JP2013221170A - Method and device for controlling sheet temperature in continuous annealing furnace - Google Patents

Abstract

[PROBLEMS] To prevent the occurrence of plate temperature deviation due to overshoot or undershoot, and the occurrence of plate temperature deviation due to the delay in reaching the plate temperature target value of the actual plate temperature value, and to reduce the furnace speed for adjusting the furnace temperature. It is not necessary to ensure that the actual plate temperature reaches the target plate temperature.
A coil having the same at least one condition selected from a sheet thickness, a sheet width, and a steel type when continuous annealing is performed by connecting coils having different sheet temperature target values by ΔT ° C on the inlet side of the continuous annealing furnace. The plate temperature target value when the plate temperature target value is gradually changed at a constant rate is obtained in advance, and when the coil tip having a different plate temperature target value reaches the heating zone entry side of the annealing furnace, The plate temperature target value is instantaneously changed by a predetermined value ΔT1 ° C. corresponding to the difference between the plate temperature attainment value and the next plate temperature target value, and then the plate temperature target value is changed within the one coil. The temperature is gradually changed to the target temperature at the constant rate.
[Selection] Figure 5

Description

  The present invention relates to a plate temperature control method and apparatus for a continuous annealing furnace, and in particular, a coil having a different plate temperature target value on the heating zone outlet side is connected in advance to the continuous annealing furnace entry side, and the connected coil is continuously annealed. In this case, it is possible to prevent the plate temperature from deviating due to overshoot or undershoot, and the plate temperature from deviating due to the delay in reaching the plate temperature target value. It is related with the plate | board temperature control method and apparatus of a continuous annealing furnace which can make the deceleration of the in-furnace plate speed for furnace temperature adjustment unnecessary by making it reach | attain.

  In the continuous annealing line as illustrated in FIG. 1, the coils 10 paid out from the plurality of payoff reels 12 with respect to steel plates (also referred to as coils) having different plate temperature target values at the exit of the heating zone 22 a of the annealing furnace 22. Are welded by a welding machine 14 and continuously passed. In FIG. 1, 16 is a cleaning device, 18 is a scrubber, 20 is an entry side looper, 22b is a soaking zone of the annealing furnace 22, 22c is also a cooling zone, 24 is an exit side looper, and 26 is a coil 10 after annealing. It is a tension reel.

  Conventionally, the switching of the plate temperature target value (that is, the plate temperature set value) is controlled by switching the furnace temperature at once when the boundary point of the coil having a different plate temperature target value reaches the entry side or the exit side of the heating zone 22a. On the other hand, as in Patent Document 1, there is also a control method in which the plate temperature target value is gradually changed by a certain amount within one coil before the boundary point of the coil reaches the outlet of the heating furnace. Proposed.

JP-A-5-117766

  However, as in the former case, when a welding point of a coil having a different plate temperature target value reaches the heating zone entry side, in the control for switching to a constant plate temperature target value determined for each coil, a boundary point is added. Since the plate temperature target value is switched at once when reaching the tropical entry side, immediately after the plate temperature target value is switched, the deviation between the plate temperature target value and the plate temperature actual value becomes large. Accordingly, when the plate temperature actual value rises or falls suddenly and the plate temperature set value is increased, the plate temperature target value is overshot or the plate temperature set value is lowered as illustrated in FIG. As illustrated in FIG. 3, the plate temperature target value may be undershooted. Therefore, when the absolute value of the overshoot or undershoot is large, the plate temperature is out of the allowable range, which may lead to a defective steel plate material.

  On the other hand, as illustrated in FIG. 4, in the case of the control in which the plate temperature target value is gradually changed by a certain amount within one coil as in the latter patent document 1, the plate temperature target value gradually changes. Therefore, the actual plate temperature will gradually change. However, when the rise or fall degree of the plate temperature actual value is small, it switches to the next coil without reaching the predetermined plate temperature target value, and the plate temperature allowable range in which the plate temperature actual value is determined for each coil. There was a possibility of losing.

  In addition, in order to prevent such plate temperature losing, it is conceivable to reduce the coil passage speed (referred to as the furnace speed) of the coil, but there is a problem that the production capacity is lowered. .

  The present invention has been made to solve the above-mentioned conventional problems, and the occurrence of plate temperature detachment due to overshoot and undershoot due to plate temperature detachment and delay in arrival of the plate temperature actual value to the plate temperature target value. It is an object of the present invention to prevent the need for slowing down the furnace speed for adjusting the furnace temperature, and to ensure that the actual plate temperature reaches the target plate temperature.

  The present invention is a coil in which at least one condition selected from a plate thickness, a plate width, and a steel type is the same when continuous annealing is performed by connecting coils having different plate temperature target values by ΔT ° C on the inlet side of the continuous annealing furnace. The plate temperature target value when the plate temperature target value is gradually changed at a constant rate is obtained in advance, and when the coil tip having a different plate temperature target value reaches the heating zone entry side of the annealing furnace, The plate temperature target value is instantaneously changed by a predetermined value ΔT1 ° C. corresponding to the difference between the plate temperature attainment value and the next plate temperature target value, and then the plate temperature target value is changed within the one coil. The problem is solved by gradually changing the temperature to the target temperature at the constant rate.

Here, when the predetermined value ΔT1 ° C. is instantaneously changed by a total change amount ΔT ° C. of a different coil with respect to the plate temperature target value when the tip of the coil reaches the heating zone entrance side of the annealing furnace, The overshoot amount (or undershoot amount) of the actual temperature value is ΔA1 ° C, the difference between the plate temperature target value and the plate thickness allowable upper limit value (or lower limit value) is ΔB1 ° C, and the coil tip enters the heating zone of the annealing furnace. When the plate temperature target value is gradually changed at a constant rate by the total change amount ΔT ° C. from the time when the coil tail end reaches the heating zone exit side of the annealing furnace, the coil tail end When the difference between the plate temperature target value and the plate temperature actual value is ΔA2 ° C. and the difference between the plate temperature target value and the plate temperature allowable lower limit value (or upper limit value) is ΔB2 ° C., the following expression: | ΔA2−ΔB2 | ≦ ΔT1 ≦ ΔT− (| ΔA1−ΔB1 |)
It is good to limit to the range.

  The present invention is also a plate temperature control device for a continuous annealing furnace used when continuous annealing is performed by connecting coils having different plate temperature target values by ΔT ° C. on the inlet side of the continuous annealing furnace, and the plate thickness, plate width, steel type Means for obtaining in advance a plate temperature arrival value when the plate temperature target value is gradually changed at a constant rate, and the tips of the coils having different plate temperature target values. Means for instantaneously changing the plate temperature target value by a predetermined value ΔT1 ° C. corresponding to the difference between the plate temperature attainment value and the next plate temperature target value when the temperature reaches the heating zone entry side of the annealing furnace; And a means for gradually changing the plate temperature target value in the same coil to the next plate temperature target value after changing the plate temperature target value instantaneously. A plate temperature control device for a continuous annealing furnace is provided.

Here, when the predetermined value ΔT1 ° C. is instantaneously changed by a total change amount ΔT ° C. of a different coil with respect to the plate temperature target value when the tip of the coil reaches the heating zone entrance side of the annealing furnace, The overshoot amount (or undershoot amount) of the actual temperature value is ΔA1 ° C, the difference between the plate temperature target value and the plate temperature allowable upper limit value (or lower limit value) is ΔB1 ° C, and the coil tip enters the heating zone of the annealing furnace. When the plate temperature target value is gradually changed at a constant rate by the total change amount ΔT ° C. from the time when the coil tail end reaches the heating zone exit side of the annealing furnace, the coil tail end When the difference between the plate temperature target value and the plate temperature actual value is ΔA2 ° C., and the difference between the plate temperature target value and the plate temperature allowable lower limit (or upper limit value) is ΔB2 ° C., the following expression: | ΔA2−ΔB2 | ≦ ΔT1 ≦ ΔT -(| ΔA1-ΔB1 |)
Means limited to the range of

  According to the present invention, the plate temperature target value is instantaneously changed by the predetermined value ΔT1 ° C. corresponding to the difference between the plate temperature target value when the plate temperature target value is gradually changed at a constant rate and the next plate temperature target value. Therefore, it is possible to prevent the plate temperature from being deviated due to a delay in reaching the plate temperature target value to the plate temperature target value when the plate temperature target value is gradually changed. Further, the amount ΔT1 ° C. at which the plate temperature target value is instantaneously changed is limited to the difference between the plate temperature target value when the plate temperature target value is gradually changed at a constant rate and the next plate temperature target value. Therefore, there is no occurrence of overshoot or undershoot that deviates from the allowable range of the plate temperature.

  Therefore, it is possible to prevent the plate temperature from falling without decreasing the furnace speed for the purpose of preventing the plate temperature from falling, and it is possible to prevent a reduction in production capacity and a decrease in line production.

  The average time of deceleration for adjusting the plate temperature was 30% of the entire conventional plate temperature switching time. However, when the plate temperature control according to the present invention is performed, the plate temperature is accurately changed without deceleration. be able to. In addition, there is no need to cut off the portion of the steel plate where the temperature is too low.

The figure which shows the whole structure of an example of a continuous annealing line When the plate temperature target value is increased by ΔT ° C when the tip of the next coil whose plate temperature target value differs by ΔT ° C reaches the heating zone entry side, the overshoot of the plate temperature actual value with respect to the plate temperature target value Diagram showing the state where When the tip of the next coil whose plate temperature target value differs by ΔT ° C reaches the heating zone entry side, when the plate temperature target value is lowered at a stroke by ΔT ° C, the plate temperature actual value undershoots the plate temperature target value. Diagram showing the state where When the plate temperature target value is gradually changed in one coil, the rate of increase of the actual value is small at the tail end of the coil, and the arrival delay amount ΔA2 ° C. of the actual plate temperature value to the target plate temperature is generated Figure showing The figure which shows the temperature setting method in embodiment of this invention When the tip of the next coil whose plate temperature target value differs by ΔT ° C reaches the heating zone entry side, when the plate temperature target value is lowered at a stroke by ΔT ° C, the plate temperature actual value undershoots the plate temperature target value. The figure which shows the state where quantity ΔA1 ° C has occurred When the plate temperature target value is gradually changed within one coil, a state in which the rate of decrease of the actual value is small at the tail end of the coil and the arrival delay amount ΔA2 ° C. of the actual plate temperature value to the target plate temperature value is generated. Figure showing The figure which shows the example of the temperature change state which pinched | interposed the coil with a wide plate temperature tolerance range between the coils with a narrow plate temperature tolerance range The figure which shows the measurement example of overshoot amount (DELTA) A1 degreeC of the coil tip The figure which shows the measurement example of arrival delay amount (DELTA) A2 degreeC of a coil tail end The figure which shows the example of the plate temperature target value of this invention and plate temperature actual value which were set based on the experimental result of FIG.9 and FIG.10.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the present embodiment, as illustrated in FIG. 5, when it is necessary to change the plate temperature target value by ΔT ° C. between coils having different plate temperature target values (FIG. 5 shows an example of increase), the tip of the next coil When the welding point reaches the heating furnace entrance side, the plate temperature target value is first changed instantaneously by ΔT1 ° C., and then the next plate temperature target is gradually increased at a constant rate to the welding point at the tail end of the coil. It is made to change to a value (ΔT2 ° C.).

  As described above, when the tip of the next coil having a different plate temperature target value reaches the heating zone entry side, it is changed instantaneously by ΔT1 ° C., so that the plate temperature target value described later is gradually changed. The plate temperature can be prevented from coming off due to the delay in reaching the plate temperature target value of the actual plate temperature value.

  Also, since the coil temperature is gradually changed to the next plate temperature target value at a constant rate from the tip of the coil to the tail end, there is no occurrence of overshoot or undershoot that deviates from the plate temperature allowable range.

  Here, ΔT1 ° C. can be determined as follows. In other words, when one coil (uses a sample) passes in advance, the plate temperature target value is instantly changed by the total change amount ΔT ° C when the coil tip reaches the heating zone entry side as illustrated in FIG. The temperature is raised, and the overshoot amount ΔA1 ° C. of the actual plate temperature is measured.

  In addition, when another coil (use of sample) passes in advance, as illustrated in FIG. 4, from the time when the coil tip reaches the heating furnace entry side until the coil tail end reaches the heating zone entry side. Then, the plate temperature target value is gradually raised at a constant rate by the total change amount ΔT ° C., and a difference (referred to as an arrival delay amount) ΔA 2 ° C. between the plate temperature target value and the plate temperature arrival value at the coil tail end is obtained. taking measurement.

Here, if the difference between the plate temperature target value illustrated in FIG. 2 and the plate temperature allowable upper limit value is ΔB1 ° C., and the difference between the plate temperature target value illustrated in FIG. 4 and the plate temperature allowable lower limit value is ΔB2 ° C., ΔT1 ° C. Can be set as:
| ΔA2−ΔB2 | ≦ ΔT1 ≦ ΔT− (| ΔA1−ΔB1 |) (1)

  In addition, the above-mentioned plate temperature attainment value is the past when the plate temperature target value is gradually changed at a constant rate with a coil having at least one condition selected from the plate thickness, plate width, and steel type. It is good also as an average value of these results, or it is good also as a value calculated | required by calculation.

  The right side of the above equation (1) is a condition for preventing the plate temperature actual value from deviating from the plate temperature allowable upper limit even if the plate temperature actual value overshoots. Further, the left side of the equation (1) is a condition for preventing a deviation from the allowable lower limit of the plate temperature even if the arrival delay of the actual plate temperature is generated.

  Note that ΔT1 ° C. is not limited to the above, and when the coil tip shown in FIG. 6 reaches the heating zone entry side, the plate temperature target value is instantaneously lowered by ΔT ° C. to measure the undershoot amount ΔA1 ° C., The plate temperature target value may be gradually decreased by a certain rate until ΔT ° C. until the coil tail end reaches the furnace entrance side, and ΔA2 ° C. may be measured to obtain a range of ΔT1 ° C. in the equation (1).

Actually, ΔT1 ° C. taking into account the effect of the difference between the plate temperature deviation amount | ΔA1-ΔB1 | ° C. due to overshoot and the plate temperature deviation amount | ΔA2-ΔB2 | ° C. due to the arrival delay of the actual plate temperature value. It is desirable to set the value of the center of the upper and lower limits as in the following equation.
ΔT1 = (1/2) {ΔT− (| ΔA1−ΔB1 |) + (| ΔA2−ΔB2 |)}
... (2)

  In this way, the plate temperature is set, and, as illustrated in FIG. 8, a coil having a wide plate temperature tolerance range (for example, the second coil and the fourth coil) having a wide plate temperature tolerance range (eg, the second coil and the fourth coil). By sandwiching the third coil), it is possible to satisfy the allowable range of the plate temperature for all the coils.

  When the plate temperature target value is changed by ΔT = 40 ° C when cold-rolled steel sheets with different steel plate temperatures of T4CA and DTS and size of 0.20x900mm are welded continuously. When the plate temperature target value is instantaneously changed by ΔT ° C. when the welding point at the coil tip reaches the heating furnace entrance side, the overshoot amount ΔA1 = 15 ° C. is obtained from the actual value illustrated in FIG. The difference ΔB1 between the target temperature value and the plate temperature allowable upper limit value was set to 10 ° C. FIG. 10 shows a case where ΔT ° C. is gradually changed to a plate temperature target value at a constant rate from the time when the leading end of the next coil reaches the inlet side of the heating furnace until the tail end of the next coil reaches the inlet side of the heating furnace. The difference ΔA2 = 15 ° C. between the plate temperature target value and the plate temperature actual value at the tail end of the next coil is obtained from the actual value to be obtained, and the difference ΔB2 = 10 ° C. between the plate temperature target value and the plate temperature allowable lower limit value is obtained. From these values, ΔT1 = 20 ° C. was set and operated using the equations (1) and (2) according to the present invention, and as shown in FIG. It was confirmed that can be changed (increased). Conventionally, it has been necessary to reduce the plate speed for temperature adjustment to prevent overshoot and arrival delay of the plate temperature, and that time accounted for 30% of the plate temperature switching time. It was confirmed that the production time was 0% and the production efficiency was improved by 10%.

  In addition, the operation amount of temperature is not limited to the present embodiment, but can be changed according to the size (thickness, width, cross-sectional area, etc.) of the coil.

  In the above description, the case where the coil temperature is increased has been described. However, the present invention can be similarly applied to the case where the coil temperature is decreased.

10 ... Steel plate (coil)
DESCRIPTION OF SYMBOLS 12 ... Pay-off reel 14 ... Welding machine 22 ... Annealing furnace 22a ... Heating zone 26 ... Tension reel

Claims (4)

When continuous annealing is performed by connecting coils with different plate temperature target values by ΔT ° C on the inlet side of the continuous annealing furnace,
With a coil having at least one condition selected from a plate thickness, a plate width, and a steel type, a plate temperature attainment value is obtained in advance when the plate temperature target value is gradually changed at a constant rate,
When the tips of the coils having different plate temperature target values reach the heating zone entry side of the annealing furnace, the plate temperature target is set by a predetermined value ΔT1 ° C. corresponding to the difference between the plate temperature reached value and the next plate temperature target value. Change the value instantly,
Next, a plate temperature control method for a continuous annealing furnace, wherein the plate temperature target value is gradually changed at the constant rate until the next plate temperature target value in the one coil. When the predetermined value ΔT1 ° C. is instantaneously changed by a total change amount ΔT ° C. of the different coil with respect to the target plate temperature when the tip of the coil reaches the heating zone entrance side of the annealing furnace, The overshoot amount (or undershoot amount) is ΔA1 ° C, the difference between the plate temperature target value and the plate temperature allowable upper limit value (or lower limit value) is ΔB1 ° C, and the coil tip reaches the heating zone entry side of the annealing furnace. In the case where the plate temperature target value is gradually changed at a constant rate by the total change amount ΔT ° C. from the time when the coil tail end reaches the heating zone exit side of the annealing furnace, the plate temperature of the coil tail end is changed. When the difference between the target value and the actual plate temperature value is ΔA2 ° C., and the difference between the target plate temperature value and the allowable lower limit value (or upper limit value) is ΔB2 ° C., the following formula: | ΔA2−ΔB2 | ≦ ΔT1 ≦ ΔT− ( | ΔA1-ΔB1 |)
The plate temperature control method for a continuous annealing furnace according to claim 1, wherein the plate temperature control method is limited to the range described above. A plate temperature control device for a continuous annealing furnace used when continuous annealing is performed by connecting coils having different plate temperature target values by ΔT ° C. on the inlet side of the continuous annealing furnace, at least one selected from a plate thickness, a plate width, and a steel type With a coil having the same conditions as described above, means for obtaining in advance a plate temperature arrival value when the plate temperature target value is gradually changed at a constant rate;
When the tips of the coils having different plate temperature target values reach the heating zone entry side of the annealing furnace, the plate temperature target is set by a predetermined value ΔT1 ° C. corresponding to the difference between the plate temperature reached value and the next plate temperature target value. Means to change the value instantly;
Means for changing the plate temperature target value instantaneously and then gradually changing the plate temperature target value in the one coil to the next plate temperature target value at the constant rate;
A plate temperature control device for a continuous annealing furnace, comprising: The predetermined value ΔT1 ° C. is the actual plate temperature value when the coil temperature target value is instantaneously changed by the total change amount ΔT ° C. of the different coil when the tip of the coil reaches the heating zone entry side of the annealing furnace. The overshoot amount (or undershoot amount) is ΔA1 ° C, the difference between the plate temperature target value and the plate temperature allowable upper limit value (or lower limit value) is ΔB1 ° C, and the coil tip reaches the heating zone entry side of the annealing furnace. In the case where the plate temperature target value is gradually changed at a constant rate by the total change amount ΔT ° C. from the time when the coil tail end reaches the heating zone exit side of the annealing furnace, the plate temperature of the coil tail end is changed. When the difference between the target value and the actual plate temperature value is ΔA2 ° C., and the difference between the target plate temperature value and the allowable lower limit value (or upper limit value) is ΔB2 ° C., the following formula: | ΔA2−ΔB2 | ≦ ΔT1 ≦ ΔT− ( | ΔA1-ΔB1 |)
The plate temperature control device for a continuous annealing furnace according to claim 3, further comprising means for limiting to the above range.

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