JPH0417621A - Method and device for setting temperature of heating furnace - Google Patents

Abstract

PURPOSE:To automatically control the temp. in a heating furnace where the slabs of different sizes coexist to the values adaptive to the respective slabs by using a specific furnace temp. setting device at the time of subjecting the many steel slabs to a continuous heat treatment in the heating furnace having plural treating zones. CONSTITUTION:A slab temp. computing device 6 computes the temp. of all the slabs in a fresh in-furnace position, tentatively sets a preset furnace temp. to the slabs of the same zone and predicts the slab temp. in the outlets of the respective zones when one piece of the slab is ejected from the heating furnace 9 at the time of subjecting the many steel slabs of the different sizes to the heating treatment in the heating furnace 9 having the plural treating zones. The control rules of a knowledge base 3 are then obtd. from fuzzy inference by a fuzzy inference device 7 in accordance with the deviation from the target temp. 10 in the outlets of the zones and the residence time in the furnace within the same zone determined from the ejection pitch 11 of the slabs. The change rate of the furnace temp. is then determined for all the slabs within the same zone and the slab with which the change rate is largest, i.e., the neck slab is found. The temp. set value at which the neck slab is not overhardened or underhardened is then determined by a furnace temp. computing device 8. This value is outputted and transmitted to the heating furnace 9. The furnace temp. is thus adequately controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) The present invention relates to a method and apparatus for setting a furnace temperature in a continuous heating furnace for heating steel pieces such as slabs in a plurality of continuous zones.

(Prior art) In general, continuous heating furnaces (hereinafter simply referred to as heating furnaces) are used to heat the material to be heated to a temperature suitable for subsequent processes, and to achieve target production in order to minimize energy consumption. It must be operated to ensure sufficient quantity. The biggest problem in operating this heating furnace is how to set the furnace temperature when the load inside the furnace fluctuates, that is, when materials to be heated of different sizes are mixed in the same furnace. That is to say.

To explain this using FIG. 10, inside the heating furnace 2 equipped with the burner 1, from the extraction port toward the charging port, there are slabs St, S2, "', as materials to be heated,
S1. "', So are arranged and the dimensions of the slab S1, for example, the thickness, are different, the thin slab S+ ~ St-+
, S+++ ~S, and set the furnace temperature,
The thicker slab S will be insufficiently fired, which will cause a big problem in the subsequent process.

On the contrary, if the furnace temperature is set for the thick slab S, the thin slabs S1 to SS1+1 to S1 will be overcooked, which will not only increase the scale but also waste energy.

As is well known, it takes a considerable amount of time for the actual temperature of the heating furnace to reach the set value, so it is virtually impossible to set the temperature for each slab individually. be.

Therefore, conventionally, while considering the characteristics of the heating furnace 2 and knowing that some of the slabs S1 to S1 to Sfi will be overheated, at least the slab S is set at the target extraction temperature. The operator had set the furnace temperature of the heating furnace 2 so that the temperature reached . In this way, when the operator sets the furnace temperature, the operator must be familiar with the dimensional information, current temperature information, target extraction temperature information, extraction pitch information, etc. for all slabs in the furnace. Operations relied on experience and intuition.

However, in recent years, it has become difficult to secure skilled operators, and demands for energy saving and stable operation of furnaces have become increasingly strict.

Therefore, recently, a method of automatically setting the furnace temperature without human intervention using an algorithm based on a mathematical formula has been proposed, for example, in "Japanese Patent Application No. 142,613/1981". However, such a mathematical formula The algorithm-based method does not take into consideration the operator's knowledge of flexible furnace temperature settings, so it is not possible to grasp various types of information and perform flexible furnace temperature settings. .

(Problem to be solved by the invention) As described above, conventional furnace temperature settings not only fail to achieve energy savings, labor savings, and automation, but also allow for flexible furnace temperature settings based on the understanding of many types of information. There was a problem that it could not be done.

An object of the present invention is to provide a heating furnace that can save energy, save labor, and automate, and can also set a flexible furnace temperature in consideration of the knowledge of the operator regarding flexible furnace temperature settings. An object of the present invention is to provide a furnace temperature setting method and device.

[Configuration of the Invention (Means for Solving the Problems) In order to achieve the above object, the present invention provides a knowledge base storing control rules regarding changes in furnace temperature and a knowledge base for each item of the continuous heating furnace. Based on the furnace temperature and extraction pitch from the installed furnace temperature detector, a temperature prediction model is used to calculate the current temperature of all the steel slabs in the continuous heating furnace, and the steel slabs at the belt entrance are transferred to the belt exit. A billet temperature calculation means predicts the strip exit temperature of the billet using a temperature prediction model assuming that the current furnace temperature is maintained until reaching the temperature, and A knowledge base constructed for each strip, steel type, and billet size based on the deviation between the predicted exit temperature and the strip exit target temperature, and the short time the billet remains in the strip from its current position until it passes the strip exit. Through fuzzy inference using the control rules of
A fuzzy inference means that calculates the furnace temperature change amount for all slabs in the same zone and selects the neck slab that has the largest furnace temperature change amount among the calculated furnace temperature change amounts; The furnace temperature set value is calculated using the furnace temperature change amount calculated for the neck slab selected by the inference means as the furnace temperature change amount set value for the belt, and the furnace temperature set value is determined for all the belts. Furnace temperature calculation means for outputting the output.

(Function) Therefore, in the heating furnace furnace temperature setting method and apparatus of the present invention, the current temperature of all the steel slabs in the continuous heating furnace is determined in advance using a heat transfer equation based on the furnace temperature and extraction pitch,
The deviation between the predicted temperature at the zone exit and the target temperature at the zone exit, which is determined by the temperature prediction model, assuming that the current furnace temperature is maintained until the slab at the zone entrance reaches the zone outlet, and Based on the short time remaining in the same strip from the current position until passing the strip exit, fuzzy inference using control rules configured for each strip, type of steel, and billet size determines the amount of furnace temperature change within the same strip. This is calculated for all the slabs, and the neck slab with the largest furnace temperature change among the calculated furnace temperature changes is selected, and the furnace temperature change calculated for this neck slab is calculated. The furnace temperature set value is determined as the furnace temperature change amount set value for the zone, and the furnace temperature set value is determined for all zones in the same procedure as described above.

(Example) First, the concept of the present invention will be explained.

Generally, a heating furnace has a large heat capacity and a large time constant, so controlling the furnace temperature by feedback control has little effect. Therefore, from the state of the furnace at the current time,
Feedforward control, which sets the furnace temperature by predicting the furnace condition at a future time, is effective.

FIG. 2 shows slabs 81-S shown in FIG. 10.

This is a diagram showing the state in which the slab S1 is sequentially extracted at each timing, and time t1 represents the time when the slab S1 reaches the extraction port, and this time t1 will be referred to as the current time for the purpose of explanation. Similarly, time t, -1 is the future time when slab S1 reaches the extraction port, and slab S, is extracted at time j++1.

Also, the interval Δ1 between each time. is the extraction pitch, and this extraction pitch Δt1 is determined by the time required for rolling etc. in the post-process, the capacity of the furnace, the product production volume, etc., and may be slightly extended in some cases to ensure the target extraction temperature. It is.

As shown in FIG. 2, the slab S1 is in the furnace from the current time t1 to the future time t2, and the slab S1 is
is from future time t1 to future time t. 1 will remain in the furnace at the extraction port.

In this case, by constantly detecting the furnace temperature and measuring the temperature at the time of charging and the time in the furnace of each slab, the current temperature of all the slabs can be calculated. That is, slab 81~
The current temperature or future furnace temperature of So, as well as the temperature during the period in which it resides in the extraction port, can be calculated using a well-known slab heat transfer model equation.

For example, the following equation is used as this slab heat transfer model equation.

q-σ・ε((θ, +273)'-(θ, +273)
'1... (1) θ, (Δ t) - θ, + (q/k) ・ Δ
t... (2) However, the above equation (1) is based on the furnace temperature θ and the current temperature of the slab θ
Equation (2) is the equation for calculating the temperature of the slab, where q is the amount of heat absorbed by the varnish slab θ1: Furnace temperature θ, current temperature of the varnish slab σ: Stefan Boltzmann constant ε : Heat absorption coefficient θ related to furnace temperature and slab, (Δt): Δ is a constant related to the slab temperature after the time and the properties and dimensions of the varnish slab.

Incidentally, a continuous heating furnace is generally composed of a plurality of zones, and the furnace temperature increases in the order of the pre-heating zone, heating zone, and soaking zone from the slab loading port to the extraction port.

Now, m slabs are placed in one belt from the extraction port (
(equivalent to a soaking zone). Assuming that the current furnace temperature is maintained until m slabs are extracted, slab S1
The temperature of the slab at the time of extraction is not necessarily the extraction target temperature, and baking may be insufficient or overcooked.

Therefore, for slabs that are predicted to have a large deviation between the extraction temperature and the target temperature, the current furnace temperature is changed according to the change rule. The change rules are (a) Temperature deviation between the target temperature at the zone outlet and the predicted temperature (b) Remaining furnace time in the zone (how many minutes after extraction will be done at the current extraction pitch) (c) Slab dimensions (d ) The amount of change in furnace temperature is determined by the conditions of the steel type.

For example, one of the rules for changing the furnace temperature is expressed in the form of ``If the temperature deviation is large (overcooked) and the remaining furnace time is short, the amount of furnace temperature change should be greatly reduced.''

The change rules are “overcooked” and short like this.
This is a method that models the operator's judgment and decision-making, such as the condition of the slab firing and the corresponding change in furnace temperature, and is achieved by using fuzzy reasoning. can do.

That is, if the temperature deviation, remaining furnace time, and furnace temperature change amount are treated as fuzzy variables, their membership relationships are expressed in the shapes shown in FIGS. 3, 4, and 5, respectively. In FIGS. 3 to 5, μ8. μ71μ
m indicates the degree of membership of the fuzzy variables Δθ, , TR, Δθ to each member subfunction. In addition, the membership functions of temperature deviation are NB (quite undercooked), NM (undercooked), Z (properly baked), PN (overcooked), P
The membership functions for the remaining furnace time are NB (fairly short), NM (short) Z(
(intermediate) PM (long) PB (fairly long), and the membership function of the furnace temperature change amount is NB (greatly lowered)
, NM (lower) Z (maintain the status quo) PM (raise) PB (greatly raise).

Next, the fuzzy inference performed by the fuzzy inference means will be described below. That is, the control rules stored in the knowledge base have the following format.

If Δθ1 is Xl and TR is Y, then Δθ□ is W.

Here, X5 is membership functions NB, NM.

Which of Z, PM, and PB is can be, Yl is membership function PB, PM Either Z, NM, or NB can be, Wl is the membership function NBNM Either Z, PM, or PB be.

Control rules are determined for each band layer, slab size, and steel type.

FIGS. 6(a) to 6(c) are table diagrams showing control rules for band layers.

Fuzzy inference in the soaking zone is performed as follows. That is, now Δθ is -+18°C, and TR-
It will be 32 minutes. At this time, the degrees of membership μ of the fuzzy variable Δθ to the membership functions NB, NM, ZPM, and PB are 0.0°0.0.75 and 0.25, respectively (FIG. 3). Also, the degree of belonging to TR, NB, NM, Z, PM, and PB is 0, 0, 0, 0.70° 0.3, respectively.
0 (Figure 4). Then, for each of the 25 control rules in the soaking zone, the fitness of the antecedent part of each rule ω, (
i-1 to 25) are calculated using the following equation (3).

ω, -mint(μ,),, (μm),)...(
3) Here, (μ,)I is the control rule i (i-1°...
・Fuzzy variable Δθ in 25).

, (μT)l represents the membership degree of fuzzy variable TR in control rule i (i””1+...25), and min is the smaller of (μg)+ and (μT)l. It shall take a value.

For example, if the control rule i is expressed as "If Δθ, is PB and TR is PB, then Δθ1 is NM", then (μ, ), -0, 25, (μ engineering)
, -0,30, so ω1-〇,25.

Next, 1W, which is the inference result based on control rule i, is expressed as follows (
4) Calculate using the formula.

ω1wl −min (ωIW1 (y)]...
(4) Here, yεΔθ1. For example, if control rule 1 is expressed as above, W, is NM, so
ωIW+ is the shaded area shown in FIG.

Then, using the inference result ω1W1 based on each control rule i, a composite ambiguous set C8 is created using the following equation (5).

C, -tJ　ω　W ... (5) Here, U is the operation symbol for calculating the union, and j = Ru.

Then, the composite ambiguous set C8 becomes the shaded area shown in FIG.

Next, the center of gravity P1 of the second synthetic ambiguous set C8 is expressed as (
6) Calculate using the formula.

P yaw f C-(y)ydy/ f Cm(y)ydy
...(6) And this calculated center of gravity P1
Let be the inference result regarding the amount of change in the soaking zone furnace temperature.

Assuming that the current furnace temperature is maintained until the slab located in the soaking zone is extracted, the extraction temperature at the future extraction time is calculated, and the current furnace temperature is changed based on the degree of baking and remaining furnace time. The quantity is determined for all slabs located in the soaking zone using knowledge-based control rules. Among these slabs, the slab that requires the largest change in furnace temperature is called the neck slab.

FIGS. 8(a) and 8(b) are diagrams for explaining how to find the neck slab, and are the slab S1 with the largest furnace temperature change amount of each slab, that is, the highest furnace temperature setting value in the diagram.
5 is the neck slab.

This means that, as shown in Figure 9, slab S, 5 is the slab that is least fired among the slabs in the soaking zone, and the amount of furnace temperature change based on fuzzy reasoning is Δθ1. In other words, by raising the furnace temperature to θ,', the slab temperature at the extraction time t1 can be maintained at the target temperature.

An embodiment of the present invention based on the above concept will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of a heating furnace furnace temperature setting device according to the present invention. The heating furnace furnace temperature setting device of this embodiment includes a knowledge base 3, a man-machine interface 4,
It consists of a process interface 5, a slab temperature calculation device 6 which is a slab temperature calculation means, a fuzzy inference device 7, and a furnace temperature calculation device 8.

Here, the knowledge base 3 stores control rules regarding furnace temperature changes, for example, in the if-then format described above. Further, the man-machine interface 4 is used by an operator to update the control rules stored in the knowledge base 3.

On the other hand, the process interface 5 inputs a furnace temperature detection signal from a furnace temperature detector installed in the container of the heating furnace 9 and outputs a furnace temperature set value signal to the heating furnace 9 side. Further, the slab temperature calculation device 6 calculates the temperature based on the furnace temperature detection signal and the extraction pitch from the process interface 5.
The current temperature of all slabs in the heating furnace 9 is calculated using the well-known temperature prediction model described above, and it is assumed that the current furnace temperature is maintained until the slab at the zone entrance reaches the zone exit. The temperature prediction model described above is used to predict the zone outlet temperature of the slab.

Further, the fuzzy inference device 7 includes a slab temperature calculation device 6
The band, steel type, and slab dimensions 12 are determined from the deviation between the predicted temperature at the band exit and the target temperature 10 at the band exit, and the short time 11 remaining in the band from the current position until the slab passes the band exit. The amount of furnace temperature change is calculated for all slabs in the same zone by fuzzy inference using the control rules of Knowledge Base 3 configured for each zone, and the furnace temperature that is the largest among the calculated furnace temperature changes This is to select the amount of temperature change. Furthermore, the furnace temperature calculation device 8 calculates the furnace temperature setting value by using the furnace temperature change amount calculated for the neck slab selected by the fuzzy inference device 7 as the furnace temperature change amount setting value for the belt, and This determines and outputs the furnace temperature set value for each zone.

Next, a method for setting the furnace temperature in the heating furnace furnace temperature setting device configured as above will be explained.

First, when one slab is extracted, the slab temperature calculation device 6 calculates the temperatures of all the slabs at a new position in the furnace. This is based on the slab heat transfer model (1), (
2) It is calculated based on the furnace temperature and the previous slab temperature using the formula. Next, the slab temperature calculating device 6 predicts the slab temperature at each zone outlet for the slabs located in the same zone, assuming the current furnace temperature.

Next, the fuzzy inference device 7 calculates the slab temperature predicted by the slab temperature calculation device 6 and the zone outlet target temperature 10.
Based on the difference between the two slabs and the short time remaining in the same zone determined from the extraction pitch 11 of that slab, the control rules of Knowledge Base 3 are fuzzy inferred and the amount of furnace temperature change is applied to all slabs in the same zone. The slab that requires the greatest amount of furnace temperature change,
In other words, the neck slab is found.

In this way, when a neck slab is found by the fuzzy inference device 7, the furnace temperature calculation device 8 determines the furnace temperature change amount setting value that will not cause the neck slab to become under-fired or over-fired. Heating furnace 9 to find the value
The output is transmitted to the side.

In this case, the furnace temperature set value is determined by adding the neck slab furnace temperature change amount determined by the fuzzy inference device 7 and the current furnace temperature.

The above calculations are performed in the same way for each band saw, and the furnace temperature setting value for each band saw is determined.

As mentioned above, in this embodiment, extraction is performed from time to time, and as the slab composition located in the soaking zone changes, such neck slabs are successfully found and there is no over-baking or under-baking. This makes it possible to automatically change the furnace temperature. In addition, taking into account the operator's knowledge of flexible furnace temperature settings, the most detailed parts of furnace temperature settings can be incorporated into the control rules, making it possible to set furnace temperatures flexibly. .

Furthermore, since the furnace temperature can be set automatically, it is possible to save energy and labor.

Furthermore, since fine adjustments to the control rules can be made by simply adjusting the membership function, there is no need for a major software review of the entire furnace temperature setting logic of the control computer, making software maintenance extremely easy. .

[Effects of the Invention] As explained above, according to the present invention, it is possible to achieve energy saving, labor saving, and automation, and also to create a flexible furnace that takes into consideration the knowledge of the operator regarding flexible furnace temperature settings. A heating furnace furnace temperature setting method and apparatus capable of setting the temperature can be provided.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the heating furnace furnace temperature setting device according to the present invention, Fig. 2 is a diagram for explaining the slab extraction timing and the position in the furnace, and Figs. 3 to 5 show the furnace temperature. Figure 6 is a table diagram showing the control rules used in fuzzy inference. Figure 7 is a diagram to explain fuzzy operations used in fuzzy inference. Figure 8
The figure is a diagram to explain the neck slab for changing the furnace temperature, Figure 9 is a diagram to explain the furnace temperature change and slab temperature change, and Figure 10 is a diagram to explain the technical problems of heating furnace operation. This is a diagram for DESCRIPTION OF SYMBOLS 1... Burner 2... Heating furnace, 3... Knowledge base, 4... Man-machine interface, 5... Process interface, 6... Slab temperature calculation device, 7
...fuzzy inference device, 8...furnace temperature calculation device, 9.
...Heating furnace, 10...Target outlet temperature, 11...Extraction pitch information, 12...Slab information. Applicant's agent Patent attorney Takehiko Suzue Ward 9 Kia P Day M (minutes) Figure 4 F5 Atjl: I! (@C) Figure 5 (b) 8th Ward House Gokora! Run! I('C) Map $ 10th ward

Claims (2)

[Claims] (1) In a method for setting the furnace temperature of a continuous heating furnace that heats slabs or other steel slabs in a plurality of continuous bands, the current temperature of all the steel slabs in the continuous heating furnace is determined based on the furnace temperature and extraction pitch. is calculated in advance using the heat transfer equation, and the band exit prediction is calculated using the heat transfer equation, assuming that the current furnace temperature is maintained until the billet at the band entrance reaches the band exit. Using control rules configured for each strip, steel type, and billet size, based on the deviation between the temperature and the target temperature at the strip exit, and the remaining furnace time in the same strip from the current position until the billet passes the strip exit. Then, by fuzzy inference, the amount of furnace temperature change is determined for all slabs in the same zone, and the neck slab with the largest amount of furnace temperature change among the determined furnace temperature changes is selected, and the neck slab is The furnace temperature set value was determined by using the furnace temperature change amount determined for the steel slab as the furnace temperature change amount set value for the zone, and the furnace temperature set value was determined for all zones using the same procedure as above. A heating furnace furnace temperature setting method characterized by: (2) In a device for setting the furnace temperature of a continuous heating furnace that heats steel pieces such as slabs in a plurality of continuous bands, a knowledge base storing control rules regarding changing the furnace temperature, and each of the continuous heating furnaces. Based on the furnace temperature and extraction pitch from the furnace temperature detector installed in the belt, use a temperature prediction model to calculate the current temperature of all the steel slabs in the continuous heating furnace,
A billet temperature calculation means for predicting a strip outlet temperature of the steel billet using the temperature prediction model assuming that the current furnace temperature is maintained until the billet at the strip entrance reaches the strip outlet; , From the deviation between the band exit predicted temperature and the band exit target temperature predicted by the billet temperature calculation means, and the remaining furnace time in the same zone from the current position until the billet passes the strip exit, the strip and Using fuzzy inference using the knowledge-based control rules configured for each steel type and billet size, the amount of furnace temperature change is calculated for all slabs in the same zone, and the calculated amount of furnace temperature change is fuzzy inference means for selecting the neck slab with the largest amount of furnace temperature change among them; A furnace temperature setting device for a heating furnace, comprising a furnace temperature calculation means for calculating a furnace temperature set value as a set value, determining and outputting the furnace temperature set value for all zones.