JP6327208B2 - Heating furnace extraction temperature prediction method and heating furnace extraction temperature prediction apparatus for billets - Google Patents

Description

  The present invention relates to a technique for predicting a furnace extraction temperature of a steel piece to be subjected to hot rolling or the like.

  The steel slab subjected to hot rolling is usually extracted by heating to a target extraction temperature targeted in a heating furnace and subjected to rolling. Therefore, when heating the steel slab in the heating furnace, it is necessary to heat the steel slab uniformly so as to reach the target extraction temperature. In order to uniformly heat the steel slab to the target extraction temperature, the furnace temperature of the heating furnace is required. It is necessary to monitor the furnace extraction temperature of steel and billets as needed. However, when the scale is generated on the surface of the steel slab extracted from the heating furnace, it is difficult to directly measure the furnace extraction temperature of the steel slab.

  On the other hand, in Patent Document 1, the atmospheric gas components in the heating furnace are measured using a carbon dioxide gas meter and a dew point meter, the gas emissivity is obtained from the measured value, and the overall heat absorption rate is obtained from the gas emissivity. A method for calculating and predicting the furnace extraction temperature of a billet is described. Further, in Patent Document 2, the steel slab temperature at the time of rolling is obtained based on the rolling load when the steel slab is rolled and the outer dimensions of the steel slab before and after rolling, and the steel slab reaches the rolling mill from the heating furnace. The method of calculating the furnace extraction temperature of a steel piece in consideration of the cooling up to is described.

In Patent Document 3, the surface of the steel slab extracted from the heating furnace is descaled with high-pressure water, and after reheating of the scale-removed steel slab surface is completed, the surface temperature of the steel slab is measured, It describes that the extraction temperature of the steel slab is calculated and predicted based on the temperature measurement value.
Furthermore, in Patent Document 4, air is blown to the surface of the steel slab extracted from the heating furnace to remove the scale, and after the reheating of the steel slab surface temperature is completed at the subsequent stage, the measured value is measured. Based on this, it is described that a steel slab surface temperature at the time of extraction in a heating furnace is calculated and predicted.

JP-A-6-192751 Japanese Unexamined Patent Publication No. 63-26214 Japanese Patent No. 4349177 Japanese Patent Application No. 2012-135522

  However, since the distribution of the atmospheric gas is not uniform in the heating furnace, the method described in Patent Document 1 has a very large temporal variation of the atmospheric gas components, and it is not possible to identify an appropriate overall heat absorption rate. There is a problem that it is extremely difficult. Further, it is difficult to accurately calculate the slab temperature from the rolling resistance and outer dimensions of the slab, and the cooling condition from the heating furnace to the rolling mill becomes a disturbance factor. In the method, there is a problem that the furnace extraction temperature of the billet cannot be accurately obtained.

  In the method described in Patent Document 3, since the surface temperature of the scale-removed billet is measured, the surface temperature of the billet can be measured without being affected by the scale. Since the heat transfer coefficient is very large and the temperature measurement value on the steel slab surface varies greatly depending on the boiling state of the descaling water, there is a problem that the furnace extraction temperature of the steel slab may not be accurately predicted.

Further, in the method described in Patent Document 4, the method of blowing air from the ejection nozzle can remove the primary scale that easily peels off the surface, but almost eliminates the tight scale that is strongly generated near the surface of the steel slab. As a result, there is a problem that it is difficult to measure the true value of the surface temperature of the slab.
And when the accuracy of the measured temperature cannot be guaranteed, the furnace extraction temperature of the steel slab cannot be accurately predicted by any subsequent calculation using the measured temperature.
In view of the circumstances as described above, an object of the present invention is to review a conventional temperature evaluation method for a heating furnace extracted steel material, and to provide a technique capable of obtaining the heating furnace extraction temperature of a steel piece with higher accuracy. It is said.

  In order to solve the problem, a method for predicting a furnace extraction temperature of a steel slab according to one aspect of the present invention is a method for predicting a furnace extraction temperature of a steel slab extracted from a heating furnace. A scale removing step for removing scale from the surface of the steel piece by spraying water and compressed air from the ejection nozzle to the surface of the extracted steel piece, and steel from which the scale has been removed after the scale removing step. Calculate the steel slab surface temperature at the time of furnace extraction based on the temperature measurement process to measure the surface temperature of the slab after the reheating of the steel slab surface is completed, and the temperature measurement value obtained in the above temperature measurement process. A heating furnace extraction temperature prediction step for predicting a heating furnace extraction temperature of the steel slab.

  Moreover, the heating furnace extraction temperature prediction apparatus of the steel slab which is one aspect of the present invention is an apparatus for predicting the heating furnace extraction temperature of the steel slab extracted from the heating furnace, and the steel slab extracted from the heating furnace. In order to remove scale from the surface of the steel slab with respect to the surface of the steel, a jet nozzle for spraying water and compressed air, respectively, and after the reheating of the steel slab surface to the spray of water and compressed air is completed The temperature measurement unit for measuring the surface temperature of the steel slab at the position, and the furnace slab extraction of the steel slab by calculating the steel slab surface temperature at the time of heating furnace extraction based on the temperature measurement value measured by the temperature measurement unit A heating furnace extraction temperature prediction unit for predicting the temperature.

  According to one aspect of the present invention, it is not necessary to remove the scale of the surface of a steel piece extracted from a heating furnace with high-pressure water having a predetermined pressure or higher, and depending on the heat transfer coefficient of descaling water and the boiling state of descaling water, It is possible to prevent the temperature measurement value on one surface from fluctuating greatly. In addition, by using both compressed air and spraying while suppressing the removal of scale with high-pressure water, it is possible to prevent the deficiency of the scale removal capability and to suppress the deviation of the temperature measurement of the billet surface from the true value. Become. Thereby, the heating furnace extraction temperature of the steel slab used for hot rolling etc. can be estimated accurately.

It is a figure explaining the structure of the heating furnace extraction temperature prediction apparatus which concerns on embodiment based on this invention. It is a conceptual diagram which shows the scale removal and temperature measurement position by the water and compressed air which concern on embodiment based on this invention. It is another conceptual diagram which shows the scale removal by water and compressed air which concerns on embodiment based on this invention, and a temperature measurement position. It is a figure which shows the example of the temperature change from the heating furnace extraction of a steel piece to temperature measurement.

Next, embodiments of the present invention will be described with reference to the drawings.
(Constitution)
In this embodiment, a case where the present invention is applied to a continuous production line for hot-rolled steel sheets will be described as an example.
As shown in FIG. 1, the continuous production line for hot-rolled steel sheets of the present embodiment includes a heating furnace 1 for heating a steel slab S and a rough rolling mill 2 for rough rolling the steel slab S heated in the heating furnace 1. Prepare. The steel piece S (slab) extracted from the extraction port of the continuous heating furnace 1 is transported toward the roughing mill 2 along a pass line defined by the plurality of transport rollers 3.

During the conveyance, the heating furnace extraction temperature prediction device removes a part of the scale formed on the upper surface of the steel slab S, measures the temperature of the upper surface of the steel slab S from which the scale has been removed, and measures the temperature. The furnace extraction temperature of the steel slab S is predicted based on the temperature. In the present embodiment, the case where the heating furnace extraction temperature is predicted from the temperature of the upper surface of the steel slab S is exemplified, but the temperatures of the upper and lower surfaces of the steel slab S are measured, and the temperature measurement value of the steel slab S is measured. The heating furnace extraction temperature may be predicted.
The furnace extraction temperature prediction device for the steel slab S of the present embodiment includes a scale removal jet nozzle 5, a temperature measurement unit 6, and a controller 4. The controller 4 includes a heating furnace extraction temperature prediction unit 4A and a scale removal evaluation unit 4B.

(Ejecting nozzle 5)
The ejection nozzle 5 removes the scale from the surface of the steel slab S by spraying water and compressed air toward the surface of the steel slab S being extracted from the heating furnace 1 and being conveyed toward the roughing mill 2. To do. In this embodiment, as shown in FIG. 2, the case where the scale produced | generated in the width direction center part of the steel slab S is removed in strip shape along a conveyance direction is illustrated. The removal portion of the scale may be performed in a spot manner.

  The scale removal jet nozzle 5 of the present embodiment includes a high-pressure water jet nozzle 5A and a compressed air jet nozzle 5B. The high-pressure water ejection nozzle 5A and the compressed air ejection nozzle 5B are arranged so as to be aligned in the conveying direction of the steel piece S. Then, the high pressure water 7 is ejected from the high pressure water ejection nozzle 5A toward the upper surface of the steel piece S, and then the compressed air 8 is ejected from the compressed air ejection nozzle 5B toward the upper surface of the steel piece S, thereby removing the scale. I do.

Here, although the case where the compressed air 8 is ejected after the high pressure water 7 is ejected is illustrated, the nozzle may be arranged so that the high pressure water 7 is ejected after the compressed air 8 is ejected.
Alternatively, as shown in FIG. 3, an ejection hole for ejecting the high-pressure water 7 and an ejection hole for ejecting the compressed air 8 are provided in the ejection portion of one nozzle, and the high-pressure water 7 and the compressed air are simultaneously ejected from one nozzle. You may comprise so that 8 may be ejected. In this case, for example, an ejection hole for high-pressure water is arranged at the center side of the ejection part of one nozzle, and an ejection hole for compressed air is arranged on the outer periphery so as to surround it, or the ejection part of one nozzle A jet hole for compressed air is arranged on the center side, and a jet hole for high-pressure water is arranged on the outer periphery so as to surround it.

The high pressure water jet nozzle 5A has a water pressure selected from a range of 0.35 MPa to 0.65 MPa in which the jet distance to the surface of the steel slab S is set between 50 mm and 200 mm and the pressure of water jetted from the nozzle 5A is selected from the range of 0.35 MPa to 0.65 MPa. It is good to set so that.
The compressed air ejection nozzle 5B has an air pressure selected from the range of 0.65 MPa or more and 0.35 MPa or less, with the ejection distance to the surface of the steel piece S set between 50 mm and 200 mm, and the pressure of the air ejected from the nozzle 5B. It is good to set so that.

(Temperature measuring unit 6)
The temperature measuring unit 6 is disposed on the downstream side of the ejection nozzle 5 and at a position where it is estimated that the reheating of the surface of the steel piece S with respect to the spraying of the water 7 and the compressed air 8 is completed. What is necessary is just to estimate the position where the recuperation was completed from the conveyance speed of the steel slab S and the temperature drop at the time of scale removal.
The temperature measurement unit 6 of the present embodiment includes a first temperature measurement unit 6A that measures the temperature of the surface of the steel slab S at the scale removal position, and a second temperature that is the temperature of the surface of the steel slab S that has not been subjected to scale removal. And a temperature measuring unit 6B. Each temperature measurement part 6A, 6B consists of a radiation thermometer, for example.

Here, a plurality of first temperature measurement units 6A and a plurality of second temperature measurement units 6B may be arranged. In this case, for example, an average value of temperatures measured by the plurality of first temperature measuring units 6A is employed. Further, an average value of the temperatures measured by the plurality of second temperature measuring units 6B is employed. When a plurality of second temperature measuring units 6B are arranged, it is preferable to arrange the second temperature measuring units 6B so as to line up along the width direction of the steel slab S, for example, on both the left and right sides of the scale removal position. In the case of arranging a plurality of temperatures, it is possible to obtain the temperature in consideration of uneven heating in the heating furnace 1.
A signal corresponding to the surface temperature of the steel slab S measured by each temperature measuring unit 6 is supplied to the controller 4.

(Controller 4)
As described above, the controller 4 includes the heating furnace extraction temperature prediction unit 4A and the scale removal evaluation unit 4B.
(Heating furnace extraction temperature prediction unit 4A)
The heating furnace extraction temperature prediction unit 4A calculates the surface temperature of the steel slab S at the time of extraction from the heating furnace based on the temperature measurement value formed from the signal from the first temperature measurement unit 6A, and the heating furnace for the steel slab S described above. Predict the extraction temperature (average temperature in the plate thickness direction when extracting from the heating furnace). The predicted heating furnace extraction temperature is supplied to, for example, a heating furnace control unit or a rolling control unit.

  The heating furnace extraction temperature predicting unit 4A is used when the surface temperature of the steel slab S measured by the first temperature measuring unit 6A, the air temperature around the steel slab S, and the steel slab S are cooled by natural cooling. When the steel slab S is cooled by the heat transfer coefficient, the specific heat of the steel slab S, the elapsed time from the time when the steel slab S is extracted from the furnace to the surface temperature measurement, and the air and water ejected from the ejection nozzle Based on the heat transfer coefficient and the temperature of the air and water ejected from the ejection nozzle onto the surface of the steel slab S, the surface temperature of the steel slab during the heating furnace extraction is calculated.

Furnace extraction temperature prediction unit 4A of this embodiment, so as to predict by calculating the heating furnace extraction temperature of the steel strip S seeking billet surface temperature T _A at the time of the heating furnace extraction from below (1) It is configured.
T _A = T _E + ΔT _a1 + ΔT _c −ΔT _R + ΔT _a2 (1)

here,
T _E : Surface temperature measurement value by the first temperature measurement unit 6A ΔT _a1 : The steel piece S from point A (heating furnace extraction point) to point B (scale removal start point by the ejection nozzle) shown in FIG. the amount of temperature drop _(T A _-T B)
ΔT _c : temperature drop amount of steel slab S from point B shown in FIG. 1 to point C (end point of scale removal by the ejection nozzle) (T _B −T _C )
[Delta] T _R: D from the point C to the point shown in Figure 1 the temperature rise of the steel strip S down to (recuperation completion point of the surface of the steel strip S) _(T D _-T C)
ΔT _a2 : temperature drop amount of steel slab S from point D to point E (temperature measurement point by first temperature measurement unit 6A) shown in FIG. 3 (T _D −T _E )

  Respectively.

The temperature drop amount ΔT _{a1 in the} equation (1) is expressed by the following equation (2).

here,
T: Surface temperature of the steel slab S (T = 0, T = T _A )
S: Surface area of the slab S l: Typical thickness of the surface of the slab S Q: Amount of heat lost by the heat conduction to the inside of the slab S α _a : Heat transfer coefficient when the slab S is cooled by natural air cooling C: Specific heat of steel slab S t _a1 : Elapsed time from point A to point B shown in FIG. 1 T _a : Air temperature around steel slab S

Further, the temperature drop amount ΔT _{c in the} equation (1) is expressed by the following equation (3).

here,
α _c1 : Heat transfer coefficient when the steel slab S is cooled by water ejected from the high pressure water ejection nozzle 5A α _c2 : When the steel slab S is cooled by the compressed air ejected from the compressed air ejection nozzle 5B Heat transfer coefficient C: Specific heat of steel slab S _Tc : Elapsed time from point B to point C shown in FIG. 1 (time for spraying water ejected from nozzle 5A for high-pressure water ejection to steel slab. (Since the compressed air ejected from the air ejection nozzle 5B is blown, the nozzle 5A and the nozzle 5B have the same time)
T _c1 : temperature of water ejected from the high pressure water ejection nozzle 5A T _c2 : temperature of air ejected from the compressed air ejection nozzle 5B

Further, (1) increase in temperature [Delta] T _R and the amount of temperature drop [Delta] T _a2 of formula is represented by below equation (4).

here,
α _a : Heat transfer coefficient when billet S is cooled by natural air cooling C: Specific heat of billet S t _R : Elapsed time from point C to point D shown in FIG. 1 t _a2 : Point D shown in FIG. Represents the elapsed time from point to point E.
Here, FIG. 4 is a diagram illustrating an example of the relationship between the surface temperature of the steel slab S and the elapsed time since the extraction with the heating furnace.

As illustrated in FIG. 4, the surface temperature of the steel slab S is the furnace extraction temperature T _A = about 1200 ° C. at the point A in FIG. 1 immediately after being extracted from the heating furnace 1, but is then naturally air-cooled thereafter. At point B, the temperature falls to T _B = about 1175 ° C. Then, the surface of the steel slab S is forcibly cooled by water and air ejected from the ejection nozzles 5A and 5B from the point B to the point _C. = 1165 ° C. Thereafter, recuperation is performed on the surface of the steel slab S, and the temperature of the steel slab S rises to T _D = about 1170 ° C. at point D when the recuperation is completed. Thereafter, the surface of the steel slab S is naturally air-cooled, and at the point E measured by the first temperature measuring unit 6A, the temperature of the steel slab S falls to T _E = about 1160 ° C.
Therefore, by solving the above (1) to (4), it is possible to calculate a billet surface temperature T _A at the time of the heating furnace extraction, heating furnace of steel strip S from the calculated value of the billet surface temperature T _A The extraction temperature can be predicted.

(Scale removal evaluation unit 4B)
The scale removal evaluation part 4B is based on the first temperature measured by the first temperature measurement part 6A acquired from the steel slab S and the second temperature measured by the second temperature measurement part 6B. The state of scale removal by the jetted water and the compressed air 8 is evaluated. That is, the state of scale removal is evaluated by the degree of deviation between the first temperature and the second temperature acquired from the same steel piece S.

Here, the temperature of the surface of the steel slab S where the scale is removed is higher than the temperature of the surface of the steel slab S where the scale exists. For this reason, when the scale is not sufficiently removed, the temperature difference between the first temperature and the second temperature is reduced accordingly.
Moreover, since the target heating temperature in the heating furnace 1 is determined according to a request from the next process such as a rough rolling process, the range of the surface temperature of the steel slab S continuously extracted in the heating furnace 1 is naturally constant. Specified in range. Moreover, it is limited to the fixed range also about the heating conditions in the heating furnace 1 of the steel piece S heated continuously. For this reason, it seems that the heating situation of each steel slab S and the formation situation of the scale by heating do not change significantly. In particular, among the steel pieces S that are continuously heated, the closer the steel piece S is to the steel piece S that is the object of temperature measurement this time, the closer the state is.

The scale removal evaluation unit 4B of the present embodiment performs processing as follows.
That is, the scale removal evaluation unit 4B of the present embodiment obtains the temperature difference ΔT between the first temperature and the second temperature acquired for each steel piece S, and sequentially stores them in the storage unit 9.
Each time the temperature difference ΔT is stored in the storage unit 9, the scale removal evaluation unit 4 </ b> B acquires the temperature obtained from the latest preset number of steel slabs S among the temperature differences ΔT stored in the storage unit 9. An average value ΔTm of the difference ΔT is calculated. The set number is selected from a range of 3 to 6, for example. In this embodiment, the number is four. In addition, when the steel grade heated is changed, it is preferable to use the data of the same steel grade. Moreover, when there is no information on the latest temperature difference of the preset number, the average value of the temperature differences ΔT of the approximate target temperatures of the same steel type may be temporarily employed. In this case, an average value of temperature difference data of about 10 or more within half a year is preferable.

  Next, the scale removal evaluation unit 4B determines whether or not the absolute value of the difference (ΔTm−ΔTi) between the temperature difference ΔTi and the average value ΔTm acquired this time is equal to or greater than a preset threshold value. If the difference is more than the threshold, it is determined that the scale removal is abnormal. The threshold value is set based on experiments and known theoretical formulas for variations in heating by the heating furnace 1. For example, the threshold is set to 10% or more and 20% or less, for example, 10%. There may be a plurality of thresholds, and the scale removal state may be graded and evaluated.

Here, the evaluation of scale removal is not limited to the above content. For example, the change of the temperature difference ΔT may be sequentially obtained, and if the temperature difference ΔT tends to be small, the scale removal may be evaluated according to the tendency.
Alternatively, the scale removal may be evaluated simply from the temperature difference ΔT acquired this time.
Here, if the scale removal evaluation unit 4B determines that the scale removal has become insufficient, the ejection pressure of water or high-pressure air ejected to the steel slab S, the ejection amount per unit time, the ejection time, etc. are increased. Perform the process.
Here, the process of jetting water and compressed air by the jet nozzle 5 for removing scale constitutes the scale removing process. Temperature measurement by the temperature measurement unit 6 constitutes a temperature measurement process. The processing of the heating furnace extraction temperature prediction unit 4A constitutes the heating furnace extraction temperature prediction step. The processing of the scale removal evaluation unit 4B constitutes the scale removal evaluation process.

(Operation other)
Water 7 and compressed air 8 are sprayed onto the surface of the steel slab S extracted continuously from the heating furnace 1 to remove the scale 10 from a part of the surface of the steel slab S, and then the surface temperature of the steel slab S is measured. .
Here, when scale removal is performed using only high-pressure water, the heat transfer coefficient of high-pressure water is very large, and the temperature measurement value on the surface of the steel slab S varies greatly depending on the boiling state of the high-pressure water. For this reason, there exists a possibility that the heating furnace extraction temperature of the steel slab S cannot be estimated correctly. On the other hand, when the scale removal is performed only with compressed air, the primary scale that is easily peeled off from the surface of the steel slab S can be removed, but there is a possibility that the tight scale that is strongly generated near the surface of the steel slab S can hardly be removed. As a result, it is difficult to measure the true value of the steel slab surface temperature.

  On the other hand, in this embodiment, the scale removal is performed using both the water 7 and the compressed air 8 so that the pressure of the water 7 and the spraying amount of the water 7 for scale removal can be scaled only with water. The required scale removal can be performed in a state of being kept low compared to the case of removal. Moreover, it can suppress that the measured temperature value of the steel piece S surface fluctuates greatly depending on the heat transfer coefficient of the water 7 and the boiling state of the water 7.

Thereby, it is possible to suppress the temperature measurement on the surface of the steel slab S from greatly deviating from the true value. Therefore, the furnace extraction temperature of the steel slab S used for the next process such as hot rolling can be accurately predicted.
That is, since the temperature of the part where scale removal has been performed is performed after reheating of the surface of the steel slab S is completed while suppressing fluctuations due to the heat transfer coefficient of the descaling water and the boiling state of the descaling water, accurate steel The surface temperature of the piece S can be measured. Therefore, by predicting the heating furnace extraction temperature of the steel slab S based on the temperature measured values of the first temperature measuring unit 6A and the second temperature measuring unit 6B, the steel slab S used for hot rolling or the like. It is possible to accurately predict the furnace extraction temperature.

Moreover, by comparing the heating furnace extraction temperature of the steel slab S predicted by the heating furnace extraction temperature prediction device with the heating furnace extraction temperature of the steel slab S predicted based on the temperature control model in the heating furnace, It becomes possible to correct the overall heat absorption rate and improve the medium accuracy of the target extraction temperature.
Further, by the billet surface temperature T _A at the time of the heating furnace extraction (1) determined from equation predicting the furnace extraction temperature of the steel strip S, a heating furnace of steel strip S to be subjected, such as hot rolling extraction The temperature can be predicted more accurately.

In the present embodiment, the scale removal evaluation unit 4B evaluates the scale removal, so that it is possible to determine whether or not the temperature measurement value has deviated from the true value, and the measurement value abnormality can be grasped at an early stage.
Here, in this embodiment, the heating furnace extraction temperature is predicted based on the temperature of the upper surface side of the steel slab S, but the heating furnace extraction temperature is predicted based on the temperature of the lower surface or the upper and lower surfaces of the steel slab S. May be.

Moreover, after colliding in a solid state with the surface of the steel slab S against the jetted compressed air 8, particles that evaporate or melt may be included to improve the scale removal capability. In this case, the scale can be removed only with compressed air.
Examples of the material of the granule include a solid made of dry ice (trade name) or baking soda. These do not cause a chemical change in the steel slab S, are harmless to the human body, and do not cause problems in terms of quality and environmental hygiene.

Moreover, in the said embodiment, the case where scale removal is performed with the water 7 and the compressed air 8 is illustrated. On the other hand, the scale removal evaluation unit 4 </ b> B may evaluate the scale removal while removing the scale using only the high-pressure water 7.
Here, the scale removal evaluation unit 4B determines that the scale removal is abnormal. The scale removal is insufficient, and the temperature measurement of the first temperature part is abnormal. That is, the scale removal evaluation unit 4B can be regarded as performing an abnormal evaluation of the temperature measurement value.

Next, examples of the present invention will be described.
<Example>
Scale removal is performed by sequentially ejecting water and compressed air 8 from the water and compressed air ejection nozzle toward the upper surface of the steel piece S (plate width 1.25 m, plate thickness 230 mm) extracted from the heating furnace 1. did.
At this time, the ejection distance of water and compressed air 8 is 150 mm, and the ejection condition is a water density of 5510 L / m ² . min (pre-nozzle water pressure 0.45 MPa) and compressed air 8700 Nm3 / h (pre-nozzle compressed air pressure 0.45 MPa).

  Then, after removing the scale from the surface of the steel slab S, the surface temperature of the steel slab S is measured by a radiation thermometer after the reheating of the surface of the steel slab S is completed, and based on the temperature measurement value of the radiation thermometer. When calculating and predicting the heating furnace extraction temperature of the slab S, the steel slab S overheating temperature in the heating furnace 1, the heating furnace 1 unit, and the quality defect occurrence rate index due to insufficient heating were investigated. The results are shown in Table 1.

<Comparative example>
Further, only the high-pressure descaling water was ejected from the spray nozzle onto the surface of the steel piece S extracted from the heating furnace 1, and the scale was removed.
In the comparative example, the distance of water was set to 150 mm, and the ejection condition was set to a water density of 170,000 L / m ² · min (nozzle pre-water pressure 15 MPa).

And like the Example, the steel slab S overheating temperature in the heating furnace 1, the heating furnace 1 basic unit, and the quality defect occurrence rate parameter | index resulting from insufficient heating were investigated. The results are listed in Table 1.

As can be seen from Table 1, in the comparative example, the average of the steel slab S superheating temperature was around 31 ° C., whereas in the example, the average of the steel slab S superheating temperature was less than 10 ° C.
Further, when the basic unit of the heating furnace in the comparative example is 1.0 and the quality defect occurrence rate index resulting from unexpected heating is 1.0, in the example, 0.9 and the quality defect occurrence rate index are 0.5. It became less than.
Thus, in the Example, it turns out that a heating furnace extraction temperature can be estimated accurately, suppressing the temperature fluctuation of temperature measurement.
Here, in the configuration of the embodiment, when water is ejected from the central portion from the same nozzle and compressed air 8 is ejected from the peripheral portion, and when compressed air 8 is ejected from the peripheral portion from the central portion from the same nozzle. But I tried it. Even in this case, it has been confirmed that the same effect as that of the example can be obtained.

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Rough rolling mill 3 Conveying roller 4 Controller 4A Heating furnace extraction temperature prediction part 4B Scale removal evaluation part 5 Injection nozzle 5A High pressure water injection nozzle 5B Compressed air injection nozzle 6 Temperature measurement part 6A 1st temperature measurement part 6B Second temperature measurement unit 7 High pressure water 8 Compressed air 9 Storage unit S Steel slab ΔT Temperature difference ΔTi Temperature difference ΔTm Average value

Claims (6)

A method for predicting a furnace extraction temperature of a steel slab extracted from a furnace,
A scale removal step of removing scale from the surface of the steel piece by blowing water and compressed air from the ejection nozzle to the surface of the steel piece extracted from the heating furnace,
After the scale removal step, a temperature measurement step of measuring the surface temperature of the steel slab from which the scale has been removed after the reheating of the steel slab surface is completed,
A furnace extraction temperature prediction step for calculating a steel slab surface temperature at the time of furnace extraction based on the temperature measurement value obtained in the temperature measurement process and predicting a furnace extraction temperature of the steel slab, and
I have a,
The temperature measurement in the temperature measurement step measures the first temperature, which is the temperature of the steel slab surface at the scale removal position, and is the temperature of the steel slab surface where scale removal has not been performed in the scale removal step. Measure the temperature of 2,
Furthermore, the steel slab heating furnace extraction temperature prediction method characterized by including the scale removal evaluation process which evaluates the scale removal by the said scale removal process from said 1st temperature and said 2nd temperature . In the scale removal evaluation step, the temperature difference between the first temperature and the second temperature is recorded for each extracted steel slab, and the average of each temperature difference ΔT in a plurality of steel slabs measured most recently is recorded. 2. The steel according to claim 1 , wherein a value ΔTm is obtained, and when the absolute value of the difference between the temperature difference measured this time and the average value ΔTm deviates more than a preset threshold value, it is determined that the scale removal is abnormal. Method for predicting the extraction temperature of a piece of heating furnace. In the heating furnace extraction temperature prediction step, the surface temperature of the steel slab portion from which the scale measured in the temperature measurement step has been removed, the air temperature around the steel slab, and the steel slab are cooled by natural cooling. The steel slab is cooled by the heat transfer coefficient, the specific heat of the steel slab, the elapsed time from the extraction of the steel slab to the surface temperature measurement, and the air and water jetted from the jet nozzle. And calculating the steel slab surface temperature at the time of extraction in the heating furnace based on the heat transfer coefficient at the time of heating and the temperature of air and water jetted from the jet nozzle to the surface of the steel slab. The method for predicting the extraction temperature of a steel slab according to claim 1 or claim 2 . An apparatus for predicting a heating furnace extraction temperature of a steel piece extracted from a heating furnace,
In order to remove scale from the surface of the steel slab with respect to the surface of the steel slab extracted from the heating furnace, an ejection nozzle for spraying water and compressed air, respectively,
A temperature measuring unit for measuring the surface temperature of the steel slab from which the scale has been removed, at a position after completion of recuperation of the steel slab surface with respect to the water and compressed air;
A furnace extraction temperature prediction unit that calculates a steel slab surface temperature during heating furnace extraction based on a temperature measurement value measured by the temperature measurement unit and predicts a furnace extraction temperature of the steel slab, and
I have a,
As said temperature measurement part, it has the 1st temperature measurement part which measures the temperature of the steel slab surface of a scale removal position, and the 2nd temperature measurement part which is the temperature of the steel slab surface where scale removal is not performed ,
And a scale removal evaluation unit for evaluating scale removal by the water and compressed air from the first temperature measured by the first temperature measurement unit and the second temperature measured by the second temperature measurement unit; a heating furnace extraction temperature predicting apparatus of the steel strip, characterized in that it comprises a. The scale removal evaluation unit records the temperature difference between the first temperature and the second temperature for each extracted steel slab, and averages the temperature differences ΔT for a plurality of steel slabs measured most recently. The steel slab according to claim 4 , wherein a value ΔTm is obtained, and when the absolute value of the difference between the temperature difference measured this time and the average value ΔTm deviates more than a set threshold value, it is determined that the scale removal is abnormal. Furnace extraction temperature prediction device. The heating furnace extraction temperature predicting unit is a surface temperature of the steel piece part from which the scale measured in the temperature measuring step is removed, the air temperature around the steel piece, and the steel piece is cooled by natural cooling. The steel slab is cooled by the heat transfer coefficient, the specific heat of the steel slab, the elapsed time from the extraction of the steel slab to the surface temperature measurement, and the air and water ejected from the ejection nozzle. And calculating the steel slab surface temperature at the time of extraction in the heating furnace based on the heat transfer coefficient at the time of heating and the temperature of air and water jetted from the jet nozzle to the surface of the steel slab. Item 6. The apparatus for predicting the extraction temperature of a steel slab according to item 4 or claim 5 .

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