JPH08192212A - Method for controlling sheet crown and shape - Google Patents

Abstract

PURPOSE: To secure the objective sheet crown and stabilize passing through by improving the calculational accuracy of a roll profile when work rolls which are not ground after using them at the previous time are reused. CONSTITUTION: In a method in which the profile in the axial direction of the work roll is calculated before rolling a metal plate and the controlled variable of a device for controlling a sheet crown and shape is set based on the calculated profile, at the time of changing the work rolls, the wear profile and thermal profile of the work rolls used up to this time or rolling result information for calculating them are stored. When the work rolls to be used from now on are not ground after using them at the previous time, the wear profile and thermal profile or the rolling result information for calculated them which are stored about the work rolls are called and the variation of thermal profile of the work rolls from the completion of use at the previous time to the start of reuse is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a plate crown and a shape when a work roll is reused without grinding.

[0002]

2. Description of the Related Art In plate rolling, it is necessary to appropriately set the control amounts of the plate crown and the shape control device before rolling in order to pass the rolled material tip in a stable shape and to secure a target plate crown. There is. For that purpose, a model system capable of accurately predicting the plate crown and shape is indispensable, and the models are roughly classified into elastic deformation calculation model of rolling mill, deformation characteristic calculation model of rolling material, and axial profile calculation model of work roll. It

Among them, the roll profile is calculated after every rolling of the rolled material based on the rolling performance data of the current material and the wear profile and the thermal profile calculated after the previous material rolling. It is common to calculate the profile and thermal profile. Therefore, if the rolls ground by replacing the work rolls are installed, it is necessary to initialize the wear profile and the thermal profile by the previous rolling or the rolling record information (hereinafter collectively referred to as profile information) for calculating these. There is. In the conventional rolling operation, since rolls are changed all at once at the end of the rolling cycle, the profile information of all stands was initialized at the same time.

However, in recent years, in the field of hot rolling, rolls made of a new material having a wear resistance several times that of conventional rolls (hereinafter referred to as high speed rolls) have been developed by roll makers and have been introduced into actual machines. As a result, in the past, the work rolls were changed all at once for every one-cycle rolling, whereas the high-speed roll stand enables rolling for several cycles without changing the rolls, and multiple high-speed rolls can be used for high-speed rolls. Even if the rolls are worn or rough even if they are in use, by exchanging only the rolls on the stand that exceed the standard, the roll grinding work is significantly improved in efficiency.

On the other hand, since the high-speed roll is higher in cost than the conventional roll, if sudden roll grinding is performed due to rolling trouble such as drawing, the unit consumption of the roll is remarkably reduced even if the grinding amount is the same as that of the conventional roll. Therefore, under the present circumstances, it is unavoidable to use a conventional roll for the final stand, which often requires roll replacement and grinding due to drawing or the like, and to replace it every rolling cycle.

As described above, recently, the timing of exchanging the work rolls differs depending on the stand due to the introduction of the high-speed roll, and the method of initializing the profile information at the end of the rolling cycle cannot be dealt with. At the time of exchange, the profile information is initialized.

[0007]

However, in the operation of the high speed roll, for example, referring to the contents of the next rolling cycle, if necessary, the roll is temporarily removed without grinding and the other roll is waited for. It is also possible to use it by rolling it after incorporating it and reusing it. Further, even in cold rolling work, a roll that has been used once may be reused without being ground in order to improve the basic unit of roll.

In the prior art, profile information of each stand is initialized with the replacement of the work rolls even when the rolls that have not been ground after the previous use are reused as described above. Therefore, the roll profile calculation at the time of restart of rolling is performed. The value will be very different from the actual value. As a result, it is not possible to set an appropriate control amount for the plate crown and the shape control device,
There is a problem that the target plate crown cannot be obtained, or the plate passing property is deteriorated due to a defective shape to cause rolling trouble such as misrolling and drawing.

The present invention is intended to solve such a problem, and secures a target plate crown by improving the roll profile calculation accuracy when a work roll that has not been ground after the previous use is reused. An object of the present invention is to provide a plate crown and a shape control method capable of stabilizing a threaded plate.

[0010]

In order to achieve the above object, the present invention takes the following technical means. That is, the present invention calculates the axial profile of the work roll prior to rolling of the plate material, and in the method of setting the control amounts of the plate crown and the shape control device based on the calculated profile, when replacing the work roll. , It stores the profile information of the work roll used so far, and recalls the profile information stored for the work roll if the work roll to be used from now on has not been ground after the last use, and It is characterized by calculating the change in the thermal profile from the end of use to the start of reuse.

[0011]

In the present invention, when the work roll that has not been ground after the previous use is reused, the final profile information at the time of the last use is called and the thermal profile from the end of the last use to the start of the reuse is called. Is calculated, the roll profile can be accurately predicted from the first rolled material at the time of reuse.

[0012]

EXAMPLES Specific examples of the present invention will be described below.
FIG. 1 is a view showing the arrangement of rolling mills and work rolls of a hot strip mill embodying the present invention, in which the first to third stands are ordinary four-high rolling mills, and the fourth to seventh stands are work rolls. This is a four-high rolling mill that moves in the axial direction.
A work roll bending device is arranged on each of the third to seventh stands. 10 is a rolled material.

In this embodiment, first, as shown in FIG. 1 (a), in the first cycle, all the first to seventh stands were assembled with ground work rolls for rolling. Of these, the first to third stands are conventional high chrome rolls, the fourth to sixth stands are high speed rolls, and the seventh stand is a conventional Ni grain roll. Since the second cycle was a special rolling cycle, the work rolls of all stands were replaced. However, the high-speed rolls of the fourth to sixth stands were not ground but kept in standby.

Since the third cycle was a normal rolling cycle, after completion of rolling in the second cycle, as shown in FIG.
As shown in (1), the ground conventional rolls were installed in the first to third stands and the seventh stand, and the high speed steel rolls that had been on standby were installed in the fourth to sixth stands for rolling. Note that, in FIG. 1, the hatched work rolls are reuse rolls.

Since the HSS roll has the characteristics of large thermal expansion and small wear, the roll profile at the end of the first cycle rolling has a convex shape larger than that after grinding, and even when air-cooled during standby. At the start of rolling in the third cycle, a considerably large convex roll profile remains. However, in the conventional method, the profile information is initialized when the rolls are exchanged after the completion of the first and second cycles, so that the convex shape due to the profile calculation of the fourth to sixth stands is generated in the third cycle, especially at the beginning of the rolling cycle. Much smaller than it really is. For this reason, the set value of the work roll bending amount became unnecessarily large, and a middle stretched shape was generated during the passage of several rolled materials after the start of the third cycle rolling.

FIG. 2 shows the transition of the difference between the calculated value and the actual value of the plate crown at the beginning of the first and third rolling cycles according to the conventional method. In the third cycle, the actual value is different from the calculated value. Is about 20 μm smaller. Although the error of the calculated value of the plate crown is gradually reduced by performing learning, about 10 rolling is required to absorb the error with the normal learning gain, and during this period, the plate crown is larger than the target value. It may be smaller than necessary.

On the other hand, in the method of the present invention, the 4th to 4th stored when the rolls are replaced after the completion of the first cycle rolling.
The profile information of the 6th stand is called at the time of roll exchange after the completion of the second cycle rolling, and the change in the thermal profile from the end of the first cycle rolling to the start of the third cycle rolling is calculated, and the first cycle of the third cycle is calculated. The bending amount for the actual rolled material is set. Therefore, it was possible to pass the plate from the first in a substantially flat shape, and it was possible to secure the target value for the plate crown.

A method of processing profile information when exchanging work rolls according to the present invention will be described below with reference to the flow chart shown in FIG. In step 1, the area in which the profile information about the roll used this time is stored is searched by using the roll number unique to each roll as a keyword, and if there is a corresponding one, the current information is overwritten and stored in step 2. If there is no profile information stored in the newly used roll for the roll used this time, the roll number and the current profile information are stored in the empty area in step 3.

Next, in step 4, the profile for the roll to be used next time is searched in the same manner as in step 1, and if there is a corresponding one, it is determined in step 5 whether or not the roll to be used next is ground, and it is ground. If it is not reused, the profile information stored in step 6 is called. If the next roll to be used does not have the profile information stored in the new roll, or if the next roll to be used has undergone grinding, the profile information is initialized.

Here, to determine whether or not the next roll to be used has been ground, the ground flag in the storage area is referred to. The ground flag is set when each roll is ground, and reset when the profile information is stored in step 2 or step 3. In the present embodiment, in order to save the storage area of the profile information, as a process before step 1, it is judged whether the roll used this time is a high speed roll, and if it is a conventional roll, it is not reused. On the assumption that the profile information is not stored, the profile information may not be stored.

Next, the method of calculating the roll profile in this embodiment will be described. Basically, the wear profile and the thermal profile of the work roll are calculated, and the sum of these is used as the roll profile. First, the method of calculating the wear profile will be described. The amount of wear Wc at the central portion of the strip width is expressed as the following equation (1) as a function of the rolling pressure, the number of contacts between the strip and the work roll, and the sliding distance due to the advance of the strip in the roll bite.

[0022]

[Equation 1]

Here, P is a rolling load, B is a plate width, 1d is a contact arc length, L is a rolling length, Dw is a work roll diameter, f is an advance rate, and k, α, and β are constants. The wear profile W (X) of the work roll is the profile function w obtained from the result of the continuous rolling experiment of the same width material as the wear amount Wc of the central portion of the strip width.
It is obtained by calculating the amount of wear at each position in the roll axial direction by the product of (X) and superposing this on each rolling.

Therefore, the wear profile Wn (X) at the start of the n-th rolling is expressed by the following equation (2). FIG. 4 shows a comparison result between the calculated value and the actually measured value by the equation (2). As shown in FIG. 4, it can be seen that the calculated value by the equation (2) agrees well with the measured value.

[0025]

[Equation 2]

As can be seen from the constitution of the equation (2), the wear profile can be obtained by superposing the wear profile for one material this time on the cumulative value up to the previous material.
Only the final wear profile needs to be stored when the roll is replaced. Next, as a method of calculating the thermal profile, at each calculation timing, the temperature distribution at the time of this calculation is calculated based on the temperature distribution inside the work roll at the time of the previous calculation, and the thermal profile is calculated from the temperature distribution. is there. In this embodiment, the most basic two-dimensional difference method is used. The calculation method is also described in “Theory and Practice of Sheet Rolling” edited by the Iron and Steel Institute of Japan, pages 141 to 143, which will be briefly described below.

The heat conduction equation considering the temperature changes in the radial direction and the axial direction of the roll is expressed by the following expression (3).

[0028]

(Equation 3)

Here, α = λ / (ρ · c), T is roll temperature, t is time, λ is thermal conductivity of roll, ρ is density of roll, c is specific heat of roll, and r is radius. Direction coordinates,
x is a coordinate in the roll axis direction. Here, when the expression (3) is displayed as a difference, it becomes the following expression (4).

[0030]

[Equation 4]

The temperature T _{k + 1} at each position inside the roll at t = t _{k + 1} is obtained by solving these simultaneous linear equations with the temperature T _k at each part of t = t _{k being} a known value. Desired. The boundary conditions are given in the same manner as the equation (4), with the heat transfer coefficient at each position on the roll surface during rolling and cooling, the heat flux from the material during rolling, and the ambient temperature being known.

If the temperature distribution is obtained, the thermal expansion of the roll in the plane strain state is expressed by the following equation (5).

[0033]

(Equation 5)

Here, γ is a linear expansion coefficient, and R is a roll radius. The minimum value of U (X) in the axial direction is called a parallel expansion amount, which is U when the position of the minimum value is X _0.
It is represented by (X ₀ ). X ₀ is usually the roll barrel end, but particularly in the case of a rolling mill that moves the roll in the axial direction, it is the barrel barrel end on the side where the distance to the plate is long. The thermal profile is expressed as the difference between U (X) and U (X ₀ ).

If such a method is adopted, the final temperature distribution may be the only information stored for calculating the thermal profile during reuse. As the sum of the wear profile and the thermal profile calculated as above,
The roll profile is calculated. Further, as another thermal profile calculation method, there is also a method of using a two-dimensional simple model considering the temperature distributions in the work roll radial direction and the axial direction.

This is because the average temperature rise in the radial direction θm obtained from the approximate solution of the heat conduction equation in the radial direction at the central portion of the strip width for each rolled material and the profile function V (obtained from the heat conduction equation in the axial direction) X) is used to calculate the average amount of temperature increase in the radial direction at each position in the axial direction, and this is overlapped each time rolling is performed, as shown in FIG. The thermal expansion Un (X) at the start of the n-th rolling is expressed by the following equation (6).

[0037]

(Equation 6)

FIG. 6 shows a comparison result between the calculated value and the measured value of the thermal profile using the equation (6). As shown in FIG. 6, it can be seen that the calculated value by the equation (6) is in good agreement with the measured value. However, in this method, since Vi (X), θmi in the equation (6) is a function of time, it is necessary to recalculate using data of all rolled materials that have been rolled in the past with the passage of time. Therefore, in order to calculate the thermal profile during reuse, the strip width of each rolled material,
It is necessary to memorize for each roll information such as the leading edge biting time, the trailing edge trailing edge time, the actual value of the work roll movement amount in the work roll moving type rolling mill, and the heat flux calculation value from the rolled material to the roll. There is.

Although this embodiment has been described with reference to the case of hot finish rolling, it goes without saying that it can be similarly applied to the case of cold tandem rolling.

[0040]

As described above in detail, according to the plate crown and the shape control method of the present invention, when the work roll which has not been ground after the previous use is reused, when the roll is used. Since the latest profile information of the work roll is called and the change in the thermal profile from the end of the previous use of the work roll to the start of reuse is calculated, the roll profile from the first rolled material at the time of reuse can be accurately measured. Can be predicted, and an appropriate control amount can be set for the plate crown and the shape control device. As a result, the target plate crown can be secured and the plate passing can be stabilized.

[Brief description of drawings]

FIG. 1 is a view showing an arrangement of rolling mills and work rolls of a hot strip mill embodying the present invention.

FIG. 2 is a graph showing the transition of the difference between the calculated value and the actual value of the plate crown by the conventional method.

FIG. 3 is a graph showing a method of processing profile information when exchanging work rolls according to the present invention.

FIG. 4 is a graph showing a comparison between a calculated wear profile of a work roll and an actually measured value.

FIG. 5 is a graph showing thermal expansion at the start of the n-th rolling.

FIG. 6 is a graph showing a comparison between a calculated value and a measured value of a thermal profile of a work roll.

[Explanation of symbols]

 1-3 Conventional 4-high rolling mill of hot strip mill 4-7 Working roll moving 4-high rolling machine 8 Conventional work roll of hot-strip mill 9 High speed roll 10 Rolled material

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location B21C 51/00 N 8315-4E B21B 37/00 116 M (72) Inventor Hiroyuki Hasegawa Kakogawa City, Hyogo Prefecture Kanazawa 1st Kamigawa Steel Works Kakogawa Works

Claims (1)

[Claims] 1. A method of calculating an axial profile of a work roll prior to rolling of a plate material and setting a control amount of a plate crown and a shape control device based on the calculated profile, when replacing the work roll, The wear profile and thermal profile of the work roll used so far or the rolling record information for calculating these are stored, and if the work roll to be used from now on is not ground after the previous use, it is stored for the work roll. Wear profile and thermal profile or rolling performance information for calculating these, and calculate the change in thermal profile from the end of the last use of the work roll to the start of reuse, Shape control method.