JPH08150409A - System for controlling temperature of rolled stock in hot strip mill - Google Patents

Abstract

PURPOSE: To highly accurately control the temp. of a rolled stock by calculating passing time between prescribed positions and conversion time of thermal rundown, obtaining an evaluation function and controlling strip coolant based on the evaluation function. CONSTITUTION: Finishing dtands 1-7 are provided with strip coolant devices 8-13, an inlet thermometer 14 and descaling device 15 are provided on the inlet side of a finishing mill and an outlet thermometer 16 on the outlet side. In this temp. control system for rolled stocks, the passing time between a 1st prescribed position and a 2nd prescribed position and the reduced time of thermal rundown based on a time interval till rolling starting point is passed through the 1st prescribed position are calculated and the evaluation function for temps. in the 2nd prescribed position. By executing the on-off control of the coolant based on the evaluation function, the temp. of the rolled stock is controlled with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the temperature of a rolled material on the outlet side of a hot strip mill finish rolling mill, and more particularly, by controlling the on / off of a strip coolant between stands, the length of a hot strip that has been finish rolled is increased. The present invention relates to a method for smoothing the temperature distribution in the direction.

[0002]

2. Description of the Related Art Generally, hot strip (hot rolled steel strip)
Skid marks and thermal rundown are the main causes of temperature variations in the rolling material longitudinal direction in the mill. The skid mark is a phenomenon in which the temperature of the part in contact with the skid pipe of the rolled material in the heating furnace in the pre-rolling process falls below the temperature of other parts. It is a phenomenon in which it takes time to reach the finish rolling mill entry side, and the temperature lowers during that time, causing the temperature to decrease toward the rear end side of the rolled material. Such temperature variations cause variations in the deformation resistance of the rolled material, and among them, thermal rundown has a large temperature drop amount, and therefore has a great effect on the quality such as the thickness of the rolled material after finish rolling.

In order to prevent this influence, the temperature of the rolled material on the exit side of the finishing mill of the hot strip mill is set to
Various methods for controlling to a preset temperature have been proposed. For example, Japanese Patent Laid-Open No. 58-178407 discloses a method of injecting strip coolant between stands of finish rolling mills according to a temperature distribution in the longitudinal direction of hot strips in a finish rolling mill or a rolling pressure distribution corresponding to the temperature distribution. A technique is disclosed in which the temperature fluctuation width in the longitudinal direction of the hot strip is suppressed to a small level by controlling the amount of water.

Further, Japanese Patent Laid-Open No. 62-6713 discloses that
Using the rolling data such as the rolling position, rolling load, and entry side plate thickness of each stand of the finishing rolling mill, the temperature change amount of the rolled material at each stand is calculated, and the strip coolant between each stand is calculated based on the temperature change amount. By controlling
A technique for making the temperature of the rolled material uniform in the longitudinal direction is disclosed.

Further, in Japanese Unexamined Patent Publication No. 62-40924, the operation amount of the strip coolant is determined from the target temperature of the rolled material on the delivery side of the finishing rolling mill and the like, and each point of the rolled material from the entry side of the finishing rolling mill is determined. Feed-forward control to inject water when the tracked point reaches just below the strip coolant between each stand, and to perform online learning to control the temperature of the rolled material on the exit side of the finishing rolling mill. Technology is proposed.

[0006]

The above-mentioned various methods all use feedforward control,
There is a problem that the temperature of the rolled material inside the finish rolling mill must be calculated while continuously measuring the temperature on the entry side of the finish rolling mill, and the amount of calculation is enormous. Also,
Instead of measuring the temperature on the entry side of the finish rolling mill, even if a method of predicting and calculating the temperature at that location is adopted,
There is no suitable guideline for determining the timing of changing the amount of strip coolant between the stands, and there is a problem that the temperature of the rolled material cannot be controlled with high accuracy.

In view of the above circumstances, the present invention requires a small amount of calculation to control the temperature of the rolled material and is capable of controlling the temperature of the rolled material with high accuracy, and is a rolling material temperature control method in a hot strip mill. The purpose is to provide.

[0008]

Means for Solving the Problems A rolling material temperature control system of the present invention which achieves the above object is: (1) Rolling with a plurality of strip coolants capable of freely turning on and off for injecting cooling water into a rolling material being passed. After an arbitrary predetermined point on the rolled material passes through the entrance side of the finish rolling machine for finishing rolling the material or the first predetermined position in the finish rolling machine, the predetermined point is the exit side of the finish rolling machine. Or a passage time calculating means for calculating a passage time until it passes through a second predetermined position on the downstream side of the first predetermined position in the finish rolling mill (2) A predetermined rolling start point is set as a starting point Conversion time calculating means for calculating a conversion time obtained by converting the thermal rundown of the predetermined point into time, based on the time interval until the predetermined point passes the first predetermined position (3) The passage time and the conversion Based on time and above prescribed Evaluation function calculating means for calculating an evaluation function for evaluating the temperature at the second predetermined position (4) Based on the evaluation function, the temperature of the rolled material at the second predetermined position falls within a predetermined temperature range. As described above, a strip coolant control means for controlling on / off of a plurality of strip coolants is provided.

In the rolled material temperature control method of the present invention, further, (5) temperature calculation means for calculating temperatures at a plurality of points on the rolled material having different evaluation function values from each other (6) temperature at the plurality of points Timing control means for determining the on / off timing of each of the plurality of strip coolants based on the above, and (7) the strip coolant control means controls on / off of the plurality of strip coolants based on the timings determined by the timing calculation means. It is preferably one.

[0010]

In the rolling material temperature control method of the present invention, the passing time in (1) above and the conversion time in (2) above are calculated to calculate (3) above.
Is used to control the strip coolant on / off based on this evaluation function.The evaluation function can be obtained with a small amount of calculation, and the amount of cooling water that cools each point of the rolled material to the target temperature is high. It is possible to predict with accuracy, and it is possible to control the temperature of the rolled material with high accuracy while maximizing the capacity of the finishing mill.

Further, as a specific method for controlling the on / off of the strip coolant based on the evaluation function, as described in (5) above, a plurality of points on the rolled material, more specifically, the maximum and minimum points of the evaluation function, for example, can be used. And the temperature of the strip coolant is calculated based on these temperatures ((6) above), and the strip coolant is configured to be turned on and off based on that timing. It is possible to determine the on / off timing of the strip coolant over the entire length of the rolled material by simply calculating the temperature at points with few Can be controlled with high precision.

[0012]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 is a schematic structural diagram of a hot strip mill finish rolling mill to which an embodiment of the present invention is applied. The finish rolling mill is provided with finish stands 1 to 7 and strip coolants 8 to 13 are provided between the finish stands 1 to 7. Further, the finish rolling mill inlet side thermometer 14 and the descaling device 15 are provided on the entrance side of the finish rolling mill, and the finish rolling mill exit side thermometer 16 is provided on the exit side of the finish rolling mill. Has been.

In the following, the position on the rolled material (distance L from the tip of the rolled material) and the speed V of the rolled material are all the rolled material even if the rolled material is at a position before rolling or during rolling. Indicates the distance when converted after being rolled, and the speed at the position of the exit side thermometer 16 of the finishing rolling mill.
FIG. 2 is a diagram showing the rolling speed V with respect to the time T (horizontal axis) based on the time point when the rolled material front end passes through the finishing rolling mill inlet side thermometer 14.

The rolling speed V of the rolled material has speed break points P _{1 to} P ₄ as shown in FIG. Here, when a point on the rolled material that is L [m] away from the tip of the rolled material at the time T passes through the finishing rolling mill inlet side thermometer 14, the time T is: T = F ₁ (L, speed folding Position of points) (1) where F ₁ represents a function. Can be written as

FIG. 3 shows a point on the rolled material, which is L [m] away from the tip of the rolled material, starting from the time when the leading edge of the rolled material passes through the finishing rolling mill inlet side thermometer 14. For time T (horizontal axis) when passing through the rolling mill entrance side thermometer 14,
It is a figure which shows the passage time T _D (vertical axis) from the point of the L [m] passing through the finishing rolling mill inlet side thermometer 14 to passing through the finishing rolling mill outlet side thermometer 16.

The passing time T _D shown in FIG. 3 is calculated by using the rolling speed V shown in FIG. 2. The passing time T _D = F ₂ (L, position of speed break point, virtual length of finish rolling mill). 2) can be obtained as Here, F ₂ represents a function, and the virtual length of the finish rolling mill is the thickness of the rolled material between the stands, if the thickness after the completion of rolling (thickness at the position of the finishing mill exit side thermometer 16). ), The distance between the stands should be extended so that a rolled material of the same weight as the actual weight before placing such an assumption would be placed between those stands. , The length between the finishing-roller inlet-side thermometer 14 and the finishing-roller outlet-side thermometer 16.

Further, in the same manner as the method of calculating the passage time T _D , an arbitrary point of the rolled material (L [m] from the tip of the rolled material is obtained.
(A distant point) passes an arbitrary position in the finish rolling mill, for example, a time when each position of each strip coolant 8 to 13 passes,
It is also possible to determine a passage time from when a rolled material passes through a position in the finish rolling mill to when it passes through another position downstream thereof.

[0018] Figure 4 is a point of L [m] from the tip of the rolled material, passing time from passing through the finishing stands 1 shown in FIG. 1 until passing through the finishing mill delivery temperature meter 16 T _D ( (Vertical axis). As in the case of FIG. 3, the abscissa indicates the point at which the rolled material enters the finishing rolling mill thermometer 14 after the tip of the rolled material passes through the finishing mill rolling thermometer 14. It represents the time to pass.

One embodiment of the present invention whose schematic diagram is shown in FIG. 1 is suitable.
The finishing rolling mill used is a thermometer 14 on the inlet side of the finishing rolling mill.
The air-cooling section between the descaling device 15 and the
In the air-cooled section, there is little change in rolling speed and temperature change.
The effect on the finishing stand is shown in Fig. 3
1 and the finishing rolling mill exit side thermometer 16 transit time T _D 
The evaluation function described later may be obtained based on ′.

This transit time T _D ′ is the transit time T _D ′ = F ₃ (L, the position of the speed break point, the virtual length between the finishing stand 1 and the finishing pressure gauge 16 on the exit side). It can be expressed as (3).

FIG. 5 is a graph showing a function obtained by converting the thermal rundown into time. The thermal rundown can be conveniently expressed as a time function D by multiplying the time T in the above formula (1) by a function R (steel type, plate thickness) determined by the steel type and plate thickness of the rolled material. D = R (steel type, plate thickness) × F ₁ (L, position of speed break point) (4) By combining the above formulas (2) and (4), the finish rolling mill output side thermometer 16 The evaluation function H representing the temperature of the rolled material at the position can be obtained as follows.

H (L, plate thickness, position of speed break point, steel type) = F ₂ (L, position of speed break point, virtual length of finish rolling mill) + R (steel type, plate thickness) × T (L, speed) (Folding point position) (5) Here, using the equation (5), the point at the position of the finishing rolling mill inlet side thermometer 14 on the rolled material when the speed V of the rolled material changes Finishing mill exit side thermometer on rolled material 16
The evaluation function of the point at the position is obtained for each of the speed break points P _{1 to} P ₄ (see FIG. 2). As a result, it is possible to know how many meters from the tip of the rolled material the maximum point of the evaluation function is, and how many meters there is the minimum point of the evaluation function.

FIG. 6 is a graph showing the evaluation function obtained as described above for a rolled material of a certain steel type and plate thickness,
FIG. 7 is a graph showing changes in the temperature measurement value by the finish rolling mill outlet side thermometer 16 when rolling is performed on the rolled material of the steel type and plate thickness while keeping the water cooling conditions in the finishing rolling mill constant. Comparing FIG. 6 and FIG. 7,
It can be seen that the lowest temperature point and the highest temperature point obtained by the evaluation function and the actually measured lowest temperature point and the highest temperature point are extremely well matched.

Next, regarding the two points of the evaluation function shown in FIG. 6, namely, the lowest temperature point and the highest temperature point, the heat balance is not calculated but the temperature is calculated by properly calculating the temperature, Based on these temperatures, the on / off timings of the strip coolants 8 to 13 were calculated so that the temperature of the rolled material at the position of the exit-side thermometer 16 of the finish rolling mill was always controlled to be constant. Strip coolant 8-13
As shown in FIG. 1, one stand is provided in each stand, and since there are six in total, the total number of on / off controls that can be performed is six. According to the temperature calculation, the number of strip coolants to be turned on (water injection) was 0 at the lowest temperature point, and the number of strip coolants to be turned on (water injection) at the highest temperature point was 6.

FIG. 8 is a graph of the evaluation function shown in FIG.
FIG. 9 is a graph showing the on / off timing of the strip coolant, and FIG. 9 is a graph showing the temperature measurement result of the rolled material by the finishing rolling mill outlet side thermometer 16 when the strip coolant is on / off controlled as shown in FIG. By the relatively simple calculation as described above, the on / off timing of the strip coolant as shown in FIG. 8 is obtained, and by controlling the on / off of the strip coolant in such a manner, as shown in FIG. Precise temperature control is performed.

In the above embodiment, the evaluation function was obtained based on the passage time between the finishing rolling mill inlet side thermometer 14 or the finishing stand 1 and the finishing rolling mill outlet side thermometer 16. The positions of the starting point and the end point are not limited to the positions of the finishing rolling mill inlet side thermometer 14 or the finishing stand 1 and the finishing rolling mill exit side thermometer 16, and the present invention is limited to a certain section in the finishing rolling mill. , It can also be applied only between certain stands.

[0027]

As described above, according to the present invention,
It is possible to obtain an evaluation function by a relatively simple calculation, control the strip coolant on / off based on the evaluation function, and control the temperature of the rolled material with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of a hot strip mill finish rolling mill to which an embodiment of the present invention is applied.

FIG. 2 is a diagram showing a rolling speed with respect to a time based on a time point when a front end of a rolled material passes through a thermometer on an entrance side of a finishing rolling mill.

[FIG. 3] The starting point is the time when the leading edge of the rolled material passes through the thermometer on the entry side of the finishing rolling mill. Thermometer 14
FIG. 7 is a diagram showing a passage time T _D from the time when the point of L [m] passes through the finish rolling mill inlet side thermometer to the time when it passes through the finishing rolling mill exit side thermometer with respect to the time of passing through.

FIG. 4 shows the passing time T _D ′ from the tip of the rolled material to the point L [m] after passing through the finishing stand 1 shown in FIG. It is a graph.

FIG. 5 is a graph showing a function in which thermal rundown is converted into time.

FIG. 6 is a graph showing an evaluation function obtained as described above for a rolled material having a certain steel type and plate thickness.

FIG. 7: Temperature measurement by an exit side thermometer of the finishing rolling mill when rolling was performed with the water cooling conditions in the finishing rolling mill kept constant for the rolled material having the steel type and plate thickness for which the evaluation function shown in FIG. 6 was obtained. It is a graph showing change of a value.

FIG. 8 is a diagram showing the on / off timing of the strip coolant on the graph of the evaluation function shown in FIG.

9 is a graph showing the results of temperature measurement of a rolled material by a thermometer on the exit side of the finishing rolling mill when the strip coolant is controlled to be turned on and off as shown in FIG.

[Explanation of symbols]

 1,2, ..., 7 Stand 8,9, ..., 13 Strip coolant 14 Thermometer for inlet of finishing rolling mill 15 Descaling device 16 Thermometer for outlet of finishing rolling mill

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichiro Maeda 1 Kawasaki-cho, Chuo-ku, Chiba City Inside the Kawasaki Steel Co., Ltd. (72) Inventor Takayuki Kaji 1 Kawasaki-cho, Chuo-ku, Chiba Kawasaki Steel Co., Ltd. In-house

Claims (2)

[Claims] 1. A first predetermined inside of a finishing rolling mill or a first predetermined inside the finishing rolling mill, comprising a plurality of strip coolants that can freely turn on and off to inject cooling water into the rolling material being passed. After an arbitrary predetermined point on the rolled material passes through the position, the predetermined point is a second predetermined point downstream of the first predetermined position on the exit side of the finish rolling mill or in the finish rolling machine. A passing time calculating means for calculating a passing time until passing the position, a predetermined point based on a time interval from the predetermined rolling start time until the predetermined point passes the first predetermined position. A conversion time calculating means for calculating a conversion time obtained by converting the thermal rundown into time, and an evaluation function for evaluating the temperature at the second predetermined position of the predetermined point based on the passage time and the conversion time. Evaluation function calculator And a strip coolant control means for controlling on / off of the plurality of strip coolants so that the temperature of the rolled material at the second predetermined position falls within a predetermined temperature range based on the evaluation function. Method for controlling temperature of rolled material in hot strip mill. 2. The temperature calculation means for calculating the temperature of a plurality of points on the rolled material having different values of the evaluation function, and the on / off timing of each of the plurality of strip coolants based on the temperatures of the plurality of points. 3. The strip coolant control means controls ON / OFF of the plurality of strip coolants based on the timing obtained by the timing calculation means. Rolled material temperature control method in hot strip mill.