JPH08260055A - Method for controlling furnace temperature of steel heating furnace - Google Patents

Abstract

PURPOSE: To remarkably reduce the calucated value while maintaining such discharging temp. control accuracy as the conventional method, in a furnace temp. control method for continuous type heating furnace. CONSTITUTION: (1) To all the steels in the furnace, a priority order of steels is obtd. from a steel priority table and the steel at the most downstream side having the highest priority is defined as the precedingly heating neck steel to be heated. (2) An ejecting scheduled time Tr of the precedingly heating neck steel to be heated is read out from the ejecting schedule time table and an average T/H THr to Tr is calculated. (3) A target furnace temp. Tfr is obtd. by refering a target furnace temp. table while using THr, the kind of the precedingly heating neck steel to be heated and the target discharging temp. as keys. (4) The Tfr is set to a furnace temp. adjusting meter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace temperature control method for a continuous steel material heating furnace, which is intended to secure a steel material extraction temperature.

[0002]

2. Description of the Related Art In a heating furnace that continuously heats steel materials such as slabs and billets, it is necessary to heat them at a temperature higher than a target extraction temperature determined for each steel type in order to secure quality in a rolling process which is a post process. Is. On the other hand, excessive heating leads to deterioration of the fuel consumption rate and deterioration of quality such as curling of steel materials, so the furnace temperature is controlled in order to secure an appropriate extraction temperature.

Conventionally, as a method for controlling the furnace temperature of these continuous steel material heating furnaces, the temperature of each steel material in the furnace is estimated by utilizing a heat transfer difference equation, and the estimated time from extraction to the extraction time is extracted. After estimating the temperature of each steel material in the furnace by the method of obtaining the furnace temperature required to secure the steel material temperature from the heat transfer equation, and also by using the heat transfer difference equation, the deviation from the ideal heat pattern is determined. The method of compensating with temperature was used.

[0004]

However, all of these methods require a very large amount of calculation because they are premised on the steel material temperature estimation calculation by the heat transfer difference equation. In a typical steel material heating furnace, dozens of steel materials exist in the furnace at the same time in many cases, but for all of these, the heat transfer difference equation is solved in a cycle of 5 to 10 seconds, so a dedicated electronic computer is used. Sometimes needed. In addition, in the operation of a continuous steel heating furnace, in general, due to troubles such as roll replacement and misroll in the rolling process which is a post-process, or tooth loss operation for adjusting the furnace temperature when changing lots, However, in such a case, the accuracy of the steel material temperature estimation calculation deteriorates significantly. Therefore, even with the conventional method that requires a large amount of calculation, it can be applied only when the reactor conditions are stable.

An object of the present invention is to solve the drawbacks of the conventional method, and to provide a furnace temperature control method which greatly reduces the amount of calculation while maintaining the extraction temperature control accuracy comparable to that of the conventional method.

[0006]

According to the present invention, the most heated neck steel of the steel in the furnace is specified from the quality priority of each predetermined steel type, and the hourly average until the scheduled extraction time of the heated neck steel is determined. The extraction amount (hereinafter referred to as average T / H) is calculated, the target furnace temperature is obtained from the average T / H, the steel type of the superheated neck steel material, and the target extraction temperature of the heating neck steel material, and the target furnace temperature is matched. The above problem is solved by controlling the furnace temperature so that

[0007]

The present invention will be described in detail below. First, FIG.
An example of the continuous steel material heating furnace to which the furnace temperature control method of the present invention is applied is shown in FIG. Reference numeral 11 is a steel material to be heated, 12 is a charging table, 13 is an extraction table, and 14 is a steel material conveying device. Further, 15 is a heating burner, and 16a to 16c are furnace thermometers. The steel material inserted from the charging table 12 is conveyed to the furnace outlet by the steel material conveying device 14, and is extracted from the extraction table.
It is extracted by the bull 13 and transported to a rolling line or the like which is a post process.

The heat balance equation in the continuous steel heating furnace shown in FIG. 2 is shown below.

Σα · [Tf (i) ⁴ −Tm (i) ⁴ ] = THo · Tm (n) · Cm−THi · Tm (1) · Cm (1) Fi [Tf (i + 1) , Tf (i)] = Fi-1 [Tf (i), Tf (i-1)] + α ・ [Tf (i) ⁴ −Tm (i) ⁴ ] ＋ Wi ＋ Cfi ・ dTf (i) / dt ・ ・ ・ ( 2) Fn [Tf (n + 1), Tf (n)] = Q ... (3) Fo [f (1), Tf (0)] = 0 ... (4) α: From furnace to steel Heat transfer coefficient Tf (i): furnace temperature at furnace position i Tm (i): steel material temperature at furnace position i THi: charging average T / H THo: extraction average T / H Cm: heat capacity per unit weight of steel material Cfi: Heat capacity of the furnace body at position i in the furnace Fi: Heat transfer amount of the furnace body (including atmospheric gas) from position i + 1 in the furnace to position i in the furnace Wi: Heat dissipation amount of furnace body at position i in the furnace Q: Heating Heating from burner Here, the furnace position i is set to n in accordance with the fixed position of the steel material.
It is divided into zones, where the charging side is 1 and the extraction side is n.

In the steady state, the following equation holds.

Tho = THi (5) dTf (i) / dt = 0 (6) From equations (1) to (6), in the steady state, the average extraction amount per hour, the outlet furnace It can be seen that the extraction temperature is determined by the temperature and steel type. Therefore, the extraction temperature can be secured by determining the target outlet-side furnace temperature from the average T / H, the steel type, and the target extraction temperature, and performing the furnace temperature control with the target outlet-side furnace temperature as the reference value. Further, it is clear that the amount of calculation required to determine the target outlet furnace temperature is significantly smaller than that of the conventional method based on the steel material temperature estimation calculation by the heat transfer equation. As described above, the present invention can provide a furnace temperature control method that can secure the extraction temperature in a steady state with a small amount of calculation.

Next, the characteristics of the furnace temperature control method of the present invention in an unsteady state will be considered. The unsteady states that occur during actual operation include those that can be predicted at the time of charging and those that occur suddenly, so each of these will be considered below.

(1) Unsteady state that can be predicted at the time of charging: The unsteady state that can be predicted at the time of charging includes charging of steel materials having different steel types, charging of steel materials having different target extraction temperatures, scheduled roll replacement, etc. Due to the interruption of the extraction due to the fluctuation of the average T / H. There are two types of these unsteady states, one acting to increase the extraction temperature and the other acting to decrease the extraction temperature. For example, if the extraction is suspended due to roll replacement, etc., even if an attempt is made to control the furnace temperature in a lower direction, the heat capacity of the furnace body is large and there is a time delay in the decrease of the furnace temperature. Exceeds the target extraction temperature.
On the contrary, when the target extraction temperature rises, even if an attempt is made to increase the furnace temperature, there is a time delay in increasing the steel material temperature, and the extraction temperature tends to cause the target extraction temperature crack.

First, in the case of acting to increase the extraction temperature, if the overheating itself has little influence on the quality, and if it is an unsteady state that can be predicted in advance, the furnace temperature is gradually lowered to improve the quality. It is possible to eliminate the above effects.

Regarding the case of acting in the direction of lowering the extraction temperature, there is no problem if the fluctuation range is small and it can be sufficiently absorbed in the time between charging and extraction, but even if it exceeds it, the target The extraction temperature can be secured by forming a steel-free space in front of the material having a high extraction temperature or inserting a warming-up material.

(2) Sudden unsteady state: As the unsteady sudden state, it is conceivable that the average T / H fluctuates due to interruption of extraction due to a trouble in the lower process or the like. In this case, the extraction temperature exceeds the target extraction temperature as at the time of interruption of the extraction for scheduled roll exchange, etc.
There is a possibility that the extraction temperature will rise considerably. However, this cannot be avoided by using any furnace temperature control method.
Rather, the conventional method, which is based on the steel material temperature estimation calculation using the heat transfer difference equation, cannot guarantee the estimated temperature of the steel material in the furnace at the time of the sudden extraction interruption, so that the furnace temperature control cannot be performed normally for a while after that. In comparison, the method of the present invention can be said to be more stable in the sense that the control direction can be guaranteed to some extent.

[0017]

FIG. 3 shows an example of system configuration for realizing the furnace temperature control method of the present invention. Reference numeral 21 denotes an arithmetic unit. The arithmetic unit has a tracking function 22 and a furnace temperature control function 23 according to the present invention inside. Reference numeral 24 is a furnace temperature controller, 25 is a fuel flow rate controller, and 16 is a furnace thermometer. Further, 14 indicates a steel material conveying device. In FIG. 3, the steel material is tracked by the tracking function 22 incorporated in the arithmetic unit 21 in response to a signal indicating that the steel material has been conveyed and a signal indicating that the steel material has been loaded. Further, the furnace temperature control function 23 calculates the target furnace temperature based on the steel material tracking and sets it in the furnace temperature controller 24. The furnace temperature controller 24 controls the furnace temperature by operating the fuel flow rate controller 25.

Next, an outline of the furnace temperature processing by the furnace temperature control function 23 is shown in FIG. 1, and one embodiment of the present invention will be described with reference to FIG.

(1) Specification of the most heated neck steel material (STEP
1) Steel priority table 1 for all steel materials in the furnace
Therefore, the steel material priority is obtained, and the steel material on the most downstream side among the steel materials having the highest priority is set as the most heated neck steel material.

(2) Calculation of average T / H until the scheduled extraction time of the hottest neck steel material (STEP 2) The scheduled extraction time Tr of the hottest neck steel material is extracted from the scheduled extraction time table 2 and calculated by the following formula until Tr. Calculate the average T / H THr: THr = ΣMi / (Tr-Tc) Tc: Current time Mi: Steel material weight The subscript i indicates all steel materials from the most downstream steel material to the most heated neck steel material. If there is a tooth missing part in the steel material arrangement, the weight is added assuming that the tooth missing part is also filled with the same steel material as the steel material located upstream thereof. The weight of the connecting material is also added assuming that it is the same steel material as the steel material located on the upstream side.

The expected extraction time table 2 is preliminarily calculated from the expected extraction pitch of each steel material, the extraction interruption schedule due to the roll change in the post-process, the expected recovery time of the unexpected extraction interruption due to a trouble, etc. It should be calculated for all steel materials.

(3) Calculation of target furnace temperature (STEP 3) Keys THr, steel type of the most heated neck steel, and target extraction temperature.
Then, the target furnace temperature Tfr 3 is obtained by referring to the target furnace temperature table 3.

(4) Setting of target furnace temperature (STEP 4) Tfr is set in the furnace temperature controller.

[0024]

By using the furnace temperature control method of the present invention, while maintaining the extraction temperature control accuracy comparable to the conventional method,
It is possible to greatly reduce the calculation amount.

[Brief description of drawings]

FIG. 1 is a flowchart showing the contents of furnace temperature control according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing an example of a continuous steel material heating furnace to which the furnace temperature control method of the present invention is applied.

FIG. 3 is a block diagram showing a system configuration for realizing the furnace temperature control method of the present invention.

[Explanation of symbols]

1: Steel material priority table 2: Extraction scheduled time table 3: Target furnace temperature table 11: Steel material to be heated 12: Charging table 13: Extraction table 14: Steel material conveying device 15: Heating burner 16, 16a to 16c: Furnace thermometer 21: Computing device 22: Tracking function 23: Furnace temperature control function according to the present invention 24: Furnace temperature controller 25: Fuel flow controller

Claims (1)

[Claims] 1. In a furnace temperature control method for a continuous steel material heating furnace, the most heated neck steel material among the steel materials in the furnace is specified from a predetermined quality priority for each steel type, until the scheduled extraction time of the most heated neck steel material. Of the steel material heating furnace, wherein an average extraction amount per hour is calculated, and a target furnace temperature is obtained from the average extraction amount per hour, the steel type of the most heated neck steel material, and the target extraction temperature of the heating neck steel material. Temperature control method.