JPH11108773A - Metal plate temperature measuring equipment and rolling method for heat rolled steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately control rolling finish temperature by calculating the plate thickness average temperature of a metal plate from the surface temperature of the metal plate heated to a specified temperature, a plate thickness and a detected value of a heat quantity lost from the unit area of the metal plate surface per unit time based on a specified expression. SOLUTION: Among the plate thickness average temperature TM of a metal plate heated to a high temperature, the surface temperature TS of the metal plate, a physical value and a heat quantity Q lost from the unit area of the metal plate surface per unit time, a thermal conduction relational expression indicated by the expression of TM=TS+(H×Q)/(α×λ) (Ts; metal plate surface temperature, H: plate thickness of the metal plate, Q: heat quantity lost from the unit area of the metal plate surface per unit time, α: constant, λ: metal plate thermal conductivity, TM: rough bar plate thickness average temperature) is established. For highly accurately controlling the temperature of rolling finish, a plate thickness average temperature is set based on the thermal conduction relational expression, and by deciding a heat quantity supplied to a rough bar 2 based on the set plate thickness average temperature, the temperature of rolling finish is effectively controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the temperature of a high-temperature metal sheet and a method for rolling a hot-rolled steel strip using the apparatus.

[0002]

2. Description of the Related Art The quality of a metal material product such as a hot-rolled steel strip is closely related to the heat history during production, and temperature control in the production process is extremely important. In the case of a hot-rolled steel strip, the rolling finish temperature after finish rolling is closely related to the material of the hot-rolled steel strip, and control of the rolling finish temperature is important. In order to use it as an index for temperature management, the temperature of a metal material is measured. Usually, the temperature of the surface of the metal material is measured using a radiation thermometer or the like.

[0003] In order to provide the necessary thermal history to the metal material,
A step of heating the metal material is often incorporated.
In the heating step, heating control must be performed accurately in order to apply a predetermined temperature to the metal material. Japanese Unexamined Patent Application Publication No. 2-8318 proposed for such a request discloses that the temperature after heating is determined based on the temperature of the material to be heated measured by a thermometer provided on the inlet side of the induction heating device. This is a technique for controlling the output of an induction heating device so as to reach a target temperature.

[0004]

However, the technique disclosed in Japanese Patent Laid-Open No. 2-8318 has the following problems. A slab heated to a predetermined temperature is roughly rolled to form a rough bar, and the rough bar is finish-rolled by a finishing mill to produce a hot-rolled steel strip. Install a heating device between the rolling mills, based on the rough bar surface temperature measured on the heating device entrance side, so that the rolling finish temperature measured by the finish rolling mill exit thermometer will be the target temperature, When the coarse bar is heated by performing the heating control, the rolling finish temperature becomes higher than the target temperature.

The reason lies in the difference between the average temperature of the thickness of the metal plate and the surface temperature. The temperature distribution in the plate thickness direction of a high-temperature metal plate in a steady state is highest at the center of the plate thickness, and lowers closer to the surface. The greater the thickness of the metal plate, the greater the difference between the average thickness temperature and the surface temperature. FIG. 2 shows changes in the surface temperature, the sheet thickness center temperature, and the sheet thickness average temperature of the material to be rolled before and after finish rolling (Source: Sheet Rolling Theory and Practice (The Iron and Steel Institute of Japan, 1984, p. 158)). The difference between the average sheet thickness and surface temperature of the rough bar before descaling is about 50 ° C., but in the hot-rolled steel strip after finish rolling, the average sheet thickness and surface temperature are almost equal. As in the prior art, a method of controlling the surface temperature of a hot-rolled steel strip by calculating the amount of heat supplied to the coarse bar based on the surface temperature of the coarse bar on the inlet side of the heating device, the average thickness of the coarse bar An extra amount of heat is added by the difference between the temperature and the surface temperature, and the rolling finish temperature becomes higher than the target temperature. In order to avoid this, it is necessary to determine the heating amount based on the average temperature of the plate thickness, not the surface temperature of the rough bar.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for measuring the average thickness of a high-temperature metal sheet and to control the rolling finish temperature with high accuracy based on the average thickness. An object of the present invention is to provide a method for rolling a steel strip.

[0007]

In order to solve the above problems and achieve the object, the present invention uses the following means. (1) A temperature measuring device according to the present invention includes a surface temperature detecting unit for a metal plate heated to a predetermined temperature, a plate thickness detecting unit for a metal plate, and a heat amount lost from a unit area of the metal plate surface per unit time. Means for calculating the average thickness of the metal plate based on the following equation (1) from the values detected by the detection means: temperature measurement of the metal plate. Device.

T _M = T _S + (H × Q) / (α × λ) (1) T _M : Average thickness of metal plate, T _S : Surface temperature of metal plate, H: Metal plate Thickness, Q: amount of heat lost from the unit area of the metal plate surface per unit time, α: constant, λ: thermal conductivity of the metal plate (2) The temperature measuring device of the present invention converts the heat amount Q into the following (2) The temperature measuring device for a metal plate according to the above (1), which is given by an equation.

[0009] Q = ε × σ × (T S 4 -T R 4) + h × (T S -T R) ... (2) ε: emissivity, σ: Stefan-Boltzmann constant, h:
Heat transfer coefficient between metal plate and air, T _R : room temperature (3) In the rolling method of the present invention, the metal slab is roughly rolled into a rough bar, the rough bar is heated by a heating device, and then finish-rolled. In the rolling method for producing a hot-rolled steel strip, the average temperature of the coarse bar thickness is determined based on the following equation (1) based on the coarse bar surface temperature measured by the temperature detecting means of the coarse bar installed on the inlet side of the heating device. A method for rolling a hot-rolled steel strip, comprising setting and controlling an output of a heating device based on an average temperature of the sheet thickness so that a finishing temperature of the rolling becomes a target temperature.

T _M = T _S + (H × Q) / (α × λ) (1) T _M : Average thickness of metal plate, T _S : Surface temperature of metal plate, H: Metal plate Thickness, Q: amount of heat lost from the unit area of the metal plate surface per unit time, α: constant, λ: thermal conductivity of the metal plate (4) In the rolling method of the present invention, the heat amount Q is calculated by the following (2)
The method for rolling a hot-rolled steel strip according to the above (3), which is given by an equation.

[0011] Q = ε × σ × (T S 4 -T R 4) + h × (T S -T R) ... (2) ε: emissivity, σ: Stefan-Boltzmann constant, h:
Heat transfer coefficient between metal plate and air, T _R : room temperature (5) The rolling method of the present invention is characterized in that the heating device for heating the coarse bar is a solenoid-type induction heating device. A method for rolling a hot-rolled steel strip according to 3) or 4).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have developed an apparatus for measuring the average thickness of a high-temperature metal sheet, and enable accurate control of the rolling finish temperature based on the average thickness of the sheet. In order to obtain a method for rolling a hot-rolled steel strip, the present inventors have conducted intensive studies and obtained the following findings. The present inventors, between the thickness average temperature T _M of the metal plate heated to a high temperature, the surface temperature of the metal plate, physical properties, and the amount of heat lost from the unit area of the metal plate surface per unit time, It has been found that the heat conduction relational expression shown in the following expression (1) holds. T _M = T _S + (H × Q) / (α × λ) (1) T _M : Average thickness of metal plate, T _S : Surface temperature of metal plate, H: Thickness of metal plate, Q : The amount of heat lost from the unit area of the metal plate surface per unit time, α: constant, λ: thermal conductivity of the metal plate The plate thickness average temperature T _M of the coarse bar is set by this equation (1).

The heat quantity Q lost from the unit area of the rough bar surface per unit time is calculated by the following equation (2). Q = ε × σ × (T S 4 -T R 4) + h × (T S -T R) ... (2) ε: emissivity, sigma: Stefan-Boltzmann constant, h:
It is known that the heat transfer coefficient between the metal plate and the air, T _R : room temperature, The amount of heat Q lost by radiation from the unit area of the rough bar surface per unit time is given by the following equation (3).

[0014] Q = ε × σ × (T S 4 -T R 4) ... (3) ε: emissivity, σ: Stefan-Boltzmann constant, T
_S : Coarse bar surface temperature, T _R : Room temperature Equation (2) is an equation obtained by further increasing the accuracy in consideration of the amount of heat lost due to heat transfer between the metal plate and air in addition to the known equation (3). is there.

In order to enable accurate control of the rolling finishing temperature, the present inventors described the above (1),
It has been found that it is effective to control the rolling finishing temperature by setting the average thickness of the sheet based on the equation (2) and determining the amount of heat to be supplied to the coarse bar based on the average temperature of the thickness. It was.

Based on the above findings, the present inventors determined the average thickness of the coarse bar heated to a high temperature by measuring the surface temperature of the coarse bar measured at the entrance of the heating device, the physical property value, and the unit time. It is set from a device that calculates using a heat conduction relational expression based on the amount of heat lost from the unit area of the bar surface, and based on the average thickness of the plate, the output of the solenoid type induction heating device is set so that the rolling finish temperature reaches the target temperature. A device for controlling the thickness average temperature of a metal plate heated to a high temperature, and a hot-rolled steel strip capable of accurately controlling a rolling finish temperature based on the average thickness temperature. Of the present invention, and completed the present invention.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic side view showing a row of hot rolling equipment for carrying out the present invention. The slab at a predetermined temperature is roughly rolled by the rough rolling mill 1 to become a rough bar 2, sent to a finish rolling mill 10 on a transfer table (not shown), and finish rolled to be a hot rolled steel strip. On the way, the rough bar 2 is heated by the solenoid-type induction heating device 9, and is heated to a temperature required for the finishing temperature of the rolling measured by the finishing thermometer 11 to reach the target temperature.

The pulse generator 3 generates a pulse each time the transport roll 4 rotates by a predetermined angle. By measuring the number of generated pulses after the coarse bar tip detection sensor 5 detects the tip of the coarse bar 2, it is possible to know where the coarse bar 2 is.

A heating device inlet thermometer 7 (means for detecting the surface temperature of the rough bar 2) measures the surface temperature of the rough bar 2. In the present invention, the rough bar 2 is obtained by the following equation (1) based on the surface temperature.
The average temperature of the sheet thickness.

T _M = T _S + (H × Q) / (α × λ) (1) T _M : Average thickness of coarse bar, T _S : Surface temperature of coarse bar, H: Plate of coarse bar Thickness, Q: heat loss from the unit area of the coarse bar surface per unit time, α: constant, λ: thermal conductivity of the coarse bar. Equation (1) is, as described above, the state of the temperature distribution in the thickness direction of a high-temperature metal plate in the steady state (the highest temperature at the center of the thickness, and the lower the closer to the surface, the lower the average thickness and surface temperature). The difference is proportional to the thickness of the metal plate.).

That is, the equation (1) is based on the average thickness of the sheet in consideration of the surface temperature of the high-temperature metal sheet (coarse bar) in the steady state and the amount of heat transferred from the metal sheet surface to the inside of the sheet while further cooling by radiation. The temperature is set. The average thickness T _M of the metal plate, the surface temperature of the metal plate, physical properties (thickness of the metal plate, thermal conductivity), and the unit area of the metal plate surface in unit time The heat conduction relational expression shown in the above expression (1) holds between the amount of heat lost.

If the steady state is reached thermally, the heat conduction equation [ρ · Cp (∂T / ∂t) = λ · (∂ ² T /
∂x ² )] (where ρ: density of coarse bar, Cp: specific heat of coarse bar, T: thermal diffusion time), and a time-dependent term (here, the left side) can be approximated to zero, The heat conduction equation is a second-order differential equation relating to the position x (here, the position of the coarse bar in the thickness direction). The solution is a quadratic function of x. On the rough bar surface, the integral constant is determined from the boundary condition that the heat flow rate (the amount of heat lost from the unit area of the rough bar surface per unit time) becomes Q, and the condition that the solution becomes symmetrical with respect to the thickness center of the rough bar. You can decide. If this solution is obtained, equation (1) can be easily derived.

The amount of heat Q lost from the unit area of the rough bar surface per unit time is calculated by the following equation (2). Q = ε × σ × (T S 4 -T R 4) + h × (T S -T R) ... (2) ε: emissivity, sigma: Stefan-Boltzmann constant, h:
The heat transfer coefficient between the rough bar and air, T _R: room temperature.

The equation (2) is, as described above, the heat quantity Q radiated from the unit area of the rough bar surface per unit time given by the following equation (3), and the heat quantity Q between the metal plate and the air. The accuracy is improved in consideration of the amount of heat (h × (T _S −T _R )) lost due to the heat transfer.

[0025] Q = ε × σ × (T S 4 -T R 4) ... (3) ε: emissivity, σ: Stefan-Boltzmann constant, T
_S : Rough bar surface temperature, T _R : Room temperature Equations (1) and (2) show that the temperature distribution in the thickness direction of the rough bar 2 is a recuperation process immediately after the surface of the rough bar 2 is water-cooled by descaling or the like. It cannot be used when it is in an unsteady state, such as The thickness average temperature can be set only when the temperature distribution in the thickness direction of the rough bar 2 has reached the steady state. Coarse bar 2 when cooled in air
, The emissivity ε is 0.6 to 0.7. The heat transfer coefficient h is 20-30, but there is almost no difference even when h = 0. The constant α can be set with high accuracy by taking a value around 6.

As an apparatus for setting the average temperature of the thickness of the rough bar 2, the above-described heating device inlet thermometer 7 (rough bar 2) is used.
Surface temperature detecting means), plate thickness detecting means of the coarse bar 2,
Means for detecting the amount of heat lost from the unit area of the surface of the rough bar 2 per unit time, and means for calculating the average temperature of the thickness of the rough bar 2 based on the expression (1) from the detection values from these detecting means (for example, , A computer that performs calculations based on a preset program). The thickness detecting means and the calorific value detecting means are not particularly limited, and include, for example, a method of actually measuring using a sensor and a method of calculating and setting as shown below (generally, "calculating and setting Method "is used.).

A. Thickness detecting means 1) Gamma ray thickness gauge Gamma rays are irradiated from above the coarse bar, the intensity of the transmitted gamma ray is measured by a gamma ray detector installed below the coarse bar, and the transmittance of the gamma ray and the plate determined in advance are determined. The thickness of the coarse bar is determined based on the thickness relationship.

2) Setting Based on Rolling Theory The thickness of the coarse bar is set from the roll gap and rolling load at the final stage of the rough rolling mill. b. Calorimetric detection means 1) Schmitt belt A plate with a constant thickness made of a substance with a constant thermal conductivity is brought into close contact with a rough bar, and the temperature difference between the two surfaces is measured with a thermocouple or the like to measure the heat flow rate (mechanical engineering Publicly known means introduced in the handbook).

2) Setting method using equation (2) From the surface temperature of the rough bar, the heat flux Q is set based on equation (2) as described above. As for the emissivity ε and the heat transfer coefficient h, values experimentally obtained are already known (as described above, ε: 0.6 to 0.7, h: 20 to 3).
0).

Based on the operating conditions such as the position of the coarse bar 2 thus obtained, the average temperature of the coarse bar 2 at the entrance side of the solenoid type induction heating device 9 and the rolling pass schedule, the control device 6 Calculates the amount of heating required to make the rolling finish temperature the target temperature, and controls the electric power supplied from the high frequency power supply 8 to the solenoid type induction heating device 9. As the heating device, it is desirable to use a solenoid type induction heating device 9 in consideration of heating efficiency and control response. Hereinafter, examples of the present invention will be described to demonstrate the effects of the present invention.

[0031]

EXAMPLE Heated to 1250 ° C. in a heating furnace, thickness 23
0 mm, a width of 1300 mm, a length of 9000 mm steel slab, using a row of hot rolling equipment as shown in FIG. 1, rough rolling mill 1 to form a coarse bar 2 of 35 mm thick,
Further, the rough bar 2 was finish-rolled by the finish rolling mill 10 to produce a hot-rolled steel strip having a thickness of 2.8 mm and a width of 1300 mm. In addition, the hot rolling equipment train which performed this Example is the 5000 k which heats the rough bar 2 between the rough rolling mill 1 and the finishing rolling mill 10.
It is provided with six W-class solenoid induction heating devices 9.

FIG. 3 shows the change in the finishing temperature of the rolling measured by the exit thermometer 11 on the finishing mill. A graph (comparative example) represented by a mark indicates the rolling finishing temperature when the coarse bar 2 was not heated by the solenoid-type induction heating device 9. The graph with a circle (prior art) shows the heating of the solenoid-type induction heating device 9 based on the surface temperature of the rough bar 2 measured by the heating device inlet thermometer 7 so that the rolling finish temperature becomes 890 ° C. This is the rolling finish temperature when control is performed. It is 15 ° C. or more higher than the target temperature of 890 ° C.

On the other hand, based on the surface temperature of the rough bar 2 measured by the thermometer 7 on the inlet side of the heating device, the above-mentioned (1) was set at α = 6.
Based on the average sheet thickness temperature of the rough bar 2 estimated by the equation, the rolling finish temperature when the input power of the solenoid type induction heating device 9 is determined so that the rolling finish temperature becomes 890 ° C. is shown by a black circle. (Example of the present invention). A rolling finish temperature almost equal to the target temperature of 890 ° C. is obtained. In the present embodiment, the surface temperature of the coarse bar 2 measured by the heating device inlet thermometer 7 and the average thickness of the sheet estimated by the present invention are 30 to 3 times.
There is a 5 ° C difference. Due to this temperature difference, a difference in the rolling finish temperature shown in FIG. 3 is generated.

FIG. 4 is a diagram showing a change in the electric power supplied to one solenoid type induction heating device 9.
In the present embodiment, the power supplied to the six solenoid induction heating devices 9 is controlled so as to be the same at a certain position of the coarse bar 2. For example, regarding the input power of the present invention in FIG. 4, when the tip of the coarse bar 2 passes through the six solenoid-type induction heating devices 9, the input power of any of the solenoid-type induction heating devices 9 is about 4000 kW. ing. As can be seen from FIG. 4, in the prior art, extra power is supplied compared to the present invention, and the energy consumption is deteriorated. From FIGS. 3 and 4, it can be seen that the target rolling finish temperature is obtained with the minimum input power required by the present invention.

[0035]

According to the present invention, the average thickness of the metal plate can be determined from the surface temperature of the high-temperature metal plate. Further, in a method of roughly rolling a metal slab to form a rough bar, heating the rough bar with a heating device, and finish rolling to produce a hot-rolled steel strip, the surface temperature of the rough bar measured at the heating device entrance side. From, by setting the thickness average temperature of the coarse bar by the method of the present invention, based on the thickness average temperature, so that the rolling finish temperature is the target temperature, by determining the input power to the heating device, Accurate control of the rolling finishing temperature is possible.

As a result, the rolling finishing temperature can be controlled with the minimum required amount of heating, and an increase in energy consumption can be prevented. Further, the material of the hot-rolled steel strip is improved and uniformized, and the yield is increased.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a configuration of each device of a hot rolling equipment row according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change in temperature of a material to be rolled before and after finish rolling.

FIG. 3 is a diagram showing a change in a rolling finishing temperature according to the embodiment of the present invention.

FIG. 4 is a diagram showing a change in electric power supplied to the induction heating device according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Coarse rolling mill, 2 ... Coarse bar, 3 ... Pulse oscillator, 4 ... Conveying roll, 5 ... Coarse bar tip detection sensor, 6 ... Control device, 7 ... Heating device inlet side thermometer (metal plate surface temperature detecting means ), 8: High frequency power supply device, 9: Solenoid induction heating device, 10: Finishing rolling mill, 11: Finishing mill output thermometer.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masaaki Yamamoto 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (5)

[Claims] 1. A metal plate surface temperature detecting means heated to a predetermined temperature, a metal plate thickness detecting means, a heat amount detecting means lost from a unit area of the metal plate surface per unit time, and these detecting means A means for calculating the average thickness of the metal plate from the detected value from the following formula (1), based on the following equation (1): T _M = T _S + (H × Q) / (α × λ) (1) T _M : Average thickness of metal plate, T _S : Surface temperature of metal plate, H: Thickness of metal plate, Q : The amount of heat lost from the unit area of the metal plate surface per unit time, α: constant, λ: thermal conductivity of the metal plate 2. The apparatus according to claim 1, wherein the heat quantity Q is given by the following equation (2). Q = ε × σ × (T S 4 -T R 4) + h × (T S -T R) ... (2) ε: emissivity, sigma: Stefan-Boltzmann constant, h:
Heat transfer coefficient between metal plate and air, T _R : room temperature 3. The metal slab is rough-rolled into a rough bar,
In a rolling method in which a rough bar is heated by a heating device and finish-rolled to produce a hot-rolled steel strip, the following (1) is obtained from the rough bar surface temperature measured by the temperature detecting means of the rough bar installed on the inlet side of the heating device. )) Setting the average thickness of the coarse bar based on the formula, and controlling the output of the heating device based on the average thickness to control the output of the heating device so that the finishing temperature of the rolling becomes the target temperature. Rolling method of rolled steel strip. T _M = T _S + (H × Q) / (α × λ) (1) T _M : Average thickness of metal plate, T _S : Surface temperature of metal plate, H: Thickness of metal plate, Q : The amount of heat lost from the unit area of the metal plate surface per unit time, α: constant, λ: thermal conductivity of the metal plate 4. The method for rolling a hot-rolled steel strip according to claim 3, wherein the heat quantity Q is given by the following equation (2). Q = ε × σ × (T S 4 -T R 4) + h × (T S -T R) ... (2) ε: emissivity, sigma: Stefan-Boltzmann constant, h:
Heat transfer coefficient between metal plate and air, T _R : room temperature 5. The method for rolling a hot-rolled steel strip according to claim 3, wherein the heating device for heating the coarse bar is a solenoid-type induction heating device.