JP6784182B2 - Steel plate temperature control method and steel sheet temperature control device - Google Patents

Description

The present invention relates to a steel sheet temperature control method and a steel sheet temperature control device.

Generally, a continuous annealing facility for steel sheets is composed of a heating furnace, a soaking furnace, a cooling furnace, etc., and on the entrance side of the facility, the tail end of the preceding material having different sizes, specifications, and annealing conditions such as plate thickness and plate width. And the tip of the trailing material are welded together to form a single steel sheet that is continuously processed. Here, in the heating furnace, the goal is to perform heat treatment so as to be suitable for each annealing condition by switching the furnace temperature set value of each heating zone before and after the welded portion. Finally, on the exit side of the equipment, the steel sheet is cut in coil units and shipped, or is transported to the next process.

In a heating furnace, it is common to raise the temperature of the steel sheet by radiant heating using a radiant tube, but if the size of the steel sheet differs at the welded part, the heating conditions will be the same before and after that. The temperature of the steel sheet fluctuates.

In Patent Document 1, an induction heating device is arranged on the inlet side of the heating furnace, and the heating furnace exit side plate temperature predicted when the heating conditions are changed, the line speed (plate passing speed), and the inlet derived according to the operating conditions. The amount of change in the temperature of the steel plate required for heating by the induction heating device is calculated based on the residual rate of heat input, and the output of the induction heating device is changed based on the calculation result to change the temperature of the plate on the exit side of the heating furnace. A method for controlling the temperature of a steel plate to be reduced is disclosed.

Japanese Unexamined Patent Publication No. 2005-298941

The wasted time, which is a parameter that characterizes the plate temperature change with respect to the plate thickness change, gas flow rate change, and line speed change due to the change in heating conditions, depends on the line speed (plate passing speed). This wasted time is the time until the effects of changes in plate thickness, gas flow rate, line speed, etc. appear on the plate temperature. During this time, the temperature of the steel plate on the inlet side of the heating furnace is changed by an induction heating device. However, there is no effect on the temperature of the steel sheet on the outlet side of the heating furnace.

However, in the steel sheet temperature control method disclosed in Patent Document 1, since the steady speed after the line speed change is completed is used as the line speed used when calculating the steel plate temperature change amount, wasted time has elapsed. The plate temperature on the exit side of the heating furnace will fluctuate greatly during the subsequent line speed change.

The present invention has been made in view of the above problems, and an object of the present invention is a method for controlling the temperature of a steel sheet capable of reducing fluctuations in the temperature of the plate on the exit side of the heating furnace while changing the line speed, and controlling the temperature of the steel sheet. To provide the device.

In order to solve the above-mentioned problems and achieve the object, the method for controlling the temperature of a steel plate according to the present invention has a plurality of heating zones in which an induction heating device is arranged on the entrance side and arranged along the plate passing direction of the steel plate. A plate temperature measurement process that measures the temperature of the steel plate on the outlet side of the heating furnace, a furnace temperature measurement process that measures the furnace temperature of each heating zone, and a line speed change that changes the line speed based on the line speed change command. process and the toward change end from the line speed of the change start, for a plurality of positions set at predetermined intervals in the through plate direction of the steel sheet being dumped in the heating furnace, traveling time for each of the heating zones Using the passage time prediction step for predicting the passage time, the passage time prediction result for the plurality of positions predicted by the passage time prediction step, and the furnace temperature measurement value at the current time measured by the furnace temperature measurement step, The temperature of the steel plate on the outlet side of the induction heating device so that the steel plate does not change on the outlet side of the heating furnace is calculated using a plate temperature calculation model formula capable of calculating the temperature of the steel plate in the heating furnace. Induction heating output change to change the output of the induction heating device so that it becomes the temperature of the steel plate on the exit side of the induction heating device calculated by the induction heating output side plate temperature calculation step and the induction heating output side plate temperature calculation step. has a step, and in the transit time prediction step determines the delivery side speed of the input side speed and the final heating zone of the heating zone used in predicting the traveling time for each of the heating zones, the input of each heating zone The lateral speed is characterized in that it is obtained separately for the case during acceleration / deceleration and the case after completion of acceleration / deceleration.

Further, in the steel plate temperature control device according to the present invention, an induction heating device is arranged on the entrance side, and the temperature of the steel plate on the exit side of a heating furnace having a plurality of heating zones arranged along the plate passing direction of the steel plate is measured. A plate temperature measuring unit for measuring, a furnace temperature measuring unit for measuring the furnace temperature of each heating zone, a line speed changing unit for changing the line speed based on a line speed change command, and a change end from the start of the line speed change. A passage time prediction unit that predicts the passage time of each heating zone with respect to a plurality of positions set at predetermined intervals in the plate passage direction on the steel plate charged in the heating furnace , and the passage time. The change of the steel plate on the outlet side of the heating furnace occurs by using the passing time prediction result for the plurality of positions obtained by the prediction unit and the furnace temperature measurement value at the current time measured by the furnace temperature measurement unit. The induction heating outlet plate temperature calculation unit that calculates the temperature of the steel plate on the outlet side of the induction heating device, which does not exist, using a plate temperature calculation model formula that can calculate the temperature of the steel plate in the heating furnace, and the induction heating It has an induction heating output changing unit that changes the output of the induction heating device so as to be the temperature of the steel plate on the exit side of the induction heating device calculated by the exit side plate temperature calculation unit, and the passage time prediction unit. obtains an output side speed of the input side speed and the final heating zone of the heating zone used in predicting the traveling time for each of the heating zones, acceleration and deceleration completion in the case of entry-side speed during acceleration and deceleration of each heating zone It is characterized in that it is obtained separately for the later case.

The steel sheet temperature control method and the steel sheet temperature control device according to the present invention have the effect of being able to reduce fluctuations in the temperature of the plate on the exit side of the heating furnace while changing the line speed.

FIG. 1 is a block diagram showing a configuration of a temperature control device for a steel plate according to an embodiment. FIG. 2 is a graph showing an example of a velocity pattern in the i-th heating zone. FIG. 3 is a diagram showing a flow of convergence calculation of the induction heating exit side plate temperature by Newton's method. FIG. 4 is a block diagram showing a configuration of a temperature control device for a steel plate in a conventional method. FIG. 5A is a graph showing the line speed in the method of the present invention and the conventional method. FIG. 5B is a graph showing the induction heating output side plate temperature in the method of the present invention and the conventional method. FIG. 5C is a graph showing the temperature on the exit side of the heating furnace in the method of the present invention and the conventional method.

Hereinafter, a method for controlling the temperature of the steel sheet according to the present invention and an embodiment of the temperature control device for the steel sheet will be described. The present invention is not limited to the present embodiment.

FIG. 1 is a block diagram showing a configuration of a temperature control device 1 for a steel plate according to an embodiment. As shown in FIG. 1, the temperature control device 1 for the steel plate according to the embodiment has N (≧ 1) pieces arranged along the sheet passing direction of the steel plate (in the present embodiment, the first heating zone to the fifth heating zone). This is a device for controlling the temperature of a steel sheet in a continuous annealing facility including a heating furnace having a heating zone (5) and an induction heating device 2 provided on the entrance side of the heating furnace. Although FIG. 1 illustrates a heating furnace having five heating zones, the present invention can be applied to any heating furnace having one or more heating zones.

The steel plate temperature control device 1 includes a plate temperature measuring unit 11, a line speed changing unit 12, a furnace temperature measuring unit 13, a passing time prediction unit 14, an induction heating output side plate temperature calculation unit 15, an induction heating output changing unit 16, and the like. Is provided as the main component.

Here, a temperature rise model formula in a heating furnace will be described. The calculation of the temperature rise of the steel plate in the heating furnace can be calculated according to the equation of the equation (1). In the numerical calculation, the following equation (1) is discretized in an appropriate time step Δt and the difference is calculated. In the following equation (1), ρ is the specific heat of the steel sheet [kcal / kg / K], C is the specific gravity of the steel sheet [kg / m ³ ], h is the thickness of the steel sheet [m], and T _s is the temperature of the steel sheet [° C. ], T _w is the furnace temperature [° C], φ _cg is the overall heat transfer coefficient [-], σ is the Stefan-Boltzmann constant (= 1.3565e ^-11 [kcal / s / m ² / K ⁴ ]], t is the time [ s] is shown.

Then, in a heating furnace having a plurality of heating zones, the plate temperature from the heating furnace entry side to the heating furnace exit side can be calculated by setting the furnace temperature for each heating zone. Here, the initial plate temperature may be set to the temperature on the heating zone entry side.

The line speed change unit 12 receives the line speed change command output from the process computer 3 and changes the line speed. Similarly, the transit time prediction unit 14 receives the line speed change command output from the process computer 3 at the line speed change command timing to the line speed change unit 12. Then, transit time prediction unit 14, by the procedure 1 to procedure 5 below, toward change end from change start line speed by the line speed changing unit 12, the sheet passing direction position of the steel sheet to be charged in the furnace (the longitudinal position ), The transit time of each heating zone is predicted for a plurality of positions including at least two points , the position at the start of the line speed change and the position at the end of the line speed change. Further, description on the plurality of positions to be predicted transit time, in line speed change starting point, position the sheet passing direction position of the steel sheet to be charged in the furnace (longitudinal position) 0 (k = 0), and at the end of the line speed change , the position (longitudinal position) of the steel plate charged in the heating furnace is set to position N (k = N), and N points from position 0 to position N at equal intervals. It is divided into .

First, as step 1, the time t _acc [s] from the start of acceleration / deceleration to the completion of acceleration / deceleration is obtained using the following equation (2). In the following equation (2), α indicates the acceleration rate [m / s ² ], and dV indicates the speed change amount [m / s].

In the following steps 2 to 5, the calculation is performed for k = 0, 1, 2, ... N.

Next, as step 2, the initial velocity V ₀ (k) [m / s] for induction heating calculation at k = 1, 2, ... N is obtained using the following equation (3). In the following equation (3), V ₀ indicates the speed before acceleration / deceleration [m / s], and N indicates the induction heating calculation division number [-].

Next, as step 3, the acceleration / deceleration distance l (k) [m], which is the distance from the start of acceleration / deceleration to the completion of acceleration / deceleration at the kth steel plate position, is obtained using the following equation (4).

Next, as step 4, the i-th heating zone entry speed and the final heating zone exit speed are obtained.

First, the entry speed V (1, k) [m / s] of the first heating zone at the k-th steel plate position can be obtained by the following equation (5).

Next, the entry speed V (i, k) [m / s] of the i-th heating zone (2 ≦ i ≦ 5) at the k-th steel plate position is obtained separately for during acceleration / deceleration and after completion of acceleration / deceleration. .. In the following equations (6) to (8), L _z (j) indicates the section distance (j = 1 to 5) which is the equipment length in the plate passing direction of each heating zone.

First, the entry speed V (i, k) [m / s] of the i-th heating zone (2 ≦ i ≦ 5) during acceleration / deceleration of the line speed satisfying the relationship of the following equation (6) is determined by the following (7). Obtained by the formula.

On the other hand, the entry speed V (i, k) of the i-th heating zone (2 ≦ i ≦ 5) after the acceleration / deceleration of the line speed satisfying the relationship of the following formula (8) is completed can be obtained by the following formula (9).

The final heating zone exit speed (fifth heating zone exit speed) is the same as the entry speed V (i, k) of the i-th heating zone (2 ≦ i ≦ 5) after the acceleration / reduction of the line speed is completed. Therefore, it can be obtained by the above equation (9).

Next, as step 5, the transit time of the i-th heating zone is obtained.

FIG. 2 is a graph showing an example of a velocity pattern in the i-th heating zone. In the velocity pattern in the i-th heating zone as shown in FIG. 2, it is considered that the passage time t (i, k) [s] at which the k-th steel plate position passes through the i-th heating zone is obtained. This transit time t (i, k) [s] can be obtained by the sum of the acceleration time t ₁ and the constant velocity time t ₂ in the i-th heating zone. Note that in step 4, the i-th heating zone entry speed and the final heating zone exit speed are calculated.

First, the acceleration distance x ₁ [m], which is the distance in the section of the acceleration time t ₁ [s] in the i-th heating zone shown in FIG. 2, can be obtained by the following equation (10).

Next, the constant velocity distance x ₂ [m], which is the distance in the section of the constant velocity time t ₂ [s] in the i-th heating zone shown in FIG. 2, can be obtained by the following equation (11).

Here, the section distance L _z (i) of the i-th heating zone (1 ≦ i ≦ 5) in the heating furnace is given by the equipment length in the plate-passing direction of each heating zone as described above, and is given by the following ( The constant velocity time t ₂ [s] can be obtained by the equation 12).

In the present embodiment, the section distance L _z (i) of the i-th heating zone (1 ≦ i ≦ 5) is the section distance L _z (1) = 20.4 [m] of the first heating zone. 2 section distance L _z (2) = 5.1 [m] of the heating zone, section distance L _z (3) = 5.1 [m] of the third heating zone, section distance L _z (4) of the fourth heating zone ) = 5.1 [m], and the section distance L _z (5) of the fifth heating zone is given as 5.1 [m].

Further, the acceleration time t ₁ [s] can be obtained by the following equation (13).

From the sum of the acceleration time t ₁ [s] in the i-th heating zone and the constant velocity time t ₂ [s] obtained in this way, the i-th heating zone transit time t (i, k) [s] can be obtained. ..

Subsequently, the induction heating output side plate temperature calculation unit 15 will be described. The induction heating outlet side plate temperature calculation unit 15 obtains the plate temperature on the outlet side of the induction heating device that minimizes the fluctuation of the plate temperature on the outlet side of the heating furnace. The plate temperature measuring unit 11 measures the plate temperature on the heating furnace outlet side at the line speed change command timing, and transmits the measured plate temperature value to the induction heating outlet side plate temperature calculating unit 15. Further, the furnace temperature measuring unit 13 measures the actual value of the furnace temperature of each heating zone in the heating furnace at the line speed change command timing, and transmits the measured actual value to the induction heating output side plate temperature calculating unit 15. .. In addition, the induction heating output side plate temperature calculation unit 15 also receives the prediction result of the passage time of each heating zone from the passage time prediction unit 14.

Here, the calculated value of the plate temperature on the exit side of the heating furnace at the k-th steel plate position is T ₀ = f ( _TIH , t (i, k), _TW (i), ρ, C, H, φ _CG , σ). It is represented by. The function f is a temperature rise model formula based on the mathematical formula (1). Further, _TIH is the induction heating exit side plate temperature (initial value of plate temperature calculation). Further, _TW (i) is a furnace temperature measured value (measured value by the furnace temperature measuring unit 13) of each heating zone.

FIG. 3 is a diagram showing a flow of convergence calculation of the induction heating exit side plate temperature by Newton's method. The induction heating output side plate temperature calculation unit 15 uses the Newton method shown in FIG. 3 to perform convergence calculation so that the calculation value T ₀ of the _output side plate temperature of the heating furnace is within an error ε [° C.] with respect to the _output side plate temperature target value T _aim . To obtain the calculated value of the induction heating output side plate temperature.

That is, in the convergence calculation of the induction heating output side plate temperature by the Newton method by the induction heating output side plate temperature calculation unit 15, first, "1" is substituted into the variable "Loop" indicating the number of convergence calculations (S1), and the induction heating output is performed. the initial value of the induction heating delivery temperature to the variable "T _{the IH"} indicating side temperature assigns "T _IH0" (S2). Next, the induction heating output side plate temperature calculation unit 15 calculates the heating furnace output side plate temperature calculation value T ₀ , and substitutes “Loop + 1” into the variable “Loop” (S3). Then, in the induction heating output side plate temperature calculation unit 15, the variable "Loop" is set in advance so that the calculation value T ₀ of the _output side plate temperature of the heating furnace is within an error ε [° C.] with respect to the _output side plate temperature target value T _aim . It is determined whether the number of times exceeds n times (S4). The _output side plate temperature target value T _aim may be a value measured by the plate temperature measuring unit 11 or a heating furnace exit side plate temperature calculated value obtained from the line speed before acceleration.

If the calculated value T ₀ of the outside plate temperature of the heating furnace is not within the error ε [° C] with respect to the target value T _{aim of the output} side plate temperature, or if the variable “Loop” does not exceed the preset n times, the induction heating is performed. When the side plate temperature calculation unit 15 determines (No in S4), the induction heating output side plate temperature calculation unit 15 uses the Newton method to make the heating furnace output side plate temperature calculation value T ₀ an error ε with respect to the _output side plate temperature target value T _aim [ Convergence calculation is performed so as to be within [° C.] (S5). Then, when the calculated value T ₀ of the outside plate temperature of the heating furnace converges within an error ε [° C.] with respect to the target value T _{aim of the output} side plate temperature, or when the variable “Loop” exceeds the preset n times, induction heating is performed. When the output side plate temperature calculation unit 15 determines (Yes in S4), the induction heating output side plate temperature calculation unit 15 ends the convergence calculation of the induction heating output side plate temperature by the Newton method.

Then, the calculated value of the induction heating output side plate temperature in the convergence calculation at that time is transmitted from the induction heating output side plate temperature calculation unit 15 to the induction heating output changing unit 16, and the induction heating output changing unit 16 outputs the output of the induction heating device 2. To change. The plate temperature calculation model formula in the induction heating output side plate temperature calculation unit 15 is the measured value of the plate temperature predicted value obtained by inputting the line speed at the current time and the furnace temperature measurement value as the input of the plate temperature calculation model formula. It may be corrected by an error.

[Example]
The effectiveness of the method of the present invention (the method for controlling the temperature of the steel sheet according to the embodiment) was verified by simulation. The set values of each heating zone are shown in Table 1 below, and the set values of the steel sheet are shown in Table 2 below. The speed change amount dV is 0.05 [m / s], and the acceleration rate α is 8.3333e ^-4 [m / s ² ]. Then, the induction heating calculation division number N, which is a design parameter, was set to 5.

Further, for comparison with the method of the present invention using the temperature control device 1 for the steel sheet shown in FIG. 1, a block diagram showing the configuration of the temperature control device for the steel sheet in the conventional method is shown in FIG. As shown in FIG. 4, the temperature control device 100 for a steel sheet in the conventional method includes a heating furnace having five heating zones (first heating zone to fifth heating zone) arranged along the sheet passing direction of the steel sheet. This is a device for controlling the temperature of a steel sheet in a continuous annealing facility provided with an induction heating device 102 provided on the entry side of the heating furnace. The steel plate temperature control device 100 in the conventional method mainly includes a plate temperature measuring unit 111, a line speed changing unit 112, a furnace temperature measuring unit 113, an induction heating output side plate temperature calculating unit 115, an induction heating output changing unit 116, and the like. It is provided as a component. On the other hand, the steel sheet temperature control device 100 in the conventional method does not include a device corresponding to the transit time prediction unit 14 included in the steel sheet temperature control device 1 in the method of the present invention. Therefore, the induction heating output side plate temperature calculation unit 115 does not consider the state during acceleration / deceleration of the line speed, and uses the line speed change completion speed to determine the induction heating output side plate temperature that can reduce the fluctuation of the heating furnace exit side plate temperature. It shall be sought. A line speed change command is output from the process computer 103 to the line speed change unit 103 and the induction heating output side plate temperature calculation unit 115.

FIG. 5A is a graph showing the line speed in the method of the present invention and the conventional method. FIG. 5B is a graph showing the induction heating output side plate temperature in the method of the present invention and the conventional method. FIG. 5C is a graph showing the temperature on the exit side of the heating furnace in the method of the present invention and the conventional method.

As shown in FIG. 5A, the line speed is changed in the same manner in the method of the present invention and the conventional method, and the change of the line speed is completed around 65 [s]. In FIG. 5B, in the conventional method, the induction heating output side plate temperature is set by using the steady speed after the line speed change is completed, whereas in the method of the present invention, the line speed is being accelerated / decelerated and accelerated / decelerated. Based on the speed prediction after completion, the induction heating output side plate temperature is set at a plurality of steel plate positions.

In the method of the present invention and the conventional method, as shown in FIG. 5C, there is wasted time up to around 45 [s]. Then, in the method of the present invention, the plate temperature on the exit side of the heating furnace has converged to the target value immediately after the wasted time has elapsed. On the other hand, in the conventional method, the heating furnace outlet side plate temperature does not converge to the target value even after 100 [s], and the method of the present invention has better convergence of the heating furnace outlet side plate temperature than the conventional method. I understand. As described above, in the method of the present invention, it is possible to reduce the fluctuation of the plate temperature on the exit side of the heating furnace during the change of the line speed after the lapse of wasted time, as compared with the conventional method.

1 Temperature control device 2 Induction heating device 3 Process computer 11 Plate temperature measurement unit 12 Line speed change unit 13 Furnace temperature measurement unit 14 Passing time prediction unit 15 Induction heating output side plate temperature calculation unit 16 Induction heating output change unit

Claims (2)

An induction heating device is arranged on the entrance side, and a plate temperature measuring step for measuring the temperature of the steel plate on the exit side of a heating furnace having a plurality of heating zones arranged along the plate passing direction of the steel plate, and
A furnace temperature measurement process that measures the furnace temperature in each heating zone,
The line speed change process that changes the line speed based on the line speed change command,
Toward change end from change start of the line speed, to a plurality of positions set at predetermined intervals in the through plate direction of the steel sheet being dumped in the heating furnace, predicts the traveling time for each of the heating zones Transit time prediction process and
Using the passing time prediction results for the plurality of positions predicted by the passing time prediction step and the furnace temperature measurement value at the current time measured by the furnace temperature measuring step, the steel plate on the outlet side of the heating furnace The induction heating outlet side plate temperature calculation step of calculating the temperature of the steel plate on the outlet side of the induction heating device so that no change occurs using a plate temperature calculation model formula capable of calculating the temperature of the steel plate in the heating furnace, and
An induction heating output changing step of changing the output of the induction heating device so as to be the temperature of the steel plate on the exit side of the induction heating device calculated by the induction heating output side plate temperature calculation step.
Have,
In the transit time prediction step,
Seeking and exit side speed of the input side speed and the final heating zone of the heating zone used in predicting the traveling time for each of the heating zones, after when the acceleration or deceleration completion in the entry-side speed during acceleration and deceleration of each heating zone A method for controlling the temperature of a steel sheet, which is characterized in that it is obtained separately for each case. An induction heating device is arranged on the entrance side, and a plate temperature measuring unit for measuring the temperature of the steel plate on the exit side of a heating furnace having a plurality of heating zones arranged along the plate passing direction of the steel plate.
A furnace temperature measuring unit that measures the furnace temperature in each heating zone,
A line speed change unit that changes the line speed based on the line speed change command,
Toward change end from change start of the line speed, to a plurality of positions set at predetermined intervals in the through plate direction of the steel sheet being dumped in the heating furnace, predicts the traveling time for each of the heating zones Transit time prediction unit and
Using the passing time prediction results for the plurality of positions obtained by the passing time prediction unit and the furnace temperature measurement value at the current time measured by the furnace temperature measuring unit, the steel plate on the exit side of the heating furnace An induction heating output side plate temperature calculation unit that calculates the temperature of the steel plate on the outlet side of the induction heating device so that no change occurs using a plate temperature calculation model formula that can calculate the temperature of the steel plate in the heating furnace.
An induction heating output changing unit that changes the output of the induction heating device so that the temperature of the steel plate on the exit side of the induction heating device is calculated by the induction heating output side plate temperature calculation unit.
Have,
The transit time prediction unit
Seeking and exit side speed of the input side speed and the final heating zone of the heating zone used in predicting the traveling time for each of the heating zones, after when the acceleration or deceleration completion in the entry-side speed during acceleration and deceleration of each heating zone A temperature control device for a steel sheet, which is characterized in that it is obtained separately for each case.

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