JPH11293349A - Control of temperature of continuous heating furnace and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling the temp. in a heating furnace, with which the aggravation of consumption unit is prevented and the productivity is improved, and to provide a device therefor. SOLUTION: Actually measured rolling temp. obtained by an actually measured rolling temp. calculating means 8 is fetched, and it is judged whether or not rolling at a corrected setting temp. is executed. When judge not, it is further judged whether or not the average value of the measured rolling temps. of the newest steel material Si is lower than that of the previous steel material Si -1 . If yes, it is also judged whether or not the steel material showing a lower temp. value than the previous one continues in (m) pieces, and if so, it is judged whether or not the average value of the measured rolling temps. of the steel material Si is less than a corrected threshold value. If judged lower than the corrected threshold value, a corrected setting temp. is calculated by using a correcting quantity table 18 and a flag to instruct forcible execution is turned ON. Then, the corrected setting temp. is selected with a setting temp. slecting means 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the temperature of a continuous heating furnace for continuously heating a plurality of workpieces to be supplied to a rolling mill in a hot rolling facility, and an apparatus used for implementing the method.

[0002]

2. Description of the Related Art A slab cast in a steelmaking factory is processed into a steel slab in a lump mill, and then, after a care process, conveyed to a heating furnace in a rolling factory where the slab is continuously heated to a predetermined temperature. After being heated to a rolling mill. In this continuous heating furnace, a value obtained by adding an expected temperature drop from the time of extraction from the heating furnace to the time of starting rolling in the rolling mill to the target rolling temperature of the rolling mill is defined as the target heating temperature. And
The steel material temperature at the time of being transferred to the heating furnace is used as the initial value, the temperature rise of the steel material in the furnace is obtained from the furnace atmosphere temperature or the furnace wall temperature by heat transfer calculation, and the steel material is extracted from the extraction pitch determined by the operating conditions. The temperature of the heating furnace is set such that the moving speed is predicted, and the value (steel material temperature at the extraction position) calculated using these values becomes the target heating temperature.

[0003] The steel material temperature (initial value) at the time of being carried into the heating furnace is obtained by heat transfer calculation using the steel material temperature at the time of cutting in the previous process, or this value is obtained by a thermometer installed in the furnace. Use the value corrected with the actual measurement value. Then, feedback control is performed such that the steel material temperature at the extraction position secures at least the target heating temperature, and that the steel material temperature during rolling (actually measured rolling temperature) does not fall below the lower limit management value of the target rolling temperature.

In this method, it is necessary to actually measure the furnace temperature in order to obtain the calculated value of the steel material temperature rise in the furnace and the initial value obtained by the heat transfer calculation. When a thermometer is installed in a furnace for measurement, a large-scale facility is required to shut off disturbance radiant energy from the furnace wall or the flame, and it is difficult to shut off completely. The present applicant has disclosed a method of controlling the temperature of a heating furnace which does not require the measurement of the furnace temperature in Japanese Patent Publication No. 3-32605. In this method, the target heating temperature is feedback-corrected based on the deviation between the measured rolling temperature and the target rolling temperature, and the error between the temperature drop (actual temperature drop temperature) obtained based on the measured value and the expected temperature drop.

[0005] Further, in the furnace, the steel material is supported by columns (fixed beam, moving beam) cooled by a cooling means such as water cooling and transferred in the furnace length direction. Therefore, in the steel material at the time of extraction, the temperature of the portion in contact with the column is lower than that of the portion not in contact with the column, and so-called skid marks are generated. This skid mark increases the load on the rolling mill and in some cases trips the rolling mill.

However, the above-described method is intended only for each steel material temperature at the time of extraction to satisfy a target heating temperature (target extraction temperature), and does not reflect the presence of a skid mark portion in control. Not. In order to cope with this, the present applicant subtracts the minimum value from the average value of the measured rolling temperature to obtain a skid mark width, and calculates a value obtained by adding the skid mark width, the actual drop temperature and the lower limit management value of the rolling temperature. A method of controlling the temperature as a corrected target extraction temperature is disclosed in
No. 337818.

[0007]

However, in the actual operation, the actual rolling temperature is set to the target rolling temperature due to various reasons such as an increase in the extraction pitch, an increase in the size of the steel material, a change in the steel type, or a change in the rolling schedule. May be below. The extraction pitch is determined to some extent depending on the rolling size, construction, steel type, and the like, but varies depending on the technical difference between operators, heating conditions, and the like. Immediately after model change, product size,
Control for suppressing surface flaws and thereafter gradually accelerating is also performed. Therefore, when it is predicted that the temperature is equal to or lower than the target rolling temperature due to the above-mentioned circumstances, the set temperature of the heating furnace is increased. However, since the heating furnace has a large thermal inertia,
It usually takes 3 to 5 minutes for the rise in the set temperature to be reflected in the steel material temperature. Therefore, it is necessary to wait for this follow-up, and wasteful power is consumed in the rolling mill, which deteriorates the basic unit and leads to a decrease in productivity.

[0008] The present invention has been made in view of such circumstances, and it is possible to prevent the deterioration of the basic unit by estimating that the measured rolling temperature is lower than the target rolling temperature and raising the preset temperature in advance. It is another object of the present invention to provide a heating furnace temperature control method capable of improving productivity and an apparatus used for implementing the method.

[0009]

According to the first aspect of the present invention,
In a method for controlling the temperature of a continuous heating furnace that continuously heats a plurality of workpieces to be given to a rolling mill, the temperature of the workpieces at the time of rolling is measured, and the obtained value is compared with the value of the previous one. When the comparison result indicates that the value is lower than the value of the previous individual for a predetermined number of times, the set temperature of the continuous heating furnace is increased by a predetermined amount, and then lowered.

The invention according to claim 6 is an apparatus for controlling the temperature of a continuous heating furnace for continuously heating a plurality of workpieces to be supplied to a rolling mill in a hot rolling facility. The means for measuring the temperature of the material to be treated, the means for comparing this measured value with the measured value of the previous individual, and as a result of the comparison, it has been determined that the measured value is lower than the measured value of the previous individual for a predetermined number of times. Means for outputting a command to raise the set temperature of the continuous heating furnace by a predetermined amount.

The invention according to claim 2 is characterized in that, during rolling of the material to be processed given from a continuous heating furnace to a rolling mill, an average value of the temperature of the material to be processed obtained at a plurality of points of the material to be processed; Using the extraction temperature of the material to be processed at the time of extraction from the continuous heating furnace, a predetermined target extraction temperature of the material to be processed is corrected, so that the extraction temperature of the material to be processed becomes the corrected target extraction temperature. In the method of setting the temperature of the continuous heating furnace, based on the set temperature, in the method of controlling the temperature of the continuous heating furnace to continuously heat a plurality of workpieces to be given to the rolling mill, the average value obtained Was compared with the average value of the previous individual, and when the average value was lower than the average value of the previous individual for a predetermined number of times, the set temperature of the continuous heating furnace was adjusted according to the processing conditions and / or the material to be processed. It is raised by a predetermined amount and then lowered

In these inventions, it takes time until the furnace temperature actually rises after the set temperature is raised, but before the minimum value of the measured rolling temperature falls below the target rolling temperature lower limit value. Since the temperature inside the furnace can be completely increased,
It is possible to prevent the occurrence of processing defects such as an increase in load and a trip of a rolling mill during rolling in a post-process.
In addition, since the set temperature is increased only when the decrease in the measured rolling temperature is continued for a predetermined number of times or more, the set temperature is not increased when the value of only one individual decreases and then returns. Therefore, in such a case, the set furnace temperature correction function operates, and the measured rolling temperature of the succeeding workpiece does not become excessively high.

According to a third aspect of the present invention, in the first or second aspect, the amount of increase in the set temperature of the continuous heating furnace is determined based on the number of materials to be processed extracted from the continuous heating furnace per unit time. It is characterized by doing.

The amount of temperature rise taking into account the delay time in temperature rise in the furnace and the quantity per unit time of the material to be extracted from the continuous heating furnace (extraction pitch; pieces / unit time or t / unit time) is taken into consideration. Since it is used, cracking of the target rolling temperature lower limit value can be reliably prevented.

According to a fourth aspect of the present invention, in the first, second or third aspect, the set temperature of the continuous heating furnace is such that the average value is continuously lower than the previous value by a predetermined number of times and the average value is a predetermined value. The threshold value is increased when the threshold value becomes smaller than the threshold value.

Thus, if the average value is continuously lower than the previous value a predetermined number of times, but the average value is not smaller than a predetermined threshold value, the set temperature is not increased and the set temperature is not increased. It is possible to prevent the timing of the rise from becoming too early, and to minimize the increase in power consumption.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the set temperature of the continuous heating furnace is increased by:
If the number of materials to be processed is less than a predetermined number, the process is not performed.

It is possible to prevent the mold from being changed before or immediately after the increase in the furnace temperature. Therefore, it is possible to reduce the number of times the change of the set temperature is repeated, and to suppress the deterioration of the basic unit.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a control block diagram of a temperature control device for a continuous heating furnace according to the present invention, and also shows main parts of a hot rolling facility. Figures 2-4
5 is a flowchart showing a processing procedure of the method of the present invention.
In the hot rolling equipment, a heating furnace 1
Is arranged, and the rolling mill 2 is installed downstream thereof. The combustion of the heating furnace 1 is controlled by a combustion control device 5. The steel materials S ₁ , S _2, ..., S _i, S _n , which are the materials to be heated, are sequentially carried into the heating furnace 1.
It is heated during the transfer in the furnace length direction and is extracted from the extraction port. The extracted steel S is guided to the rolling mill 2 and rolled to be commercialized. At a predetermined position of the rolling mill 2 (e.g., on the exit side of the first vertical rolling mill), a rolling thermometer 3 for measuring a steel material temperature is provided.

First, the type, size, rolling conditions,
The target rolling temperature is calculated by the higher-order calculation means 4 based on data such as the destination (step S1). The target extraction temperature calculating means 6 calculates the target extraction temperature using the target rolling temperature and the data of the predicted drop temperature / skid mark width reference value table 7 given in advance (step S).
2).

Then, it is determined whether or not the processing is for the _first steel S1 (step S3). If it is the first steel, the processing in the target extraction temperature changing means 14 is not performed, and the furnace time calculation is performed. The means 15 calculates the in-furnace time of the steel S based on the extraction pitch (step S4). If it is the second or later,
Processing for Correcting Target Extraction Temperature (Step S5)
Is performed according to the processing procedure shown in FIG.

First, a rolling thermometer 3 provided in a rolling mill 2
As a result, the temperature of the steel S exiting the first vertical rolling mill is detected at a plurality of locations over the entire length, and the measured rolling temperature is calculated by the measured rolling temperature calculating means 8 (step S51). The actually measured drop temperature calculating means 9 calculates the actually measured drop temperature from the obtained actually measured rolling temperature and the target extraction temperature, and, if there is a previous value, the value is compared with the previous value by the smoothing means 10. It is smoothed (step S52). In addition, the skid mark width calculating means 11 calculates the skid mark width by subtracting the minimum value from the average value of the measured rolling temperatures over the entire length of the steel material S. The obtained skid mark width is smoothed by the smoothing means 12 (step S53). Then, these values are added by the target extraction temperature correction means 13 to calculate a correction amount of the target extraction temperature (step S54). Target extraction temperature changing means 14
Then, the target extraction temperature is changed based on the obtained correction amount of the target extraction temperature (step S55). After the change of the target extraction temperature, the process proceeds to step S4 to calculate the furnace time.

The set temperature of the heating furnace 1 is set such that the steel material S transferred in the heating furnace 1 reaches the changed or unchanged target extraction temperature in the obtained furnace time. Is calculated (step S6). As described above, the set temperature of the heating furnace 1 is calculated using the expected drop temperature and the skid mark width of the expected drop temperature / skid mark width reference value table 7 in the first process, and the actual value in the second and subsequent processes. The feedback is calculated.

Next, it is determined whether or not i or more steel materials S of the same type have been extracted (step S7). If there are i or more steel materials S, the set temperature correcting means 17 sets the set temperature as shown in FIG. A correction process is performed (Step S8). In the set temperature correction process, first, the measured rolling temperature calculated by the measured rolling temperature calculating means 8 is taken in (step S81), and it is determined whether or not the corrected set temperature is being executed (step S82).
If it is not running, the mean value of the measured rolling temperature of latest steel S _i is, it determines whether the previous steel S _i-1 of less than (step S83). Here, in the case of YES, it is determined whether or not m steel materials having a lower value than the previous time are continuous m (step S84). If m are present continuously, the average value of the measured rolling temperature of the steel material S _i determines whether below the corrected threshold value to be described later (step S85). When the temperature is below the correction threshold, the correction set temperature is calculated using the correction amount table 18, and the forced execution instruction flag is turned on (step S86). Then, the set temperature corrected by the set temperature selecting means 19 is selected (step S9).

In step S82, the correction set temperature is already being executed.
In step S83, the steel material S _iThe measured rolling temperature of
Steel S_i-1If the value is higher than the value of
If it is determined that the temperature decrease tendency is not continuous for m lines
And if not below the correction threshold in step S85
Is executed in step S without turning on the forced execution instruction flag.
9 and proceed to step 9
Select a constant temperature.

If it is determined in step S7 that the number is not equal to or more than i, the flow directly proceeds to step S9, and a set temperature that has not been corrected is selected. When one of the set temperatures is selected by the set temperature selecting means 19, the value is output to the combustion control device 5 (step S10).

When the corrected set temperature is given, the combustion control device 5 holds the temperature for a predetermined time and then returns to the temperature before the correction. If information indicating that a type change (size change, steel type change, etc.) is to be carried out several times later or rolling is to be stopped is provided from the heating furnace 1 to the combustion control device 5, the corrected set temperature Is used, and the normal set temperature is maintained. Thereby, deterioration of the basic unit can be prevented.

Further, the tendency is determined when the measured rolling temperature decreases continuously for a predetermined number of times or more. Therefore, the function of correcting the set temperature is activated by an abnormal value (decrease) only once, and the temperature of the succeeding material becomes excessive. Never get higher.

FIG. 5 is a conceptual diagram showing the method of the present invention.
As described above, the target rolling temperature of the steel material to be rolled by the rolling mill is set based on data such as the type of the steel material, the size, the rolling conditions, the destination, and the like, and the rolling material can be rolled without any trouble. In addition, a lower limit management value of a target rolling temperature of a steel material is determined based on a material and a type of the steel material. In the present invention, a value higher than the target rolling temperature by α ° C. is set as a correction threshold for the set temperature. Then, when the actually measured rolling temperature satisfying the target rolling temperature drops, for example, three consecutive times and falls below the correction threshold, the set temperature is corrected. When the conventional control method responds to the decrease in the measured rolling temperature, the correction is performed when the average value of the measured rolling temperatures decreases the target rolling temperature. Therefore, in the case shown in FIG. 5, the correspondence is delayed by four.

After the set temperature is corrected, even if three steel materials are processed until the furnace temperature actually rises, according to the method of the present invention, the minimum value of the measured rolling temperature is equal to the target rolling temperature. The lower limit control value is not divided, but in the case of the conventional method, the lower limit control value is divided. Therefore, when the conventional method is used, an increase in load at the time of the rolling process in the subsequent process, processing defects such as a trip of the rolling mill occur, but when the method of the present invention is used, this can be prevented beforehand. .

The target rolling temperature may be determined separately from the lower limit control value, as described above, but the present invention is not limited to this, and based on the lower limit control value of the target rolling temperature, The value may be a value obtained by adding the mark width and a predetermined safety temperature. In this case, as low a target rolling temperature as possible can be set, whereby the load on the heating furnace is reduced.

[0032]

6 and 7 show specific examples of control using the conventional method and the method of the present invention, respectively. As the steel material S, a hollow round steel having a length of 70 mm is used, and the extraction pitch is set at 1 / min. The process shown in FIG. 2 is performed every 30 seconds by skipping the process of step S5, the process shown in FIG. 3 (step S5) is performed each time a steel material S is extracted, and the process shown in FIG.
Perform every second. The difference α between the correction threshold of the set temperature and the target rolling temperature is 30 ° C. The correction amount table 18 used by the set temperature correction means 17 is determined based on past experience, and corresponds to, for example, an extraction pitch as shown in FIG. Further, a material corresponding to the extraction pitch and the billet size may be used. After 4 minutes and 30 seconds, the lower limit value of the target rolling temperature decreased, but this was due to a change in the material of the steel material.

In the conventional method, as shown in FIG. 6, the measured rolling temperature continuously decreases, and the next processing timing of the steel material whose average measured rolling temperature is lower than the target rolling temperature, ie, 8 minutes and 30 seconds The setting temperature of the heating furnace 1 is increased later.
However, since the measured furnace temperature was slow to follow, the measured rolling temperature continued to decrease, and after 10 minutes (the eleventh steel material), the minimum value of the measured rolling temperature was lower than the lower limit control value of the target rolling temperature.

On the other hand, according to the method of the present invention, as shown in FIG.
The set temperature is corrected, and then the measured rolling temperature of the five steel materials further decreases, but the minimum value of the measured rolling temperature does not fall below the target extraction temperature lower limit (target rolling temperature lower limit management value) and rises again. Have begun to do. Therefore, the minimum value of the measured rolling temperature did not fall below the lower limit control value of the target rolling temperature.

[0035]

As described above, the method for controlling the temperature of the continuous heating furnace according to the present invention and the apparatus used for carrying out the method are based on the presumption that the measured rolling temperature is lower than the target rolling temperature and By raising the temperature, it is possible to complete the increase in the furnace temperature before the minimum value of the measured rolling temperature falls below the lower limit value of the target rolling temperature. The present invention has excellent effects, for example, it is possible to prevent the occurrence of processing defects, prevent deterioration of the basic unit, and improve the productivity.

[Brief description of the drawings]

FIG. 1 is a control block diagram in a temperature control device for a continuous heating furnace according to the present invention.

FIG. 2 is a flowchart showing a processing procedure of a temperature control method for a continuous heating furnace according to the present invention.

FIG. 3 is a flowchart showing a processing procedure of a target extraction temperature correction shown in FIG.

FIG. 4 is a flowchart showing a processing procedure of a set temperature correction shown in FIG. 2;

FIG. 5 is a conceptual diagram illustrating the method of the present invention.

FIG. 6 is a graph showing a specific control example using a conventional method.

FIG. 7 is a graph showing a specific control example using the method of the present invention.

FIG. 8 is a graph showing a correction amount table used by the set temperature correction means of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Rolling mill 3 Rolling thermometer 5 Combustion control device 8 Measured rolling temperature calculating means 9 Measured falling temperature calculating means 11 Skid mark width calculating means 17 Set temperature correcting means 18 Correction amount table 19 Setting temperature selecting means S ₁ , S ₂ ... S _i ... S _n steel

Claims (6)

[Claims] In a method for controlling the temperature of a continuous heating furnace for continuously heating a plurality of workpieces to be supplied to a rolling mill, the temperature of the workpieces during rolling is measured, and the obtained value is set to 1 Compared to the value before the individual, as a result of the comparison, when the value is lower than the value of the previous individual for a predetermined number of times, the set temperature of the continuous heating furnace is increased by a predetermined amount, and then lowered. Temperature control method of the continuous heating furnace. 2. An average value of the temperatures of the workpieces measured at a plurality of points of the workpieces during rolling of the workpieces provided to the rolling mill from the continuous heating furnace, and extracted from the continuous heating furnace. Using the extraction temperature of the material to be processed at the time, the predetermined target extraction temperature of the material to be processed is corrected, and the temperature of the continuous heating furnace is adjusted so that the extraction temperature of the material to be processed becomes the corrected target extraction temperature. And a method for controlling the temperature of a continuous heating furnace for continuously heating a plurality of workpieces to be supplied to a rolling mill based on the set temperature. Compared with the value, when the average value is lower than the average value of the previous individual for a predetermined number of consecutive times, the set temperature of the continuous heating furnace is increased by a predetermined amount corresponding to the processing conditions and / or the material to be processed, After that, the temperature control of the continuous heating furnace characterized by being lowered Law. 3. The amount of increase in the set temperature of the continuous heating furnace is:
3. The temperature control method for a continuous heating furnace according to claim 1, wherein the temperature is determined based on the number of materials to be processed extracted from the continuous heating furnace per unit time. 4. The method according to claim 1, wherein the set temperature of the continuous heating furnace is increased when the average value continuously drops a predetermined number of times from a previous value, and when the average value becomes smaller than a predetermined threshold value. The method for controlling the temperature of a continuous heating furnace according to claim 1, 2 or 3. 5. The method according to claim 1, wherein the set temperature of the continuous heating furnace is not increased when the number of materials to be processed is smaller than a predetermined number until the number of materials to be processed is changed. Temperature control method of continuous heating furnace. 6. An apparatus for controlling the temperature of a continuous heating furnace for continuously heating a plurality of workpieces to be given to a rolling mill in a hot rolling facility, wherein the temperature of the workpieces during rolling is measured. Means, means for comparing the measured value with the measured value of the previous individual, and a result of the comparison,
Means for outputting a command to raise the set temperature of the continuous heating furnace by a predetermined amount when the measured value is lower than the measured value of the previous individual for a predetermined number of times. Control device.