JP6123745B2 - Steel sheet rolling method - Google Patents

Description

  The present invention relates to a steel sheet rolling method, and more particularly, to a steel sheet rolling method for controlling warpage of a steel sheet during rolling.

  In many cases, the rolled steel sheet has a defective shape (flatness). These shape defects not only reduce the product value of the steel sheet, such as inhibiting the rationalization of the processing process when using the steel sheet, but also reduce the rolling efficiency and threading performance in the production of the steel sheet, increase the refining process, etc. Greatly impacts productivity and manufacturing costs.

  Among the defective shape of the steel sheet, there is a defective shape called warpage in which the steel sheet curves in the front direction or the reverse direction. The warpage of a steel sheet caused by rolling is often caused by a difference in elongation between the front and back surfaces of the steel sheet during rolling. Warpage that curves to the front direction side (up roll side) during rolling is called up warp, and warpage that curves to the back direction side (lower roll side) is often referred to as downward warp. This is called warping. In addition, as shown in FIG. 1, a warp in the longitudinal direction during rolling is referred to as a longitudinal warp (L warp), and a warp in the width direction is referred to as a width warp (C warp).

  Generally, a rolling mill is provided with a pair of upper and lower work rolls, and may be provided with a backup roll adjacent to the work rolls. A work roll is a roll which contacts a to-be-rolled material at the time of rolling, and adds a load directly. The backup roll is a roll installed adjacent to the work roll in order to suppress the deflection of the work roll. The 2Hi rolling mill has a pair of upper and lower work rolls, and the 4Hi rolling mill has a pair of upper and lower work rolls and a backup roll. Further, in order to further suppress the deflection of the work roll, an intermediate roll may be installed between the work roll and the backup roll. For example, a 6Hi rolling mill has a pair of upper and lower work rolls, an intermediate roll, and a backup roll. It has a total of 6 rolls.

  The rolling mill may be provided with a mechanism (bender) that applies a pressing force to the chock of the roll to give the roll deflection. The force that gives the roll deflection by the vendor is called bending force.

  Conventionally, as a means for correcting warpage of a steel sheet, there is a method of correcting warpage in a process different from rolling by an apparatus different from a rolling mill, that is, a method of correcting warpage using a roller leveler or a tension leveler. Has been done.

  On the other hand, a method of controlling the warpage of a steel sheet by operating some rolling conditions during rolling has also been proposed. For example, Patent Document 1 or Patent Document 2 discloses a method of controlling the warpage of a rolled plate by giving a peripheral speed difference to upper and lower work rolls and driving each work roll. Patent Document 3 discloses a method of controlling the shape of the control cooling steel sheet by adjusting the amount of water injection on the front and back surfaces of the steel sheet in the control cooling device when the hot-corrected steel sheet is cooled. Is disclosed. Furthermore, Patent Document 4 discloses a method of controlling the load from the work roll on the upper and lower surfaces and controlling the warpage of the metal plate by individually controlling the bending force acting on the roll chock.

JP 2010-240654 A WO2009 / 057820 Japanese Patent Laid-Open No. 10-5868 JP 2013-66934 A

  However, in the conventional method of correcting the warpage of the rolled sheet in a process different from rolling by an apparatus such as a roller leveler or a tension leveler, there is a problem that productivity is reduced such as extension of lead time and manufacturing cost is increased.

  Further, the warpage control method of the rolled sheet proposed in the above-mentioned Patent Documents 1, 2, and 4 is intended for the L warpage shown in FIG. 1 and is not a method for controlling the C warpage during rolling.

  The objective of this invention is providing the rolling method of the steel plate which does not require apparatuses and processes other than a rolling mill, and controls C curvature of a steel plate with a rolling mill during rolling.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors applied a vertically asymmetric bending force to the upper work roll and the lower work roll during rolling, and made the upper work roll and the lower work roll asymmetric in the vertical direction. The present inventors have found that the C warpage of a steel sheet can be controlled during rolling by bending, and the present invention has been completed.

That is, this invention consists of the following summaries.
(1) rolling with upper work roll and a mechanism for applying the ink-bending force between the lower work rolls, and a mechanism for applying a de crease bending force to at least one of the upper work roll or the lower work roll A rolling method of a steel sheet using a machine, wherein bending forces having different sizes are applied to the upper work roll and the lower work roll, respectively.
(2) The rolling of the steel sheet according to (1), wherein each bending force applied to the upper work roll and the lower work roll is set corresponding to a warp in the width direction of the steel sheet before rolling. Method.
(3) The bending force applied to the left and right ends of each of the upper work roll and the lower work roll is set separately on the left and right sides corresponding to the width direction distribution of warpage of the steel sheet before rolling. (1) The rolling method of the steel plate as described in (2).

  According to the present invention, it is possible to manufacture a steel sheet that does not require any equipment and processes other than a rolling mill, does not generate C warpage, or has extremely slight C warpage.

  Further, since the steel sheet after rolling does not have a large C warp, the operation in the subsequent process is stabilized, and the product quality and productivity are greatly improved.

It is a schematic diagram which shows the curvature which generate | occur | produces in a steel plate. Is a diagram showing the relationship between Di crease bending force and the curvature variation of C warp. Is a schematic diagram illustrating the positive and negative de-crease bending force. It is a schematic diagram which shows the method of calculating | requiring the curvature amount of a steel plate, and the curvature of curvature. It is a schematic diagram which shows the roll structure of the rolling mill used for the Example of this invention.

  The rolling according to the present invention is carried out cold, and the steel type of the material to be rolled (steel plate) is not limited. In addition, the rolling method according to the present invention can obtain the effect of reducing C warpage regardless of the thickness and width of the steel sheet, but more effectively, rolling of steel sheets having a thickness of 3 mm or less and a width of 2500 mm or less. And rolling with a 2Hi, 4Hi, or 6Hi rolling mill.

The rolling mill used in the present invention is a rolling mill provided with a bender which is a mechanism for applying bending force to a work roll chock to impart deflection to the work roll. The vendor applies a bending force between the upper work roll chock and the lower work roll chock and between the backup roll chock and the housing and the work roll chock in a direction to repel each other by a hydraulic device. Often takes a structure. A vendor that applies a force in a repulsive direction between the upper work roll chock and the lower work roll chock is referred to as an incremental vendor, and the force applied by the incremental vendor is referred to as an incremental bending force. Further, means a vendor to apply a force in the direction to repel each other during such chocks and the housing of the backup roll and the work roll chocks and di crease vendor, the force which the de-crease vendor added that di crease bending force . For de crease vendors, the rolling mill of 2Hi so apply a repulsive force between the housing and the work roll chock, the repulsive force between the chocks of the chocks and the work roll of the backup roll in the rolling mill of 4Hi Make a call. In the 6Hi rolling mill, a repulsive force is applied between the chock of the intermediate roll and the chock of the work roll, or between the chock of the backup roll and the chock of the intermediate roll.

In the embodiment of the present invention, in order to control the C warpage of the steel sheet, by applying different bending forces to the upper work roll and the lower work roll, respectively, the upper work roll and the lower work roll are given an asymmetrical vertical deflection, The roll gap through which the material to be rolled passes is made asymmetric in the vertical direction. Therefore, the rolling mill according to the present invention, the upper work roll of the de crease vendors add bending force from above chocks or, lower work roll of the de crease vendors applying bending force from below chock, of at least one It is necessary to have a function of applying separate bending forces to the upper work roll and the lower work roll. For example, if the rolling mill 4HI, adding repulsive force between the bottom of chock chock of the upper and the upper backup roll of the upper work roll di crease vendor or, chocks of the lower work roll lower and lower backup rolls, comprising applying a repulsive force de crease vendor, at least one of the between the upper chock of. As an example with respect 2Hi rolling mill, di crease vendor adding repulsive force between the upper and the housing of the chocks of the upper work roll, or a repulsive force between the lower and the housing of the chocks of the lower work roll comprising di crease vendors, at least one one added. In the present invention, at least either the upper work roll and lower work rolls as described above, if it has a de crease vendors adding de crease bending force of the roll arrangement (2Hi, 4Hi, 6Hi) is any Absent. Moreover, the de-crease vendor corresponds to C warping of a wide variety of steel sheet, in order to correct the C warpage of the steel plate to warp of sufficiently small curvature, to adjust the de-crease bending force applied to the rolls It is necessary to have a function.

Furthermore, the rolling mill used in the present invention, in order to prevent increase of the elongation of the steel sheet edge portions by di crease bending force exerted from the de crease vendors, and it the shape of the originating steel defective ink lease between the upper and lower work rolls It is necessary to have an increase vendor that adds bending power.

  Moreover, in embodiment of this invention, it is preferable to set the bending force added to an upper work roll and a lower work roll corresponding to the width direction curvature (C curvature) of the steel plate before rolling. For this purpose, the bending conditions and rolling applied to the upper and lower work rolls under the rolling conditions to be implemented (steel grade, thickness, width, rolling mill, rolling load, elongation rate, entry side tension and exit side tension) It is necessary to grasp the relationship between the amount of change in the curvature of the C warp of the steel sheet (the amount of change in the curvature of the C warp). When the relationship between the bending force applied to the upper and lower work rolls and the amount of curvature change of the C warp is unknown, or measured during rolling, for example, as shown in FIG. If it is difficult to obtain, a preliminary experiment for measuring the bending force and the curvature change amount of the C warp due to rolling is performed in advance according to the rolling conditions to be performed as necessary. FIG. 2 shows an example of the relationship between the bending force applied to the upper and lower work rolls obtained through a preliminary experiment and the amount of change in curvature of the C warp due to rolling. In FIG. 2, the bending force is a force applied from the vendor to one end of the roll, and is, for example, the force 4 or 5 in FIG. 3A or the force 5 or 6 in FIG. From FIG. 2, the relationship between the bending force and the curvature change amount of the C warp due to rolling can be approximated by the following formula [1].

Record
_{κ ν = A × P + B} [1]
_{κ ν = 1 / R 0 -1} / R i
Where κ _{ν is the} amount of change in the curvature of the C-warp of the steel sheet due to rolling.
(The upward direction is positive) [1 / m]
A: The amount of change in curvature of the C warpage of the steel sheet due to rolling
Coefficient representing the relationship with bending force
[1 / (m × kN)]
B: When bending force is vertically symmetric
Change in curvature of C-warp of steel sheet due to rolling
(The upward direction is positive) [1 / m]
P: Bending power [kN]
R ₀ : Curvature radius of curvature of steel sheet after rolling [m]
R _i : Curvature radius of C warp of steel plate before rolling [m]
In the preliminary experiment, the bending force was set so as to be in any of the following conditions (I) or (II).

(I) above di crease bending force and the ink lease state bending force are equal.

(II) state under de crease bending force and-bending force are equal.
As shown in FIG. 3, the bending force when the vendor is applied as in (I) above is negative, and the bending force when the vendor is applied as in (II) is positive.

However, not necessarily set equal to Di crease bending force acting on the upper work roll or the lower work roll-bending force is adjusted so as to reduce the shape defect such as elongation excessive steel edges.

  By using the relational expression [1] between the bending force obtained as described above and the curvature change amount of the C-warp of the steel sheet due to rolling, the bending force necessary for correcting the C-warp of the steel sheet before rolling is applied. C warpage can be reduced. For example, when the relationship between the bending force and the amount of change in the curvature of the C warp of the steel sheet due to rolling is obtained as in the above equation [1], the bending force required to make the C warp of the steel sheet before rolling zero. It calculates | requires by following formula [2].

Record
P = − (κ _i + B) / A [2]
Here, κ _i : curvature of C warp of steel plate before rolling (the upward warping direction is positive) [1 / m]
Incidentally, the curvature kappa _c of C warp of the steel sheet, taken Setsuban enough length 500mm from the steel plate, as shown in FIG. 4, the deflection amount of warpage when hung The sections plate [delta] _c and chord It is determined by the following equation by measuring the length L _c.

κ _c = 8 × δ _c / L _c ²
Further, when the curvature of the C warp of the steel sheet before rolling is not uniform in the width direction, the bending force applied to the left and right ends of each of the upper work roll and the lower work roll is distributed in the width direction of the C warp of the steel sheet before rolling. It is preferable to set the left and right separately correspondingly. For example, if the curvature of the C warp of the steel sheet before rolling differs between the left side and the right side of the sheet width direction center in the rolling direction, if the rolling mill is equipped with a bender on each of the left and right ends of the upper and lower work rolls, rolling The bending force obtained by the equation [2] may be applied separately to the left and right vendors in the direction corresponding to the curvature of the left and right sides of the steel sheet. In addition, if this method is used, even when the configuration of the rolling mill vendor is asymmetrical (such as when the vendor is provided only on one side of the work roll), the range in which the warpage can be changed is limited, but the present invention is applied. It is possible to control the warpage.

Table 1 shows the specifications of the rolling mill used in this example. Under the the rolling machine, as shown in FIG. 5, adding an ink lease vendors adding-bending force 5, the de-crease vendor and lower di crease bending force 6 on addition of above de crease bending force 4 and di crease vendors are respectively provided at both ends of the work roll.

  First, each bending to be applied to upper and lower work rolls using a SPTE 5.6 / 2.8D (JIS G 3303 standard) steel plate having a known thickness 0.18 mm and a width of 320 mm as a material to be rolled, with a curvature of C warp before rolling. The force was changed as shown in Table 2, and the rolling load was set to 312.5 (kN / m), the elongation was set to 3.0%, the incoming tension was 98 (MPa), and the outgoing tension was 98 (MPa). Then, a rolling experiment was carried out, and the amount of change in curvature of the C warp due to rolling was determined. The result is shown in FIG. From FIG. 2, the relationship between the bending force and the curvature change amount of the C warp can be approximated by the following equation [3].

_{κ ν = 0.019 × P + 0.06} [3]
Accordingly, the plate thickness 0.18mm curvature is kappa ₁ of C warp before rolling, the C warpage of SPTE 5.6 / 2.8D steel plate width 320 mm, the elongation rate using the present rolling mill 3.0% The bending force required for correction by rolling set to ## EQU3 ## is obtained by the following equation [4].

P = − (κ _i +0.06) /0.019 [4]
Therefore, an SPTE 5.6 / 2.8D steel plate having a plate thickness of 0.18 mm and a plate width of 320 mm with different curvatures of C warp before rolling, rolling load: 312.5 (kN / m), elongation: 3.0 %, Entry side tension: 98 (MPa), exit side tension: 98 (MPa), rolling under the bending conditions of the method of the present invention obtained from the formula [4] and the bending conditions set by the conventional method, rolling The curvature of C warpage of the later steel plate was measured. The results are shown in Table 3. When the determination was made on the condition that the curvature of the C warp of the steel sheet after rolling was ± 0.1 (1 / m) or less, all the cases were satisfied in the case according to the method of the present invention. None of them do not satisfy the conditions, and the effects of the present invention are remarkably exhibited.

1 rolled steel plate 2 upper work roll 3 lower work rolls 4 above di crease bending force 5-bending force 6 under de crease bending force 7 upper backup roll 8 lower backup roll

Claims (3)

Steel sheet by the upper work roll and a mechanism for applying the ink-bending force between the lower work roll, rolling mill and a mechanism for applying a de crease bending force to at least one of the upper work roll or the lower work roll of a rolling method, a rolling method of steel plate characterized by adding bending force of the upper work roll and different sizes in the lower work roll.   The steel sheet rolling method according to claim 1, wherein each bending force applied to the upper work roll and the lower work roll is set corresponding to a warp in a width direction of the steel sheet before rolling.   2. The bending force applied to both left and right ends of each of the upper work roll and the lower work roll is set separately on the left and right sides corresponding to the width direction distribution of warpage of the steel sheet before rolling. Or the rolling method of the steel plate of 2.

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