JPH03207823A - Method for determining material heating curve in heating furnace - Google Patents

Abstract

PURPOSE:To determine a material heating curve capable of improving precision in the rolling dimensions at the time of determining the curve for a heating furnace by taking the furnace temp. correction amt. inputted by an operator into consideration. CONSTITUTION:The furnace temp. setting means 106 for a heating furnace 101 is formed with an actual temp. calculating means 20, a heating curve calculating means 21, a set furnace temp. calculating means 22 and a parameter change calculating means 23 and periodically started. The present material temp. is calculated by the means 20 using the actual furnace temp. based on the material information such as the dimensions and weight of the material in the furnace, extraction temp. and in-furnace conveyance information from a material information means 102. The parameter is changed by the means 23 based on the set furnace temp. correction value from an operator input means 107, a heating curve for each material is determined by the means 21 based on the input value from the means 20 and 23, and the set furnace temp. is indicated to a fuel flow controller 103 through the means 22. Consequently, a heating curve matching the image of an operator is determined.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for determining a material temperature rise curve of a heating furnace in a hot rolling line.

[Conventional technology]

FIG. 4 is an explanatory diagram showing a process in which the charging temperature of a steel billet is determined based on elapsed time in the conventional continuous heating furnace control method disclosed in, for example, Japanese Patent Publication No. 5B-18401. This invention attempts to control the temperature inside the heating furnace according to the temperature of the sea bream pieces, and various temperature measurements of the sea bream pieces have been carried out. Let us explain how to find it.

First, continuously cast steel pieces are cut into predetermined lengths after continuously casting molten steel (step ST4.1).

At this time, the temperature of the steel billet is controlled to a constant value (approximately 800"C) by the water cooling control attached to the continuous casting equipment, and is measured with a thermometer.The temperature of the steel billet charged into the continuous heating furnace as a temperature control piece is A few hours after cutting, it is loaded into a heating furnace.
At this time, the charging temperature θ, 1 is calculated using the following heat transfer equation based on the cutting time of the rope, the temperature of the steel slab at the time, the time of charging into the continuous heating furnace, and the dimensions of the steel slab (step ST2).

However, θ(t.x): Material temperature t: Time (elapsed time from cutting time) H: Slab thickness initial condition θ(0,x)=θ.

θ. Billet temperature at the end of two continuous casting Boundary conditions ■ Center ■ Surface?・■・θ (t, O) =4.88・εθy? : Emissivity with the atmosphere θ■P :Ambient temperature When the elapsed time until the charging time t=n, the average temperature in the thickness direction is used as the charging temperature θ1 as shown in the following equation. Charging temperature θ. 7, the charging temperature θ in the heating furnace
Using i as the initial value, the furnace temperature of each zone is controlled so that the predicted extraction temperature of the steel slab matches the target extraction temperature, and the heat transfer equation is calculated for each zone furnace temperature based on the remaining furnace time of each zone until extraction. Solve by assuming (step ST4.3, ST4.4')
If the extraction temperature is predicted and there is a deviation from the target value, the assumed furnace temperature is corrected again and calculations are repeated until they match to find the set furnace temperature, and the temperature rise curve of the material is calculated using the results. Determine (step ST4.5). [Problem to be solved by the invention] Since the conventional method for determining the material temperature rise curve of a heating furnace is performed as described above, it is necessary to calculate the amount of correction when there is a deviation between the predicted and desired furnace temperature once assumed. It has to be done by trial and error, and since the heat transfer equation is solved, calculations take time when the number of slabs (steel slabs) in the furnace increases, so it is not suitable for online calculations. In addition, when considering the rolling process, there were issues such as a decrease in dimensional accuracy during rolling because no consideration was given to the temperature difference between the skids (sliding members) and the skid part (hereinafter referred to as uniformity). ．． In addition, the determined furnace temperature does not necessarily match the operator's image, and in that case, without a man-machine interface with the furnace control zone, intervention is not possible, and the operation ends up switching from automatic to manual. , there were issues such as a decline in the application rate of automation. This invention was made to solve the above-mentioned problems, and it is possible to determine the temperature rise curve in a short time, and improves dimensional accuracy during rolling by incorporating two types of temperature conditions at the skid part and between the skids. The purpose of this study is to obtain a method for determining the material temperature rise curve of a heating furnace that can increase the application rate of automatic control. [Means for Solving the Problems] A method for determining a material temperature rise curve for a heating furnace according to the present invention is to obtain two types of slab average temperatures between the skid portion and the skid using a slab temperature prediction formula model, and calculate the slab average temperature. The slab average temperature sensitivity during extraction for each zone furnace temperature is determined using the slab average temperature sensitivity formula during extraction, and the correction amount when the slab is in each zone is determined using the modified furnace temperature calculation formula, and each zone furnace temperature is calculated using When the operator inputs a furnace temperature correction value during the calculation cycle of the corrected furnace temperature calculation formula, each correction value is determined by the parameter calculation formula, and the correction is reflected in the next cycle.

[For production]

The method for determining the material temperature rise curve of a heating furnace according to the present invention is to obtain two types of slab average temperatures between the skid part and the skid using a slab average temperature calculation formula, and then use a prediction model to calculate the temperature of the slab at the time of extraction relative to the furnace temperature. Temperature sensitivity is determined by calculating the slab average temperature sensitivity formula during extraction. Furthermore, a convergence calculation is performed on the required furnace temperature for each zone based on the extraction target temperature and target soaking degree using the sensitivity, adjustment gain, and prediction model to determine the temperature increase curve. In addition, when the operator inputs the amount of correction for each zone temperature while online, the amount of correction is calculated using a parameter calculation formula and is corrected online to enable control that matches the operator's image. [Embodiment of the Invention] An embodiment of the invention will be described below with reference to the drawings. 1st
The figure shows a conceptual diagram of a heating furnace. In order to maintain each control zone stably, each control zone is divided into three zones, for example, a preheating zone, a heating zone, and a soaking zone, and the temperature is controlled. Further, FIG. 2 is a block diagram showing the control system of the heating furnace.
, the parameter change calculation means 23 at the time of operator intervention. Information is given to the current temperature calculation means 20 from the material information means 102 as a parameter. Also,
101 is a heating furnace divided into zones and has multiple sets of fuel flow rate controllers 103, and in order to enable independent temperature control for each zone, a furnace temperature detector 104 and a combustion burner 1 are installed.
It is equipped with 05. When the operator inputs a set furnace temperature correction value using the operator input means 107 while online, the parameter change calculation means 23 corrects any of the extraction target temperature, target soaking degree, and adjustment gain through the operator input means 107. do. Based on these parameters, the temperature rise curve calculation means 2l determines a material temperature rise curve that matches the operator's image from the next cycle. Next, a calculation method for determining a material temperature increase curve will be explained with reference to the flowchart in FIG.

First, the equations for the slab average temperature are shown in equations (1) and (2). θ,. =01+(θ,.-,-θ*=>expr a
, i・tt#＞・・・・・・・・・ (1) /(θ,8−θji−1) ・・・・・・
... (2) Here, θji' slab average temperature ac: correction coefficient θ, . : Set furnace temperature C. : Specific heat t, : Predicted remaining furnace time γ : Specific gravity H : Slab thickness σ : Stefan Boltzmann constant i : Band (i=1.3) j : Skid part/space (j-1.2) Equation (1) is Predicted remaining furnace time LL, slab thickness H, set furnace temperature θ, . is given, the average temperature of each strip exit side slab θ, . is calculated (slab temperature prediction formula model).

First, in step STI, initial values θ and 8 of each zone furnace temperature are set using table values. In addition, the draw of equation (3)? Using the slab average temperature sensitivity formula, the slab average temperature sensitivity for each zone temperature can be found by partial differentiation with respect to each zone furnace temperature θ1. Fjk - θθj3/θθ■ ・・・・・・・・・
- (3) (j = 1. 2. k = 1. 3) (1) in step ST2. From equation (2), the slab average temperature θ,1 during extraction is determined, and in step ST3, (4),
Check whether formula (5) is satisfied. ...
...... (4) (5) Here, j is the belt where the slab exists.

Subsequently, in step ST4, the slab average temperature sensitivity is determined using equation (3). Here, in step ST5, if equations (4) and (5) are not satisfied based on the following case classification, the correction amount Δθ of the corrected furnace temperature. (modified furnace temperature calculation formula).

(i) If the slab is in the preheating zone (a) If both equations (4) and (5) are not satisfied here, β is a table value or an online calculation. calculation value.

(b) When only formula (5) is satisfied here, βI β2 is a table value or an This is an online calculation value.

(ii) When the slab exists in the heating zone (a) When both equations (4) and (5) are not satisfied (b) When only equation (5) is satisfied? Here, α is a table value or an online calculated value.

(ii) If the slab exists in the soaking zone, pus'Δθ,
3-θ13AIM-θ. ．． -----・-(10)
In this way, the correction amount Δθ■ can be found by solving the above equation.

θ, i is Δθ. Add 1 (θ,, +Δθ,, →θ,
．． ). Then, the processing in steps ST2 to ST5 is repeated until equations (4) and (5) are satisfied.

If the operator inputs the furnace temperature correction value during this cycle, the table value or the calculated value β, β1 . β2, α, extraction target temperature and target soaking degree are corrected and reflected in the next cycle (step ST7),
In order to correct the necessary furnace temperature for the existing zone of the slab determined in step ST5 using the operator's furnace temperature correction value and replenish the correction amount, the following process is performed.

(iv) If the slab exists in the preheating zone (a) (4)
, What if both equations (5) are not satisfied? 11) is convergently calculated and the gain of the following equation is reflected in the next cycle.

β=(θ, 1-θ■M) θ, -θ,! 1')B,,
g= (θ, isam10, t””)/2 (i=1
．． 2) (b) When only formula (5) is satisfied β1 = (θ1 - θ,.') / (θ,, 10, 1) β2 =
(θ, 2-θ-z')/(θg3-θ, ♂) (v) When the slab exists in the heating zone (a) When both equations (4) and (5) are not satisfied...
・・・・・・・・・(13) Convergent calculation of equation (13) to calculate ΔΔθ (target uniformity degree correction amount)
will be reflected in the next cycle.

(b) When only formula (5) is satisfied FI3・Δθ,,=θ,AI′−θI3...
...(14) Convergently calculate the equation (14) and reflect the gain of the following equation to the next cycle.

α=(θ.2−0.2κ)baθ,,−θg−)(vi)
If the slab exists in the soaking zone, the furnace temperature determined in step ST5 is corrected by the operator correction value, and at that furnace temperature, the average temperature of the slab during extraction is calculated using equation (1), and the deviation from the extraction target temperature is transferred to the next cycle. reflect. Δθ = θ1, −θ. ^1M In this way, although the variables to be reflected in the next cycle differ depending on each case, the table value β used in step ST5
, β1, β2, α or Δθ, ΔΔθ are reflected in the target values to obtain a material temperature rise curve that matches the operator's image.

Next, heating furnace control based on one embodiment of the present invention will be explained with reference to FIG. 2.

In FIG. 2, a heating furnace 10 divided into a plurality of control zones
1, a combustion burner 105 and a furnace temperature detector 104 are arranged, and the fuel flow rate controller 103 controls the flow rate to t? so that the temperature reaches the set temperature for each control zone set by the furnace temperature setting means 106. It has been ilJllI. Reference numeral 102 is a material information means, which provides information on the dimensions, weight, extraction temperature, etc. of the material in the furnace.
Material information such as in-furnace conveyance information is instructed to the furnace temperature setting means 106. Further, when the operator inputs a set furnace temperature correction value while online, the furnace temperature setting means 106 recognizes it by the operator input means 107.

The furnace temperature setting means 106 consists of a current temperature calculation means 20, a temperature increase curve calculation means 21, a set furnace temperature calculation means 22, and a parameter change calculation means 23 upon operator intervention, and is activated periodically. The current temperature calculation means 20 calculates the current material temperature using the actual furnace temperature based on the material information.

Temperature rise curve calculation 1,000 stages 2L determines the temperature rise curve for each material as described above. The set furnace temperature calculation means 22 instructs the determined furnace temperature to the fuel flow rate controller LO3.

Further, the set furnace temperature correction value obtained by the operator manual means 107 is used to change each parameter in the parameter change calculation means 23, and the temperature rise curve calculation means 21 determines the temperature rise curve using these parameters. [Effects of the Invention] As described above, according to the present invention, two types of slab average temperatures at the skid portion and between the skids are predicted by a temperature prediction formula model, and the slab average temperature sensitivity to furnace temperature is calculated using the prediction formula model. When determining the material temperature rise curve by correcting each zone furnace temperature using the corrected furnace temperature calculation formula, the amount of correction is taken into account when the operator inputs the furnace temperature correction amount, reducing calculation time. It is shortened and suitable for online control of the heating furnace, and has the effect of improving the dimensional accuracy of slab rolling and determining a temperature increase curve that suits the operator's image.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the general structure of a heating furnace, FIG. 2 is a block diagram showing a method of controlling a heating furnace according to an embodiment of the present invention, and FIG. 3 is a material diagram showing a method of controlling a heating furnace according to an embodiment of the present invention. FIG. 4 is a flowchart showing a calculation method for determining a temperature increase curve. FIG. 4 is an explanatory diagram showing a process when the slab charging temperature in a conventional continuous heating furnace is determined based on elapsed time. In the figure, 101 is a heating furnace, and 106 is a furnace temperature setting means. In addition, the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] In a method for determining a material temperature rise curve for a heating furnace, which determines a material temperature rise curve in a heating furnace that has a plurality of control zones and continuously heats and extracts slabs, Two types of slab average temperatures are calculated using a slab temperature prediction formula model, and using the slab average temperature, the slab average temperature sensitivity at the time of extraction for each zone furnace temperature is calculated by the slab average temperature sensitivity formula at the time of extraction, The correction amount of the corrected furnace temperature when is in each zone is determined by the corrected furnace temperature calculation formula, and each zone furnace temperature is corrected, and the operator inputs the furnace temperature correction value during the calculation cycle of the corrected furnace temperature calculation formula. Then, the extraction target temperature correction, target soaking degree correction value, and correction furnace temperature calculation gain are calculated by the parameter calculation formula, and the deviation from the extraction target temperature is corrected and reflected in the next cycle. Temperature curve determination method.