JPH04323325A - Method for controlling temperature of steel sheet in continuous annealing furnace - Google Patents

Abstract

PURPOSE:To stablish accurate temp. control method in the case of executing continuous heating treatment in a continuous annealing furnace by joining steel sheets having different conditions in dimension, aimed sheet temp., material quality, etc. CONSTITUTION:At the time of executing the continuous treatment to the preceding material and the following material having different conditions in the continuous annealing furnace, at first, the order of priority to the preceding material and the following material is decided based on the sheet thickness, the preset aimed temp. and torelance in the sheet temp., and a sheet temp. responsive curve from the preceding material to the following material, in which the length of out of the sheet temp. in the material at the priority side becomes zero and length of out of the sheet temp. in the material at non-priority side becomes the min. value and changing timing for setting line velocity for realizing this and the furnace temp., are calculated under presuming and also, based on this, the line velocity and the furnace temp. are controlled, respectively.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] This invention involves joining steel plates (strips) with different conditions such as dimensions, target plate temperatures, materials, etc. and continuously processing them in a continuous annealing furnace. The present invention relates to a method for controlling the temperature of a steel plate at a joint between a preceding material and a succeeding material. [Prior art and its problems] In a continuous annealing furnace, steel plates (
In order to heat-treat the strip continuously, the rear end of the "strip being threaded" and the front end of the "strip to be threaded next" are connected by welding on the entrance side of the furnace. In this case, if at least one of the dimensions (thickness and width), target strip temperature, and material of each strip before and after the weld are different before and after the weld, the line speed and furnace temperature may be changed at the weld. Must. By the way, in a continuous annealing furnace, the furnace temperature is generally controlled by a furnace temperature control device by manipulating the fuel flow rate so that the furnace temperature setting value and the actual furnace temperature match. However, in this case, the furnace temperature response is poor because the heat capacity of the furnace is very large. That is, it takes about 20 minutes for the actual furnace temperature to reach the set furnace temperature after changing the furnace temperature setting value. Therefore, there was a problem that the plate temperature of the strip deviated from the target plate temperature value between these areas, making it impossible to obtain predetermined mechanical properties. [0004] Therefore, if the plate temperature cannot be avoided,
A method has been proposed in which the deviation in mechanical properties of the strip is intentionally caused to occur on the overheated side, where there are fewer problems in terms of plate quality, to reduce deviations in the mechanical properties of the strip (Japanese Patent Laid-Open No. 57-35640, etc.). but,
This method had a new problem: ``If the target plate temperature and plate thickness change at the same time before and after the weld, the plate temperature deviation toward the overheating side will be too large.'' . For this reason, the present applicant previously proposed the following method of controlling the temperature of a steel plate in a continuous annealing furnace (Japanese Patent Application No. 317013/1983), but this method is shown in the time chart of FIG. This is explained by: FIG. 3 shows that, as shown in item (A), the thickness H1 of the preceding material is smaller than the thickness H2 of the succeeding material (H1 < H2), and as shown in item (B), the thickness H1 of the preceding material is smaller than the thickness H2 of the succeeding material. This example relates to a temperature control example when the target plate temperature T1 of the material is smaller than the target plate temperature T2 of the next material (T1 < T2). Here, since the response time of the furnace temperature is long, about 20 minutes, the plate temperature becomes a response curve as shown in item (E), and the upper limit (a) and lower limit (b) of the plate temperature tolerance.
An out-of-tolerance part (c) of the preceding material and an out-of-tolerance part (d) of the plate temperature of the next material occur. Therefore, in order to minimize the plate temperature deviation parts (c) and (d),
Setting changes are made to the line speed shown in item (C) and the furnace temperature shown in item (D). That is, the parts (c) and (d) outside the plate temperature tolerance.
When the areas of are respectively E1 and E2, the "timing of changing the line speed V1 of the preceding material to the line speed V2 of the next material" and "the timing of changing the line speed of the preceding material V2" are set such that the evaluation function E calculated by the following formula is minimized. Calculate the timing for changing the furnace temperature F1 from the furnace temperature F2 of the next material to the furnace temperature F2 of the next material. E=αE1 + (1-α)
E2 (0<α<1)...
(1) The parameter α in the above equation (1) is a parameter for specifying the sheet temperature response curve of “prior material emphasis” or “following material emphasis”, and is a parameter for specifying the plate temperature response curve of “prior material emphasis” or “following material emphasis”. It is specified in advance as a table value according to the size of the plate temperature tolerance. In actual sheet temperature management, as shown in item (E) in FIG. 3, the sheet temperature tolerance deviation length L1 of the preceding material from the sheet temperature tolerance upper limit (a) and lower limit (b) The board temperature tolerance length L2 of the row material is the control standard. [0009] Although the temperature control of the steel plate was made very stable by the above-mentioned means proposed earlier by the present applicant, it was still found through actual work that ``this method that minimizes the evaluation function E of the above equation (1)'' Then, the parameter α and the plate temperature response curve (E
) is difficult to grasp, and the length L is outside the plate temperature tolerance.
Parameters are indirectly set so that 1 and L2 meet the management standards.
It has become recognized that it is extremely difficult to specify the data α. For example, in FIG. 3, if it is desired that the sheet temperature deviation length L2 of the next material is zero and the sheet temperature deviation length L1 of the preceding material is to be minimized, appropriate parameters corresponding to this should be set.
It is difficult to specify the value of α in advance. For this reason, Figure 4
It is not necessarily a practical method as it requires repeated calculations as shown in the figure. [00011] Therefore, an object of the present invention is to eliminate the above-mentioned problems seen in the conventional method and to accurately and accurately control the temperature of treated steel sheets in a continuous annealing furnace without requiring particularly difficult operations. The aim was to establish a means of stable control. [Means for Solving the Problems] The present invention was completed based on the research results of the present inventors, who conducted numerous experiments in order to achieve the above object. When continuously processing preceding material and subsequent material under different conditions in a continuous annealing furnace equipped with a speed control device and a furnace temperature control device, based on the sheet thickness, predetermined target sheet temperature and sheet temperature tolerance, In addition to determining which of the preceding material and the following material has priority (determining priority criteria in advance as described below), it also determines the "length of the sheet temperature deviation from the sheet temperature tolerance" of the priority material. ``Plate temperature response curve from the preceding material to the next material'' where ``length of plate temperature deviation from plate temperature tolerance'' of the non-priority side material is zero and the minimum value, and setting of line speed and furnace temperature for this. By predicting the change timing and controlling the line speed and furnace temperature based on this,
Even if conditions such as steel plate dimensions, target plate temperature, material quality, etc. differ between the preceding material and the subsequent material, accurate steel plate temperature control can be carried out so that at least the priority material can stably satisfy the plate temperature control standards. It is characterized by the fact that Hereinafter, the present invention will be described in more detail along with its functions and effects based on Examples. Embodiment FIG. 1 shows an example of temperature control of a steel plate when the method of the present invention is applied to a heating zone of a continuous annealing furnace. In Fig. 1, the part indicated by the symbol (1) has a steel plate (s) inside.
This is a continuous annealing furnace heating zone equipped with a hearth roll (2) for transferring. The flow rate of fuel supplied to the continuous annealing furnace heating zone (1) is controlled by a furnace temperature control device (5).
Furnace temperature detector (
3) Fuel flow control device (4) based on the signal from
It is done through. A plate temperature detector (6) is provided on the exit side of the continuous annealing furnace heating zone (1). In addition, a drive motor (7) is installed on the entrance side of the continuous annealing furnace heating zone (1).
A pair of upper and lower bridle rolls (8) driven by a motor are provided, and the speed of this drive motor (7) is controlled by a speed control device (9). A welding point detector (10) is provided on the entry side of the bridle roll (8), and a welding point position signal is input to a welding point position tracking device (11). This welding point position tracking device (11), speed control device (9), and furnace temperature control device (5) are connected to a setting command device (15), and this setting command device (15)
is line speed/furnace temperature setting change timing calculation device (12
)It is connected to the. This line speed/furnace temperature setting change timing calculation device (12) includes a next line material setting value calculation device (13).
) and a plate temperature tolerance priority determination device (14) are connected. Then, the next material setting value calculation device (13) receives information on the thickness, width, target material temperature, and material of the next material, and the line speed/furnace temperature setting change timing calculation device (12) receives information on the thickness, width, target material temperature, and material of the next material. The plate temperature tolerance priority determination device (14) receives information on the plate thickness, target plate temperature, and plate temperature tolerance. Next, the control process based on the above configuration is shown in FIG.
This will be explained based on the flowchart shown in FIG. First, we receive the coil information (thickness, width, target plate temperature, material) of the next material, the actual line speed and furnace temperature of the preceding material, and the information on the sheet temperature tolerance of the preceding material and the next material. and store it in memory. Next, using the information received and stored in the memory and the line speed table values prepared in advance, the line speed V2 of the next row material is calculated by the next row material setting value calculation device ( 13), it is calculated and determined using the following formula (2). V2 = F(H2, W2, Z
2)
...(2) 00019] Also, (2)
The furnace temperature setting value F2 of the next row material under the line speed V2 determined by the formula is calculated by the next row material set value calculation device (13) as follows (
3) Obtain by calculating using the formula. F2 = G (V2, H2,
W2, Z2, T2, ΦCG2)
...(3) Next, the timing of setting changes when changing from the line speed and furnace temperature of the preceding material to the line speed and furnace temperature of the next material is important for control, and the timing of these setting changes is important. Do calculations. A method of calculating this setting change timing will be explained using the time chart shown in FIG. 3. In the conventional method, the evaluation function E in equation (1) above is minimized so that the area outside the sheet temperature tolerance of the preceding material (c) and the area outside the sheet temperature tolerance of the next material (d) are minimized. However, in the method of the present invention, the sheet temperature tolerance priority determination device (14) determines which of the preceding material and the following material has priority based on the sheet thickness, target sheet temperature, and sheet temperature tolerance ( For example, if the preceding material is given priority, the preceding material's sheet temperature tolerance length L1 is zero and the sheet temperature tolerance length L2 of the next material is the minimum. If the next material has priority, the sheet temperature tolerance length L2 of the next row material is zero and the sheet temperature tolerance length L1 of the preceding material is the minimum. The plate temperature response curve is predicted and calculated so that the necessary "timing for changing the line speed V1 of the preceding material to the line speed V2 of the next material" and the "furnace temperature F of the preceding material" are calculated.
1 to the next material's furnace temperature F2 is calculated. In other words, as shown in the following equation (4), an optimization problem in which the evaluation function L is minimized under the constraint conditions is calculated. of"
By solving the problem using "Nonlinear Optimization Numerical Computation Method," the optimal timing for changing the line speed and furnace temperature settings can be determined. L (evaluation function) = P2 L1
+P1 L2...
...(4) At this time, the line speed can be changed by the maximum acceleration/deceleration rate determined by the capacity of the bridle roll drive motor, and the furnace temperature can be changed by a first-order lag waveform determined by the heat capacity of the furnace. It is similar to the conventional method in that the predictive calculation is performed assuming that it is possible. [00024] Furthermore, the parameter P1 of the above equation (4)
, P2 is determined by the plate temperature tolerance priority determination device (14) based on the plate thicknesses of the preceding material and the succeeding material, the target plate temperature, and the plate temperature tolerance, as shown in the flowchart of FIG. 5, for example. Determined according to criteria. Furthermore, the welding point position tracking device (11) shown in FIG. 1 constantly tracks the welding position between the preceding material and the succeeding material, and this welding point position is determined at the timing of changing the line speed or furnace temperature setting. When passing the corresponding position, the setting command device (15) outputs a speed change command and a furnace temperature change command to the speed control device (9) and the furnace temperature control device (5), respectively. In response to this, the speed control device (9) controls the speed of the drive motor (7) to match the set speed, and the furnace temperature control device (5) controls the fuel flow rate so that the furnace temperature matches the set value. A control device (4) operates the fuel flow rate supplied into the furnace. [00026] In this way, when the preceding strip and the succeeding strip, which have different dimensions, target plate temperatures, materials, etc., are welded together and are continuously heat-treated in a continuous annealing furnace, the plate thickness and the predetermined target plate temperature are The priority of appropriate processing of the preceding strip and the following strip is determined based on the strip temperature tolerance and the strip temperature tolerance, and the strip temperature deviation length from the strip temperature tolerance of the priority strip is zero and the strip temperature of the non-priority material is determined. We predict and calculate the "plate temperature response curve from the preceding material to the next material" where the length of the deviation of the plate temperature from the tolerance is the minimum value, and the timing of changing the line speed and furnace temperature settings to achieve this. If control is performed based on this, it will be possible to perform extremely accurate temperature control that has never been seen before. [Summary of Effects] As explained above, according to the present invention, it is possible to provide a continuous annealing furnace control method that can accurately and stably control the temperature of a steel plate without requiring particularly difficult and complicated operations. , industrially extremely useful effects are brought about.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an example of a temperature control method according to the present invention.

[Fig. 2] Flowchart showing the temperature control process according to the present invention.
It is.

FIG. 3 is a time chart of the previously proposed method.

FIG. 4 is a flowchart showing a procedure for changing operating conditions in the previously proposed method.

[Explanation of symbols]

a Upper limit of plate temperature tolerance b Lower limit of plate temperature tolerance c Area outside the plate temperature tolerance of the preceding material d Area outside the plate temperature tolerance of the succeeding material 1 Continuous annealing furnace heating zone 2 Hearth roll 3 Furnace temperature detector 4 Fuel flow control Device 5 Furnace temperature control device 6 Plate temperature detector 7 Drive motor 8 Bridle roll 9 Speed control device 10 Welding point detector 11 Welding point position tracking device 12 Line speed/furnace temperature setting change timing calculation device 13 Next line Material setting calculation device 14 Plate temperature tolerance deviation length specification device 15 Setting command device

Claims (1)

[Claims] Claim 1: When continuously processing a preceding material and a subsequent material under different conditions in a continuous annealing furnace equipped with a line speed control device and a furnace temperature control device, Based on the temperature tolerance, it is determined which of the preceding material and the following material has priority, and the "
Sheet temperature response curve from the preceding material to the succeeding material where the "length of the sheet temperature deviation from the sheet temperature tolerance" is zero and the "length of the sheet temperature deviation from the sheet temperature tolerance" of the non-priority side material is the minimum value. A method for controlling the temperature of a steel plate in a continuous annealing furnace, which is characterized by predicting and calculating the timing of setting changes in line speed and furnace temperature for that purpose, and controlling the line speed and furnace temperature respectively based on this.