JP4715352B2 - Metal plate rolling method - Google Patents

Description

  The present invention relates to a method for rolling a metal plate, and more particularly to a method for rolling a metal plate in which a work roll is shifted in the axial direction.

  In rolling a metal plate, a portion of the roll corresponding to a plate path (a portion where the metal plate and the roll are in contact) is worn due to contact between the metal plate as a material to be rolled and a work roll (hereinafter also referred to as a roll). Go. In particular, in hot rolling, since the high-temperature material to be rolled comes into contact with the roll, the temperature of the portion of the roll corresponding to the plate path rises and thermally expands. Therefore, as the number of rolled sheets increases, the axial profile of the roll changes.

  And the local wear and thermal expansion of this roll become disturbance factors, the width direction thickness distribution (also called plate crown) and shape of the material to be rolled are deteriorated, the product quality is lowered and the rolling stability is hindered. Invite. In addition, since the frequency of replacing the rolls is increased, the roll basic unit may be deteriorated.

  Therefore, a work roll shift method has been put to practical use in which a work roll for rolling is rolled by shifting in the width direction by several mm for each rolled material.

As a conventional work roll shift method, for example, as described in Patent Document 1 and Patent Document 2, a cyclic shift for periodically shifting the work roll has been used.
Japanese Patent Laid-Open No. 06-154823 JP-A-11-254015

  By the way, in cyclic shift, roll shift is performed for each material to be rolled at a constant pitch while reciprocating between predetermined folding positions. Therefore, it is possible to disperse the thermal expansion and wear of the roll very effectively for a rolling cycle in which continuous rolling of the same width is performed.

  However, in general, the sheet width often changes gradually in the rolling cycle, and in such a case, a sufficient effect cannot be obtained by the conventional cyclic shift. When the plate width is gradually narrowed in the rolling cycle, the shift range is too wide in the latter half of the rolling cycle, and sufficient effects of thermal expansion of the roll and distribution of wear cannot be obtained.

  In addition, depending on the difference in width between a material to be rolled and the material to be rolled next, because of the cyclic shift due to the thermal expansion and wear of the roll in the vicinity of both width ends of the plate path, On the rolled material side, profile anomalies such as edge high spots and edge drops may occur.

  The present invention provides a rolling method capable of effectively dispersing the thermal expansion and wear of a work roll in rolling of all the rolled materials in a rolling cycle.

  The inventors have noticed that there is a problem that the conventional cyclic shift has determined the folding position for reversing the shift movement direction in consideration of only the mechanical restrictions of the shift mechanism of the rolling mill. As a result of intensive studies on the effects of changing the folding position inside, including the addition of conditions for crossing the upper and lower work rolls, it was found that there is an optimum method for determining the shift position.

That is, the present invention provides a rolling method of a metal plate for cyclically shifting the work rolls of the rolling mill in the axial direction, when determining the shift position of the work rolls in accordance with the rolling sequence in a rolling cycle, predetermined shift pitch In addition to changing the cyclic shift position, the distance from the center position in the axial direction of the work roll to the return position that reverses the cyclic shift movement direction when changing the cyclic shift position is determined in the rolling order within the rolling cycle. Accordingly , in determining the turn-back position that reverses the cyclic shift movement direction, the distance from the axial center position of the work roll to the turn-back position at the start of rolling is set to 100 mm or more, and the work roll at the end of the rolling cycle is set to 100 mm or more. The distance from the axial center position to the folding position is A rolling method of metal plate, wherein the monotonically decreasing to be less than 50% of the distance to the turn-back position from the axial center position of the work roll at the rolling start.

  According to the present invention, it is possible to effectively disperse the thermal expansion and wear of the work roll and to obtain a good plate crown in the rolling of all the rolled materials in the rolling cycle.

  A method for determining a shift position of a work roll in rolling a metal plate that shifts the work roll of a rolling mill in the axial direction according to the present invention will be described.

  In the present invention, when determining the shift position of the work roll in accordance with the rolling order within the rolling cycle, the shift position is changed at a predetermined shift pitch, and the folding is performed to reverse the shift movement direction from the axial center position of the work roll. The distance to the position is changed according to the rolling order in the rolling cycle, and this will be specifically described with reference to FIG. 2 and other drawings.

  First, the concept of shift will be described with reference to FIG. FIG. 2 is a front view schematically showing the work roll and the material to be rolled during rolling. In FIG. 2, 101A represents an upper work roll, 101B represents a lower work roll, and 102 represents a material to be rolled. 103 is a center line indicating the center position in the left-right direction of the rolling mill, 104A is the left-right direction of the upper work roll 101A, that is, the center position in the axial direction, and 104B is the left-right direction of the lower work roll 101B, that is, the center position in the axial direction. . Here, taking the upper work roll as an example, the shift position of the work roll is defined by the distance between the center position 103 in the left-right direction of the rolling mill and the center position 104A in the left-right direction of the upper work roll. Cyclic shift is a rolling method in which a shift position is changed at a certain pitch every time a material to be rolled is rolled, and a series of operations for reversing the shift movement direction when the turn-back position is reached is repeated. Here, the upper and lower work rolls are shifted in opposite directions so as to be point-symmetric when viewed from the front view as shown in FIG.

  In FIG. 1, the horizontal axis indicates the rolling order, and the vertical axis indicates the shift position. Also, the black circle symbol ● in the figure indicates the locus of the shift position.

  The initial shift position is 0, and the shift pitch is Δy. The folding position is M, and the value of M can be changed in the rolling cycle. The folding position at the start of rolling is M (0), and the folding position at the i-th rolling order is M (i). . If the final roll of the rolling cycle is nth, the folding position at this time is M (n). In this example, the first shift direction is assumed to be a positive direction. Here, Δy> 0, and in the example of FIG. 2, the positive direction is the direction from the left to the right in FIG. 2 for the upper work roll.

  Note that the rolling cycle refers to starting rolling after incorporating a freshly ground work roll into a rolling mill, rolling some (50 to 100 inside / outside) material to be rolled, and then another polishing. A group of materials to be rolled from when all work rolls are incorporated into a rolling mill to when rolling is started is referred to as one constituent unit.

In other words, in this embodiment, after the rolling is started, the direction is shifted in the positive direction until the first turn-up position is reached. That is,
When y (i) <M (i) −Δy and y (i) −y (i−1) ≧ 0,
y (i + 1) = y (i) + Δy
It becomes.

Next, when the first turn-back position is reached, the shift direction is reversed (negative direction). That is,
When y (i) ≧ M (i) −Δy and y (i) −y (i−1) ≧ 0,
y (i + 1) = y (i) −Δy
It becomes.

Then, it shifts in the negative direction until it reaches the turn-back position in the negative direction. That is,
When y (i) ≧ −M (i) + Δy and y (i) −y (i−1) <0,
y (i + 1) = y (i) −Δy
It becomes.

Further, when the turn-back position in the negative direction is reached, the shift direction is reversed again, and the shift is again made in the positive direction. That is,
When y (i) <− M (i) + Δy and y (i) −y (i−1) <0,
y (i + 1) = y (i) + Δy
It becomes.

Here, in the above description, the first shift direction is a positive direction for the upper work roll, and y (1) = Δy. At this time, the first roll shift direction of the lower work roll is a negative direction, That is,
y (1) = − Δy.

  Furthermore, in the case of a hot finishing rolling mill in which the subsequent four stands among the seven stands are made of a work roll shift rolling mill, for a rolling cycle composed of 120 low carbon steel plates with a plate width of 1600 mm to 1000 mm, The effect of the folding position on the thickness profile of each rolled material was investigated. The work roll (hereinafter simply referred to as a roll) of the last seventh rolling mill (seventh stand) is 700 mm in diameter, 2000 mm in length, and made of nickel grain cast iron. The sheet crown (measured from the sheet width central position and the sheet thickness deviation at the position 25 mm from the sheet width end) was measured with a sheet thickness profile meter installed on the exit side of the finishing mill. The closer the plate crown is to zero, the smaller the thickness deviation in the width direction and the better the quality. However, minus, that is, the one that is thicker at the 25 mm position from the plate width end than the center position of the plate width is poor. .

  Since the shift pitch is 21 mm and the folding position is changed according to the rolling order in the rolling cycle, M (0) at the start of rolling and M (120) at the end of rolling are determined, and the folding position between them is linear. It was decided to interpolate. Moreover, as an evaluation index, an average value of 120 sheet crowns was used.

  FIG. 3 shows the evaluation of the plate crown with respect to the conditions of M (0) and M (120). However, in the figure, when the plate crown is 80 μm or more, or minus (thickness at the 25 mm position from the plate width end) is x (defect), the plate crown is 60 μm or more and less than 80 μm is △ (somewhat bad), the plate A crown of 40 μm or more and less than 60 μm was evaluated as ◯ (good), and a plate crown of 0 μm or more and less than 40 μm was evaluated as ◎ (very good).

  From FIG. 3, when M (0) and M (120) are 0 mm, that is, when the shift is not performed at all, the plate crown is x (defective). This is presumably because the roll wear and thermal expansion are concentrated in the passing portion of the material to be rolled, and the roll profile changes greatly during the rolling cycle.

  Further, when M (0) and M (120) of the conditions corresponding to those on 301 in FIG. 3 are equal, that is, when the turning position of the shift does not change during the rolling cycle, Δ (somewhat poor). Met. On the other hand, when M (0) and M (120) are not equal, that is, when the folding position is changed according to the rolling order in the rolling cycle, a plate crown of ◯ (good) or higher is obtained. It has been. This is presumed to be because a larger roll wear and thermal expansion dispersion effect was obtained than when the turn-back position did not change. In particular, M (0) is larger than 100 mm (range on the right side from 302 in the figure), and the distance from the axial center position of the roll to the turn-back position at the end of the rolling cycle is the axial center position of the roll at the start of rolling. In the range below 303, which is 50% or less of the distance from the folding position to the folding position, a ク ラ ウ ン (very good) plate crown is obtained, which is the most preferred embodiment of the present invention.

  Here, the upper limit of the folding position M does not have an upper limit from the plane of the plate crown, but from the viewpoint of equipment, when M increases, it is necessary to increase the roll length of the roll, Due to problems such as the need for equipment, it is desirable that the thickness be 300 mm or less.

  In addition, the sheet crown of the material to be rolled is controlled by utilizing the phenomenon that the gap between the upper and lower rolls expands in a parabolic shape from the center in the width direction of the material to be rolled, which occurs when the upper and lower rolls cross each other. By combining a roll cloth which is a means for carrying out, it is possible to obtain a more excellent plate crown. FIG. 4 shows the evaluation of the plate crown when roll cloth is performed under the same rolling conditions as in FIG. FIG. 4 shows that the range in which a very good plate crown can be obtained is widened. This is presumably because even when the roll shift alone cannot provide a very good plate crown, it is possible to further improve the plate crown by appropriately crossing the upper and lower rolls.

  Here, when the same investigation as described above was performed under conditions other than 21 mm, for example, 5 mm, 11 mm, 29 mm, and 37 mm, the same result was obtained.

  An actual machine simulation was performed on a rolling cycle having a sheet width configuration shown below to verify the present invention. The hot rolling mill is a four-stage finish rolling mill in which the last four of the seven stands are work roll shift rolling mills. The final seventh rolling mill has a 700 mm diameter and 2000 mm cylinder length nickel grain cast iron roll. It was. The shift stroke of the work roll shift rolling mill from the fourth stand to the seventh stand is ± 300 mm. Further, it is assumed that a mechanism for crossing the upper and lower rolls is also provided from the fourth stand to the seventh stand.

  The width structure of the rolling cycle in this example is as follows.

(Cycle A)
As shown in FIG. 5, 120 steel plates with a width of 1200 mm are continuously rolled. That is, there is no width change.

(Cycle B)
As shown in FIG. 6, rolling is started from a steel plate having a width of 1200 mm, the width is increased until the first 21 pieces have a width of 1600 mm, 79 pieces thereafter are reduced by 10 mm, and finally the 810 mm plate is rolled. .

  In each of the above cycles, the length of the steel plate was a constant value of 1000 m. The finishing thickness is 2 mm to 2.5 mm.

  For the above cycles A and B, comparison and evaluation between the conventional example and the present invention example were performed. The results are shown in Table 1 and FIGS.

  FIGS. 7-14 has shown the shift position of the upper work roll of the 7th stand in the invention examples 1-8, and made the positive direction the drive side. Here, the lower work roll is point-symmetric with the upper work roll, that is, starts to shift in the negative direction after rolling starts. The fifth stand is shifted in the same direction as the seventh stand, the fourth stand and the sixth stand are opposite to the seventh stand, that is, the upper work roll is in the negative direction, and the lower work roll is in the negative direction. Decided to start shifting in the positive direction. In other words, the adjacent stands are shifted in a so-called zigzag pattern both vertically and vertically.

  15-17 has shown the shift position of the upper work roll of the 7th stand in the comparative examples 3, 5, and 6. FIG. The definition of the shift direction is the same as that of the above-described invention example.

  As evaluation, it evaluated by the average value of the board crown in the 7th stand exit side. Here, the plate crown is obtained by averaging the deviation of the plate thickness at the plate width center position and the plate width end at a position 25 mm from the plate width end, and when the sign is negative, that is, minus, from the plate width end compared to the plate width center position. It shows that the plate thickness at the 25 mm position is thick. When the plate crown is 80 μm or more or minus (the plate thickness at the 25 mm position from the plate width end is thick), the plate crown is 60 μm or more and less than 80 μm, and the plate crown is 40 μm or more and less than 60 μm. Excellent, the plate crown was 0 μm or more and less than 40 μm was considered very good.

  Invention Example 1 is a shift (FIG. 7) in which the distance from the center position in the axial direction of the roll to the turn-back position is reduced according to the rolling order in the rolling cycle, and a good plate crown is obtained.

  Hereinafter, when the distance from the axial center position of the roll to the turn-back position is simply referred to as the distance to the turn-back position, Invention Example 2 indicates that the distance to the turn-up position at the start of rolling is 100 mm or more. And a monotonously reduced shift (FIG. 8) so that the distance to the folding position at the end of the rolling cycle is 50% or less of the distance to the folding position at the start of rolling. Has been obtained.

  Invention Example 3 is a shift (FIG. 9) in which the distance to the turn-back position is reduced according to the rolling order within the rolling cycle, and is a case where a cloth is used in combination, and a very good plate crown is obtained. Yes.

  Inventive Example 4, as in Inventive Example 2, the distance to the folding position at the start of rolling is 100 mm or more, and the distance to the folding position at the end of the rolling cycle is 50% of the distance to the folding position at the start of rolling. The shift is monotonously reduced so as to be as follows (FIG. 10), and a very good plate crown is obtained.

  Invention Example 5 is a shift (FIG. 11) in which the distance to the turn-back position is changed according to the rolling order within the rolling cycle, and a good plate crown is obtained.

  Inventive Example 6, like Inventive Example 2, the distance to the folding position at the start of rolling is 100 mm or more, and the distance to the folding position at the end of the rolling cycle is 50% of the distance to the folding position at the start of rolling. The shift is monotonously decreased so as to be as follows (FIG. 12), and a very good plate crown is obtained.

  Invention Example 7 is a shift (FIG. 13) in which the distance to the turn-back position is decreased according to the increase in each rolling order in the rolling cycle, as in Invention Example 3, and is a case where a cross is used in combination. A very good plate crown is obtained.

  Inventive Example 8, similarly to Inventive Example 2, the distance to the folding position at the start of rolling is 100 mm or more, and the distance to the folding position at the end of the rolling cycle is 50% of the distance to the folding position at the start of rolling. The shift is monotonously reduced so as to be as follows (FIG. 14), and a very good plate crown is obtained.

  On the other hand, Comparative Example 1 was a case where no shift was performed, and the plate crown was poor.

  In Comparative Example 2, the shift was not performed and only the cross was performed, and the plate crown was poor.

  In Comparative Example 3, the distance to the turn-back position was kept constant in the rolling cycle (FIG. 15), and the plate crown was somewhat poor.

  In Comparative Example 4, the shift was not performed, and the plate crown became excessive at the 80th rolling, and a roll change was necessary on the way.

  In Comparative Example 5, the distance to the turn-back position was kept constant in the rolling cycle, and crossing was performed (FIG. 16). The plate crown was slightly poor.

  In Comparative Example 6, the distance to the turn-back position was kept constant in the rolling cycle (FIG. 17), and the plate crown was poor.

It is a figure which shows an example of the shift position of the work roll in this invention. It is a figure explaining the concept of the cyclic shift in this invention. It is a figure which shows evaluation of the plate crown with respect to the conditions of M (0) and M (120) in embodiment of this invention. It is a figure which shows evaluation of the plate crown at the time of performing roll cross with respect to the conditions of M (0) and M (120) in embodiment of this invention. It is a figure which shows the board width of the cycle A in the Example of this invention. It is a figure which shows the board width of the cycle B in the Example of this invention. It is a figure which shows the shift position of the example 1 of an invention in the Example of this invention. It is a figure which shows the shift position of the invention example 2 in the Example of this invention. It is a figure which shows the shift position of the example 3 of an invention in the Example of this invention. It is a figure which shows the shift position of the invention example 4 in the Example of this invention. It is a figure which shows the shift position of the invention example 5 in the Example of this invention. It is a figure which shows the shift position of the invention example 6 in the Example of this invention. It is a figure which shows the shift position of the invention example 7 in the Example of this invention. It is a figure which shows the shift position of the invention example 8 in the Example of this invention. It is a figure which shows the shift position of the comparative example 3 in the Example of this invention. It is a figure which shows the shift position of the comparative example 5 in the Example of this invention. It is a figure which shows the shift position of the comparative example 6 in the Example of this invention.

Explanation of symbols

101A Upper work roll 101B Lower work roll 102 Material to be rolled 103 Center line 104A of rolling mill Center position 104B of upper work roll 101A Center position M of lower work roll 101B Folding position

Claims (1)

In the rolling method of a metal plate for cyclically shifting the work rolls of the rolling mill in the axial direction, when determining the shift position of the work rolls in accordance with the rolling sequence in the rolling cycle, the cyclic shift positions in a predetermined shift pitch with change, from the axial center position of the work rolls, the distance to the return positions for reversing the cyclic shift movement direction at the time of changing the cyclic shift position, and change in accordance with the rolling sequence in the rolling cycle, the In determining the turn-back position that reverses the cyclic shift movement direction, the distance from the axial center position of the work roll to the turn-back position at the start of rolling is set to 100 mm or more, and the work roll is turned back from the axial center position at the end of the rolling cycle. The distance to the position is Rolling method of metal plate, characterized in that the monotonically decreasing to be less than 50% of the distance to the turn-back position from the axial center position of the over crawl.

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