JP4126463B2 - Furnace temperature setting method in continuous annealing furnace heating furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a furnace temperature setting method in a heating furnace of a continuous annealing furnace, and more particularly to a furnace temperature setting method for controlling the furnace temperature of the first half of the heating furnace and the entire heating furnace.
[0002]
[Prior art]
In a continuous annealing furnace, it is important to prevent the occurrence of meandering and to ensure a stable sheet passing state. The first possible cause of meandering is the generation of a thermal crown of hearth rolls in the first half of the furnace. Conventionally, a method for controlling the thermal crown itself and a method for preventing the thermal crown by cooling the hearth roll are known. These techniques are also one of the means for preventing meandering, but there are some facilities that are not mechanically compatible.
[0003]
Therefore, we devised the initial crown of the hearth roll and conceived a method to prevent meandering by controlling the strip surface temperature at the center of the heating furnace, that is, the furnace temperature in the first half of the heating furnace, to suppress the generation of the thermal crown. Yes. As a means for doing this, it is necessary to divide the heating furnace into a plurality of zones and individually set the furnace temperature in each zone.
[0004]
As a method for setting the furnace temperature for each zone, for example, Japanese Examined Patent Publication No. 59-33176 discloses a low fuel by switching to step heat or flat heat depending on the dimensions of the strip, the steel type, and the target plate temperature on the heating furnace exit side. A method of performing an efficient heat treatment with the amount used is disclosed. Here, step heat refers to a furnace temperature setting method in which the zone of the heating furnace is divided into, for example, four, and the furnace temperature set value is gradually increased by a certain step width from the previous zone, and flat heat is the entire furnace A furnace temperature setting method in which all zones have the same target furnace temperature. A furnace temperature setting method in which the furnace temperature setting value is gradually lowered with a certain step width from the previous zone is referred to as reverse step heat.
[0005]
Japanese Patent Laid-Open No. 5-25555 separately measures the plate temperature at the intermediate portion and the outlet side of the heating furnace, controls the furnace temperature of the first half of the heating furnace based on the intermediate portion plate temperature, An apparatus in which the furnace temperature in the latter half of the heating furnace is controlled based on the part plate temperature is disclosed. Japanese Patent Application Laid-Open No. 5-271784 discloses a technique in which the furnace temperature in the first half of the heating furnace is set higher than the furnace temperature in the second half of the heating furnace. Furthermore, in Japanese Patent Laid-Open Nos. 60-56026 and 7-126759, the heating furnace is divided into a plurality of zones, and the set furnace temperature in each zone is increased stepwise from the upstream side to the downstream side. What to set is disclosed.
[0006]
[Problems to be solved by the invention]
However, the conventional method of switching to step heat or flat heat depending on the size of the strip, the steel type, and the target plate temperature on the heating furnace exit side fixes the heat pattern depending on the object, and changes the step width. Since it does not take into account the prevention of meandering, there is a possibility that the exit side temperature may deviate significantly from the target temperature when a person attempts to correct the central temperature to prevent meandering. It was. On the other hand, in terms of quality, if it is intended to guarantee the outlet side plate temperature, the central plate temperature cannot satisfy the allowable range, and there is a risk of meandering.
[0007]
In addition, in the method of calculating and setting the furnace temperature of the first half and the second half of the furnace separately based on the measured plate temperature at the middle part and the outlet side of the furnace, the balance of the furnace temperature is between the first half and the second half. When producing various varieties, there is a risk that the desired temperature of the furnace will not be in time for the next material, or that the squeeze of the furnace zone itself may adversely affect the equipment.
[0008]
In addition, the method of setting the furnace temperature of the first half of the heating furnace to be high is actually overcapacity because the set temperature cannot be reached in the first half, or the use is limited because the predicted outlet side plate temperature is insufficient. There are problems such as poor fuel efficiency.
[0009]
Also, in the method of dividing the heating furnace into multiple zones and setting the furnace temperature so that the set furnace temperature in each zone increases stepwise, the step width is not changed, so the plate temperature at the center of the heating furnace is within the allowable range There is a problem that the furnace temperature set value cannot be corrected when the condition is not satisfied.
[0010]
The present invention has been made in view of the above-mentioned conventional problems, and the furnace temperature is set so that the plate temperature at the center of the heating furnace and the outlet side can be appropriately controlled while performing efficient heat treatment with a small amount of fuel used. In addition, it is an object of the present invention to provide a technique capable of preventing the occurrence of meandering and improving the quality and the plate passing property.
[0011]
[Means for Solving the Problems]
The present invention divides a heating furnace of a continuous annealing furnace that continuously heats a metal strip into a plurality of zones in the traveling direction of the metal strip, and can set different furnace temperatures for each zone to heat the traveling metal strip. In the furnace temperature setting method in the heating furnace of the continuous annealing furnace for controlling the metal strip plate temperature at the heating zone outlet side, the plate temperature at the heating furnace outlet side and the center of the heating furnace is monitored, the heating furnace outlet side and the heating In the center of the furnace , the furnace temperature set value is changed from step heat to flat heat in accordance with the monitored plate temperature so that the plate temperature of the metal strip falls within a predetermined range set in advance. The above-mentioned problem is solved by making the transition while gradually reducing .
[0013]
In the present invention, the heating furnace of the continuous annealing furnace that continuously heats the metal strip is divided into a plurality of zones in the traveling direction of the metal strip, and a separate furnace temperature can be set for each zone. In the furnace temperature setting method in the heating furnace of the continuous annealing furnace that controls the plate temperature of the metal strip on the heating zone exit side, the plate temperature is monitored at the heating furnace exit side and the heating furnace center, and the heating furnace exit side and In the center of the heating furnace, the furnace temperature set value is changed from flat heat to reverse step heat according to the monitored plate temperature so that the plate temperature of the metal strip falls within a predetermined range set in advance . The transition is made while gradually increasing the step width.
[0014]
Hereinafter, the process leading to the present invention will be described.
[0015]
First, the inventors separately set the furnace temperature setting of the first half of the heating furnace with a plate thermometer installed in the center of the heating furnace and the furnace temperature setting of the latter half of the heating furnace with a plate thermometer installed on the outlet side of the heating furnace. However, the relationship between the target plate temperatures at the center of the heating furnace and on the outlet side varied depending on the material.
[0016]
In other words, since the purpose is only to prevent meandering in the center of the heating furnace, it does not vary greatly depending on the material, but on the exit side, the purpose is to guarantee the quality of the material, so the target plate depends on the destination, purpose of use, etc. The temperature varies greatly. Therefore, when trying to set the furnace temperature using the target plate temperature at the center of the heating furnace and the outlet as it is, the furnace temperature setting in the first half of the heating furnace may suddenly fall below the lower limit value.
[0017]
Conventionally, step heat and flat heat are fixed depending on the steel type and size, and there is no method for changing the step width even in the case of step heat.
[0018]
Therefore, in the present invention, step width is basically changed little by little on the assumption that the furnace temperature does not vary greatly from the entry side to the exit side using step heat.
[0019]
According to the present invention, while monitoring the plate temperature at the center of the heating furnace and the outlet side of the heating furnace, the furnace temperature set values are changed so as to appropriately control the respective plate temperatures. Even when there are many changes, the transition is smooth, the occurrence of meandering can be prevented, and the product material can be assured.
[0020]
Furthermore, not a furnace temperature setting of the heating furnace, step heat, using a step pattern such as a flat heat and reverse step heat. Thus modify the step size, apart furnace temperature more than necessary in each zone Therefore, the step pattern and the furnace temperature can be smoothly changed up and down, and the furnace temperature setting can be easily changed when a wide variety of materials are passed in a short cycle while the combustion effect is as high as possible.
[0021]
In addition, since the plate temperature in the central portion is intended to prevent meandering, it can be said that the target plate temperature in the central portion satisfies the target unless it falls below the target value (ie, the target plate temperature in the central portion = This is the lower limit of tolerance.) The upper and lower permissible ranges of the target plate temperature on the delivery side are set according to the material, and the current furnace temperature is set within the permissible range.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
FIG. 1 is a schematic configuration diagram showing equipment including a heating furnace of a continuous annealing furnace to which the present invention is applied.
[0024]
In FIG. 1, 10 is a heating furnace which forms the main body of the continuous annealing equipment. A continuous strip-shaped strip 12 is welded through the heating furnace 10 to pass through it. These strips 12 are continuously fed in the direction of arrow A as the rolls 14 inside and outside the heating furnace 10 rotate, and are rapidly heated toward the exit side of the heating furnace 10 by, for example, radiant heat from a radiant tube burner. Is done.
[0025]
Reference numeral 16 is a high-order computer for giving comparative data such as plate thickness, plate width, and steel type for the material to be manufactured, the target plate temperature of the material at the center of the heating furnace 10 and the outlet side, and the allowable upper and lower limits.
[0026]
Reference numeral 18 denotes a furnace temperature setting computer for setting a specific furnace temperature. Based on the material standard from the host computer 16, the furnace temperature setting computer 18 obtains the specific gravity, specific heat, and plate temperature target at the center of the target material and their allowable values. Also, the furnace temperature setting computer 18 basically uses what step pattern for the material to be heated, that is, the furnace temperature is set to the same furnace temperature in all zones in a flat shape, or the furnace temperature is increased in a step shape. Then, read the initial conditions such as how much step width to raise the furnace temperature. The furnace temperature setting computer 18 performs a plate temperature prediction calculation based on these initial conditions. That is, as a result of determining the furnace temperature so as to satisfy the plate temperature at the outlet side of the heating furnace 10, if the plate temperature at the center is insufficient, the step pattern is corrected and the plate temperature prediction calculation is performed again. The final result of repeating the temperature prediction and the furnace temperature correction is output as a furnace temperature value to the controller 20 that controls the furnace temperature of the heating furnace 10.
[0027]
The heating furnace 10 is divided into, for example, four zones Z1, Z2, Z3, and Z4 as objects for setting the furnace temperature. In each zone, a thermometer 22 is installed for each of the upper part and the lower part, and the furnace temperature is measured. The result of the furnace temperature measurement by the thermometer 22 is taken into the controller 20. In each zone, a plurality of combustion gas pipes 24, a combustion gas flow rate measuring device 26, and a combustion gas flow rate valve 28 are provided as necessary, and are controlled by a controller 20 installed in each. The furnace temperature in each zone is adjusted by opening and closing the combustion gas flow valve 28 by feedback from a combustion gas flow measuring device 26 provided separately for the upper and lower portions of each zone.
[0028]
In addition to these, plate thermometers 30, 32, and 34 for measuring the plate temperature of the surface of the strip 12 are installed on the entrance side of the heating furnace 10, the center portion of the heating furnace, and the exit side of the heating furnace. It is taken into the temperature setting computer 18 and used for the plate temperature prediction calculation. Further, the feeding speed of the strip 12 by the roll 14 or the like is measured by the line speed detector 36, and the speed is also taken into the furnace temperature setting computer 18 and used for the plate temperature prediction calculation.
[0029]
Hereinafter, the operation of the present embodiment will be described.
[0030]
FIG. 2 is a flowchart showing a flow of calculation processing performed by the furnace temperature setting computer 18 in the first embodiment.
[0031]
This first embodiment is the case where the step heat with a step width of a ° C. becomes the initial value, and even after correction, the furnace temperature on the first half side does not allow the reverse step-shaped furnace temperature setting with a higher furnace temperature. is there.
[0032]
First, at step 100, the furnace temperature setting computer 18 receives data such as comparison data, plate thickness, plate width, steel type, delivery target plate temperature value and its allowable range from the host computer 16. Next, in step 102, other data necessary for the furnace temperature setting calculation, such as the center plate temperature target value, its allowable value, and the initial value of the step pattern, are read.
[0033]
In the next step 104, plate temperature prediction calculation is performed. In this, the furnace temperature value is calculated such that the plate temperature on the outlet side of the heating furnace 10 becomes the target value according to the step pattern. In this case, a heat absorption model in which the entire furnace temperature is regarded as one is used. At this point, it is not known whether the center plate temperature is satisfied. Therefore, in the next step 106, the plate temperature prediction calculation of the first half of the furnace is performed based on the furnace temperature calculated now. That is, to what degree the plate temperature is heated up to the center by the calculated furnace temperature is calculated. In this case, a heat absorption model only for the first half of the furnace is used.
[0034]
In the next step 108, it is determined whether or not the center plate temperature is within the target allowable range. If the central plate temperature satisfies this allowable range, the process proceeds to the next step 110, the set furnace temperature is output to the controller 20, and the calculation is terminated.
[0035]
In step 108, when the central plate temperature does not satisfy the allowable range, that is, as shown in FIG. 3B, the central plate temperature is within the allowable range M2 even though the outlet side plate temperature is within the allowable range M2. If it is lower than M1, it is determined in step 112 whether or not the step width is 0 (that is, whether or not flat heat is applied). If the step width is not 0, the process proceeds to step 114, where the step width is reduced from the initial value a shown in FIG. 3A to a / 2 shown in FIG. 4A. To correct. By correcting the step width to ½ in this way, as shown in FIG. 4 (a), the furnace temperature in the latter half zone decreases by the amount that the step width has decreased, and the furnace temperature in the first half zone increases accordingly. To do. This ultimately means shifting the combustion load to the first half zone.
[0036]
Returning to step 104 again, the outlet side plate temperature and the central plate temperature are similarly calculated again with the corrected step pattern. At this time, as shown in FIG. 4 (b), when the central plate temperature is insufficient in the central allowable range M1, the step width is further increased by 1 in step 114, as shown in FIG. 5 (a). / 2 is corrected to a / 4. As a result, when the center plate temperature satisfies the allowable range M1 at the center as shown in FIG. 5B, the process proceeds to step 110, the set furnace temperature is output to the controller 20, and the calculation is terminated.
[0037]
Thus, the step width is corrected from the initial value a,
a → a / 2 → a / 4 → 0
In this order, the size is gradually reduced, and if necessary, as shown in FIGS. 6 (a) and 6 (b), finally flat heating is performed.
[0038]
As shown in FIGS. 7A and 7B, even in the case of flat heat, and when the central plate temperature is insufficient in the allowable range M1, in step 112, it is confirmed that the step width is 0, that is, flat heat. After confirmation, it is determined in step 116 whether the calculated outlet side plate temperature is within the commanded upper limit. If the outlet side plate temperature has not reached the upper limit, the target value of the outlet side plate temperature is increased by ΔT ° C. in step 118 as shown in FIG. 8A, and the outlet side plate temperature and the central plate temperature are calculated again. This is intended to increase the central plate temperature by the shortage by increasing the target plate temperature on the delivery side within a range that is acceptable for the material. Then, the target value of the delivery side plate temperature is changed to a high value within the upper limit, and when the central plate temperature reaches the allowable range M1 as shown in FIGS. 9A and 9B, the controller sets the set furnace temperature in step 110. 20 to finish the calculation.
[0039]
In step 116, if the delivery side plate temperature exceeds the upper limit value, the quality at the delivery side cannot be guaranteed because the plate temperature is too high, and the plate temperature is too low at the center. In step 120, the abnormality is notified and the process is terminated.
[0040]
7 to 9 described above are cases in which the step width is corrected and the flat plate heat is started from the step heat and the center plate temperature is insufficient. However, the initial value starts from the flat heat, and the reverse step furnace temperature is obtained. The same applies when the setting is not allowed.
[0041]
Next, a second embodiment of the present invention will be described.
[0042]
In the second embodiment, flat heat is used as an initial value, and a reverse-step furnace temperature setting is accepted.
[0043]
In the flowchart of the calculation process in this case, it is confirmed in step 112 in FIG. 2 that the reverse step width is within the allowable range (−b ° C.), and in step 114, the reverse step width is changed from 0 → (−b / 4). ) → (−b / 2) → (−b)
2 is all the same as the flowchart of FIG. Considering this replacement, the operation of the second embodiment will be described using the flowchart of FIG.
[0044]
Steps 100 to 106 are the same as those in the first embodiment. In step 108, as shown in FIG. 10 (b), when it is determined that the central plate temperature value is an axis below the allowable range M1 in the center, the process proceeds to step 112, and the reverse step width is within the allowable range (−b). It is determined whether or not. When the reverse step width is 0, the routine proceeds to step 116, where it is determined whether or not the outlet side plate temperature calculator is within the upper limit value, and when it is within the upper limit value, at step 118, as shown in FIG. The temperature is changed higher by ΔT ° C within the range up to the upper limit. At this time, as shown in FIG. 11B, also in the calculation of the flat heat, when the central plate temperature does not satisfy the allowable range M1 in the center, the reverse step width is changed to −b / 4 in step 114. At this time, if the center plate temperature does not satisfy the allowable range M1 at the center, the reverse step width is set in the order of 0 → (−b / 4) → (−b / 2) → (−b). The reverse step width is corrected to the permissible range (−b). Then, as shown in FIGS. 12A and 12B, when the central plate temperature satisfies the allowable range M1 at the center, the set furnace temperature is output to the controller 20 in step 110 and the calculation is terminated. .
[0045]
Thus, 2nd Embodiment is a case where it shifts to the reverse step heat which raises the furnace temperature of the first half zone from the case where the plate temperature of the heating furnace 10 central part and the exit side cannot be satisfied even by calculation of flat heat, The idea of shifting the combustion load to the first half and increasing the combustion load in the first half zone because the central plate temperature is insufficient is common to the first embodiment.
[0046]
In addition, although 2nd Embodiment started from the flat heat as an initial value, you may make it perform a reverse step-shaped furnace temperature setting as an initial value.
[0047]
In the embodiment described above, since both the plate temperature at the center of the heating furnace and the outlet side are satisfied, it is possible to guarantee the material on the outlet side and to prevent meandering that is likely to occur in the first half of the heating furnace. Became. In this embodiment, the combustion balance can be maintained by using a combustion pattern such as step heat or flat heat, and even when there are many changes in the furnace temperature setting, the transition can be performed smoothly. It became.
[0048]
【The invention's effect】
As described above, according to the present invention, since both the plate temperature at the center of the heating furnace and the outlet side are satisfied, the material on the outlet side is guaranteed and at the same time the meandering that is likely to occur in the first half of the furnace is prevented, While maintaining the balance of combustion, it has become possible to produce products that are stable and have good material.
[0049]
The purpose of maintaining the center plate temperature was to prevent meandering, but it is effective only for the plate temperature when passing through the center when it is necessary to guarantee the temperature control curve (heat cycle) in the heating furnace for other purposes. .
[0050]
In addition, the furnace temperature setting of the heating furnace is based on the step pattern of step heat, flat heat and reverse step heat, and the furnace temperature in each zone is set so that it does not vary more than necessary. The change is smooth, and there is also an effect that the furnace temperature setting can be easily changed when a wide variety of materials are passed through in a short cycle in a state where the effect of combustion is as high as possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an outline of a heating furnace of a continuous annealing furnace to which the present invention is applied. FIG. 2 is a flowchart showing a processing flow in the first embodiment of the present invention. FIG. 4 is an explanatory diagram showing the initial value in the process of calculating the furnace temperature from heat to flat heat. FIG. 4 is an explanatory diagram showing the case where the step width is halved in the process. FIG. FIG. 6 is an explanatory diagram showing a case where flat heat is generated in the same process. FIG. 7 is an explanatory diagram showing a process of calculating the furnace temperature in the case of flat heat in the first embodiment. FIG. 8 is an explanatory view showing a case where the furnace temperature is raised in the same process. FIG. 9 is an explanatory view showing a case where the center target value is achieved in the same process. FIG. 10 is a view from flat heat in the second embodiment. Reverse FIG. 11 is an explanatory diagram showing an initial value in the process of calculating the furnace temperature up to tep heat. FIG. 11 is an explanatory diagram showing a case where the furnace temperature is raised in the process. FIG. 12 is an explanatory diagram showing a case where reverse step heat is used in the process. [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Heating furnace 12 ... Strip 14 ... Roll 16 ... Host computer 18 ... Furnace temperature setting computer 20 ... Controller 22 ... Thermometer 24 ... Combustion gas piping 26 ... Combustion gas flow measuring device 28 ... Combustion gas flow valve 30, 32, 34 ... Plate thermometer 36 ... Line speed detector

Claims (2)

The heating furnace of the continuous annealing furnace that continuously heats the metal strip is divided into multiple zones in the direction of travel of the metal strip, making it possible to set different furnace temperatures for each zone, heating the traveling metal strip, In the furnace temperature setting method in the heating furnace of the continuous annealing furnace that controls the plate temperature of the metal strip on the side,
Monitor the plate temperature at the furnace exit side and the center of the furnace,
The furnace temperature set value is changed from step heat according to the monitored plate temperature so that the plate temperature of the metal strip falls within a predetermined range set in advance at the heating furnace exit side and the heating furnace center part, respectively. A method for setting a furnace temperature in a heating furnace of a continuous annealing furnace, wherein a transition is made to flat heat while gradually reducing the step width . The heating furnace of the continuous annealing furnace that continuously heats the metal strip is divided into multiple zones in the direction of travel of the metal strip, making it possible to set different furnace temperatures for each zone, heating the traveling metal strip, In the furnace temperature setting method in the heating furnace of the continuous annealing furnace that controls the plate temperature of the metal strip on the side,
Monitor the plate temperature at the furnace exit side and the center of the furnace,
In accordance with the monitored plate temperature , the furnace temperature set value is set from the flat heat so that the plate temperature of the metal strip falls within a predetermined range set in advance at the heating furnace outlet side and the heating furnace central portion, respectively. A furnace temperature setting method in a heating furnace of a continuous annealing furnace, wherein a transition is made to a reverse step heat while gradually increasing the step width.

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