JPS599125A - Method for setting temperature of heating furnace - Google Patents

Abstract

PURPOSE:To make contribution to the improvement in the size and quality of products, by calculating and setting the temp. in the transverse direction of a heating furnace from the temp. of the material to be heated at the present temp., the target temp. of the material to be heated after a specified time and the prescribed temp. gradient in the longitudinal direction of the material to be heated. CONSTITUTION:Two units of control devices 61, 62 for furnace temp. are provided in the transverse direction of a furnace. When a set furnace temp. thetag1REF is given, a burner 21 is operated by a thermometer 51, a subtractor 91 and the device 61, and the temp. in the furnace is maintained at thetag1. When a set furnace temp. thetag2REF is given, a burner 22 is operated by a thermometer 52, a subtractor 92 and the device 62 and the furnace temp. is maintained at thetag2. Therefore, a furnace temp. gradient can be made in the transverse direction of the furnace. Thereupon, the above-described thetag1REF, thetag2REF are calculated and set from the temp. thetag1 of a slab 1 at the present time, the target temp. thetag2 of the slab 1 after a specified time and the prescribed temp. gradient DELTAthetaM in the longitudinal direction of the slab 1.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for setting the furnace temperature of a heating furnace for heating a material to be heated such as a slab, and particularly to a method for setting a furnace temperature in a furnace width direction, that is, a longitudinal direction of the material to be heated. ensure the temperature gradient at a predetermined value, and
The present invention relates to a furnace temperature setting method in the furnace width direction for maintaining a material to be heated at a target temperature.

[Technical background of the invention and its problems]

A heating furnace, for example, a continuous slab heating furnace (hereinafter simply referred to as "heating furnace 1"), heats the material to be heated (hereinafter referred to as "slab J") to a temperature suitable for the subsequent process while minimizing energy consumption. It must be operated in such a way as to ensure the production number of

FIG. 1 is a block diagram showing a typical heating furnace.

Slab 1 is from charging port 3 to extraction port 4-! , a preheating zone 101 surrounded by a furnace wall 10. Heating zone 102. While passing through the soaking zone 103, it is heated and extracted at the extraction target temperature. The furnace temperature detected by the furnace thermometer 5 in each zone is fed back to the subtractor 9, and the furnace temperature in each zone is controlled by the furnace temperature control device 6 to operate the burner 2 to reach the operator's set value θRgF. be done. Further, the slab 1 is loaded so that its length direction is in the furnace width direction of the heating furnace.

Generally, in the rolling process after the heating furnace, it is necessary to suppress the temperature gradient in the longitudinal direction of the slab within a predetermined range in order to improve the dimensions and quality of the product.

For this reason, in consideration of the temperature drop in the longitudinal direction of the slab in each step after extraction in a heating furnace, an operation is carried out in which the temperature in the longitudinal direction of the slab during extraction is given a gradient. This can be achieved by creating a gradient in the temperature inside the furnace in the width direction of the heating furnace, that is, in the length direction for the slab in the furnace.

Conventionally, when creating a temperature gradient in the slab length direction, the furnace temperature was set by the furnace temperature control device in the furnace width direction based on the operator's experience and intuition.

Furthermore, in recent years, with the spread of computers, computers have been introduced into heating furnace systems, and complex calculations such as the calculation of the slab temperature from moment to moment and the set furnace temperature to obtain a predetermined slab temperature are performed. Processing has become possible, but sufficient computer control has not yet been achieved.

In view of the above-mentioned points, the present invention provides means for accurately setting the furnace temperature, which ensures the temperature of the slab at a target value and the temperature gradient in the longitudinal direction of the slab at a predetermined value, using computer calculations. The purpose of this invention is to provide a method for setting the furnace temperature of a heating furnace, which is effective in improving the dimensions and quality of products.

[Summary of the invention]

The present invention is equipped with a furnace temperature control device capable of creating a temperature gradient in the furnace width direction and a temperature i1' that detects the furnace temperature in the furnace width direction, and sets the temperature of the material to be heated to a target value after a certain time from the current time. The method of setting the furnace temperature in the furnace width direction to ensure that the temperature gradient in the length direction, which is the furnace width direction, of the material to be heated is set to a predetermined value has been changed. From the temperature of the material to be heated at , the target temperature of the material to be heated after a certain period of time, and the temperature gradient in the length direction of a predetermined material to be heated by heat conduction analysis that relates the slab surface temperature and the slab average temperature, This is a furnace temperature setting method for a heating furnace in which the furnace temperature in the furnace width direction is derived and set.

[Embodiments of the invention]

Hereinafter, the present invention will be specifically explained with reference to Examples.

In each drawing, the same reference numerals represent the same or corresponding parts.

FIG. 3 shows a sectional view taken along line 8-Ao of the slab and a certain band moving through the heating furnace shown in FIG.

However, in order to simplify the explanation, it is assumed that the furnace temperatures at the upper and lower parts of this belt are equal, and only the upper part is shown in Figure 3.

As shown in Fig. 3, the furnace temperature control device 61.6 is placed in the furnace width direction.
There are two 2s.

Now, when the set furnace temperature θ72 is given, the burner 21 is operated by the furnace thermometer 51, the subtractor 91, and the furnace temperature control device 61, and the furnace temperature is maintained at θ·gl. Similarly, when the set furnace temperature θ number 1 is given, the burner n is operated by the furnace thermometer 52, the subtractor 92, and the furnace temperature control device 62, and the furnace temperature is maintained at θg2. Therefore, the two furnace temperature control devices 1f61 and 1f62 each have a furnace temperature set value θv. By giving θζy, it is possible to create a furnace temperature gradient in the furnace width direction.

Therefore, the positions on the slab 1 directly below the furnace thermometers 51 and 52 are defined as xl and x2 from the tip of the slab, and the slab upper surface temperature at the slab upper position x1 is θl11, the average in the thickness direction of the slab at the same position. The temperature (hereinafter, average temperature is simply referred to as the average temperature in the thickness direction) is θ98, the slab upper surface temperature at position x2 on the slab is 06□, and the average temperature at the same position is θ7□.

The temperature gradient in the slab length direction is a gradient in the slab length direction that connects the average temperature θM1 at the position x1 on the slab and the average temperature θM2 at the position S2.

Therefore, the temperature gradient in the slab length direction is
, the difference between the average temperature θ□ at position x2 and the average temperature θ4□ at position x2 (hereinafter referred to as the temperature difference in the slab length direction) Δ
Determined by θ. That is, ensuring the temperature gradient in the slab length direction at a predetermined value means ensuring that the temperature difference Δθ in the slab length direction is at a predetermined value.

The present invention provides a furnace temperature setting value that maintains this temperature difference Δθ in the longitudinal direction of the slab at a predetermined value, RE! It is necessary to find gl g2 and F and TLEF.

Here, the change in slab temperature over time is the fourth
Consider the case shown in the figure.

Current time t. The surface temperature at position x1 on the slab is 08, (to), the average temperature is θMl (tO), the surface temperature at position X on the slab is θ52 (to), and the average source power is 0M2 (tO).

Consider the case where after a certain period of time Δ, the temperature difference Δθ in the slab length direction is reduced to a predetermined temperature difference Δθ, and the average temperature θM2 (tO+Δt) at the slab top position x2 is maintained at the target temperature θ[P″. , the average temperature θM2 at the position x2 on the slab is taken as a representative point of the temperature of the slab.

By the way, the temperature difference KF Δθ in the predetermined slab length direction is the temperature drop in the process after extraction in the heating furnace]'
The target temperature θ is given in consideration of tEF, and the target temperature θ is given for each slab position in the furnace based on the slab temperature heating pattern that ensures the extraction target temperature at the extraction time and takes energy saving into consideration.

Average temperature θMl('O+Δt) at time (to+Δt)
t) is the heat transfer from the furnace temperature θ, , tq□1 and the furnace temperature θ3
Upon receiving heat transfer lq2□ from °, θMl (tO+Δ1) = θMl (tO) +-(q1
1+q;g)・Mountain Cρh・・・・・・・・・(1 formula) ql,=・Φ1□(θ7□2−θslk”O”・・・・
...(2 formulas) q2. =σΦ21(6g2k ”e
lk(tO) l ”・・・・・・(3 formula)% formula% σ is Stefan Boltzmann constant, C is specific heat, ρ density, h is thickness, Φ1□ is furnace temperature θ2, and position on the slab from X , the heat absorption rate, Φ2, determined by experiments etc. from the furnace temperature θ3° to the upper slab ft'l, X 2
The heat absorption rate is determined by experiments, etc., where k is the subscript indicating the absolute temperature.

At this time, the surface temperature θsl (tO+c) can be calculated from the right eye of the heat conduction angle, which relates the surface temperature and the average internal temperature of the slab and controls the average temperature, which has been elucidated in the present invention. O+Δt)+, (
q,,"q21) (Formula 4) Here, kl is a constant determined by slab 1.

It can be expressed as

In exactly the same way, regarding position X2 on the slab...
...(5 formula) q12=σΦ12(θglk-08□k(1o))=-
...-(Equation 6) q22=σΦ2□ (0g2 - θ52
k (tO)) ...... (Formula 7) However, Φ1゜ is the heat absorption rate from the furnace temperature θg1 to the slab top position X2-・, Φ2□ is the slab top position X2 from the furnace temperature θg2 The heat absorption rate to is .

Still, θ52 (tO + Δ1) = θM2 ('O + Δt) 1/10 (
q1□+q2□)・・・・・・・・・(Equation 8) Here, if the temperature difference in the predetermined slab length direction at time (to+Δt) is Δθ, then θMl(tO+Δ1
)=θM2(tO+Δt)+ΔθRFF...-(Equation 9)
The average temperature θM2(
'O+Δt) is RF'F ・・・・・・・・・(Formula 10)%
Formula %). At this time, from (Equation 9) and (Equation 10), the slab -
The average temperature θMl ('O+Δt) at the upper position X is θ (t+Δ1)=θ +Δθ ・・・・・・・・・
・(Formula 11)% Formula %. Therefore, (Equation 2), (Equation 3), and (Equation 14) are (
(1), (6), (7), and (1)
By substituting (Equation 0) into (Equation 5), we can calculate the furnace temperature θ
Solving for the furnace temperature θ3°, we get l...(Equation 12)...(Equation 13).

That is, the current time t. The average temperature θ and □(1o) at the position x1 on the slab and the surface temperature Osl”O) at the position x
2 average temperature θM2 (to) and surface temperature θ8□ (1o)
From the temperature difference Δθ in the longitudinal direction of the slab and the target temperature θ2'', the furnace temperature θg1 and the furnace temperature θg2 are determined using equations (12) and (13), respectively, and the furnace temperature control system for the furnace width j direction is calculated. Trade Fi
If the set values of l and fi2 are θ and θ, it is possible to create a predetermined temperature gradient in the longitudinal direction of the slab in time gl g2 Δ from the current time 'Q, and to ensure that the slab temperature is at the target temperature. I can do it.

The above is a method of creating a temperature gradient in the length direction of one slab.

In a continuous heating furnace, when the length of one slab is short, so-called two-row charging is performed in which two slabs are charged in the width direction of the furnace. In the case of this double row charging, if we use the concept of temperature gradient inside the furnace in the width direction of the furnace, we can independently heat the two wooden slabs to the target temperature by creating a furnace temperature gradient in the width direction of the furnace. is possible.

Another embodiment of the present invention will be specifically described below with reference to FIG.

Considering the case where two slabs S 1+ 82 are charged in the width direction of the furnace, the slab S1 is heated to the target temperature θ for a certain period of time Δt1, and the slab S is heated to the target temperature θ for a certain period of time Δt1.
The furnace temperature in the furnace width direction for heating to the target temperature θM2 at 2Δt2 is determined.

! P, current time t. The average temperature of slab S1 at θM+('O) and the surface temperature at θ8. (1o), the average temperature of the slab S2 is θ4□ (1o), and the surface temperature is θ8° (1o).

Slab S1 was heated for 311 hours at a furnace temperature of θ8. 2, the average temperature of the slab S at time (1o + Δ) is the heat transfer risk Qll of (Equation 2) and (Equation 3).
Using l921 (Formula 14), cl is the specific heat of the slab S, ρ1 is the density of the slab S1, and hl is the thickness of the slab S1.

Similarly, if slab S2 is heated at furnace temperature θ3□ for 42 hours, slab S2 at time (1o+Δ12)
The average temperature of (Equation 6) and (Equation 7) is the heat transfer difference q1゜・q2
Using °... (Formula 15) Where, C2 is the specific heat of slab S2, ρ is the density of slab S2, and h2 is the thickness of slab S2.

Therefore, in order to bake the slab S1 to the target temperature EF θ for a certain period of time Δt1, I RFF . In order to bake to θ, 2 O F ...... (17 formula) % formula %) Here, (2 formula), (3 formula) and (16 formula) are converted to (14 formula)
and (Equation 6), (Equation 7) and (Equation 17)
Substitute into (Equation 15) and create a furnace? n Og
We can solve for I+03□.

That is, in FIG. 5, in order to heat the slab S to the target temperature θ4 in 411 hours and to heat the slab S2 to the target temperature θ in 712 hours, the furnace temperature θg1 determined by means 2 described above must be The furnace temperature θ2□ is controlled by the furnace temperature control device 6.
1 and 62 furnace temperature set value 01F'50REF,! Just give it to me gl g2.

These methods are only possible by setting the furnace temperatures on the slabs independently, and are extremely effective methods in that they can independently ensure the temperature of each slab during two-row charging.

FIG. 6 is a block diagram showing the configuration of an embodiment of the present invention.

G is the activation signal of the present invention, and may be an extraction signal generated when the slab 1 is extracted from the heating furnace, or may be a constant periodic signal. When signal G is activated, first the slab temperature calculation device 7
The current time is t. Slab position X of target slab 1 in
and x2 average temperature θMl('O), θhtz(t(1
) and surface temperature θsl''O''θs2''0).

The slab average temperature and surface temperature it W are (equation 1) ~
Using the relationship of (8), the total v4[2 may be t2, and the well-known heat conduction method formula may be converted into a form that can be expressed numerically using a subtraction machine and calculated moment by moment.

Next, the output of the slab temperature calculation device 7, that is, the average temperature at the slab ff4', x t, θMl('O)1
Surface temperature θ (1) and average temperature θ at position
M2(,.).

sl O2 surface temperature θ52 (tO'), target temperature θ determined from the slab temperature jKf - temperature increase pattern, and a predetermined slab length direction to be applied to the target slab furnace position determined from the temperature gradient in the length direction of the gas slab required during extraction. From the temperature difference Δθ, the furnace temperature θgI 10g2 to be set in the furnace width direction is determined by (formula 12)
Calculation is performed by the set furnace temperature calculation device 8 using (Equation 13). The output of the set furnace temperature calculation device 8 is the furnace temperature θ to be set for a period of time Δ from the current time.

The burner 2I is adjusted by the furnace temperature gauge 51 and the furnace temperature control device fil so that the temperature becomes 1. Similarly, the burner 22 is adjusted by the furnace temperature side 52 and the furnace temperature controller 62 so that the furnace temperature immediately above the slab position x2 becomes θ.

[Effects of the Invention] Thus, according to the present invention, when the slab is extracted from the heating furnace, it is possible to create a temperature gradient in the longitudinal direction of the slab, which is required in the subsequent process. Since the slab temperature is calculated moment by moment, it is possible to set the furnace temperature with extreme precision in response to changes in the thickness of the target slab or changes in the temperature gradient value in the specified slab length direction. You can expect an improvement in product quality 9 dimensional accuracy.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the entire continuous slab heating furnace, Figure 2
Figure 3 is a plan view of a zone in which a heating furnace is located, Figure 3 is an explanatory diagram of an embodiment of the present invention in a cross-sectional view taken along line A-A', Figure 4 is a temperature one-hour characteristic diagram of each variable, and Figure 5 is an explanatory diagram 1 of another embodiment of the present invention. Figure 6 is a block diagram showing the configuration of an embodiment of the present invention. 1 + 81 + 82 mountain slab 2, ha, 2? ...Burner 3...Charging port 4...Extraction port 5.5], 52...Furnace thermometer 6, 61.62...Furnace temperature control device 7...Slab temperature control Device 8... Setting furnace temperature calculation device 9.91.92... Subtractor 10... Furnace wall. Applicant's agent Kiyotan Inomata 2 figures city 4 figures opening - 16 figures

Claims (1)

[Claims] Equipped with a furnace temperature control device that can create a temperature gradient in the furnace width direction and a thermometer that detects the furnace temperature in the furnace width direction, the temperature of the heated material is maintained at the target value after a certain period of time from the current time. In a furnace temperature setting method for a heating furnace that sets the furnace temperature in the furnace width direction to make the temperature gradient in the length direction, which is the furnace width direction, of the heating material to a predetermined value, A furnace temperature setting method for a heating furnace, characterized in that the furnace temperature in the furnace width direction is set by calculating a percentage from a later target temperature of the material to be heated and a predetermined temperature gradient in the length direction of the material to be heated.