JPS61199038A - Method for controlling temperature of strip in continuous annealing furnace - Google Patents

Abstract

PURPOSE:To stabilize the control of the temp. of an strip and to reduce a change in the passing speed of the strip by regulating heating and the passing speed in accordance with the difference between the temp. of the strip at the outlet of a heating furnace and the desired temp. of the strip. CONSTITUTION:The temp. of a strip at the outlet of a heating furnace in a continuous annealing furnace is measured with a thermometer. This measured result is inputted in a temp. controller and compared with the desired heating temp. of the strip. This temp. difference is compared with a predetermined permitted temp. difference. When the temp. difference is within the permitted temp. difference, the flow rate of fuel for heating is regulated. When the temp. difference exceeds the permitted temp. difference, the passing speed of the strip and the flow rate of fuel are combinedly regulated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of controlling the heating temperature of the metal strip at the exit side of the heating furnace when the metal strip is annealed in a continuous annealing furnace.

[Conventional technology]

The plate temperature during continuous annealing of a metal strip has a significant effect on its mechanical properties, and it is required to control it with precision.

As a method of controlling the plate temperature in a conventional continuous annealing furnace, for example, as shown in JP-A-55-73830, when heating through a direct heating furnace and an indirect heating furnace,
The plate thickness is measured at the inlet side of the furnace, and the variation in plate thickness is fed forward to the direct-fired heating furnace to adjust the fuel flow rate of the direct-fired furnace.When the fuel flow rate reaches the upper and lower limits, excessive There is a method that can be adjusted by controlling the threading speed of the strip.

This has a certain effect, and even if the thickness of the strip changes, fluctuations in the strip temperature are prevented.

[Problem that the invention seeks to solve]

By the way, continuous annealing furnaces for metal strips are often equipped with a heating furnace, a holding furnace, and a cooling furnace, but changing the strip threading speed in order to adjust the temperature of the strip plate at the exit side of the heating furnace is difficult. It may become a major disturbance factor to the temperature control of the strip plate on the exit side of other furnaces, especially cooling furnaces, and when changing the threading speed, the tension of the metal strip may be disturbed throughout the continuous annealing furnace due to acceleration/deceleration, or the metal strip Meandering or the like occurs in the passing of the strip, and if it is severe, the strip plate may break in the furnace, or the strip may be scratched due to contact with the hearth roll in the furnace and the inner wall of the furnace. This tendency is particularly noticeable in thin strips produced in vertical furnaces.

The first objective of the present invention is to smoothly control the plate temperature, and the second objective is to reduce disturbances in strip tension due to plate temperature control.

Means for Solving Problem c] In the present invention, in addition to temperature control and strip threading speed control by fuel flow rate, the size of the temperature deviation between the strip temperature at the exit side of the heating furnace of the continuous annealing furnace and the target plate temperature is controlled. By using temperature control based on the furnace temperature, the number and number of changes in the strip passing speed are minimized as much as possible.

The present invention will be explained in detail below with reference to one embodiment.

FIG. 1 shows an outline of the configuration of an apparatus for carrying out one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a heating furnace of a continuous annealing furnace, and its fuel flow rate is controlled by a fuel flow rate control device 2 provided for each zone (three zones in this example) divided into a plurality of zones. 3 is a furnace temperature control device provided for each zone of the heating furnace 1, which controls the given target heating temperature and the furnace temperature detected by the thermometer 4 installed in the furnace for each zone. The fuel flow rate of the heating furnace 1 is calculated based on the deviation, and is outputted to the fuel flow rate control device 2 via the changeover switch 9 as a target flow rate.

5 is a strip heating plate temperature control device provided for the entire heating furnace, and controls a predetermined target strip heating temperature (hereinafter abbreviated as target plate temperature) and a plate provided on the furnace outlet side. Based on the strip temperature deviation from the actual temperature of the strip detected by the thermometer 6 (hereinafter abbreviated as actual strip temperature),
The fuel flow rate for each zone of the heating furnace 1 is calculated so as to eliminate this, and the calculated fuel flow rate is output as a target flow rate to the fuel flow rate control device 2 of each zone via the changeover switch 9.

7 is a plate temperature control device, and when the plate temperature deviation between the target plate temperature and the actual plate temperature is greater than a predetermined plate temperature deviation margin, steps 1 to 7 are operated.
The change in the lip threading speed is output to the in-furnace strip threading speed controller 8, and is also output to the furnace temperature controller 3 so that there is no deviation between the target heating furnace temperature and the actual furnace temperature.

The fuel flow rate control device 2 is a furnace temperature control device! 3 or the output from the heating plate temperature control device 5, the flow rate 3II moderation valve (
(not shown) to adjust the fuel flow rate and eliminate plate temperature deviation. Furnace strip threading speed control device 8
Controls the rotational speed of a lease roll drive motor (not shown) in accordance with the output from the plate temperature control device 7.

The control method of the present invention will be explained below.

The target plate temperature of the strip in continuous annealing has a slight plate temperature deviation margin 10 as shown in FIG.

Of course, it is desirable to be able to heat the plate according to the target plate temperature,
! There is a temperature margin that does not pose a practical problem in terms of deterioration of the material property values of the i2 product, and this is taken into account as the plate temperature deviation margin.

In the present invention, depending on whether or not the plate temperature deviation is within the deviation margin, plate temperature control in the heating furnace is performed using either temperature control using fuel flow rate or temperature control using a combination of plate threading speed and fuel flow rate. I will do it. That is, the actual plate temperature from the plate thermometer 6 is compared with the target plate temperature in the plate temperature control device 7, and if the plate temperature deviation is within the plate temperature deviation margin 10, heating is performed to ensure the material quality. 1 selection command is output to the selector switch 9, and the plate temperature is controlled by the fuel flow rate. That is, the heating plate temperature control device 5
The fuel flow rate in each zone of the heating furnace 1 is controlled by the fuel flow rate control device 2 with an output of 1, in order to slowly converge the plate temperature deviation to zero.

Further, if the plate temperature deviation margin 10 is exceeded, the plate temperature is outside the range where it is difficult to secure the material, so plate temperature control using plate passing control with a fast response speed of the heated plate temperature is used. That is, the plate temperature control device 7 immediately
At the same time as changing the strip passing speed, the method is switched to a method in which the fuel flow rate of the heating furnace 1 is determined by the output of the furnace temperature control device 3.

At this time, the changeover switch 9 functions as a selection switch for the outputs of the furnace temperature control device 3 and the heating plate temperature control device 5 associated with the switching of the control method, and the selection command is sent to the plate temperature control device 7. is output from.

Thereafter, when the plate temperature deviation again falls within the plate temperature deviation margin 10, the control method is again switched to the control method using the fuel flow rate.

According to the present invention, by doing as described above.

1- on the passing of the strip in the continuous annealing furnace as mentioned above.
It is possible to achieve plate temperature control with high precision and quick response without causing much trouble.

When the plate temperature deviation becomes larger than the plate temperature deviation margin lO,
The fuel flow rate of the heating furnace 1 is determined by furnace temperature control.
It is desired to maintain the appropriate heating furnace temperature of the strip (given as the target furnace temperature to the furnace temperature control device 3) as much as possible, and the fuel flow rate becomes abnormal due to a malfunction or abnormality detection of the plate thermometer 6. This is to prevent destruction of the furnace equipment or breakage of the strip due to overheating.

Embodiments of the present invention are shown in FIGS. 3a to 3d.

This will be explained below.

Figure 3a shows the actual strip temperature on the exit side of the heating furnace.

Fig. 3b shows the sheet passing speed, Fig. 3 shows the heating furnace temperature, and Fig. 3d[i9 shows the changes over time in the fuel flow rate.

In section A shown in Figure 3a, the plate temperature deviation is 1
0, and the plate temperature is controlled by the fuel flow rate control method, and after about 2 minutes the plate temperature deviation exceeds the plate temperature deviation margin of 10 or more 1, for example +15°C or more. The vehicle has entered the section entrance by switching to plank control using a combination of controls. Therefore, the sheet passing speed increases, and the fuel flow rate is also determined by the output of the furnace temperature control. The reason why the fuel flow rate is about to suddenly increase at the beginning of the section is because there is a large difference between the target furnace temperature and the actual furnace temperature when the control method is switched.

The plate temperature decreased due to the change in the plate passing speed at the start of the section, and since it was once again within the deviation margin, the control method using the fuel flow rate was switched again in the section C, and the plate temperature remained unchanged at the target plate temperature.

〔Effect of the invention〕

As described above, the present invention has advantages such as stable plate temperature control and plate passing speed that can be changed both in number and amount.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an outline of the configuration of an apparatus for carrying out one embodiment of the present invention, FIG. 2 is a graph showing a plate temperature deviation margin range in the present invention, and FIGS. 3a and 3b. FIGS. 3c and 3d are graphs showing the results of an embodiment of the present invention. 1: Heating furnace 2: Fuel flow rate control device 3: Furnace temperature control device 4: Temperature meter 5: Heating plate temperature control device 6: Plate thermometer 7: Plate temperature control device 8: Threading speed control device 9: Changeover switch lO: Board temperature deviation margin [F] 1st kudzu 2+n Figure 3a Figure 3゜factor 3d Procedure amendment (method) % formula % 1. Indication of incident Patent Application No. 39895 of 1985 2.
Title of the invention Strip plate temperature control method 3 in a continuous annealing furnace, relationship with the amended case Patent applicant address 2-6-3 Otemachi, Chiyoda-ku, Tokyo Name (665) Representative of Nippon Steel Corporation Takeshi 1
) Yutaka

Claims (1)

[Claims] To control the strip temperature in a continuous annealing furnace, the strip temperature at the exit side of the heating furnace in the continuous annealing furnace is measured and compared with the strip target heating temperature, and then the strip temperature deviation and a separately predetermined strip temperature are measured. Compared to the deviation margin, when the plate temperature deviation is within the plate temperature deviation margin, the fuel flow rate for heating is controlled,
A method for controlling the plate temperature of a strip in a continuous annealing furnace, characterized in that when the plate temperature deviation margin is exceeded, the plate passing speed and the fuel flow rate are controlled in combination.