JPS60114520A - Method for controlling temperature of continuous heating furnace - Google Patents

Abstract

PURPOSE:To control the ejection temp. of billets to a target temp. with less errors in the stage of heating the billet in a continuous heating furnace by operating in combination of the temp. control basing on a mathematical expression model for heat transfer and the measured value of the surface temp. of the billets by a radiation thermometer, etc. CONSTITUTION:Many billets 2 are continuously heated in a continuous heating furnace 1 and are ejected from the furnace then the billets are rolled with a hot roughing mill group 3. The average calculated value thetaSa of the ejection temp. of the billets 2 from the furnace 1 is calculated by a mathematical expression model for heat transfer and the temp. on the billet surface of the billets ejected from the furnace 1 and prior to entrance to the group 3 is measured with a radiation thermometer 4. The temp. of the billet surface is distributed in the rolling direction and therefore such a characteristic value as an average value is calculated by the signal processing function of a calculator 6 for control and is made the measured value thetaEa of the surface temp. of the billets. The target ejection temp. of the billets 2 is corrected from the thetaEa and the calculated value thetaSa and the billets are heated to the temp. optimum to rolling.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature control method for a continuous heating furnace that heats a steel billet to a target extraction temperature by applying a heat transfer mathematical model or the like.

[Prior art]

In the operation of a continuous heating furnace, hot steel billets or hot charge steel billets are charged into the continuous heating furnace, and the furnace temperature and extraction pitch are controlled to heat them to a temperature suitable for rolling. There is.

Traditionally, continuous heating furnaces have been operated by relying on the long experience and intuition of each furnace operator, but in recent years, control computers have come into widespread use, Attempts have been made to minimize the fuel consumption while heating the billet to an appropriate temperature while extracting it in the rolling order and feeding it to the rolling process.

As for temperature control by computer, for example,
There are inventions disclosed in Japanese Patent Publication No. 12325 and Japanese Patent Publication No. 5G-19727.

In these processes, the position and temperature of each billet in the heating furnace is tracked, the location and time in the furnace are predicted from the future rolling schedule, and the temperature rise until each billet is extracted from the furnace is estimated. Then, the furnace temperature and extraction pitch are controlled so that the estimated temperature rise satisfies predetermined conditions. At this time, a known heat transfer formula model that can be easily executed by a control computer is applied to track the temperature of each steel slab and estimate the temperature rise until extraction. Here, the predetermined conditions for temperature control are that the temperature of the steel strip at the time of extraction is within an allowable range, and that the difference in temperature between the inside and outside of the strip is within a certain value, with emphasis on heat uniformity. h are incorporated into the control IT computer as a target extraction temperature condition and a target steel billet internal and external temperature difference condition, respectively.

These conditions are sometimes set based on the material characteristics of the steel billet, but in most cases they are determined empirically based on many years of operational experience. The surface temperature of the steel billet was .

The surface temperature of this steel piece can be determined by the reactor operator using a portable optical high temperature sensor 1 or a fixed radiation thermometer to obtain the temperature value, which is used as extremely important information for reactor operation. Ta.

Although the temperature value measured by this radiation thermometer is input as a temperature signal to the aforementioned control computer, it has not been used as effective information for temperature control. this is,
This is because the temperature value measured by a radiation thermometer is based on thermal radiation energy measurement, and is not the so-called true temperature due to changes in the emissivity of the surface of the steel piece and changes in the measurement position due to rolling conditions. In other words, the control computer applies the heat transfer formula model described above online to calculate the true temperature of the inner and outer surfaces of each steel slab, and the radiation temperature signal, which is only a relative temperature value due to disturbance elements, is It was not possible to compare the actual temperature with the heat transfer formula model solution that calculated the true temperature.

However, this radiation temperature signal is still important furnace operation information, and is recorded as a temperature signal waveform on the record @81 as the surface temperature of each billet, or as the heating record of each billet in the control H1 calculator. The reality is that it is often printed on the form.

On the other hand, the calculation of the temperature of the steel billet by the control computer is performed on a plate m8 due to the ffpt limit on the calculation load, and it can be said that a certain degree of strictness is ignored. Furthermore, when calculating the heat transfer claws to the steel slabs in the heating furnace, the thermal constant is generally determined offline for each furnace zone based on the actually measured temperature rise curve, and then the thermal calculation coefficients are determined offline for each furnace zone. In,
This value is often used as a fixed value. However, these heat division constants change depending on the furnace operating conditions, and it is impossible to modify them online. As a result, temperature control based on a heat transfer formula model applies a temperature calculation method with a certain error, and temperature control based on the calculated value cannot avoid this error.

[Purpose of the invention]

An object of the present invention is to reduce errors in temperature control in a continuous heating furnace.

[Summary of the invention]

In order to achieve the above object, the present invention organically combines temperature control based on a heat transfer equation model and surface temperature measurements using, for example, a radiation thermometer. That is, in temperature control for heating a steel billet to a target temperature from charging to extraction in a continuous heating furnace, the target extraction temperature is corrected based on the calculated value of the extraction temperature and the measured value of the surface temperature of the steel billet after extraction.

Here, "after extraction" refers to the period from immediately after the m piece is extracted from the heating furnace to the initial state during rolling by the rough rolling mill.

Generally, in temperature control of a continuous heating furnace, the target extraction temperature O3 is determined for each product type and size based on experience or material characteristics, as described above. On the other hand, the standard value of the surface temperature of the steel billet after extraction, 0, is given as the basic data for determining the target extraction temperature. On the other hand, there is a value Osa of the extraction temperature calculated by the heat transfer formula model, and a value Oε of the surface temperature of the steel piece measured by a radiation thermometer etc. after extraction.
a exists. Normally, the steel billet surface temperature signal from a radiation thermometer includes temperature fluctuations within each billet based on the temperature distribution in the rolling direction of the billet, but the control computer's internal signal processing function It is assumed that two characteristic values (for example, an average value may be used) are calculated.

In an ideal state, when the calculated extraction temperature value Osa is within a certain tolerance value ΔO8 with respect to the target extraction temperature O8, the measured value O5a of the surface temperature of the steel billet is equal to the temperature difference i (Q value 0).
However, if the determination of the target extraction temperature O8 is unreasonable or a large change in the heat calculation constant as mentioned above occurs, the calculated extraction temperature Osa may be within the range of the allowable value Δ05. Controls that try to match the extraction temperature Os lead to incorrect operation. At this time, if the convergence of the measured value of the steel billet surface temperature 0 (=a) with respect to the standard value θε of the steel billet surface temperature is observed, the possibility of divergence in temperature control using the heat transfer formula model can be avoided.

In some cases, there is also a temperature control method that emphasizes the thermal uniformity of the steel billet by calculating dI of the temperature difference Δtsi between the inside and outside of the steel billet using a heat transfer formula model, and regulating that this value is within the ill capacity value Δts. In this case, add the measured value θRa of the surface temperature of the strip due to the radiation temperature drop at the exit of the rough rolling mill, and use the same method as the target extraction temperature control method to obtain the measured temperature drop 0sa-θFta from the time of extraction to the exit of the rough rolling mill. Temperature drop standard value ΔGap.

It is possible to avoid the possibility of divergence in temperature control by the heat transfer formula model by observing the convergence of the equation.

The present invention will be described in detail below with reference to the drawings.

First, the control calculator calculates the extraction temperature HI value Osa of the steel slab 2 extracted from the heating furnace 1 shown in FIG. 1 by 31n using a heat transfer equation model. Here, the extraction temperature d1 calculated value Dsa
It is well known that T is given by the following function using the current furnace temperature T and the calculated value of the radish pieces immediately before extraction.

Qu=4.88φcg((T+273/100)' (
(ls, -+11-1-273/100)') 5 pieces of steel
The top surface temperature O5 when divided is.

+2λo'Δt/ρ(Δx)2 [φg−1−t(8X/λ)Qll−φr,−tl where.

Qu: Heat transfer claw to the upper surface of the steel piece due to radiation inside the furnace φcg: Parameter expressing radiation efficiency (overall heat absorption coefficient) H'a: Heat content corresponding to 0 degrees. α=s, s-1φ
α: Conversion temperature corresponding to Oα4. α”S, 5-1λ0:
Heat conduction chamber ρ of steel billet: Specific weight ΔX of steel billet: Thickness Δt of steel billet: f, aIIn period of ti1 for control river meter.

Therefore, the steel billet temperature 0s-In just before extraction means the time Δt
The temperature of the two sides of the steel piece will be the same as before.

In addition, the bottom surface temperature Osa and the inside surface temperature Osa [! ”
'2+3+4] is given by the following formula.

11s=Hs-1 2λ0・Δ*/p・cΔX)2[φg-1-φg-1
) However, it was assumed that there was no heat transfer to the top surface of the steel slab due to radiation in the furnace immediately before extraction.

Li)(t))1s=I(s-1+λ.・Δt/ρ・(Δx)”CJs”l’+Js
"12φ'R'-s) However, i = 2, 3, 4 degrees, where, = 2 ~ 5 At this time, to calculate the m piece temperature average value as the extracted temperature calculation value Os, it is recommended to use the following formula 6-3 (i) 0sa =, Σθ5815 t + l In addition, the temperature difference Δtsa between the inside and outside of the rigid piece is To calculate the value, use the following formula.

Δts11=θ5a−Osa Now, for a single heating furnace, the control meter 'r1. Since it is placed under the temperature control of the machine 6, the extraction thermometer λγ value Or,:I is about to converge to the (1 standard extraction temperature O8.) On the other hand,
The surface temperature of this steel piece is measured by a radiation thermometer 4 installed between the rough rolling mill 3 after extraction.

Since the steel billet surface temperature has a temperature distribution in the rolling direction, a temperature waveform as shown in Fig. 2 is produced from 1)), but the signal processing function of the control computer allows for example One 1.1' characteristic value is calculated, and this ill!l constant value is 0.
Regarding 1d, it is a conventional furnace operation tank! (Steel from Q)
“1 A standard surface temperature value OE is given.

1-1 The permissible value ΔOs is set in line with the bleaching temperature Os.
A 7'1 volume value Δ06 is determined for the surface temperature O1.

a) 1(Js C15al≦ΔOs and l Oa
-〇cal≦80L: To Nodosa extraction temperature calculation value Osa
and the measured value of the steel billet surface temperature +1, :a, the target extraction temperature OS and the target surface temperature value 0. Since it converges well with I, the temperature control is stable and there is no need to correct the extraction temperature.

1)) l Os −0str l >ΔO8 and 1
0ε-OI: When Ql≦Δθ, the measured value of the surface temperature of the steel piece OGa is within the allowable value range in line with its standard value Oc, so even though the actual temperature control is stable, The control computer measures the extraction temperature and extracts the value Osa! Since it is outside the fi1 degree 9'1 range, that is, Us-80s and 0!5+80s, it is determined that the control condition is poor.

In order to prevent these control operations from occurring, the target extraction temperature is modified as follows.

0s=Osa+k lΔOs if Us −Osa>
00s=Osa−2ΔOs j, f t)s−Os
ra<0 However, the correction gain is 0, 1≦1.0<k2≦1.

c) IOs (lsal≦ΔO8 and 10E ac
al>Δθ. The temperature control conditions have converged when
The fixed results are out of the norm. However, the radiant temperature t1
Since it is thought that the cause is a change in the measurement conditions of t), we place emphasis on the stability of the humidity control operation and do not perform the 1-1 correction of the degree of stray extraction M.

d) IOs-0sal>ΔO5 and 10a (lc
When al>ΔOo, the billet extraction temperature is not corrected. However, it can be used to determine the convergence of temperature control operations.

■ 08-(JSa>80s and F)c When Oaa>Δor= , the extraction temperature for the previous steel piece according to the heat transfer formula model is Osa, the measured SrM piece surface temperature is Or, a, O8- 0sa<Δ[ノSil and Oa Oc a
<Δ' 1448, it can be said that A is in a transient state of convergence, but if necessary, in order to improve the convergence, temperature control side such as increasing the temperature inside the furnace or lowering the extraction pitch can be applied. Put a foot bag on it.

+L)l 0s-Osa〉8O5 and 13E (Ig
When al≦−Δ05, there is a contradiction between the target extraction temperature and the standard value of the steel billet surface temperature, for example, 0s−Osa>0s−Osa and θa−Oeh<O
If the two determination results are about to diverge in opposite directions, such as r=Oea, the temperature control operation is stopped.

Even in cases other than these, the convergence of the temperature control operation can be increased to 11! can be understood.

In the above, we have described the temperature control method that focuses on the target extraction temperature, but we have also described the temperature control method that focuses on the target temperature difference between the inside and outside of the steel billet. After extraction, roughness is extended 1.
The measured temperature drop value 0εa -ORa and its temperature drop mark 7 (Q value Δ , promote or stop temperature control operations.

Here, the rough rolling mill outlet surface temperature 81 (oRa) is the radiant temperature fit installed at the rear of the rough rolling mill 3 in FIG.
Measured by 5.

Furthermore, this method can also be applied independently to a temperature control method that combines the target extraction temperature and the target temperature difference between the inside and outside of the steel billet.

〔Example〕

An example of implementing the present invention will be described below.

Furnace type 2 top and bottom 3'! iF type butcher furnace heating capacity 1201'/I+ Slab size: 106° x 12m (approximately 1000Kg) 100
Temperature to O+J: 1.000-1250℃ Temperature difference between inside and outside 2
0~50℃ Steel billet surface temperature immediately after extraction: 950~1150℃ Rough rolling mill exit steel No. 1 surface temperature = 800~1ioo℃ Copper type: 0.0
8%C killed steel, 0.8%C eutectoid steel, 1%Cr-Mo steel, I%Crt[.

Stainless Steel When the present invention was applied to the above-mentioned heating furnace, even for 1% Cr-Mo steel for which prior analysis of actual measurement data was insufficient, the copper piece surface temperature was initially 1' The extraction temperature was set to 0s = 11.50°C, but since the extraction temperature (ls = 1120 to 1140°C) was obtained at the steel piece surface temperature measurement value f7I:a = 090 to 1120°C, the target extraction temperature O8 was 1125° It was corrected to C and was able to prevent excessive overheating.And since each temperature was constantly displayed and output as a heating result by the operation guide,
This control method was easily accepted by reactor operators with long experience.

〔Effect of the invention〕

As explained below, according to the present invention, not only can the possibility of divergence in temperature control using the conventional heat transfer formula model be avoided, but also the standard value of the steel billet surface temperature after extraction can be reduced in the future. It is now easy to change the target extraction temperature when changes occur, and it is also easier to set the standard value of billet surface temperature for temperature control of new steel types and determine the target extraction temperature. Became.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an outline of the configuration of an apparatus for carrying out the present invention, and FIG. 2 is a graph showing a measurement output signal of the radiation temperature n1 obtained by measuring the temperature on the surface of a steel piece, and the vertical axis is the output signal. The horizontal axis represents the level and the time. 1: Heating furnace 2: Extracted particles 3: Rough rolling mill group 4: Radiation temperature it (for temperature measurement after extraction)
5: Radiation temperature W+ (for temperature measurement at 1 for m rolling mill quantity) 6: Control computer

Claims (1)

[Claims] (1) In a temperature control method for heating a steel billet to a target extraction temperature from charging to extraction in a continuous heating furnace; the extraction temperature subtraction value and the measured value of the steel billet surface temperature after extraction. It is characterized by correcting the target extraction temperature based on. Temperature control method for continuous heating furnace. (2) A temperature control method for a continuous heating furnace according to claim (1), wherein the extracted temperature calculation value is an average temperature of a steel slab determined by applying a heat transfer mathematical model; (3) The extracted temperature calculation value is the temperature difference between the inside and outside of the steel piece, which was obtained by applying the heat transfer formula model. A method for controlling the temperature of a continuous heating furnace according to claim (1). (4) The temperature of the continuous heating furnace according to claim (1), wherein the extraction temperature 81 calculated value is the average temperature of the steel slab and the temperature difference between the inside and outside of the steel slab determined by applying a heat transfer formula model. Control method. (5) Claim (1) above, wherein the measured value of the steel billet surface temperature after extraction is the steel billet surface temperature immediately after extraction. The temperature control method for a continuous heating furnace as described in item (2), item (3), or item (4). (6) The steel billet surface temperature after extraction 4111 constant value is the steel billet surface temperature immediately after extraction and at the exit of the rough rolling mill, or The temperature control method for a continuous heating furnace according to item (4).