JP7200918B2 - Cold-rolling method for steel plate and method for manufacturing cold-rolled steel plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for cold rolling a steel plate and a method for manufacturing a cold rolled steel plate.

As a method for cold rolling a steel plate, there is a method described in Patent Document 1, for example.
In Patent Document 1, as a method of cold rolling even difficult-to-roll materials such as electromagnetic steel sheets and high-strength steel sheets without causing sheet breakage, the unit tension at the width end of the steel sheet on the delivery side of the rolling mill is set to zero. describes rolling while controlling the shape of the steel plate with an actuator.

JP 2019-141874 A

However, since the target material of the Sendzimir rolling mill is a material to be rolled at a high tension, it is difficult to make the unit tension at the edge of the strip width zero in rolling by the Sendzimir rolling mill.
SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a technique that enables more stable rolling in the Sendzimir rolling mill.

The inventors have found that in the rolling pass where the strip temperature is high in rolling by the Sendzimir rolling mill, the strip width edge becomes a tension shape due to the growth of the thermal crown, and the unit tension at the strip width edge cannot be made zero. It was found to be difficult. Furthermore, the inventors have found that even with the same material and the same final target strip shape, by changing the target shape of the steel strip in each pass according to the strip temperature of the steel strip rolled by the Sendzimir rolling mill, It was found that more stable rolling becomes possible.
In order to solve the problem, a steel sheet cold rolling method according to one aspect of the present invention is a cold rolling method for cold rolling a steel sheet by a Sendzimir rolling mill in a plurality of passes. The target shape of the steel sheet in the first pass, in which the temperature of the steel sheet to be rolled is determined to be 200 ° C. or higher, is higher than the target shape of the steel plate in the second pass, in which the temperature of the steel plate to be rolled is determined to be less than 200 ° C. The gist is to set it in an elongated shape.
Another aspect of the present invention is a method for manufacturing a cold-rolled steel sheet, which includes a cold-rolling step according to the method for cold-rolling a steel sheet according to the above aspect.

According to the aspect of the present invention, rolling by the Sendzimir rolling mill can be performed more stably by changing the target shape of the rolling pass according to the plate temperature of the steel plate to be rolled. As a result, according to the aspect of the present invention, it is possible to obtain the desired cold-rolled steel sheet.

1 shows a Sendzimir rolling mill according to an embodiment of the invention; FIG. It is a figure explaining an intermediate roll shift mechanism which shifts an intermediate roll. It is a figure explaining the structure of a shape control part. It is a figure which shows the example of a target shape.

Next, embodiments of the present invention will be described with reference to the drawings.
In this embodiment, as shown in FIG. 1, a Sendzimir rolling mill 1 reverse-rolls a steel sheet 10 in multiple passes to produce a cold-rolled steel sheet. At this time, in the present embodiment, the plate temperature of the surface of the steel plate 10 is determined (estimated) for each rolling pass, and when the plate temperature of the steel plate 10 is determined to be 200 ° C. or higher, the plate temperature is determined to be less than 200 ° C. Compared to the case, the target shape of the steel sheet 10 to be rolled in the pass is set to a sheet shape having a more edge-elongated shape, and the steel sheet 10 is rolled by the Sendzimir rolling mill 1 .

In this embodiment, the target shape of the rolling pass is changed according to the plate temperature of the steel plate to be rolled, and the above multiple passes are divided into the first pass and the second pass according to the conditions of the target shape of the rolling pass. and Specifically, among the above multiple passes, the pass in which the temperature of the steel sheet to be rolled is determined to be 200°C or higher is defined as the first pass, and the temperature of the steel plate to be rolled is determined to be less than 200°C. Let the pass be the second pass.
In the present embodiment, the term "pass" refers to a process in which the steel sheet 10 passes through the Sendzimir rolling mill 1 and is subjected to reduction, and the unit of passing in one direction is called one process (one pass). Thus, if the steel plate 10 passes through the Sendzimir mill 1 in one direction and then in the opposite direction, the total number of passes is two.

Here, the “more edge stretched shape” is to relatively increase the edge stretched shape. The I-unit value is set to a plate shape with a larger value. In this embodiment, when the plate temperature of the steel plate 10 is less than 200° C., the target shape of the steel plate 10 does not necessarily have to be the edge-elongated shape. One of the characteristics of the present embodiment is that the target shape of the rolling is changed when the sheet temperature of the steel sheet 10 to be rolled by the Sendzimir rolling mill 1 is 200° C. or more and less than 200° C. even if the other rolling conditions are the same. .

<I-unit value>
In general, steepness or differential elongation is used as an evaluation method for a belt-like shape of a steel plate or the like. The steepness λ is expressed by the following equation using the wave height H and the wave pitch L in the longitudinal direction (rolling direction) of the band.
λ=H/L
The differential elongation rate Δε is expressed by the following equation using the length ΔL of the stretched portion.
Δε=ΔL/L
The difference in elongation [I-unit] is expressed by ε×10 ⁵ . 1I-unit, which is the unit difference in elongation, is given by the following equation where the length ΔL of the elongated portion is 10 μm (0.01 mm) with respect to the reference length L=1 m (=1000 mm).
1I-unit = 0.01mm/1000mm
That is, 1I-unit=1.0×10 ⁻⁵ . The larger the difference in elongation [I-unit] is, the more elongated the strip shape is. A non-contact three-dimensional measuring device is used to measure the I-unit value.

The present embodiment will be described in detail below.
<Sendzimir rolling mill 1>
As shown in FIG. 1, the Sendzimir rolling mill 1 includes a pair of work rolls 1a, a first intermediate roll 1b, a second intermediate roll 1c, and a backup bearing 1d (backing assembly) for rolling a steel plate 10 (rolling material) from above and below. consists of
The Sendzimir rolling mill 1 performs reciprocating rolling (reverse rolling) of the steel plate 10 by switching the conveying direction (the direction of the pass line) of the steel plate 10 between one direction (for example, from left to right on the paper surface) and the opposite direction (for example, from right to left on the paper surface). ). Reels 2 are arranged upstream and downstream of the Sendzimir rolling mill 1, respectively. The reel 2 functions both to wind and unwind the steel sheet 10 depending on the rolling.

The Sendzimir rolling mill 1 has an intermediate roll shift mechanism for shifting intermediate rolls as a mechanism for controlling the shape of the steel sheet, as shown in FIG. That is, as shown in FIG. 2, the first intermediate roll 1b has a tapered shape on one end side in the axial direction. By shifting to , the load on the work roll 1a is controlled, and the steel sheet 10 is rolled so as to have the target shape. Shift control of the first intermediate roll 1b is performed by a signal from the shift control section 3C supplied to the actuator 4. As shown in FIG.
FIG. 2(b) shows a state in which the first intermediate roll 1b is shifted by a predetermined amount with respect to FIG. 2(a).

<Cold rolling>
Using the Sendzimir rolling mill 1 configured as described above, a target cold-rolled steel sheet is produced by reverse rolling a steel sheet 10 as a rolled material by a preset number of passes. Here, a pass schedule is set according to the target thickness of the cold-rolled steel sheet, and the rolling conditions for each pass are set.
As shown in FIG. 3, the shape control section 3 of the cold rolling method of this embodiment includes a pass temperature determination section 3A, a shape setting section 3B, and a shift control section 3C.

<Pass temperature determination unit 3A>
The pass temperature determination unit 3A determines the plate temperature of the steel plate 10 in each rolling pass when manufacturing the target cold-rolled steel plate.
Here, the steel plate 10 is rolled by the Zenzima rolling mill, and the temperature of the steel plate rises due to heat generated during processing. The amount of increase in the sheet temperature due to heat generated by processing differs depending on the material of the steel sheet 10 and how thin the sheet is made by each rolling. Here, it is assumed that the steel plate 10 reaches 200° C. or higher in about 5 passes, for example.
In the present embodiment, it is possible to determine in advance which of the rolling passes is to be rolled at a strip temperature of 200° C. or higher based on a preset pass schedule.

That is, the pass temperature determination unit 3A estimates the amount of heat generated by rolling in each pass based on a preset pass schedule, and from the estimated value, the plate temperature of the steel plate 10 rolled in each pass is 200° C. or higher. Determine (estimate) whether or not
When descaling is appropriately performed after rolling in each pass, the sheet temperature determination for the next pass is performed including the temperature drop due to the descaling.
Further, as shown in FIG. 1, temperature sensors 20 are arranged on the entry side and the exit side of the rolling mill, and the pass temperature determination section 3A determines the strip temperature detected by the temperature sensor 20 on the exit side of the preceding pass. The plate temperature of the steel plate 10 in the target pass may be determined. At this time, if a descaling facility is provided, the temperature sensor 20 is preferably provided on the output side of the descaling facility.

<Shape setting unit 3B>
The shape setting section 3B sets the target shape of the steel sheet 10 in each rolling pass based on the determination by the pass temperature determination section 3A.
In the shape setting unit 3B of the present embodiment, when it is determined that the sheet temperature of the steel sheet 10 rolled by the Sendzimir rolling mill 1 is 200 ° C. or higher for each pass, compared to the case where the sheet temperature is determined to be less than 200 ° C. The target shape of the steel plate 10 is set to a plate shape closer to the edge extension shape side. For example, the shape setting unit 3B sets the initial target shape of the steel plate 10 in the pass without considering the growth of the thermal crown, and when it is determined that the temperature of the steel plate 10 to be rolled is 200° C. or higher, The target shape is changed from the initial target shape described above to a plate shape closer to the edge extension shape.

At this time, when the sheet temperature of the steel sheet 10 to be rolled is determined to be 200° C. or higher, the target shape of the steel sheet 10 is set so that the I-unit value at both ends of the steel sheet is lower than the I-unit value at the center of the steel sheet as the first pass. It is preferable to set the plate shape to a value greater than 10. Further, when it is determined that the temperature of the steel sheet 10 to be rolled is less than 200° C., it is preferable to set the target shape of the steel sheet 10 to a flat shape as the second pass.
Here, the I-unit value at the center of the steel sheet in the target shape is set to approximately the same value regardless of whether the target shape is a flat shape or an elongated edge shape. The I-unit value at both ends in the width direction of the steel plate 10 when the target shape is a flat shape is 10 or more than the I-unit value at both ends in the width direction of the steel plate 10 when the target shape is a flat shape. It can be said that there is.

In addition, when the plate temperature of the steel plate 10 to be rolled is determined to be 200 ° C. or higher, the I-unit value at both ends of the steel plate 10 in the target shape of the steel plate 10 is 10 compared to the case where the plate temperature is determined to be less than 200 ° C. It is preferable to set the value to a value larger than that. The I-unit value at the central portion of the steel plate 10 is assumed to be "0".
Here, in the present embodiment, the term "edge-stretched shape" means that the I-unit value at both ends in the width direction of the steel plate 10 in the target shape is larger than the I-unit value at the central portion. In addition, the flat shape means that the I-unit value at both ends in the width direction of the steel plate 10 in the target shape is equal to or less than the I-unit value at the central portion or is less than 10 greater than the I-unit value at the central portion. . Incidentally, I-unit is generally used as a unit indicating a steel sheet shape based on a differential elongation ratio of 1×10 ⁻⁵ .

<Shift control unit 3C>
The shift control unit 3C performs a process of shifting the first intermediate rolls 1b via the actuators 4 so that the steel sheet 10 has the target shape set by the shape setting unit 3B before rolling in each pass. do.
That is, the shift control unit 3C calculates the axial position of the intermediate rolls corresponding to the target shape of the steel plate 10 set by the shape setting unit 3B by a known method, and from the calculation result and the current positions of the intermediate rolls, , the shift amount (including the shift direction) of the intermediate roll is obtained, and the calculated shift amount is output to the actuator 4 after the gain is adjusted with a preset control gain. In the case of PID control, the control gain is a control amount to be multiplied by each control term. To increase the control gain means to increase the control gain of at least one of the control gains of each control term. Point.

The actuator 4 shifts the first intermediate roll 1b according to the input signal.
Here, when it is determined that the temperature of the steel sheet 10 to be rolled is 200° C. or higher, the control gain related to the shift of the intermediate rolls can be set to a larger value than when it is determined that the temperature is less than 200° C. preferable.
The control gain is preferably set to a larger value as the amount of Si contained in the steel sheet 10 to be rolled increases.
Furthermore, the control gain is preferably set to a larger value as the temperature of the steel sheet 10 to be rolled increases.

<Operation and others>
In the cold rolling method using the Sendzimir rolling mill 1 configured as described above, the target shape of the steel sheet 10 is set according to the sheet temperature of the steel sheet 10 in each pass of rolling, and rolling is performed in each pass, To produce the desired cold-rolled steel sheet.
For example, in 10-pass rolling, the temperature of the steel sheet 10 to be rolled is determined to be less than 200° C. in the 1st to 5th passes, and the temperature of the rolled steel plate 10 is determined to be less than 200° C. in the 6th to 10th passes. Suppose that it is determined as above. In this example, passes 1 to 5 correspond to the second pass, and passes 6 to 10 correspond to the first pass.
In this case, in the present embodiment, in the 1st to 5th passes at which the plate temperature is less than 200°C, the target shape of the steel plate 10 is rolled as a flat shape, whereas the 6th pass at which the plate temperature is 200°C or higher. In passes 10 to 10, rolling is performed with the target shape of the steel plate 10 set to the edge-elongated shape (see FIG. 4).
As described above, in the present embodiment, by changing the target shape of the rolling pass according to the temperature of the steel sheet 10 to be rolled, rolling by the Sendzimir rolling mill 1 can be performed more stably. As a result, in the present embodiment, it is possible to more stably produce the intended cold-rolled steel sheet.

<Modification>
In the above description, control by the roll bender mechanism was exemplified as the shape control of the steel plate 10, but the shape control of the steel plate 10 may adopt known control other than the roll bender mechanism. For example, the shape control of the steel plate 10 may be performed by a roll bender mechanism that changes the amount of axial deflection of the work roll 1a, a VC roll mechanism that operates the roll crown by hydraulic pressure, or the like.
Further, in the above description, the cold rolling mill to which the steel sheet cold rolling method of the present application can be applied is the Sendzimir rolling mill. Other known cold rolling mills include, for example, tandem rolling mills and single stand rolling mills. At the time of the filing of the present application, the steel sheet temperature does not normally reach 200° C. due to the heat generated during tandem rolling or single stand rolling, so these examples are not described. However, for example, when rolling is performed by raising the steel sheet temperature to 200° C. or more using a heating device before rolling or between passes, the same problem as in the present application may occur. Under the problem of stable rolling, when it is determined that the steel sheet temperature to be rolled will be 200 ° C. or higher in the cold rolling method with a tandem rolling mill or a single stand rolling mill, the cold rolling method of the steel sheet of the present application is applied. may

<effect>
This embodiment has the following effects.
(1) The present embodiment is a steel sheet cold rolling method for cold rolling a steel sheet 10 by a Sendzimir rolling mill 1 in a plurality of passes, wherein the sheet temperature of the steel sheet 10 to be rolled in the plurality of passes is 200° C. or higher. The target shape of the steel sheet 10 in the first pass determined to be a flatter shape than the target shape of the steel sheet 10 in the second pass determined that the temperature of the steel sheet 10 to be rolled is less than 200°C is set.
According to this configuration, it is possible to set a more appropriate target shape according to the plate temperature of the steel plate 10 to be rolled, and rolling by the Sendzimir rolling mill 1 can be performed more stably.

(2) In addition, the present embodiment is a cold rolling method in which the steel sheet 10 is cold rolled in a plurality of passes by the Sendzimir rolling mill 1, and the sheet temperature of the steel sheet 10 to be rolled in the plurality of passes is 200° C. or higher. The I-unit value of both ends set as the target shape of the steel sheet 10 in the first pass determined as It is set to a value that is 10 or more larger than the I-unit value of both ends set as the target shape.
According to this configuration, it is possible to more reliably set the target shape of the steel sheet 10 when it is determined that the temperature of the steel sheet 10 to be rolled is 200° C. or higher.
(3) As the target shape of the steel plate 10 in the first pass, it is preferable to set the I-unit value at both ends of the steel plate to a value 10 or more larger than the I-unit value at the central portion of the steel plate.
According to this configuration, the target shape of the steel plate 10 in each pass can be set more reliably.

(4) In the present embodiment, the Sendzimir rolling mill 1 is provided with an intermediate roll shift mechanism for shifting the intermediate rolls as a mechanism for controlling the shape of the steel sheet, and the control gain for the shift of the intermediate rolls is set to the temperature of the steel sheet 10 to be rolled. is determined to be 200° C. or more, a larger value is set than when the plate temperature is determined to be less than 200° C.
For example, the control gain is set to a larger value as the amount of Si contained in the steel sheet 10 to be rolled increases. Also, for example, the control gain is set to a larger value as the temperature of the steel sheet 10 to be rolled increases.
According to this configuration, breakage during rolling can be further suppressed, and rolling by the Sendzimir rolling mill 1 can be performed more reliably and stably (see Examples described later).
(5) In the present embodiment, a cold-rolled steel sheet is manufactured by a cold-rolled steel sheet manufacturing method including a cold-rolling step according to the steel sheet cold-rolling method described above.
According to this configuration, it is possible to more stably produce the desired cold-rolled steel sheet.

Next, examples based on this embodiment will be described.
FIG. 4 shows the target shape set according to the plate temperature in this embodiment. In FIG. 4, the center in the strip width direction is set as the origin position, the horizontal axis shows the strip width position, and the vertical axis shows the deviation in the strip width direction (I-unit value).
As shown in FIG. 4, in the present embodiment, when the plate temperature is 200° C. or higher, compared with the case where the plate temperature is lower than 200° C., the edge stretch shape (the direction in which the I-unit value increases) is increased. was set to , and rolling was performed. In the comparative example, the rolling was performed in a shape (flat shape) of less than 200° C. in FIG. 4 regardless of the plate temperature of the steel plate 10 to be rolled.

<Example 1>
In this example, in the pass (first pass) where the plate temperature of the steel plate 10 is 200 ° C., the steel plate made of each steel material having a Si content of 2.40 to 4.00% by mass is described in Table 1. , with the target shape (I-unit value) and control gain of the steel plate 10, respectively.
The target shape (I-unit value) of the steel plate 10 in the pass before the temperature of the steel plate 10 was raised to 200° C. was set to a flat shape (I-unit value=0). Moreover, the pass at which the plate temperature of the steel plate 10 to be rolled was 200° C. was the sixth pass. The I-unit values in the table are the I-unit values at both ends in the width direction. The I-unit value at the central portion in the width direction was set to "0".
Here, the breakage rate in Table 1 indicates the breakage occurrence rate under each rolling condition, and is the breakage rate when each example is performed 100 times.
In the table, the example with I-unit value=0 is a comparative example.

As can be seen from Table 1, in the steel plates 10 of each steel type, the target shape of the steel plate 10 when the plate temperature of the steel plate 10 is 200 ° C. is more elongated than the comparative example in which the I-unit value is 0. It was found that the breaking rate can be kept small by using a plate shape of
Furthermore, as can be seen from Table 1, even if the target shape of the steel plate 10 when the plate temperature of the steel plate 10 is 200 ° C. is set to a more edge-shaped plate shape based on the present invention, when the Si content of the steel type increases, Although there was a tendency for the breakage rate to increase, it was found that by performing gain adjustment and making adjustments so that the control gain becomes relatively large, the breakage rate can be suppressed as the control gain increases.

Here, as the steel sheet 10 to be rolled at high tension by the Sendzimir rolling mill 1, a steel type having a Si content of 2.40% by mass or more is suitable. However, as can be seen from Table 1, the higher the Si content, the easier it is to break during rolling. On the other hand, as can be seen from Table 1, by applying the present invention, it was found that the fracture rate in rolling with the Sendzimir rolling mill 1 can be suppressed to a small value, and stable rolling becomes possible. . Furthermore, it was found that the fracture rate can be suppressed to a low level by increasing the control gain as the Si content in the steel sheet 10 increases.

In Table 1, the reason why the breaking rate increases as the control gain decreases is that if the target shape is simply changed in the edge elongation direction, the sheet width end portion will be broken before the actuator 4 for shape control is controlled in the elongation direction. It is conceivable that it becomes a stretched shape. On the other hand, it is considered that by changing the gain value and increasing the control amount that produces an edge-stretched shape, the edge-stretched shape can be suppressed and stable rolling can be performed without breakage.
<Example 2>
The rolling conditions were the same as in Example 1, except that the temperature of the steel sheet 10 in the pass where the temperature exceeded 200°C was adjusted to 250°C.
The results are shown in Table 2.

The temperature of the steel sheet 10 was less than 200°C in the first pass (second pass) before the target pass in which the temperature of the steel plate 10 was 250°C. Moreover, the pass (first pass) in which the plate temperature of the steel plate 10 to be rolled was 200° C. was the sixth pass.
As can be seen from Tables 1 and 2, the higher the temperature of the steel sheet 10 rolled by the Sendzimir rolling mill 1, the more likely it is to break. At this time, as can be seen from Tables 1 and 2, even with the same steel type and the same target shape based on the present invention, the higher the plate temperature, the higher the control gain, thereby suppressing the fracture rate. I knew I could.

1 Sendzimir rolling mill 1a work roll 1b first intermediate roll 3 shape control unit 3A pass temperature determination unit 3B shape setting unit 3C shift control unit 4 actuator 10 steel plate 20 temperature sensor

Claims (7)

A cold rolling method in which a steel plate having an Si content of 2.40 to 4.00% by mass is cold rolled in multiple passes by a Sendzimir rolling mill,
Among the plurality of passes, the target shape of the steel plate in the first pass in which the temperature of the steel plate to be rolled is determined to be 200 ° C. or higher is changed to the target shape of the steel plate in the second pass in which the temperature of the steel plate to be rolled is determined to be less than 200 ° C. A method of cold rolling a steel sheet, characterized in that the steel sheet is set to an edge-elongated shape rather than the target shape of the steel sheet. A cold rolling method in which a steel plate having an Si content of 2.40 to 4.00% by mass is cold rolled in multiple passes by a Sendzimir rolling mill,
Among the plurality of passes, the I-unit value of both ends set as the target shape of the steel plate in the first pass in which the plate temperature of the steel plate to be rolled is determined to be 200 ° C. or higher is A method of cold rolling a steel sheet, characterized in that the I-unit value is set to a value that is 10 or more larger than the I-unit value of both ends set as the target shape of the steel sheet in the second pass determined to be less than 200°C. The steel plate according to claim 2, wherein as the target shape of the steel plate in the first pass, the I-unit value at both ends of the steel plate is set to a value that is 10 or more larger than the I-unit value at the center of the steel plate. cold rolling method. The Sendzimir rolling mill includes an intermediate roll shift mechanism for shifting the intermediate roll as a mechanism for controlling the shape of the steel sheet,
The control gain relating to the shift of the intermediate roll is set to a larger value when it is determined that the temperature of the steel sheet to be rolled is 200°C or higher than when it is determined that the temperature of the steel plate to be rolled is less than 200°C. A method for cold rolling a steel sheet according to any one of claims 1 to 3. 5. The method of cold rolling a steel sheet according to claim 4, wherein the control gain is set to a larger value as the amount of Si contained in the steel sheet to be rolled increases. 6. The method of cold rolling a steel sheet according to claim 4, wherein the control gain is set to a larger value as the temperature of the steel sheet to be rolled increases. A method for producing a cold-rolled steel sheet, comprising a cold-rolling step according to the steel sheet cold-rolling method according to any one of claims 1 to 6.

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