JPH11254012A - Method for controlling strip thickness at tip part of coil in hot finish-rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set-up of a coil under further stable condition and to improve the precision of strip thickness at the front tip part of the coil by inputting a setting value to the tension at the inlet side and zero to the tension at the outlet side as the set-up condition, calculating rolling ?toad and forward slip and setting the roll gap in each stand and peripheral speed of the roll. SOLUTION: The rolling condition in a learning point and the rolling condition at the front tip part of the coil, are distingushed, and in the learning point, the tension values at the inlet and the outlet sides in each stand are measured to learn the rolling load and the forward slip. To the set-up, the rolling load and the forward slip calculated with the setting value to the tension at the inlet side and zero to the tension at the outlet side, are used. In this way, the precision of the strip thickness at the front tip part of the coil can drastically be improved, and such trouble as folding and stretching of the strip at the time of passing through the strip for coil can be prevented because out of the setting value at the front tip part of the coil is small. Then, the product having good precision of the strip thickness can efficiently be produced in the good yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the thickness of a coil end portion in hot finish rolling, and more particularly to a setup for intermittently hot finishing rolling a coil by a continuous rolling mill having a plurality of stands. About the method.

[0002]

2. Description of the Related Art The thickness accuracy of a hot coil, particularly the thickness accuracy of a coil tip, largely depends on the initial setup accuracy of a finishing mill. In the improvement of the thickness accuracy over the entire length of the hot coil, the AGC (automatic thickness control) has been within the allowable range by the AGC (Automatic Thickness Control) in the center of rolling, so improving the thickness accuracy at the coil tip has become an important issue. ing.

[0003] The roll gap is set using a rolling load and a mill elongation formula. In order to improve the setting accuracy, it is general to carry out model learning. For example, as described in the detailed description of the invention of Japanese Patent Application Laid-Open No. 60-15010, a correction coefficient To make the calculated value match the actual value.

However, since the roll peripheral speed and the advance rate are used for estimating the sheet thickness between stands, the position to be learned must be a stationary part, and the position of the tip of the coil where the sheet thickness accuracy actually matters is considered. Was different.

In order to correct this difference, Japanese Patent Publication No. 3-1
As shown in 8965 and Tokuhei 3-151109,
Based on the load and plate thickness of the front stand at the time of passing the sheet (at the end of the coil), determine the roll gap of the stand (Japanese Patent Publication No.3-1896).
5) A dynamic correction, in which the roll gap of the next stand is reset (Japanese Patent Publication No. 3-151109) based on the load and plate thickness of the stand, has come to be performed.

Japanese Patent Application Laid-Open No. 64-75111 discloses that a friction coefficient is learned by applying a rolling torque and used for setup.

[0007]

However, the rolling situation at the time of threading (the most advanced part of the coil) is different from the rolling situation at the steady part where model learning is performed. Even if it is carried out, the accuracy of the thickness of the coil tip is not easily improved, and a large change in the roll gap also causes troubles such as double incorporation and pulling of the plate.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to improve the thickness accuracy of the coil tip by setting up the coil more stably at the position of the tip of the coil. I do.

[0009]

SUMMARY OF THE INVENTION According to the present invention, when a coil is intermittently hot-finished rolled by a continuous rolling mill having a plurality of stands, as shown in FIG. The input and output tension values are taken in to learn the rolling load and the advance rate, and for the coil setup, the input value is set as the input tension and the output tension is set as zero as the setup condition. The above problem is solved by calculating the roll gap and the roll peripheral speed of each stand by calculating the advance rate and the roll ratio.

As described above, the setup in the hot finish rolling is not set up under the tension condition of the steady portion, but is made to match the rolling condition at the time of threading.
It is possible to set up more stably at the position of the coil tip, and it is possible to improve the thickness accuracy of the coil tip.

Further, by starting the thickness control of the stand before the leading end of the rolled material bites into the next stand,
The present invention is intended to prevent a change in plate thickness (reduction in plate thickness) due to the occurrence of output side tension when the next stand is engaged and when the output side looper is raised.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In this embodiment, for example, as shown in FIG.
The present invention is applied to, for example, a 7-stand continuous hot finishing mill in which three stands 11 to 17 are provided, and loopers 21 to 28 and a tension meter 31 to 38 are arranged between the stands.

In this embodiment, a certain stand 10_n
FIG. 3 shows how the tension of the rolled material (coil) 8 changes. Ma
First, as shown in FIG.
0_nAnd then, as shown in FIG.
Paper 20_iUntil the start-up, the input tension is undefined
(Tension is zero when the board is doubled, and high when the board is pulled.
Tension), the output side tension becomes zero. In FIG. 4, 10
_n-1Is the front stand, 10 _{n + 1}Is the next stand.

[0015] Then, as shown in FIG. 3 (B), the launch of the entry side looper 20 _i, as shown in FIG. 3 (C),
Until the next stand 10 _{n + 1} is engaged, the entrance tension is the set value T and the exit tension is zero.

Further, as the rolling progresses, as shown in FIG. 3 (C), the rolled material 8 bites into the next stand 10 _{n + 1} , and then, as shown in FIG. Until the rise of 20 _° , the incoming tension is the set value T, and the outgoing tension is indefinite (zero tension in the state of double plate in the plate, high tension in the tension state).

[0017] Finally, as shown in FIG. 3 (D), the exit-side looper 20 _o rises, both inlet and outlet tension becomes the set value T.

The tip of the coil where thickness variation is a problem
Until the rolled material 8 bites into the next stand 10 _{n + 1} , during this time, as described with reference to FIGS. 3 and 4, the entrance tension is undefined or the set value, and the exit tension becomes zero. On the other hand, the learning is performed in the steady rolling region, and both the entrance and exit tensions are at the set value T.

In the conventional setup method, the coil tip is set up by the same setting calculation as the calculation at the time of learning without considering the difference between the rolling condition at the learning point and the rolling condition at the coil tip. For this reason, the plate thickness at the tip of the coil largely deviates from the target value.

On the other hand, according to the present invention, the rolling condition at the learning point and the rolling condition at the coil tip are distinguished from each other, and as shown in FIG. Calculate the load, learn the rolling load and advanced rate,
For the setup, the rolling load and the advanced ratio calculated when the entrance tension is a set value and the exit tension is zero are used. In this way, when setting up the coil tip, by setting the output side tension to zero instead of the set value, it is possible to match the passing state of the coil tip,
It is possible to increase the thickness accuracy from the leading edge of the coil.

However, there is a possibility that a change in the sheet thickness (a decrease in the sheet thickness) may occur due to the occurrence of the output side tension when the next stand is engaged and when the output side looper is raised. In order to suppress this, before the rolled material is bitten by the next stand and the rolled material is pulled, the thickness control is started at the stand, and the gap can be widened so as to compensate for the decrease in the thickness due to the occurrence of the output side tension. In this way, it is possible to suppress the thickness variation (reduction of the thickness) due to the occurrence of the output side tension by the AGC, and it is possible to maintain the high-accuracy setup effect at the coil tip.

[0022]

EXAMPLE A low-carbon steel having a finished plate thickness of 2.0 mm and a plate width of 1500 mm was set up by calculating the rolling load and the advance ratio by the following calculation method, and was finished on a 7-stand as shown in FIG. Rolling was performed by a rolling mill, and the accuracy of the thickness of the coil tip was compared.

The setting calculation method used is a case where the calculation is performed with no tension in both the learning calculation and the setting calculation (Comparative Example 1), and a case where the calculation is performed under the tension condition of the steady portion in both the learning calculation and the setting calculation (Comparative Example). 2) At the time of learning calculation, it is calculated using the actual value of the entrance and exit tension,
At the time of setting calculation, the input tension is set at the set value, and the output tension is calculated at zero (Method 1 of the present invention). At the time of learning calculation, the input and output tension is calculated using the actual value.
At the time of setting calculation, the input side tension is set at a set value, the output side tension is calculated as zero, and the automatic thickness control is started at the relevant stand before the next stand is engaged (the method 2 of the present invention). .

FIG. 5 shows how the thickness of the coil tip varies according to the four calculation methods. In both Comparative Examples 1 and 2, the rolling conditions at the time of learning calculation and at the time of setting calculation are not distinguished.
From the time when both the input and output tensions are zero, the input tension is the set value, and after the output tension is zero, both the input and output tensions become the set values. In accordance with this change, the sheet thickness is gradually reduced, and finally, the sheet thickness deviation becomes substantially zero. The entry and exit side tensions reach the set values only after the next stand has been engaged and the exit side looper has risen.
It will be overly thick. In addition, the thickness accuracy in the steady part is
Comparative Example 2 is better than Comparative Example 1 because the difference in the tension conditions is reflected in the setting calculation.

On the other hand, in the method 1 of the present invention, the input side tension is set to the set value and the output side tension is set to zero, and the set value is equal to the set value from the tip of the coil, so that the thickness deviation is almost zero. Also, when the entrance looper is started, the plate thickness hardly changes because the entrance tension has already been established. However, since the thickness reduction due to the generation of the output side tension due to the startup of the output side looper cannot be suppressed, the thickness is slightly too thin in the steady region.

On the other hand, in the method 2 of the present invention, in addition to the method 1 of the present invention, since the automatic thickness control is started before the next stand is engaged, the above-mentioned thickness reduction due to the occurrence of the output side tension is suppressed. As a result, a high thickness accuracy can be maintained in the range from the leading edge of the coil to the steady portion.

It should be noted that, in the above embodiment, the present invention
Although the present invention has been applied to the continuous hot finishing mill of the stand, the application of the present invention is not limited to this.

[0028]

According to the method of the present invention, it is possible to set up with high accuracy by setting calculation in consideration of the rolling state of the coil tip,
The thickness accuracy of the coil tip can be greatly improved. Also, since the deviation of the setting at the coil tip becomes small, it is possible to prevent troubles such as doubling and pulling of the plate when passing the coil,
It is possible to efficiently produce a product with a high thickness accuracy with good yield.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the gist of the present invention.

FIG. 2 is a diagram showing a configuration example of a seven-stand continuous hot finishing mill to which the present invention is applied.

FIG. 3 is a diagram for explaining the principle of the present invention, showing a tension variation state at the time of threading of a coil tip.

FIG. 4 is a view showing a rolling situation in each stage of FIG. 3;

FIG. 5 is a diagram showing a comparison of a sheet thickness variation state at a coil tip in a comparative example and an example of the present invention.

[Explanation of symbols]

8 ... rolled material (coil) 10 _n ... the stand 10 _{n + 1} ... next stand 10 _n-1 ... Previous stand 11-17 ... Stand 20 _i ... entry side looper 20 _o ... exit-side looper 21 to 26 ... looper 31 to 36 ... Tension meter

Claims (2)

[Claims] When a coil is intermittently hot-finished and rolled by a continuous rolling mill having a plurality of stands, a tension value on an entrance side and an exit side of each stand is taken in with respect to a front coil to learn a rolling load and an advanced ratio. At the same time, input the set value for the input tension and zero for the output tension for the coil setup, calculate the rolling load and advance ratio, and calculate the roll gap and roll circumference of each stand. A method for controlling a thickness of a coil end portion in hot finish rolling, wherein a speed is set. 2. The method for controlling the thickness of a coil end portion in hot finish rolling according to claim 1, wherein the thickness control of the stand is started before the end portion of the rolled material bites into the next stand. A method for controlling the thickness of a coil end portion in hot finish rolling.