JPH05154509A - Hot finishing mill - Google Patents

Abstract

PURPOSE:To execute high-accuracy control of sheet crown that is defined as difference in thickness between the middle part of width and the vicinity part of edge of a sheet of rolled product and edge drop that thickness in the edge part of the sheet is reduced. CONSTITUTION:In a rolling mill which is provided with respective pairs of work rolls 2, intermediate rolls 3 and back-up rolls 4, each intermediate roll has the length of barrel longer than the length of barrel of the back-up roll 4, also sigmoidal roll crown is formed and the intermediate rolls 3 are mutually inversely arranged. Further, the barrel ends of the intermediate rolls 3 are connected to a shifting device 6 which is moved between the contact region with the back-up rolls 4 and the outside in the axial direction of the roll. On the other hand, each work roll 2 has the length of barrel equal to or shorter than that of the intermediate roll 3, also tapered parts where the diameters are gradually reduced toward the end sides are formed in the end parts of barrel on the mutual opposite sides, and then are connected to a shifting device 7 with which the work rolls 2 are mutually moved in the reverse direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot finish rolling mill for rolling a sheet bar rolled by a rough rolling mill to a product thickness, which is formed between a central portion of a rolled product sheet and a portion near an edge thereof. This is for controlling with high accuracy the plate couran defined as the plate thickness difference, and further the edge drop in which the plate thickness of the plate edge portion decreases.

[0002]

2. Description of the Related Art Generally, when a hot-rolled steel sheet is produced by a hot finish rolling mill, the thickness of the central portion of the sheet width becomes thicker than that of the edge portion due to the bending of the roll by the rolling load. On the other hand, the plate thickness at the edge portion becomes thin, and plate crowns and edge drops occur there. By the way, if the plate crown and the edge drop become large, it becomes difficult to provide an appropriate plate profile in the cold rolling of the next step, and the shape defect easily occurs, and the yield is unavoidably reduced. From that,
In the hot finish rolling mill, it is necessary to minimize the plate crown and the edge drop.

Therefore, for the purpose of reducing the plate crown, for example, as disclosed in Japanese Patent Publication No. 62-10722, a backup roll and a work roll are provided with a uniform diameter over the entire length of the roll. By installing an intermediate roll consisting of so-called flat rolls, and installing a 6-high rolling mill capable of shifting both intermediate rolls in their axial directions in opposite directions to each other, the crown control ability is improved. Enhanced rolling mill train, and Japanese Patent Laid-Open No. Sho 5
As disclosed in JP-A-7-91807, by imparting an S-shaped crown to any of a work roll, an intermediate roll or a backup roll, and shifting the roll having the S-shaped crown in the axial direction. Rolling mills with improved crown control capabilities have been proposed.

Further, Japanese Patent Application Laid-Open No. 55-77903 discloses that
When the work rolls are shifted cyclically, one side is used to suppress the increase in edge drop that occurs when the roll wear increases as the number of rolling processes increases and the center of the work roll becomes a trapezoidal profile. A method has been proposed in which a pair of work rolls whose ends are tapered are moved according to the width of the rolled material, and the side ends of the rolled material are rolled in the tapered grinding region of the work rolls.

[0005]

However, in the technique disclosed in Japanese Patent Publication No. 62-10722,
Since the length of the intermediate roll is about the same as the length of each of the backup roll and the work roll, when the intermediate roll is shifted to make the plate crown small, the intermediate roll, the backup roll, and the work roll are Since the contact length with the roll becomes short and the vertical rigidity of the rolling mill decreases, when the rolling load changes due to the temperature deviation of the sheet bar and other factors, the roll gap of the work roll changes significantly, and the specified plate thickness accuracy In addition, when the center of the strip width deviates from the center of the rolling mill due to bending of the sheet bar, etc., meandering occurs due to the difference in rigidity between the left and right sides of the rolling mill, and rolling becomes impossible due to narrowing. There was a problem with. In addition, due to the short contact length between the intermediate roll and other rolls, spalling occurs due to the increase in the linear pressure between the rolls, and there is another problem that the life of the rolls is shortened early. ..

Further, in the latter prior art disclosed in Japanese Patent Laid-Open No. 57-91807, for example, when profile control is performed by shifting a work roll provided with an S-shaped crown, schedule-free rolling is performed. During operation, there was a problem that crown control became impossible due to wear of the work roll.

Further, the technique disclosed in Japanese Patent Laid-Open No. 55-77903 is effective in reducing the edge drop, but it is disadvantageous in that it is difficult to control the profile over the entire width of the plate.

The present invention solves all of the problems of the prior art, prevents the reduction of the rigidity of the rolling mill and the meandering of the rolled material due to the shift of the intermediate roll, and controls the plate crown and the edge drop. It is intended to provide a hot finish rolling mill capable of maintaining high performance over a long period of time.

[0009]

The present invention is a rolling mill having a pair of work rolls, an intermediate roll and a backup roll, each intermediate roll having a barrel length longer than that of the backup roll. ,
An S-shaped roll crown is provided and the intermediate rolls are arranged in opposite directions, and a shift device for moving the barrel end of the intermediate roll between the contact area with the backup roll and the axially outer side of the roll is connected, Each work roll has a barrel length equal to or less than that of the intermediate roll, and at the barrel end portions opposite to each other, a tapered portion having a gradually smaller diameter toward the roll end side is provided, and the work rolls are moved in opposite directions. It is a hot finish rolling mill connected to a shift device.

Here, the S-shaped roll crown is obtained by extracting one pitch from a higher-order function curve of third or higher order,
The roll crown is defined as one obtained by extracting one pitch from a sinusoidal curve or a curve that is close to these curves.

[0011]

In this hot finish rolling mill, the intermediate rolls effectively reduce the rolling load acting on the respective side end portions of the sheet bar due to the presence of the S-shaped roll crown, which Becomes more remarkable when the respective intermediate rolls are point-symmetrically shifted in mutually opposite directions, so that the crown controllability can be greatly improved.

If the crown control amount is insufficient, the barrel end of the intermediate roll is further shifted toward the inner side in the axial direction of the barrel end of the backup roll, and the contact length between the rolls is increased. By shortening, the load distribution acting on each barrel end between the rolls can be advantageously reduced, and the crown controllability can be greatly improved. Such a shift condition is necessary especially when a rolling plate having a narrow width has to be rolled in a situation where the wear of work rolls in the latter half of the rolling cycle is large. That is, by shifting the barrel end of the intermediate roll to the inside of the barrel end of the backup roll, the linear pressure between the rolls is increased, and the non-contact portion is generated in each barrel between the intermediate roll and the backup roll and between the intermediate roll and the work roll. The vertical rigidity is minimized.

Therefore, regardless of whether or not there is a temperature difference between the sheet bars and regardless of the sheet bar width, the plate thickness accuracy can be sufficiently increased, and the bending moment acting on the work roll in the intermediate roll can be achieved. Can be realized to achieve a high degree of crown control even when the plate width is narrow.

Further, by rolling both edge portions of the rolled plate at the tapered portion of the work roll, the gap between the upper and lower work rolls becomes large, so that edge drop can be advantageously avoided.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated examples. FIG. 1 is a front view showing an embodiment of the present invention. Here, a pair of two work rolls 2, an intermediate roll 3 and a backup roll 4 are respectively arranged in the housing 1, and both work rolls 2 are axially moved by respective shift devices 5. And the intermediate rolls 3
By means of the other respective shift device 6, which can also be shifted in the opposite axial directions.

The backup roll 4 is constituted by a so-called straight roll having a uniform barrel diameter over the entire length, while the intermediate roll 3 has a barrel length longer than that of the backup roll 4 and has an S-shape as shown in FIG. It has a roll-shaped crown.

Here, as the curve for forming the S-shaped roll crown, as described above, one pitch is extracted from a higher-order function curve of third or higher order, and one pitch is extracted from a sine function curve. It is possible to select either the ones or curves that approximate those curves.

As shown in FIG. 1, the respective intermediate rolls 3 having such roll crowns are arranged in opposite directions to each other by the action of the shift device 6, and as shown in FIG.
As shown in (a) and (b) of FIG. 3, the shift positions are opposite to each other between the minimum shift position and the maximum shift position.
At the minimum shift position shown in (a), one barrel end 3a of the intermediate roll 3 is exactly aligned with one barrel end 4a of the backup roll 4, while at the maximum shift position shown in FIG. 3 (b). , The other barrel end 3b of the intermediate roll 3
, Is slightly recessed inward from the other barrel end 4b of the backup roll 4.

As is clear from the drawings shown in FIGS. 1 and 3, the work roll 2 is in contact with the thickened portion of the intermediate roll 3 at the opposite barrel end portions,
The roll has a taper portion 2a having a gradually smaller diameter toward the roll end side, and a roll having a continuous diameter portion 2b which is adjacent to the taper portion 2a and occupies most of the barrel length of the work roll.

When the respective rolls 2, 3 and 4 are configured as described above, in FIG. 1, the respective work rolls 2 are connected to the spindle 7 and the pinion stand 8
Are sequentially connected to the speed reducer 10 attached to the motor 9. Here, by the shift device 5 connected to the work roll 2 via the pinion stand 8 and the spindle 7,
The shift position of the work roll 2 can be, for example, a magnescale, and the shift position of the intermediate roll 3 by the shift device 6 connected to the intermediate roll 3 can also be, for example, a magnescale. Other position detecting devices 12 capable of detecting the respective positions are used. In the figure, 13 is a rolled plate as a product, 14 is a work roll bender, 15 is an intermediate roll bender and 1
Reference numerals 6 respectively indicate load cells.

FIG. 4 is a control system diagram of the rolling mill as described above. That is, reference numeral 21 in the drawing denotes an arithmetic unit. The arithmetic unit 21 has rolling conditions for one cycle, for example, the shape and size of the tapered portion of the work roll 2, the crown shape and size of the intermediate roll 3, the plate width, and the reduction of each stand. The rate, the finished plate thickness, the target plate crown, the target plate shape, and the like are input in advance, and the arithmetic unit 21 calculates the target plate crown and the target plate crown based on these information and the cyclic shift amount of the work roll 2. The shift amount of the intermediate roll 3 and the set values of the bending forces of the roll benders 14 and 15 are calculated in order to obtain the plate shape.

Based on the calculation result, the shift control device 22 and the bender control device 23 respectively control the operations of the shift device 6 and the roll benders 14 and 15 to control the shift amount of the intermediate roll 3 and the roll bending force. Each is set as a set value, and the start of rolling is awaited in such a state.

On the other hand, during rolling, the plate shape detector 24
And based on the feedback signal from the plate crown detector 25 to the arithmetic unit 21, the arithmetic unit 21 realizes the target plate shape and the target plate crown with high accuracy,
The shift amount of the intermediate roll 3 and the correction value of the bending force of each roll are calculated, and the shift control device 22 and the bender control device 23 determine the shift amount of the intermediate roll 3 and the roll bender based on the correction value. 14,
Adjust the bending force of 15.

In hot rolling with such a rolling mill, particularly under the action of the roll crown of the intermediate roll 3, it is possible to extremely effectively reduce the rolling load applied to the side end portion of the sheet bar from the work roll. Therefore, the plate crown can be controlled with high accuracy together with the actions of the roll benders 14 and 15, and the control range can be made sufficiently wide by shifting the intermediate roll 3. it can.

That is, considering a case where a pair of upper and lower intermediate rolls 3 each having an S-shaped roll crown are combined as shown in FIG. 5, both intermediate rolls when the shift amount of the intermediate roll 3 is set to zero. As shown in FIG. 6 (a), the synthetic roll crown of the roll 3 has a downward convex shape, and the rolling load acting on the work roll 2 from the intermediate roll 3 is
Depending on its composite crown shape, the side edges of the work roll 2 are considerably smaller than the central part, which can lead to a sufficiently high crown controllability. In addition, the respective intermediate rolls 3 are shifted in the opposite directions (+35
0 mm), the composite roll crown becomes a larger downward convex shape, as shown in FIG. 6 (b), and a sufficiently large crown control amount can be brought about.

By the way, the crown control amount is, as shown in FIG. 6, the maximum diameter D ₁ and the minimum diameter D of _one intermediate roll 3.
It can also be increased by increasing the difference ΔD from ₂ . By the way, in the present invention, the maximum diameter D ₁
When the difference ΔD between the minimum diameter D ₂ and the minimum diameter D ₂ is 0.8 mm, the crown control amount is as shown by the solid line in FIG. 7, and by shifting the intermediate roll 3 to 500 mm, the crown control amount is over a range of approximately 200 μm. It can be controlled and also the barrel end 3 of the intermediate roll 3
By shifting a by 700 mm inward of the barrel end 4a of the backup roll 4, a crown control amount over a range of approximately 250 μm can be obtained.

On the other hand, in the conventional 6-high rolling mill equipped with the intermediate roll having the uniform diameter of the straight roll, when the shift amount of the intermediate roll exceeds 350 mm, the meandering of the plate,
Due to the occurrence of diaphragms, the practical limit shift amount is 35
Since it is 0 mm, the plate crown can be controlled only within the range of approximately 150 μm.

FIG. 6 shows the results under the condition that the tapered portion 2a of the work roll 2 is arranged outside the plate edge portion. Next, the tapered portion 2 of the work roll 2 is shown.
The effect of reducing edge drop due to a will be described. That is, when the work rolls 2 are shifted in the opposite directions as shown in FIG. 8B from the posture of zero shift amount shown in FIG. 8A, the tapered portion 2a of the work rolls 2 is rolled. The length in contact with the plate 13, that is, the length EL from the taper starting point of the tapered portion 2a to the end of the rolled plate becomes long, so that the gap between the upper and lower work rolls also expands by the amount corresponding to the shift of the work roll 2, resulting in edge drop. Is reduced.

Here, 8 × 10 ⁻⁴ (1.6 m
FIG. 9 shows the relationship between the length EL and the edge drop change amount when the work roll 2 having a taper of m / 200 mm) is shifted and the length EL is changed. As is clear from the figure, the reduction amount of edge drop between 25 mm and 100 mm from the edge of the rolled plate has a nearly linear relationship with the length EL. From this relationship, as shown in FIG. The calculator 21 can calculate the shift amount of the work roll 2.

The contour shape of the tapered portion 2a of the work roll 2 is shown in FIG. 1 or 3 in order to obtain a suitable contact linear pressure distribution of the intermediate roll 3 which realizes a desired plate crown and edge drop amount. In addition to the tapered shape,
It is possible to use sine and cosine curves, both taper shapes, 2, 4, and 6th order curves shown in 0 (a) to (c), respectively.

Further, according to this rolling mill, even if the intermediate rolls are shifted under normal intermediate roll shift conditions (the barrel end 3a of the intermediate roll 3 is outside the barrel end 4a of the backup roll 4), the respective rolls are shifted. Since the contact length between rolls 2, 3, and 4 does not change at all and the longitudinal rigidity of the rolling mill does not change, the plate thickness accuracy of hot finish rolling is greatly improved and the line pressure between rolls is excessively increased. Is prevented. Even if the width center of the sheet bar deviates from the center of the rolling mill, the change in linear pressure on the left and right sides of the rolling mill will be smaller than before, suppressing flattening between rolls and eventually reducing the plate edge. Therefore, plate bending can be effectively reduced.

When the plate width is relatively narrow and the target crown is small, it has already been described that the barrel end 3a of the intermediate roll 3 is shifted inward from the barrel end 4a of the backup roll 4 to perform crown control. The shift amount here is smaller than the conventional shift amount, and under such shift conditions, since the strip width is narrow and the rolling load is small, the vertical rigidity of the roll and the meandering of the strip are hardly affected.

[Specific Example] Hereinafter, a comparative test regarding the plate crown distribution with respect to the number of rollings and the like when the rolling mill according to the present invention is used and when the conventional rolling mill is used will be described. Inventive rolling mill In a rolling mill train in which the finishing rolling mill having the configuration shown in FIG. 1 is arranged in the rear three stands, a sheet bar having a width of 900 to 1600 mm and a thickness of 40 mm and a finishing thickness of 1.6 to 3.2
It was rolled into a thin low-carbon steel having a thickness of mm, and the plate crown was measured at a position of 25 mm from the edge every 5 coils. Here, the barrel length of the work roll is 2300 mm, the barrel length of the intermediate roll is 2800 mm, the barrel length of the backup roll is 2300 mm, and the tapered portion of the work roll is 8 × 10 ⁻⁴ (1.6 mm / 200 mm). At the point where the taper was given, the diameter difference between the maximum diameter and the minimum diameter of the intermediate roll was set to 0.8 mm, and the intermediate roll was set to 0 mm.
The shift range was from mm to 700 mm.

A conventional three-stage rolling mill including the final stand of the rolling mill was provided with a six-high rolling mill, each of which was composed of a flat roll and had a work roll having a barrel length of 2300 mm, an intermediate roll and a backup roll. Meanwhile, while shifting the intermediate roll, the same hot rolling as in the case of using the invention rolling mill was performed, and the same sheet crown measurement as that case was performed.

Test Results These measurement results are shown in FIG. According to the figure, when the rolling mill of the present invention is used, it is clear that even if the target crown is changed, highly precise strip rolling can be performed very close to it. The rolling schedule for the strip width was the same for both the invention rolling mill and the conventional rolling mill.

Further, when the invention rolling mill and the conventional rolling mill are used to roll 100,000 tons in a thin product cycle, the number of times of drawing, the plate thickness accuracy and the plate crown average value are as shown in Table 1. According to the invention, the invention rolling mill was far superior to the conventional rolling mill in terms of strip thickness accuracy and sheet passing property (reduction of drawing).

[0037]

[Table 1]

[0038]

According to the present invention, the target plate shape having the desired plate crown and the edge drop can be achieved with high accuracy, the yield in the cold rolling of the next process can be improved, and at the same time, Stable rolling can be performed.

[Brief description of drawings]

FIG. 1 is a front view showing a rolling mill of the present invention.

FIG. 2 is a diagram showing a roll crown of an intermediate roll.

FIG. 3 is a diagram showing a shift state of an intermediate roll.

FIG. 4 is a control system diagram of the rolling mill of FIG.

FIG. 5 is a view showing a combined state of upper and lower intermediate rolls.

FIG. 6 is a view showing a synthetic roll crown of upper and lower intermediate rolls.

FIG. 7 is a graph showing a crown control amount.

FIG. 8 is a view for explaining the action of the tapered portion of the work roll.

FIG. 9 is a graph showing the relationship between work roll shift and edge drop change amount.

FIG. 10 is a view showing a shape of a tapered portion of a work roll.

FIG. 11 is a graph showing a distribution state of a plate crown with respect to the number of rolled lines.

[Explanation of symbols]

 1 Housing 2 Work Roll 2a Tapered Part 2b Uniform Diameter Part 3 Intermediate Roll 3a Intermediate Roll Barrel End 3b Intermediate Roll Barrel End 4 Backup Roll 4a Backup Roll Barrel End 4b Backup Roll Barrel End 5 Shift Device 6 Shift Device

Claims (1)

[Claims] 1. A rolling mill comprising a pair of work rolls, an intermediate roll and a backup roll, each intermediate roll having a barrel length longer than that of the backup roll and having an S-shaped roll crown. Each of the work rolls is provided with an intermediate roll, and the intermediate rolls are arranged in opposite directions, and further, the barrel end of the intermediate roll is connected with a shift device that moves between a contact area with the backup roll and the axial outside of the roll. It has a barrel length equal to or less than that of the above, and at the barrel end portions on the opposite sides to each other, a tapered portion having a gradually smaller diameter toward the roll end side is provided, and further connected to a shift device that moves the work rolls in opposite directions. Hot finishing rolling machine.