calculation.

On the other hand, the shape data processing computer 34 inputs the shape data of the hot-rolled steel sheet 1 detected by the shape shape 15 after cooling,
How much the shape deviates from the ideal shape is calculated. The cooling data learning control computer 36 performs stress strain learning calculation based on the displacement calculated by the shape data processing computer 34 and the stress strain obtained by the stress strain estimation calculation. The learning result obtained by this learning calculation will be used in the stress-strain estimation calculation by the cooling control computer 30 at the time of setting. Further, the cooling data learning control computer 36 corrects the standard value upper / lower ratio initial value based on the deviation between the actual shape and the ideal shape calculated by the shape data processing computer 34,
This corrected value will be used when determining the operation standard value in the cooling control computer 30 at the time of setting.

Thus, the cooling control device for a hot-rolled steel sheet according to the present invention, first, before the hot steel sheet 1 is conveyed to the cooling device 7,
Estimating the plate temperature and plate shape during cooling, determining the plate passing hardness and the upper and lower surface cooling water amount in the cooling device 7, the cooling stop temperature becomes a preset temperature, so that a predetermined material is obtained, In addition, while the setting control of the cooling device is performed so that the shape becomes an ideal shape, learning calculation is performed based on the actual data of the hot-rolled steel sheet 1 after cooling, and this learning result is used for subsequent manufacturing of the hot-rolled steel sheet 1. In consideration of the data at the time, the quality and the like are managed by closed loop control.

The cooling control device for a hot-rolled steel sheet according to the present invention configured as described above operates as follows based on the flowcharts shown in FIG. 6 and subsequent figures. Incidentally, in the explanation of this flowchart, the explanation of the matters already explained above will be omitted.

First, the cooling setting calculation calculated before the hot steel plate 1 is conveyed to the cooling device 7 will be described with reference to FIG.

The cooling setting calculation is started at the start of finish rolling of the hot-rolled steel sheet 1 to be cooled (finish rolling is normally performed a plurality of times), immediately before the end of finish rolling, and at the timing when the data input / output device 33 corrects the data. First, the cooling control computer 30
Determines whether the finish rolling of the hot-rolled steel sheet 1 to be set has been performed before the final finishing rolling, and if the timing is earlier than the final finishing rolling, the target finishing temperature sent from the business computer 32 is set to the finishing temperature. At the timing after the final rolling, the actual finishing temperature detected by the finishing rear surface thermometer 11 and input by the rolling control computer 31 is determined as the finishing temperature. Also, this judgment is made by the computer for cooling control.
This is performed depending on whether or not the rolling control computer 31 has input to 30 (step 1). Next, the cooling control computer 30 performs estimation calculation of the temperature of the hot steel plate 1 on the inlet side of the cooling device 7 (step 2), and the business computer 32.
The operation standard value (the initial value of the water / sewage ratio, the mask amount) is determined based on the various data and the corrected standard value output from (step 3). Next, the cooling control computer 30 uses the temperature of the hot steel plate 1 on the input side of the cooling device 7 and the initial ratio of the upper and lower ratios determined in step 3 to perform a simple plate temperature estimation calculation and carry out the running speed of the hot steel plate 1. Is calculated (step 4). Next, the cooling control computer 30
Is the strip temperature determined in step 4 and step 2
Steel plate 1 on the inlet side of the cooling device 7 estimated in
Temperature, the learning value of the temperature obtained by the learning calculation of step 5 described later and the operation standard value (initial value of the vertical ratio) determined in step 3 The stress-strain estimation calculation is performed based on the learning value obtained as a result of the stress-strain estimation calculation. Based on the result of the stress-strain estimation calculation, the optimum top-bottom ratio of the cooling water amount is calculated from the upper and lower surfaces of the cooling water for which the stress-strain is to be minimized (step 5). And a computer for cooling control
In step 30, the plate temperature in the final cooling zone calculated in step 5 is compared with the target cooling stop temperature input by the business computer 31 to perform the correction calculation of the strip running speed (step 6). Result mask controller
37, the strip passage speed control device 40, and the cooling water amount control device 38, respectively (step 7), and the hot steel plate 1 is cooled.

A cooling learning calculation performed after cooling the hot steel plate 1 will be described with reference to FIG. The cooling data learning control computer 36 corrects the initial value of the vertical ratio in the operation standard value based on the actual ratio of vertical water amount and the actual warp amount (step 10). Next, the cooling data learning control computer 36 estimates the temperature of the hot steel plate 1 on the inlet side of the cooling device 7, and performs the inlet side temperature learning calculation from the estimated temperature and the actual temperature of the cooling device inlet side (step). 11). Then, the cooling data learning control computer 36 performs the plate temperature estimation calculation during cooling using the actual water amount and the actual strip temperature (step 12), and changes the estimated temperature and the actual cooling rear surface temperature and the actual upper and lower surface temperature. A temperature learning calculation during cooling is performed from the difference (step 13). Further, the cooling data learning control computer 36 uses the temperature learning value obtained in step 13 to calculate the temperature and the shape, compares them with the actual warp amount, and performs the shape learning calculation (step 14).

Next, the processing of each step of the main routine shown in FIG. 6 will be described in detail.

FIG. 8 is a subroutine flowchart of step 2 in the main routine.

This subroutine flowchart is a process for estimating the temperature of each part on the plate surface at the inlet side of the cooling device 7 while the hot-rolled steel sheet 1 is conveyed to the inlet side of the cooling device 7 before the start of final finishing rolling of the finishing rolling mill 5. It shows a procedure.

First, the cooling control computer 30 uses the finishing temperature determined in step 1 to determine the initial temperature distribution of 11 points in 10 divisions in the thickness direction of the hot steel sheet 1 by the following method.

The upper surface temperature is the finishing temperature. The temperature difference between the upper surface and the maximum plate temperature is given by the following formula.

ΔT = 33.8−3.63h (−0.0371 + 0.00528h) ・_TF However, ΔT: Temperature difference between the upper surface and the maximum plate temperature h: Plate thickness T _F : Finishing temperature The lower surface temperature is the upper surface temperature and the inlet side. Determined from the temperature learning value.

T _L = T _F + K ₁ ξ (ΔTs con + ΔTs class) + K ₂ However, T _L : Lower surface temperature ξ: Temperature conversion coefficient learning value ΔT _S : Inlet temperature upper and lower surface temperature difference learning value ξ, ΔT _S It will be described later in the description.

K ₁ , K ₂ : Adjusting elements, K ₁ = 1.0, K ₂ = 00 The radial temperature distribution satisfying the above conditions 1 to 3 is determined, and the temperature distribution in the plate thickness direction is determined.

FIG. 8 shows the determination method (step 20). Then, the cooling control computer 30 uses the time counter t for calculating the difference.
Is reset to 0 and started, and the plate temperature estimation difference calculation is started. This plate temperature estimation difference calculation is based on the initial temperature distribution state obtained in step 20,
This is carried out by solving the one-dimensional heat conduction difference equation shown in the following equation, using 11 points of the total thickness divided into 10 points at the representative points on the plate as calculation points (steps 21 and 22). Conversion from plate temperature T to heat content Q T> 880Q = 3.333 + 0.16T T ≦ 880Q = −149.05 + 0.481 ・ T-1.68 × 10 ⁻⁴・ T ² Q (i) _t ; Heat content of element i at time t T (i) _t ; Same temperature display Δt; Time interval for difference calculation (= const, 150 msec) ρ; Density λ; Thermal conductivity of element i Tg ; Air temperature ΔQ _S ; Boundary condition Δx; Thickness division thickness Converting heat content Q to temperature T (heat content; specific heat from 0 ° C to T
Q> 144.13T = −20.8 + 6.25 × Q 0 <Q ≦ 144.13 Since the method of giving ρ and λ is well known, detailed description will be omitted.

When the representative point reaches the finish rolling mill 5 when the final reduction is performed (step 23), the amount of heat generated by rolling is added. This amount of heat is the sum of plastic working heat, friction heat, and roll heat removal. The calculation formulas for these heats are also known formulas shown below.

1) Plastic working heat ΔQ _p = η _p · K _fm · ε / (J · P) Δ Q _p ; Plastic working heat (heat content display) n _p ; Efficiency (= const) K _fm ; Average deformation resistance K _fm ; Average Deformation resistance J; Work equivalent (= const) ρ; Specific gravity 2) Friction heat ΔQ _f = n _f · μ · P _m · ΔV / (J · P) ΔQ _f ; Friction heat (heat content display) n _f ; Efficiency (= const ) Μ; Friction coefficient (= const) P _m ; Average rolling force (finishing final reduction) ΔV; Relative speed difference between rolling roll and steel plate 3) Heat removal from roll ΔQ _R ; Heat removal from heat (display of heat content) η _R ; Efficiency C _P ; Specific heat T _R ; Rolling time ΔT; Amount of temperature drop before and after final rolling Since each element is known, detailed explanation is omitted (step twenty four). When the cooling control computer 30 determines that it is the time when the representative point reaches the hot straightening machine 6 based on the integrated time of the timer started in step 21 (step 25), the hot straightening machine 6 Add heat of temperature drop due to passage, that is, heat removal (step 2
6). The heat removal amount is shown below.

HL heat removal addition 1) HL heat removal ΔTHL; Temperature drop due to passing HL (heat removal amount) Next, at the time when the tip of the hot steel plate 1 reaches the cooling device 7, the cooling control computer 30 stores the temperature of the tip of the hot steel plate 1 (steps 27 and 28), and the center of the hot steel plate 1 is stored. At the time when the parts reach the cooling device 7, the cooling control computer 30 stores the temperature of the central part of the hot steel plate 1 (steps 29, 30), and the tail end of the hot steel plate 1 reaches the cooling device 7. When it is time to do so, the cooling control computer 30 stores the temperature of the tail end of the hot steel plate 1 (steps 31, 32). The arrival time of each part is determined based on the transport distance and the transport speed plate length. The integrated time of the timer for catching the moving position of the hot-rolled steel sheet 1 as time is integrated with the time interval of Δt (step 33). Δt is 0.1s
It is about ec. Then, the transformation heat is added to the temperature of each of the stored representative points. This addition of transformation heat is performed by comparing the calculated surface temperature of the central part with the Ar3 transformation point.

First, the Ar ₃ transformation temperature (Tar ₃ ) is calculated by the following formula.

_{Tar 3 = B 6 + B 7} [C] + B 8 [Si] + B 9 [Mn] + B 10 [Ni] + B 11 [Cu] + B 12 [V] B 6 = 868, B 7 = -396, B 8 = 24.6 , B ₉ = −58.7, B ₁₀ = −50, B ₁₁ = 35, B ₁₂ = 190, [C], [Si], [Mn], [Ni], [Cu], [V] are
Rolled steel sheet Each component 1/100% by weight (included in the sheet information from the vidicon) Addition of transformation heat is the following formula for each tip, center, tail and each part, considering the learning value. (Step 3
Four).

T (i) = Tc (i) + dT _trs + ΔT (i = 1 to 11) ΔT; Cooling device inlet side temperature learning value T (i); Cooling device inlet side plate temperature Tc (i); Inlet plate temperature dTtrs: Transformation heat value (common to the tip, center, and tail portions) When Tc (i)> Tar ₃ dTtrs = O Tc ≤ Tar ₃ dTtrs = B ₁₄ (Ts-Tar ₃ ) + B ₁₅ , Table 1 B ₁₄ B ₁₅ h> 18mm 0.56 9.09 16 <h ≦ 18mm 0.58 0.53 h ≦ 16mm 0.55 −7.98 Next, the operation standard value of step 3 in the main flowchart of FIG. 6 is determined.

Operating standard values predetermined by the plate width, the target cooling start temperature, the cooling stop temperature, the number of zones used in the cooling device 7, the lower surface water amount of each zone, which are input from the business computer 32, that is, the upper and lower sides of each zone. Determine the water volume ratio, side edge mask volume, tip mask volume, and tail mask volume. The ratio of the amount of water supplied to each zone becomes a search initial value for the optimum calculation of the ratio of vertical ratio performed in step 5.

Next, FIG. 10 shows a subroutine flow chart of the plate passing speed setting calculation of step 4 in the main flow chart shown in FIG. This sub-routine flowchart is for determining the optimum sheet passing speed of the hot steel plate 1 in the cooling device 7. The cooling control computer 30 calculates the average amount of water used in the cooling device 7 as follows (step 40).

Q _lav : Average bottom surface cooling water volume (m ³ / m ² minutes) Q (i); i zone bottom surface water volume (m ³ / m ² minutes) Lz (i); i zone cooling length (m) Nz; , Lz (i) is a cooling zone where no water flows and Lz (i)
= 0.

The average cooling water volume for the upper surface is calculated by the following formula.

Q _uav ; upper surface average cooling water amount (m ³ / m ² · min) η _{o (i)} ; water and sewage ratio initial value Next, the cooling control computer 30 calculates the temperature at the inlet side of the cooling device 7 calculated in step 2. The required cooling time tc and the temperature / time influence coefficient when the hot steel plate 1 is cooled to the target cooling stop temperature with this average amount of water with respect to the plate temperature in the central portion are obtained.
The temperature is calculated by the one-dimensional difference formula. The calculation is shown below.

(1) Inside plate One-dimensional heat conduction difference equation (2) Top and bottom surface points (3) Heat load <Suffix j represents the j-th element divided in the plate thickness direction.

(4) Heat transfer coefficient (divided into upper and lower surfaces) α = {αB ・ (W / K ₀ / K ₃ ) ^X } ^L αB = EXP {(a ₀ + a ₁・ Ts + a ₂・ Ts ² +… + a ²・ Ts ⁶ ) / 1000) X = b ₀ + b ₁・ Ts + b ₂・ Ts ² ＋ …… ＋ b ₆・ Ts ⁶ ) W: Water density (m ³ / m ² min) Ts: Steel plate surface temperature (× 10 ^-2 ℃) α B: Standard α L: Temperature learning value (before classification of upper and lower surfaces) H: Heat content (Kcal / kg), Ts: Steel surface temperature, ρ: Specific heat (kg / m ² ), Tw: Water temperature (℃), Kd: Thermal conductivity (Kcal / mhr ℃), Kd ₀ : 0 ℃ Thermal conductivity (Kcal / mhr ℃), φj: Conversion temperature (℃), Δt: Calculation division time (hr) = 1.39 × 10 ^-6 (50msec), Q: Surface heat load (Kcal / m ² hr) , Δy: Divided length in thickness direction (m), Tg: Ambient temperature (℃), C: Specific heat (Kcal / kg ℃), α: Heat transfer coefficient (Kcal / m ² hr ℃), β ₁ , β ₂ : The coefficients are β ₁ = 0, β ₂ = 1 for water cooling and β ₁ = 1, β ₂ = 0 for air cooling.

(5) Average plate temperature calculation (6) Cooling time tc; Sum of Δt until Tav reaches the target cooling stop temperature (7) Temperature / time influence coefficient dT / dt = (Tav ₀ = Taim) / tc dT / dt; Temperature / time influence coefficient Tav ₀ ; Average plate temperature at inlet side of cooling device Taim: Target cooling stop temperature Temperature / time influence coefficient is the falling temperature per unit time in the cooling calculation, that is, cooling rate, and this temperature / time influence coefficient The correction calculation of the cooling time, which will be described later, is performed by (step 41). Then, the plate passing speed is calculated based on the cooling time and the total length Lzone of the use zone. Vcc = Lzone / tc Vcc strip speed (step 42). The strip running speed obtained by the above calculation is
Since the speed was calculated assuming a constant amount of water in all zones,
It is a rough decision.

Next, FIG. 9 shows a sub-routine flow chart for determining the optimum water / sewer ratio in step 5 in the main flow chart shown in FIG. This sub-routine flowchart is a routine for performing a process for calculating the temperature and plate shape transitions in the cooling device 7 and determining the water / water flow ratio that minimizes the warp in the plate width direction for each cooling zone. Specifically, since the warp in the plate width direction is caused by the asymmetric distribution of the thermal stress in the plate width direction due to the temperature difference between the upper and lower surfaces, the exit side of the cooling zone for each cooling zone. The amount of warp in the plate width direction is estimated, and the amount of warp in the upper and lower surfaces for minimizing the warp in the plate width direction in the cooling zone, that is, for making the above-mentioned thermal stress symmetrical in the plate thickness direction is determined.

First, the cooling control computer 30 obtains the exit side passage time of each cooling zone in the central portion by using the already determined strip passing degree (step 50). Then, the cooling control computer 30 sets t = 0 when the calculation target point reaches the entrance side of the cooling device 7, and at the same time sets the value of the counter Z for counting the number of cooling zones to 1 (steps 51, 52). ).
Next, the cooling control computer 30 sets input conditions. The input conditions are the inlet side set temperature of the zone, the stress in the plate width direction, the plate width, and several kinds of water and sewer ratios provided before and after the standard operating water and sewer ratio (step 53).
Then, the plate temperature estimation calculation is performed in the same manner as the entrance side temperature estimation process of FIG. 7, the plate temperature estimation calculation of each representative point in the zone is performed, and the plate shape estimation calculation is performed.
This shape estimation calculation will be described later in detail, but is performed based on the one-dimensional thermoelastic-plasticity formula. These plate temperature estimation calculation and shape estimation calculation are performed at predetermined time intervals,
The process is repeated until the representative point leaves the cooling zone (steps 54 to 57). Then, the optimum water and wastewater ratio of the cooling zone obtained up to step 57 is calculated, the value of the counter Z is incremented by 1, and the process returns to step 53. And
The process returns to the main routine in which the calculated cooling zone number becomes equal to the zone number n determined by the operation standard value determination process (steps 58-60).

In this way, in this subroutine, the amount of warp in the plate width direction on the exit side of each zone is estimated on the entrance side of each zone, and the optimum water and sewer flow rate ratio that minimizes the amount of warp in the plate width direction in the zone is calculated. .

FIG. 12 is a subroutine flowchart of the shape estimation calculation shown in FIG. The calculation is performed for each time step Δt used in the cooling calculation in order to consider the temperature change with time in each part in the plate thickness direction. Now, suppose that the amount of warp in the plate width direction at the time is obtained.

The cooling control computer 30 uses a linear expansion coefficient of the hot steel plate 1,
Calculate physical properties such as Young's modulus and yield stress (step
61). Since the stress state at time t-t at time t is known, this stress is converted to a point on the stress-strain line. This conversion is for temperature compensation because the stress-strain diagram changes due to the temperature change of the hot steel plate 1 (step 62). Here, the stress-strain relationship is σ ≦ E, which is known in the elastic range.・ In the range of ε plasticity To do.

σ: stress ε: strain E: Young's modulus with respect to temperature at time t σγ ₁ , εγ: yield stress with respect to temperature at time t ₁ , yield strain, εγ: (σγ / E) Next, the cooling control computer 30 is a steel plate. In the thickness direction
It is divided into 10 parts, and the following simultaneous equations are created for each of the divided elements (i = 1 to 10) based on the values obtained in the above steps.

Where ΔP (i, t): time t for the i-th element from the top
Internal force increased from −Δt to time t A: Cross-sectional area of element E (i, t): Young's modulus of temperature i of the i-th element at time t from the top PL (i, t−Δt): From top Time t-Δ of i-th element
Length at t Δε _T (i, t): Time t−Δt of the i-th element from the top surface
Strain (temperature change X-ray expansion coefficient) X (i) from the plate thickness center to the thickness center of the i-th element from the upper surface E (t); plate at time t Young's modulus for the average temperature in the thickness direction BH: Thickness of each element ρ (t−Δt): radius of curvature of steel sheet at time t−Δt In the above equation, if the element i is plasticized, (σ / σγ) = (ε instead of E (i, t) / Εγ) ⁿ obtained from dρ / dε = nσγ · (ε / εγ) ⁿ⁻¹ · 1 / εγ.

Equation (2) is If i = 2 to n in the equation (2 '), simultaneous equations of n = -1 are obtained.

The coefficient of ΔP (i, t) in the equation (2 ′) is represented by C (i, l), C (i,
2), ... C (i, n) and the right side is D (i), i = 2
Equation (2 ') for n is Also, due to the balance of forces in the plate thickness direction, ΔP (1, t) + ΔP (2, t) + …… + ΔP (n, t) = 0 (3) Matrix display [K] ・{P} = {F} (4) In equation (4) Regarding the solution of this simultaneous equation, the simultaneous equation is expressed in matrix for ΔP (i, t) as shown below,
Below [K] matrix, shape matrix, {P}
Is called a stress increment matrix, and [F] is called a strain matrix. Then, based on the shape matrix obtained in step 63, the stress calculation due to thermal strain is calculated. This stress calculation is based on the general method of solving the matrix, and calculates the inverse matrix [K] ^-1 of [K] {P} = [1k] ^-1 to find the stress increment {P} The previous stress calculated for each time interval is added to (step 64). Next, based on the above stress, each element determines whether the elasticity is plastic, and if plastic, the stress value is the yield stress value,
Redetermine the stress of each element. Here, when plasticizing from elasticity, and when it is elasticized from plasticity, it is strictly necessary to perform a convergence calculation for stress-strain, but in the present invention, by reducing the calculation time step, the convergence calculation is omitted, The calculation time is shortened.

In addition, the stress of each element is redetermined, and the stress-strain relational expression Further, the mechanical strain at time t is obtained, and the length (that is, the plate width) of each element at time t is obtained together with the previously obtained thermal strain.

Further, the cooling control computer 30 calculates the plate width direction warp amount of the hot steel plate 1 based on the above calculation result.

The calculation of the warp amount is performed on the exit side of each zone.

Here, the warp amount in the plate width direction and the warp direction in which the plate asymmetry in the plate thickness direction in the plate width direction obtained above are canceled out are obtained by the following formula.

FIG. 13 is a subroutine flow chart of the plate passing speed correction calculation shown in step 6 of the main flow chart described in FIG. In this plate passing speed correction calculation, the plate passing speed roughly determined in step 4 is evaluated and corrected as necessary.

First, the cooling control computer 30 calculates the average plate temperature estimated value Tlast at the outlet side of the final water cooling zone of the cooling device obtained in step 5 of the main routine, and the business computer 3
2 is compared with the target cooling stop temperature Taim output from step 2 (step 80), and it is determined whether the absolute value of this temperature difference is larger or smaller than the allowable deviation amount ε (step 81).
℃. When this temperature difference is smaller than the allowable deviation amount, the acceleration rate is calculated so that the temperatures of the tip, center, and tail portions of the hot-rolled steel sheet 1 having a considerable length match when exiting the cooling device 7. (Step 82). On the other hand, when the temperature difference is equal to or more than the allowable deviation amount, the correction calculation of the required strip passing speed is performed. This modified calculation is shown in the following formula.

V = lzone / [Kv- (Tlast-Taim) / (dT / dt) + tc] Kv; coefficient = 0.6 dT / dt; temperature-time influence coefficient The speed obtained by this modified calculation is the optimum top / bottom ratio setting calculation (step Repeat 5). However, the correction is made within 5 times, and if the condition is not satisfied even after 5 times of correction, step 82 is performed.

FIG. 13 is a subroutine program in step 82 shown in FIG.

This calculation of the acceleration rate is performed so that the entire surface of the hot steel plate 1 is brought to a uniform temperature on the outlet side of the cooling device 7.

First, the cooling control computer 30 calculates the temperature of the inlet side of the cooling device 7 in each of the longitudinal direction, the tip, the center, and the tail end of the hot steel plate 1 in the inlet temperature setting calculation in step 2. Then, the cooling control computer 30 calculates the required cooling time in the cooling device 7 at each of the tip and tail portions from the required cooling time of the central portion used in step 5 of the hot steel plate 1, and based on this required cooling time. Calculate the strip speed pattern. The formula for cooling time is shown below. (Step 90).

t _m ＝ lzone / Vcc t _m ＋ (φ / Vcc) ・ (Tt−Tm) t _b ＝ t _m ＋ (φ / Vcc) ・ (Tb−Tm) φ: Coefficient t _t ； Tip cooling time t _b ; Tail end cooling time t _m ; Central part cooling time Vcc; Final strip speed determined lzone; Effective cooling zone length (sum of cooling zones for water cooling) Tt; Tip cooling device inlet side plate temperature (Average value in the thickness direction) Tm; Tail end cooling device inlet side plate temperature (thickness direction average value) Tb; Central part cooling device inlet side plate temperature (thickness direction average value) Next, cooling of each point of this plate is required. Calculate the strip speed pattern that satisfies the time. The sheet passing speed is given as a set of the data of the position of the plate leading edge and the conveying speed.

As shown in FIG. 15, when the position of the plate tip is x and the transport speed at this time is V (x), point A on the plate at the cooling device inlet at that time, in other words, x rearward from the plate tip. The water cooling time at the point is Given in.

Next, the water cooling times t _t , t _m , and t _b at the tip, the center, and the tail end are obtained by the following equations.

L: plate length V (x) = 1 / (ax ² + bx + c), and substituted into the above three equations to obtain a, b, c.

The acceleration range (domain of x) is defined by the following formula.

0 ≤ x ≤ L + lzone + Δlc ₂ L; plate length lzone; effective cooling zone length Δlc ₂ ; extra complex (= const) From the above, x is appropriately set within the determined acceleration range V
By substituting into the expression (x), the position of the plate front end and the transport set (speed pattern) at that time are created (step 91). Then, the calculation result is output to the strip passing speed control device 40.

In this way, the acceleration rate is obtained because the hot steel plate 1 is cooled while being conveyed, and therefore the time at which the cooling device 7 enters the steel plate tip portion and the tail end portion differ. That is, since the cooling start temperature is different along the lengthwise direction of the steel sheet, the temperature after cooling is different between the tip end portion and the tail end portion, and the striping speed is set to make the product material uniform over the entire length. This is because it is corrected by increasing the speed toward the tail end.

The above is the cooling setting process performed until the hot steel plate 1 as the cooling target material reaches the cooling device 7, and the cooling control device for the hot-rolled steel plate according to the present invention has a learning function described later, Controlled cooling is always performed under optimal conditions. In this learning, two components as error components, that is, a continuous component (continuous term) that changes as the rolling of the finish rolling mill 5 progresses, and a peculiar change such as a sheet thickness characteristic are performed. Intrinsic components (layer-wise terms) are taken into consideration. In the above description of the setting calculation, what is described as the learning value is the sum of the continuous term and the stratified order. However, when calculating the learning value, it is actually impossible to separate these two types of terms accurately.
The distribution of error is fixed and the distribution ratio is an adjustment item.

FIG. 16 shows a flowchart for correcting the standard value of operation in order to improve the accuracy of the standard operation value (the initial value of the water / sewer ratio) in step 10 of FIG.

The shape data processing computer 34 inputs the plate shape detected by the shape meter 15 and calculates the actual warp amount in the plate width direction of the hot steel plate 1 based on the input plate shape data (steps 100 and 101). Then, the cooling data learning calculation computer 36 calculates an operation standard value based on these data, that is, a new upper / lower ratio initial value for each zone, and updates the operation standard value. In this update, it is assumed that the warp amount in the plate width direction is proportional to the vertical ratio in the vicinity of the optimum value, and the vertical ratio is corrected. However, if the actual amount in the plate width direction is within the reference value (3 mm), this correction is not performed. The calculation formula is shown below (step 102).

η ₀ (i) new = η ₀ (i) old + Δη (i = 1 to ηus
e) Δη = K ₁ (Cr-Cair) where η ₀ (i) new; updated upper / lower ratio initial value η ₀ (i) old; before upper / lower ratio ratio initial value Δη; upper / lower ratio correction value ηuse; actual Final use zone No. Cr; Actual C amount of warp Cair; Target C amount of warp K ₁ ; Correction coefficient (= −0.01) Next, learning of the inlet temperature of the cooling device 7 in step 11 in the main flowchart of FIG. Will be described with reference to FIG.

The learning of the inlet side temperature of the cooling device 7 is performed for the purpose of improving the accuracy of the inlet side temperature estimation calculation of the cooling device 7,
Calculating an inlet-side temperature correction value that corrects the inlet-side absolute temperature value of the cooling device 7 and a correction value of the temperature difference between the upper and lower surfaces before the start of final finishing rolling that corrects the temperature distribution in the sheet thickness direction on the inlet side of the cooling device Is.

First, the inlet temperature estimation calculation is performed. This calculation is performed by the same formula as the input temperature estimation calculation in the above step. However,
The learning value is as follows.

Temperature conversion coefficient: Data used when calculating the setting of the material.

Entry temperature upper / lower surface temperature difference learning value; data used when setting calculation of the material.

Cooling device inlet side temperature learning value; data used when setting calculation of the material.

Calculated as calculation result Cooling device inlet side upper surface temperature Tcal (1)
And the temperature difference ΔTincal between the upper and lower surfaces is obtained (step 110).

Next, the learning value is updated. First, the inlet temperature correction value is updated according to the following formula (step 111).

ΔTu _IN = Treal (1) -Tcal (1) ΔTucon _N = g ₁ · ΔTucon _O + g ₃ · (1-g ₁ ) ΔTu _IN ΔTuclas _N = g ₂ · ΔTuclas _O + (1-g ₃ ) (1-g ₂ ) ΔTu _IN However, ΔTu _IN ; CLU inlet side upper surface temperature estimation error Treal (1); CLC inlet side thermometer actual measurement surface component Tcal (1); CLC inlet side plate temperature estimated value surface component ΔTucon _N , ΔTucon _O ; New and old CLC inlet temperature correction value continuous term (after and before update) ΔTuclas _N , ΔTuclas _O ; New and old CLC inlet temperature correction value stratified terms (after and before update) g ₁ , g ₂ ; Coefficient (0 ≦ g ₁ , g ₂ ≦ 1.0) g ₃ ; Coefficient (0 ≦ g ≦ 1) Next, the cooling device inlet side temperature upper and lower surface temperature learning value is updated according to the following equation (step 106).

_{ΔTs · con = g 5 · ΔTs} · con + g 7 · (1-g 5) · ΔT s CLC real ΔTs · class = g 6 · ΔTs · class + (1-g 7) · (1-g 6) · ΔT _{s CLC real} ΔTs ・ con; upper and lower surface temperature difference learning term (continuous term) ΔTs ・ class; upper and lower surface temperature difference learning term (stratified term) ΔTs CLC real; upper and lower surface temperature difference on CLC inlet side (measured at CLC inlet side _{value) g 5, g 6, g} 7: the coefficient upper and lower surfaces the temperature difference, the lower surface metal temperature - defined on the surface metal temperature.

Next, the temperature conversion coefficient is updated (step 113). However, ξ _N , ξ _O ; New and old of the temperature difference conversion coefficient between upper and lower surfaces (after updating and before) ΔT _{s FM set} ; Temperature difference between upper and lower surfaces before finishing 1 reduction (set as initial condition in learning calculation) ΔTSCLC cal CLC inlet side upper and lower surface temperature difference (calculation result on CLC inlet side) g ₄ ; Upper and lower surface temperature difference conversion coefficient update gain update gain Next, plate temperature during cooling in step 12 of the main flowchart of FIG. Estimate calculation subroutine flowchart
Shown in Figure 18.

First, the plate temperature distribution on the inlet side of the cooling device 7 is determined. That is, the cooling device front surface thermometer 13 and the optical fiber thermometer pair
The inlet side temperature distribution is determined using the actual value of 20.
This determination method is the same as the calculation of the initial temperature distribution in Step 20 described above, and is performed assuming that the temperature distribution in the plate thickness direction is radial, and the upper surface temperature is the actual measurement value of the inlet-side thermometer 13.

In addition, the temperature difference between the upper surface temperature and the maximum plate temperature should be
Using the formula for the temperature difference between the maximum plate temperature on the inlet side and the upper surface, which was obtained by calculating the initial temperature distribution of 20, the temperature difference between the upper surface and the lower surface is the actual upper and lower surfaces of the optical fiber thermometer vs. 20. The plate temperature distribution in the plate thickness direction is determined as the temperature difference (radiation is calculated) (step 120).

Next, the plate temperature transition calculation from the inlet side to the outlet side of the cooling device 7 is performed. This is to perform the plate temperature estimation calculation from the inlet side to the outlet side thermometer 18 of the cooling device 7 by using the model (calculation formula) used in the plate temperature estimation calculation in the above step 54 and the latest learned value. However, shape estimation calculation is not performed. Then, the following data are stored (step 121).

1. Upper surface estimated plate temperature Tucal (i); i at the exit side of each cooling zone
Corresponds to the cooling zone.

2. Lower surface estimated plate temperature TLcal (i); i at the outlet side of each cooling zone
Corresponds to the cooling zone.

3. Average value of the estimated upper and lower surface temperature on the outlet side of each cooling zone Taca
l (i).

4. Upper surface estimated plate temperature Tucal (Mz) under the outlet thermometer 18 5. Lower surface estimated plate temperature Tlcal (Mz) under the outlet thermometer 18 6. Upper and lower surfaces under the outlet thermometer 18 Average estimated plate temperature Tacal
(Mz) However, Mz = Nuse + 1, Nuse + number of actual use zones.

Next, the model error is calculated. All the plate temperature estimation errors of the model occur in the water cooling region, and in the air cooling region, it is considered that the plate temperature estimation errors accumulated by the water cooling are included as they are. A model estimation error is obtained using the upper and lower surface average plate temperature as a reference value (step 122).

Terror = Tmreal-Tacal (Mz) (29) Tmreal: Temperature measured by the rear surface thermometer of the cooling device Terror: Estimation error of the plate temperature by the rear surface thermometer of the cooling device.

Next, the model error is distributed. Although various methods can be considered for the error distribution method, in this embodiment, the simplest structure is adopted, and it is regarded as a level-up item for checking model behavior. The model error is assumed to increase in proportion to the water cooling time and is given by the following equation. Further, the model estimation error at an arbitrary time t is ΔTE (t).

ΔTE (t) = Terrorit / tclcout (0 ≦ t ≦ tclcout) or ΔTE (t) = Tterror (tclout <t). tclcout
Is the actual final cooling zone slip-out time. The exit side transit time of each zone is substituted into the above formula to calculate the model estimation error at the exit side of each zone. (Step 123).

ET (i) = ΔTE (tzoi) ET (i); Plate temperature estimation error at i-zone exit side tzoi; i-zone exit side transit time tclcout; Final use zone exit side transit time Next, determine the actual temperature transition. In this case, first, the actual temperature transition on the outlet side of each zone is obtained for the upper and lower surface points. The basic idea of determining the actual temperature transition is as follows.

1) It is considered that the temperature transition profile (time / temperature characteristic) of the model estimation is correct as a whole, and the actual temperature transition can be observed from the model estimated value and the model error.

2) Since the learning target is the heat transfer coefficient of the upper and lower surfaces, determine the temperature transition of the upper and lower surfaces (note the plate center and the average of all plates).

3) Actual upper and lower surface temperature transition is 21 with optical fiber thermometer
Express the upper and lower surface temperature difference measured in ~ 23.

Based on the upper and lower surface average plate temperature, the upper surface actual temperature change is calculated as (1/2) · (upper and lower surface average estimated value + model error-upper and lower surface temperature actual value), and the lower surface actual temperature change is (1 /
2) ・ (Estimated value of upper and lower surfaces + model error + actual value of upper and lower surfaces) These are actual temperature + actual temperature = estimated average + model error actual temperature- actual temperature = actual temperature difference between upper and lower surfaces Tur (i) = (1/2) ・ [Tacal (i) + ET (i)- DTr (i)] Tlr (i) = (1/2) ・ [Tacal (i) + ET (i) −DTr (i)] Tur (i); i Zone Outward upper surface actual temperature Tlr (i); i Actual temperature of lower surface of zone exit side DTr (i); Actual temperature difference of upper and lower surface of zone exit side However, DTr (1) and DTr (2) do not have a pair of optical fiber thermometers. versus
The actual values of the 20th and 3rd zone output side optical fiber thermometers 21 are interpolated with respect to time to obtain (step 124).

Next, the cooling temperature learning calculation in step 12 of the main flowchart in FIG. 7 will be described.

First, the actual temperature transition obtained in step 124 is regarded as a true value, and the learning value is calculated so that the result of the plate temperature estimation calculation matches the actual temperature transition. The learning value is a correction value for the heat transfer coefficient of the upper and lower surfaces, and is held over the entire temperature range for the upper and lower surfaces. The learning value has an exponential type as shown in the above temperature calculation formula. First, the basic idea will be explained.

1) It is assumed that all the errors of the plate temperature estimation calculation are in the errors of the upper and lower surface heat transfer coefficient models, and the temperature model learning has the form of the correction value of the heat transfer coefficient. That is, the temperature is on the horizontal axis, the heat transfer coefficient is on the vertical axis (logarithmic display), and the base has a heat transfer coefficient curve (upper surface or lower surface). The heat transfer coefficient learning value is obtained, and the base heat transfer coefficient is obtained. The coefficient is corrected with the learning value, and this is set as the heat transfer coefficient for the next heat transfer calculation.

2) The problem of obtaining the learning value of the heat transfer coefficient is a non-linear identification problem, and it is impossible to analytically obtain the optimum value.
Therefore, a computer experiment is performed to search for a learned value such that the estimated plate temperature output by changing the input condition matches the actual plate temperature.

3) The above computer experiments are sequentially searched and calculated to obtain a learning value. However, there are two input variable conditions to be identified (upper surface correction method and lower surface correction method), and this becomes an optimization problem of the two-dimensional parameter.

FIG. 20 shows a subroutine flowchart for this temperature calculation. First, an outline will be described. Optimal heat transfer coefficient correction values [Lud (j), Lld (j)] are obtained for each zone. Lud
(J) and Lld (j) calculate the plate temperature transition of the zone with nine different condition settings, and the upper and lower surface temperatures on the exit side of the zone have the highest difference between the actual value and the estimated value. Adopt small conditions. When the difference between the actual value and the estimated value is larger than the reference value, search again. This operation is carried out in all usage zones. Further, the temperature learning value is calculated for each cooling zone, but when the learning value is updated, the optimum correction value for each cooling zone is converted into the correction for each temperature range to update the learning value. It will be described with reference to FIG.

First, the correction value initial condition is set. A condition set of the heat transfer coefficient correction value for performing the retrieval calculation is performed (step 130).

Lua (i, j) = 1.0 + Δαu (i) …… (35) Lla (i, j) = 1.0 + Δαl (i) …… (36) Lua (i, j): j-zone condition i heat transfer on the upper surface Coefficient correction value.
i = 1 to 9, j ≦ 6.

Lla (i, j): Lower surface heat transfer coefficient correction value under the condition i in the j zone.

Δαu (i): additional value under condition i (upper surface).

Δαl (i): additional value under condition i (lower surface).

Δαu (i): The values of Δαl (i) are shown in the following table and FIG.

Table Condition (i) Δαu (i) Δαl (i) 1 0 0 2 0 Δα 3 Δα Δα 4 Δα 0 5 Δα -Δα 6 0 -Δα 7 -Δα -Δα 8 -Δα 0 9 -Δα Δα where Δα: Heat transfer coefficient change (constant) Next, the plate temperature is estimated and calculated. For condition i = 1 to 9,
A plate temperature estimation calculation for the zone (j) is performed. As the calculation formula, the same difference formula used in the plate temperature estimation calculation in step 121 is used to calculate the total thickness. However, instead of the learned value, the heat transfer coefficient correction values of Conditions 1 to 9 are used, and the shape estimation calculation is not performed.

For condition 1, Lua (i, j), Lla (i, j), ... Condition i
To, enter Lua (i, j), Lla (i, j) and use the inlet plate temperature and the actual water cooling time in common with all conditions. As a result, the calculation results of conditions 1 to 9 Tucal (1) to Tucal
(9), Tlcal (1) to Tlcal (9) are obtained. Tucal
(I): Upper surface plate temperature under condition i (outside of j zone) Tl
cal (i); lower surface plate temperature under condition i (outside of j zone) (step 131).

Next, the presence or absence of the optimum solution is determined. For the conditions 1 to 9, the following evaluation function value Ia (i) is calculated, and when the evaluation function value has a value smaller than the reference value, it is determined that there is an optimum solution.

Ia (i) = [Tur (j) −Tucal (i)] ² + [Tlr (j) −Tlcal (i)] ² (37) When Ia (i) <Ist, it is determined that there is an optimal solution. . Ist is a temperature error squared reference value (= 100).

When it is determined that the optimum solution exists, the zone exit side plate temperature (next zone initial temperature) distribution is determined. The j-zone outlet side plate temperature under the condition i * that minimizes Ia (i) is set as the initial temperature distribution of the next zone (step 134).

Next, when it is determined that there is no optimum solution, the correction value search range is corrected. Search again around the minimum of Ia (i). The heat transfer coefficient correction value is set to the conditions 1 to 9 again. However, the search range is narrowed.

Lua (i, J) = Lua (l, J) + Δαu (i) …… (38) Lla (i, j) ＝ Lla (k, j) ＋ Δαl (i) …… (39) Δαu (i): Ka ΔΔu (i) However, 1 is i (1: suboptimal condition) where Ia (i) satisfies the minimum. Ka is a search range correction coefficient (0 <Ka <1) and is a constant. FIG. 22 shows the state of the search (step 133).

When the final zone is completed (step 135), the optimum learning value is updated next. The optimum correction value determined in step 134 is converted into an optimum learning value vector, and the optimum learning value vector and the old learning value vector are subjected to exponential smoothing in vector units to determine a new learning value.

B) Learning value vector shape The upper and lower surfaces have independent shapes. Each component corresponds to a learning value for each surface temperature range. It also has continuous terms and stratified terms.

Ludg = [Ludg (1),… Ludg (j),… Ludg (n)] …… (40) Lldg ＝ [Ludg (1),… Ludg (j),… Ludg (n)] …… (41) Ludg (j); upper surface learning value for temperature range of steel sheet surface temperature <TS (j), Lldg (j); lower surface learning value for temperature range of steel sheet surface temperature <TS (j) Get the learning value.

(B) Conversion of the optimum correction value into the optimum learning vector.

Although the optimum correction value is calculated for each cooling zone, it is edited as a vector for each temperature. The relevant region of the surface temperature of each cooling zone is used as learning.

For the temperature range component at the boundary between the cooling zones, the average of both zones is taken as the learning value (the weighted average Ludg (j) * for the position of the temperature boundary value is taken). The area where there is no optimum correction value is 1.0.

Ludg * (j) = [Lud (k) * X {TS (j + 1) -Tur (k)] + Lud (k + 1) * X {Tur (k) -TS (j)}] / [TS (j + 1) -TS (J)] (40) j: Parameter for temperature classification k: Parameter for cooling zone Perform for each of the upper and lower surfaces. Repeat for each continuous and stratified item. FIG. 23 shows the relationship between the change in plate temperature and the calculated optimum correction value and optimum learning value.

C) Numerical smoothing.

In updating the learning value, exponential smoothing is performed in vector units.
This is done for each of the continuous and stratified terms.

Ludgcon (j) ＝ (1−g ₈ ) Ludgcon ＋ g ₈・ Ludge (j) ＊ …… (4
1) Ludgclass (j) ＝ (1－g ₉ ) Ludgcloss ＋ g ₉・ Ludge (j) ＊…
… (42) Ludgcon (j) ＝ (1−g ₈ ) Ludgcon ＋ g ₈・ Ludge (j) ＊ …… (4
3) Ludgclass (j) ＝ (1−g ₉ ) Ludgcloss ＋ g ₉・ Ludge (j) ＊…
(42) Ludgcon (j); continuous term upper surface heat transfer coefficient learning vector Ludgclass (j); stratified term upper surface heat transfer coefficient learning vector Lldgcon (j); continuous term lower surface heat transfer coefficient learning vector Lldgclass (j) ; Lower surface heat transfer coefficient learning vector of stratification Note that when a cooling zone occurs where actual and estimated temperatures do not converge when calculating the optimal correction value, the optimal correction value for the cooling zone before that is valid, Process as invalid. Updates are made only for valid zones.

Next, the stress-strain learning calculation in step 14 of the main flowchart of FIG. 7 will be described.

FIG. 24 is a subroutine flowchart of stress-strain learning calculation. This process is performed in order to improve the accuracy of stress strain estimation calculation.

The learning calculation is performed on the assumption that the error in the plate width direction warp amount estimated value is equal in each zone, and is in the form of correction of the plate width direction warp amount estimated value for each cooling zone.

First, the optimum learning value calculated by the temperature learning calculation described above is used, and the actual operation parameter is the actual value, and the temperature / shape estimation calculation is performed from the inlet side of the cooling device 7 to the bottom of the shape meter 15 to estimate the plate. Calculate the amount of warpage Ccal in the width direction (step 14
0).

Next, the shape meter calculated by the shape data processing computer 34
An estimated error ΔC _T of the warp amount in the plate width direction is calculated from the actual warp amount Creal in the plate width direction based on the actually measured shape (actual value) detected by 15 (step 141).

ΔC _T = Creal−Ccal The error ΔC (i) is distributed to each zone (step 14
2).

ΔC (i) = ΔC _T / Nuse …… (47) Nuse; Final use zo No. Next, the learning value is changed to the next ΔC (i) con and ΔC (i) class.
To update. The learning value is the continuous term ΔC (i) con and the stratified term Δ.
It has a C (i) class (step 133).

ΔC (i) con = (1-g ₁₂ ) ΔC (i) con + g ₁₂ · (1-g ₁₃ ) · ΔC (i) (48) ΔC (i) class = (1-g ₁₄ ) ΔC ( i) class + g ₁₄ · g ₁₃ · ΔC (i) (48) B ₁₂ : Update gain of continuous term B ₁₃ : Update gain of stratified term B ₁₄ : Allocation gain of continuous term and stratified term As above, In the present invention, in the cooling process of the hot steel plate 1, the heat transfer coefficient at the upper and lower surfaces of the plate is based on the amount of cooling water sprayed from the lower surface that is preset so as to obtain the cold speed required for securing the material. The amount of cooling water jetted from the upper surface is determined so as to match, and control is performed so that the amount of warp in the plate width direction is minimized. Further, since this control includes learning control, it is possible to easily obtain a desired material and shape, and it is possible to always manufacture a steel sheet having stable quality.

As shown in FIG. 25A (conventional cooling stop temperature accuracy record-target data) and FIG. 25B (cooling stop temperature accuracy record according to the present invention-target data), according to the present invention, It can be seen that there is much less variation in the accuracy of the cooling stop temperature compared to. Further, as shown in FIG. 26A (conventional plate width direction warp amount data) and FIG. 26B (plate width direction warp amount data), the present invention improves the plate width direction warp. I understand.

Further, although no specific numerical value is shown, along with the improvement of the warp in the plate width direction, the straightening rate, which indicates the degree to which the warp in the plate width direction should be corrected after the completion of cooling, was greatly reduced.

27A (conventional plate thickness direction hardness distribution) and FIG. 27B (plate thickness direction hardness distribution) show a conventional plate thickness direction hardness distribution state and a plate thickness direction hardness distribution state according to the present invention. Test results are shown.

As is apparent from this figure, the hardness difference between the upper and lower surfaces is extremely small, and it can be seen that uniform materials are obtained on the upper and lower surfaces.

28A (conventional plate width direction warped state) and FIG. 28B (plate width direction warped state) show the test results of the conventional C warped state and the plate width direction warped state of the present invention. It is shown.

As is apparent from this figure, the conventional maximum amount of C warpage was about 10 mm, but in the present invention, the maximum value is 1.5 m.
It is suppressed to about m. Therefore, a very flat shape can be obtained. 29A shows the water cooling start temperature in the longitudinal direction of the steel plate, FIG. 29B shows the water cooling end temperature in the longitudinal direction according to the conventional method, and FIG. 29C shows the water cooling end temperature in the longitudinal direction according to the present invention.

As is clear from this figure, according to the present invention, the temperature deviation in the longitudinal direction at the start of water cooling is improved and a uniform water cooling end temperature is obtained.

[Effects of the Invention] As is clear from the above description, in the present invention, the nozzles arranged on the upper and lower surfaces such that the amount of warpage of the hot steel plate obtained from the stress strain value obtained by the stress strain calculation means is minimized. Since the amount of cooling water injected from each of the above is controlled, it is possible to minimize the stress inside the hot steel plate during cooling, and improve the temperature accuracy of the upper and lower surfaces of the hot steel plate and the cooling temperature accuracy during the cooling process. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a part of a steel plate production line equipped with a cooling control device for hot-rolled steel plates according to the present invention, and FIG. 2 is a measuring device for measuring the temperature and shape of a hot steel plate being conveyed. FIG. 3 is a diagram showing an arrangement state and an internal structure of the cooling device, FIG. 3 is a diagram showing arrangement states of thermometers and nozzles in the cooling device, and FIG. 4 is cooling of the hot-rolled steel sheet according to the present invention. FIG. 5 is a schematic configuration diagram of a control system of the control device, FIG. 5 is a diagram showing the overall schematic operation of the cooling control device for a hot-rolled steel sheet according to the present invention, and FIG. 6 is a hot rolling process according to the present invention. Main flow chart of cooling control apparatus for steel sheet, FIG. 7 is a flow chart for performing cooling learning calculation, FIG. 8 is a subroutine flow chart for estimating inlet side temperature of hot steel sheet, and FIG. 9 is a case for performing plate temperature estimation calculation. The temperature distribution diagram used as a hypothesis for Fig. 11 is a subroutine flow chart for setting the optimum plate passing speed, Fig. 11 is a subroutine flowchart for determining the optimum vertical ratio of water volume, Fig. 12 is a subroutine flowchart for shape estimation calculation, and Fig. 13 is a plate passing speed. Subroutine flowchart for correcting the, Figure 14 is a subroutine flowchart for calculating the acceleration rate for uniformly cooling the hot steel sheet, Figure 15 is a conceptual diagram in the case of calculating the water cooling time based on the acceleration rate, FIG. 16 is a subroutine flowchart for correcting the standard value, FIG. 17 is a subroutine flowchart for the inlet side temperature learning calculation, FIG. 18 is a subroutine flowchart for the actual cooling temperature calculation, and FIG. 19 is an actual cooling temperature. Fig. 20 is a conceptual diagram for the calculation, Fig. 20 is a subroutine flowchart for temperature learning calculation, and Figs. Conceptual diagram of the process when performing temperature learning calculation, FIG. 24 is a subroutine flowchart of stress strain learning calculation, FIGS. 25A and 25B are distribution diagrams of cooling stop temperature accuracy between the conventional and the present invention, and 26A. FIG. 26 and FIG. 26B are distribution diagrams of C warpage height between the conventional and the present invention, FIG. 27A and FIG. 27B are diagrams showing plate thickness direction hardness distribution state between the conventional and the present invention, FIG. 28A and FIG. FIG. 28B is a diagram showing a deformed state of a hot steel sheet according to the related art and the present invention, and FIGS. 29A to 29C are comparison diagrams of temperature distribution between the conventional and the present invention at a cooling start temperature and a cooling end temperature. . 1 ... Hot steel plate, 5 ... Finishing rolling mill, 6 ... Hot straightening machine, 7 ... Cooling device, 7C ... Nozzle, 8 ... Solenoid valve (cooling water amount control means), 20-23 ... Optical fiber Thermometer (temperature detection means) 30 ... Cooling control computer (first calculation means, temperature distribution calculation means, correction value calculation means), 31 ... Rolling control computer (stress strain calculation means), 32 ... Business computer (First calculation means) 36 ... Computer for cooling data learning calculation (warp amount detection means), 38 ... Cooling water amount control device (cooling water amount control means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C21D 9/52 102 11/00

Claims (1)

[Claims] 1. A finish rolling mill for rolling a hot steel sheet to a predetermined thickness, and a width of the hot steel sheet placed in a post-process of the finish rolling machine and conveyed from above and below the hot steel sheet in both upper and lower directions. In a steel plate manufacturing apparatus in which a cooling device that sprays cooling water from a plurality of nozzles arranged in a direction to cool the hot steel plate while transporting the hot steel plate is provided, on a hot steel plate transported in the cooling device. A plurality of pairs of temperature detecting means for detecting the temperature of the lower surface, a warp amount detecting means for detecting the warp amount of the hot steel sheet after being cooled by the cooling device, and based on various physical property values of the hot steel sheet given in advance. hand,
First calculation means for determining the relationship between the amount of cooling water injected from the nozzles arranged on the upper and lower surfaces of the cooling device and the heat transfer coefficient of the hot steel plate, and the actual results of the hot steel plate at the cooling device inlet detected by the temperature detecting means From the relationship between the temperature and the amount of cooling water obtained by the first calculation means and the heat transfer coefficient of the hot steel plate,
The temperature distribution calculating means for independently calculating the temperature distributions of the upper and lower surfaces of the hot steel plate during cooling, and the temperature distribution of the upper and lower surfaces of the hot steel plate calculated by the temperature distribution calculating means are detected by the temperature detecting means. Correction value calculation means for calculating a correction value of the heat transfer coefficient of the hot steel plate to match the temperature distribution obtained from the actual temperature of the upper and lower hot-rolled steel sheet in the water cooling, and the correction value calculation means obtained by the first calculation means. The relationship between the heat transfer coefficient of the hot steel plate and the amount of cooling water is corrected by the correction value calculated by the correction calculating means, and is obtained based on the relationship between the heat transfer coefficient of the hot steel plate and the amount of cooling water after the correction. Stress-strain calculation means for calculating the stress strain inside the hot steel sheet from the temperature distribution in the plate thickness direction, and based on the stress strain calculated by the stress-strain calculation means, the thermal steel sheet after being cooled by the cooling device Warp amount calculating means for calculating the warp amount, the warp amount of the hot steel plate calculated by the warp amount calculating means and the actual warp amount of the hot steel plate detected by the warp amount detecting means are compared, and the comparison result Based on the correction value calculation means for calculating the stress strain correction value calculated by the stress strain calculation means, and the correction value obtained by the stress strain property value calculation means A hot-rolled steel sheet characterized by having a cooling water amount control means for controlling the amount of cooling water injected from each of the nozzles arranged on the upper and lower surfaces so that the amount of warpage of the plate obtained from the stress strain value is minimized. Cooling control device.