JPH0745047B2 - Multi-stage rolling mill - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multi-high rolling mill equivalent to 20 stages having an excellent flatness control function.

(Prior Art) Cold rolling of hard-to-work materials such as stainless steel and silicon steel is often carried out by a multi-high rolling mill having 12 or 20 steps. In such a multi-stage rolling mill, the diameter of the work rolls can be reduced, so that there is an advantage that the rolling load can be reduced under a high pressure as compared with the conventional rolling mill having a vertical arrangement. On the other hand, however, when the work roll has a small diameter, the roll is largely bent, which causes a defect that the rolled material is apt to have a defective shape.

Therefore, various solutions have heretofore been proposed in order to prevent the occurrence of such shape defects.

As one of them, there is a method of controlling the shape of the rolled material by dividing the outermost backup roll into a plurality of parts in the axial direction and adjusting the displacement amount of each divided roll. However, in this method, the more intermediate rolls there are between the backup rolls and the work rolls, the less the effectiveness thereof. Therefore, a multi-stage rolling mill having many intermediate rolls such as 12 or 20 rolls. Then, I was not able to fully demonstrate that ability.

In order to improve this point, a method of using a work roll bender or an intermediate roll bender together with the above-mentioned backup roll displacement amount adjusting method has been proposed in Japanese Patent Publication No. 58-50108. However, this method has the drawback that the equipment becomes complicated, and the thinner the roll, the more
Further, as the roll barrel becomes longer, the bending force does not act on the central portion, so that there is a problem that the control force remains only at the rolled material end portion.

Also, Japanese Patent Publication No. 63-207405 proposes a method in which one end of the intermediate roll has a tapered shape and is independently shifted in the axial direction. However, even in this method, the control force and the range are only around the taper portion, and the taper shape needs to be changed one by one according to the steel type and the plate width.

Further, Japanese Patent Publication No. 63-30104 and the like propose a rolling machine of a vertical type in which an S-crown that can be approximated by a cubic formula is given to a roll and the roll can be shifted in the axial direction. However, even with this method, it is possible to control only the end portion and the central portion of the rolled material, and it is helpless to control the quarter elongation, and further the composite elongation in which belly elongation, ear elongation and the like are mixed.

(Problems to be Solved by the Invention) The present invention advantageously solves the above-mentioned problems, not to mention simple stretch and ear extension, as well as complex shape defects such as quarter stretch and ear-belly composite extension. It is an object of the present invention to propose a 20-high multi-stage rolling mill that can be modified and has excellent shape control capability.

(Means for Solving the Problems) That is, the present invention provides a multi-stage rolling mill in which a plurality of first intermediate rolls, second intermediate rolls, and backup rolls are sequentially arranged behind a pair of work rolls. , At least two rolls selected from a roll group consisting of a first intermediate roll and a second intermediate roll are provided with roll crowns of at least one wavelength having the same waveform curve, while the same roll group At least two other rolls selected from the above are given roll crowns over at least two wavelengths of the same wavy curve, and for each of the above crown-providing roll pairs,
It is a multi-stage rolling mill because it is arranged such that the roll axis directions are opposite to each other and is incorporated in the mill housing so as to be movable in the roll axis direction.

Further, the present invention is a multi-stage rolling mill in which a roll bending device is incorporated in the above rolling mill.

In the present invention, as the waveform curve for one wavelength or two wavelengths to be given to the roll, one pitch or two pitches are extracted from the sine curve, and one pitch is also obtained from a higher-order function of third or higher order. Alternatively, those obtained by taking out two pitches, and further, their approximate curves are advantageously matched, but among them, one taking out one pitch or two pitches from the sine curve and its approximate curve are particularly preferable.

Hereinafter, the present invention will be specifically described with reference to the drawings.

1 a and b show the roll arrangement of a multi-high rolling mill according to the invention in side and in front.

In the figure, 1 is a rolled material, 2 is a work roll, 3 is a first intermediate roll, 4 is a second intermediate roll, and 5 is a split-type backup roll. Rolls 2 are arranged and these work rolls 2
4 first intermediate rolls, 2 behind each
However, behind the first intermediate roll 3, there are a total of six second intermediate rolls 4 each in the upper and lower three, and the second intermediate roll 4 further.
A total of 8 split back-up rolls 5 are installed behind each of the above and below, forming a 20-high rolling mill.

In addition, 6 is a roll bending apparatus.

Of these, the first intermediate roll 3 is provided with a roll crown having a waveform curve that can be approximated by one pitch of a sine curve, and has a structure capable of shifting in the roll axial direction.

On the other hand, the second intermediate roll 4 shown by hatching in FIG. 1 is provided with a roll crown formed of a waveform curve that can be approximated by two pitches of a sine curve, and like the first intermediate roll, a structure capable of shifting in the axial direction. It has become.

The roll to which the waveform curve that can be approximated by one pitch or two pitches of the sine curve is to be added is not limited to the above case, and all of the work roll 2, the first intermediate roll 3, and the second intermediate roll 4 are added. It is possible to freely select and combine from the inside.

In addition to the above-mentioned sine curve and its approximate curve, the waveform curve to be given is a waveform curve obtained by extracting one pitch or two pitches with a coordinate origin interposed from a higher-order equation of a third order or higher, and further It may be an approximate curve.

Further, the roll shift device may be either a hydraulic type or an electric type.

(Operation) In FIGS. 2A to 2C, a roll pair provided with a corrugated roll crown that can be approximated by one pitch of a sine curve is installed in the roll axial direction in the opposite direction, and the roll gap change in the case of axial shifting is shown. Show.

FIG. 11A shows a case where the roll pairs are arranged to face each other and the roll gap is constant in the axial direction. FIG. B shows the case where each roll is moved in the direction of the arrow from the state of a,
The roll gap is wide at the center and narrow at the ends. Further, FIG. 6C shows a case where each roll is moved in the opposite manner to that of FIG. B, but the roll gap is narrow at the center and wide at the ends.

Therefore, by appropriately shifting the roll pair provided with the corrugated roll crown that can be approximated by one pitch of the sine curve in the roll axial direction, it is possible to effectively correct the ear stretch and the belly stretch.

Next, FIGS. 3A to 3C show changes in the roll gap when a roll pair provided with a corrugated roll crown that can be approximated by two pitches of a sine curve is installed in the roll axial direction in the opposite direction and is shifted in the axial direction. .

FIG. 11A shows a case where the roll pairs are arranged to face each other and the roll gap is constant in the axial direction. FIG. B shows the case where each roll is moved in the direction of the arrow from the state of a,
The quarter has a narrow roll gap, while the center and both ends have wide roll gaps. Further, FIG. 6C shows the case where each roll is moved in the direction opposite to that in FIG. B, but the quarter portion has a wide roll gap.

Therefore, by appropriately shifting the roll pair provided with the corrugated roll crown that can be approximated by two pitches of such a sine curve in the roll axis direction, it becomes possible to effectively correct the ear-abdominal compound stretch and the quarter stretch. .

Now, referring to FIG. 4, as the first intermediate roll (1IMR) or the second intermediate roll (2IMR) of the 20-high rolling mill shown in FIG. A roll pair provided with (hereinafter simply referred to as S crown) or a roll pair provided with a corrugated roll crown (hereinafter simply referred to as W crown) that can be approximated by two pitches of a sine curve is used, and each is independently alone in the roll axial direction. The results of examination of the shape control ability when shifted are shown in comparison with the case where a so-called one-taper roll having tapered grinding on one side is shifted and the case where a divided backup roll is extruded.

The shape control ability was evaluated by the elongation difference ratio Λ2 between the central portion and the end portion and the elongation difference ratio Λ4 between the central portion and the quarter portion of the rolled material.

As is clear from the figure, in the case of the single taper roll shift alone and the S crown shift alone, the ear extension and the belly extension can be controlled to some extent, but the quarter extension and the ear-belly composite extension control can hardly be expected.

It should be noted that the split backup roll extrusion can be expected to slightly control the quarter elongation and the ear-abdominal compound elongation.

On the other hand, in the case of W crown shift alone, a remarkable effect can be expected in controlling the quarter elongation and the ear-abdominal compound elongation control. However, it is hard to say that it is enough to control ear and belly stretch.

Next, FIG. 5 shows the results obtained by investigating the shape correction ability when using the W crown roll as the first intermediate roll and the S crown roll as the second intermediate roll at the same time in the 20-high rolling mill described above. The results are shown in comparison with the investigation results when a single taper roll is used as an intermediate roll and a roll bender and a split backup roll extrusion are used together.

As is clear from the figure, by combining the S crown roll and the W crown roll and appropriately shifting in the roll axial direction, not only ear elongation and belly elongation but also quarter elongation and composite elongation An excellent correction capability is obtained, and thus a wide range of flatness control can be realized.

In the present invention, the roll pair to which the S crown or W crown is to be applied is at least two roll pairs selected from a roll group consisting of a work roll, a first intermediate roll and a second intermediate roll, Although any roll may be used, it is more preferable that each roll pair is selected from the same type of roll group, that is, a work roll pair, a first intermediate roll group, and a second intermediate roll group. Further, the control effect is larger as the S-crown and W-crown-applied rolls are closer to the material to be rolled, and the arrangement of each roll pair is larger in the order of point symmetry, vertical symmetry, and left-right symmetry with the material to be rolled as the center.

When comparing a sine curve as a reference line of a waveform curve to be given to a roll and a higher-order function curve, if the sine curve is followed, the roll crown amount and the waveform pitch can be easily adjusted simply by giving the amplitude and period. It is extremely advantageous in that it can be set, and also has the advantage of good symmetry in the width direction.

On the other hand, in the case of a higher-order function curve, as described below, it may not be possible to arbitrarily set the roll crown amount and the waveform pitch. It has some disadvantages in that it becomes complicated, and that the symmetry across the width is not very good.

That is, for example, considering the case where a waveform curve for two pitches as shown in FIG. 6 is given here, in order to perform shape control at this time, the center of the roll barrel is set as the origin and the waveform curve is set with respect to the origin. Since it is necessary to make point symmetry, the higher-order function is expressed by the following equation (1).

f (x) = a ₁ x + a ₃ x ³ + a ₅ x ⁵ + ... + a _n x ⁿ (1) In order to arbitrarily set the roll crown amount and the pitch by using the formula (1), shown in Table 1. It is necessary to determine the coefficients a _{1 to} a _n so as to satisfy the six equations.

That is, equation (1) has six unknowns a ₁ , a ₃ , a ₅ , a ₇ , a ₉ ,
It is an 11th-order odd function as in the following equation (1) ′ having a ₁₁ , which is extremely complicated.

_{f (x) = a 1 x} + a 3 x 3 + a 5 x 5 + a 7 x 7 + a 9 x 9 + a 11 x 11 ...
(1) 'Also, if n <11, the roll crown cannot be set arbitrarily. This is because when we try to express it by a fifth-order odd function like the equation (1), there are _three unknowns, a ₁ , a ₃ , and a ₅ ,
This is because only three conditional expressions of the expression (2) shown in Table 1 can be taken into consideration.

f (x) = a ₁ x + a ₃ x ³ + a ₅ x ⁵ (1) ″ For example, in order to define the crown amount, when the formulas (2) -1, (2) -2 shown in the first case are selected, To specify the pitch, the remaining four conditional expressions (2) -3, (2) -4,
Only one conditional expression can be selected from among (2) -5 and (2) -6, and the pitch of the crown is uniquely determined by this, so the crown pitch cannot be changed arbitrarily. .

In this way, when a particular roll crown is represented by a higher-order function curve, the crown cannot be arbitrarily selected when the order is low, whereas when it is represented by a sine curve, on the other hand, when the order is high, it becomes extremely complicated. The disadvantage remains.

(Example) Example 1 In the 20-high rolling mill shown in FIG. 1 above, a roll having a crown (S1 crown) that can be approximated by a cubic formula as shown in FIG. 7 is used as the first intermediate roll 3. , While the first
A roll having a crown (W1 crown) that can be approximated by a quintic equation as shown in FIG. 8 was used as the second intermediate roll 4 shown by hatching in the figure.

Then, the first intermediate roll and the second intermediate roll were axially shifted to roll a stainless steel plate having a plate width of 1000 mm from a plate thickness of 1.2 mm to 1.0 mm.

Shape plan views showing the roll arrangement and the shape correction ability at this time are shown in FIGS. 9A and 9B, respectively.

Further, FIG. 9 shows the case where the conventional device is used.
A roll having a single taper shape as shown in a and b is used as the first intermediate roll and the second intermediate roll, these rolls are axially shifted, and the split backup roll extrusion is also used, The results of an investigation of the shape control ability when rolling is also shown.

As is apparent from FIG. 9, the conventional apparatus can obtain the shape control ability only in a narrow range, and the shape ability to follow the composite elongation and the quarter elongation is remarkably small. Moreover, because of the narrow control range, it is necessary to change the taper shape of the first intermediate roll or the second intermediate roll depending on the case depending on the steel seed plate width of the rolled material.

On the other hand, when the device of the present invention is used, it is possible to obtain a wide control range that can sufficiently cope with the composite elongation and the quarter elongation, and to change the shape of the intermediate roll for various kinds of rolled materials. It is possible to obtain a plate having a good shape without any problem.

Example 2 Similarly, in the 20-high rolling mill, the eighth intermediate roller was used as the first intermediate roll.
A roll having a crown (W1 crown) that can be approximated by a quintic equation as shown in the figure is used as the second intermediate roll
Rolls having a crown (S1 crown) that can be approximated by a cubic equation as shown in the figure are arranged as shown in FIG. 11a, and the result of investigation on the shape control ability when the same rolling as in Example 1 is performed is shown. It is shown in FIG.

As is clear from Fig. 11b, the first
When W crown roll is used for the intermediate roll,
Compared to the case where S crown roll is used as the intermediate roll, the ability to control the quarter elongation and the composite elongation is further excellent.

Example 3 Similarly, in the 20-high rolling mill, the first intermediate roll 12th
A roll having a crown (W2 crown) that can be approximated by two sine curve pitches as shown in the figure, on the other hand, a crown (S2 crown) that can be approximated by one sine curve pitch as shown in FIG. 13 as the second intermediate roll. Roll with 14th
The result of having investigated about shape control ability when arrange | positioning like FIG. A and performing the rolling similar to Example 1 is shown in this figure b.

As is clear from Fig. 14b, even when the roll is provided with a crown approximated to a sine curve, excellent quarter elongation and composite elongation control ability are obtained as in the second embodiment.

Example 4 Similarly, in a 20-high rolling mill, the eighth intermediate roll was used as the first intermediate roll.
A roll having a crown (W1 crown) that can be approximated by a quintic equation as shown in the figure is used as the second intermediate roll
A roll having a crown (S1 crown) that can be approximated by a cubic formula as shown in the figure is arranged as shown in FIG. 15a, and a bending force is applied to the first intermediate roll to obtain the first embodiment.
The result of investigating the shape control ability when performing the rolling similar to the above is shown in FIG.

As is clear from FIG. 15b, in this example as well as in Examples 2 and 3, since the W intermediate roll is used as the first intermediate roll, which is closer to the material to be rolled, the ability to control the quarter elongation and the composite elongation is particularly excellent. ing.

Example 5 Similarly, in the 20-high rolling mill, the first intermediate roll is the 12th roll.
A roll having a crown (W2 crown) which can be approximated by two pitches of a sine curve as shown in the figure, while a crown (S2 crown) which can be approximated by one pitch of a sine curve as shown in FIG. 13 is used as a second intermediate roll. Fig. 16b shows the results of an examination of the shape control capability when the rolls having the same were arranged as shown in Fig. 16a and the bending force was applied to the first intermediate roll to carry out the same rolling as in Example 1. Show.

Example 6 In the same 20-high rolling mill, as shown in FIG. 17a, of two sets of four rolls located outside the second intermediate roll,
A crown (W1 crown) that can be approximated by a quintic equation as shown in FIG. 8 is provided to one set at point symmetry positions, while a crown (S1 crown that can be approximated by a cubic equation as shown in FIG. The result of the investigation of the shape control ability when the same rolling as in Example 1 was performed by applying a bending force to the first intermediate roll by applying each of the crowns) is shown in FIG.

Example 7 Similarly, in a 20-high rolling mill, as shown in FIG. 18a, two upper and lower two sets of rolls located outside the second intermediate roll can be approximated by a quintic equation as shown in FIG. Crown (W1
Crown) can be approximated by a cubic equation as shown in Fig. 7 to a pair of upper and lower parts located in the center (S1 crown)
FIG. 11B shows the results of an examination of the shape control ability when the same rolling as in Example 1 was performed by applying the bending force to the first intermediate roll and applying the bending force.

Example 8 Also in a 20-high rolling mill, as shown in FIG. 19A, a crown which can be approximated to a pair of rolls located in a point symmetrical position of the first intermediate roll by two pitches of a sine curve as shown in FIG. (W2 crown), on the other hand, a shape obtained by applying a crown (S2 crown) that can be approximated by one pitch of a sinusoidal curve as shown in FIG. The result of investigation on the control ability is shown in FIG.

Example 9 In the same 20-high rolling mill, as shown in FIG. 20a, of the two upper and lower rolls located outside the second intermediate roll,
One set is a crown (W2 crown) that can be approximated by two pitches of a sine curve as shown in Fig. 12, while the other set is a crown (S2 crown) that can be approximated by one pitch of a sine curve as shown in Fig. 13. ) Is applied and the bending force is applied to the first intermediate roll, and the shape control capability when the same rolling as in Example 1 is performed is investigated, and the result is shown in FIG.

Example 10 Similarly, in a 20-high rolling mill, as shown in FIG. 21a, two sets of upper and lower two rolls located outside the second intermediate roll were used with two sine curve pitches as shown in FIG. Approximate crowns (W2 crowns) are added to the upper and lower sets located in the center on the other hand, and crowns (S2 crowns) that can be approximated by one pitch of a sine curve as shown in FIG.
The result of investigating the shape control ability when the bending force is applied to the intermediate roll and the same rolling as in Example 1 is performed is shown in FIG.

Example 11 Similarly, in a 20-high rolling mill, as shown in FIG. 22a, a pair of rolls located at the point symmetry position of the first intermediate roll can be approximated by a quintic equation as shown in FIG. Crown) and, on the other hand, another set of crowns (S1 crowns) that can be approximated by a cubic formula as shown in FIG. 7 are provided, respectively, and the shape control ability when the same rolling as in Example 1 is performed is investigated. The result is shown in FIG.

Example 12 Similarly, in a 20-high rolling mill, as shown in FIG. 23a, a work roll pair is provided with a crown (W1 crown) that can be approximated by a quintic equation as shown in FIG. A crown (S1 crown) that can be approximated by a cubic equation as shown in FIG. 7 is provided to each pair of rolls at symmetrical positions, and the shape control ability when the same rolling as in Example 1 is performed is investigated. The result is shown in FIG.

Example 13 A stainless steel plate having a plate width of 1000 mm was rolled from a plate thickness of 1.2 mm to 1.0 mm in the 20-high rolling mill shown in FIG. 1 above. At that time, the taper roll shown in FIG. 10, the S crown roll shown in FIG. 13, and the W crown roll shown in FIG. 12 were used individually for the first intermediate roll, respectively, and were moved to the position shown in FIG. After the first intermediate roll is installed and rolled, and the first intermediate roll is shifted by 50 mm to the position shown in Fig. 24b, the elongation difference distribution in the width direction of the rolled material is shown in Fig. 25.
Shown at a, b and c in Figures, 26 and 27. In each figure, “a” indicates the distribution of elongation difference ratio before the shift, and “b” indicates the distribution of the elongation difference ratio after the shift of 50 mm. Further, c indicates a distribution of variation in the elongation difference ratio in the width direction of the rolled material due to the shift of 50 mm (an elongation difference ratio distribution a before the shift minus an elongation difference ratio distribution b after the shift is subtracted).

The elongation difference ratio Λ is defined by the following formula (for example, see "Theory and practice of sheet rolling" edited by The Iron and Steel Institute of Japan, p. 96).

Λ = (1 _i −1 _o ) / 1 _o where 1 _i is the elongation (mm) of the rolled material at each position in the strip width direction, and 1 _o is the elongation (mm) of the center of the rolled material. . When the difference in elongation is positive, that part of the rolled material extends from the center of the rolled material, and when it is negative, it does not extend. That is, if the difference in elongation difference in the width direction is equal, it means that the shape of the rolled material is flat.

The 20th which used the taper roll alone for the 1st intermediate roll
In the case of the figure, the quarter elongation is generated, and even if the first intermediate roll is shifted by 50 mm, only the shape of the end of the rolled material can be changed. Further, in the case of FIG. 26 in which the S crown roll is used alone as the first intermediate roll, only the shapes of the end portion and the central portion of the rolled material can be changed. On the other hand, the 27th, in which the W crown roll was used alone as the first intermediate roll,
In the case of the figure, it is possible to mainly change the shape of the quarter portion. Therefore, if the W crown roll is used, the quarter elongation control can be sufficiently performed.

Example 14 Similarly, in a 20-high rolling mill, in addition to the conventional shape control function, a W crown roll as shown in FIG. 12 was used, and each roll was shifted to an appropriate position to obtain the best shape. The same rolling as in Example 13 was performed. In addition, a good shape means that the variation of the elongation difference ratio distribution in the width direction is small.

If the W crown roll is not used as the conventional device,
Fig. 28 shows the case where the W crown roll is used for the central second intermediate roll, Fig. 29 shows the case where it is used for the outer second intermediate roll, and Fig. 30 shows the case where it is used for the first intermediate roll.
Figure 31 shows each.

As is clear from these figures, in the conventional device, the quarter elongation occurs, and this cannot be suppressed. On the other hand, when the apparatus of the present invention is used, it is possible to control the elongation of the quarter portion and flatten the shape of the rolled material. In this case, the controlled variables are the central second intermediate roll (Fig. 29), the outer second intermediate roll (Fig. 30), the first
It becomes larger in the order of the intermediate roll (Fig. 31). Therefore,
For example, the elongation of the quarter part of the rolled material on the entry side is large,
If a large amount of control is required in the quarter section, the W crown roll may be applied to a roll located near the rolled material, and conversely, even if there is a quarter elongation of the incoming rolled material, the elongation is small and When the control becomes too sensitive, it is desirable to use it at a position away from the rolled material. As described above, the present invention enables optimum control for various quarter elongations.

Example 15 Similarly, in a 20-high rolling mill, as shown in FIG.
Using the S-crown roll shown in FIG. 7 as the intermediate roll and the W-crown roll shown in FIG. 8 as the second intermediate roll on the outer side, these rolls are appropriately positioned so as to obtain the best shape. And rolled in the same manner as in Example 13. Fig. 32 shows the distribution of the elongation difference ratio of the rolled material at that time.

By combining the W crown roll and the S crown roll, the quarter portion is controlled by the W crown roll and the end portion and the central portion are controlled by the S crown roll to obtain a completely flat rolled material having a uniform elongation difference in the width direction. I was able to.

It is obvious that the W crown roll is essential in addition to the conventional S crown roll in order to obtain this completely flat rolled material.

(Effects of the Invention) Thus, according to the multi-high rolling mill according to the present invention, excellent correction ability can be obtained not only for the ear elongation and the belly elongation but also for the quarter elongation and the composite elongation, and therefore the flatness control over a wide range can be achieved. Can be realized.

[Brief description of drawings]

1 a and b are a side view and a front view showing a roll arrangement of a 20-high rolling mill to which the present invention is applied, and FIGS. 2 a to 2 c are S crown rolls installed in parallel in opposite directions, respectively. FIG. 3A to FIG. 3C show roll gap changes when the roll gap is shifted in the roll axis direction, and FIGS. 3A to 3C show roll gap changes when the W crown rolls are installed in parallel in opposite directions and are shifted in the roll axis direction. FIG. 4 and FIG. 4 are diagrams showing the shape control ability when the S crown roll pair or the W crown roll pair is independently applied to the first intermediate roll or the second intermediate roll of the 20-high rolling mill, respectively. FIG. 5 is a shape control range diagram showing the shape correction ability when the W crown roll and the S crown roll are simultaneously used as the first intermediate roll and the second intermediate roll of the 20-high rolling mill, and FIG. 6 is a high-order formula. W that can be approximated FIG. 7 is a diagram showing a suitable S-crown that can be approximated by a cubic formula, FIG. 8 is a diagram showing a suitable W-crown that can be approximated by a quintic formula, and FIGS. Roll arrangement diagram and shape control range diagram showing the arrangement of W crown roll and S crown roll in a 20-high rolling mill, respectively. Fig. 10 a and b are diagrams showing the taper shape of a single taper roll, Fig. 11 respectively. a and b are roll arrangement diagrams and shape control range diagrams showing the arrangement of W crown rolls and S crown rolls in a 20-high rolling mill, respectively, and FIG. 12 shows a suitable W crown that can be approximated by two pitches of a sine curve. Fig. 13 is a diagram showing a suitable S-crown that can be approximated by one pitch of a sine curve, and a in Figs. 14 to 23 is W in a 20-high rolling mill.
Roll arrangement diagrams showing the arrangement of the crown rolls and the S-crown rolls, b in the same figure are shape control range diagrams for each roll arrangement in the same figure a, and FIGS. 24a and 24b are respectively for a 20-high rolling mill. FIGS. 25A, 25B, and 25C are views showing roll positions of the first intermediate roll before and after the shift, respectively, and FIGS. 25A, 25B, 25C, and 25C show the before and after shifts when the taper roll is used alone as the first intermediate roll. 26A, 26B, 26C, 26C, 26C, 26D, 26E, 26C, 26C, 26C, 26C, 26C, 26C, 26C, 26C, 26C, and 26C show the distribution of the difference in elongation percentage and the distribution of the amount of change in the difference in elongation, respectively, before the shift in the case where the S crown roll is used alone for the first intermediate roll, The figure showing the distribution of the difference in elongation after the shift and the distribution of the amount of change in the difference in the elongation, Figures 27a, 27b, 27c, and 27c are the shifts when the W crown roll is used alone as the first intermediate roll. Distribution of elongation difference before and after shift and Fig. 28 is a diagram showing the distribution of the change rate of the difference ratio, Fig. 28 is a diagram showing the distribution of the elongation difference ratio when a conventional 20-high rolling mill is used, and Fig. 29 is a W crown roll with 20-high rolling. Fig. 30 is a diagram showing an elongation difference distribution when used for the second intermediate roll in the center of the rolling mill. Fig. 30 shows the elongation when the W crown roll is used for the second intermediate roll outside the 20-high rolling mill. Fig. 31 is a diagram showing a difference distribution, Fig. 31 is a diagram showing an elongation difference distribution when the W crown roll is used as the first intermediate roll of the 20-high rolling mill, and Fig. 32 is a 20-high rolling mill. FIG. 3 is a diagram showing an elongation difference rate distribution when an S crown roll is used as the first intermediate roll and a W crown roll is used as the outer second intermediate roll. DESCRIPTION OF SYMBOLS 1 ... Rolled material, 2 ... Work roll 3, ... 1st intermediate roll, 4 ... 2nd intermediate roll 5 ... Backup roll 6 ... Roll bending apparatus

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Claims (2)

[Claims] 1. A multi-stage rolling mill in which a plurality of first intermediate rolls, second intermediate rolls and backup rolls are sequentially arranged behind a pair of work rolls, wherein the work rolls, the first intermediate rolls and the second intermediate rolls are provided. At least two rolls selected from the roll group consisting of rolls are given roll crowns covering at least one wavelength of the same wavy curve to each other, while at least two other rolls selected from the above roll group A roll crown having at least two wavelengths having the same wavy curve as each other is applied to a pair of rolls, and for each of the above-mentioned crown-providing roll pairs,
A multi-stage rolling mill characterized in that the roll axes are arranged so as to be opposite to each other and are incorporated in a mill housing so as to be movable in the roll axis directions. 2. A multi-stage rolling mill according to claim 1, comprising a roll bending device.