JP2018123364A - Steel plate temperature control method and steel plate temperature control device - Google Patents

Abstract

An object of the present invention is to provide a temperature control method for a steel plate and a temperature control device for a steel plate that can reduce fluctuations in plate temperature on the outlet side of a heating furnace during line speed changes. [Solution] A steel plate temperature control method includes a plate temperature measurement step of measuring the steel plate temperature at the exit side of a heating furnace which has a plurality of heating zones in which an induction heating device is placed on the inlet side, and a furnace temperature of each heating zone. A furnace temperature measurement process to measure, a line speed change process to change the line speed, and a passing process to predict the passing time of each heating zone for multiple positions in the steel plate threading direction from the start to the end of changing the line speed. Using the time prediction process, the predicted passage time prediction result, and the furnace temperature measurement value at the current time, the steel plate temperature at the exit side of the induction heating device is calculated so that no change in steel plate temperature occurs at the exit side of the heating furnace. , an induction heating exit side plate temperature calculation step of calculating using a plate temperature calculation model formula, and an induction heating output changing step of changing the output of the induction heating device so as to achieve the calculated steel plate temperature. [Selection diagram] Figure 1

Description

  The present invention relates to a steel plate temperature control method and a steel plate temperature control apparatus.

  In general, continuous annealing equipment for steel sheets is composed of a heating furnace, a soaking furnace, a cooling furnace, etc., and on the entry side of the equipment, the tail end of the preceding material with different sizes, standards, and annealing conditions such as plate thickness and width And the front-end | tip part of a succeeding material is welded, and a process is continuously performed as one steel plate. Here, in a heating furnace, it is a goal to heat-process so that it may suit each annealing condition by switching the furnace temperature setting value of each heating zone before and behind a welding part. Finally, on the exit side of the facility, the steel sheet is cut and shipped in units of coils or is transported to the next process.

  In a heating furnace, it is common to raise the temperature of a steel sheet by radiant heating using a radiant tube, but in a situation where the size of the steel sheet is different at the weld, the heating conditions are the same before and after that. Variations occur in the temperature of the steel sheet.

  In Patent Document 1, an induction heating device is arranged on the entrance side of the heating furnace, and the heating furnace outlet side plate temperature predicted when the heating conditions are changed, the line speed (plate passing speed), and the inlet derived from the operating conditions. By calculating the amount of steel plate temperature change required for heating with the induction heating device based on the residual rate of heat input, and changing the output of the induction heating device based on the calculation result, the fluctuation of the heating furnace outlet side plate temperature can be reduced. A method for controlling the temperature of a steel sheet to be reduced is disclosed.

JP 2005-298951 A

  The dead time that is a parameter characterizing the plate temperature change with respect to the plate thickness change, the gas flow rate change, and the line speed change due to the change of the heating condition depends on the line speed (plate feed speed). This dead time is the time until the influence of plate thickness change, gas flow rate change, line speed change, etc. appears in the plate temperature. During this time, the temperature of the steel plate on the inlet side of the heating furnace is changed by the induction heating device. However, there is no effect on the temperature of the steel plate on the exit side of the heating furnace.

  However, in the temperature control method of the steel sheet disclosed in Patent Document 1, the dead time has elapsed since the steady speed after completion of the line speed change is used as the line speed used when calculating the steel plate temperature change amount. A large fluctuation occurs in the heating furnace outlet side plate temperature during the subsequent line speed change.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is a steel plate temperature control method capable of reducing fluctuations in the heating furnace outlet side plate temperature during the line speed change, and the temperature control of the steel plate. Is to provide a device.

  In order to solve the above-described problems and achieve the object, the steel sheet temperature control method according to the present invention includes a plurality of heating zones in which an induction heating device is arranged on the entry side and arranged along the sheet passing method. A plate temperature measuring step for measuring the temperature of the steel plate on the outlet side of the heating furnace, a furnace temperature measuring step for measuring the furnace temperature in each heating zone, and a line speed change for changing the line speed based on a line speed change command A plurality of steps including a line speed change start time point and a line speed change end time point among the steps in the sheet passing direction of the steel sheet charged into the heating furnace from the start of change of the line speed to the end of change. A passage time prediction step for predicting a passage time of each heating zone with respect to a position; a passage time prediction result for the plurality of positions predicted by the passage time prediction step; and a furnace temperature measurement step. The temperature of the steel plate on the exit side of the induction heating device so as not to cause a change in the steel plate on the exit side of the heating furnace is measured in the heating furnace. An induction heating outlet side plate temperature calculation step that is calculated using a plate temperature calculation model that can calculate the temperature of the steel plate, and a temperature of the steel plate on the outlet side of the induction heating device calculated by the induction heating outlet side plate temperature calculation step The induction heating output changing step for changing the output of the induction heating device is provided.

  Further, in the temperature control method for a steel sheet according to the present invention, in the above invention, the plate temperature calculation model formula is obtained by using the current line speed and the furnace temperature measurement value as inputs of the plate temperature calculation model formula. The correction is made with an error from the measured value of the steel plate temperature predicted value.

  Moreover, the temperature control device for a steel sheet according to the present invention is configured such that the induction heating device is disposed on the entry side, and the temperature of the steel sheet on the exit side of the heating furnace having a plurality of heating zones disposed along the sheet passing method. A plate temperature measuring unit for measuring, a furnace temperature measuring unit for measuring the furnace temperature in each heating zone, a line speed changing unit for changing the line speed based on a line speed change command, and a change from the start of changing the line speed to the end of the line speed Among the plurality of positions including at least two points of the line speed change start time and the line speed change end time among the sheet passing direction positions of the steel sheet charged into the heating furnace, Using the predicted passage time prediction unit, the passage time prediction results for the plurality of positions obtained by the passage time prediction unit, and the current furnace temperature measurement value measured by the furnace temperature measurement unit, Induction to calculate the temperature of the steel plate on the exit side of the induction heating device so that the steel plate does not change on the exit side of the heating furnace using a plate temperature calculation model that can calculate the temperature of the steel plate in the heating furnace. A heating output side plate temperature calculation unit and an induction heating output change unit that changes the output of the induction heating device so as to be the temperature of the steel sheet on the output side of the induction heating device calculated by the induction heating output side plate temperature calculation unit It is characterized by having.

  In the steel sheet temperature control apparatus according to the present invention, in the above invention, the plate temperature calculation model formula is obtained as the input of the plate temperature calculation model formula at the current line speed and the furnace temperature measurement value. It is corrected by an error from the measured value of the steel plate temperature predicted value.

  The steel plate temperature control method and the steel plate temperature control device according to the present invention have the effect of reducing fluctuations in the heating furnace outlet side plate temperature during line speed change.

FIG. 1 is a block diagram illustrating a configuration of a steel sheet temperature control apparatus according to an embodiment. FIG. 2 is a graph showing an example of a speed pattern in the i-th heating zone. FIG. 3 is a diagram showing a convergence calculation flow of the induction heating outlet side plate temperature by the Newton method. FIG. 4 is a block diagram showing a configuration of a steel sheet temperature control device 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.5 (b) is a graph which shows the induction heating exit side plate | board temperature in this invention method and the conventional method. FIG.5 (c) is a graph which shows the heating furnace exit side temperature in this invention method and the conventional method.

  Hereinafter, an embodiment of a temperature control method for a steel sheet and a temperature control apparatus for a steel sheet according to the present invention will be described. In addition, this invention is not limited by this embodiment.

  FIG. 1 is a block diagram illustrating a configuration of a steel sheet temperature control apparatus 1 according to the embodiment. As shown in FIG. 1, the steel sheet temperature control apparatus 1 according to the embodiment includes N (≧ 1) pieces (in the present embodiment, the first heating zone to the fifth heating zone) arranged along the plate passing direction of the steel plate. 5) of the heating furnace and the induction heating apparatus 2 provided on the heating furnace entrance side, the apparatus controls the temperature of the steel sheet in the continuous annealing equipment. 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 passage time predicting unit 14, an induction heating outlet side plate temperature calculating unit 15, an induction heating output changing unit 16, and the like. As a main component.

Here, the temperature rise model formula in the heating furnace will be described. The temperature increase calculation of the steel sheet temperature in the heating furnace can be calculated according to the equation (1). In numerical calculation, the following equation (1) is discretized at an appropriate time step Δt and the difference is calculated. In the following formula (1), ρ is the specific heat of the steel plate [kcal / kg / K], C is the specific gravity of the steel plate [kg / m ³ ], h is the thickness of the steel plate [m], and T _s is the temperature of the steel plate [° 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 ], and t is the time [ s].

  And in the heating furnace which has a some heating zone, the plate | board temperature from a heating furnace entrance side to a heating furnace exit side can be calculated by setting the furnace temperature for every heating zone. Here, the initial plate temperature may be set to the temperature at 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 passage 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. And the passage time prediction unit 14 follows the following procedure 1 to procedure 5 from the start of the change of the line speed by the line speed change unit 12 to the end of the change in the sheet passing direction position (longitudinal position) of the steel sheet charged in the heating furnace. ), The passage time of each heating zone is predicted for a plurality of positions including at least two points of the line speed change start time and the line speed change end time. Further, for the sake of explanation, the plurality of positions to be predicted for the passage time are N points at equal intervals from the start of change of the line speed to the end of change.

First, as procedure 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 represents the acceleration rate [m / s ² ], and dV represents the speed change amount [m / s].

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

Next, as procedure 2, the following initial speed V ₀ (k) [m / s] for induction heating calculation at k = 1, 2,. In the following equation (3), V ₀ represents the speed before acceleration / deceleration [m / s], and N represents the induction heating calculation division number [−].

  Next, as the procedure 3, the following equation (4) is used to obtain an acceleration / deceleration distance l (k) [m] that is a distance from the acceleration / deceleration start to the acceleration / deceleration completion at the k-th steel plate position.

  Next, as procedure 4, an i-th heating zone entry speed and a final heating zone exit speed are obtained.

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

Next, the entry side 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 during acceleration / deceleration and after completion of acceleration / deceleration. . In addition, in the following formula (6) to the following formula (8), L _z (j) indicates a section distance (j = 1 to 5) which is the equipment length in the sheet passing direction of each heating zone.

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

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

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

  Next, as procedure 5, the passage time of the i-th heating zone is obtained.

FIG. 2 is a graph showing an example of a speed pattern in the i-th heating zone. In the speed pattern in the i-th heating zone as shown in FIG. 2, it is considered that the k-th steel plate position obtains a transit time t (i, k) [s] that passes through the i-th heating zone. This passage time t (i, k) [s] can be obtained by the sum of the acceleration time t ₁ and the constant speed time t ₂ in the i-th heating zone. It should be noted that the calculation is performed while paying attention that the i-th heating zone entry speed and the final heating zone exit speed are obtained in the procedure 4.

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

Next, the constant speed distance x ₂ [m], which is the distance of the constant speed time t ₂ [s] in the i-th heating zone shown in FIG. 2, is 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 from the equipment length in the sheet passing direction of each heating zone, as described above. The constant speed time t ₂ [s] is obtained from 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, Section distance L _z (2) = 5.1 [m] of the second 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] is obtained by the following equation (13).

The i-th heating zone passage time t (i, k) [s] is obtained from the sum of the acceleration time t ₁ [s] and the constant speed time t ₂ [s] in the i-th heating zone. .

  Next, the induction heating outlet side plate temperature calculation unit 15 will be described. The induction heating outlet side plate temperature calculation part 15 calculates | requires the plate | board temperature in the induction heating apparatus exit side from which a board temperature fluctuation | variation becomes the minimum on the heating furnace exit side. The plate temperature measuring unit 11 measures the plate temperature on the heating furnace exit side at the line speed change command timing, and transmits the measured plate temperature value to the induction heating exit side plate temperature calculating unit 15. Moreover, the furnace temperature measurement part 13 measures the actual value of the furnace temperature of each heating zone in a heating furnace in line speed change command timing, and transmits the measured actual value to the induction heating exit side plate temperature calculation part 15. . Further, the induction heating outlet 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 heating furnace outlet side plate temperature calculation value at the k-th steel plate position is T ₀ = f (T _IH , t (i, k), T _W (i), ρ, C, H, φ _CG , σ). Represented by The function f is a temperature increase model formula based on the formula (1). T _IH is the induction heating outlet side plate temperature (initial value of plate temperature calculation). T _W (i) is a furnace temperature measurement value (measurement value by the furnace temperature measurement unit 13) of each heating zone.

FIG. 3 is a diagram showing a convergence calculation flow of the induction heating outlet side plate temperature by the Newton method. The induction heating outlet side plate temperature calculation unit 15 performs convergence calculation so that the heating furnace outlet side plate temperature calculated value T ₀ is within an error ε [° C.] with respect to the outlet side plate temperature target value T _aim by the Newton method shown in FIG. Go to find the calculated value of the induction heating outlet side plate temperature.

That is, in the convergence calculation of the induction heating outlet side plate temperature by the Newton method by the induction heating outlet side plate temperature calculation unit 15, first, “1” is substituted into the variable “Loop” indicating the number of convergence calculations (S 1). The initial value “T _IH0 ” of the induction heating outlet side temperature is substituted into the variable “T _IH ” indicating the side temperature (S2). Next, the induction heating outlet side plate temperature calculation unit 15 calculates the heating furnace outlet side plate temperature calculation value T ₀ and assigns “Loop + 1” to the variable “Loop” (S3). The induction heating outlet side plate temperature calculation unit 15 determines whether the heating furnace outlet side plate temperature calculated value T ₀ is within an error ε [° C.] with respect to the outlet side plate temperature target value T _aim or a variable “Loop” is set in advance. It is determined whether it has exceeded n times (S4). Note that the _delivery side plate temperature target value T _aim may be a measurement value obtained by the plate temperature measurement unit 11 or a heating furnace delivery side plate temperature calculation value obtained from a line speed before acceleration.

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

  Then, the calculated value of the induction heating outlet side plate temperature in the convergence calculation at that time is transmitted from the induction heating outlet side plate temperature calculation unit 15 to the induction heating output change unit 16, and the induction heating output change unit 16 outputs the output of the induction heating device 2. To change. In addition, the plate temperature calculation model formula in the induction heating outlet side plate temperature calculation unit 15 is the measured value of the predicted plate temperature obtained by using the current line speed and the measured furnace temperature as the input of the plate temperature calculation model formula. You may correct with an error.

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

  For comparison with the method of the present invention using the steel sheet temperature control apparatus 1 shown in FIG. 1, a block diagram showing the structure of the steel sheet temperature control apparatus in the conventional method is shown in FIG. As shown in FIG. 4, a temperature control apparatus 100 for a steel plate in a conventional method includes a heating furnace having five heating zones (first heating zone to fifth heating zone) arranged along the plate passing direction of the steel plate. The apparatus for controlling the temperature of the steel sheet in the continuous annealing equipment provided with an induction heating device 102 provided on the heating furnace entrance side. The steel plate temperature control apparatus 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 outlet 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 according to the conventional method does not include a device corresponding to the transit time prediction unit 14 provided in the steel plate temperature control device 1 according to the present invention. Therefore, the induction heating outlet side plate temperature calculation unit 115 does not consider the state during the acceleration / deceleration of the line speed, and uses the line speed change completion speed to calculate the induction heating outlet side plate temperature that can reduce fluctuations in the heating furnace outlet side plate temperature. Suppose you want. A line speed change command is output from the process computer 103 to the line speed changing unit 103 and the induction heating outlet side plate temperature calculating unit 115.

  FIG. 5A is a graph showing the line speed in the method of the present invention and the conventional method. FIG.5 (b) is a graph which shows the induction heating exit side plate | board temperature in this invention method and the conventional method. FIG.5 (c) is a graph which shows the heating furnace exit side temperature in this invention method and the conventional method.

  As shown in FIG. 5A, the line speed is changed in the same way between 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 outlet side plate temperature is set using the steady speed after completion of the line speed change, whereas in the method of the present invention, the acceleration / deceleration during the acceleration / deceleration of the line speed is performed. Based on the speed prediction after completion, induction heating outlet side plate temperatures at a plurality of steel plate positions are set.

  In the method of the present invention and the conventional method, as shown in FIG. 5C, there is a dead time up to around 45 [s]. In the method of the present invention, the heating furnace outlet side plate temperature converges to the target value immediately after the dead 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, the fluctuation of the heating furnace outlet side plate temperature during the line speed change after the dead time has elapsed can be reduced as compared with the conventional method.

DESCRIPTION OF SYMBOLS 1 Temperature control apparatus 2 Induction heating apparatus 3 Process computer 11 Plate temperature measurement part 12 Line speed change part 13 Furnace temperature measurement part 14 Passing time prediction part 15 Induction heating exit side plate temperature calculation part 16 Induction heating output change part

Claims (4)

A plate temperature measuring step in which an induction heating device is arranged on the entry side and measures the temperature of the steel plate on the exit side of the heating furnace having a plurality of heating zones arranged along the sheet passing method;
A furnace temperature measuring step for measuring the furnace temperature of each heating zone;
A line speed changing step for changing the line speed based on the line speed changing command;
Among a plurality of positions including at least two points of a line speed change start time and a line speed change end time among the sheet passing direction positions of the steel sheet charged into the heating furnace from the start of change of the line speed to the end of change. A passing time prediction step for predicting the passing time of each heating zone,
Using the passing time prediction result for the plurality of positions predicted by the passing time prediction step and the current temperature furnace temperature measurement value measured by the furnace temperature measurement step, the steel sheet on the outlet side of the heating furnace An induction heating outlet side plate temperature calculation step for calculating the temperature of the steel plate on the outlet side of the induction heating apparatus 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,
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 outlet side of the induction heating device calculated by the induction heating outlet side plate temperature calculation step;
A temperature control method for a steel sheet, comprising: In the temperature control method of the steel plate according to claim 1,
The plate temperature calculation model formula is characterized in that the line speed and the furnace temperature measurement value at the current time are corrected with an error from the measurement value of the steel plate temperature prediction value obtained as an input of the plate temperature calculation model formula. A method for controlling the temperature of a steel sheet. An induction heating device is arranged on the entry side, and a plate temperature measurement unit for measuring the temperature of the steel plate on the exit side of the heating furnace having a plurality of heating zones arranged along the sheet passing method,
A furnace temperature measuring unit for measuring the furnace temperature of each heating zone;
A line speed change unit for changing the line speed based on the line speed change command;
Among a plurality of positions including at least two points of a line speed change start time and a line speed change end time among the sheet passing direction positions of the steel sheet charged into the heating furnace from the start of change of the line speed to the end of change. A transit time prediction unit for predicting the transit time of each heating zone,
Using the passing time prediction results for the plurality of positions determined by the passing time prediction unit and the current furnace temperature measurement value measured by the furnace temperature measurement unit, the steel sheet on the outlet side of the heating furnace An induction heating outlet side plate temperature calculation unit that calculates the temperature of the steel plate on the outlet side of the induction heating apparatus so that no change occurs, using a plate temperature calculation model that can calculate the temperature of the steel plate in the heating furnace,
An induction heating output changing unit for changing the output of the induction heating device so as to be the temperature of the steel plate on the outlet side of the induction heating device calculated by the induction heating outlet side plate temperature calculation unit;
A temperature control device for a steel sheet, comprising: In the temperature control apparatus of the steel plate of Claim 3,
The plate temperature calculation model formula is characterized in that the line speed and the furnace temperature measurement value at the current time are corrected with an error from the measurement value of the steel plate temperature prediction value obtained as an input of the plate temperature calculation model formula. A steel sheet temperature control device.

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