JP5929048B2 - Hot rolling method - Google Patents

Description

  The present invention relates to a method for hot rolling steel.

  In the rolling mill, a thrust force in the width direction of the rolling material (thrust force in the width direction) is generated on the rolling roll due to the asymmetry of the rolling material or the crossing of the axis of the rolling roll. This thrust force is supported by the housing via a keeper plate (see, for example, Patent Document 1).

  This thrust force is not preferable in terms of equipment maintenance, and to reduce this thrust force, conventionally, it has been reduced by a method of spraying or applying a lubricant to at least one of a work roll and a backup roll (for example, Patent Document 2).

  In the pair cross mill, there is a method of setting the cross angle between the backup rolls to be smaller than the cross angle between the work rolls in order to reduce the thrust force generated between the work roll and the backup roll. (For example, refer to Japanese Patent Laid-Open Publication No. 2003-259542).

JP-A-57-202909 JP 03-234305 A JP 58-157504 A

  However, although the method described in Patent Document 2 is effective in reducing the undesired thrust force in terms of equipment maintenance, there is a problem that the thrust force due to asymmetry that occurs during rolling cannot be reduced. Causes of asymmetry include deviation of the intersection of the upper and lower work roll axes, that is, the cross point from the geometrically normal position, and the occurrence of a rolling load difference in the width direction of the rolled material, that is, a differential load. There is also a problem that uneven wear occurs in the rolling roll due to the occurrence of the differential load due to the thrust force.

  In the method described in Patent Document 3, the axis of the work roll and the backup roll is generally offset in the rolling direction, and the thrust force can be reduced by reducing the cross angle of the backup roll. The position of the work roll in contact with the backup roll is changed from the normal position, which adversely affects the crown control, shape, and sheet passing property of the rolled material. In general, the pair cross mill is more strictly managed than the other mills because the positions of the backup roll and the work roll are strictly controlled. Therefore, it is not preferable in operation to change the cross angle of only the backup roll.

  The present invention has been made in view of the circumstances as described above, and provides a hot rolling method capable of appropriately canceling the thrust in the width direction generated in a rolling roll when hot rolling steel. It is intended.

  In order to solve the above problems, the present invention has the following features.

  [1] In hot rolling of steel, the thrust force in the width direction of a backup roll of a finishing mill and / or a roughing mill is measured, and the thrust force is canceled by crossing the backup roll and the work roll. Hot rolling method to do.

  [2] In hot rolling of steel, measure the width direction thrust force of the work roll of the finishing mill and / or the roughing mill, cross the backup roll and the work roll, and the absolute value of the thrust force of the upper and lower work rolls The hot rolling method characterized by equalizing.

  [3] The hot rolling method according to [1] or [2], wherein a strain gauge is attached to a stress concentration portion of the chock and the thrust force in the width direction is measured.

  [4] The hot rolling method according to [1] or [2], wherein the thrust force in the width direction is measured from the shift cylinder pressure.

  [5] Using the measured thrust force in the width direction, the skew angle θ ′ is obtained from the following equations (1) and (2), and the backup roll and the work roll are crossed so that the skew angle θ ′ becomes zero. The hot rolling method according to any one of [1] to [4], wherein

  In the present invention, when the steel is hot-rolled, it is possible to appropriately cancel the thrust force in the width direction generated in the rolling roll.

It is a figure which shows the thrust force measuring method (strain gauge) of the rolling roll in one Embodiment of this invention. It is a figure which shows the thrust force measuring method (cylinder pressure) of the rolling roll in one Embodiment of this invention. It is a figure which shows the thrust force which acts on a roll in a pair cross mill. It is a figure which shows the cross angle of the upper and lower work rolls in a pair cross mill. It is a figure which shows the correction method of the skew angle in one Embodiment of this invention. It is a figure which shows the measurement result in the Example of this invention. It is a figure which shows the measurement result in the Example of this invention.

  One embodiment of the present invention will be described.

  First, the basic concept in one embodiment of the present invention will be described.

  In general rolling mills, recombination is performed by moving the backup roll and work roll in the width direction in the width direction of the rolling material. Therefore, a load cell is installed in the housing and the thrust force in the width direction (hereinafter simply referred to as “thrust force”). ) Is difficult to measure.

  Therefore, in one embodiment of the present invention, a strain gauge is attached to the chock of a rolling roll (backup roll or work roll) of a finish rolling mill and / or a rough rolling mill, or a shift cylinder in the case of a shift mill. Thrust force can be measured by measuring pressure.

  At that time, generally, in the cross mill, the thrust force acting on the work roll is small at a cross angle of about 1 degree. In particular, in the pair cross mill, the work roll and the backup roll are substantially parallel, and the thrust force acting on the backup roll is small. Is ideally 0, and since it is necessary to measure a slight thrust force, it is preferable to attach a strain gauge to the stress concentration portion.

  In this embodiment, the thrust force measurement value of the work roll or backup roll is used to calculate the parallel displacement amount and direction of both axes, and the position adjustment shim of the chock positioning device is increased or decreased to The thrust force is countered by crossing to.

  Thus, the thrust force acting on the roll can be canceled out, which is effective for equipment maintenance. Since there are cases where the thrust bearing of the backup roll is burned out at about 1/4 of the normal load, the smaller the thrust force of the backup roll is, the better, in order to continue stable rolling.

  In addition, the absolute value of the thrust force of the upper and lower work rolls can be made equal, and the sum of the forces in the width direction exerted on the rolled material from both work rolls can be reduced to 0. preferable.

  Also, by comparing the thrust force of the upper and lower work rolls, the deviation of the intersection of the upper and lower work roll axes, that is, the cross point from the geometrically normal position is calculated, and based on this, the upper or lower backup roll is crossed appropriately. By doing so, there is also an effect of making the absolute values equal and reducing the meandering of the rolled material.

  In addition, by using the measured thrust force value of the work roll or backup roll, the amount of parallel displacement of both axes is calculated and the amount of wear is reduced by canceling the thrust force by crossing the two appropriately. Since the replacement cycle can be extended, the operating rate of the rolling mill can be increased.

  Moreover, the axial line of a work roll and a backup roll can be made parallel from a thrust force measurement value, a leveling error can be reduced, and meandering of the rolled material can be prevented, which is preferable in operation.

  Next, details of one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a state in which a thrust force is measured using a strain gauge for a pair cross mill rolling roll (work roll, backup roll) in an embodiment of the present invention. Here, FIG. 1A is a perspective view, and FIG. 1B is a top view. Rolling roller 1 is restrained by chocks 2, when the chocks 2 fixed not to move in the width direction in the housing, cause bending by the thrust force F ₁ to the chock 2, strain gauges 3, strain gauges measuring cable 4, strain measuring device 5 To measure the strain. Thrust force F ₁ is determined by the stress calculated using the measured distortion.

FIG. 2 shows a state in which the thrust force is measured using the back pressure of the shift cylinder with respect to the rolling roll (work roll, backup roll) of the shift mill in one embodiment of the present invention. When the thrust force F ₂ acts on the rolling roll 6, a back pressure is generated in the shift cylinder 7, and the thrust force F ₂ can be obtained using the back pressure.

FIG. 3 shows a thrust force acting on a rolling roll in a pair cross mill. Since the rolled material 8, the upper work roll 9 and the lower work roll 10 have a cross angle θ and a speed direction difference as shown in FIG. 4, the thrust forces F ₃ and F ₄ have the same magnitude and act in opposite directions to each other. To do. In addition, as shown in FIG. 5, if the work roll and the backup roll are misaligned, if the skew angle (cross angle between the work roll and the backup roll) forms θ ′, there is a difference in the speed direction, resulting in a thrust. Forces F ₅ and F ₆ are generated. If there is a shift in the cross point of the roll, a load difference occurs in the width direction, and F ₁₁ and F ₁₂ have different values.

  FIG. 5 shows a correction method of the skew angle θ ′ using the measurement result of the thrust force. A thrust force is generated in the backup roll by the skew angle θ ′, and deformation of the chock is measured by a strain gauge and converted into a thrust force. Further, the skew angle θ ′ is obtained by the following equations (1) and (2). The position adjustment shim 14 of the chock positioning device 13 in contact with the chock is increased or decreased so that the skew angle θ ′ is reduced. Then, the deviation between the thrust force of the backup roll and the cross point becomes small. Accordingly, the thrust force and the differential load are reduced, which is preferable for equipment maintenance, and the asymmetry during rolling is small, which is preferable for operation.

FIG. 4 shows the cross points of the upper and lower work rolls. The cross point 15 is an intersection of the axes of the upper work roll and the lower work roll, and has an effect of preventing meandering by increasing / decreasing the position adjustment shim 17 of the chock positioning device 16 so as to pass through the center in the width direction of the rolled material. The cross point position may be determined such that the thrust force measurement values F ₃ and F ₄ are equal. If the thrust force measurement values F ₃ and F ₄ (forces in opposite directions) are set to be small (the absolute value of the thrust force is set to be equal), the thrust force acting on the rolling material is reduced. The force to meander the rolled material is reduced, which is preferable in operation.

  As an example of the present invention, a hot rolled steel sheet having a thickness of 3.1 mm and a width of 900 mm is targeted for a pair cross mill of a work roll (diameter φ575 mm × body length 2030 mm) and a backup roll (diameter φ1630 mm × body length 2030 mm). After rolling, the thrust force acting on the rolling roll (work roll, backup roll) was investigated.

  At that time, based on the above-described embodiment of the present invention, the case where the work roll and the backup roll are appropriately crossed is defined as the present invention example, and the conventional case is defined as the conventional example.

  The results are shown in FIGS. FIG. 6 is a comparison of the thrust coefficient (thrust force / rolling load) of the lower backup roll between the conventional example and the example of the present invention. As an example of the present invention, a strain gauge is attached to the thrust force of the back-up roll. Measured and rolled by adjusting the cross angle between the backup roll and the work roll so that the thrust force of the backup roll becomes almost zero. FIG. 7 shows the thrust coefficient (thrust force / rolling load) of the lower work roll. As an example of the present invention, the roll force of the work roll was measured from the back pressure of the shift cylinder, and rolled while adjusting the cross angle between the backup roll and the work roll so that the absolute values of the thrust forces of the upper and lower work rolls were equalized. This is a comparison with a conventional example in which the cross angle is not adjusted.

  As shown in FIG. 6, in the example of the present invention, the thrust coefficient of the backup roll is close to 0 (that is, the absolute value of the thrust coefficient is smaller) than in the conventional example, and the thrust force of the backup roll is reduced. A reduction effect is shown. Further, as shown in FIG. 7, in the example of the present invention, the difference in thrust coefficient between the upper and lower work rolls is close to 0 as compared with the conventional example, and the thrust force of the upper and lower work rolls is almost equal, Roll rolling is not likely to occur due to meandering or differential load, and stable rolling can be achieved.

DESCRIPTION OF SYMBOLS 1 Roll roll 2 Chock 3 Strain gauge 4 Strain gauge measurement cable 5 Strain measurement device 6 Roll roll 7 Shift cylinder 8 Rolled material 9 Upper work roll 10 Lower work roll 11 Upper backup roll 12 Lower backup roll 13 Backup roll chock positioning device 14 Position adjustment Shim 15 Cross point 16 Work roll chock positioning device 17 Position adjustment shim

Claims (4)

In the hot rolling of steel, the width direction thrust force of the backup roll of the finish rolling mill and / or the rough rolling mill is measured, the backup roll and the work roll are crossed to cancel the thrust force, and the measured width direction thrust is measured. Using the force, the skew angle θ ′ is obtained from the following formulas (1) and (2), and the hot roll is characterized in that the backup roll and the work roll are crossed so that the skew angle θ ′ becomes zero. Method.

In hot rolling of steel, measure the width direction thrust force of the work roll of the finish mill and / or rough mill, and make the absolute value of the thrust force of the upper and lower work rolls equal by crossing the backup roll and work roll. In addition, the skew angle θ ′ is obtained from the following formulas (1) and (2) using the measured thrust force in the width direction, and the backup roll and the work roll are crossed so that the skew angle θ ′ becomes zero. A hot rolling method characterized by the above.

  The hot rolling method according to claim 1 or 2, wherein a strain gauge is attached to a stress concentration portion of the chock to measure a width direction thrust force.   The hot rolling method according to claim 1 or 2, wherein the width direction thrust force is measured from a shift cylinder pressure.

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