JP3627366B2 - Steel sheet hot rolling mill and hot rolling method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin steel sheet hot rolling mill and a continuous hot rolling method.
[0002]
[Prior art]
Generally, a hot-rolled steel sheet is a slab heated to a predetermined temperature and rolled to a predetermined thickness with a roughing mill to form a rough bar, and then the rough bar is a continuous hot rolling mill composed of a plurality of rolling stands. It is manufactured by finish rolling into a hot-rolled steel sheet having a predetermined thickness.
[0003]
In the rolling operation of the steel sheet in such a continuous hot rolling mill, when the material to be rolled is caught in the rolling mill or when the material comes out of the rolling mill, the material is bent in the width direction to the rolling mill. There is a problem of so-called plate instability such that the material is not bitten or the material breaks and damages the roll.
[0004]
In order to prevent the problems described above, conventionally, the running state of the material between the rolling mills during the previous rolling was observed, and the difference in the sheet width direction of the roll gap was changed to stabilize the rolling.
[0005]
However, such a method relies on the experience and intuition of the rolling mill operator, and the results are not necessarily accurate, so various studies have been made on its improvement. For example, Japanese Patent Laid-Open No. 61-219411 focuses on the deviation in the width direction of the steel sheet and the difference in the width direction of the rolling load, and gives the difference in the width direction of the roll gap according to the difference in the rolling load. A method for avoiding plate instability (hereinafter referred to as Prior Art 1) is disclosed.
[0006]
Japanese Laid-Open Patent Publication No. 61-143016 discloses a method (hereinafter referred to as Prior Art 2) for measuring the position in the width direction between rolling stands of materials and operating the width direction difference of the roll gap. Yes.
[0007]
Further, in Japanese Patent Laid-Open No. 4-210808, the displacement of the roll bearing box is measured so that the clearance between the work roll bearing box and the rolling mill housing metal is controlled to a certain value or less. A method (hereinafter referred to as Prior Art 3) of exchanging the liner metal when exceeding is disclosed.
[0008]
[Problems to be solved by the invention]
Since the hot rolling of the steel sheet by the continuous hot rolling mill is performed at a high speed of 1500 m / min or more, the above-mentioned problem of instability of the sheet passing is about 0.2 seconds between the rolling stands at an interval of about 5.5 m. Since it occurs in a very short time, the desired effects cannot be achieved by the prior arts 1 and 2.
[0009]
Furthermore, the factors causing the rolling load difference are not only the deviation in the width direction of the material to be rolled, but also the distribution in the width direction of the sheet thickness, the deviation in the width direction of the material temperature, and the difference in elastic deformation characteristics of the rolling mill itself. It is conceivable and it is difficult to solve depending on the prior arts 1 and 2 because it is necessary to appropriately classify these factors.
[0010]
According to the prior art 3, the stability of rolling can be obtained by restraining the displacement of the bearing box, but a certain amount of clearance is necessary from the viewpoint of workability at the time of changing the roll gap for roll thickness control or roll reassignment. In addition, it is not clear in what circumstances the roll bearing moves, and there is a possibility of unnecessary repair work.
[0011]
Accordingly, an object of the present invention is to solve the above-mentioned problems, and in a continuous hot rolling operation of a steel sheet, when the material to be rolled is caught in the rolling mill or when the material comes out of the rolling mill, Prevents the occurrence of so-called plate feed instability, which is bent in the width direction and does not get caught in the rolling mill, or the material breaks and damages the roll, and the steel plate is stably rolled in a good state. An object of the present invention is to provide a hot rolling mill and a continuous hot rolling method capable of producing a high-quality thin steel sheet with high yield.
[0012]
[Means for Solving the Problems]
From the above-mentioned viewpoints, the present inventors have conducted intensive research to develop a method capable of accurately preventing the occurrence of plate instability in continuous hot rolling of a steel sheet in a continuous hot finishing rolling mill. As a result, if the work roll of the rolling mill is positioned stably so as not to move in the axial direction and the rolling direction of the roll before and after rolling or during rolling, the above-mentioned plate instability can be dramatically improved. I understood.
[0013]
As shown in FIG. 2, the work roll 1 is usually arranged with a so-called offset a that shifts the relative position of the backup roll 2 in the rolling direction. Although the offset amount is usually 5 mm or more depending on the strength of the bearing, the work roll 1 is placed in a direction in which the offset a is given by the contact force of the backup roll 2 by providing such an offset a. It is believed to be stable when pressed.
[0014]
However, it has been observed that movement occurs in the work roll 1 during actual rolling, especially when the material bites into or out of the rolling mill. Such a movement of the work roll is a behavior that cannot be considered in a normal force relationship, and thus the cause has not been clarified conventionally.
[0015]
Thus, as a result of conducting research from a detailed point of view in actual operation in order to elucidate the cause, it has been found that the work roll movement phenomenon occurs as follows.
[0016]
In other words, it is inevitable that the upper and lower work rolls have a small diameter difference. After the material comes out of the rolling mill, the upper and lower work rolls come into contact with each other, so that the upper and lower work rolls have a difference in diameter. Torque in the opposite direction is generated according to each. As a result, a phenomenon occurs in which one of the upper and lower work rolls moves in the direction opposite to the direction pressed during rolling.
[0017]
The phenomenon described above is that the rolling mill is an elastic body, so that a large rolling load generated during rolling causes elastic deformation and the roll gap widens, and at the end of rolling, the elastic deformation returns to the original and the roll gap becomes small. It is likely to occur when the finished sheet thickness of the rolled material is thin and the set value of the roll gap is small.
[0018]
It has been confirmed that the pressing force of the work roll due to the torque described above is several times the pressing force generated by the offset with the backup roll, and the pressing force of the work roll due to the torque is opposite to the pressing direction due to the offset. If it works in the direction, the bearing box will move easily.
[0019]
On the other hand, in rolling by a hot finish rolling mill, it is known that the front end portion and the rear end portion of the rolled steel sheet are not maintained in a rectangular shape, but have a tongue shape or a fish tail shape. In addition, since the rolled material has various asymmetries in the width direction, when it is bitten into the rolling mill or exits from the rolling mill, rolling does not start or end in the width direction at the same time. .
[0020]
That is, when the rolled material is bitten, the upper and lower work rolls are not necessarily in the non-contact state simultaneously from the contact state to the entire roll length direction of the roll, and may partially move in the offset direction first. Similarly, when the rolled material comes out, the upper and lower work rolls do not contact the entire body length direction at the same time, and partly moves in the direction opposite to the offset first.
[0021]
As shown in FIG. 3, the lower work roll 1a is larger in diameter than the upper work roll 1b, and when the offset of such work rolls 1a, 1b is set to the rolling direction exit side indicated by the arrow, The upper and lower work rolls 1a and 1b are pressed against the exit side in the rolling direction during steady rolling.
[0022]
However, when the setting of the roll gap of the work rolls 1a and 1b is small, the work rolls 1a and 1b are in contact with each other because there is no rolling load in a state in which rolling is not performed, and the lower large-diameter work roll 1a is Due to the frictional force or torque received from the upper small-diameter work roll 1b, the upper work roll 1b moves so as to be pressed against the entry side in the rolling direction as indicated by arrow A, and the upper work roll 1b receives the frictional force or torque received from the lower work roll 1a. As shown by the arrow B, it moves so as to be pressed toward the rolling direction exit side.
[0023]
When the work rolls 1a and 1b move in this way, when the backup rolls 2a and 2b are in contact with the work rolls 1a and 1b with an offset, the work rolls 1a and 1b are rotated around the backup rolls 2a and 2b. The roll gap also changes.
[0024]
That is, if the amount of movement of the work roll in the rolling direction is different in the sheet width direction, the change in the roll gap will also be different in the sheet width direction, and as a result, the rolling reduction will be different in the sheet width direction. It is considered that the plate is bent in the width direction and the instability of the passing plate as described above occurs.
[0025]
This invention is made based on the knowledge mentioned above, and consists of a pair of upper and lower work rolls and a backup roll, and one of the pair of upper and lower work rolls is in the rolling direction entry side with respect to the backup roll. The other of the work rolls is offset relative to the backup roll toward the exit side in the rolling direction. In the steel sheet hot rolling mill, the diameter of the one work roll arranged with an offset toward the entry side in the rolling direction with respect to the backup roll is arranged on the exit side in the rolling direction. It is characterized in that it is larger than the diameter of the other work roll that is arranged with a directed offset .
[0026]
The diameter of the one work roll arranged with an offset toward the entry side in the rolling direction with respect to the backup roll is the diameter of the other work roll arranged with an offset towards the exit side in the rolling direction. It is preferable that it is larger within a range of 0.1 to 1 mm.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Since the movement of the work roll basically occurs by the mechanism described above, when the work roll offset is set on the outgoing side in the rolling direction, the small diameter work roll is always pressed against the outgoing side in the rolling direction. Even if no measures are taken, there is almost no movement in the work roll.
[0028]
On the other hand, in the large-diameter side work roll, during rolling, it is pressed against the rolling direction exit side, and when the material comes out of the rolling mill and the upper and lower work rolls come into contact with each other, it seems to be pressed against the entrance side in the rolling direction. Move to.
[0029]
Therefore, in the present invention, in order to eliminate the above-described fluctuation of the work roll, the backup roll is arranged so that the large-diameter side work roll is pressed against the entry side in the rolling direction even during rolling. On the other hand, the offset was shifted toward the entry side in the rolling direction.
[0030]
FIG. 1 is a schematic side view showing an example of the arrangement of work rolls in the present invention. As shown in FIG. 1, the diameter of the lower work roll 1a is larger than the diameter of the upper roll 1b. Such a large-diameter lower work roll 1a is arranged with an offset a shifted from the lower backup roll 2a toward the entry side in the rolling direction. The small-diameter upper work roll 1b is arranged with an offset b shifted from the upper backup roll 2b toward the outgoing side in the rolling direction.
[0031]
As a result, since the large-diameter lower work roll 1a is in a state of being pressed against the entry side in the rolling direction even during rolling, the material comes out of the rolling mill and the upper and lower work rolls 1a and 1b are in contact with each other. Even if it will be in a state, it will not occur that work roll 1a, 1b moves to the rolling direction entrance side.
[0032]
The difference in diameter between the upper and lower work rolls 1a and 1b is set to 0.1 mm or more in consideration of the difference in thermal expansion of the rolls. In terms of torque, it is considered that there is no problem even if the difference in roll diameter is large, but if the difference in roll diameter exceeds 1 mm, slippage at the time of contact may increase and the roll surface may be damaged. Arise. Therefore, the difference between the diameters of the work rolls 1a and 1b should be within a range of 0.1 to 1 mm. A preferable diameter difference between the work rolls 1a and 1b is about 0.5 mm.
[0033]
According to the present invention, the effect is exhibited even when there is play in the bearing other than the clearance between the roll chock and the housing that can be measured and managed. With the conventional method of managing the clearance between the roll chock and the housing or the method of restraining the chock only, there is a backlash in the bearing. The work roll cannot be stabilized because it moves to the entry side by the amount combined with the backlash.
[0034]
In the present invention, the horizontal force applied to the work roll does not change in a constant direction for each chock regardless of whether it is rolling or non-rolling. It can be held in a stable position in the direction.
[0035]
For example, as shown in FIG. 1, the diameter of the lower work roll 1a is 0.5 mm larger than the diameter of the upper roll 1b, and the lower backup roll 2a of the lower work roll 1a having such a large diameter is used. The steel sheet was hot-rolled by setting the offset a toward the entry side in the rolling direction to 6 mm and the offset b toward the exit side in the rolling direction with respect to the upper backup roll 2b of the small-diameter upper work roll 1b in the same manner as 6 mm. As a result, the work roll recombination frequency due to instable sheeting is reduced to about ¼ compared to the conventional case, and the instability of sheet passing due to the horizontal movement of the work roll in the finishing mill is eliminated, Rolling stability could be improved dramatically.
[0036]
【The invention's effect】
As described above, according to the present invention, in the continuous hot rolling operation of the steel sheet, when the material to be rolled is caught in the rolling mill or when the material comes out of the rolling mill, the material is in its width direction. It can prevent the occurrence of so-called plate instability, such as bending into a rolling mill and preventing it from biting into the rolling mill or damaging the rolls, and can stably roll the steel plate in good condition. Thus, an industrially useful effect is obtained that can produce a thin steel sheet having excellent quality with a high yield.
[Brief description of the drawings]
FIG. 1 is a schematic side view showing a work roll portion in the present invention.
FIG. 2 is a schematic side view showing offset of a work roll.
FIG. 3 is a schematic side view showing a horizontal force received by the upper and lower work rolls when the upper and lower work rolls come into contact with each other.
[Explanation of symbols]
1 Work Roll 1a Lower Work Roll 1b Upper Work Roll 2 Backup Roll 2a Lower Backup Roll 2b Upper Backup Roll

Claims (3)

It consists of a pair of upper and lower work rolls and a backup roll, and one of the pair of upper and lower work rolls is arranged with an offset that is shifted relative to the backup roll toward the entry side in the rolling direction. And the other of the work rolls is disposed with an offset that is shifted relative to the backup roll toward the exit side in the rolling direction.
The diameter of the one work roll arranged to give an offset toward the rolling direction entry side with respect to the backup roll is the other work roll arranged to give an offset toward the rolling direction exit side. A steel sheet hot rolling mill characterized by being larger than the diameter . The steel sheet hot rolling mill according to claim 1 , wherein a diameter of the one work roll is larger than a diameter of the other work roll within a range of 0.1 to 1 mm . In a hot rolling method of a steel sheet, in which a material is continuously hot rolled onto a steel sheet by a continuous hot rolling mill comprising a plurality of rolling stands, one of the upper and lower pair of work rolls of the rolling mill is set against a backup roll. An offset with the position relatively shifted toward the entry side in the rolling direction is provided, and the other of the work rolls is shifted relative to the backup roll toward the exit side in the rolling direction. The diameter of one work roll disposed with an offset toward the entry side in the rolling direction and the diameter of the other work roll disposed with an offset toward the exit side in the rolling direction. Daito none than, thereby, allowed to ensure horizontal stability of the work roll during rolling, it has to continuously rolled steel sheet stably Wherein hot rolling method of steel plate.

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