JP2955420B2 - Method and apparatus for producing ultra-thin stainless steel strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an ultra-thin stainless steel strip having a thickness of 0.3 mm or less which is cold
The present invention relates to a method and an apparatus for manufacturing an ultra-thin stainless steel strip to be annealed in a continuous annealing furnace having the above free span.

[0002]

2. Description of the Related Art In the process of manufacturing a stainless steel strip, cold rolling (hereinafter referred to as rolling) is a step of finishing a sheet thickness to a predetermined thickness. And secondary processing is difficult as it is. Therefore, in order to soften the material, heat treatment is performed by heating and cooling in a continuous annealing furnace (hereinafter referred to as an annealing furnace) which is a post-rolling process. As a heat treatment other than annealing, stress relief, age hardening, and the like may be performed. Here, annealing is mainly described.

[0003] In general, stainless steels are roughly classified into ferritic and austenitic stainless steels, each having an annealing temperature of about 7 ° C.
It is in the range of 50-1000C, about 1000-1100C. From the difference in temperature, wrinkles often occur empirically in the latter, particularly in an ultrathin stainless steel strip having a thickness of 0.3 mm or less.

There are two types of annealing furnaces, a horizontal type and a vertical type. In the horizontal type furnace, as shown in FIG.
Although it is sent on several hearth rolls 2 provided at every 13 m pitch, in the vertical furnace shown in FIGS. 16 and 17, there is no hearth roll in the heating zone 3 and the subsequent cooling zone 4. Often. The furnaces shown in FIGS. 16 and 17 are bright annealing furnaces. FIG. 16 shows an example in which heating and cooling are performed in a down pass, and FIG. 17 shows an example in which heating and cooling are performed in an up pass. The furnace body is substantially inverted U-shaped, and the inside of the steel strip 1 is filled with a blend gas of hydrogen gas and nitrogen gas to prevent scale from being generated on the surface of the heated steel strip 1. At the inlet 5 and the outlet 6 are provided roll sealing means 7 and 8 for preventing leakage of the gas. In the upper furnace, there is a top roll 9 and an inlet 5
And the distance between the outlet 6 and each top roll 9 is 15 to 5
0 m, and despite the fact that the free span is very long, in order to prevent scratches on the surface of the steel strip, a hearth roll is not provided between them in many cases. As shown by the imaginary line 10, in many cases, only one pair is provided between the heating zone 3 and the cooling zone 4.

FIG. 18 is a sectional view showing a direct-fired annealing furnace. Since the steel strip 1 is heated in the waste gas atmosphere of the burner 11, and cooling is performed by air cooling or injected water, scale is generated on the steel strip surface, and descale is required as post-treatment. Although not shown in the drawings, other annealing furnaces for heating with a radiant tube are well known.

[0006]

As in the above prior art, in a horizontal furnace and a vertical furnace having a long free span,
When passing a so-called ultra-thin steel strip having a thickness of 0.3 mm or less, wrinkles are likely to occur in the steel strip. To prevent this,
Known methods include avoiding quenching, strongly cooling the center of the sheet width, and adjusting the hearth roll crown.Either method completely prevents the occurrence of wrinkles in the steel strip. Can not do. When such wrinkles occur, the commercial value of the stainless steel strip is completely lost, and the production cost of each process required for rolling to ultra-thin is in spite of being more expensive than products of general thickness In addition, when heat treatment of an ultra-thin steel strip, there is a large problem in production, such as a technician having to attend the cooling adjustment work.

[0007] The present inventor, as a result of earnest research, has solved the above-mentioned problems and found that wrinkles can be completely prevented by controlling the shape of the steel strip before heat treatment. That is, a stainless steel strip cold-rolled to a thickness of 0.3 mm or less tends to wrinkle when annealed in an annealing furnace having a free span of 15 m or more. As a result of repeating the board test,
It has been found that when the shape of the ear elongation or the quarter elongation is realized by the rolling, the wrinkle is always remarkable.

Accordingly, it is an object of the present invention to produce a high quality stainless steel strip by reliably preventing wrinkles from being generated in the annealed stainless steel strip and improving the shape of the annealed ultrathin stainless steel strip. It is an object of the present invention to provide a method and an apparatus for manufacturing a steel strip that can be used.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a continuous annealing furnace having an uncontacted or unconstrained free span of at least 15 m or more over a stainless steel strip cold-rolled to a thickness of 0.3 mm or less by a rolling mill. In the method for producing an ultra-thin stainless steel strip which is annealed by the method, the rolling mill is feedback-controlled based on the shape of the stainless steel strip immediately after the cold rolling so that the stainless steel strip has a medium elongation. A method for producing an ultra-thin stainless steel strip, characterized by adjusting the rolling tension of the stainless steel strip.

In the present invention, the steepness of the middle elongation is determined by:
0.2 to 2%.

Further, the present invention is characterized in that the difference in elongation percentage of the middle elongation is 1 × 10 ⁻⁵ to 1 × 10 ⁻³ .

Further, the present invention provides a rolling mill for cold-rolling a stainless steel strip to a thickness of 0.3 mm or less, and a free span in which the passed stainless steel strip is not contacted or unconstrained for at least 15 m or more. 0.3mm thickness
A continuous annealing furnace for annealing the cold-rolled stainless steel strip below, in a manufacturing apparatus for an ultra-thin stainless steel strip, disposed in close proximity to the exit side of the rolling mill, the cold-rolled stainless steel strip Means for detecting the elongation difference distribution in the width direction of the steel strip; calculating means for calculating the steepness based on the output from the elongation difference distribution detecting means; and steepness determined by the calculating means. Display means for displaying an image as a distribution on the surface of the stainless steel strip, and control means for controlling the rolling force of the rolling mill in response to the output from the arithmetic means so that the stainless steel strip has a middle elongation. And a production apparatus for an ultra-thin stainless steel strip.

[0013]

According to the present invention, the shape of a stainless steel strip cold-rolled to a thickness of 0.3 mm or less is detected by a detecting means such as a hollow multi-split roll method. Based on the shape, the rolling mill is feedback-controlled so that the stainless steel strip has a middle elongation, and the rolling tension of the stainless steel strip is adjusted, whereby the generation of wrinkles after annealing can be reliably prevented. In controlling the rolling mill so that the stainless steel strip has a medium elongation, the steepness of the medium elongation is set to 0.2 to 2
%, Or the difference in elongation during medium elongation is 1 × 10 ^-5
By setting it to 1 × 10 ⁻³ , generation of wrinkles after annealing can be more reliably prevented.

According to the invention, the stainless steel strip is cold-rolled to a thickness of 0.3 mm or less by a rolling mill.
Means for detecting the elongation difference distribution close to the exit side of the rolling mill during continuous annealing in an annealing furnace having a free span in which a roll or the like does not contact or restrain the stainless steel strip for more than m. Is provided, the distribution of the elongation difference in the width direction of the stainless steel strip after cold rolling is detected by the detection means, and the steepness is calculated by the calculation means based on the output from the detection means, The steepness on the surface of the stainless steel strip is image-displayed by the display means so that the operator can visually recognize the shape of the stainless steel strip after passing the rolling mill, and responds to the output from the arithmetic means by the control means. Thus, it is possible to control the rolling force of the rolling mill so that the stainless steel strip has a middle elongation, thereby preventing the stainless steel strip from wrinkling after annealing.

[0015]

FIG. 1 is an overall system diagram for explaining an embodiment of the present invention. For example, in order to manufacture injection needles, composite resin panels, communication cable sheath tubes, clad pipe materials, etc., annealed stainless steel strips having a thickness of 0.3 mm or less have been used.
Orders for ultra-thin products of about 1 mm are increasing. In manufacturing such an ultra-thin stainless steel strip, the sheet is passed through a cold rolling mill 20 to perform cold rolling, and then an annealing process is performed in an annealing furnace 21.

As the cold rolling mill 20, for example, a single stand levers type 12-stage Christer mill capable of automatic shape control is used. The rolling mill 20 includes a pair of upper and lower work rolls 22a and 22b,
It has intermediate rolls 23a and 23b that support 2a and 22b, and backup rolls 24a and 24b that support each intermediate roll 23a and 23b. The lower backup roll 24b is supported by a pair of left and right pressing means 25a and 25b having a hydraulic cylinder and the like, and can adjust the pressing force of the stainless steel strip 26 passed between the work rolls 22a and 22b. It is configured to be able to.

The annealing furnace 21 is a vertical bright annealing furnace, and its furnace body is formed substantially in an inverted U shape. A pair of roll seal means 29 and 30 are provided at an inlet 27 and an outlet 28 in the passing direction of the furnace body, respectively, and a hydrogen gas or the like for preventing generation of scale filled in the furnace body is provided. The airtightness inside the furnace is maintained so as not to leak. Top rolls 31 and 32 are provided on the upper part of the furnace body.
The distance between the roll seal means 29 and the top roll 31 on the entrance side and the distance between the roll seal means 20 and the top roll 32 on the exit side are 15 to 5 respectively.
By providing such a free span of 15 m or more, it is possible to prevent the surface of the stainless steel strip to be passed from being damaged.

On the exit side of the cold rolling mill 20, there is provided a shape detecting roll 33 which is a means for detecting a difference in the elongation ratio in the width direction of the passed stainless steel strip 26.
As the shape detecting roll 33, a magnetostrictive load detector as shown in the perspective view of FIG. 2 and the sectional view of FIG. 3 is used. The shape detection roll 33 is, for example, 2
A plurality of contact rings 34 having a width of about 6 to 52 mm
And a plurality of (four in this embodiment) strain gauges 35 provided in the circumferential direction to detect distortion of the contact ring 34, and when the stainless steel strip 26 passes, the contact ring 3
4, a radial load of 1250 kgf (in the case of a width of 52 mm) can be detected.

The output from the shape detecting roll 33 is input to a monitor 36, and the unevenness of the stainless steel strip 26 in the width direction is displayed as an image. Also, the shape detection roll 33
Is input to the calculating means 37, and is decomposed into linear, quadratic and quartic functions. Indices are calculated as steepnesses λ2 and λ4 corresponding to quadratic and quartic functions, respectively, and these are displayed on the display means 38. Is displayed on a plane image of the stainless steel strip 26, and the steepness λ calculated by the arithmetic means 37 is displayed.
2, .lambda.4 are input to the control means 39 to adjust the crown for the backup rolls 24a and 24b, and to adjust the intermediate rolls 23a and 23b and the work rolls 22a and 22b.
The bending is adjusted for the pressure reduction means 25a, 2
5b is controlled as adjustment of the rolling reduction. The calculation method in the calculation means 37 will be described below.

(1) Elongation of Rolling A steel strip having an original length L 'and a thickness t' is rolled to have a length L,
FIG. 4 shows a state in which the thickness t has been reached. If there is no change in the width w, the following equation holds.

[0021]

L ′ × t ′ = L × t∴t ′ / t = L / L ′ The ratio of the extended length (L−L ′) to the original length L ′ is:
The elongation ε by rolling.

[0022]

Ε = (L−L ′) / L ′ = L / L′−1 = t ′ / t−1 Therefore, the length L and the thickness t after rolling and the elongation ε of rolling are given by the following equations. Become a relationship.

[0023]

L = L ′ × (1 + ε) t = t ′ / (1 + ε) This clearly indicates that the larger the elongation ε of the rolling, the longer the sheet and the thinner the sheet.

(2) Rolling rate In the rolling operation of the steel strip, it is easier to measure the sheet thicknesses t 'and t than the sheet lengths L' and L, and the rolling elongation ε.
In general, the following ratio is used as the rolling ratio γ.

[0025]

Γ = (t′−t) / t ′ = 1−t / t′∴t = t ′ × (1−γ) Therefore, ε and γ have the following relationship.

[0026]

## EQU5 ## t / t '= 1-.gamma..epsilon. = T' / t-1 = 1 / (1-.gamma.)-1 = .gamma ./ (1-.gamma.) / 1 / .epsilon. = (1-.gamma.) /. Gamma. = 1 / γ-1 １ ／ 1 / γ = 1 / ε + 1 = (1 + ε) / ε γ = ε / (1 + ε) (3) Steepness of steel strip The steel strip when shipped as a product can be as flat as possible. However, the rolled steel strip is not necessarily completely flat, and when a length L is cut out and placed on a flat plate, the strip elongates as shown in FIG. There are various types such as ear growth as shown in FIG. (B) and quarter growth as shown in FIG. For example, the width center cross section of the steel strip in FIG. 5A is wavy as shown in FIG. Assuming that the wave height is h and the wave period is p, the steel strip length is longer than p (p + dp). At this time, the following ratio is represented by the steepness λ as a measurable index indicating the degree of the shape defect.

[0027]

Λ = h / p As can be seen, a steel strip that is not flat means a steel strip whose steepness is not 0 and whose value is different in the width direction, as shown in FIGS. 5 (a) to 5 (c). The typical widthwise steepness distribution is shown in the lower part.

It is clear from the measurement method that the steepness value does not become negative.

[0029]

Λ ≧ 0 Now, the steepness of the as-rolled steel strip is generally less than 0.04, and most of it is less than about 0.02, ie less than about 2% in percentage, That is, when the wave period is 100 mm, the wave height is 2 mm, and when the wave period is 500 mm, the wave height is 10 mm. If the steepness is less than 0.005, that is, less than 0.5%, the shape looks almost good visually. On the other hand, if it is 0.5% or less, it is difficult to measure.

(4) Length distribution in the width direction As another measuring method of the shape defect, the following can be considered. As shown in FIGS. 7 (a) and 7 (b), if this plate is cut in the longitudinal direction, dL appears with a difference in length as shown in the middle row. That is, the defective shape is interpreted as follows. In other words, even before the stripping, the length of the central portion was longer than both ends in the width direction, so that the central portion was subjected to compressive stress by both ends in the width direction, and both ends in the width direction were subjected to tensile stress by the central portion. However, the center is deformed out of plane. In other words, by not being flat,
Both ends and the central part released the stress.

Then, a case where the shape is considerably defective is taken up next, and as shown in FIG. 7 (a), it is assumed that both ends in the width direction are straight and the center is a sine curve with a steepness of 2%. If the length difference ratio dL / L is considered, it is the same value as dp / p in the above item (3), and is given geometrically by the following approximate expression.

[0032]

DL / L = dp / p = (π / 2) ² × (h / p) ² = 2.47 × λ ² = 2.47 × 0.02 ² = 0.001 = 1 × 10 ^{− 3} That is, the steepness λ is 0.1%, and it can be seen that dL is extremely small as compared with L, although the medium elongation is remarkable visually.

The steepness of 4%, 0.
5% and 0.2% are 4 × 10
⁻³ , 6 × 10 ⁻⁵ , 1 × 10 ⁻⁵ .

Therefore, in addition to the necessity of such a stripping operation, it is very difficult to measure a very small length, so that the measurement of the steepness λ is more realistic.

In the above example, λ is 2% and dL / L is 0.1%
Therefore, dL / L is λ as a value detected by the measurement.
1/20. That is, the introduction of λ was also a means for exaggerating the minute dL and facilitating the measurement.

FIGS. 7A and 7B show the distribution of dL / L in the width direction at the lower stage. It is clear that the value does not become negative.

(5) Elongation difference The "ratio of length difference dL to length L before cutting" discussed in the preceding section (4) is referred to as elongation difference de.

[0038]

De = dL / L∴dL = de × L The reason why the de is referred to as the difference in elongation is hypothetical as follows: the elongation is obtained by pulling the center of a flat plate having a length L. This is because if a distortion of the difference de is given, a similar shape is obtained.

(6) Difference in Elongation of Rolling A description will be given of obtaining such a shape even if a flat shape is targeted by rolling. FIG. 9 shows the steel strip of L ′ × t ′ × w before the rolling in the preceding section (1) again, and it is considered that this was a flat plate material. Therefore, even if the material is rolled to give an elongation percentage ε to extend the length to L, the amount of the strain is slightly different in the width direction. At both ends in the width direction, it is ε, but at the center, (ε + d
ε), the length is L at both ends, but (L + dL) at the center. Length L at both ends
And the rolling ratio ε, as already described,

[0040]

L = L ′ × (1 + ε + dε), and at the center,

[0041]

L + dL = L'.times. (1 + .epsilon. + D.epsilon.) = L + L'.times.d.epsilon. DL = L'.times.d.epsilon. In addition, the virtual elongation rate difference d described in the previous section (5)
e has the following relationship.

[0042]

DL = L × de∴dε = (L / L ′) × de = (1 + ε) × de The elongation difference dε of this rolling is estimated, and the steel strip before the finishing pass of rolling is flat. The strain ε of the rolling in the finishing pass is 0.05, ie, 5%, and the steel strip after rolling has a steepness of 2%.
Assuming that the middle stretch, de was 0.001, so

[0043]

## EQU13 ## dε = (1 + ε) × de = (1 + 0.05) × 0.001 ≒ 0.001 In other words, it can be seen that a very small difference in elongation of rolling of about 0.1% leads to a remarkable shape defect. Here is the difficulty and importance of shape control of rolling.

As can be seen from the above, the difference in the elongation of the rolling in the width direction is different from that in the non-flat steel strip, but it is apparent that the difference also depends on the shape before rolling and the thickness distribution in the width direction. .

(7) Plate Thickness Distribution In FIGS. 8 (2) and 8 (3), the plate thickness is not described as t. The reason is that both ends are thinner than t even at the center (t−d
This is because t). However, the following can be said from the above item (2).

At both ends,

[0047]

T = t '× (1-γ) = t ′ × {1-ε / (1 + ε)} = t ′ / (1 + ε)

[0048]

T−dt = t ′ / (1 + ε + dε) However, in this numerator / denominator, d
Since ε is small compared to ε and (1 + ε), it can be ignored,

[0049]

T−dt１６t ′ ≒ (1 + ε) = t∴dt ≒ 0 After all, it can be considered that the plate thickness after rolling is t = constant.

(8) Correspondence between steepness and elongation rate difference Correspondence between steepness λ and elongation rate difference de mentioned in (4) above,
In other words, the correspondence between FIGS. 5 and 7 will be described.

[0051]

DL / L = dp / p = (π / 2) ² × (h / p) ² = 2.47 × λ ² ∴λ = (de / 2.47) ^1/2 The following two points described above are confirmed. First, since de is a value of 0.005 or less and less than 1, λ is increased by taking a route.
Second, λ and de are not negative.

Therefore, the λ distribution in FIG. 5 and the de distribution in FIG. 7 have similar shapes, and the unit of the vertical axis is the same as%, but they do not match even if the scale of the vertical axis is adjusted. However, once one distribution is measured, the other distribution can be calculated.

(9) Another method of measuring the difference in elongation The measurement of de by stripping described in (4) above is not always easy, but it is also possible to measure it according to the following principle. The plate material of FIG. 8 is elastically deformed by being pulled, and the length (L + d
(L + d2) is shown in FIG. 9 (2). Since the length of the original plate was not constant, the tension T for making it the above-mentioned constant length is not constant in the width direction. The center portion is extended by d2, and both end portions are extended by (dL + d2). Assuming that the Young's modulus E is constant in the width direction, according to Hooke's law, the tension TE at both ends is

[0054]

## EQU18 ## TE = E × (dL + d2) / L On the other hand, the tension TC at the center is

[0055]

## EQU19 ## TC = E × d2 / (L + dL) However, in this denominator, dL is small compared to L and can be ignored, and is approximated as follows.

[0056]

TC = E × d2 / L These tension distributions are shown in the lower part.

It is easy to understand if this tension is divided into the following two steps. First, it is extended by d2 over the entire width, the length of both ends is (L + d2), and the length of the center is (L + dL + d2). Next, extend only the both ends to make the entire length (L + dL + d
2) = Constant. The above approximation means that the tension required for the first stage can be regarded as constant in the width direction, and is indicated by a virtual line M in FIG. 9 (2). The added tension is required for the second stage.

From these, it can be seen that the tension T for elastically deforming and pulling to a certain length has a linear relationship with the length deviation dL in the width direction of the original plate. Therefore, if FIG. 9 (3) is turned upside down (drawing the distribution of −T) and the scale of the vertical axis and the position of the horizontal axis are adjusted, the unit is different, but a graph of FIG.
Can be matched.

Accordingly, the tension distribution for elastically deforming the plate material to a certain length can be measured, and it can be seen from the calculation that the de distribution and the λ distribution can be obtained therefrom.

(10) Elongation difference measuring device-shape detector.

As an apparatus for measuring the elongation difference de using the method (9), the shape detecting roll 33 as shown in FIGS. 1 to 3 is used as described above. In the preceding paragraph (9), a sheet material having a different length in the width direction was pulled to a certain length, but as shown in FIG.
The steel strip is stretched by rolling tension regardless of the shape,
The situation of the preceding paragraph (9) has been realized without care. As shown in FIG. 1, a plurality of split rings 34 are used as a shape detector.
3 to FIG. 3, the roll 33 is installed.

The tension reel 41 applies tension to the steel strip 26 while winding the steel strip 26, but does not cause plastic elongation. Then, the steel strip 26 attempts to push down the roll 33 with a force corresponding to the tension as shown in FIG. In the figure, the steel strip is drawn as if it were stripped. In the steel strip from which a shape defect is found when the tension is removed, a width direction tension distribution corresponding to the shape is generated, and each ring 34 detects the tension distribution.

In the roll arrangement corresponding to each bar graph in FIG. 11, the pass line in the rolling mill is horizontal, and the deflector roll 4 is located between the roll 33 and the tension reel 41.
Since there are 2 and 43, there is an advantage that the winding angle of the steel strip around the roll 33 is constant. Without the deflector roll, the rise of the pass line accompanying the thickening of the tension reel 41 by the steel strip 26 changes the winding angle θ of the steel strip around the shape detection roll 33 (see also FIG. 3), and the same tension is applied. Even if it is kept, there is a problem that the pressing force is reduced. However, a technique of detecting the pass line angle θ and correcting the same has also been generalized.

As described above, the only practical measurement of the conventional shape is to measure the steepness λ from the wave height and the period by placing the plate on a flat plate. The distribution of the tension T in a linear relationship with de can be continuously measured online, and the de distribution can be obtained through calculation processing.
It is also possible to obtain a λ distribution therefrom. Also,
A steepness of 0.2% or less, which was difficult to measure, can also be measured.

(11) Output example of shape detection roll The shape detection roll 3 used by the present inventors in a rolling mill
As an output example of No. 3, L1000 × W1000 × t174
FIG. 12 shows an elongation rate difference de distribution calculated from the deviation of the force of pressing down the ring 34 of the detection roll 33 by the steel strip having the in-ear extension (see FIG. 1) when (mm) is used. Although there is an area where de, which is impossible originally, is displayed as negative,
This is because of the following concept.

That is, as described in the preceding section (5), de is a value virtually distorted assuming that a flat plate having a length L is partially pulled, but the average length of the distorted result is Is set to L, tension is applied to the center and both ends, and negative tension (compression) is applied to the quarter, and the horizontal axis position (d
FIG. 12 is obtained by using the calculation logic for setting e = 0). Therefore, in this figure, the difference between the uppermost part and the lowermost part is important.

In this figure, one scale on the horizontal axis is de = 10 ^-4
That is, it corresponds to 0.001%, and when converted to steepness,

[0068]

Λ = (10 ⁻⁴ /0.247) ^1/2 = 0.002 That is, it corresponds to 0.2%.

Since this figure does not directly measure de as described in the previous section, unless the steel strip to be measured is actually calculated so as to have the shape as shown in this figure. No. An example of the confirmation is shown in FIG. The steepness calculated from the shape detector output de and the measured steepness ○
Are in good agreement with each other, and thus the vertical scale interval in FIG. 12 is appropriate, that is, it can be said that the index having the shape of de is detected well.

(12) Other Shape Detecting Method During Rolling Such a shape detecting device is a relatively new technology, and another method for knowing the shape of a steel strip used when it was absent is as follows.
The rolling mill was stopped and the tension was loosened to check visually, or both ends of the steel strip being rolled were hit with a rod to estimate the level of the generated sound. Although the former is reliable, there is a problem that a roll indentation called a touch mark remains at a stop portion of the rolled work roll. The latter has the advantage of not having such a problem and of being capable of continuous detection, but requires a skill in the operation and involves a risk.

(13) Apparatus for Adjusting Steel Strip Shape Provided in Rolling Mill As described in the previous section (6), in rolling, the shape changes due to slight deviation in elongation strain of rolling. Conversely, the rolling distortion is finely changed in the width direction to adjust the shape. For example, in the rolling mill shown in FIG. 1, the uppermost backup roll 23a has a split ring structure, and when one of these rings is moved up and down, the shape of the steel strip immediately below it changes. The adjusting device built in such a rolling mill has a history that is older than that of the shape detector, and detects the shape by the method described in the above (12), and operates the shape adjusting device to obtain the target shape. You may make it.

As other shape adjustment methods, a method of forcibly bending a work roll or an intermediate roll, a method of
A so-called gradient reduction method for adjusting the reduction force balance of the reduction device on the other side may be used.

(14) Automatic Shape Control Referring to FIG. 1 again, the shape of the steel strip is grasped by a shape detector during rolling, a difference from a target shape is confirmed, and the difference is adjusted. The shape may be fed back to the device to automatically control the shape to the target. FIG. 1 shows an example of automatic control for obtaining a flat steel strip having a target shape by confirming the grasp of the shape as a widthwise elongation rate difference distribution de of the steel strip using a shape detection roll. This is an example in which an asymmetric middle ear extension shape occurs. However, as described above, the steel strip being rolled looks flat due to the tension of the tension reel, but in this figure, the shape is drawn as if it is visible. The de distribution is calculated by a computer using first-order, second-order,
It is confirmed as a sum of fourth-order functions and is decomposed into each. The primary component is fed back to the intermediate roll bender under the gradient pressure of the rolling mill, the secondary component is fed back to the position adjustment of the contact ring constituting the backup roll, and, for example, all functions converge to zero. Is controlled as follows.

(15) λ2 and λ4 The steepness λ and elongation difference de have been described as indices indicating the shape of the steel strip. However, these must be in the form of a graph or a numerical table corresponding to the width direction position. Cannot be represented.
For example, if the steepness λ is only 2%, any of ear growth, medium growth, quarter growth, and the like cannot be determined. However, it is convenient if the shape can be displayed as one point in the two-dimensional orthogonal coordinates of the shape plane. This and the next section will discuss this.

Now, suppose that the de distribution remains only in the quadratic function in the rolling of the above item (14). If it is convex downward, the steel strip is ear-elongated, and if it is convex upward, it is medium-elongated. .
In addition, if the component of the quartic function remains, and it is open upward, it indicates the middle ear extension, and if it is open downward, it indicates the quarter extension.

The inventors of the present invention determine whether the end is extended (de> 0 at the end, ear extension) or contracted (de <0 at the end, middle extension) as compared with the center. Index steepness index λ
2 has been introduced. The difference from the steepness is to take a negative value. If the end is more elongated, it is positive, and if it is shrunk, it is negative. 2 of λ2 is related to the quadratic function component. On the other hand, if λ4 related to the quartic function is
It is used as an indicator of ear growth. First, the calculation of λ2 will be described. As shown in FIG. 11, the steel strip width w is divided into 36 equal parts between ± w / 2, and the ends are regarded as 7 w / 18 to 9 w / 18.
An index # 2 for determining whether the de of that portion is higher or lower than the dec of the central portion is determined in this section as follows.

[0077]

(Equation 22)

The sign of Λ2 is positive or negative, and k is a proportional coefficient described later. And

[0079]

Λ2 = ± (| Λ2 | /2.47) ^1/2, and the sign of λ2 is set to Λ2. The steel strip having a positive λ2 has a so-called ear elongation at the end compared to the center, and the steel strip having a negative λ2 has a center elongated at the end compared to the end. Indicates that there is so-called medium elongation.

If, for example, λ2 = 1%, if the steepness at the center is λ, the end is λ + 1% and λ2 =
If it is -1%, it is convenient to determine the value of k such that if the steepness of the end is λ, the center is λ + 1%. Thus, the sign of λ2 indicates which of the center and the end is the reference for the steepness, that is, which part is less elongated. When λ2 = −1%, if the steepness at the center is λ, the steepness at the end does not necessarily become λ-1%. This is because λ-1% may be negative.

Next, the calculation of λ4 will be described, but is the same as λ2. The steel strip width w is divided into 36 equal parts between ± w / 2, and the quota part is regarded as 3 w / 18 to 5 w / 18, and it is determined whether the de of that part is higher or lower than the dec of the central part. Index # 4 for this section is determined as follows in this section.

[0082]

(Equation 24)

The sign of # 4 is positive or negative, and k is the aforementioned proportional coefficient. And

[0084]

Λ4 = ± (| Λ4 | /2.47) ^1/2, and the sign of λ4 is set to Λ4. The sign of λ4 is the same as λ2.

(16) Shape plane Considering the two-dimensional orthogonal coordinates of λ4 on the horizontal axis and λ2 on the vertical axis, the shape of the steel strip in FIG. 1 can be displayed as one point within it, and one point on the so-called shape plane , That is, as a point having coordinates (λ4, λ2). An example is shown in FIG.

For example, a shape in which λ4 is 0 means that the shape is on the vertical axis on this plane. Further, if λ2 is positive, simple ear extension is obtained, and if λ2 is negative, simple middle extension is obtained. Show.

If λ4 is positive, it indicates that the shape of the quarter is mixed, and if λ4 is negative, it indicates that the shape of the ear is mixed. Eventually (λ
If the position of (4, λ2) is the first quadrant on the upper right, quarter extension is mixed with ear extension, if it is in the second quadrant on the upper left, it is in the middle of the ear with strong ear extension, and if it is in the third quadrant on the lower left, the middle of the ear is strong. In the fourth quadrant in the lower right, it indicates that the shape is a mixture of medium elongation and quarter elongation. In the example on the display means 38 of FIG. 1, it is displayed as a cross at the lower left of FIG.

(17) Shape Control During Rolling Since it is desired that the steel strip when shipped as a product is close to a flat shape, one goal of the conventional rolling operation is to make the shape of the steel strip close to flat. there were. However,
If there is no elongation during the rolling operation, there is a danger of tearing if small cracks or the like are present at the ends of the steel strip. That is, the shape of the fourth quadrant is not desirable when represented by a shape plane. Therefore, the shape of the rolled steel strip is the first,
The flat shape was strictly the origin of this plane, but the actual target shape was a slight extension of the ear.

(18) Summary In the present invention, in the production of a so-called ultra-thin steel strip having a sheet thickness of 0.3 mm or less, the shape of the steel strip is set to a moderate elongation of 0.5 to 4% or a difference in elongation percentage of 6%. By controlling the medium elongation from × 10 ⁻⁵ to 4 × 10 ⁻³ , it has been found that wrinkles in the furnace can be prevented even if the subsequent heat treatment is performed in a furnace having a long free span such as a vertical furnace. On the point.

However, of course, the present invention is not only applicable to a modern rolling mill in which a shape detector is provided and fed back to the shape adjusting device. For example, a conventional rolling mill can be used in the following manner. That is, in the final pass of rolling, after rolling under certain rolling conditions, the rolling mill is stopped, the steel strip is sagged and visually inspected to see if its shape is middle elongation, if not. If so, correct the rolling conditions and repeat the rolling and inspection again. For measuring the shape, there is also a method of measuring the steepness by inserting a flat plate under the steel strip. The steepness is in the range of 0.5% to 4% if it is apparently medium elongation, both visually and when the steepness is actually measured. If it is medium elongation, the conditions are followed and rolling is completed. According to this method, indentations (touch marks) of the roll due to some stoppages of rolling are inevitable in the initial portion of rolling, and a shape unstable portion of several hundred meters is created until the conditions are set. However, since the steel strip is extremely thin, the weight of the scrap portion is smaller than the whole.

In the heat treatment line, which is a post-rolling process, the steel strip is finally wound in a coil shape. When a wrinkled steel strip is wound on a wrinkled part in a furnace, the steel strip is internally wound there. Since the problem that wrinkles are transferred to the outer winding appears, it is necessary to avoid generating wrinkles at the beginning of heat treatment as much as possible, but since the part of the rolling adjustment part is not middle elongation, Fortunately, the initial part of the rolling is fortunately the final part of the heat treatment which is the next step, and becomes the outer winding of the wound coil, so that the wrinkle transfer problem does not occur. Outer winding wrinkles may be cut off in a further next step. The same is true for modern rolling mills that have a shape detector and perform automatic shape control. Even so, the damage is smaller than in the past, when the entire steel strip was wrinkled.

FIG. 14 shows a comparison between the shape before the heat treatment, ie, the rolled shape, and the shape after the heat treatment when the steel strips of various shapes are heat-treated in the bright annealing furnace shown in FIG. As described in the prior art, wrinkles are likely to occur in the austenitic system. Therefore, in this experiment, SUS304, which is a typical steel type, was used.
mm, and the maximum steel strip temperature in the furnace was about 1050 ° C. as a general heat treatment temperature of SUS304. The wrinkles in this figure show a typical form, which is linear in the longitudinal direction of the steel strip, which is considered to be the result of the steel strip buckling in the width direction in the furnace. As can be seen, wrinkles occurred in the parts of the shape that had not stretched before the heat treatment, which was reproducible.

That is, in the conventional rolling, a flat shape with a slight edge elongation has been often aimed at. However, when such a steel strip is continuously annealed, significant wrinkles are generated in a flat central portion although not shown in the figure. Was. However, by rolling the central portion as shown in the present invention with a target of non-flat, so-called medium elongation and realizing the shape, wrinkling in the furnace, which is the next step, can be avoided.

By utilizing the above facts, ultra-thin steel strips of many austenitic steel grades were further passed. FIG. 13 described above.
Shows the relationship between the resulting rolling shape and the presence or absence of wrinkles in the furnace.
Obviously, the shape of the second and third quadrants is desirable. In some cases, wrinkles were observed near the vertical axis of the second quadrant, but a stable manufacturing condition region was confirmed.

[0095]

According to the present invention, by controlling the rolling mill so as to have a middle elongation during rolling, it is possible to reliably prevent wrinkles from occurring in the steel strip after annealing, and to make the ultra-thin stainless steel strip after annealing. And a high-quality stainless steel strip can be manufactured.

In recent years, the demand for ultra-thin stainless steel has increased, and it is indispensable for stainless steel strip manufacturers to have a stable production technique. Prevention of wrinkles generated in the process is particularly important among them. Yes, especially in the heat treatment furnace, but it was difficult to take countermeasures.

As described above, when wrinkles occur in the annealing furnace, the commercial value of the stainless steel strip is completely lost, and
The production cost of each process required to roll to ultra-thin is wasted despite being more expensive than products of general thickness,
Further, if the time required for each step required for rolling to an extremely thin thickness is obtained, each step can produce a steel strip having a general thickness as a larger weight. In other words, instead of producing a large amount of general thickness steel strip, a small amount of ultra-thin material is produced, so scraping ultra-thin material is equivalent to scraping a comparable amount of general thickness steel strip. In order to re-produce that amount of ultra-thin material, we have to give up producing a comparable amount of general thickness steel strip,
The present invention can solve this problem, which has also reduced the production capacity of the factory.

Conventionally, wrinkle prevention depends only on the adjustment of cooling conditions. However, since such conditions have not been established, technical staff must attend the cooling adjustment work when heat treating ultra-thin steel strip. In addition, since the ultra-thin product inevitably has a long steel strip length, it requires a long time to pass through the steel strip here, and therefore, the time required for attending is also long. The industrial significance of the present invention that solves these problems is extremely large.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an overall configuration for explaining an embodiment of the present invention.

FIG. 2 is a perspective view showing a shape detection roll 33.

FIG. 3 is a sectional view perpendicular to the axis of the shape detection roll 33.

FIG. 4 is a diagram for explaining distortion caused by rolling.

FIG. 5 is a diagram showing the relationship between the shape of a steel strip and steepness.

FIG. 6 is a diagram for explaining steepness.

FIG. 7 is a diagram for explaining an elongation difference.

FIG. 8 is a diagram for explaining the occurrence of medium elongation by rolling.

FIG. 9 is a diagram for explaining a method of measuring an elongation difference.

FIG. 10 is a view schematically showing a schematic configuration of a rolling mill 20.

11 is a graph showing an elongation difference detected by a shape detection roll 33. FIG.

FIG. 12 is a graph showing steepness detected by a shape detection roll 33.

FIG. 13 shows steepness λ2, λ4 displayed on display means 38.
It is a figure showing an example of.

FIG. 14 is a view showing a state of occurrence of wrinkles before and after annealing of a stainless steel strip.

FIG. 15 is a simplified sectional view showing a conventional horizontal annealing furnace.

FIG. 16 is a simplified sectional view showing a conventional vertical bright annealing furnace.

FIG. 17 is a simplified cross-sectional view showing another conventional vertical bright annealing furnace.

FIG. 18 is a simplified sectional view showing a conventional vertical annealing furnace.

[Explanation of symbols]

 Reference Signs List 20 cold rolling mill 21 annealing furnace 22a, 22b work roll 23a, 23b intermediate roll 24a, 24b backup roll 25a, 25b pressing down means 26 stainless steel strip 33 shape detection roll 34 contact ring 35 strain gauge 37 calculating means 38 display means 39 control means

Claims (4)

(57) [Claims] An ultra-thin stainless steel strip which is annealed in a continuous annealing furnace having a non-contact or unconstrained free span of at least 15 m or more, wherein the stainless steel strip is cold-rolled to a thickness of 0.3 mm or less by a rolling mill. In the manufacturing method, based on the shape of the stainless steel strip immediately after the cold rolling,
A method for producing an ultra-thin stainless steel strip, characterized in that a rolling mill is feedback-controlled to adjust the rolling tension of the stainless steel strip so that the stainless steel strip has a middle elongation. 2. The method for manufacturing an ultra-thin stainless steel strip according to claim 1, wherein the steepness of the middle elongation is set to 0.2 to 2%. 3. The elongation difference of the middle elongation is 1 × 10 ⁻⁵ or more.
2. The method for producing an ultra-thin stainless steel strip according to claim 1, wherein the thickness is 1 × 10 ⁻³ . 4. A rolling mill for cold rolling a stainless steel strip to a thickness of 0.3 mm or less, and a free span in which the passed stainless steel strip is not contacted or unconstrained for at least 15 m or more, A continuous annealing furnace for annealing the stainless steel strip cold-rolled to a sheet thickness of 0.3 mm or less, a production apparatus for an ultra-thin stainless steel strip, comprising: Means for detecting a distribution of elongation difference in the width direction of the rolled stainless steel strip; calculating means for calculating a steepness based on an output from the elongation difference distribution detecting means; and the calculating means Display means for displaying an image of the determined steepness as a distribution on the surface of the stainless steel strip; and in response to an output from the arithmetic means, the rolling force of the rolling mill so that the stainless steel strip has a middle elongation. To Apparatus for producing ultra-thin stainless steel strip which comprises a Gosuru control means.