JP2726576B2 - Cold rolled steel sheet rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a rolled plate (hereinafter referred to as "rolled plate") when cold rolling a plate by crossing upper and lower work rolls in a plane parallel to the plate.
The present invention relates to a method for rolling a cold-rolled steel sheet to prevent twisting of the steel sheet.

[0002]

2. Description of the Related Art In recent years, the demands of customers on the accuracy of the shape and thickness of a rolled sheet have become increasingly severe. Therefore,
In order to control the crown of the rolled plate, the upper and lower work rolls are independently crossed in a plane parallel to the plate, and the plate is rolled (this is referred to as "work roll cross rolling"), or a backup roll is used. A method of rolling the plate material (this is referred to as “pair cross rolling”) is adopted in which the pair intersects in a plane parallel to the plate material. These roll cloth rolling methods have already been put into practical use especially in hot rolling because of their excellent controllability, but when applied to cold rolling where high dimensions and shape accuracy are required, the rolled sheet twists. Therefore, countermeasures are required.

The reason why the rolled sheet is twisted when roll cross rolling is performed will be described with reference to FIG. (A) of FIG.
Each of the upper work roll 1 and the lower work roll 2 is
When the plate material 3 is rolled while intersecting in a plane parallel to
FIG. 3 is a three-dimensional view for explaining that the torsion occurs. Due to the geometrical arrangement of the work rolls 1, 2, the end A of the rolling plate 4 is pushed down during rolling and the end B on the opposite side is pushed up, so that the rolling plate 4 is twisted. FIG. 1B is a three-dimensional view illustrating that the rolled plate 4 is twisted when roll-cross rolling is performed in the same manner. As shown in FIG. 1 (a), since the rotation axes of the work rolls 1 and 2 are not perpendicular to the rolling direction X of the sheet material 3, the shear force F in the sheet width direction is applied to the upper surface of the rolled sheet 4. ₁ occurs, and a shearing force in the width direction
F ₂ is generated, resulting rolled plate 4 is twisted. Although the directions of these two torsions are opposite to each other, it is considered that under normal rolling conditions, the torsion due to shearing force is large, so that the combined torsion does not become zero, and as a result, the torsion remains in the rolled plate 4. Have been.

[0004] In hot rolling, recrystallization occurs immediately after rolling even if a shearing force that generates torsion acts on the rolled sheet. Therefore, tension is applied except for the top and bottom of the rolled sheet, and apparently the rolled sheet is rolled. Is flattened, the residual stress causing twisting is eliminated, so that the twisting of the rolled plate does not substantially matter.

[0005] In the cold rolling, since a stress relieving effect due to recrystallization immediately after the rolling cannot be expected at all, the rolled sheet is twisted. In particular, when a rolled plate is shipped by as-roll, if there is a twist in the rolled plate, there is a great problem in quality. In addition, a rolled material having a twist may deteriorate the sheet passing property in a process line such as a continuous annealing furnace, and may be a trouble factor in operation.

JP-B-59-41804 discloses a rolling line in which roll cross rolling mills are arranged in tandem, in which the direction of intersection of upper and lower work rolls is reversed in the order of the rolling mills. JP-A-59-144503 discloses a group of rolling mills in which one of a pair of work rolls is arranged at right angles to a rolling direction, and the other work roll is inclined in a plane parallel to the work roll. , In which the arrangement of the work rolls of each rolling mill is reversed in the order of the rolling mills. However, even if cold rolling is performed on these rolling lines, the direction of twist of the rolled plate is only reversed for each rolling stand, and the rolled plate still has twist after the final pass. Therefore, it cannot be an essential solution to the twist of the rolled plate.

[0007]

The roll cloth rolling for controlling the sheet crown has a problem that the above-mentioned rolled sheet is twisted. On the other hand, the dimensions of the rolled plate,
Consumer demands for shape accuracy are becoming more stringent. JP-B-59-41804 and JP-A-59-144503
In the rolling method disclosed in Japanese Patent Application Laid-Open Publication No. H10-260, twist still exists in the rolled plate after the final pass.

An object of the present invention is to prevent the twist of a rolled plate by a relatively simple method when performing cold rolling by a roll cross rolling method.

[0009]

SUMMARY OF THE INVENTION The present invention has the following features when rolling is performed by a roll cross rolling method.

[0010] In the case of a tandem rolling mill, at least at a final stand, a cold rolling steel sheet is rolled by a parallel rolling method.

[0011] In the case of a reversing mill, at least in the final pass, a cold rolling steel sheet is rolled by a parallel rolling method.

In a tandem rolling mill or a reversing rolling mill to which the method of the present invention is applied, the roll arrangement thereof is 2
Not only a double type but also a triple type, a quadruple type, a five-type type, a six-type type and a multiple type such as a Zenjimiya mill may be used. Be eligible.

[0013]

FIG. 2 is a diagram for explaining a method for measuring the twist of a rolled plate. The twist ratio ξ of the rolled plate is determined by the following method. First, a test piece 5 is prepared by cutting a rolled plate into a predetermined size for each pass of each stand. Next, one end of the test piece 5 is fixed by a jig 6 having good flatness by the method shown in FIG. 2, and the twist distance H of the other end of the test piece 5 is measured. Thereafter, the distance H is divided by (L × W) to calculate the torsion ratio の of the rolled sheet. That is, the definition of the torsion rate of a rolled sheet is defined as ξ = H / (L × W)
And The sign of the torsion of the rolled sheet is defined as follows. In FIG. 2, the torsion rate when the left end of the rolled sheet is twisted to the right side of the drawing with respect to the vertical plane parallel to the rolling direction X is positive, and the twisting when the left end is twisted to the left side of the drawing. Make the rate negative. FIG. 2 shows the case where H is positive, that is, ξ is positive.

FIG. 3 shows the torsion ratio of the rolled plate at each stand passage. That is, the work roll diameter is 500mm
In a five-stand tandem rolling mill capable of pair-cross rolling, the intersection angle between the upper and lower work rolls is fixed (0.75 de
g) to reduce the thickness of high-strength steel (TS: 100kgf / mm ² )
The figure shows the torsion ratio of the rolled plate at each stand passage when rolling from 3.2 mm to 1.2 mm. The rolling reduction at each stand was 20%, 20%, 20%, 15% and 15%, respectively.

FIG. 3 shows that the surface roughness R _max of the work rolls of all stands is 5 μm (symbols in the figure: ● and ○) and 1.5.
μm (symbols in the figure: ▲ and △), when all the stands are rolled with the same cross direction of the upper and lower work rolls (symbols in the figure: 印 and ▲) and each stand In each case, the torsion rate of the rolled sheet is shown in the case where the crossing direction of the upper and lower work rolls is alternately reversed (symbols in the figure: 印 and △).

The following can be seen from FIG. First, when the cross direction of the work rolls above and below all the stands is made the same, and the cross angle is fixed, the torsion of the rolled plate monotonically increases for each stand. Next, even if the crossing direction and the crossing angle of the upper and lower work rolls are the same, if the work roll is rolled with a small surface roughness, the torsion rate of the rolled sheet is reduced. Furthermore, if the rolling direction is alternately reversed while the crossing angle of the upper and lower work rolls is kept constant for each stand, the torsional rate of the rolled sheet is reversed for each stand, and its absolute value is Although it is smaller than when rolling is performed with the cross direction of the upper and lower work rolls being the same, it still increases as the rolling is performed by the rear stand.

FIG. 4 shows the correlation between the crossing angle of the upper and lower work rolls at the fourth stand and the torsion of the rolled plate after passing through the fourth stand. That is, in the tandem rolling mill, the crossing angle (0.75 deg) and the crossing direction of the upper and lower work rolls are made constant in the first to third stands.
By changing only the intersection angle at the stand to 0.25 to 1.0 deg, the thickness of high-strength steel (TS: 100 kgf / mm ² ) plate from 3.2 mm
It shows the torsion of the rolled sheet after passing through the fourth stand when rolling to 1.2 mm. The rolling reduction at the fourth stand was 15%.

FIG. 4 shows that the surface roughness R _max of the work rolls from the first to the fourth stands is 5 μm (the symbol in the figure: ○).
), 3μm (symbol in the figure: ◇), 2μm (symbol in the figure: □), 1.5μm (symbol in the figure: △) and 1μ
m (symbol in the figure: ● mark) shows the torsion rate of the rolled sheet when it is set to 5 levels.

The following can be seen from FIG. When the surface roughness of the work roll is constant, the smaller the intersection angle between the upper and lower work rolls at the fourth stand, the lower the torsion rate of the rolled plate. When the crossing angle is 0.75 deg, the torsion rate of the rolled sheet is maximized, and when it is larger than 0.75 deg, the torsion rate of the rolled sheet decreases again.

FIG. 5 shows the correlation between the rolling reduction at the final stand and the torsion of the rolled sheet after passing through the final stand. That is, in the tandem rolling mill, up to the first to fourth stands, the crossing angle of the upper and lower work rolls (crossing angle of 0.75 deg at which the torsion rate of the rolled plate becomes maximum) and the crossing direction and the rolling reduction (20%) are kept constant. High-strength steel (TS: 100 kgf / mm ² ) is rolled to a thickness of 3.2 mm to 1.3 mm, and then the fifth stand (final stand) is used to reduce the upper and lower work rolls without intersecting only the rolling reduction. Shows the torsion of the rolled sheet when rolling is performed while changing the value of the rolled sheet to 0 to 20%.

FIG. 5 shows that the surface roughness R _max of the work rolls of the first to fifth stands is 5 μm (the symbol in the figure: ○).
), 3 μm (symbol in the figure: ◇), 1.5 μm (symbol in the figure: △), and 1 μm (symbol in the figure: ●) indicate the twist ratio of the rolled sheet when it has four levels. It is.

The following can be seen from FIG. Regardless of the magnitude of the torsion rate up to the fourth stand, unless the upper and lower work rolls intersect at the final stand, the torsion rate of the rolled sheet decreases significantly as the rolling reduction at the final stand increases,
When the rolling reduction exceeds 5%, the twist of the rolled plate as a product hardly causes a problem, and when the rolling reduction exceeds 10%, the rolling plate does not twist at all. Incidentally, if the rolling reduction is small surface roughness R _max of the work roll even 10% or less, but torsion of the rolled plate is small enough to almost negligible, the reduction rate 10
% Is not practical because the rolling efficiency is poor.

As described above, if the work is rolled by using a tandem rolling mill and rolling the plate without intersecting the upper and lower work rolls only in the final stand in a plane parallel to the plate (parallel rolling method), the twist of the rolled plate is reduced. It was explained that it can be reduced. However, it is clear from the above description that parallel rolling is not necessarily performed only on the final stand but may be started from a middle stand in order to remove the twist of the rolled plate. Furthermore, these findings obtained using a tandem rolling mill apply just as well to the case of a reversing rolling mill capable of roll cross rolling.

Summarizing the above, when rolling is performed by the roll-cross rolling method, if at least the final stand (in the case of a tandem rolling mill) or at least the final pass (in the case of a reversing rolling mill) is rolled by the parallel rolling method, the rolling is performed. The twist of the plate can be made extremely small. Furthermore, according to the torsion rate of the cold rolled steel sheet in roll cross rolling,
If the rolling reduction in the parallel rolling is made sufficiently large, a rolled sheet having no twist can be obtained.

As described above, even if only the crossing direction of the upper and lower work rolls is alternately reversed for each stand (each pass), the torsion rate of the rolled sheet increases at the rear stand (rear pass). It is not a fundamental solution. However, since the absolute value of the torsion of the rolled plate is reduced as compared with the case where the crossing direction of the upper and lower work rolls is kept the same, the crossing direction of the upper and lower work rolls is set to each stand in addition to the rolling method of the present invention. It is even more desirable to adopt a method of rolling by alternately inverting each (each pass).

[0026]

[Examples] Tables 1-1 and 1 were prepared by a five-stand tandem rolling mill capable of pair-cross rolling with a work roll diameter of 460 mm and a one-stand reversing mill capable of pair-cross rolling with a work roll diameter of 380 mm. -2 steel type,
The plate material showing the material thickness and the finish thickness was rolled. The surface roughness of the work roll was set at two levels of 1.5 μm and 5 μm.
The torsion ratio of the rolled sheet after rolling is also shown in Table 1-1 and Table 1-2.

Test Nos. 1 to 6 are examples of the present invention. This is the case where parallel rolling (work roll intersection angle is 0 deg) at the final stand, and the case where the surface roughness of the work rolls at the fourth to fifth stands is reduced from 5 μm to 1.5 μm. As a result, although the rolling reduction at the final stand was as small as 5%, the torsion of these rolled plates was extremely low,
The level was practically no problem. Furthermore, there was almost no passing trouble in the continuous annealing furnace after the rolling.

Test Nos. 7 to 12 are examples of the present invention. Test No.1
As in the case of ~ 6, this is the case where parallel rolling (work roll intersection angle is 0 deg) at the final stand. However, test Nos. 1 to 6
In this case, the surface roughness of the upper and lower work rolls was 5 μm on all stands and the rolling reduction was 10% on the final stand. As a result, the torsion rate of these rolled plates was extremely low, and was at a level at which there was no problem in practical use.
Furthermore, there was almost no passing trouble in the continuous annealing furnace after the rolling.

Test Nos. 13 to 16 are examples of the present invention. Test N
As in o.1-6, this is the case where parallel rolling (work roll intersection angle is 0 deg) is performed in the final pass. As a result, the torsion rate of these rolled plates was extremely low, and was at a level at which there was no problem in practical use. Furthermore, there was almost no passing trouble in the continuous annealing furnace after the rolling.

Test Nos. 17 to 32 are comparative examples. This is the case where roll cross rolling is performed even at the final stand (final pass). These rolled sheets were twisted, and the commercial value of the rolled sheets was extremely low. Moreover, the passing trouble in the continuous annealing furnace after rolling was almost four times as large as that of the example of the present invention.

[0031]

[Table 1-1]

[0032]

[Table 1-2]

[0033]

According to the method of the present invention, it is possible to prevent the twist of the rolled plate occurring in the roll cross rolling by a relatively simple method. As a result, a high-quality cold-rolled steel sheet can be manufactured with high productivity.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a three-dimensional view for explaining that the rolled plate is twisted by the geometrical arrangement of the work rolls in roll cross rolling, and FIG.

FIG. 2 is a diagram illustrating a method for calculating a torsion ratio of a rolled plate.

FIG. 3 is a view showing a torsion ratio of a rolled plate every time a stand passes.

FIG. 4 is a diagram showing a correlation between an intersection angle of upper and lower work rolls in a final stand and a torsion rate of a rolled plate after passing through the final stand.

FIG. 5 is a diagram showing a correlation between a reduction ratio at a final stand and a torsion ratio of a rolled plate after passing through the final stand.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Masui 4-33, Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. (72) Inventor Hiroshi Matsuda 4-chome, Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima 6-22 Mitsubishi Heavy Industries, Ltd.Hiroshima Works (72) Inventor Kazuhiko Horie 4-2-2 Kanon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd.Hiroshima Works (72) Inventor Hideaki Furumoto Hiroshima City, Hiroshima Prefecture 4-6-22 Kannonshinmachi, Nishi-ku, Hiroshima Laboratory, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-58-61902 (JP, A) JP-A-58-138505 (JP, A)

Claims (2)

(57) [Claims] When rolling is performed by a roll cross rolling method using a multi-high rolling mill having a plurality of roll stands,
A method for rolling a cold-rolled steel sheet, wherein at least a final stand is rolled by a parallel rolling method. 2. A method for rolling a cold-rolled steel sheet, wherein rolling is performed by a parallel rolling method at least in a final pass when rolling is performed by a one-stand reversing rolling mill by a roll cross rolling method.