JPH11229040A - Annealing method and apparatus correcting shape of fe-ni alloy steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Fe-Ni alloy steel strip having thin thickness and wide width and excellent strip shape by correcting the unevenness to the strip width direction of strain in the longitudinal direction of the strip already formed before charging an annealing furnace, at the same time of a stress removal annealing in a vertical furnace. SOLUTION: The following processes are executed in order. (1) The Fe-Ni alloy steel strip is heated at the recrystallized temp. or lower and cooled. (2) Three or more of rolls 4 are arranged in the longitudinal direction orthogonal to the strip 1 at the inlet side in a cooling zone 3 and the strip 1 is pushed in and the restraint in the strip width direction is loaded to the strip 1. (3) A curvature radius of the pushed strip 1 is adjusted to 2500-5000 mm. (4) The max. temp. of the strip at the position where the restraint is loaded, is adjusted to in the range of 200-500 deg.C. (5) A conveying stress of the strip is adjusted to in the range of 0.1-20 kg/mm<2> and the conveying stress in the (5) according to the strip shape before charging into the annealing furnace 5 is regulated to in the range of 0.1-20 kg/mm<2> . (6) The max. heating temp. is executed in the range of 500-700 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to remove the stress remaining on a Fe--Ni alloy steel strip after temper rolling, and to reduce uneven strain formed on the strip by the temper rolling. In order to homogenize and correct the plate shape, the above-mentioned strip is heated and cooled at a temperature lower than the recrystallization temperature using a vertical annealing furnace, and high strip tension is applied thereto while the strip is constrained in the width direction. The present invention relates to an annealing method for performing heat treatment and an annealing apparatus.

[0002]

2. Description of the Related Art The Ni content targeted by the present invention is 30%.
-40 wt.% Fe-Ni alloy steel sheet, e.g.
Since the thin plate of Invar alloy containing wt.% has excellent low coefficient of thermal expansion characteristics, it is widely used as a shadow mask for cathode ray tubes, and its thickness is as thin as 0.05 to 0.2 mm. . The Fe-Ni alloy steel strip applied to a special use in such an electronic material is required to have a large plate shape, excellent flatness, and a beautiful and dense surface property.

[0003] Such a material is subjected to stress relief annealing after temper rolling, and as a sheet shape defect before the annealing, there are generally middle elongation and ear waves in addition to the corrugated sheet. The corrugated sheet is generated by buckling of the sheet in the width direction. Medium elongation and ear waves occur due to the difference in the longitudinal distortion of the plate depending on the width position.

On the other hand, there are a vertical furnace and a horizontal furnace as such stress relief annealing furnaces for strips of material. In the horizontal furnace, since the catenary due to the weight of the strip, which is a problem in the vertical furnace, is hardly applied to the strip itself, a plate shape defect due to the catenary does not occur. However, there is a disadvantage that a surface flaw is easily generated by contact with a support roll provided in the furnace. Therefore, in the present invention, improvement is intended for a vertical furnace in which a roll such as a horizontal furnace is not provided in a heating furnace.

By the way, in tension annealing generally applied to a carbon steel strip or an alloy steel strip, when the strip thickness is relatively large and the width is relatively small, the transport tension is as high as, for example, about 20 kg / mm ^2. Even if tension annealing is performed with tension applied, no bending in the width direction of the strip, a so-called corrugated shape, does not occur after the treatment, and neither middle elongation nor ear waves occur.
There is no problem.

However, in the case of a thin material such as the above-mentioned Fe—Ni alloy steel strip for use in a thin plate for an electronic material or the like, the residual stress generated by temper rolling is removed to relatively reduce the thickness. When the plate shape defect is corrected by applying a large transport tension and tension annealing is performed to obtain a plate with good flatness, the longitudinal tension becomes unbalanced at the width position of the plate. In the vertical annealing furnace, a long free span is further formed between the inlet outer roll below the annealing furnace and the outlet outer roll above, and the thermal stress caused by the heating and cooling treatment in this free span. Is added to the strip. As a result, the strip after heat treatment has a corrugated shape. In this way, a corrugated shape is generated in the Fe—Ni alloy steel strip.

FIGS. 4 and 5 show examples of the shape of the strip corrugated sheet thus generated. FIG. 4 shows a schematic shape of the corrugated plate viewed in a cross section in the width direction of the strip, and shows a case where there is one curve, and FIG. 5 shows a case where there are two curves.
Here, h ₁ , h ₂ , and h ₃ are called bending amounts.

[0008] On the other hand, Japanese Patent Publication No. 15615/1990 discloses a method for preventing bending in the width direction of a metal strip.
In a vertical furnace having a heating zone and a cooling zone, the tension of the strip was adjusted to a low tension within the range of 0.1 to 1.5 kg / mm ² , and the strip temperature was 200 in the cooling zone.
Three or more rolls are provided at a position where the temperature falls to within the range of ~ 700 ° C, and the roll is used to push the strip into the
A method for producing a bend having a radius of curvature in the range of ~ 15000 mm, by adjusting the roll diameter and the roll arrangement to conditions in which the radius of curvature is obtained and material deformation does not easily occur in the strip. A technique for annealing steel strip (hereinafter referred to as prior art) is disclosed.

[0009]

As described above, according to the prior art method of performing tension annealing while applying a high tension to a strip, in the case of a thin and wide strip, a new plate is formed in a tension annealing step. Curvature in the width direction occurs, and the corrugated plate is likely to be formed. Particularly, when a strip material having a high required flatness is annealed, there is a problem that a sufficiently satisfactory flatness cannot be obtained.

On the other hand, according to the prior art described above, the strip is conveyed with a low tension in the vertical annealing furnace, and the cooling capacity in the cooling zone width direction in the furnace is controlled to be uniform. Since the thermal stress generated in the process is suppressed, it is possible to suppress the longitudinal tension from becoming unbalanced at the width position of the plate, and therefore, even when performing annealing treatment on a thin wide strip, a new plate is newly set in the annealing furnace. There is an advantage that it is possible to prevent a corrugated shape curved in the width direction.

However, in order to manufacture a plate which is required to have a small thickness and a particularly excellent flatness as used in a shadow mask for a cathode ray tube manufactured from an Fe--Ni alloy steel strip, Since it is necessary to prevent the bending in the width direction of the sheet during annealing of the material and to correct uneven distortion such as middle elongation and ear waves formed on the sheet before annealing, as in the prior art, The annealing method with low tension load cannot be applied. That is, in order to produce a thin Fe-Ni alloy steel strip having a small thickness and a wide width, particularly, a sheet having excellent flatness, it is necessary to add the above-described prior art to the above-mentioned prior art by forming the strip into a strip before the stress relief annealing. It is necessary to add a new technology for uniformly correcting uneven plate longitudinal distortion at the width position of the plate.

[0012] Accordingly, an object of the present invention is to provide a stress relief annealing, which is an original purpose, using a vertical type stress relief annealing furnace, and to dispose a strip in a longitudinal direction already formed on a strip before charging the annealing furnace. It is possible to remove the non-uniformity in the width direction of the plate, correct the plate shape, and produce a new plate shape defect in the annealing furnace, thereby producing a strip having an excellent plate shape. To develop technologies that The object of the present invention is to solve the above-mentioned problem, and thereby, by a tension annealing heat treatment method, there is no bending in the width direction of the plate such as a corrugated plate, and the longitudinal distortion of the plate such as middle elongation and ear waves is reduced. An object of the present invention is to provide an annealing method and an annealing apparatus for producing a thin Fe-Ni alloy steel strip having a good flatness and a small thickness without any difference due to the width position.

[0013]

Means for Solving the Problems The present inventors have proposed Fe-N
In order to remove the non-uniformity in the sheet width direction of the plate longitudinal strain already formed by temper rolling on the i-alloy steel strip, it is necessary to increase the transport tension in the vertical annealing furnace. It was a precondition. However, when the non-uniformity is slight, it is not essential to increase the transport tension. Then, a combination condition of the transporting tension of the strip and the heating temperature is appropriately selected to correct the curvature in the plate width direction. At this time, in particular, if the position for restraining the in-furnace strip in the plate width direction and the restraining force of the strip in the plate width direction are appropriately selected, a new shape of the plate can be formed in the furnace even if the transport tension is increased. It has been found that there is a condition capable of correcting the distortion of the plate before annealing without causing defects and obtaining a desired excellent plate-shaped strip.

The present invention has been made based on the above-mentioned findings, and has the following features. The annealing method according to claim 1 is a method of annealing a Fe—Ni alloy steel strip using a vertical annealing furnace having a heating zone and a cooling zone, wherein the following conditions (1) to (5) are satisfied. The method is characterized in that the Fe-Ni alloy steel strip is heated and cooled. (1) Heat the Fe-Ni alloy steel strip at a temperature below its recrystallization temperature and then cool. (2) At least three rolls adjacent to each other at right angles to the longitudinal direction of the strip are provided on the entry side in the cooling zone, and the rolls are used to alternately push the surface of the strip in opposite directions, thereby constraining the strip in the sheet width direction. Load force. (3) The radius of curvature of the strip pressed in step (2) is 2 at least at one position between the rolls.
The restraining force is adjusted by adjusting at least one of the distance between the rolls and the pushing amount so as to fall within the range of 500 to 5000 mm. (4) The temperature of the strip at the position where the binding force is applied in the step (2) is adjusted within the range of 200 to 500 ° C. (5) The transfer tension of the strip in the annealing furnace is 0.1
Adjust within the range of ２０20 kg / mm ² .

According to a second aspect of the present invention, there is provided the annealing method according to the first aspect.
The transporting tension of the strip in the step (5) is 0.1
In the range of ２０20 kg / mm ² , the value is determined according to the shape of the strip before entering the annealing furnace, and the shape of the strip is corrected.

According to a third aspect of the present invention, there is provided the annealing method according to the first aspect.
Alternatively, in the invention described in Item 2, the maximum heating temperature of the Fe-Ni alloy steel strip is set in a range of 500 to 700 ° C.

According to a fourth aspect of the present invention, in the annealing apparatus for an Fe—Ni alloy steel strip provided with a heating zone and a cooling zone, the annealing furnace is a vertical furnace.
It is characterized by having the mechanism of (4). (1) Three or more rolls close to each other, provided on the entry side in the cooling zone along the transport direction of the strip and with their axes directed perpendicular to the transport direction. (2) The strip surface is alternately pushed in opposite directions by the rolls of the above step (1), and the radius of curvature of the strip thus pushed is adjusted so that the radius of curvature of at least one portion between the rolls is in the range of 2500 to 5000 mm. The roll pushing amount adjustment mechanism. (3) A temperature control mechanism for the in-furnace strip that adjusts the material temperature of the strip in the heating zone and the cooling zone of the annealing furnace. (4) A transport tension adjusting mechanism for the strip in the furnace, which adjusts the transport tension of the strip in the vertical furnace within a range of 0.1 to 20 kg / mm ² .

[0018]

Next, the present invention will be described with reference to the drawings. FIG. 1 shows an example of an annealing apparatus according to the present invention, and is a schematic vertical sectional view of a vertical annealing apparatus for performing stress relief annealing while correcting the shape of an Fe—Ni alloy steel strip. 1 is a strip of Fe-Ni alloy steel, 2 is a heating zone, 3 is a cooling zone, and 4 is a roll. The strip 1 is conveyed in a vertical annealing furnace 5 while applying a required tension from below to above. The strip 1 is heated in the heating zone 2 at a temperature equal to or lower than the recrystallization temperature to remove the residual stress, reach the yield temperature, and correct the plate shape by the transport tension applied to the strip 1. The support positions of the strip 1 in the annealing furnace 5 are only the roll 4 provided on the entrance side in the cooling zone 3 and the in-furnace roll 7 near the outlet in the cooling zone 3. Hereinafter, the configuration and function of the annealing apparatus will be described.

(1) FIG. 2 is a schematic vertical sectional view showing the arrangement of the rolls 4 provided on the entrance side in the cooling zone.
This is a case where three rolls are provided. In the same drawing, the lower right roll 4a pushes the right surface of the strip 1 leftward, the middle roll 4b pushes the left surface of the strip 1 rightward, and the upper roll 4c pushes the right surface of the strip leftward. Press In the figure, d indicates the roll pushing amount. The roll 4 is pushed in by a hydraulic or pneumatic type or an electric load device, and the pushing amount d is controlled by a pushing amount adjusting mechanism (reference numeral 8 in FIG. 1).

(2) The strip 1 is rolled into the roll 4
To apply a restraining force to the strip 1 in the plate width direction. By applying a tension equal to or more than a predetermined value to the strip 1 while the strip 1 is constrained in the width direction, strain is applied in the longitudinal direction of the strip. However,
The magnitude of the strain given by the tension differs depending on the position in the plate width direction. That is, the magnitude of the strain applied here depends on the strain distribution in the strip width direction that has already been formed on the strip 1 before the strain is applied, and after the above-described tension load, the strain in the strip width direction is changed. It is intended to make the distribution uniform.

(3) In the present invention, the transport tension is set at 0.
The reason for limiting to a wide range from low tension of 1 to ²⁰ kg / mm ² to high tension will be described. For the above-mentioned reason, the application of a new strain in the longitudinal direction to the strip in the annealing furnace is performed by applying a tension equal to or more than a predetermined value in the heating zone by the transport tension adjusting mechanism (reference numeral 9 in FIG. 1). .

(A) Here, it is necessary to correct the plate shape
Tension σ_reformFind the value of Fig. 3 shows the required shape correction
Transfer tension σ_reformFIG. 4 is a schematic diagram for finding the minimum value of. Board
Tension σ required for shape correction_reformIs the strip temperature T
_stStress σ of strip determined by_yLarger than
Is necessary. Strip temperature T_stAnd its temperature
Yield stress of strip at σ_yBetween the
Top temperature T_stThe yield stress of the strip σ_y
Has a decreasing relationship (σ in FIG._y= F (T_st)). one
On the other hand, the heating temperature of the strip should be lower than the recrystallization temperature.
Ni-Fe alloy steel (Ni: 30 to 50)
wt.%), the maximum heating temperature is in the range of 500 to 700 ° C.
I do. Therefore, if the loaded σ_reformThe length of the plate
Assuming that the hand tension is completely uniform at the width position
Should be loaded on the strip to correct the plate shape
Tension σ_reformIs the strip temperature T_stIs the highest heating temperature
Stress σ of strip at 700 ° C_{y, 700}that's all
And it is sufficient. But in practice, the loaded σ_reformTo
The longitudinal tension of the plate shows a certain tension distribution in the width direction.
The mechanism of forming and correcting the actual plate shape is the strip
Yield stress σ _yCorrection by plastic deformation from the position beyond
Since the positive progresses, the transport tension is σ_{y, 700}than
Small value (σ '_reformThe shape correction is possible in ()). However
And, when trying to correct the shape over a wide range of plate width,
It is effective to increase the transport tension.

On the other hand, if the restraining force of the roll in the sheet width direction is not increased as the transport tension increases, the distortion after correction cannot be made uniform in the sheet width direction. In order to increase the restraining force, the radius of curvature of the strip due to the pressing of the roll must be reduced. However, if the radius of curvature is made too small, there is a problem in that the sheet is drawn by a roll. On the other hand, if the transport tension is excessively increased, not only the correction of the corrugated sheet shape, but also the sheet thickness decreases. To solve these problems, the transport tension is 20 kg / m
It has been found that it is sufficient to limit it to m ² or less.

(B) By the way, the strain distribution in the longitudinal direction of the strip before treatment in the annealing furnace with respect to the width position of the plate is almost uniform, and the strip has a good plate shape that requires almost no correction. In some cases. In such a case, the transport tension may achieve the original purpose of transporting the strip. The transport tension for this is 0.1 kg /
mm ² or more is required.

In the present invention, even if the degree of deformation of the plate before annealing varies to various levels, the strip can be continuously and efficiently annealed by determining the transport tension according to the degree of deformation. There is a big feature in the point that it becomes possible. Therefore, as a condition satisfying the above (a) and (b), it is desirable that the transport tension is adjusted within a range of 0.1 to 20 kg / mm ² . Therefore, it is necessary that the transport tension adjusting mechanism (FIG. 1, reference numeral 9) can adjust the strip tension within the above range.

The maximum heating temperature is set to 500-70.
The reason for setting the temperature within the range of 0 ° C. is as follows. When performing stress relief annealing of a Ni-Fe alloy steel strip having a Ni content of 30 to 40 wt.%, It is necessary to set the temperature to 700 ° C. or lower because mechanical properties such as softening due to recrystallization are not significantly changed. Further, it is necessary to secure 500 ° C. or more for the main purpose of removing stress.

(4) Next, the reason why the radius of curvature of the strip by pressing the roll is limited to the range of 2500 to 5000 mm will be described. In order to apply the above-described appropriate correction strain to the strip, it is necessary to apply an appropriate transport tension to the strip while applying an appropriate restraining force to the strip in the plate width direction as described above. . The inventor of the present invention has determined that the appropriate strip restraining force is that when the number of the rolls 4 is three or more, the strip 1 is pushed in an appropriate amount by a pushing amount adjusting mechanism (reference numeral 8 in FIG. 1), and the radius of curvature formed in the strip 1 is increased. It has been found that by appropriately selecting R (see FIG. 2), it can be achieved without damaging the plate shape. That is, the smaller the radius of curvature R is, the larger the strip restraining force is. However, if the radius R is less than 2500 mm, a so-called plate drawing occurs when the strip 1 passes over the roll 4 and impairs the plate shape. On the other hand, as the radius of curvature R increases, the strip restraining force decreases,
When R is 5000 mm or more, the restraining force becomes too small, and a bending in the width direction of the sheet is newly generated due to the transport tension, and the flatness targeted by the present invention is not satisfied. Here, of the plate flatness, the amount of curvature h _{1 of} the corrugated plate in the plate width direction,
The target values of h ₂ and h ₃ (see FIGS. 4 and 5) were set to 4 mm or less.

Then, in order to obtain the radius of curvature R,
According to the experimental results, when the number of rolls is 2 or less, it is difficult for the strip 1 to take a meandering movement path, and R = 25
It cannot be secured within the range of 00 to 5000 mm. If the number of rolls is three or more, there is no problem in securing the curvature radius.

As described above, the radius of curvature R of the strip 1 is adjusted within an appropriate range. The curvature radius R
Is experimentally obtained from the roll interval s and the roll pressing amount d described above, for example.

(5) The installation position of the roll for restraining the strip in the width direction will be described. Strip 1
The roll 4 for restraining the roll in the width direction requires a large amount of cost for manufacturing and installing a roll capable of withstanding high temperatures when provided in the heating zone, and the surface of the strip is easily scratched by the contact between the roll and the strip. Should be avoided. On the other hand, if the roll 4 is provided in the cooling zone, the problem can be easily solved. Further, it is necessary to set the heating zone in the heating zone so that the strip temperature at the position is set to 500 ° C. or lower, or the strip temperature at the position is set to 500 ° C. or lower. If the cooling conditions in the cooling zone are further adjusted according to the above, the above-mentioned problem of the equipment concerning the roll can be solved. However, as the position of the roll 4 is further away from the inlet of the cooling zone and closer to the outlet, the free span of the strip from the inlet of the heating zone in the annealing furnace becomes longer, so that the roll 4 restrains the strip in the width direction of the strip. Disadvantaged above. That is, in this case, the radius of curvature R of the strip must be reduced to increase the restraining force on the strip, and plate drawing is likely to occur.

If the lower limit of the strip temperature at the roll 4 installation position is 200 ° C. or higher, there is no problem with the temperature obtained in actual operation, and there is no particular limitation. However, in normal operation, unless the cooling rate after the end of heating is abnormally increased, the temperature will eventually be about 200 ° C. or more.

From the above, the installation position of the roll 4 is as follows.
On the inlet side in the cooling zone, a space in the furnace is secured so that the strip temperature at that position can be adjusted to 500 ° C. or less and the radius of curvature of the strip can be adjusted within the range of 2500 to 5000 mm as described above. It is desirable to be as close as possible to the inlet of the cooling zone, provided that it is possible. It is more effective to move the roll 4 to a position having a more restrictive force.

(6) The greatest feature of the present invention is that the roll 4
The radius of curvature of the strip according to
And the transfer tension is up to 20k.
g / mm ² , which is a combination technology with the method of transporting with high tension, and properly combining the roll installation position and the number of rolls with the strip temperature conditions at the roll installation position of the heating zone. Accordingly, even if the strip shape is corrected by applying a high tension to the strip, the intended purpose can be achieved without damaging the plate shape on the other hand.

[0034]

Next, the present invention will be described in more detail with reference to examples. The following tests were performed based on the above-described embodiment.

The thicknesses of 0.12 mm and 0.25 mm2
A temper-rolled strip of 36 wt.% Ni alloy steel having a sheet width of 880 mm was subjected to annealing for removing residual stress at a maximum temperature of the strip of about 550 ° C. to correct the sheet shape. The annealing furnace used was the same vertical furnace as that shown in FIG. 1, and three rolls were installed near the entrance in the cooling zone. However, as a comparative example outside the scope of the present invention, a test in which two rolls were installed was also performed.

The temperature of the strip at the roll setting position was about 350 ° C. 3 or 2 roll interval s
Were all 330 mm, and the roll pressing amount d was variously changed to adjust the radius of curvature R of the strip so as to be a predetermined value within and outside the range of the present invention. Then, depending on the amount of bending in the width direction of the strip before removing the residual stress, the in-furnace transfer tension is set to five levels (0.2, 1.5, 4, 10, and 10) in the range of 0.2 to 15 kg / mm ^2. 15 kg / mm ² ).

Under the above test conditions, the strip was subjected to annealing for removing residual stress, and the shape of the plate was corrected. In Table 1,
The test conditions of Examples 1 to 7 satisfying the conditions within the scope of the present invention and Comparative Examples 1 to 6 that are conditions outside the scope of the present invention are shown.

[0038]

[Table 1]

Next, test results will be described. As the plate shape of the strip, corrugated plate, middle elongation, plate drawing, and plate breakage were measured.

As shown in FIGS. 4 and 5, the corrugated shape of the strip before and after the annealing has one curved portion in the width direction of the plate and two curved portions in the transverse direction as shown in FIGS. There was. As shown in each of FIGS. 4 and 5, the maximum values h ₁ and h ₁ and h ₂ of the amount of curvature, which are gaps between the strip 1 and the horizontal platen 10, were measured. FIG.
When there are two bends as in the above, the larger value of the bend amount is determined as the bend amount of the strip. The above-mentioned amount of curvature was used as the evaluation characteristic of the plate wave, and those having a bending amount of 4 mm or less were accepted.

The median steepness of the strip was measured before and after annealing. FIG. 6 is an explanatory diagram of the middle elongation steepness. The steepness λ is defined as λ = (a / p) × 100% from the wave height a and the pitch p in the plate longitudinal section in the middle elongation portion.
The medium growth steepness was determined to be acceptable when λ ≦ 0.5%.

Further, the strip was inspected for sheet drawing and occurrence of sheet breakage. Then, as the evaluation of the strip plate shape, a strip which passed both the amount of bending and the steepness of the middle elongation and in which neither the plate drawing nor the plate breaking occurred was evaluated as good in the comprehensive evaluation, and was marked with ○, and the above evaluation Strips in which even one of the characteristics was unacceptable were evaluated as poor in the overall evaluation and indicated by x.

The test results are shown in Table 1. As can be seen from the above test results, Fe—Ni after stress relief annealing accompanied with shape correction performed by the methods of Examples 1 to 7
As the alloy steel strip, a good one that achieved the target for the plate shape was obtained. On the other hand, in the methods of Comparative Examples 1 to 6, even if stress relief annealing accompanied with shape correction is performed,
The target for the plate shape was not achieved, and a good Fe-Ni alloy steel strip could not be obtained.

[0044]

As described above, according to the present invention,
The stress remaining in the Fe-Ni alloy steel strip after the temper rolling is removed, and the uneven shape formed by the temper rolling is uniformed to correct the sheet shape, thereby causing sheet drawing and sheet bending. It is possible to inexpensively manufacture a strip having excellent flatness, which has improved middle elongation and ear waves without accompanying the above, and has a good corrugated sheet shape and suppressed curvature in the board width direction. Such an annealing method and an annealing apparatus can be provided, and an industrially useful effect is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view showing an example of a vertical annealing apparatus according to the present invention.

FIG. 2 is a detailed view of an arrangement of rolls provided on an entrance side in the cooling zone of FIG. 1;

FIG. 3 is a strip transfer tension σ required for plate shape correction.
It is a schematic diagram which calculates | _requires the minimum value of _reform .

FIG. 4 is a schematic cross-sectional shape in the direction C when the strip has one curvature in the plate width direction.

FIG. 5 is a schematic cross-sectional shape in the C direction when the strip has two curvatures in the plate width direction.

FIG. 6 is an explanatory diagram of the middle stretch steepness of the strip.

[Explanation of symbols]

1 strip 2 heating zone 3 cooling zone 4, 4a, 4b, 4c roll 5 annealing furnace 6 annealing device 7 near the outlet furnace rolls 8, 8a, 8b, 8c push amount adjusting mechanism 9 conveying tension adjusting mechanism 10 plate h _1, h _2, h ₃ plate width direction of the bending amount d roll push amount D roll diameter R of curvature radius a crest p pitch

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Daisuke Ozaki 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (4)

[Claims] 1. A method of annealing a Fe—Ni alloy steel strip using a vertical annealing furnace having a heating zone and a cooling zone, wherein the Fe—Ni alloy steel strip is subjected to the following steps (1) to (5). An annealing method with shape correction of an Fe-Ni alloy steel strip, comprising heating and cooling the Ni alloy steel strip. (1) Heating the Fe-Ni alloy steel strip at a temperature below its recrystallization temperature and then cooling. (2) At least three rolls adjacent to each other at right angles to the longitudinal direction of the strip are provided on the entrance side in the cooling zone, and the rolls are used to alternately push the surface of the strip in the opposite direction, and the strip width is applied to the strip. Apply directional restraint. (3) At least one of the distance between the rolls and the amount of pressing so that the radius of curvature of the strip pressed in the step (2) is within a range of 2500 to 5000 mm at at least one position between the rolls. Is adjusted to adjust the binding force. (4) The temperature of the strip at the position where the binding force is applied in the step (2) is adjusted within the range of 200 to 500 ° C. (5) Adjust the transport tension of the strip in the annealing furnace within a range of 0.1 to 20 kg / mm ² . 2. The transporting tension of the strip in the step (5) of claim 1 is within a range of 0.1 to 20 kg / mm ² depending on the shape of the strip before entering the annealing furnace. The annealing method with shape correction of an Fe-Ni alloy steel strip according to claim 1, wherein the value is determined. 3. The shape correction of the Fe—Ni alloy steel strip according to claim 1, wherein the maximum heating temperature of the Fe—Ni alloy steel strip is performed in a range of 500 to 700 ° C. Accompanying annealing method. 4. An annealing furnace for a Fe—Ni alloy steel strip provided with a heating zone and a cooling zone, wherein the annealing furnace is a vertical furnace and has the following mechanisms (1) to (4). An annealing apparatus with shape correction of an Fe-Ni alloy steel strip, characterized in that: (1) Three or more rolls close to each other, which are provided on the entry side in the cooling zone along the transport direction of the strip and oriented in the direction perpendicular to the transport direction. (2) The strip surface is alternately pushed in the opposite direction by the roll of (1) so that the radius of curvature of the strip thus pushed is within the range of 2500 to 5000 mm at at least one location between the rolls. A roll pushing amount adjustment mechanism that adjusts. (3) A temperature control mechanism for the strip in the furnace, which controls the material temperature of the strip in the heating zone and the cooling zone of the annealing furnace. (4) A mechanism for adjusting the transport tension of the strip in the furnace, which adjusts the transport tension of the strip in the vertical furnace within a range of 0.1 to 20 kg / mm ² .