JPS63282211A - Method for controlling furnace temperature in continuous heating furnace - Google Patents

Abstract

PURPOSE:To reduce the heat energy loss of a heating furnace by means of the optimum pitch of extraction, by setting up respective extraction times of steel stocks from a heating furnace and also by setting up furnace temps. from respective temps. of the steel stocks in the heating furnace, respective lengths of time required for the extraction of the steel stocks, and the desired temp. of extraction. CONSTITUTION:Steel stocks 51 are heated in a heating furnace 31 until the desired temp. is obtd., and then extracted at a pitch corresponding to the rolling line cycle time from a piercer 32 on the downstream side to a stretch reducer 35. In the above- mentioned continuous heating furnace 31, respective extraction times of the steel stocks 51 from the heating furnace 31 are set up by means of an industrial control computer 11, and an extraction cycle time controller 12 is controlled. At the same time, by means of the above computer 11, furnace temps. in respective zones in the heating furnace 31 are set up from the respective temps. of the steel stocks 51 in the heating furnace 31, respective lengths of time required for the extraction of the steel stocks 51 from the heating furnace 31, and the desired temp. of the steel stocks 51 to be extracted from the heating furnace 31. Respective combustion equipments 42 are controlled via furnace temp. controllers 13 based on the above-mentioned set values.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a furnace temperature control method for a continuous heating furnace that is arranged in the L flow of a hot rolling line and heats steel materials.

[Advanced technology] A heating furnace is placed at the most upstream of the steel hot rolling line.
Red-hot steel passes through each rolling mill downstream of the line and becomes a product.For example, in a rolling line for seamless steel pipes, a piercing rolling mill (hereinafter referred to as a piercer) and an elongating rolling mill (hereinafter referred to as a piercer) and a stretching mill ( A mandrel) and a reducing mill (stretch reducer) are installed, or a piercer is installed.
, elongator, plug mill, reeling mill and sizing mill are installed.

In the above-mentioned hot rolling line, the method of determining the optimum extraction cycle time of the heating furnace in accordance with the cycle time of the rolling mill has already been proposed by the present applicant in Japanese Patent Application No.
It was proposed in No. 5073.

On the other hand, many control technologies for heating furnaces have been proposed. For example, in Japanese Patent Publication No. 58-25731, the temperature at representative positions in the furnace is determined in a heating pattern using the furnace time as a parameter for multiple steel types. The furnace temperature is set based on this calculation. In addition, the special public
JP-A-53848 discloses a furnace temperature control method when a downstream rolling line is temporarily stopped.

[Problems to be Solved by the Invention] However, Japanese Patent Application No. 60-285073 assumes that the extraction temperature of the steel material from the heating furnace is an appropriate temperature.
It defines the optimum cycle time for supplying steel materials from the heating furnace to the rolling mill line, but does not mention the furnace temperature control of the heating furnace corresponding to this optimum cycle time. Special Public Service 1977-
Although the conventional heating furnace control method described in Japanese Patent No. 53848 is excellent in terms of control accuracy and energy saving, it does not take into account the balance with the rolling line.

To explain in more detail, the cycle time of a rolling line varies greatly depending on the steel loft, and especially when processing small lots continuously, it is necessary to take into account the downtime between lofts, so the temperature increase pattern must be determined in advance. Conventional methods of setting cannot accommodate cycle time fluctuations in rolling lines.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a method for controlling a heating furnace with less thermal energy loss while maintaining the optimum extraction cycle time of the heating furnace in accordance with the cycle time of the rolling line. do.

[Means for Solving the Problems] The present invention is arranged upstream of a hot rolling line to heat the steel material, and extracts the steel material heated to a target temperature at an extraction pitch corresponding to the downstream rolling line cycle time. A furnace temperature control method for a continuous heating furnace that enables setting the extraction time of each steel material from the heating furnace, and setting the temperature of each steel material in the heating furnace and the time until it is extracted from the heating furnace; The furnace temperature of each zone of the heating furnace is set based on the target temperature of each steel material extracted from the heating furnace.

[Function] According to the present invention, the furnace temperature of each zone of the heating furnace is adjusted so that the extraction temperature of each steel material from the heating furnace matches the target temperature under the conditions that determine the extraction time of each steel material from the heating furnace. It is determined. Therefore, even when the cycle time of the rolling line fluctuates, by adapting the extraction pitch of the heating furnace to the cycle time of the rolling line and controlling the furnace temperature of the heating furnace in accordance with the extraction pitch, the temperature of the heating furnace can be increased. Energy loss can be prevented.

[Example code] FIG. 1 is a schematic diagram showing the control system of the present invention.

That is, the present invention is carried out by an industrial control computer 11, an extraction cycle time control device 12, a furnace temperature control device 13, and a transmission device 14 that connects the industrial control computer 11 and each control device 5m12.13. Ru.

The industrial control computer 11 includes a cycle time calculating section 1 of a rolling mill/processing machine, a steel material grasping section 2 that grasps the position and type of steel on all rolling lines in real time, and a steel material grasping section 2 that calculates the temperature of steel in the heating furnace. A temperature calculation unit 3, a steel material temperature prediction unit 4 that predicts the temperature of the steel in the heating furnace at each hour until it is extracted, a soaking zone furnace cycle time setting unit 5, and a heating zone furnace cycle time setting unit 6. , an extraction cycle time setting section 7, and a heating furnace temperature setting section 8, and an operating system 21 that orders the operations of the respective sections 1 to 8 and exchanges information.

The operations of the above-mentioned sections 1 to 8 of the industrial control computer 11 are as follows.

The cycle time calculating section 1 of the rolling mill/processing machine uses the steel material grasping section 2, which grasps the position and type of steel material on all rolling lines in real time, to calculate the loft of the steel material on the line, the steel type of the steel material,
Receiving information such as length, weight, shape, rolling or processing conditions, etc., calculates the rolling time and processing time required for each rolling mill/processing machine for each loft 0 For example, ■r: rolling speed, LS
: Length of steel material, kl, 2: constant, D: roll diameter of rolling mill, N: roll rotation speed of rolling mill, rolling time τ
is τ=kl*Ls/Vr, Vr=2 eD
-N can be calculated.

The steel material grasping unit 2, which grasps the position and type of steel materials on all rolling lines in real time, uses the steel material tracking unit possessed by the industrial control computer 11 to check the current status of steel materials on all rolling lines including the inside of the heating furnace. The position and funnel of each steel material, steel type, length, weight, shape, rolling or processing conditions, rolling/processing history up to the present, etc. are grasped in real time as the situation changes. Here, the industrial control computer 11
Tracking of steel products is carried out by logically determining the cause-and-effect relationship of detection signals from means (sensors, etc.) placed throughout the rolling line to detect whether or not steel products are present at that location. It is assumed that information such as the loft, steel type, length, weight, etc. of each steel material to be carried into the line has been input in advance.

Steel temperature calculation unit 3 that estimates and calculates the steel temperature in the heating furnace
The system learns the current position, steel type, length, and shape of the steel in the furnace from the steel material grasping section 2, which grasps the location and type of steel on all rolling lines in real time, and the current furnace temperature from the furnace temperature control device 13. For example, the method of estimation calculation, in which the temperature of the steel material in the furnace is estimated for each unit time, is
This is carried out using the well-known difference method or finite element method, as described in Japanese Patent Publication No.-53848 and Japanese Patent Publication No. 81-1484.

The steel material temperature prediction section 4 calculates the temperature of the steel material for each unit time between the current temperature of the steel material obtained by the steel material temperature calculation section 3 which calculates the temperature of the steel material in the heating furnace and the future time required for prediction. By predicting and calculating the position in the furnace, predicting and calculating the steel material temperature for each unit time during the future time until extraction.
The predicted position calculation assumes the in-furnace transfer cycle time,
It is determined from the moving distance per cycle time and the time required for changing the rolling mill/processing machine between multiple lofts. The travel distance and set-up time per cycle time can be calculated from information held by the steel material grasping section 2, which grasps the positions and types of steel materials on all rolling lines in real time. The in-furnace transfer cycle time assumed here is:
This value is a candidate value for the heating zone furnace cycle time when the prediction range targets steel materials existing in the heating zone, and for the soaking zone furnace cycle time when the prediction range targets steel materials existing in the soaking zone. The temperature prediction calculation is performed using the same method as the steel material temperature calculating section 3 that calculates the steel material temperature in the heating furnace or a simplified method.

The soaking furnace cycle time setting section 5 is a steel material temperature prediction section 4.
The predicted value of the temperature of the steel material at the extraction position obtained by The minimum in-furnace transfer cycle time at which the heating furnace extraction reference temperature is reached is determined, and this is defined as the soaking zone furnace cycle time. The heating furnace extraction reference temperature can be calculated from information held by the steel material grasping section 2 that grasps the location and type of steel materials on all rolling lines in real time.

The heating zone furnace cycle time setting section 6 is connected to the steel material temperature prediction section 4.
The predicted value of the steel material temperature at the heating zone exit position obtained by the method is compared with the heating belt exit reference temperature, and the steel material temperature at the heating zone exit position of the steel material existing in the heating zone is determined by adjusting the in-furnace conveyance cycle time of the steel material. The minimum in-furnace conveyance cycle time at which the predicted value reaches the heating zone exit reference temperature is determined, and this is defined as the heating zone furnace cycle time. The heating zone outlet reference temperature can be calculated from information held by the steel material grasping section 2 that grasps the position and type of steel materials on all rolling lines in real time.

The extraction cycle time setting section 7 includes a rolling mill/processing machine cycle time calculation section 1, a steel material grasping section 2 that grasps the position and type of steel on all rolling lines in real time, a soaking furnace cycle time setting section 5, and a heating zone. Furnace cycle time setting section 6
This function calculates the extraction cycle time from the results.

This determines the extraction cycle time based on the method of Japanese Patent Application No. 80-285073. However, the cycle time of the heating furnace shall be the greater of the heating zone furnace cycle time and the soaking zone furnace cycle time. That is, for each loft of the steel material, the arrival time from the heating furnace to the entry side of each rolling mill/processing machine and the arrival time to the exit side are calculated based on the cycle time calculation unit 1 of the rolling mill/processing machine and the position of the steel material on all rolling lines. It is calculated by determining the rolling time/processing time and transport time using the steel material grasping section 2 that grasps the type in real time. Then, the arrival time of the next extracted steel material to the entry side of each rolling mill/processing machine is equal to or greater, and the arrival time of the next extracted steel material is equivalent to the arrival time of the above-mentioned next extracted steel material with respect to one or more rolling mills/processing machines. The larger value of the mill cycle time and the cycle time of the heating furnace is determined as the extraction cycle time. Then, this value is input to the operating system 2 of the industrial control computer 11.
1 and transmission device 14 to the extraction cycle time control device 12.

The furnace temperature setting section 8 of the heating furnace determines the temperature of the heating zone based on the functions obtained by partially modifying the soaking zone furnace cycle time setting section 5 and the heating zone furnace cycle time setting section 6 and the mill cycle time determined by the extraction cycle time setting section 7. Find the furnace temperature set value and soaking zone furnace temperature set value. In other words, the furnace temperature set value in the soaking zone is determined by the soaking zone furnace cycle time setting section 5, which calculates the extraction cycle time based on the current actual furnace temperature. The function is changed to a function that fixes the time to match, adjusts the soaking zone furnace temperature set value, and calculates the set value that is the minimum setting. In this function, the furnace temperature, which is a known parameter in the soaking zone furnace cycle time setting section 5, is used as an unknown parameter, and the in-furnace transfer cycle time, which is an unknown parameter, is used as a known parameter. Further, the heating zone furnace temperature set value is determined by the heating zone furnace cycle time setting section 6, which calculates the heating zone furnace cycle time based on the current actual furnace temperature. The in-furnace conveyance cycle time is fixed to match the soaking zone furnace cycle time, the heating zone furnace temperature set value is adjusted, and the function is changed to find the set value that is the minimum setting to find the set value. In this function, the furnace temperature, which is a known parameter in the heating zone furnace cycle time setting section 6, is used as an unknown parameter, and the in-furnace conveyance cycle time, which is an unknown parameter, is used as a known parameter.

Here, as is well known, when the furnace temperature set value is changed, the furnace temperature does not immediately match the set value, and it takes time for it to match. When the above-mentioned furnace temperature set value is given, if you directly replace it with the furnace temperature, you are ignoring this fact, so the furnace temperature θ(1) required for calculation is, for example, the furnace temperature set value. θs@t, elapsed time t since setting change,
From the furnace load M, θ(t) = f (θset, M, t)
I will give it to you. The heating zone furnace temperature set value and soaking zone furnace temperature set value thus determined are calculated using the industrial control calculation file.
It is transmitted to the furnace temperature control device 13 via the operating system 21 and the transmission device 14.

An embodiment in which the present invention is applied to a seamless steel pipe manufacturing line shown in FIG. 2 will be described below. In FIG. 2, 31 is a heating furnace, 32 is a piercer, 133 is a mandrel mill, 34 is a reheating furnace, and 35 is a stretch reducer. That is, a heating furnace (rotary hearth type steel material heating furnace) 31 is installed at the beginning of the manufacturing process, and the steel material 51 is heated thereby. As shown in FIG. 3, this heating furnace is composed of five zones, with zones 1 to 3 serving as heating zones, and zone 4.5 serving as a soaking zone. A thermocouple 41 is installed in the 4th zone to measure the furnace temperature in the 4th zone, and the furnace temperature control wave N13 in the 4th zone is calculated by the industrial control computer 11 based on the method described above via the transmission device 14. The combustion amount of the combustion devices 42 installed in four zones is controlled so that the set furnace temperature is achieved. The measured furnace temperature is transmitted to the industrial control computer 11 via the transmission device M14.

The steel materials used to make seamless steel pipes vary depending on the steel type, dimensions, and length of the product, and these are grouped together as lofts. As shown in Figure 3, steel materials 51 of lots A, B, . . . , F are being heated in the heating furnace, and lot A is being rolled in the rolling line.

At this time, the cycle time of the rolling mill and processing machine of A lot is τ, the current heating zone furnace cycle time is +s, A τ =■a direct, , τ), the soaking zone furnace is
hl h2 h3 time is τ =
■Suppose that aX(τ τ ) is s s4
In this case, the extraction pitch is determined as ■aX (with τmA'h') according to Japanese Patent Application No. 80-285073, and this value is sent to the extraction cycle time control device 12 via the transmission device ff114 (τ , is the heating zone furnace cycle time of the i zone, i = 1.2, 3. τ is the soaking zone furnace cycle time of the j zone, j = 4.5.), the extraction cycle, and the time control device 12 is: The hearth drive device 43 and the steel extraction device 44 are operated at this pitch.

Under these circumstances, the furnace temperature setting value θ, (
i=1. ..., 5) are determined as follows according to the present invention. Now in the 5th zone there are n lots of A, BA, 50 feet are n trees, in the 4th zone there are n B lots, 4B, 5 trees, n of C rows, and in the 3rd zone there are D lots of C. ,4 nD, 3 lines, 2 bands have n E lots, E, 2 lines, and l band have n F lots.For simplicity, each i band's output F,
1. Let the side radical temperature be θrk (k = 1..., 5) (Originally, θ varies depending on the funnel), and here, the time t until the final material in the 5th zone is extracted is , the furnace position is determined by τm, A by the cycle time calculation unit 1 of the rolling mill/processing machine.
+s, B' and stoppage time between lots A and B,
τ? From A-B・Time”” nA, 5 m, A
In the A-B contest, + τ + nB, 5 m, B is found, and the average value is t/(
It is found as nA, 5 B, 5) (in Mi).

” Compare M, 5 τM, 5 and the current layer ax (τ, τ) (= τF), and if τ 〉, then 5 etc. Furnace temperature setting M, 5 value will be heated from now on Cycle time τ of the rolling line for steel materials extracted from the furnace and existing in 5 zones that become materials after the heating furnace
is the soaking furnace cycle time M of 5 zones, 5 mm τ, and the steel material present in 5 zones is extracted with this τ, s, 5
0 and 5 are determined so that g, 5 0 satisfies θ. At this time τM
, 5 becomes 3.5. On the other hand, τ is τF=”
If M, 5, do the same and θ
However, there is a case where the result of this calculation, s,5, exceeds the maximum allowable furnace temperature setting.In this case, θ is the maximum furnace temperature setting, and s,5 is the furnace temperature. Let τ be the cycle time r,5 at which the temperature of all the steel materials in the 5 bands exceeds θ at the extraction port.At this time, τ becomes τ, and s,5
M, 5 g, 5 line balance will inevitably collapse.

Below, the 4-zone furnace temperature setting value is ■ax(τM, 5 g,
5), τ3. ．． Find the furnace temperature setting so that the values match.

That is, the extraction pitch is WaX(τM, 5 g,
5), when τ is assumed, the temperature of all four quasi-existing steel materials is θ at the exit side of the four bands.
Find θ that satisfies the above. The result of this calculation is r, 4
g, 4 When the temperature exceeds the maximum allowable furnace temperature setting value, θ is the maximum furnace temperature setting value, θ is the furnace temperature, and s, 4
τ is the cycle time at which the temperature of the steel material of all 4 bands becomes θ or higher at the exit side of 4 bands when g and 4 are reached.
shall be.

r, 4 g, 43 band~
Wax (τ, 5g, 5.

τs, 4 h, 3 ma""M, 5 s, 5 s, 4 h, 3
) and 7h, 2, τ, τ
, τ match, in one band, 1lIaX((H,
5s, 5.

, τ , τ , τ ) and τ match, τg, 4
h, 3 h, 2 h, 1 similar θ, θ
, find θ.

s, 3 s, 2 g, 1 Here, as an example, the furnace temperature setting method will be explained in more detail in the case of 4 zones. τ3,4 = +5ax(τM
, 5 s, 5), and so on, for example.
τ The final steel material of the 4th zone has nB,
5 g, 4 B-C" nc @"s, 4 times are taken at φ τ + , τ is the time occurring between B and C between −C. At this time, assuming that the steel material has a furnace temperature θ, the temperature at the exit side of the 4th zone can be predicted and calculated, and it can be determined whether it is higher than θ. The same thing was done for all the steel materials in the 4 bands, and the furnace temperature θ was fixed r so that θ was satisfied.
g, 4 Melt. If the result is that θ is higher than the allowable furnace temperature setting j value for the four zones, then set θ to the maximum value s,
4, and this time, find a line r and a time τ such that all the steel materials in the four zones reach a temperature of θ or higher when heated at that furnace temperature.

s, 4 The industrial control computer 11 performs the above furnace temperature setting method at regular intervals (here, every 3 minutes) and outputs the set value.

Figure 4 shows an example of a comparison of the temperature rise of steel materials using this furnace temperature setting method and the conventional manual setting by the operator.This is for a billet with a diameter of 175φ and a length of 2.5m. Although the results vary considerably depending on the lot conditions in the furnace, overall energy savings are achieved because heating is performed at a later stage compared to manually setting the furnace temperature. Furthermore, as shown in Table 1, the furnace temperature is now set lower than before. Fuel costs also fell by about 4%.

As mentioned above, the furnace temperature setting method according to the present invention determines the furnace temperature according to the takt time of the processing machines and rolling mills after the heating furnace, so it is easy to balance the line including the heating furnace.
In general, line balancing in the manufacturing process is said to be the key to maximizing production efficiency and reducing energy loss due to waiting time and the like. In this sense, the method of the present invention can be said to be an unprecedented furnace temperature setting method that minimizes energy loss without lowering production efficiency.

[Effects of the Invention] As described above, according to the present invention, the extraction pitch of the heating furnace is adapted to the cycle time of the rolling line, and the furnace temperature of the heating furnace is controlled in accordance with the extraction pitch. Heat energy loss in the furnace can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the control system of the present invention, Fig. 2 is a schematic diagram showing a seamless steel pipe production line, Fig. 3 is a control system diagram showing a furnace temperature control system for a heating furnace, and Fig. 4 is a schematic diagram showing a steel pipe manufacturing line. It is a diagram showing a temperature rising state. 11... Industrial control computer, 12... Extraction cycle time control device, 13... Furnace temperature control device. Agent Patent Attorney Osamu Shiokawa Jiryou 1 1st session

Claims (1)

[Claims] (1) Furnace temperature control of a continuous heating furnace that is placed upstream of the hot rolling line to heat the steel material and allows the steel material heated to a target temperature to be extracted at an extraction pitch that corresponds to the downstream rolling line cycle time. The method includes setting the extraction time of each steel material from the heating furnace, the temperature of each steel material in the heating furnace, the time until it is extracted from the heating furnace, and the target temperature of each steel material extracted from the heating furnace. A furnace temperature control method for a continuous heating furnace characterized by setting the furnace temperature of each zone of the heating furnace.