JP2001353512A - Method for controlling temperature of hot strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling the temperature of a hot strip by which the finishing temperature of the whole steel plate is made to coincide with the target value of the finishing temperature more accurately. SOLUTION: The finishing temperature on the outlet side of a hot rolling mill 3 is controlled so as to be made to coincide with the target value of the finishing temperature on the outlet side of the hot rolling mill 3 by calculating the target value of temperature distribution in the longitudinal direction of a rough bar 1 on the outlet side of an induction heating device 2 from the target temperature of the finished plate on the outlet side of the hot rolling mill 3 for rolling the rough bar 1 or the target temperature distribution in the longitudinal direction of the rough bar 1, calculating the target value of temperature rising of the rough bar 1 from detected temperature detected with a temperature detector 5 which is installed on the inlet side of the induction heating device 2 and the target value of the finishing temperature, performing the feedforward control of the induction heating device 2 in accordance with a subject place with a timing pulse generator 6 and making the temperature distribution in the longitudinal direction of the rough bar 1 on the outlet side of the induction heating device 2 coincide with the target value of the distribution of the finishing temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling the temperature of a hot-rolled steel strip in a hot rolling mill.

[0002]

2. Description of the Related Art In hot finish rolling, it is well known that the metallurgical and mechanical properties of a steel strip vary greatly depending on the rolling temperature. In particular, when hot rolling a slab made of carbon steel, it is necessary to make the rolling temperature in the finish rolling mill higher than the ferrite transformation start temperature (Ar3 temperature) from the viewpoint of securing the material. If the temperature is lower than the Ar3 transformation temperature during rolling, the properties such as strength, ductility, and toughness of the steel strip may deteriorate due to accumulation of coarse grains and strain.

In recent hot finishing rolling, there is a tendency to increase the length in order to improve productivity. For this reason, various measures have been taken to prevent a reduction in the rolling temperature in the longitudinal direction of the steel strip.

[0004] As a typical method, accelerated rolling is known. This is a method in which the rolling speed of a rough bar to be rolled by a finishing mill is not constant, and the rolling speed is increased after the tip of the rough bar enters the finishing mill. It is stated that the time required for the rear end of the rough bar to pass through the finish rolling mill is shortened, so that the temperature can be prevented from lowering to some extent.

On the other hand, JP-A-55-30338 discloses that an induction heating furnace is provided between the exit side of a rough rolling mill and the entrance side of a finishing rolling mill to heat the rear end of a steel strip. A method for preventing a temperature drop in the longitudinal direction is disclosed. here,
A method has been adopted in which an induction heating furnace having a small heating time constant is used, and the temperature is controlled in accordance with the deviation between the finishing temperature delivery side and its target temperature.

[0006]

In accelerated rolling, the rolling speed reaches the upper limit at the trailing end of a long slab, and it cannot be completely solved.

On the other hand, the method disclosed in Japanese Patent Application Laid-Open No. 55-30338 can solve the situation caused by the accelerated rolling to some extent. In order to control the induction heating furnace, the temperature cannot be controlled until the leading end of the rolled material leaves the finishing mill.

[0008] Further, there is a situation that it is extremely difficult to match the finish temperature target value over the entire longitudinal direction because a control delay is large and a control system with good response cannot be made.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hot rolled steel strip having a temperature at which the finishing temperature of the entire steel sheet can be more accurately matched with the finishing temperature target value. It is to provide a control method.

[0010]

In order to achieve the above object, in a first aspect of the method for controlling the temperature of a hot-rolled steel strip according to the present invention, a hot rolling mill for rolling a rough-rolled coarse bar is provided. And, using a heating device installed on the entrance side of the hot rolling mill, and a temperature detector installed on the heating device entrance side, the finishing temperature of the hot rolling mill exit side of the coarse bar, In the method for controlling the temperature of a hot-rolled steel strip, which is controlled so as to match the finishing target temperature on the outlet side of the hot rolling mill, the rough bar on the outlet side of the heating device is obtained from the finishing target temperature on the outlet side of the hot rolling mill. A target temperature value in the longitudinal direction is calculated, and a target temperature increase value of the coarse bar is calculated from the target temperature value and a temperature detected by a temperature detector installed on the inlet side of the heating device. The target field detected by the coarse bar moving distance detection device based on the temperature target value In response to the feed forward controlling the heating device. In this way, the temperature in the longitudinal direction of the coarse bar on the exit side of the heating device is made to match the target temperature value, and the finished plate temperature on the exit side of the hot rolling mill is set to the finished plate target on the exit side of the hot rolling mill. It is characterized in that control is performed so as to match the temperature.

[0011] In a second aspect of the temperature control method for a hot-rolled steel strip according to the present invention, a second temperature detector is installed on the exit side of the hot rolling mill, and the second temperature detector is provided. In feeding back the difference between the detected temperature detected at the target temperature set value in the longitudinal direction of the steel sheet on the exit side of the hot rolling mill to the temperature control, feedback to the heating device and installation in the hot rolling mill And a step of coordinating the feedback to the cooling device.

In a third aspect of the temperature control method for a hot-rolled steel strip according to the present invention, in the step of coordinating feedback to the heating device and feedback to the cooling device, Record the amount of heating of the coarse bar detected by the side, the amount of cooling by the heating device, the amount of cooling by the cooling device, and the temperature detected at the exit side of the hot rolling mill, based on the recorded results. And correcting a target temperature value in the longitudinal direction of the rough bar on the exit side of the heating device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] In order to make the finishing temperature of the entire steel sheet more accurately match the finishing temperature target value, first, an induction heating device is installed on the finishing rolling mill group entrance side. In addition, it is necessary to bring the finishing mill group and the induction heating device as close as possible to reduce the dead time.

For this purpose, in the present invention, a temperature target value on the exit side of the heating device, that is, a temperature target value on the entrance side of the finishing mill group is set, and a temperature detector is installed on the entrance side of the heating device. From the surface temperature of the coarse bar detected by the
The amount of electric power required for heating to the temperature target value on the entrance side of the finishing mill group is calculated, and the calculated amount of electric power is given to the heating device.

At this time, the temperature target value on the entrance side of the finishing rolling mill group is a preset temperature target value in the longitudinal direction of the rough bar on the exit side of the finishing rolling mill group, and the finishing rolling mill for finish rolling the rough bar. From the speed schedule of the group, the thickness schedule between each stand of the finishing rolling mill group, the load setting of each finishing rolling mill, cooling by deskke just before the finishing rolling mill group, the setting of spray cooling in the finishing rolling mill group, etc. It can be calculated based on a temperature change model.

Hereinafter, a method for controlling the temperature of a hot-rolled steel strip according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a basic configuration of a steel sheet rolling apparatus according to a first embodiment of the present invention.

FIG. 1 schematically shows a state in which a slab is roughly rolled by a rough rolling mill, and the roughly rolled rough bar 1 is heated by an induction heating device 2 and subsequently finish rolled by a finish rolling mill 3. Is shown in

As shown in FIG. 1, in the apparatus according to the first embodiment, a temperature detector 4 is installed on the inlet side of the induction heating device 2, and the outlet side of the induction heating device 2, that is, the finishing mill 3 The target temperature of the coarse bar 1 on the entry side is calculated for the entire coarse bar longitudinal direction. An example of a specific calculation method will be described below.

It is known that the temperature change from the entry side to the exit side of the steel sheet of the hot rolling mill can be estimated by solving a heat conduction equation. Here, in the hot rolling, the temperature distribution analysis mainly considers only the thickness direction. At this time, in the longitudinal direction, the length of the coarse bar 1 is several tens of meters, so that the length on the exit side of the finishing rolling mill 3 may exceed several thousand meters, and an appropriate length is determined. The temperature is assumed to be constant. Further, in the width direction, it is basically considered that the processing is affected only by the uniform processing and the phenomenon and is uniform. Therefore, the heat conduction equation of the plate portion divided in the longitudinal direction is given by the following equation.

[0021]

(Equation 1)

Here, T _{s is} the temperature of the rolled material, Cp is the specific heat of the rolled material, ρ is the density of the rolled material, λ is the thermal conductivity of the rolled material, q is the internal heat generation, and t is the time.

The factors of the temperature change in hot rolling include:
As heat removal terms: 1) air cooling (radiative heat transfer, convective heat transfer), 2)
Water cooling (heat transfer by spray cooling), 3) contact heat transfer with the work roll (WR) of the rolling mill, and, as heat input terms, 4) processing heat due to rolling, 5) frictional heat between WR and rolled material Are generally known, of which 1),
2) is given as the boundary condition of equation (1). Also,
4) and 5) can be given as internal heat generation q in the equation (1).

It should be noted that the method 3) needs to be solved simultaneously with the WR heat conduction equation.
An analytical solution based on the Laplace transform is known, and the amount of heat transfer can be calculated as a function of the initial temperature distribution between the rolled material and the WR, the elapsed time, and the position in the thickness direction.

Therefore, what kind of temperature change the rolled material exhibits depends on what boundary conditions and internal heat generation at each time from the entry side to the exit side of the rolling mill 3 in the calculation target portion in the longitudinal direction of the rolled material. Is determined, and equation (1) can be solved by a difference method or the like.

On the other hand, items required to determine the temperature change factors 1) to 5) are as follows.

1) Air cooling: Air cooling time, emissivity.

2) Water cooling: Water cooling time, heat transfer coefficient.

3) Heat removal from contact with WR: contact time with WR.

4) Heat generation during processing: rolling reduction, rolling load, contact arc length.

5) Heat generation by friction: coefficient of friction, rolling load, WR
Speed, rate of advance, rate of reverse, contact time with WR.

In order to determine these, it is necessary to provide a speed schedule of the calculation target portion and a rolling schedule at each stand in advance, but in normal hot rolling, these are set-up calculations as a rolling schedule and a speed schedule. Since the finishing temperature target value on the exit side of the finishing rolling mill is calculated, each condition can be calculated by using these set-up calculated values.

The temperature change model of the steel sheet given as described above is for obtaining the temperature on the exit side of the finishing mill from the temperature on the entrance side of the finishing mill.

In the present invention, it is necessary to determine the target temperature of the outlet of the induction heating device installed on the inlet of the finishing mill from the target temperature of the finishing temperature. Although various calculation methods are conceivable, for example, there is a method in which an appropriate finish rolling mill inlet side temperature is given as an initial condition and a convergence calculation is performed so that the finish outlet side temperature matches a target value.

As described above, the longitudinal direction of the rough bar is divided into a plurality of parts, and the target temperature on the finishing rolling mill entrance side is calculated for each of the divided parts from the finishing temperature target value, whereby the finishing entrance side is calculated. The target temperature distribution in the longitudinal direction of the rough bar is obtained.

Next, the induction heating device 2 and the induction heating device 2
An example of a temperature control system using the temperature detector 4 installed on the input side of the device will be described.

As shown in FIG. 1, the control system includes a temperature detected at the inlet side of the induction heating
The difference from the temperature target value set on the outlet side of i.e., the amount of temperature rise is determined, and the power set value required for heating in the induction heating device 2 is
The calculation may be performed by the power control amount calculation unit 5. At this time, if the temperature target value set on the outlet side of the induction heating device 2 is calculated as a distribution in the longitudinal direction as described above, heating is performed at the longitudinal position indicated by the target value and the heating device. Since location consistency is important, it is necessary to track which portion in the longitudinal direction is at the position of the temperature detector 4. For this reason, after the tip of the rough bar is detected by the temperature detector 4, the transfer distance is sequentially changed to the corresponding temperature target value by counting the transfer distance using, for example, a pulse generator (PG) 6 attached to the transport roll. Just do it.

[Second Embodiment] In order to further improve the temperature control performance of a steel sheet and improve the temperature accuracy of the exit side of the finishing mill group, it is necessary to manage the temperature of the steel sheet on the exit side of the finishing mill group. There is. As the temperature control means in the steel plate rolling device, there is an inter-stand cooling spray for cooling the steel plate, in addition to the induction heating device. In order to control the temperature of the steel sheet, these induction heating devices and stand-to-stand cooling spray
It is important to utilize it effectively for controlling the temperature of steel sheets.

The purpose of the second embodiment is to effectively utilize the temperature control means in the steel sheet rolling apparatus, further improve the temperature control performance of the steel sheet, and improve the temperature accuracy at the exit side of the finishing mill group. And

That is, in the second embodiment, in addition to the feedback to the induction heating device 2, feedback is applied to the inter-stand cooling spray 8 which is another temperature control means of the finishing mill 3. ing. With such a configuration, when the temperature change in the finishing mill 3 differs from the prediction model, the difference can be reflected in the temperature control as quickly as possible, and the temperature accuracy on the outlet side of the finishing mill group is improved. Can be done.

Hereinafter, a method for controlling the temperature of a hot-rolled steel strip according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a view showing a basic configuration of a steel sheet rolling apparatus according to a second embodiment of the present invention. 2, for the sake of simplicity, the same parts as those in FIG. 1 are denoted by the same reference numerals.

Generally, in hot rolling, a feedback control system using a temperature detector 7 arranged on the finishing side and a cooling spray 8 between stands is configured. In most cases, PI control based on the deviation between the finishing target value and the temperature detected by the temperature detector 7 is employed.

On the other hand, the induction heating device 2 is
In the situation where the temperature control means is increased on the inlet side, a mechanism for coordinating induction heating and spray control, that is, a finishing temperature control management mechanism 9 is arranged.

The finishing temperature control management mechanism 9 mainly monitors the heating / cooling operation. Since the heating device 2 is an operation of only heating and the cooling spray 8 is an operation of only cooling, even if the detected temperature on the exit side of the finishing rolling mill is as intended, the heating device 2 may overheat. There is a possibility that energy is wasted by supercooling with the cooling spray 8. By monitoring this consistency at all times, energy consumption can be saved.

[Third Embodiment] The third embodiment is an implementation method of the second embodiment.

FIG. 3 is a view showing a basic configuration of a steel sheet rolling apparatus according to a third embodiment of the present invention. 3, for the sake of simplicity, the same parts as those in FIG. 2 are denoted by the same reference numerals.

One of the causes of the temperature control by the heating device 2 and the cooling spray 8 leading to overheating and supercooling is as follows.
The error between the calculation of the target temperature value in the longitudinal direction of the heating device outlet side coarse bar and the temperature estimation model used in the power control amount calculation in the embodiment. For this reason, the temperature estimation calculation described in the first embodiment, which is performed by dividing the coarse bar in the longitudinal direction, is performed by, for example, recording the detected temperature result, the heating operation result, and the cooling operation result in the model correction unit 10, respectively. ,
For example, the tracking calculation may be saved, and the model calculation error may be corrected based on the track-storing results. As an example of a method of performing this correction, there is a simple method of multiplying an error between the model calculation and the actual result by an adjustment gain to correct the target temperature value in the longitudinal direction of the heating device outlet coarse bar. Further, a method of estimating a parameter of the temperature model (such as a heat transfer coefficient by water cooling) and adjusting the temperature model to an actual result may be used.

According to the above-described structure, not only the error of the feedforward heating by the induction heating can be absorbed but also the energy consumption by the induction heating can be reduced as the finishing temperature control.

[0050]

As described above, according to the present invention, it is possible to provide a method for controlling the temperature of a hot-rolled steel strip, which makes it possible to make the finishing temperature of the entire steel sheet match the finishing temperature target value more accurately.

[Brief description of the drawings]

FIG. 1 is a view showing a basic configuration of a steel sheet rolling apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a basic configuration of a steel plate rolling apparatus according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a basic configuration of a steel plate rolling apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Coarse bar, 2 ... Induction heating device, 3 ... Finishing rolling mill, 4 ... Temperature detector (inlet side of induction heating device), 5 ... Power control amount calculator, 6 ... Pulse generator, 7 ... Temperature detector (finishing) 8: Cooling spray between stands, 9: Finishing temperature control mechanism, 10: Model correction unit.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G05B 13/02 B21B 37/00 BBL (72) Inventor Hiroshi Sekine 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor St. Nakano 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside Nippon Kokan Co., Ltd. (72) Inventor Yoichi Honashiki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun F-term (reference) in this steel pipe Co., Ltd. 4E024 BB07 BB08 BB09 FF10 5H004 GA02 GB03 HA01 HB01 JA01 JA12 JB08 KB32 KD56

Claims (3)

[Claims] 1. A hot rolling mill for rolling a coarsely-rolled coarse bar, a heating device installed on an inlet side of the hot rolling mill,
Using a temperature detector installed on the heating device entrance side,
In the temperature control method of a hot-rolled steel strip, in which the finishing temperature of the hot rolling mill exit side of the rough bar is controlled to match the finishing target temperature of the hot rolling mill exit side, the hot rolling mill exit side From the finishing target temperature, a temperature target value in the longitudinal direction of the coarse bar on the heating device output side is calculated.From the temperature target value, and a detected temperature detected by a temperature detector installed on the heating device input side. Calculating a target temperature increase value of the coarse bar, and performing feedforward control on the heating device according to a target position detected by the coarse bar moving distance detection device based on the target temperature increase value, The temperature in the longitudinal direction of the rough bar on the output side of the apparatus is controlled to match the target temperature value, and the finished plate temperature on the output side of the hot rolling mill is controlled to match the finished plate target temperature on the output side of the hot rolling mill. Temperature control of hot-rolled steel strip Method. 2. A second temperature detector is provided on the outlet side of the hot rolling mill, and a detected temperature detected by the second temperature detector and a longitudinal direction of the steel sheet on the outlet side of the hot rolling mill are provided. When feeding back a deviation from a target temperature set value to temperature control, the method has a step of coordinating feedback to the heating device and feedback to a cooling device installed in the hot rolling mill. Item 2. The method for controlling temperature of a hot-rolled steel strip according to item 1. 3. The step of coordinating the feedback to the heating device and the feedback to the cooling device, wherein the amount of heating of the coarse bar, the temperature of which has been detected on the heating device entrance side, by the heating device; The actual amount of the cooling amount and the temperature detected at the exit side of the hot rolling mill are recorded, and the target temperature value in the longitudinal direction of the rough bar on the exit side of the heating device is corrected based on the recorded actual results. The method for controlling the temperature of a hot-rolled steel strip according to claim 2, wherein: