JP2006274401A - Method for automatically controlling combustion in continuous heating furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for automatically controlling combustion in a continuous heating furnace with which in the case of heating a plurality of steel materials having different states of size, kind of steel, etc., the atmospheric temperature in the furnace can smoothly and suitably be controlled without lowering the operating efficiency and the steel material can be heated at high precision to the target extruding temperature. <P>SOLUTION: When the plurality of the steel materials having different states of size, kind of steel, etc., are continuously heated with the continuous heating furnace, in which each zone can independently be controlled to the furnace temperature, respectively; a weighting factor in each steel material is obtained according to charging temperature into the heating furnace, thickness, position in the furnace and kind of steel, and the atmospheric temperature in the furnace is calculated by using the obtained weighting factor to control this temperature, and thus, each steel material is stably heated to the target extruding temperature. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an automatic combustion control method for a continuous heating furnace capable of efficiently heating a steel material such as a plurality of slabs having different states such as size and steel type to an optimum temperature in a continuous heating furnace. It is.

  In a continuous heating furnace, steel materials such as a plurality of slabs charged in the furnace sequentially pass through the pre-tropical zone, heating zone and soaking zone, and in the meantime, reach the target extraction temperature at the heating furnace extraction port. Heated. When continuously heating a plurality of steel materials in such a continuous heating furnace, if the sizes and types of the steel materials are different, each steel material must be heated according to the heating conditions adapted to the state. Don't be.

  Conventionally, many methods have been proposed as means for efficiently heating the plurality of steel materials described above to the target extraction temperature. For example, in Patent Document 1, in a continuous heating furnace in which a plurality of steel materials having different heating conditions are heated in the same furnace and each zone can independently control the furnace temperature, the soaking temperature of the steel materials in the furnace is set. The continuous heating furnace is set to be equal to or higher than the soaking temperature average value of each steel material before and after the steel material, and the soaking time of the steel material is set to be equal to or higher than the average temperature equalizing time of each steel material before and after the steel material. An automatic combustion control method is disclosed.

In addition, Patent Document 2 includes an evaluation item including an evaluation term for a weighted sum relating to the square of the deviation between the slab future temperature and the slab future target temperature for each slab at every control time from the present to a predetermined time in the future. In the heating temperature control method for a continuous heating furnace that calculates the furnace temperature setting value so as to minimize the function, the weight distribution given to each slab is the thickness of the preceding slab and the subsequent slab in the same heating furnace. , A method of determining based on the width, the steel type, the extraction target temperature, the charging temperature, and the predicted in-furnace time is disclosed.
JP 7-11347 A Japanese Patent Laid-Open No. 11-335739

  In the method described in Patent Document 1, in order to secure the heating time of the steel material in the heating furnace, the extraction pitch of the steel material from the heating furnace is limited. As a result, the heating furnace becomes a neck process, and the operation efficiency decreases. Problems arise.

  In the method described in Patent Document 2, the weight distribution to be given to each slab is determined based on the slab thickness, width, steel type, extraction target temperature, charging temperature, and predicted presence of the preceding slab and the succeeding slab in the same heating furnace. It is determined based on the furnace time, and there are many types of weighting factors. As a result, the automatic control of the heating temperature cannot be performed smoothly, and the number of times the operator intervenes and controls increases due to the occurrence of trouble, and the intended priority order cannot be achieved.

  Therefore, the object of the present invention is to solve the above-described problems, and when a plurality of steel materials having different sizes and types of steel are heated in a continuous heating furnace, the steel material extraction pitch from the heating furnace is limited, and the heating furnace However, there is no problem that the operation efficiency is reduced due to the bottleneck process, and the automatic control of the heating temperature is smoothed by setting the optimum atmosphere temperature for each slab because there are many types of weighting factors. It is possible to automatically and smoothly control the atmosphere temperature in the heating furnace without causing problems that are difficult to carry out, and to match the steel material to the target extraction temperature from the heating furnace with high accuracy. It is an object of the present invention to provide an automatic combustion control method for a continuous heating furnace that can be heated.

  The automatic combustion control method for a continuous heating furnace according to the first aspect of the present invention is a method for continuously heating a plurality of steel materials having different sizes and types of steel in a continuous heating furnace in which each band can independently control the furnace temperature. The weighting factor for each steel material is calculated according to the heating furnace charging temperature, thickness, furnace position and steel type of each steel material, and the furnace temperature inside the furnace is calculated and controlled using the obtained weighting factor. Thus, each steel material is stably heated to a target extraction temperature.

The automatic combustion control method for the continuous heating furnace of the second invention is the method described in the first invention, wherein the optimum function temperature (J) of the steel material is calculated based on the weight coefficient when calculating the optimum temperature of the heating furnace. (1) It calculates by the type | formula, It is characterized by the above-mentioned.

  According to the method of the present invention, even when the sizes and types of steel materials to be heated are different, the steel material extraction pitch from the heating furnace is limited, the heating furnace becomes a neck process, and the operation efficiency is reduced. By controlling the heating temperature using the minimum necessary weight coefficient, the atmospheric temperature inside the heating furnace can be automatically and smoothly controlled without any trouble, and the quality of steel can be made uniform. There is an advantage that it can be realized.

  Hereinafter, the control method of the present invention in the case of continuously heating a plurality of slabs having different sizes and types of steel as a steel material in a continuous heating furnace will be described. In order to heat the slab so as to satisfy the target extraction temperature from the heating furnace in a continuous heating furnace consisting of a pre-tropical zone, a heating zone, and a soaking zone, each of which can be controlled independently, The optimum furnace atmosphere temperature must be calculated.

  In order to satisfy the target extraction temperature, it is easy to calculate the optimum set atmosphere temperature for each slab by a computer, but in the case of multiple slabs with different sizes, steel types, etc., it differs for each slab It is necessary to set the optimum set ambient temperature. Therefore, it is difficult to calculate an optimum atmospheric temperature for all slabs staying in the continuous heating furnace in which only one atmospheric temperature can be set in each band.

  Therefore, in the present invention, the current furnace atmosphere temperature necessary to satisfy the target extraction temperature is calculated for each slab located in each of the pre-tropical zone, heating zone, and soaking zone where the furnace temperature can be controlled independently. Then, the optimum atmospheric temperature of each band is calculated and set by multiplying and averaging the weighting coefficient for each slab determined by the state of the heated slab.

In calculating the optimum atmospheric temperature, the slabs in the heating furnace are set as S1, S2,. By calculating the furnace temperature at which the obtained evaluation function (J) is minimized, it is possible to obtain the optimum set ambient temperature of the zone in which all slabs staying in the zone are close to the target extraction temperature on average. it can.

  In the present invention, the weight coefficient Wi for the slab Si in the above equation is calculated by four factors of the slab heating furnace charging temperature, the slab thickness, the slab furnace position, and the slab steel type. The reason why the calculation of the weighting coefficient Wi for the slab is limited to the above four factors in the present invention will be described below.

  Slab heating furnace charging temperature: Slabs with a lower charging temperature in the furnace require more time to be baked, and if the slab does not burn, the slab in the furnace cannot be extracted. Therefore, it is necessary to set the furnace temperature giving priority to a slab having a low charging temperature into the furnace.

  Slab thickness: The thicker the slab, the longer it takes to bake. If the slab does not burn, the slab in the furnace cannot be extracted. Therefore, it is necessary to set the furnace temperature with priority given to the thick slab charged in the furnace.

  Slab furnace position: In the heating furnace, when the position of the slab in each band is close to the exit side, the slab is immediately sent to the next band, so even if priority is given to the slab, it is not in time. Further, when the position of the slab is close to the entry side of each band, the in-furnace time is the longest among the slabs existing in the band, and therefore it is not necessary to give priority to the slab. Therefore, it is necessary to reduce the priority coefficient for the slabs located near the entry side and the exit side of each band, and increase the priority coefficient for the slabs located in the center of each band.

  Steel type of slab: A slab whose material is greatly affected by the heating temperature needs to be preferentially baked to the target temperature, so its priority coefficient needs to be increased.

  In the present invention, the weighting coefficient for the slab is limited to the above four factors, and in calculating the furnace atmosphere temperature, an appropriate target furnace temperature cannot be set unless the above four factors are taken into consideration. On the other hand, if another factor other than the above four factors is added to the weighting factor, the degree of influence due to the four factors is reduced, so that it becomes impossible to set an appropriate target furnace temperature.

  FIG. 1 is a graph showing the difference between the actual product extraction temperature and the target extraction temperature, that is, the accuracy of the slab extraction temperature when automatic combustion control of a continuous heating furnace is performed using a computer according to the method of the present invention. . As shown in the drawing, as a result of examining slabs having a number (N) of 1243, the average value (ave) of the difference between the actual product extraction temperature and the target extraction temperature is only 0.4 ° C., and the deviation (σ) is 10 It is clear that the accuracy of the slab extraction temperature by the method of the present invention is very high.

  FIG. 2 is a graph showing the difference between the actual product extraction temperature and the target extraction temperature, that is, the accuracy of the slab extraction temperature when combustion control is performed without using a computer. As shown in the drawing, as a result of examining slabs having a number (N) of 2,919, the average value (ave) of the difference between the actual product extraction temperature and the target extraction temperature is 6.3 ° C., and the deviation (σ) is 16. The extraction temperature accuracy of the slab was low at 4 ° C.

  In addition, when the four factors of the slab heating furnace charging temperature, slab thickness, slab furnace position, and slab type are not used as the weighting coefficient for the slab, automatic control of the heating furnace is smoothly performed. The frequency of operator intervention was high at about 70%. On the other hand, when the above four factors were used as the weighting factor by the method of the present invention, the operator intervention frequency was reduced to about 5%.

  The method of the present invention can be applied to heating furnace automatic combustion control when various steel materials such as slabs and billets having different states such as size and steel type are heated in the pre-tropics, heating zones, and soaking zones of continuous heating furnaces. .

The graph which shows an example of the slab extraction temperature precision at the time of implementing the automatic combustion control of a continuous heating furnace using the computer by the method of this invention Graph showing the accuracy of slab extraction temperature when combustion control of a continuous heating furnace is carried out without using a computer

Claims (2)

When continuously heating a plurality of steel materials of different sizes, steel types, etc., in a continuous heating furnace in which each belt can independently control the furnace temperature, the heating furnace charging temperature, thickness, and position in the furnace of each steel material And by calculating the weighting factor for each steel material by the steel type and calculating the atmospheric temperature in the furnace using the obtained weighting factor and controlling it, each steel material is stably heated to the target extraction temperature An automatic combustion control method for a continuous heating furnace. The continuous heating furnace according to claim 1, wherein when calculating the optimum furnace atmosphere temperature of the heating furnace, the evaluation function (J) of the steel material is calculated by the following formula (1) based on the weighting factor. Automatic combustion control method.

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