JPH0525555A - Method for controlling sheet temperature in heating zone and device therefor of continuous heat-treating line - Google Patents

Abstract

PURPOSE:To control the sheet temp. at the outlet of a heating zone within the desired limits determined with respect to the quality of the sheet in the radiant tube-type heating zone of continuous annealing equipment. CONSTITUTION:The thermometers 1 and 2 for the sheet are provided at the intermediate part and outlet of a heating zone in the radiant tube-type heating zone of continuous annealing equipment, and the furnace temp. at the first half of the heating zone is controlled by the thermometer 1 at the intermediate part and the furnace temp. at the second half by the thermometer 2 at the outlet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate temperature control method and apparatus in a heating zone of a continuous heat treatment line such as continuous annealing equipment.

[0002]

2. Description of the Related Art In continuous annealing equipment for steel strips, generally, as shown in FIG. 4, a heating zone 10, a soaking zone 11, a cooling zone 12 (a rapid cooling facility 12a such as a gas jet and a slow cooling facility 12b such as a cooling tube) are used. Consists of a quenching zone 13 and other furnace configurations. Then, the heat treatment is performed in the annealing pattern as shown in FIG. 5, and the material control of the steel strip X is performed.
Of these, the outlet plate temperature of the heating zone 10 is an important factor for determining the material, and it is very important to keep it within a predetermined target range.

For this reason, in the heating zone 10, particularly the radiant tube type heating zone, the heating furnace outlet plate temperature was kept within the target range by the following constitution.

One of them is, as shown in FIG. 6, an operator monitors the output of the outlet plate thermometer 2a and the furnace temperature of each zone of # 1 to # 7, and the air flowing to the radiant tube of each zone. The amount (thick solid line in the figure) and gas flow rate (thin solid line in the figure) are manually input to the gas flow rate setting device 6 to control the flow rate. As shown in FIG. 7, the operator controls the furnace temperature by monitoring the output of the outlet plate thermometer 2a and manually inputting the furnace temperature reference value into the furnace temperature setting device 7. As shown in FIG. 8, the operator sets the outlet target plate temperature in the plate temperature setter 8, and the outlet plate thermometer 2a feeds the plate temperature back to the setter 8 for control.

[0005]

In a line having the above-described plate temperature control structure, the outlet plate temperature deviates from the predetermined target plate temperature due to the following reasons, resulting in a material abnormality and a reduction in yield.

In the first configuration, the manual operation by the operator causes the outlet plate temperature to vary depending on the skill level of the operator. Also, with the other configuration, adjustment is difficult, and therefore it has not been put to practical use. In other words, the factors that cause fluctuations in the outlet plate temperature include changes in line speed and plate size such as coil units, as well as changes in radiation heat transfer efficiency due to changes in plate thickness tolerance and changes in plate surface properties. Can be given. The latter is a change that occurs at a pitch of several tens of meters in the lengthwise direction of the plate, and therefore the control system for the outlet plate temperature needs a response corresponding to this, but the response of the furnace itself to this is low. That is, the path length of the heating zone is usually a hundred and several tens of meters, and when a radiant tube is used, the rate of change of the furnace temperature is several degrees per minute, so the furnace temperature is changed and the result is It takes several tens of seconds to several minutes for the plate temperature to appear. Therefore, it is difficult to adjust the control constants (proportional, integral, differential constant) in the plate temperature adjusting system.

The present invention was devised in view of the above problems of the prior art, and provides a plate temperature control method and apparatus for keeping the plate temperature at the exit of the heating zone of a continuous heat treatment line within a predetermined target range. It is intended to be provided.

[0008]

Therefore, the plate temperature control method in the heating zone of the continuous heat treatment line according to the present invention measures the plate temperature at the intermediate portion and the outlet of the heating zone, and based on the detected value of the intermediate portion plate temperature. In addition to controlling the furnace temperature in the first half of the heating zone, the furnace temperature in the latter half of the heating zone is controlled so that the plate temperature is determined by the material based on the detected value of the outlet plate temperature. .

A second aspect of the present invention relates to an apparatus for carrying out the method of the first aspect of the present invention. As a specific configuration thereof, one or a plurality of plate thermometers are provided at each of an intermediate portion of the heating zone and an outlet of the heating zone, and the first half of the heating zone is provided. It has a furnace temperature control system that feedback-controls the furnace temperature of the middle part based on the detection value of the intermediate plate thermometer, and the furnace temperature of the latter half of the heating zone is determined by the material based on the detection value of the outlet plate thermometer. It is characterized by having a furnace temperature control system that performs feedback control so that the plate temperature is reached.

The installation position of the intermediate plate thermometer will be determined with reference to the outlet plate temperature influence coefficient. Here, the outlet plate temperature influence coefficient means the furnace temperature of a specific zone of the heating zone at 10 ° C.
The amount of change in the outlet plate temperature when the temperature is changed is expressed by the ratio to 10 ° C. A simulation example of the outlet plate temperature influence coefficient is shown in FIG. As shown in Fig. 9, the outlet plate temperature influence coefficient changes depending on the path length of the zone and the hearth load (plate thickness * line speed * plate specific gravity), but it shows a larger value for the outlet side zone and the zone with a longer path length. It will be.

Therefore, in the structure of the present invention, for the purpose of improving the responsiveness of the plate temperature control of the outlet plate temperature, the intermediate plate thermometer is set just before the outlet-side final zone having a large outlet plate temperature influence coefficient, or It is desirable to install it just before the zone in front of it.

[0012]

In the above configuration of the present invention, the heating zone is controlled to be divided into two parts for controlling the plate temperature in the middle part of the heating zone (a plate thermometer is installed in the middle part), and the furnace is further provided in each region. By performing temperature control (installing a furnace temperature control system for each), it is possible to obtain a stable outlet plate temperature.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the second invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the plate temperature control apparatus of the second invention in a radiant tube type heating furnace of a strip X continuous annealing facility.

The heating furnace 10 is composed of a plurality of zones from # 1 zone to # 7 zone, and each of these zones #
A gas flow rate setting device 6 is provided in each of 1 to # 7, and the amount of air (thick solid line in the figure) and the gas flow rate (thin solid line in the figure) that flow into the radiant tube for each zone are adjusted. . These configurations are no different from the configurations of the above-mentioned prior art.

In this embodiment, an intermediate plate thermometer 1 and an outlet plate thermometer 2 are installed immediately before the final # 7 zone on the furnace outlet side and at the furnace outlet, respectively. Input the detected values of the first half furnace temperature control system 3 that will control the operation of the gas flow rate setting device 6 provided in the # 1 to # 6 zones and the outlet plate thermometer 2 on the other hand. However, the latter half furnace temperature control system 4 for finally controlling the operation of the gas flow rate setting device 6 provided in the final zone of # 7 is also provided.

In the first half furnace temperature control system 3, the detected value input from the intermediate plate thermometer 1 is compared with the intermediate target plate temperature calculated by the outlet plate temperature calculator 5 described later and input. A furnace central part plate temperature setting device 30 that outputs a plate temperature setting value in the central part of the furnace according to the deviation, and a furnace temperature setting ratio for each zone is calculated based on the plate temperature setting value output from the setting device 30. ,
The operation of the gas flow rate setter 6 in each of these zones is controlled according to the respective furnace temperature settings of # 1 to # 6 based on the ratio # 1
To # 6 furnace temperature setting device 31.

Similarly, the latter half furnace temperature control system 4 compares the detected value input from the outlet plate thermometer 2 with the outlet target plate temperature calculated and input by the outlet plate temperature calculator 5 described later. Then, the furnace exit side plate temperature setter 40 that outputs the furnace exit side plate temperature set value according to the deviation, and the furnace temperature set value of the final zone # 7 based on the plate temperature set value output from the setter 40 And a # 7 furnace temperature setter 41 for controlling the operation of the gas flow rate setter 6 in the zone according to the furnace temperature setting.

In the present embodiment, the intermediate target plate temperature and the outlet target plate temperature input to the furnace center plate temperature setting device 30 and the furnace exit side plate temperature setting device 40 are based on the calculation of the outlet plate temperature calculating device 5. This is output from there, but this calculation is performed when the preset reference value is input to the calculator 5. That is, when a reference value that is the outlet target plate temperature determined by the operator from the material is given to the outlet plate temperature calculator 5, the calculation by the calculator 5 starts and the outlet target plate temperature is first output, and The calculated value obtained from the radiation heat transfer calculation formula based on the outlet target plate temperature is output as the intermediate target plate temperature.

In the above-described configuration of this embodiment, when the preset reference value of the outlet target plate temperature is input to the outlet plate temperature calculator 5, the calculator 5 causes the central part of the furnace of the first half furnace temperature control system 3 to operate. The intermediate target plate temperature is output to the plate temperature setting device 30, and the outlet target plate temperature is output to the furnace outlet side plate temperature setting device 40 of the latter half furnace temperature control system 4. In this furnace central part plate temperature setting device 30, the plate temperature measured value immediately before the final zone of the intermediate plate thermometer 1 is compared with the intermediate target plate temperature, and the plate temperature set value of the furnace central part is output according to the deviation. It Further, the furnace outlet side plate temperature setting device 40 also compares the outlet plate temperature measurement value of the outlet plate thermometer 2 with the outlet target plate temperature, and outputs the plate temperature set value on the furnace outlet side according to the deviation. And the plate temperature set value in the central part of the furnace is # 1
When input to the # 6 furnace temperature setter 31, the furnace temperature setting ratio for each zone is obtained based on the input value, and the furnace temperature setting ratios # 1 to # 6 based on the ratio The # 6 furnace temperature setting device 31 controls the operation of the gas flow rate setting device 6 in each zone. On the other hand, when the plate temperature set value on the exit side of the furnace is input to the # 7 furnace temperature setter 41, the furnace temperature set value of the final zone # 7 is calculated based on the input value, and then the zone is set according to the furnace temperature setting. The operation of the gas flow rate setting device 6 will be controlled.

FIG. 2 shows the results when the control was carried out by the first invention method in the heating furnace of the continuous annealing equipment described above, and FIG. 3 shows the results when the control was carried out by means of the conventional structure. Both figures are graphs showing the variation of each factor in the state where the line speed is constant, but in FIG. 3, it is caused by the change of the radiation heat transfer efficiency due to the change of the plate thickness within the allowable error or the change of the surface property of the plate. While the plate temperature fluctuation is observed in the intermediate plate temperature and the outlet plate temperature, in FIG. 2, the fluctuation of the intermediate plate temperature is suppressed by the plate temperature control system, and the outlet plate temperature is controlled without fluctuation. You can see that

As described above, according to the present invention, the actual machine data shows that the outlet plate temperature is controlled to be constant.

[0023]

As described above, according to the present invention, the outlet plate temperature of the continuous annealing equipment heating zone is kept constant,
It becomes possible to avoid a decrease in yield. still,
It goes without saying that the plate temperature control configuration according to the present invention can be applied not only to the heating zone of the continuous annealing equipment, but also to the heating zone and the cooling zone of the process line in which the furnace is installed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control configuration according to an embodiment of a second invention.

FIG. 2 is a graph showing changes in plate temperature at the middle of the heating zone and the outlet in the present embodiment.

FIG. 3 is a graph showing transitions of plate temperatures at the middle and the exit of the heating zone in the conventional configuration.

FIG. 4 is a schematic diagram showing an example of a furnace configuration of continuous annealing equipment.

FIG. 5 is a graph showing a heat pattern of continuous annealing equipment.

FIG. 6 is a block diagram showing a conventional outlet plate temperature control configuration.

FIG. 7 is a block diagram showing another example of a conventional outlet plate temperature control configuration.

FIG. 8 is a block diagram showing another example of a conventional outlet plate temperature control configuration.

FIG. 9 is a graph showing an example of an outlet plate temperature influence coefficient of a heating zone.

[Explanation of symbols]

1 Intermediate plate thermometer 2 Exit plate thermometer 3 First half furnace temperature control system 4 Second half furnace temperature control system 5 Exit plate temperature calculator 6 Gas flow rate setting device 10 heating zone X strip

Claims (2)

[Claims] 1. A plate temperature is measured at an intermediate portion and an outlet of a heating zone of a continuous heat treatment line, the furnace temperature in the first half of the heating zone is controlled based on the detected value of the intermediate portion plate temperature, and the outlet sheet temperature A plate temperature control method in a heating zone of a continuous heat treatment line, characterized in that the furnace temperature in the latter half of the heating zone is controlled so that the material temperature is determined based on the detected value. 2. A furnace temperature control system, wherein one or a plurality of plate thermometers are provided at each of an intermediate portion and an outlet of a heating zone of a continuous heat treatment line, and the furnace temperature control system controls the furnace temperature based on the detected values of these plate thermometers. A plate temperature control device in a heating zone of a continuous heat treatment line, wherein the plate temperature control device is provided separately corresponding to the installation location of the plate thermometer.