JP3068980B2 - Rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling mill having a high crown control ability capable of preventing surface roughness.

[0002]

2. Description of the Related Art In recent years, as a measure for reducing the weight of a vehicle body for reducing fuel consumption of a vehicle, a change in material by adopting a high-strength steel plate and the like have been attempted in addition to a reduction in the size of the vehicle body. Above all, reducing the weight of cold-rolled steel sheets used for automobiles and wheels by reducing the thickness is extremely effective in reducing fuel consumption. However, in order to reduce the thickness of the steel sheet, the strength is reduced, and high dent resistance is required. Therefore, application of a high-strength hot-rolled steel sheet to a wheel rim, a disk, or the like is being studied intensively.
As a result, the use of thin high-tens has been promoted, and the need for thin high-tens has increased.

On the other hand, in applying a high-strength hot-rolled steel sheet to a wheel rim, a disk, or the like, for example, a wheel rim is formed by forming a steel sheet cut into a predetermined width and length into a ring shape. It is required to have a uniform thickness in the width direction for the purpose of preventing molding defects. As in this case, it is required to reduce the crown of a high-strength hot-rolled steel sheet made of a high-tensile sheet.

[0004] As described above, the demands of customers for the thickness accuracy and flatness of hot-rolled steel sheets and cold-rolled steel sheet products are becoming more severe. In particular, in order to satisfy the performance of products for end use in high-tensile steel sheets,
Or, in reality, strict plate thickness accuracy is required in order to satisfy smooth workability in a machining process line with advanced automation.

[0005] Under these circumstances, as a rolling mill for a thin steel sheet for reducing the production cost of a low crown of high-tensile steel, CVC (Co
ntinoosly Variable Crown)
Rolling mills using rolls have been proposed. For example, in Japanese Patent Publication No. 63-62283, an initial crown having substantially the same shape is provided to upper and lower work rolls so as to be symmetrical with respect to each other, and the upper and lower work rolls are moved symmetrically in the axial direction to reduce the roll gap. It has been proposed that the crown and flatness of the rolling mill be easily controlled over a large range with a small number of rolls so as to be configured to change in point symmetry.

Japanese Patent Application Laid-Open No. 58-187208 discloses that a reinforcing roll and a work roll
With contours that are curved to fit each other,
A roll stand is disclosed in which the rolls of these roll pairs are slidable in the mutual direction and / or axially relative to the rolls of the other roll pair. Further, Japanese Patent Laid-Open No. 1-2
No. 66902 discloses a pair of supported two work rolls which are not slidable in the axial direction. In this case, these work rolls are slidable in the axial direction with respect to each other. In a rolling mill in which the rolls supporting the work rolls are cylindrical, the rolls are formed according to the contours that are curved over the entire length of the cylinder, and the curved contours of the two work rolls are formed to complement each other. Machine has been proposed.

[0007]

The above-described sheet crown control by the CVC mill is extremely excellent in that a large sheet crown control effect can be obtained with a relatively small roll shift amount. If the diameter difference of the CVC roll curve is increased to increase the capacity, the peripheral speed difference between the backup roll and the work roll becomes large, and this causes the surface roughness phenomenon peculiar to CVC to occur on the roll, thereby increasing the crown control ability. There is a problem that can not be.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have intensively developed and as a result, determined the optimum conditions of the roll curve on the roll body length without reducing the crown control ability. Rolls, ie CRS
Another object of the present invention is to provide a rolling mill using (Curved Roll Shift). The gist of the invention is to provide a rolling mill in which crowns of substantially the same shape are provided on each of an upper roll and a lower roll so as to be point-symmetrical to each other, and are provided so as to be movable in the axial direction with respect to each other. When the maximum length D of the convex portion, the minimum diameter d of the concave portion, and the roll length on which the roll curvature surface curved in an uneven shape is L,
(D−d) / L ³ so as to maintain the large crown control ability
> 1.16 × 10 ⁻⁸ , and (D−d) <1.6 so as to reduce the peripheral speed difference between the rolls.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a quadruple rolling mill according to the present invention. As shown in FIG. 1, both backup rolls 2, 2 'of backup rolls 2, 2' are provided in a roll stand 1.
Are guided by the chocks 3, 3 '. Work roll pairs 4 and 4 ′ are provided between the backup rolls 2 and 2 ′, and the work roll pairs form a roll gap 6 for the steel plate 5. The reduction of the work rolls 4 and 4 ′ for determining the width of the roll gap 6 is performed by a reduction device 7 provided on the chocks 3 and 3 ′ of the backup rolls 2 and 2 ′.
Done by

With such a construction, the backup rolls 2 and 2 'of the backup roll pair 2, 2' can be shifted axially through their roll necks.
And in the case of this quadruple rolling mill, the two work rolls 4, 4 'have a contour which is curved over their entire length. In this case, the left half of the roll cylinder of the work roll 4 has a convex curved profile, while the right half has a concave curved profile. Conversely, the left half of the roll cylinder of the lower work roll 4 'has a concavely curved profile, while its right half has a convexly curved profile. In this case, the two roll cylinder parts are determined by an equal curve ratio.

As can be seen from FIG. 1, the backup roll 2 of the backup rolls 2 and 2 'has a cylindrical shape. The rolls are supported by the cylindrical roll cylinder of ′, and these rolls are deformed, which leads to a significant curvature of the roll cylinder profile in the direction of the roll gap 6. For this reason, work rolls 4, 4
The rolled profile of the roll cylinder 'is defined by a curvature having a relatively large radius of curvature. The relative S-shaped curvature of the work rolls 4 and 4 ′ in the direction of the roll gap 6 of the roll cylinder is determined by the steel plate 5. Roll gap 6
A shift in the axial direction of one or both of the work rolls 4, 4 'is carried out in order to change the formation of.

FIG. 2 is a schematic sectional view showing another embodiment of a quadruple rolling mill according to the present invention. 1 is a quadruple rolling mill similar to FIG. 1, wherein backup rolls 2, 2 ′ roll cylinders have a curved profile over their entire length. In this case, the left half of the roll cylinder of the backup roll 2 has a convex curved profile, while its right half has a concave curved profile. On the contrary, the lower backup roll 2 '
Has a concave curved profile, while its right half has a convexly curved profile. In this case, the two roll cylinder parts are determined by an equal curve ratio. As can be seen from FIG. 2, the crowns of the work rolls 4 and 4 'themselves have a cylindrical shape, but the S-shaped bending is inevitably forced by the pressure of the backup roll.

FIG. 3 is a schematic sectional view showing still another embodiment of a quadruple rolling mill according to the present invention. As shown in FIG.
In the case where both the work roll and the backup roll use a CRS roll having an uneven curved profile, the upper and lower work rolls having a curve are shifted in the axial direction, and the backup roll is a fixed or shifted type. .

FIG. 4 is a sectional view showing an embodiment of a six-high rolling mill according to the present invention. In this rolling mill 8, in addition to the backup rolls 2, 2 ′ of the backup rolls 2, 2 ′ and the work rolls 4, 4 ′ of the pair of work rolls 4, 4 ′ in the roll stand 1, an intermediate roll Versus 9, 9 '
The two intermediate rolls 9 and 9 'are provided. Backup roll 2 and 2 'of backup roll pair 2, 2'
Are guided in the roll stand 1 by the chocks 3 and 3 '. On the other hand, intermediate rolls 9 and 9 of intermediate rolls 9 and 9 '
′ Are also carried in the chocks 10 and 10 ′, which are guided in the chocks 3 and 3 ′ for the backup rolls 2 and 2 ′.

In the case of this six-high rolling mill, only the intermediate rolls 9 and 9 'are provided so as to be able to shift in the axial direction. On the other hand, backup roll pair 2 and backup roll 2 of 2 '
And 2 'and work roll pairs 4 and 4' and work rolls 4 and 4
´ is supported without shifting. In this case, the intermediate roll has an uneven curved contour. However, the present invention is not limited to this. The backup roll may have an uneven curved contour. Also, the intermediate rolls 9, 9 '
Are guided in the chocks 3 and 3 'for the backup rolls 2 and 2'.

FIG. 5 is a schematic sectional view showing another embodiment of the six-high rolling mill according to the present invention. As shown in FIG. 5, the work roll is shifted by using a shape roll having an uneven curved profile, and at the same time, a roll having a cylindrical shape or an uneven curved profile is used as an intermediate roll. It is also possible to perform either fixed or shift. Further, the backup roll may be any roll having a cylindrical shape or a contour curved in a concave and convex shape like the intermediate roll, and is not limited to any one of fixed or shiftable. Based on the configuration of the rolling mill as described above, all of these rolling mills are defined as CRSs, and the present invention is applied to all of these CRSs.

FIG. 6 is a cross-sectional view of a roll having an irregularly curved profile, which is an example according to the gist of the present invention.
Assuming that the maximum diameter D of the convex portion and the minimum diameter d of the concave portion in the curved roll and the length of the roll on which the curvature surface of the roll curved in an uneven shape is L, the crown control ability △ Cr Is proportional to (D−d) and inversely proportional to L ³ . Therefore, it can be expressed by the equation of ΔCr = K (D−d) sW ² / L ³ . Here, K is a constant, s is the shift amount, and W is the plate width. Therefore, as a result of elucidating the cause of the occurrence of skin roughness peculiar to CRS, the roll of the present invention is centered on the roll center in the body length direction, as is clear from FIG. 7 showing the surface pressure, peripheral speed difference and PV value in the body length direction of the roll. It can be seen that, unlike the normal roll, the concave and convex concave portions have a low surface pressure (P) and the convex portions have a high surface pressure.

Similarly, the difference in peripheral speed between rolls (ΔV) shows that the concave portions and the convex portions are opposite to each other about the roll center. Therefore, the curve of the P △ V value indicating the value of μ × P × △ V is as shown in FIG. Here, μ is a coefficient of friction. As can be seen from this figure, it has been clarified that the rough surface of the rolling roll occurs not at the boundary between the uneven portions nor at the position where the surface pressure is high, but at the position where the μP △ V value is maximum. That is, it has been quantitatively clarified that the position where the specific skin roughness occurs occurs at the maximum position of the μP △ V value on the left side of the roll center in the roll body length direction.

FIG. 8 is a diagram showing the relationship between the crown control ability and the maximum peripheral speed difference between rolls. As shown in FIG.
It can be seen that the crown control ability decreases as the value of D-d (mm) decreases. Therefore, it is necessary to increase the Dd value in order to enhance the crown control ability. But,
If the Dd value is increased and exceeds 1.6 or more, the rolling roll becomes rough and the crown control ability cannot be further improved.

On the other hand, if the maximum peripheral speed difference between the rolls is reduced, even if the diameter difference (D−d) is large, the surface of the rolling rolls will not be roughened as described above. According to the present invention, the diameter difference (D-d) of the roll curved in an uneven shape is reduced by reducing the diameter difference (D-d) to reduce the crown control ability. The crown control ability can be maintained by reducing the maximum peripheral speed difference between the rolls and shortening the roll curve imparting length L having the curvature surface of the roll curved in an uneven shape. That is, when the crown control ability is D−d ≧
In order to reduce the difference in peripheral speed, the range of the curved portion on the roll body length L was reduced to D-d / L ³ > 1.16 × 10 ⁻⁸ while reducing the peripheral speed difference. By using a roll curve, it became possible to prevent roughening of the rolling roll.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plate width of 938 was obtained by using a quadruple rolling mill of an initial crown roll for the upper and lower work rolls of the first to third stands of the finishing mill of a tandem hot rolling mill.
mm, shift stroke of upper and lower work rolls 300m
m, a rolling load of 3800 tons, and a roll speed of 180 mpm. Table 1 shows the conditions of the upper and lower work rolls for the initial crown roll and the conventional roll.
Shown in As shown in Table 1, in the case of the conventional roll, roughening occurred in the range of 100 mm to 400 mm on the smaller diameter side than the roll center. In contrast, the roll of the present invention did not show any roughening.

[0022]

[Table 1]

As described above, in a rolling mill using a CRS, although it has a particularly large uneven contour, the characteristic roughness of the surface is expressed by μP △ V value (friction coefficient × surface pressure ×
The concept of (peripheral speed difference) was able to elucidate quantitatively. That is, by reducing the μP △ V value, it became possible to prevent the roll from being roughened. Therefore, in order to reduce the μP △ V value, the CRS curve length L is shortened instead of merely reducing the diameter difference which is the difference between the maximum diameter of the convex portion and the minimum diameter of the concave portion of the uneven curved roll. As a result, the surface pressure can be kept constant, the peripheral speed difference can be reduced, and the occurrence of roll body roughness can be prevented while maintaining high crown control ability.

[0024]

As described above, according to the present invention, while maintaining the crown control ability at a high position without lowering the crown control ability, there is no peculiar roughness, and the thickness in the width direction is uniform. Is applicable to all steel grades, and high crown control ability is possible. Therefore, SFR (Schedule Fre
e Rolling), and at the same time, an extremely excellent effect of greatly reducing the fuel consumption rate and reducing the cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a quadruple rolling mill according to the present invention,

FIG. 2 is a schematic sectional view showing another embodiment of a quadruple rolling mill according to the present invention,

FIG. 3 is a schematic sectional view showing still another embodiment of a quadruple rolling mill according to the present invention,

FIG. 4 is a sectional view showing an embodiment of a six-high rolling mill according to the present invention;

FIG. 5 is a schematic sectional view showing another embodiment of the six-high rolling mill according to the present invention,

FIG. 6 is a cross-sectional view of a roll having an unevenly curved profile;

FIG. 7 is a diagram showing a surface pressure, a peripheral speed, and a PV value in a roll body length direction;

FIG. 8 is a diagram showing a relationship between a crown control ability and a maximum peripheral speed difference between rolls.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Roll stand 2, 2 'Backup roll 3, 3' Chock 4, 4 'Work roll 5 Steel plate 6 Roll gap 7 Rolling-down device 8 Rolling machine 9, 9' Intermediate roll 10, 10 'Chock which supports intermediate roll

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-154509 (JP, A) JP-A-5-154508 (JP, A) JP-A-5-104112 (JP, A) 245506 (JP, A) JP-A-6-285518 (JP, A) JP-A-5-185107 (JP, A) JP-A-5-177218 (JP, A) JP-A-1-284410 (JP, A) JP-A-1-262008 (JP, A) JP-A-63-20106 (JP, A) JP-A-2-268910 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 29/00 B21B 13/14 B21B 27/02 B21B 31/18

Claims (1)

(57) [Claims] 1. A rolling mill in which upper and lower rolls are provided with crowns of substantially the same shape and irregularities so as to be point-symmetric with respect to each other, and are provided so as to be movable in the axial direction with respect to each other. When the length of the roll having the maximum diameter D, the minimum diameter d of the concave portion, and the roll curvature surface curved in an uneven shape is L, the large crown control ability is maintained (D−
d) / L ³ > 1.16 × 10 ⁻⁸ , and (D−d) <1.6 so as to reduce the peripheral speed difference between rolls.