JP2002294350A - Plate temperature control method for floater type continuous annealing furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably set the temperature of a succeeding plate at the furnace outlet to be within the tolerance of the target plate temperature even when the temperature of a floater type continuous annealing furnace does not reach the set value. SOLUTION: When a connection part of a preceding plate to a succeeding plate passes through a furnace inlet, a furnace temperature, a nozzle pressure and the line speed of the succeeding plate obtained from a plate temperature control model formula with the plate temperature, the furnace temperature inlet as parameters are reset. Until the furnace temperature reaches the furnace inlet as parameters are reset. Until the furnace temperature reaches the set value of the furnace temperature, the first furnace outlet plate temperature of the succeeding plate is obtained by substituting the measured furnace temperature, the measured nozzle pressure and the set line speed in the model formula, the second furnace outlet plate temperature is obtained by substituting the measured furnace temperature, the measured nozzle pressure, and the temporarily determined temporary line speed in the model formula, the line speed of the succeeding plate for achieving the target plate temperature of the succeeding plate is obtained from the first furnace outlet plate temperature and the second furnace outlet plate temperature, the line speed and the temporary line speed, and the temperature is controlled so as to achieve the obtained line speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a sheet temperature of a floater type continuous annealing furnace in which a material to be processed in which a preceding sheet and a succeeding sheet having different target processing conditions are connected is continuously passed through a furnace for annealing. It belongs to the technical field.

[0002]

2. Description of the Related Art As is well known, there is a method in which a preceding plate and a succeeding plate of metal having different target processing conditions are connected, and the connected workpieces are continuously fed into a continuous heat treatment furnace for heat treatment. In this case, in order to set processing conditions most suitable for each of the preceding plate and the succeeding plate, a passing speed (hereinafter, referred to as a line speed) and a furnace temperature are set at a connection portion between the preceding plate and the following plate. Are controlled so that the sheet temperature at the furnace outlet of the continuous heat treatment furnace for the preceding plate and the succeeding plate is in the target temperature range. As a method of controlling the sheet temperature of such a continuous heat treatment furnace,
For example, one disclosed in Japanese Patent Application Laid-Open No. 10-324924 is known. Hereinafter, the method of controlling the sheet temperature of the continuous heat treatment furnace according to the conventional example will be described with reference to FIG. This will be described.

[0003] In the conventional method of controlling the sheet temperature of a continuous heat treatment furnace, the line speed is changed according to the furnace temperature without stopping the line and without using a dummy material. S2 is a sheet temperature control method for performing heat treatment under target processing conditions, wherein the material temperature of the preceding material S1 is maintained constant while changing the furnace temperature so as to approach the furnace temperature for processing the succeeding material S2. Is determined, a line speed LSX suitable for the heating time HX is determined, and the line speed is controlled so as to be equal to the line speed LSX. After the furnace temperature reaches the furnace temperature of the succeeding material S2, the connection S3 between the preceding material S1 and the succeeding material S2 is connected to the continuous heat treatment furnace 1.
3, a heating time H2 for maintaining the material reaching temperature of the succeeding material S2 at a constant level is determined, a line speed LS2 suitable for the heating time H2 is determined, and the line speed LS2 is adjusted to the line speed LS2. This is a sheet temperature control method for controlling the speed.

In the conventional method for controlling the sheet temperature of a continuous heat treatment furnace, the specific heat of the preceding material S1 and the succeeding material S2 in consideration of the specific gravity of the preceding material S1 and the succeeding material S2, Sheet width of S1 and succeeding material S2, sheet thickness of material, heat transfer coefficient of preceding material S1 and succeeding material S2, changing furnace temperature, preceding material S
The heating times HX and H2 are obtained using a function including the temperatures at the entrance of the material 1 and the succeeding material S2 and the temperatures reached by the preceding material S1 and the following material S2, and the length of the continuous processing furnace is determined by the obtained heating time HX ,
By dividing by H2, the line speeds LSX and LS2 of the preceding material S1 and the following material S2 are determined.

Next, the method of controlling the sheet temperature of the continuous heat treatment furnace will be described in detail. The furnace temperature for the succeeding material S2 (after the furnace temperature for the preceding material S1 (preceding material furnace temperature)) will be described. Furnace temperature)
If the furnace temperature is low, the furnace speed is reduced from the preceding material furnace temperature to the succeeding material furnace temperature, and the line speed is reduced so that the material reaching temperature of the preceding material S1 does not change. After doing
At the timing when the connecting portion S3 passes through the furnace, the line speed is controlled to be changed to the line speed of the succeeding material S2.
Conversely, if the subsequent material furnace temperature is higher than the preceding material furnace temperature, the furnace temperature is raised from the preceding material furnace temperature to the following material furnace temperature while the preceding material S1 is increased.
The line speed is accelerated so that the material reaching temperature does not change, and after the furnace temperature reaches the following material furnace temperature, the line speed is changed to the line speed of the following material S2 at the timing when the connection S3 passes through the furnace. Is controlled to be changed to

[0006]

SUMMARY OF THE INVENTION The above-mentioned conventional sheet temperature control method for a continuous heat treatment furnace is characterized in that the sheet temperature at the furnace outlet at the exit of the continuous heat treatment furnace of the preceding plate or the succeeding plate is set to a target sheet temperature within an allowable range. It is considered to be extremely useful. However, in the method for controlling the sheet temperature of the continuous heat treatment furnace, as described above, after the furnace temperature reaches the furnace temperature of the following material, the heating time for maintaining the material arrival temperature of the following material constant is determined. A line speed suitable for the heating time is obtained, and the line speed is controlled so as to be the line speed to control the plate temperature. It is assumed that the furnace temperature reaches a set value.

However, in the actual operation of the floater type continuous annealing furnace, the furnace temperature does not reach the set value due to equipment problems, that is, a decrease in combustion efficiency due to burner clogging or an air ratio defect. Alternatively, the heating time may be too long. Therefore, the sheet temperature control method of the continuous heat treatment furnace according to the conventional example on the premise that the furnace temperature reaches the set value cannot be directly applied to the sheet temperature control method of the floater type continuous annealing furnace.

Accordingly, an object of the present invention is to ensure that the furnace outlet plate temperature at the furnace outlet of the material to be processed is set to a target plate temperature within an allowable range even if the furnace temperature does not reach the set value. It is an object of the present invention to provide a method of controlling a sheet temperature of a floater type continuous annealing furnace which is made possible.

[0009]

The parameters of the sheet temperature control for obtaining the furnace exit sheet temperature at the furnace exit of the floater type continuous annealing furnace are the sheet thickness (known) of the material to be treated, the furnace temperature, and the nozzle. Pressure, line speed, furnace inlet plate temperature (known) 5
Since four items are known, the remaining one item can be obtained by calculation. Accordingly, the present inventors can determine the line speed at which the furnace exit plate temperature of the succeeding plate can be set to the target plate temperature by constantly measuring the furnace temperature, nozzle pressure, and line speed of the succeeding plate. If the line speed is controlled to the line speed, even if the furnace temperature does not reach the set value, ensure that the furnace exit plate temperature at the furnace exit of the succeeding plate is within the allowable range of the target plate temperature. The present invention has been made in view of the fact that it becomes possible.

In order to solve the above-mentioned problem, the means adopted by the method for controlling the sheet temperature of the floater type continuous annealing furnace according to the first aspect of the present invention connects the preceding sheet and the succeeding sheet having different target processing conditions. Then, in a sheet temperature control method of a floater type continuous annealing furnace in which the material to be processed, which connects the preceding plate and the succeeding plate, is passed through a furnace to anneal, the leading and trailing plates of the material to be treated are In the process where the connection passes through the furnace inlet, set the furnace temperature, nozzle pressure, and line speed obtained from the plate temperature control model formula using the plate temperature, furnace temperature, nozzle pressure, line speed, and furnace inlet plate temperature as parameters. Until the furnace temperature falls to the set value, the measured furnace temperature measured by the furnace temperature detector, the measured nozzle pressure measured by the nozzle pressure detector, and the line speed are calculated by the model formula. Then, determine the first furnace exit sheet temperature at the furnace exit of the succeeding plate, The measured furnace temperature measured by the furnace temperature detector, the measured nozzle pressure measured by the nozzle pressure detector, and the tentatively determined tentative line speed were applied to the model formula to obtain the second at the furnace outlet of the succeeding plate. A succeeding plate capable of achieving a target plate temperature of a succeeding plate at a furnace outlet from the first furnace exit plate temperature and the second furnace exit plate temperature and the line speed and the provisional line speed while obtaining the furnace exit plate temperature. And the control of the line speed is repeated so as to achieve the obtained line speed.

According to a second aspect of the present invention, there is provided a floater type continuous annealing furnace according to the first aspect of the present invention, wherein the floater type continuous annealing furnace has a sheet temperature control method. When obtaining the line speed capable of achieving the target plate temperature, the first furnace outlet plate temperature and the line speed, and the second furnace outlet plate temperature and the provisional line are determined based on the relationship between the furnace outlet plate temperature and the line speed. It is characterized by using an equation of a line segment passing through two points obtained from the speed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a floater type continuous annealing furnace according to an embodiment for carrying out a sheet temperature control method for a floater type continuous annealing furnace according to the present invention, a floater type continuous annealing furnace, and a configuration of a control system thereof will be described. This will be described with reference to FIG. 1 of the explanatory diagram, FIG. 2 of the control flow explanatory diagram of the floater type continuous annealing furnace, and FIG. 3 of the explanatory diagram of the relationship between the furnace outlet temperature of the workpiece and the line speed.

First, a floater type continuous annealing furnace will be described with reference to FIG. 1. Reference numeral 1 shown in the figure denotes a material 2 to be processed consisting of a preceding plate and a succeeding plate connected by a plate connecting device (not shown). Is a floater type continuous annealing furnace (hereinafter, referred to as a continuous annealing furnace). Inside the continuous annealing furnace 1, a furnace temperature detector 3 for measuring the furnace temperature is provided at a furnace inlet 1a side, and hot air blown to a plate by a circulating fan described later is blown at a furnace outlet 1b side, not shown. A nozzle pressure detector 4 for measuring the nozzle pressure of the hot air jet nozzle is provided.

The furnace temperature of the continuous annealing furnace 1 is determined by a furnace temperature controller 6 which takes in the measured furnace temperature fed back from the furnace temperature detector 3, and the nozzle pressure is measured by the measured nozzle pressure fed back from the nozzle pressure detector 4. Is configured to be controlled by the nozzle pressure adjuster 7 that takes in the pressure. Also,
At a position outside the furnace outlet 1b of the continuous annealing furnace 1, a line speed detector 5 for measuring a passing speed of the workpiece 2 is provided, and the line speed is fed back from the line speed detector 5. It is configured to be controlled by a line speed adjuster 8 that takes in the measured line speed.

Although not shown, an upper circulation fan and a lower circulation fan are provided in the continuous annealing furnace 1 at predetermined intervals in the vertical direction. Hot air whose temperature has been adjusted is blown toward the upper surface and the lower surface of the workpiece 2 passed between the lower circulation fan.

The setting of the furnace temperature of the furnace temperature controller 6 and the setting of the nozzle pressure of the nozzle pressure controller 7 are both fed back from the actual furnace temperature and the nozzle pressure detector 4 fed back from the furnace temperature detector 3. The set value calculation device 9 takes in the actually measured nozzle pressure. Further, the set value calculation device 9 calculates not only the furnace temperature setting and the nozzle pressure setting but also the measured furnace temperature fed back from the furnace temperature detector 3 and the measured nozzle pressure fed back from the nozzle pressure detector 4. Applying to a plate temperature control model formula to be described later using the plate thickness of the succeeding plate, the plate temperature of the furnace inlet, the furnace temperature, the nozzle pressure, and the line speed as parameters, the furnace at the furnace outlet 1b of the succeeding plate In addition to calculating the outlet plate temperature, the line speed controller 8 functions to issue a command signal so that the line speed is controlled to a line speed capable of achieving the determined furnace outlet plate temperature.

The setting change of the sheet temperature control method of the continuous annealing furnace 1 having the above-described configuration will be described below. 1a, the set value calculating device 9 sets a set value for setting the furnace outlet plate temperature T _out of the succeeding plate to the target plate temperature T _M , that is, a set value for the furnace temperature T _F , the nozzle pressure P, and the line. Each of the speeds L _S is set in the furnace temperature controller 6, the nozzle pressure controller 7, and the line speed controller 8. The set values of the furnace temperature T _F , the nozzle pressure P, and the line speed L _S set in the furnace temperature controller 6, the nozzle pressure controller 7, and the line speed controller 8 are determined in advance by the following plate temperature control model formula. Apply and ask for it. Unless there is a limit on the line speed L _S among the set values, the line speed L _S is set to be the maximum and applied. T _out = f (G _A , T _in , T _F , P, L _S ) ‥‥‥‥‥‥‥‥‥‥‥ (1) T _M = T _out ‥‥‥‥‥‥‥‥‥‥‥‥ ‥‥‥‥‥‥‥‥‥‥‥‥‥ (2) where, G _a is the thickness of the trailing plate in the plate temperature control model equation, T _in is a furnace inlet plate temperature of the trailing plate Therefore, these values are all known.

Hereinafter, a method of controlling the sheet temperature of the continuous annealing furnace 1 of the present invention after the furnace temperature is changed will be described with reference to the control flow diagram of the continuous annealing furnace according to the present embodiment shown in FIG. As described above, it takes a considerable time for the furnace temperature of the continuous annealing furnace 1 to settle to the set value, and the furnace temperature and the nozzle pressure cannot be fully adjusted to the set values. May not be reached. Therefore, first, in step 1, the measured furnace temperature T fed back from the furnace temperature detector 3 by the set value calculating device 9.
The _F1, also takes in the measured nozzle pressure P ₁ fed back from the nozzle pressure detector 4, respectively, the process proceeds to step 2.

In step 2, the measured furnace temperature T _F1 fetched from the furnace temperature detector 3, the measured nozzle pressure P ₁ fetched from the nozzle pressure detector 4, and the line speed L _S set to be the maximum are set in the above plate. Applying to the temperature control model equation (1), the first furnace outlet plate temperature T _out1 of the _succeeding plate is obtained, and the _routine proceeds to step 3.

In step 3, the first furnace outlet plate temperature T _out1 of the _succeeding plate obtained by the above plate temperature control model equation (1) is:
In the case of being within the allowable range of the target plate temperature T _M and Yes,
When it is determined that the furnace temperature has settled to the set value, the line speed deceleration and acceleration control are terminated. On the other hand, the first furnace outlet plate temperature T
_{When out1} is _out of the allowable range of the target plate temperature T _M and is No, the process proceeds to Step 4.

In step 4, the line speed L _S 'of the _succeeding plate at which the first furnace outlet plate temperature T _{out1 of the succeeding} plate becomes equal to the target plate temperature T _M is determined by using a method described later. That is,
The provisional line speed L _S2 (for example, L _S2 = L _S ×
0.95. ), And the measured furnace temperature T _F2 , measured nozzle pressure P ₂ and the set temporary line speed L _S2 are applied to the above-mentioned plate temperature control model formula (1) to obtain the second furnace outlet plate temperature T _out2 . . Next, the first furnace outlet plate temperature T
_out1 and the second furnace outlet plate temperature T _out2 , the line speed L _S at the time of setting change, and the temporarily set line speed provisionally set value L _S2 , the furnace plate temperature T _out of the succeeding plate is set to the target plate temperature T _{out. M}
Seeking equal line speed L _S 'and, the process proceeds to step 5. The setting of the temporary line speed L _S2 to 95% of the line speed L _S at the time of setting change is based on an empirical rule.

In step 4, when determining the line speed L _S ′ at which the target plate temperature T _M of the succeeding plate can be achieved, the line speed L _S ′ is determined based on the relationship between the furnace outlet plate temperature and the line speed shown in FIG. 1 Furnace exit plate temperature T _out1 and line speed L
_S , and the equation of a line segment passing through two points obtained from the second furnace exit plate temperature T _out2 and the line speed provisional set value L _S2 is regarded as a linear expression and is proportionally distributed.

By the way, the equation of the line segment passing through the two points in FIG. 3 is not a linear equation which is a straight line but a multidimensional equation which is actually a curve. However, since the interval between the two points is extremely small, there is no practical problem even if it is regarded as a linear expression that is approximately a straight line.

By the way, at the time of setting change, as described above, the line speed L _S is set to be the maximum unless there is a limit, and the provisional line speed L _S2 is set to 95% of the line speed L _S at the time of setting change. _Therefore , the target sheet temperature T _M is sandwiched between the first furnace exit sheet temperature T _out1 and the second furnace exit sheet temperature T _out2, and the line speed L _S ′ at which the target sheet temperature T _M can be achieved is: It is sandwiched between the line speed L _S and the line speed provisional set value L _S2 . Certainly, it is preferable that the line speed L _S ′ that can achieve the target plate temperature T _M is sandwiched between the line speed L _S at the time of setting change and the line speed provisional set value L _S2 , but it is necessarily sandwiched. It doesn't have to be, but it can be outside, for example.

In step 5, the line speed L _S '
The furnace outlet plate temperature T _out the target plate temperature T _M of the trailing plate (= T
_out ), and a command is issued from the set value calculator 9 to the line speed controller 8 so that the line speed is controlled so that the line speed becomes the set line speed L _S '.

In the method of controlling the sheet temperature of the continuous annealing furnace according to the present invention, the actually measured furnace temperature T _F1 , which changes every moment from when the furnace temperature is changed until the furnace temperature is settled, is measured. relative pressure P _1, seeking the line speed by repeating steps 1 to 5, and is controlled repeatedly so that the line speed obtained.

According to the sheet temperature control method of the continuous annealing apparatus according to the present embodiment, as described above, even if the furnace temperature does not reach the set value, the furnace temperature is changed after the furnace temperature is changed. Until the calorific value settles, the line speed is repeatedly controlled so that the line speed L _S ′ can continuously achieve the target plate temperature T _M of the succeeding plate at the furnace outlet. Even if the furnace temperature does not reach the set value, the furnace outlet plate temperature _Tout at the furnace outlet of the succeeding plate can be controlled to be within the allowable range of the target plate temperature T _M.

[0028]

As described above in detail, according to the method for controlling the sheet temperature of the continuous annealing apparatus according to claim 1 or 2 of the present invention, the furnace temperature may not reach the set value as described above. Also, the line speed control is repeated until the line speed at which the target plate temperature of the succeeding plate at the furnace outlet can be achieved until the furnace temperature cools down after the furnace temperature is changed. Therefore, unlike the conventional example, even when the furnace temperature does not reach the set value, the furnace outlet plate temperature at the furnace outlet of the succeeding plate can be controlled within the allowable range of the target plate temperature. effective.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a floater type continuous annealing furnace and a control system thereof according to an embodiment of the present invention.

FIG. 2 is a control flow explanatory diagram of a floater type continuous annealing furnace according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a furnace outlet temperature of a material to be processed and a line speed according to the embodiment of the present invention.

FIG. 4 is an explanatory view showing the configuration of a conventional continuous heat treatment furnace and a control system thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Continuous annealing furnace, 1a ... Furnace inlet, 1b ... Furnace outlet 2 ... Material to be processed 3 ... Furnace temperature detector 4 ... Nozzle pressure detector 5 ... Line speed detector 6 ... Furnace temperature regulator 7 ... Nozzle pressure regulator 8 ... Line speed controller 9 ... Set value calculator

Claims (2)

[Claims] 1. A floater type continuous annealing furnace for connecting a preceding plate and a succeeding plate having different target processing conditions, and passing the material to which the preceding plate and the succeeding plate are connected to each other through a furnace for annealing. In the sheet temperature control method, in the process of connecting the preceding plate and the succeeding plate of the material to be processed to pass through the furnace inlet, the sheet temperature, furnace temperature, nozzle pressure, line speed, furnace inlet plate temperature and parameters. The furnace temperature, nozzle pressure, and line speed obtained from the sheet temperature control model formula are set and the settings are changed.The furnace temperature and nozzle measured by the furnace temperature detector are measured until the furnace temperature falls to the set value. Applying the measured nozzle pressure measured by a pressure detector and the line speed to the model formula to determine the first furnace exit plate temperature at the furnace exit of the succeeding plate, and further measuring the actual furnace temperature measured by the furnace temperature detector Temperature, measured nozzle pressure measured by the nozzle pressure detector, and tentatively determined Applying the provisional line speed to the model formula to determine a second furnace exit plate temperature at the furnace exit of the succeeding plate, the first furnace exit plate temperature and the second furnace exit plate temperature, the line speed and the provisional line Floater continuous annealing characterized by obtaining a line speed of a succeeding plate capable of achieving a target plate temperature of a succeeding plate at a furnace outlet from the speed and repeating the control of the line speed so as to reach the determined line speed. Furnace sheet temperature control method. 2. A method for determining a line speed capable of achieving a target plate temperature of the succeeding plate, the first furnace outlet plate temperature and the line speed, and the relationship between the furnace outlet plate temperature and the line speed. The method according to claim 1, wherein a mathematical expression of a line segment through two points obtained from the second furnace exit sheet temperature and the temporary line speed is used.