JP2782860B2 - Strip cold rolling method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for cold rolling a strip, and more particularly to transferring a roughness to a strip surface with a dull roll.
The present invention relates to a novel strip cold rolling method capable of improving the flatness of a strip.

(Prior art) Conventional tandem rolling mill train 30 for steel sheets or strips
Is shown in FIG. Usually, this is mainly 4 stands to 6 stands, and each stand is mainly 4Hi (6Hi) mill. Taking Fig. 3 as an example, among No.5 stands, No.1 ~
The 4 stands are rolled by a bright roll with a reduction rate of 25 to 50% to reduce the thickness of the strip to be rolled.
The final stand of the No. 5 stand employs a method in which the work rolls indicated by oblique lines in the figure are dull rolls, which are lightly rolled by 3 to 8%, and the roughness of the rolls is roll-transferred to the plate surface.
In the figure, reference numeral 32 denotes a shape detector.

Such dull surface transfer is for roughening the strip surface (Rmax ≒ 3 to 10 μm) to prevent seizure at the time of annealing in the next step and to improve the adhesion of the coating film at the time of coating performed by the user. The dull roll processing in this case is generally shot processing, electric discharge processing, laser, corrosion or the like.

The plate shape, that is, the flatness of the plate is greatly affected by the tension on the exit side of the rolling mill. In particular, the higher the tension is, the better the flatness becomes (although there is an upper limit from the viewpoint of the prevention of plate breakage).
In the conventional rolling line of the configuration as shown in the figure, the winding tension is also increased, thereby tightening the winding, buckling after removing the coin,
Various problems occur, such as seizure during annealing and bending of the take-up reel. Therefore, as one measure, as shown in FIG. 4, a bridle between the multi-stage rolling mill row 40 and the winding machine 42 is provided so that the rolling mill output side tension (σ _f ) and the winding tension (σ _R ) can be set separately. A method of installing the roll 44 has been proposed.
Note that, also in the illustrated example, dull rolls are shown with diagonal lines.

Or "Nissin Steel Technical Report No. 25, November 1971" Nos. 1-9
2Hi on the rolling mill exit side as shown in Fig. 1 on the page
There is a method in which a mill can be installed to enable individual control of σ _f and σ _R. However, this 2Hi mill has almost negligible ability to reduce the strip, and only applies tension.

(Problems to be Solved by the Invention) However, the above-described prior art has the following problems.

(1) In FIG. 1, the final stand is under light pressure, but requires a large mill similar to the others. In addition, since the winding tension of the final stand is lower than the tension between the stands, the motor power is large.

(2) A 2Hi mill is ideal for dull transfer, but if a dull roll is incorporated into a multi-stage mill of 4Hi mill or more, the change in the roughness of the dull roll (wear) is remarkable and the roughness of the strip surface is not stable.

(3) Since the winding tension (= the tension on the mill exit side) is low, the finished shape is not good (the higher the tension, the better the shape).

(4) If bridle rolls are installed as shown in FIG. 4, the exit side of the mill is set to a high tension, and the winding tension is set to a low tension, the number of troubles in passing the end of the strip increases and the space increases. Strip surface flaws tend to occur due to slippage between the bridle roll and the strip.

(5) For roughness transfer, non-lubricated rolling is ideal (transfer beautifully), but in FIGS. 3 and 4, the same rolling oil as that of the preceding stand is used. Oil pits and other irregularities are present. However, it is difficult to install rolling oil wipers between stands.

(6) The technology for improving the flatness by controlling the actuator of a rolling mill by introducing a shape detector is time-delayed, and is unsatisfactory in the attained level, and the shape detector is very expensive. A tension leveler is ideal for stabilizing the shape.

An object of the present invention is to solve these problems and to provide a cold strip rolling method having excellent characteristics.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have conducted intensive studies and, as a result, have newly found the following points.

In other words, by using 2Hi mill as the final stand for dull transfer, it is possible to reduce equipment costs, stabilize dull transfer rolling, and improve product quality, and control the speed of the 2Hi mill to output the final multi-stage mill stand. The tension can be increased to stabilize the rolled shape to a higher degree, and appropriate winding tension can be set, so that a strip having a good flatness can be obtained.

Further, a wiper may be provided between the final multi-stage mill stand and the 2Hi mill stand to cut off rolling oil and transfer dull in a non-lubricated oil state with the 2Hi mill. A leveler having a high tension between the stand and the leveler may be introduced to act as a tension leveler. In this case, a strip with good flatness can be obtained without shape control.

Thus, the gist of the present invention is that a two-high rolling mill is installed between a multi-high rolling mill and a winder that constitute the final stand of a cold rolling mill, and at least one of the two-high rolling mills is rolled. The roll is a dull roll, and the two-high rolling mill performs light reduction rolling, for example, light reduction rolling to a reduction ratio of 3 to 8% to transfer the rough surface of the roll to the material to be rolled. Increase the rotation speed of the two-high mill,
The tension between these two rolling mills is made higher than the winding tension, a wiper device is provided between both the multi-high rolling mill and the two-high rolling mill, and the rolling oil of the multi-high rolling mill is shut off. A rolling method is a cold rolling method for strip, wherein non-lubricated rolling is performed.

Further, a staggered leveler is installed between both the multi-high rolling mill and the two-high rolling mill, the flatness is corrected by a tension leveler action, and then the dull transfer is slightly reduced by the two-high rolling mill. It may be.

In addition, as a cold rolling mill in the present invention, a tandem rolling mill generally including a plurality of stands is exemplified, but when performing reversal rolling, a single multi-high rolling mill may be used.

(Operation) Next, the present invention will be described more specifically with reference to the accompanying drawings.

FIG. 1 is a schematic explanatory view of a rolling mill row 10 for carrying out a cold rolling method according to the present invention, in which an unwound strip 1 is composed of a plurality of multi-high rolling mills.
Cold rolling is performed through a multi-stage rolling mill row 10 of No. 1 to No. 4 stands. A 2Hi mill 4 is installed downstream of the final multi-high rolling mill row, and at least one of the work rolls of the 2Hi mill is formed as a dull roll as shown by hatching in FIG.
Dull transfer rolling is performed by the i-mill 4. After the completion of the rolling, the strip 1 is wound on a winder 5 with a predetermined tension.

In the case of FIG. 1, the tension between the stands σ _f is increased by controlling the rotation speed of the 2Hi mill (0.3σ _y ≦ σ _f ≦ 0.7σ _y ) to achieve a high-order stabilization of the rolled shape, and the winding tension σ _R is as small as possible. It is possible to prevent seizure at the time of holding down (σ _R ≦ 0.15σ _y ) and to prevent the coil from being crushed after the coil is pulled out. Here, σ _y is the yield stress of the strip material.

FIG. 2 shows another modification of the present invention, in which a wiper 7 is installed between the final stand (No. 4 stand) and the 2Hi mill stand 4 and lubricating oil is not applied on the 2Hi mill 4. Roll (including leaving the plate as it is) and transfer a good dull pattern. The wiper 7 may be, for example, a high-pressure air jet, a squeezing pinch roll, etc., but is not particularly limited as long as it has a mechanism capable of substantially removing the rolling oil.

As described above, according to the present invention, the final stand (No. 4
Since the tension between the stand and the rolling stand of the 2Hi mill 4 can be made high tension, if levelers 9 arranged in a zigzag pattern are installed as shown in FIG. Since a high degree of flatness can be ensured, an expensive automatic shape control system using a shape detector as shown in, for example, FIGS. 3 and 4 becomes unnecessary.

(1) Comparison of 4Hi and 2Hi mills related to dull transfer rolling: In the rolling line of FIG. 1, for example, a 250φ2Hi mill and a 250φ / 500φ4Hi mill are provided on the exit side of a multi-high rolling mill, and 0.4t × 300w. According to the experimental values of full-rolled steel rolled continuously at a rolling reduction of 5%, as shown in the graph in Fig. 5, the roughness change is large in the 4Hi mill, but the change width is small and stable in the 2Hi mill. Turned out to be.

(2) Relationship between plate shape steepness (λ) and sheet breaking ratio by multi-high rolling mill and front tension σ _f : 0.8t × 1225w (mm) strip (cold rolled steel plate)
Rolled by the tandem mill shown in the figure and the final stand exit side tension σ _f
As shown in the graph of FIG. 6, the strip shape in the case where is changed is steepness λ (= h / l × 100%, h: wave height, l:
It can be seen that the wave pitch) becomes sharply good when σ _f > 0.3σ _y . In particular, when a leveler is provided, the steepness is σ _f >
Good at 0.2σ _y .

On the other hand, as is clear from the graph shown in FIG. 6 as well, the higher the tension, the higher the sheet breaking ratio, but σ _f > 0.7σ
It increases sharply at _y .

From the _{above, 0.3σ y ≦ σ f ≦ 0.7σ} y is desirable.

(3) Transfer rate of roll roughness to strip due to dull and wet: Roll when 1.0t × 200w strip (cold rolled steel sheet) is cold rolled with a 250φ / 500φ4Hi mill while changing the rolling reduction with or without lubrication. FIG. 7 is a graph showing the ratio between the surface maximum roughness R _R and the strip surface maximum roughness Rs. It can be seen that non-lubricated (a little oil may be applied to the plate surface) has a higher transfer rate and provides a beautiful dull pattern.

(4) winding tension: sigma Higher _R occurs seizure in batch annealing, especially problematic in high-temperature annealing. Empirically, it is desirable that σ _R ≦ 5 kgf / mm ² .

(5) Leveler effect: In the tandem mill shown in FIG.
When the tension was changed by incorporating a leveler consisting of φ × 4 (extension unit) and 250φ / 80φ / 250φ (correction unit), the steepness was 0.5% or less due to the tension leveler effect as shown by the dotted line in FIG. It has been found that a high level of flatness (mainly 0.3% or less) can be easily obtained.

With an automatic shape control system using a conventional shape detector, steepness of 0.3% or less was difficult to achieve.
It can be seen that the method of the invention is much better.

(Example) The present invention will be described in detail with reference to examples.

Comparative Example 5-stand tandem mill (580φ / 1422φ × 14 in FIG. 3)
The rolling mill outlet side of 50l) was modified and a 650φ2Hi mill was installed downstream to form the mill arrangement shown in Fig. 1. Both 650φ work rolls of the 2Hi mill were subjected to laser dulling with an Rmax of 5 μm, and chrome plating was applied thereon.

Conventionally, the winding tension was limited to σ _R ≦ 5 kgf / mm ² (σ _f is also 5 kgf / mm ² or less). In this example, 0.3σ _y ≦ σ _f ≦ 0.7σ _{y by} controlling the speed of the 2Hi mill. And σ _R ≦ 5kgf / mm ²
As a result, the following results were obtained.

The indentation flaw of the dull roll decreased sharply.

Dull rolls were replaced by rolling 50 km in the past, but 200 km
There was no problem with rolling, and the variation in plate roughness was reduced to 1/3 or less of the conventional value.

Flatness became conventional 0.4 to 1.2% (mean 0.8% approximately) was although there are sigma _f high tensile effect from 0.3 to 0.7% (average of about 0.5%).

Example 1 In this example, 40φ × 4 extension units and 250φ / 80φ / 2
The strip was cold rolled by a rolling line incorporating a leveler comprising a 50φ straightening unit as shown in FIG. Three rows of ultra-high pressure air jet nozzles were arranged as wipers to substantially prevent the flow of rolling oil into the 2Hi mill.

 The following results were obtained.

The dull roll transfer rate was increased, the beautifulness of the surface by visual observation was improved by one rank, and the plate stain was reduced.

When σ _{f is set} to σ _f > 0.3σ _y and the leveling amount of the leveler is adjusted, a plastic elongation of 0.2 to 0.5% is given by the leveler.
% Of the coils had a flatness of 0.3% or less.

Trouble on the downstream side was reduced by the significant improvement of the plate shape, and the total yield was improved by 0.2%.

Example 2 A 600φ 2Hi mill 82 was installed downstream of a 480φ / 1400φ / 1600l revers mill 80 having a roll arrangement shown in FIG. Both the upper and lower rolls were dull rolls. 7 pass finished product (0.
Rolling was performed with the 2Hi mill open for up to 6 passes for 5t x 1000w), and the rolling was the same as before. However, in the final pass, the downstream 2Hi mill was also reduced to increase σ _f and improve the sheet shape. With a 2Hi mill. The winding tension was as low as possible. In this example, the following results were obtained.

The roll change time for bright roll and dull roll could be omitted. Conventionally, dull transfer was performed after the roll change in the final pass.

The flatness improved significantly from 0.9% to 0.6%.

The dull roughness can be stabilized and beautiful.

(Effect of the Invention) Since the present invention is configured as described above,
Remarkable effects such as reduction of the investment amount of the new mill, improvement of the flatness of the strip, improvement of the surface properties of the strip, and the like are achieved, which is extremely useful in industry.

[Brief description of the drawings]

1 and 2 are schematic explanatory views of a tandem mill for carrying out a rolling method according to the present invention; FIGS. 3 and 4 are schematic explanatory views of a conventional tandem mill; FIG. 6 is a diagram illustrating the relationship between the effect of 2Hi and 4Hi in rolling; FIG. 6 is a diagram illustrating the relationship between the mill exit side tension, the plate shape, and the breaking ratio; FIG. FIG. 8 is an explanatory view of an embodiment using a lever mill. 1: Strip, 4: 2Hi mill 5: Winder, 7: Wiper 9: Leveler, 10: Cold rolling mill

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B21B 1/22-1/24 B21B 1/28 B21B 45/00-45/02

Claims (2)

(57) [Claims] 1. A two-high rolling mill is provided between a multi-high rolling mill and a winder constituting a final stand of a cold rolling mill, and at least one of the two-high rolling mills is a dull roll. The rolling rough surface is transferred to the material to be rolled by performing light reduction rolling by the two-high rolling mill, and the rotation speed of the two-high rolling mill is increased from the rotation speed of the multi-high rolling mill. The tension is made higher than the winding tension, a wiper device is provided between both the multi-high rolling mill and the two-high rolling mill, and the rolling oil of the multi-high rolling mill is shut off. Cold rolling method for a strip. 2. A staggered leveler is installed between both the multi-high rolling mill and the two-high rolling mill, and the flatness is corrected by a tension leveler action. 2. The method for cold rolling a strip according to claim 1, wherein the strip is rolled.