JPH0550143A - Method for predicting rolling temp. of steel sheet on hot rolling - Google Patents

Abstract

PURPOSE:To predict a rolling temperature with high precision by correcting the predicted value of this rolling temperature based on the difference between a surface temperature of steel sheet measured after roughing and a estimated surface temperature based with a rolling temperature prediction. CONSTITUTION:The surface temperature of the steel sheet 1 is measured with a thermometer 8 after de-scaling and before a roughing starting. A sampling temperature of the above steel sheet or a rolling temperature distribution of wall thickness direction of the steel sheet 1 at the measured time is estimated based on this front surface temperature. The rolling temperature prediction after he temperature measuring time point is executed by being made this estimated result as the initial time value. On the other hand, the surface temperature of the steel sheet 1 is measured with the thermometer 9 after roughing, and the rolling temperature prediction after roughing is executed by correcting the estimated sampling temperature and the estimated rolling temperature distribution with the above rolling temperature prediction based on the difference of the above front surface temperature and the estimated surface temperature based on the above rolling temperature prediction. Therefore, the rolling temperature can be predicted with high precision by correcting the predicted value of the rolling temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for predicting a rolling temperature of a steel sheet being rolled in a hot rolling line.

[0002]

2. Description of the Related Art A technique for predicting rolling temperature in hot rolling is
It is an important basic element technology of the plate thickness / flatness control and the plate width / planar shape control necessary for manufacturing a steel plate with a high yield and good dimensional accuracy. This is an essential technology for.

Conventionally, as means for predicting the rolling temperature,
The following measures such as and are taken.

In the rough rolling process, the surface temperature is predicted and used as the rolling temperature. In the finish rolling step, the average temperature at the time of temperature measurement is estimated from the surface temperature measured after rough rolling, and the rolling temperature after the measurement time is predicted based on that average temperature.

The extraction temperature is estimated from the surface temperature measured after the completion of the HSB (horizontal scale breaker), and the rolling temperature in all the processes from rough rolling to finish rolling is predicted with this as a base point.

[0006]

However, the above-mentioned conventional means have the following problems, respectively.

That is, in the case of the means, it is impossible to regard the surface temperature as the rolling temperature, so that the prediction accuracy becomes poor. Further, when the average temperature is estimated from the measured temperature, the temperature history in the previous process is not taken in, so that the prediction accuracy becomes poor when the plate thickness is large.

Further, in the case of the means, since the surface temperature is governed by the temperature near the surface of the steel sheet at the time of measuring the temperature after HSB, it is difficult to incorporate the temperature deviation inside the steel sheet into the estimated value of the extraction temperature. is there. Therefore, when there is a temperature deviation at the time of extraction, it is not possible to accurately predict the rolling temperature in the finish rolling step which is particularly important for temperature control.

The present invention is intended to solve such a problem, and is a method for rolling a steel sheet in hot rolling, which enables highly accurate prediction of the rolling temperature in an integrated process from a rough rolling process to a finish rolling process. An object is to provide a temperature prediction method.

[0010]

In order to achieve the above object, the method for predicting the rolling temperature of a steel sheet in hot rolling according to the present invention is to measure the surface temperature of the steel sheet after descaling and before starting rough rolling, Based on the surface temperature, the extraction temperature of the steel sheet or the strip temperature rolling temperature distribution of the steel sheet at the time of measurement is estimated, and the estimation result is used as an initial value to predict the rolling temperature after the time of temperature measurement, while Measure the surface temperature of the steel sheet after rolling, based on the difference between the surface temperature and the estimated surface temperature based on the rolling temperature prediction, correct the estimated extraction temperature and the estimated rolling temperature distribution by the rolling temperature prediction, It is characterized by predicting the rolling temperature after rough rolling.

[0011]

[Operation] Since the surface temperature is controlled by the temperature near the surface of the steel sheet at the time of measuring the temperature after descaling, it is difficult to incorporate the temperature deviation inside the steel sheet into the estimated value of the extraction temperature. In the rolling temperature prediction method of the steel sheet in the hot rolling of the invention, based on the difference between the surface temperature of the steel sheet measured after rough rolling and the estimated surface temperature based on the rolling temperature prediction, by correcting the rolling temperature prediction value, The rolling temperature can be predicted with high accuracy.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for predicting a rolling temperature of a steel sheet in hot rolling as an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of an apparatus to which the method of this embodiment is applied. is there.

Before explaining the rolling temperature prediction procedure according to the method of the present embodiment, an apparatus to which the method of the present embodiment is applied will be described with reference to FIG. 1. As shown in FIG. 2, after being heated by the heating furnace 3, after being descaled by a horizontal scale breaker (HSB) 4 and a vertical edger (VE) 5, a coarse mill 6
Rough rolling is carried out, and further finish rolling is carried out by the finishing mill 7.

In FIG. 1, 8 is a thermometer for measuring the surface temperature of the steel sheet 1 after descaling and before the start of rough rolling,
Reference numeral 9 is a thermometer for measuring the surface temperature of the steel sheet 1 after the rough rolling, and the rolling temperature of the steel sheet 1 is predicted in the following manner based on the measurement results of the thermometers 8 and 9.

That is, first, the surface temperature of the steel sheet 1 is measured by the thermometer 8 at the time after the descaling by the HSB 4 and the VE 5 and before the start of rolling by the rough mill 6, and the steel sheet 1 is extracted based on the measured surface temperature. The temperature or rolling temperature distribution of the steel sheet 1 in the thickness direction at the time of measurement is estimated (process 1). The estimation method is as follows.

As a precondition, the temperature distribution T (x) in the plate thickness direction at the time of measurement is represented by an Nth degree polynomial expressed by the following equation (1).

[0017]

[Equation 1]

Where x is the position in the plate thickness direction of the steel plate 1, T _S
Is the surface temperature of the steel plate 1 measured by the thermometer 8, T _C is the plate thickness center temperature of the steel plate 1, and H is the slab thickness.

Here, the medium thickness temperature T _C is derived by the following equation (4) based on the one-dimensional heat conduction equation in the thickness direction of the steel sheet 1.

[0020]

[Equation 2]

However, S is the number of cooling modes from extraction to different temperature measurement positions after descaling, Δt _j is the cooling time in each cooling mode, and N and D _j are the following equations (5) and (6), respectively. )
Is represented by.

N = g (H, Δt ₁ ) (5) D _j = f _j (H, Δt _j ) (6) (4) The plate thickness central temperature T _C is obtained from the equations, and (2), (3) Besides A and B are determined by the equation, N is determined by the equation (5), and the temperature distribution T (x) in the plate thickness direction at the time of temperature measurement is
It is calculated using equation (1).

Next, since T _C = T ₀ (extraction temperature) when H ≧ 150 mm, the extraction temperature can be calculated by the equation (4).

With the extraction temperature estimated as described above or the temperature distribution in the plate thickness direction at the time of measurement as an initial value, in the rough rolling process by the rough mill 6, the rolling temperature prediction is performed in consideration of the temperature inside the steel sheet 1. The rolling temperature prediction method is as follows.

The temperature distribution in the plate thickness direction of the steel plate 1 is represented by an Nth degree polynomial expressed by the following equation (7).

[0026]

[Equation 3]

From the model based on the analytical solution of the one-dimensional heat conduction equation in the plate thickness direction of the steel sheet 1, the basic equations A, B and N shown in the following equations (8) to (10) are created.

A = f ₁ (α _j , H _j , Δt _j ) (8) B = f ₂ (α _j , H _j , Δt _j ) (9) N = f ₃ (α _j , H _j , Δt _j (10) where α _j is the heat transfer coefficient according to the cooling mode of each rolling process, and Δt _j is the cooling time.

In each rolling process, the temperature distribution in the plate thickness direction of the steel sheet 1 can be calculated by the equation (7) by obtaining A, B and N by the equations (8) to (10). As a result, the steel sheet 1 It is possible to make predictions for each of the average temperature, the center temperature of the plate thickness, and the surface temperature.

However, as described above, when estimating the extraction temperature from the measured surface temperature after descaling, it is difficult to incorporate the temperature deviation inside the steel sheet 1 into the estimated value.

Therefore, after the rough rolling step (between the rough mill 6 and the finish rolling mill 7), the surface temperature of the steel sheet 1 is measured by the thermometer 9, and the measured temperature and the equations (7) to (10) are used. Forecast
Based on the calculated difference from the surface temperature at the time of measurement, (1)
~ By correcting the extraction temperature estimated by equation (6) and the predicted value of the rolling temperature at the time of measurement, it becomes possible to accurately predict the rolling temperature in the finish rolling process.
(Process 2).

Specific numerical examples when the prediction method of this embodiment is actually applied will be described with reference to FIGS.

(A) For example, as a steel plate, the slab thickness 28
Use 0 mm, transfer thickness 59 mm, finish thickness 15 mm.
Further, as a result of obtaining the extraction temperature of the target steel sheet and the temperature transition in each rolling process in order to grasp the effect before carrying out the present method, the results are as follows.

(B) The temperature at the time of extraction of this steel sheet was obtained by calculating the temperature in the heating furnace of the slab by the two-dimensional difference method.
The average temperature was 1205 ° C.

(C) When the one-dimensional heat conduction equation is solved by the difference method using the above extraction temperature as the initial temperature, the temperature transition of the steel sheet is obtained as shown in FIG. 2, and the surface temperature is ± 10 with the measured value. Since there is a coincidence in the error of ° C, the accuracy verification of this method is performed by comparison with the value obtained by this difference method.

(D) The results of carrying out the present method on the above steel sheets will be described below.

(E) The surface temperature measured after descaling and before rough rolling is 1107 ° C. The extraction temperature estimated by this method based on this measured temperature is 1230 ° C uniformly in the plate thickness direction, and the average temperature (120
5 ° C) is 25 ° C.

(F) Then, the estimated extraction temperature (1230
As shown in FIG. 3, the prediction error of the rolling temperature predicted by this method based on (° C.) is 20 to 25 ° C. in the rough rolling process and 15 to 20 ° C. in the finish rolling process, as shown in FIG.

(G) Next, the estimated temperature in (e) and the predicted value of the rolling temperature in (f) are corrected as follows by the measured temperature after rough rolling and before the start of finish rolling.

(H) That is, the surface temperature of the steel sheet measured after rough rolling and before the start of finish rolling is 1001 ° C., while the surface temperature predicted by the method (f) at the time of temperature measurement is 1024 ° C. The difference between the two is 23 ° C.

(I) Based on this difference of 23 ° C., the estimated extraction temperature is uniformly corrected to 1207 ° C. in the plate thickness direction, and the difference from the average temperature 1205 ° C. during actual extraction is 2 ° C.

(J) On the other hand, the predicted value of the rolling temperature also
By correcting with this difference of 23 ° C., the prediction error of the finish rolling temperature is about 1 to 2 as shown in FIG.
It becomes 2 ° C and the rolling temperature can be predicted with high accuracy.

As described above, according to the rolling temperature predicting method of this embodiment, the rolling temperature can be predicted with high accuracy in the integrated process from the rough rolling process to the finish rolling process.

The extraction temperature of the steel sheet estimated by the method of the present invention may be adopted as a learning term for the slab temperature control of the heating furnace.

[0045]

As described in detail above, according to the method for predicting the rolling temperature of a steel sheet in hot rolling of the present invention, the surface temperature of the steel sheet measured after the rough rolling and the estimated surface temperature based on the rolling temperature prediction are calculated. By correcting the rolling temperature predicted value based on the difference, there is an effect that the rolling temperature can be predicted with high accuracy in the integrated process from the rough rolling process to the finish rolling process.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an apparatus to which a rolling temperature prediction method for a steel sheet in hot rolling as an embodiment of the present invention is applied.

FIG. 2 is a graph showing a temperature transition in each rolling process of the steel sheet of this example obtained by the difference method.

FIG. 3 is a graph showing the rolling temperature in each rolling process predicted by the method of the present example, with the extraction temperature estimated by the process 1 as an initial value.

FIG. 4 is a graph showing rolling temperature after correction according to process 2.

[Explanation of symbols]

 1 Steel plate 2 Batch furnace 3 Heating furnace 4 Horizontal scale breaker (HSB) 5 Vertical edger (VE) 6 Coarse mill 7 Finishing mill 8.9 Thermometer

Claims (1)

[Claims] 1. When predicting an extraction temperature and a rolling temperature of a steel sheet during rolling in a hot rolling line, a surface temperature of the steel sheet is measured after descaling and before rough rolling is started, and the surface temperature is measured based on the surface temperature. The strip temperature rolling temperature distribution of the steel sheet at the extraction temperature of the steel sheet or at the time of measurement is estimated, and while the rolling temperature is predicted after the temperature measurement time using the estimation result as an initial value, the surface of the steel sheet after the rough rolling is performed. Temperature is measured, based on the difference between the surface temperature and the estimated surface temperature based on the rolling temperature prediction, the estimated extraction temperature and the estimated rolling temperature distribution by the rolling temperature prediction are corrected, and the rolling temperature prediction after the rough rolling is performed. A method for predicting the rolling temperature of a steel sheet in hot rolling, which comprises performing