JP2008114266A - Method for controlling heating of continuously heating furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling heating of a continuous heating furnace, which can properly set a heating pattern corresponding to an operation mode required and is applied for a continuous heating furnace arranged in a hot rolling line. <P>SOLUTION: A table of a temperature rise amount in a soaking zone is beforehand prepared according to operation modes, in which one operation mode gives priority to production efficiency and another operation mode gives priority to heat efficiency. When either of the two operation modes is determined according to the production load of a hot rolling line, a corresponding temperature rise amount in a soaking zone is selected from the table of a temperature rise amount in a soaking zone, and a heating pattern is set based on the temperature rise amount in a soaking zone. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating control method for a continuous heating furnace installed in a hot rolling line for hot rolling a steel slab to produce a hot rolled steel sheet (steel strip).

  In operating the continuous heating furnace installed in the hot rolling line, it is very important to operate the heating pattern of the steel slab.

For example, as shown in Patent Document 1, as a heating pattern of a steel slab, a heating pattern of the first stage high load type in which rapid heating is performed in a rapid heating zone and soaking is performed at a low temperature of 1100 ° C. or less in a soaking zone. Thus, there is a technique for improving productivity and improving the heating unit while reducing the skid mark and securing the scale-off amount.
JP 11-256235 A

  However, continuous heating furnaces require high production efficiency (operating configuration with priority on production efficiency) and reduction of heat intensity (depending on the target production volume (production load) of the hot rolling line) There is an operation form that gives priority to heat intensity. In order to achieve a high production efficiency, it is necessary not only to shorten the in-furnace time in the heating furnace but also to consider the productivity in the subsequent hot rolling process. In the heating pattern as described in Patent Document 1, it is possible to shorten the in-furnace time by using low-temperature heating and improve the productivity in the heating furnace, but hot rolling due to low-temperature heating. Problems such as an increase in the number of rough rolling passes due to an increase in deformation resistance may occur in the process, and as a result, the production efficiency of the hot rolling line may not be improved. In addition, low temperature heating below 1100 ° C may not be possible due to material properties that require solid solution strengthening and precipitation strengthening during the heating process. In such a case, heating to the extraction target temperature at once in the rapid heating zone After that, since the time for holding at a high temperature becomes longer, the heat intensity becomes worse.

  This invention is made | formed in view of the above situations, and as a heating control method of the continuous heating furnace installed in the hot rolling line, a heating pattern is appropriately set according to the required operation mode. An object of the present invention is to provide a heating control method for a continuous heating furnace.

  The inventors have intensively studied to solve the above-mentioned problems, and as a result, have found that the temperature rise in the soaking zone in the continuous heating furnace may be set appropriately.

  That is, first, in the case of an operation mode in which production efficiency is given priority, it is necessary to improve rolling efficiency, and for that purpose, it is important to heat so that the amount of skid mark generated in the heating furnace becomes small. This is because if the skid mark amount is large, there is a large difference in deformation resistance between the skid mark part and the non-skid mark part, so that the load during finish rolling fluctuates greatly, making it very difficult to pass through the finishing mill. . As a result, in order to avoid finishing plate troubles, it is necessary to increase the rolling interval between materials, and the rolling efficiency deteriorates. And, in order to reduce the skid mark amount, the present inventors are advantageous in that it is advantageous to reduce the temperature rise in the soaking zone by rapid heating in the heating zone, and the optimum temperature rise amount is It has been found that it varies depending on the steel type, charging temperature, and extraction temperature.

  On the other hand, in the case of an operation mode that prioritizes heat intensity, a heating pattern that avoids rapid heating, keeps the soaking temperature as large as possible, and shortens the holding time at the extraction temperature as much as possible. I found a good thing.

  Based on the above findings, the present invention has the following features.

  [1] A heating control method for a continuous heating furnace installed in a hot rolling line and equipped with a heating zone and a soaking zone, which is operated in advance between an operation mode that prioritizes production efficiency and an operation mode that prioritizes heat intensity. The temperature rise in the soaking zone is determined according to the type, and the selected operation is selected from the soaking rate in the tropical zone determined according to the operation mode according to the selection of the operation mode that prioritizes production efficiency or the operation mode that prioritizes heat intensity. A heating control method for a continuous heating furnace, wherein a soaking temperature rise corresponding to the form is selected and a heating pattern is set based on the soaking temperature rise selected.

  [2] The above-mentioned [1] is characterized in that the soaking temperature rise determined for each operation mode is determined based on the steel type, charging temperature, and extraction temperature of the billet to be heated. The heating control method of the continuous heating furnace.

  In the present invention, the heating pattern can be appropriately set according to the operation mode selected according to the production load or the like of the hot rolling line (whether the operation mode prioritizes production efficiency or the operation mode prioritizes heat intensity). As a result, it is possible to improve the production efficiency and reduce the heat intensity according to the production load of the hot rolling line.

  One embodiment of the present invention will be described. In addition, the continuous heating furnace in this embodiment is a continuous heating furnace that is installed in a hot rolling line and includes a first heating zone, a second heating zone, and a soaking zone.

  And as shown in FIG. 1, this continuous heating furnace changes the operation form (heating pattern) according to the production load of a hot rolling line. That is, when the production load of the hot rolling line is large, the first heating zone, the first heating zone, and the second heating zone as shown by the solid line in FIG. It operates in the first-stage high-load type that rapidly heats up in two heating zones to reduce the temperature rise in the soaking zone. On the other hand, when the production load of the hot rolling line is small, the heat intensity unit priority operation mode is adopted, and as shown in the heating pattern shown by the broken line in FIG. The heating pattern is as large as possible.

  For this purpose, a soaking zone table for each of the operation modes of the production efficiency priority mode and the heat source unit priority operation mode is prepared in advance, and the production load of the hot rolling line After selecting / determining whether the operation mode prioritizes efficiency or the operation mode prioritizing heat intensity, select the corresponding tropical warming amount from the soaking zone and the heating pattern based on the soaking rate Is set.

  At that time, the soaking rate of the soaking zone is affected by the steel mark, the charging temperature to the heating furnace, the extraction temperature from the heating furnace, in addition to the soaking rate of the steel piece, In addition to the operation mode, the amount of warming up in the tropical zone is determined based on the steel type, the extraction temperature, and the charging temperature. For example, FIG. 2 shows the relationship between the amount of temperature rise and the amount of skid marks in the soaking zone for the hot pieces (300 ° C. or higher) and cold pieces (less than 300 ° C.) of the steel pieces to be charged. As is clear from FIG. 2, in order to reduce the skid mark amount, it is necessary to reduce the soaking temperature rise. In particular, since the amount of skid mark increases when the soaking temperature rises above 40 ° C, in the case of an operation mode that prioritizes production efficiency, the soaking temperature rise is 40 ° C or less unless there are other restrictions. It is preferable to do. Moreover, since the amount of skid marks becomes larger as the charging temperature of the steel piece becomes lower (cold piece), the soaking temperature should be smaller in the case of the cold piece than in the case of the hot piece. Similarly, steel grades containing Si, such as S45C steel, where red scale is a problem, have a problem of increasing the surface temperature, so it is necessary to suppress an increase in surface temperature regardless of the operation mode. Set a larger value. In addition, the higher the extraction temperature, the higher the amount of heat rise, and inevitably the amount of warming up in the tropical zone increases.Therefore, the amount of skid mark increases. The amount is set to be small.

  An example of such a soaking temperature increase table is shown in Table 1. In Table 1, the operation mode classification is production efficiency priority and heat intensity priority, and the steel type classification is A (those that require a warming temperature equal to or higher than a certain temperature for quality like S45C steel). And B (those without quality restrictions), the extraction temperature category is low (less than 1100 ° C), medium temperature (1100 ° C or more and less than 1200 ° C) and high temperature (1200 ° C or more), and the charging temperature category is cold ( (Less than 300 ° C.) and hot pieces (300 ° C. or higher), and based on their classification, the tropical warming amount can be selected.

  And the heating pattern of this continuous heating furnace is set by the following procedures.

  (S1) From the production load of the hot rolling line, it is determined whether it is an operation mode with priority on production efficiency or an operation mode with priority on heat intensity, and based on the operation mode, steel type, extraction temperature and charging temperature Select the soaking temperature rise from the temperature rise table.

  (S2) Next, the soaking temperature is determined from the soaking temperature and the soaking time.

  (S3) Next, an extraction temperature, a soaking rate of the tropical zone, and a heating rate from the charging temperature to the soaking zone (that is, a total heating rate of the first heating zone and the second heating zone) are determined.

  (S4) The heating rate ratio of the first heating zone and the second heating zone is determined from the heating capability of the first heating zone and the second heating zone, and the total heating rate is apportioned according to the heating rate ratio. Thus, the respective heating amounts of the first heating zone and the second heating zone are determined.

  (S5) The furnace temperature of the 1st heating zone and the 2nd heating zone is determined from the temperature rise amount of the 1st heating zone and the 2nd heating zone.

  As described above, in this embodiment, the heating pattern is appropriately set according to the operation mode determined by the production load of the hot rolling line (operation mode with priority on production efficiency or operation mode with priority on heat intensity). can do. As a result, it is possible to improve the production efficiency and reduce the heat intensity according to the production load of the hot rolling line.

  Among a plurality of continuous heating furnaces installed in the hot rolling line, one continuous heating furnace is set to an operation mode that prioritizes production efficiency (a heating pattern with a small soaking temperature rise), and other continuous heating furnaces are used. The experiment was carried out as an operation mode with a priority on heat intensity (heating pattern with a large soaking temperature rise). Specifically, the heating pattern of the continuous heating furnace was set based on the soaking temperature increase table shown in Table 1.

  As a result, the continuous heating furnace operated in the operation mode with priority on production efficiency has an effect of improving the production efficiency of 3 t / hr, and the continuous heating furnace operated in the operation mode with priority on heat source unit has a heat source unit of 2 Mcal / t. There was an improvement effect.

  In this way, by appropriately setting the heating pattern according to the operation mode (operation mode with priority on production efficiency or operation mode with priority on heat intensity) determined by the production load of the hot rolling line, It was confirmed that the production efficiency can be improved and the heat intensity can be reduced according to the production load.

It is the figure which compared the heating pattern in the operation form of the production efficiency priority, and the heating pattern in the operation form of the heat intensity priority. It is a graph which shows the relationship between the temperature rising amount and skid mark amount in the soaking zone.

Claims (2)

  A heating control method for a continuous heating furnace installed in a hot rolling line and equipped with a heating zone and a soaking zone, in advance, according to the operating mode of the operating mode with priority on production efficiency and the operating mode with priority on heat intensity. Predetermining the temperature increase in the tropics, according to the selection of the operation mode with priority on production efficiency or the operation mode with priority on the heat intensity unit, it corresponds to the selected operation mode from the soaking rate of tropical temperatures determined for each operation mode A heating control method for a continuous heating furnace, wherein a heating pattern is set based on the selected warming amount of the tropical zone, and a heating pattern is set based on the selected warming amount of the tropical zone.   2. The continuous heating according to claim 1, wherein the soaking temperature increase determined for each operation mode is determined based on a steel type of a billet to be heated, a charging temperature, and an extraction temperature. Furnace heating control method.

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