JPS6116201B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rolling method in which the center of the width of a rolled material is intentionally shifted from the center of the work rolls to the work side or drive side.

Conventionally, in plate rolling, due to changes in the working roll profile mainly due to wear, there was a plate width regulation in the rolling schedule that meant that once a narrow material had been rolled beyond a certain level, a wide material could no longer be rolled. Regulations not only complicate process control, but especially in the case of hot rolling, they pose a major obstacle to the introduction of energy-saving technologies such as direct rolling and hot-piece charging. Therefore, as a method to eliminate such plate width restrictions, methods have been proposed such as shifting the work rolls in the axial direction or rolling the rolled material by intentionally shifting it from the mill center, but in reality, such rolling The question of what kind of wear profile to aim for and how to calculate the distance between the center of the rolled material and the center of the work roll, that is, the amount of off-center, remains largely unresolved. .

Regarding this point, in JP-A-53-68662, an invention has been made in which the amount of off-center is determined so that the wear amount of the work roll is uniform over the length direction of the body, but this invention has the following problems. was left behind. First, in order to obtain a uniform amount of wear in the lengthwise direction of the body, extreme rolling must be carried out so that the rolled material does not come into contact with the center of the body length of the work roll. This is because if all the rolled material is in contact with the center of the body length of the work roll, roll wear from all rolling will steadily accumulate at the center of the body length, while other parts Since there may be no contact with the material, wear does not progress as much, and as a result, off-center rolling (here, work roll shift rolling and rolling in which the center of the width of the rolled material is intentionally shifted from the mill center) is called off-center rolling. Even if you perform rolling (hereinafter collectively referred to as rolling),
This is because the amount of wear will not be made uniform in the lengthwise direction of the barrel. However, such extreme off-center rolling poses great difficulties in terms of sheet threadability, and the basic premise is that such rolling can only be carried out on narrow materials that are less than half of the maximum rollable width. As a result, productivity improvement due to double-width rolling cannot be expected. Furthermore, this method has the problem that the sheet passing position must be controlled with very high precision. This is because when off-center rolling of a narrow width material is performed so as not to contact the center of the body length of the work roll, one plate end of the rolled material still passes near the center of the body length of the work roll. The wear profile becomes discontinuous there.
In order to eliminate such discontinuous parts, it is necessary to perform rolling by aligning the edge of the other plate of the material to be rolled exactly with the edge of the previously rolled material. It is. If such highly accurate control of the sheet passing position is not possible, discontinuous portions of the wear profile will gradually increase, and abnormal profiles such as high spots will occur in the rolled material.

The above points will be explained using FIG. In the figure, a case is considered in which a large amount of material having the same width as the plate width b is rolled using work rolls having an effective body length.

First, as shown in FIG. 5a, it is assumed that the sheet end is aligned with the effective body end of the DS and rolled. When considering the rolling position of the next material, in order to minimize the difference between the maximum amount of wear and the minimum amount of wear, it is necessary to roll the next material in the unrolled area as shown in figure b. As a result, a roll profile as shown in figure c is obtained, and when this process is repeated and a large amount of rolling is performed, a roll profile as shown in figure d is obtained.

For reference, Figure e shows the roll profile when rolling is performed without off-center rolling. Comparing diagrams d and e, △Rmax−△Rmin
The value in the case of figure d is 1/2 of that in figure e, but when a large step appears in parts A and B of figure d and a material with a width of more than b' is rolled. , these steps are printed on the rolled material and cause problems. Further, protrusions as shown in the figure remain on the body end portions C and D, causing problems of spalling and breakage at these portions. In order to eliminate the latter problem, it would be possible to make the entire body the effective length, but this is not realistically possible due to the risk of the plate ends protruding. Furthermore, since the edge of the plate repeatedly passes through the same location on the roll, localized wear as shown by the broken line in the figure also appears.

As mentioned above, it is concluded that the logic of JP-A-68662, which minimizes △Rmax - △min, does not improve the conventional method (method that does not take off-center) in this case, but rather worsens the problem. I have no choice but to do it.

The present invention advantageously solves the drawbacks of these conventional methods, and an object of the present invention is to achieve a relatively small off-center amount such that the length centers of the rolled material and the work roll are in contact with each other, and to improve the conventional rolling schedule. Our goal is to provide a rolling method that eliminates strip width restrictions.
The gist of the present invention is to aim for the wear profile of the work roll to become a smooth curve close to a parabola in rolling a metal plate, and to set the wear profile of the work roll determined from the target profile and the past rolling history, and the wear profile of the work roll to be rolled from now on. Calculate the off-center amount of the rolled material from the plate width of the material and the estimated wear amount, and set the distance between the center of the plate width of the rolled material and the body length center of the work roll to the off-center amount. This rolling method is characterized by rolling the rolled material.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the roll wear profile that occurs in conventional hot rolling in which the strip width center is aligned with the roll center. 1 shows the initial roll profile, and 2 shows the roll profile after rolling. As can be seen from wear profile 2, step-like wear occurs for each plate width, and it is natural that an abnormal profile will occur in the rolled material when a wide material as shown in b is rolled in this state. . In addition, the part 3 in the figure is the trace of the plate edge after rolling the same width of material together, but such plate edges are high due to low material temperature and stress concentration. Contact stress occurs and localized significant wear occurs. Therefore, in the case of conventional rolling, the restriction that a large amount of material of the same width cannot be rolled must be observed.

On the other hand, Figure 2 shows that when rolling n rolls of the same width while allowing an off-center amount of up to 80 mm, the off-center amount is changed by 80/(n-1) each time one roll is rolled. The wear profile after this was determined by simulation. As a result, local wear at the edge of the plate has been significantly reduced, and it can be seen that the limitation on the number of rolled pieces of material of the same width can be greatly improved by such a simple method. However, even in wear profile 2 in Fig. 2, if a wide material as indicated by b is rolled, there is a strong possibility that part 3 will remain as an abnormal profile, and the wear profile from 3 to the end of the body is as shown in Fig. 2. However, if the plate width schedule differs, the off-center amount calculation method described above does not necessarily result in a smooth result.

Therefore, these problems are solved as follows.
First, determine the target wear profile. The most ideal target profile is a parabola or cosine function profile. This is because, as mentioned above, it is assumed that the amount of wear at the center of the roll body will hardly change even if off-center rolling is performed. There is a general tendency for the section to be the largest and the body end to be the smallest, and the parabola or cosine function shape satisfies these conditions and has the least negative effect on the plate thickness distribution. . Furthermore, rolling mills that have been developed in recent years and have a large crown shape control ability all have the ability to change the roll gap shape in a pattern close to a parabola, and if the wear profile is close to a parabola, the influence of the roll wear profile can be reduced. This can be compensated for by the ability to control the crown shape. As described above, the most ideal wear profile is a parabolic shape, but in reality, due to the limit of the off-center amount and the plate width schedule, the wear profile becomes almost trapezoidal as shown in Figure 2, where the center of the body length is flat. It is thought that there may be cases. As long as the overall amount of wear is relatively small, it is considered that a trapezoidal profile is close to a parabolic shape and poses no problem, and in this sense, the target profile may be set to be close to a trapezoid.

Next, a method for actually obtaining the off-center amount will be described. The target profile is a parabola, and the amount of off-center is determined assuming that the amount of wear caused by one rolled material is uniform in the width direction. This is because, as shown in FIG. 2, local wear at the edge of the plate is hardly a problem unless the edge of the plate passes through the same position, and it is considered that it can be ignored in terms of the amount of wear as a whole. Before calculating the amount of off-center, the target profile must first be determined.
This is done by realizing the total wear amount (indicated by roll radius or diameter) due to rolling of all the materials whose off-center amount is to be determined, at the center of the body length, and calculating the total wear area (the area surrounded by the target profile and the initial profile). ) is selected from among those that satisfy the condition that ΔA is the sum of (amount of wear) x (plate width) of all materials. In the case of a parabolic profile, it is completely and uniquely determined by the above two conditions, and the target profile is where y is the wear amount and x is the width direction coordinate with the center of the roll body length as the origin. y=-ax ² +ΔR...(1 ) However, it is expressed by the formula a=16/9 (ΔR) ³ /(ΔA) ² . In this equation, if y=0, the range x _R where roll wear occurs can be found as x _R = 3/4 ΔA/ΔR (2). xR is 1/2 of the effective torso length of the work roll
If it is larger, it is inappropriate as a target profile, so the procedure for obtaining the above target profile is repeated by excluding the one with the maximum strip width from among the rolling schedules. It is considered that the removed material in this case should be brought to the beginning of the schedule and rolled without off-center, or incorporated into another rolling schedule.

After the target profile is determined, the passing position, that is, the off-center amount of each rolled material may be determined by the method shown in FIG. 3 or 4. Figure 3 shows a method for determining the position from the body end of the target profile 4. First, the passing position of the first material (plate width b ₁ ) is determined by y = 1/, where the amount of wear is ΔR ₁ . The intersection point A between 2ΔR ₁ and the drive side (DS) target profile 4 is determined as the DS plate end position. Next, for the second material (plate width b ₂ ), the intersection of y=1/2 ΔR ₂ and the target profile of the work side (WS) is determined as the WS plate end position. The wear profiles caused by rolling these two materials are 5 and 6, respectively, and the third material (plate width b ₃ )
These profiles 5 are used when determining the threading position of
From the wear history of 6 and 6, target profile 4 is
It is determined which of WS and DS has been determined to a greater amount of wear (in this case, the relationship between ΔR ₁ and ΔR ₂ ), and the threading position is determined based on the target profile with the smaller amount of wear. In the case of Fig. 3, since ΔR ₁ <ΔR ₂ , the target profile of DS and y
The intersection point C of =ΔR ₁ +1/2ΔR ₃ is the position of the DS plate end of the third material. Note that 7 indicates wear caused by the third material. For the fourth and subsequent runs, repeating the same procedure as for the third run will determine the threading positions of all materials, that is, the amount of off-center.

In contrast to FIG. 3, FIG. 4 shows how to determine the threading position from the center of the body of the target profile. First, for the first rolled material, y
= ΔR - 1/2 ΔR The intersection point A between ₁ and the target profile of the DS is set as the board end position of the DS, and the first threading position is determined. The second one determines the intersection B between y=ΔR-1/2ΔR ₂ and the target profile of the WS as the plate edge position of the WS. For the third and subsequent shots, set the target profile.
Determine which of WS and DS has been determined to have a greater amount of wear, and determine the sheet passing position based on the target profile with the smaller amount of wear. In the case of the third one, since ΔR ₁ <ΔR ₂ , the strip passing position can be determined by using the intersection C of the target profile of the DS and y=ΔR−ΔR ₁ −1/2ΔR ₃ as the DS plate end position. By repeating the same procedure as for the third piece for the fourth and subsequent pieces, the threading positions of all materials, that is, the amount of off-center, are determined.

In addition, in Figures 3 and 4, the threading position of the first material was determined based on the target profile of the DS.
This can't be helped even in WS.

Next, a method of selecting a set of rolled materials (herein referred to as a group) to determine the target profile will be explained. The largest group is 1
A complete rolling unit rolling with a set of work rolls is considered. In this case, a wear profile that is quite close to the target profile will be achieved when all of the material in one rolling unit has been rolled;
The wear profile in the middle of the rolling unit cannot be guaranteed. In this sense, it is desirable to divide one rolling unit into several groups and define a target profile for each group. The most ideal group is that no matter how the rolling order and off-center amount within each group changes, abnormal profiles will occur in any rolled material within the group due to wear due to rolling within the group. Moreover, it is considered to be the group with the largest number of rolling rolls. When divided into several groups like this, it is considered best to alternately adopt the methods shown in FIGS. 3 and 4 for each group.

Generally, the amount of off-center is often subject to restrictions from the aspects of equipment and operation, and in this sense, the smaller the amount of off-center, the better. In order to realize the target profile by minimizing the off-center amount with emphasis on this point of view, the following may be performed. First, the rolled materials in each group are arranged in order of sheet width, ignoring the actual rolling order. When determining the amount of off-center from the body end of the target profile as shown in Figure 3, determine the off-center amount in order from the board with the largest width.
When determining the off-center amount from the center of the target profile as shown in the figure, it is sufficient to adopt a method of determining the off-center amount in order from the smallest board width.

If off-center rolling is performed using the above method, the roll wear profile will change in a nearly parabolic shape, the occurrence of abnormal profiles can be prevented, and the strip width restrictions on the rolling schedule will be significantly relaxed, or It will be possible to abolish it. Further, there is a problem that the plate crown shape fluctuates as wear progresses, but this can be dealt with by effectively utilizing the crown shape control ability of the rolling mill.

Further, in the above description, only the wear of the work roll has been considered, but the present invention can also be applied to cases where the profile change due to thermal expansion of the work roll, that is, the contribution of thermal crown is large. This is because, although there is a difference in that the roll radius increases in the case of thermal crowns and decreases in the case of roll wear, the radius increases approximately uniformly across the width of the rolled material in the case of thermal crowns as well. This is because if off-center rolling is performed using the method of the present invention, it is estimated that the roll profile will be a smooth curve similar to the target wear profile.

[Brief explanation of the drawing]

Figure 1 shows the working roll profile after normal rolling with no off-center amount, and Figure 2 shows the work roll profile rolled at equal intervals for the same strip width when the off-center amount is allowed from 0 to 80 mm. The working roll profile after rolling the same rolled material as shown in FIG. 1 by changing the center amount, and FIGS. 3 and 4 are diagrams showing a method of determining the off-center amount of each material. In FIG. 5, a to e are diagrams for explaining problems in the prior art. 1... Initial roll profile, 2... Roll profile after rolling, 3... Roll profile at the plate end threading section, 4... Target wear profile, 5... Wear due to the first material, 6... Wear due to the second material , 7...Abrasion caused by the third material.

Claims (1)

[Claims] 1. In the rolling of metal plates, the wear profile of the work roll estimated from the past rolling history and the estimated values of the plate width and wear amount of a plurality of rolled materials to be rolled from now on are calculated. The target profile of the work roll at the end of rolling is uniquely determined as a smooth curve close to a parabola, and from this target profile and the plate width and wear estimate of the material group to be rolled from these, each Rolling characterized by calculating the off-center amount of the material, setting the distance between the center of the plate width of the rolled material and the body length center of the work roll to the off-center amount, and rolling the rolled material. Method. 2 Divide a group of rolled materials to be rolled with a set of work rolls without changing the rolls into several groups, set a smooth target profile close to a parabola for the wear profile of the work rolls for each group, The amount of off-center of the rolled material is calculated from the wear profile of the work roll determined from the target profile and the rolling history in the group, and the estimated value of the plate width and wear amount of the material to be rolled, and based on the results. A rolling method according to claim 1, wherein the rolling method is performed based on the rolling method. 3 At the stage of calculating the amount of off-center, the rolled materials in each group are arranged in order of strip width, and the amount of off-center is determined in order of strip width, such that the body end of the target wear profile is determined by the width of the wide material. The rolling method according to claim 2, wherein the rolling method is performed based on the calculation result.