JP2867857B2 - Continuous annealing furnace with steel strip temperature controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention, continuous annealing furnace, in particular comprising a temperature adjustment device of the steel strip, the temperature adjustment of the strip, communicates capable of flattening the steel strip, to prevent the occurrence of shape defect
It relates to a continuous annealing furnace .

[0002]

2. Description of the Related Art Many techniques have been proposed for a method or a device for preventing the occurrence of a shape defect of a steel strip in a continuous annealing furnace. Basically, a method of controlling the temperature in the width direction of the steel strip has been proposed. It is known that preventing temperature unevenness is effective.

For example, as a technique for preventing temperature unevenness in a steel strip width direction in a heating and soaking stage, Japanese Patent Application Laid-Open No. Sho 58-133326 discloses a technique of shortening a contact time with a roll and performing uniform heating. Japanese Patent Application Laid-Open No. 62-086126 discloses that the heat input of a steel strip is controlled in the width direction of the steel strip.
JP-A-62-281291, JP-A-2-175823, JP-A-56
-19563, JP-A-60-2634, JP-A-60-24
4418, JP-A-62-99421, JP-A-2-1530
No. 26, JP-A-1-157148, JP-A-1-157149
In the publications, it is proposed to change the heat input in the steel strip width direction by various methods.

Techniques for preventing temperature unevenness in the width direction of the steel strip in the cooling stage include, for example, JP-A-59-162230, JP-A-57-79156, JP-A-55-158228 and Japanese Patent No. 58-133326, Japanese Patent No. 1374325, Japanese Patent No. 1558883, Japanese Patent No. 12578312,
JP-A-62-188731, JP-A-2-66125, and the like have proposed techniques for uniform cooling in the steel strip width direction or controlling the temperature difference in the steel strip width direction. Tokiko Sho 61-
Japanese Patent No. 45691 discloses a method of arranging a plurality of U-shaped cooling tubes in a cooling zone and controlling the amount of cooling air to uniformly cool the steel strip in the width direction.

[0005]

However, in the prior art, since it is assumed that the steel strip is uniformly heated, that is, the temperature difference in the width direction of the steel strip is suppressed for a long time, the continuous annealing furnace is required. In order to achieve uniform heating in the width direction of the steel strip over a furnace length of several tens of meters constituting the heating zone, complicated equipment is required, and there is a problem in equipment cost and operability.

In the method of Japanese Patent Publication No. 61-45691, the cooling rate is controlled by controlling the flow rate of cooling air. However, since the cooling tube has a heat capacity,
The responsiveness of the temperature in the steel strip width direction is poor only by such cooling air flow rate control, and there is a problem that a sufficient control ability cannot be obtained when the width of the steel strip is changed.

Here, the object of the present invention is to provide a relatively simple and inexpensive steel strip temperature control device of several meters and a conventional uniform heating technique using the same, but the steel strip width at the heating stage. communicating the temperature unevenness in the direction the flat strip can be obtained even has occurred
It is to provide a continuous annealing furnace .

[0008]

Means for Solving the Problems As a result of various studies to solve such problems, the present inventors first obtained the following recognition on the current state of the prior art. The base material shape of the steel strip to be subjected to continuous annealing is flat, and the steel strip is uniformly heated and cooled in the width direction of the steel strip in the continuous annealing furnace, and the tension in the steel strip longitudinal direction is uniform in the steel strip width direction. In some cases, it is obvious that the product shape becomes flat.

When the flatness of the base material is relatively good, uniform heating is performed in the width direction of the steel strip, whereby the shape of the base material is corrected by elongation generated in the heating step, and uniform cooling is performed in the width direction of the steel strip. , A product having a good shape can be obtained.

[0010] However, it is difficult to obtain a completely flat base material shape by the current rolling technology. When the flatness of the base material is relatively poor, annealing is performed with the steel strip given an appropriate in-furnace steel strip longitudinal tension, thereby causing the strip to elongate in the longitudinal direction, thereby reducing the flatness of the final product. The method of securing is adopted.

In such a case, a situation occurs in which the shape of the base material is not corrected by simply performing uniform heating and uniform cooling in the width direction of the steel strip. In order to solve such a problem, the above-described related art proposes that the shape is corrected at the cooling stage by changing the cooling air flow in the width direction of the steel strip.

On the other hand, the uniform cooling technique is based on the premise that the steel strip whose base material shape has been corrected is cooled in the heating and soaking stages. Therefore, the uniform cooling technique alone cannot prevent the shape defect of the steel strip. That is, conventionally, uniform heating for a long time or forced correction has been performed.

In view of the above, the significance of the solitary zone, which has not received much attention until now, was examined on the premise of such conventional technology. It was found that soaking time was critical for ensuring the flatness of the steel strip, and that the effect was significant even in a short time. In addition, it was unexpectedly found that the temperature difference in the width direction could be easily adjusted by a temperature control device provided with a plurality of heating devices and cooling devices parallel to the longitudinal direction of the steel strip in the solitary tropics. More preferably, the present inventors have found that a uniform cooling device in a cooling zone is effective in deteriorating the shape in a cooling zone of a steel strip once flattened in a uniform zone, and completed the present invention.

Here, the present invention is directed to a steel strip extending in the longitudinal direction of the steel strip so as to face the steel strip surface in a soaking zone in a continuous annealing furnace.
Is a continuous sintered with a temperature adjustment device of the steel strip having at least one unit consisting of a steel band edge and arranged sequentially in a plurality of the heating device and a cooling device provided in the strip width direction
It is a blunt furnace .

[0015] In the preferred embodiment of the present invention further provides a continuous annealing furnace provided with said device, Oite the cooling zone,
Opposite the steel strip surface, it extends in the steel strip longitudinally disposed sequentially arranging a plurality of heating devices and cooling devices to strip width direction from the steel strip ends, the heating device and cooling The continuous annealing furnace is characterized in that the distance between the squeezing device and the steel strip is attached so as to be adjustable one by one.

[0016]

[0017]

Next, the operation of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing a configuration of a generally used horizontal continuous annealing furnace 10 incorporating a device of the present invention . Incorporate in.

The continuous annealing furnace comprises a pre-tropical zone 12, a heating zone 14,
The pre-tropical zone 12 and the heating zone 14 are heated by a direct burner or a radiant tube (not shown). In the heating step of the steel strip, a nonuniform temperature of about 50 ° C. at the maximum in the width direction of the steel strip occurs at a heating rate of 5 to 40 ° C./sec. For this reason, the elongation is uneven in the width direction of the steel strip.

The apparatus of the present invention is a small-sized equipment having a length of several meters (for example, 6 m), and is suitable for a horizontal continuous annealing furnace. Hereinafter, a vertical continuous annealing furnace will be described. May be applied. The steel strip treated according to the present invention is not particularly limited, but for example, has a thickness of 0.2 to 0.6 mm and a width of 600 to 120.
It is a 0 mm steel strip.

In the temperature control device of the present invention incorporated in a solitary tropical zone,
2 with is a cross-sectional view of a temperature adjusting device 20 of the present invention a schematic plan view showing a structure incorporated into a soaking zone 16, FIG. 3 is a line A-A of FIG. In FIG. 2, the steel strip 22 runs from left to right in the drawing.

The temperature adjusting device 20 shown in FIG. 2 is composed of units 28a and 28b in the illustrated example. The unit is composed of an air cooling tube 24 as a cooling device and an electric heater 26 as a heating device. The electric heater and the air-cooling tube are provided in parallel with the longitudinal direction of the steel strip, and are arranged in this order from the end of the steel strip in the width direction of the steel strip. In the example shown,
An electric heater is further provided at the center. These heating and cooling devices perform temperature control in the steel strip width direction by appropriately adjusting the output, cooling air flow rate, etc., in accordance with the temperature distribution measurement values in the steel strip width direction obtained by the steel strip thermometers 32a to 32c. .
In FIG. 2, the electric heater 26 divided into three in the steel strip width direction and the air-cooled tube 24 divided into two in the width direction of the steel strip are used for simplification of the description.

The electric heater 26 corrects the temperature difference in the width direction of the steel strip generated in the preceding heating zone, and at the same time, prevents temperature unevenness such as cooling of the steel strip edge in the solitary zone. On the other hand, the air-cooling tube 24 provided along the steel strip longitudinal direction in parallel with the electric heater 26 cools a high-temperature portion near the center of the steel strip, thereby reducing the temperature difference in the steel strip width direction. A radiation thermometer having a scanning mechanism (not shown) is preferably used as the steel strip thermometer for measuring the temperature variation in the width direction of the steel strip.

The heating and cooling capacities of the electric heater and the air-cooling tube vary depending on the size of the steel strip to be treated. For example, two electric heaters of 200 KW and four air-cooling tubes of 100 Nm ³ / h may be provided. . The heating device of the present invention includes an induction heating device and the like, and the cooling device includes a gas jet cooling and the like.

The furnace body 30 constituting the main body of the temperature control apparatus according to the present invention has a heating temperature 70 of the steel strip 22 to be subjected to continuous annealing.
The material and structure must be able to withstand the furnace temperature required to maintain 0 ° C or higher.

Regarding the method of flattening a steel strip In the method of flattening a steel strip by temperature control in the pre-tropical zone and the soaking zone after the heating of the heating zone according to the present invention,
If the temperature difference in the steel strip width direction exceeds 6 ° C., sufficient flatness cannot be ensured. On the other hand, when the steel strip temperature is lower than 700 ° C., the elongation of the steel strip cannot be secured in the solitary zone, and the flattening effect is weakened. Further, when the soaking time (time for maintaining the temperature difference in the predetermined steel strip width direction) is less than 10 seconds, the creep deformation time of the steel strip cannot be secured, and sufficient flatness cannot be obtained and the flatness cannot be obtained. Effect is weakened. Therefore, preferable conditions are a steel strip temperature of 700 to 1100 ° C. and a soaking time of 10 to 25 seconds. Preferably it is 850-1100 degreeC and 12-25 seconds. The temperature difference in the steel strip width direction is within 6 ° C, preferably within 4 ° C, and is as small as possible. This will be described in more detail in an embodiment.

Thus, according to the present invention, in the tropics,
After correcting the temperature unevenness and the shape defect in the steel strip width direction, cooling is performed in the cooling zone while ensuring uniformity in the steel strip width direction.
The cooling device in the cooling zone will be exemplified later, but is not limited thereto.For example, as many technologies have been conventionally proposed, for example, gas jet cooling may be performed to control the air volume in the width direction. Good.

Thus, according to the method of the present invention,
In the heating zone, even a steel strip having a maximum temperature difference of 50 ° C. in the width direction of the steel strip can be easily flattened, and a substantially flat steel strip can be obtained even after a normal cooling history.

In a preferred embodiment of the temperature control device in the cooling zone
4 with the cooling zone of a continuous annealing furnace, schematic plan view showing a structure incorporating a temperature regulating device 20 of the steel strip of the present invention using a cooling device, FIG 5 is a schematic side view of the device of FIG. 4 is there. In the figure,
The steel strip 22 runs from right to left in the drawing.

Since the method for controlling the temperature of the steel strip is in accordance with the above description, only the differences will be described. 4 and 5 is a device for adjusting the distance d between the steel strip 22 and the cooling tube 24.
That is, 40 is provided. In the figure, a total of six cooling tubes 24, three in the upper and lower directions, and twelve cooling distance adjusting devices 40 for moving the cooling tubes 24 are provided. It is preferable that the moving speed is high as far as the equipment cost permits, in order to improve the responsiveness. As a specific means, for example, an electric jack is used. By adjusting the cooling distance and the cooling gas, it is easy to quickly cool a part of the steel strip and make the steel strip temperature uniform.

FIG. 6 is a schematic plan view showing a structure in which a steel strip temperature control device 20 of the present invention using a heating device is incorporated in a cooling zone of a continuous annealing furnace. FIG. 7 is a schematic side view of the device of FIG. FIG. In the drawing, the steel strip 22 runs from right to left in the drawing. A feature of the device shown in FIGS. 6 and 7 is that an adjustment device 42 for the distance d between the steel strip 22 and the electric heater 26 is provided similarly to the above-described device. The larger the number of electric heaters, the more advantageous in terms of control performance. In the figure, twelve electric heaters 26 and twelve heating distance adjusting devices 42 for moving them are provided. It is preferable that the moving speed is high as far as the equipment cost permits, in order to improve the responsiveness. As a specific means, for example, an electric jack may be used. The adjustment of the heating distance and the adjustment of the heating output quickly heats a part of the steel strip and makes it easy to make the steel strip temperature uniform.

By providing these temperature control devices in the cooling zone and performing uniform cooling, it is possible to prevent the steel strip once flattened in the uniform zone from deteriorating in the cooling zone, and to obtain a flatter steel strip. it can. Next, the present invention will be described more specifically with reference to examples.

[0032]

【Example】

(Example 1) Preliminary test First, as a preliminary test, it was examined how the temperature difference in the steel strip width direction and the soaking time condition had an influence on flatness in a soaking zone. FIG. 8 shows a graph comparing the temperature difference in the steel strip width direction with the flatness. Soaking temperature (steel strip temperature in soaking tropics)
When the temperature was 700 to 850 ° C and the soaking time was 12 seconds, the temperature difference was 6 ° C or less, and good flatness was obtained.

FIG. 9 is a graph showing the soaking time and flatness. Soaking temperature 700-850 ℃, steel strip width direction temperature difference 4 ℃
In case (1), good flatness was obtained with a soaking time of 10 seconds or more. It was also found that when the steel strip temperature was less than 700 ° C, the elongation of the steel strip in this solitary tropics could not be secured, and the effect diminished. Therefore, preferable conditions for the above embodiment are a steel strip temperature of 700 to 1100 ° C. and a soaking time of 10 to 25 seconds. The temperature difference in the steel strip width direction is within 6 ° C., and is preferably as small as possible.

This test In this example, the steel strip was subjected to continuous annealing using the continuous annealing furnace and the temperature adjusting device shown in FIGS. 1, 2 and 3, and the presence or absence of shape defects was investigated. The steel strip was received from the heating zone, and the temperature was adjusted in the soaking zone. At that time, the temperature distribution in the width direction of the steel strip was 50 ° C at the maximum. The thermometer 32a confirmed that the steel strip width temperature was uniform in the No. 1 zone, and in the No. 2 zone, the temperature was maintained at 700 ° C for 10 seconds or more while maintaining the temperature uniformity in the steel strip width direction. The line speed and the like were adjusted to perform soaking. This flattened the strip and then sent it to the cooling zone.

In the cooling zone, the air flow in the steel strip direction in the gas jet cooling was appropriately adjusted, uniform cooling was performed, and after cooling to 150 ° C., it was sent further downstream of the line. Table 1 summarizes the processing conditions and flatness results in this example.

[0036]

[Table 1]

Even if the temperature difference in the width direction and the soaking time are appropriate as shown in Example A, there is no sufficient effect at the soaking temperature of 650 ° C. However, as shown in Examples B and C, 700 ° C. and 850 ° C. It became flat at a soaking temperature of ° C. When the soaking temperature is appropriate at 850 ° C. and the soaking time is also appropriate at 12 seconds, the plateau becomes flat when the temperature difference in the width direction is 4 ° C. as shown in Example C, while the results are shown in Examples D and E. As described above, when the temperature difference in the width direction was 8 ° C. or 15 ° C., the surface was not flat.

Further, when the soaking temperature and the temperature difference in the width direction are appropriate as shown in Examples C and F, the soaking time is 12 seconds and
At 10 seconds, flatness is obtained, while, as shown in Example G,
When the soaking time was as short as 8 seconds, it was not flat.
The steel composition, mechanical properties, and shape of the steel strip used in this example are shown.

[0039]

[Table 2]

(Embodiment 2) Next, as a preferred embodiment of the present invention, a case where the apparatus shown in FIGS. 4 and 5 is incorporated in a cooling zone will be described. Note that this test was performed without operating the device of the present invention in the solitary tropics.

Table 3 shows the apparatus according to the present invention. Assuming the prior art, the cooling distance adjusting device 40 is fixed, and the distance d between each of the cooling tubes arranged in the width direction and the steel strip surface is constant. The degree of flatness when performing was shown. FIG. 10 shows the distribution of the steel strip temperature at that time.

Table 4 shows the flatness when the distance d between the cooling tubes arranged in the width direction and the steel strip surface was controlled in the apparatus of the present invention. The flatness is indicated by the height / wavelength of the peak, and the left and right are viewed from the traveling direction of the steel strip. FIG. 11 shows the distribution of the steel strip temperature at that time.

[0043]

[Table 3]

Comparing the above, it can be seen that the temperature difference in the width direction at the outlet of the apparatus of the present invention is smaller, the flatness is higher, and the case where the distance d to the steel strip surface is controlled is preferable.
The reason for this is that, as shown in FIG. 12, the speed of temperature adjustment, so-called response time, is greatly different, and controlling the distance d from the steel strip surface can be achieved in a short time (for the same line speed). It can be seen that the temperature difference is eliminated (with short equipment) and the surface becomes flat.

(Embodiment 3) Next, as a preferred embodiment of the present invention, a case where the apparatus shown in FIGS. 6 and 7 is incorporated in a cooling zone will be described. This test was also performed without operating the device of the present invention in a solitary zone.

Table 5 shows the apparatus of the present invention. Assuming the prior art, the heating distance adjusting device 42 is fixed, the output of the electric heater is kept constant, and the steel heater of each electric heater arranged in the width direction is fixed. The flatness when the distance d from the band surface was constant was shown. FIG. 13 shows the distribution of the steel strip temperature at that time.

Table 6 shows the flatness when the distance d between the electric heaters arranged in the width direction and the steel strip surface was controlled using the apparatus of the present invention. FIG. 14 shows the distribution of the steel strip temperature at that time.

[0048]

[Table 5]

Comparing the above, it can be seen that when the distance d to the steel strip surface is controlled, the temperature difference in the width direction at the outlet of the apparatus of the present invention is smaller, the flatness is higher, and it is preferable.
The reason for this is that, as shown in FIG. 15, the speed of temperature adjustment, so to speak, differs greatly in response time, and controlling the distance d from the steel strip surface can be achieved in a short time (for the same line speed). It can be seen that the temperature difference is eliminated (with short equipment) and the surface becomes flat.

[0050]

As described in detail above, according to the present invention,
The temperature can be controlled in the soaking zone of the continuous annealing furnace, and almost perfect flatness can be achieved by controlling the temperature in the width direction of the steel strip, and the equipment for that is simple and very cost-effective. It is advantageous.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a configuration of a general horizontal continuous annealing furnace to which the present invention is applied.

FIG. 2 is a schematic plan view of a temperature adjusting device for a steel strip provided with a heating device and a cooling device in an evenly tropics, which is an example of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is an example of a preferred embodiment of the present invention, and is a schematic plan view of a temperature control device for a steel strip provided with a cooling device capable of adjusting a distance from the steel strip in the cooling zone.

FIG. 5 is a schematic side sectional view of FIG. 4;

FIG. 6 is an example of a preferred embodiment of the present invention, and is a schematic plan view of a temperature control device for a steel strip provided with a heating device capable of adjusting a distance from the steel strip in a cooling zone.

FIG. 7 is a schematic sectional side view of FIG. 6;

FIG. 8 is a graph showing a relationship between a temperature difference in a steel strip width direction and flatness for studying a use condition of the apparatus of the present invention.

FIG. 9 is a graph showing the relationship between the soaking time and flatness for studying the use conditions of the apparatus of the present invention.

10 is a graph showing a steel strip temperature distribution when the distance between the cooling device and the steel strip is fixed as shown in Table 3 in the apparatus of FIG.

11 is a graph showing the temperature distribution of the steel strip when the distance between the cooling device and the steel strip is appropriately adjusted as shown in Table 4 in the apparatus of FIG.

FIG. 12 shows a decrease in the temperature difference between the center and the edge of the steel strip when the distance between the cooling device and the steel strip is appropriately adjusted as shown in Table 4 and when the distance is not adjusted. 3 is a graph showing the state of () with respect to time (second).

13 is a graph showing a steel strip temperature distribution when the distance between the heating device and the steel strip is fixed as shown in Table 5 in the apparatus of FIG.

FIG. 14 is a graph showing a steel strip temperature distribution when the distance between the heating device and the steel strip is appropriately adjusted as shown in Table 6 in the apparatus of FIG.

FIG. 15 shows a decrease in the temperature difference between the center and the edge of the steel strip when the distance between the heating device and the steel strip is appropriately adjusted as shown in Table 6 and when the distance is not adjusted. 3 is a graph showing the state of () with respect to time (second).

[Explanation of symbols]

 10: Horizontal continuous annealing furnace 12: Pre-tropical zone 14: Heating zone 16: Uniform tropical zone 18: Cooling zone 20: Steel strip temperature control device 22: Steel strip 24: Cooling device 26: Heating device 28a: First unit 28b: Second Unit 30: Furnace body 32a to 32c: Steel strip thermometer 40: Cooling distance adjusting device 42: Heating distance adjusting device

Claims (2)

(57) [Claims] 1. A plurality of heating devices extending in the longitudinal direction of a steel strip in a soaking zone in a continuous annealing furnace so as to face the surface of the steel strip, and sequentially arranged in the width direction of the steel strip from an end of the steel strip. A continuous annealing furnace equipped with a steel strip temperature control device provided with at least one unit composed of a steel plate and a cooling device. 2. A continuous annealing furnace provided with the temperature adjusting device according to claim 1, wherein the cooling zone extends in the longitudinal direction of the steel strip so as to face the surface of the steel strip, and extends from the end of the steel strip. A plurality of heating devices and cooling devices are sequentially arranged in the band width direction,
A continuous annealing furnace wherein the distance between the heating device and the cooling device and the steel strip can be adjusted one by one.