JPH02179308A - Method for controlling sheet crown during hot rolling - Google Patents

Abstract

PURPOSE:To improve the production efficiency of hot rolling and to reduce the required number of work rolls by maintaining a drafting condition obtaining a target sheet crown by adjusting a combination of a shift amount of work rolls and a bending force by a work roll bender. CONSTITUTION:Both a sheet crown controlling mechanism reversely shifting bottle-shaped upper and lower work rolls 3, 3 and a hot rolling mill provided with a work roll bender 5 are used. The rolls 3, 3 are reversely shifted to each other in the axial direction by a prescribed amount from shifted positions in the rolling for a preceding stock. A drafting condition to obtain a target crown is maintained by adjusting a combination of a shift amount of the rolls 3, 3 and a bending force by the bender 5. Thus, sheet crown controlling ability is improved at low equipment cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling the crown of a sheet during hot rolling. The present invention relates to a method for controlling a plate crown during hot rolling by shifting the plate crown.

(Prior Art) In recent years, temporary crown/shape control has become very important due to the need for higher dimensional accuracy and higher quality of products in hot rolling. On the other hand, from an operational perspective, there is a trend toward schedule-free production in order to achieve short delivery times and high efficiency. To achieve these objectives, a hot rolling mill with large plate crown control capabilities is required, and new rolling mills with a number of temporary crown and shape control functions have been developed.

For example, as shown in FIG.
The intermediate roll 2 of the 6-type rolling mill consisting of an intermediate roll 2 and a work roll 3 is shifted in the direction shown by the black arrow in the figure according to the width of the rolled material 4, and the work roll bender shown by the white arrow in the figure A so-called IC mill that controls the plate crown by adjusting the pending force of There are so-called pair-cross (PC) mills that control the plate crown by crossing the direction, but these rolling mills are not only expensive, but also require a long modification period when modifying an existing rolling mill, making it difficult to manufacture products. It may cause problems, or it may not be possible to modify the existing equipment due to dimensional constraints.

On the other hand, methods that have low equipment costs, can be easily modified, and have a large temporary crown control capability are disclosed in Japanese Patent Application Laid-Open No. 57-91807, Japanese Patent Application Laid-Open No. 63-20106, Japanese Patent Application Laid-Open No. 63- There is a method of controlling the plate crown of a rolled material by relatively moving upper and lower bottle-shaped work rolls in the axial direction, as disclosed in Japanese Patent No. 84713 (
(hereinafter referred to as the CVC method).

As shown in FIG. 3, according to the CVC method, the work roll 3 has a bottle-shaped cross section, and the upper and lower work rolls are arranged so that their roll gap profiles are point symmetrical. Identical members in FIGS. 1 and 2 are designated by the same reference numerals.

When applying the CVC method, the only modification of existing equipment required is the work roll shift device, and if the bottle shape of the work roll is selected appropriately, the plate crown control ability will be greater than that of the aforementioned IC mill and PC mill. It has been known.

Regarding the plate crown control method using the CVC method, Figure 4 (
This will be explained using a), b), and (C). When the upper and lower rolls are not shifted and placed in the neutral position as shown in Figure 4 (al), the gap profile in the width direction is constant;
Rolling is similar to rolling with flat rolls without crowns. On the other hand, in this figure, the upper roll is moved to the right.
When the lower roll is shifted to the left, the gap profile becomes narrower at the center of the sheet width and wider at the ends of the sheet width, as shown in Figure 4 (°C), and the crown of the sheet becomes narrower, similar to when rolling with a top and bottom convex crown roll. becomes smaller. Conversely, if the upper roll is shifted to the left and the lower roll is shifted to the right, as shown in Fig. 4 (C
), the gap profile is wide at the center of the sheet width, narrow at the ends of the sheet width, and the sheet crown becomes large, similar to when rolling with upper and lower concave crown rolls.

In this plate crown control method using a work roll with a bottle-shaped profile, if the bottle shape imparted to the work roll is appropriately selected, a very large plate crown control capability proportional to the amount of shift can be obtained, resulting in an effective This is considered to be a temporary crown control means.

(Problems to be Solved by the Invention) However, the CVC method has the following problems and has not been considered as an effective means for controlling plate crown and shape.

In finishing rolling of normal hot rolling that does not use the CVC method, after changing the work rolls, it takes 2 hours before the next work roll change.
Approximately 0.00 rolled materials (total weight: 2000 tons) are rolled with the same work roll, but the work roll wears out and thermally expands due to contact between the work roll and the rolled material, so as the number of rolled materials increases, the work roll The profile changes every moment.

In particular, a sudden change in work roll profile occurs at the boundary between the contact area and the non-contact area, which adversely affects the rolled material profile. For this reason, at present, the work rolls are shifted by a certain amount every time one rolled material is rolled to disperse work roll wear and thermal expansion, and as the number of rolled materials increases,
By rolling with a rolling schedule that narrows the sheet width, the adverse effects of work roll profile changes on the rolled material profile are eliminated.

However, since the CVC method is a rolling method that uses the bottle shape profile of the work roll to shift the work roll to change the gap profile and perform temporary crown/shape control, the change in the work roll profile is This causes a large disturbance to the temporary crown shape control. The CVC method is used after rolling! ! The shift position must be determined so that it becomes a temporary crown, and of course it is not only impossible to shift for wear and thermal expansion dispersion, but also
Even if rolling is performed using a rolling schedule that narrows the strip width as the number of rolls increases, depending on the rolling conditions such as the output target strip crown and the rolling load, it is fatal that rolling must be performed at the work roll section where the profile changes suddenly. There are certain shortcomings.

In fact, when the conventional CVC method is applied to a hot rolling finishing mill, the bottle shape profile of the work roll is maintained immediately after the roll is changed, and although the temporary crown shape control effect is oscillated, the number of rolling rolls increases. Just before changing the roll,
In some cases, the effect of controlling the plate crown shape is completely lost, or under adverse conditions, even if the temporary crown is shifted in the direction of becoming smaller immediately after the roll change, the temporary crown ends up becoming larger. Furthermore, due to local wear of the rolls, sudden changes in the temporary profile may occur, such as locally thickening of the plate thickness at the edge portions of the plate. Therefore, unless a rolling method is developed that can maintain the bottle shape profile even when the number of rolls increases, it may be impossible to apply the CVC method to an actual rolling mill.

The purpose of the present invention is to provide a temporary crown that is stable from roll change to the next roll change, that allows for shape control, and that can also prevent work roll wear and thermal expansion dispersion in the CVC method in order to prevent the occurrence of abnormal machine profiles. An object of the present invention is to provide a shape control method.

(Means for solving the problem) In normal hot rolling using conventional flat rolls or work rolls with a quadratic curve profile, the following steps are taken to prevent the adverse effects of wear and thermal expansion on temporary crown shape control. The following methods are used.

■As the number of rolls increases, roll the sheet on a schedule that narrows the width of the sheet so that the contact positions of the rolls at the ends of the sheet width do not overlap excessively.

■Each time a piece of rolled material is rolled, the upper and lower work rolls are cyclically shifted in opposite directions in the axial direction by a specified amount to disperse wear and thermal expansion, and to prevent sudden rolls at the rolling edge of the sheet width. Prevent profile changes from occurring.

As mentioned above, in the CVC method, the shift position is determined by the rolling conditions such as the crown of the exit target plate, so the above
method is impossible. Therefore, there is no choice but to establish a CVC method that allows wear and thermal expansion dispersion by work roll shift similar to method (2).

In other words, in the conventional CVC method, if the rolling conditions such as steel type, dimensions, exit target plate crown, etc. are the same, the shift position is the same, the contact area between the rolled material and the roll does not change, and therefore the plate width end The roll profile changes significantly at the point where the rolled material contacts, but in order to put the CVC method into practical use, the contact area must be changed every time one rolled material is rolled, regardless of plate crown control. Therefore, it is necessary to develop a rolling method that allows work roll shifting.

Here, the present inventors as a means to realize the above matters,
Focusing on the simple and effective method of using work roll bending, we conducted theoretical and empirical research and development. Even in the conventional CVC method, a certain amount of work roll bending force is required to compensate for load fluctuations during rolling and temporary crown shape changes due to thermal expansion of the work roll, but according to the findings of the present inventors, If a large work roll bending force is applied and the contact area between the plate material and the roll is the same as the previous rolling with a temporary wrap door using the CvC method, the target plate crown can be adjusted by adjusting this bending force. It has been found that wear of the work roll and thermal expansion dispersion can be achieved by shifting the work roll while maintaining the desired rolling reduction conditions, and the present invention has been completed.

That is, the gist of the present invention is to (i) provide a plate crown control mechanism and a work roll bending device by shifting a pair of upper and lower work rolls having a bottle-shaped profile in opposite directions to each other in the axial direction; (ii) axially shifting said work rolls to alleviate localized wear of said work rolls and their heat crown; and (ii)
tii) Maintaining rolling conditions to obtain the target plate crown by adjusting the combination of the shift amount of the work roll and the pending force by the work roll bending device, during hot rolling. This is a plate crown control method.

According to a preferred aspect of the present invention, the work roll shift reference position when determining the shift amount of the work roll may be the work roll position at the time of rolling a preceding material of the same steel type.

Further, the relative shift amount may be set so that the work roll contact position at the width end of the plate deviates from the contact position during rolling of the preceding material by a predetermined amount or more.

In addition, the variable amount of work roll bending force - the load at the clarification of the plate after rolling (1 to
It represents the crown amount of the plate after rolling that changes with the change in the work roll bending force (n).

(Operation) Next, the present invention will be described in further detail with reference to the accompanying drawings.

First, Figures 5(a), (b), and (C) show the conventional CVC
It is a diagram showing problems with the law. When multiple rolls of the same material are successively rolled using upper and lower work rolls having a bottle-shaped profile as shown in Figure 5(a) so that the same outlet plate crouge is formed, wear and thermal expansion may occur, as shown in Figure 5. As is known from the past, the work roll profile changes as shown in (b), and as is known from the past, the amount of wear is greater at the edge of the plate width than other contact areas, and the wear rate is rapid at the edge of the plate width. Work role profile changes occur. When rolling with a work roll having such a profile under rolling conditions such that the rolling load increases with the same width, if you try to roll the plate to the same crown, the result will be as shown in Figure 5 (C). As mentioned above, rolling must be carried out with the work roll shifted in the direction where the temporary crown becomes smaller. In such a case, the strip width end must be rolled at the work roll abnormal profile area, which naturally causes damage to the rolled material. In this case, the influence of this abnormal profile occurs, resulting in an abnormal profile material having protrusions at the width end.

By the way, if an appropriate bottle curve is selected in the CvC method as described above, a plate crown control effect equivalent to rolling with a work roll provided with a normal quadratic curve crown can be obtained.

In this case, the control ability of the CvC method, which is equivalent to the quadratic curve roll crown amount ΔR per radius, is expressed by the following formula.

ΔS・ΔRcvc −ni−Bj! −ΔR・・−(1)Δ
S: Shift amount (-1) ΔRcwc: Bottle shape crown shown in FIG. 5(a) K: Constant (for example, cubic curve bottle shape Bj!!
Roll body length ΔR: Difference between the roll radius at the center of the roll body length and the roll radius at the long end of the roll body Generally, when rolled with a roll having a quadratic curve roll crown of ΔR, the exit plate crown C8 is as follows. Here, if ΔRcv is constant, ΔR: Quadratic curve roll crown amount J: Work roll bending force C: A function determined by rolling conditions such as plate width and rolling load at ΔR-0, P, and -0. Therefore, from equation (1), the exit side plate crown is as follows, and it can be seen that the exit side plate crown has a linear relationship with the shift amount ΔS. As can be seen from equation (4), under the C1 constant condition, it is possible to change ΔS according to P.

That is, as shown in Fig. 6, which shows the quantitative relationship between the work roll shift position, that is, the shift amount, and the work roll bending amount, the work roll bending force is set to the minimum Pla.
By changing the shift position from in to the maximum p2max, the shift position can be changed by without changing the outlet plate crown C11, and the work roll bending force P1 can be determined for each rolled material regardless of the plate crown control. By changing this amount, the contact area between the rolled material and the work roll can be changed even in CVC rolling of materials with the same width and the same rolling conditions, and wear and thermal expansion can be dispersed.

In other words, Fig. 7 shows a graph of the relationship when the work roll shift position and the work roll bending force are changed according to the number of rolls rolled. Even in this case, as shown in FIG. 7, if the work roll bending force is increased or decreased by a certain amount for each number of rolling rolls, the work roll shift position can be changed accordingly.

In that case, as shown in FIG. 8(a), FIG.
As shown in Fig. 8(b), a smooth bottle-shaped profile can be maintained without causing a sudden work roll profile change at the edge of the plate width, as shown in Fig. 8(b), even if rolling is continued with the same width under different rolling conditions. As shown in FIG. 5(C), the occurrence of an abnormal profile as shown in FIG. 5(C) can be prevented.

Furthermore, the bottle-shaped work roll crown ΔRCVC can be maintained by the method of the present invention, and stable plate crown control ability by the CVC method can be ensured until just before the roll is changed.

By the way, the work roll bending force required to carry out the present invention is considerably larger than the pending force required for conventional sheet crown and shape control during rolling. This is because work roll wear,
Work roll shift amount required for thermal expansion dispersion is 100+u
This is because the CVC method requires work roll bending that has the ability to control the plate crown and shape to accommodate this shift amount. This work roll bending force can be determined from equation (4) by assuming that the work roll shift amount required for work roll wear and thermal expansion dispersion is ΔS. As a result of various studies conducted by the present inventors, it has been found that ΔS only needs to be the minimum LOO++n. The work roll bending force actually required for the work shown in the example below is 150 tons/
It is not effective unless it is at least twice the pending force necessary for controlling the plate crown shape during rolling, that is, twice or more of the pending force of a rolling mill employing the conventional CvC method.

Next, an example in which the present invention is applied to a hot rolling finishing mill will be described in more detail.

(Example) The hot rolling finishing mill used in this example consisted of a 4-layer rolling mill with 7 stands, and the roll dimensions of the rolling mill were as shown in Figure 9. It is the same as that in Figure 3.

The bottle shape profile of the upper and lower work rolls 3 in FIG. 9 had a cubic curve as shown in the following equation, as shown in FIG. In addition, the work roll shift amount ΔS is ±150
+u+ (ΔSs = 150-plow).

x,: Bottle shape Off center amount (am) B1. :
Work roll body length a, b: positive constant a=0.461. b=0.365 By the way, in the bottle shape curve of equation (5), ΔRcvc
"" is 0.25am, and the backup roll body length B
j! = 1780 ■ In this example, when the work roll shift position is changed from -150 - 1 to +150 m -, if there is no change in the work roll profile due to wear or thermal expansion, the quadratic curve work roll crown will be A temporary crown control effect equivalent to a change of about 330μ can be obtained. Moreover, if the pending force is changed by about 170 tons/chijik, the CvC shift position can be changed by about 100 m+-. By the way, if the off-center amount x0 shown in equation (5) is 0, as shown in FIG.
At shift position O, the gap profile becomes the same in the width direction, which is a neutral state, but if XO>0, at shift position O, the gap profile changes to the temporary crown small side,
In this case, the plate crown will shift to the larger side. That is, as can be seen from equation (1), ΔRcvc and ΔS determine the difference from the minimum plate crown to the maximum plate crown, that is, the provisional crown control amount, and X determines the minimum plate crown or maximum plate crown value, that is, plate crown control. You can decide the level.

Table 1 summarizes the rolling results of this example with respect to the temporary crown control effect, and is a table showing the work roll profile and work roll bending force conditions in order to conduct a comparative study between the conventional technology and the present invention.

The work roll crown of the existing mill in the table shows the value per diameter; if it is negative, it will be a concave profile, and if it is positive, it will be a convex profile. Work roll bending is only increased, and the table shows the maximum bending value (minimum value is zero ton/chock).

In addition, C of the present invention is equipped with a powerful work roll bender.
In order to clarify the effect of the vC method, only existing mills of work roll vendors are used here.

However, F5 to F7 are above 200 mm due to abrasion thermal expansion dispersion.
A work roll shift of m- was carried out. Traditional CvC methods used regular work roll benders. However, the bottle shape curve was the same as that of the present invention.

Figure 11 of Table 1 shows the rolling width schedule conditions after roll change, and is compared with a schedule that mixes low-carbon materials for cold-rolled mother plants and hot-rolled products, and high-tensile strength materials for hot-rolled products. investigated. Low-carbon materials for cold rolling base materials are steel types that require a high plate crown finish even at low rolling loads from the viewpoints of threadability, plate crown, and shape controllability during cold rolling (current target finished plate crown). 60μ), high-tensile steel requires a low plate crown finish to improve dimensional accuracy (target finished plate crown 30μ or less), but it is a steel type that is difficult to achieve a low plate crown due to high rolling loads.

In addition, the temporary profile data of the rolled material marked with an arrow in the figure is
They are summarized in the table.

If these 2#1 types of mixed rolling are realized, it will be possible to achieve almost schedule-free rolling from the perspective of temporary crown and shape control.
Ronshu X9501111! P! Finishing material carbon material 0 pieces 0
And 21 pieces of 2.6-So thickness x 1200mm wide high-tensile steel material, which is difficult to finish with a low plate crown, are rolled to 70 pieces.
and 71 to 0 and compare the finished plate crowns,
The advantages of the present invention will be clarified.

FIG. 12(a) is a diagram showing the work roll shift position in the CVC method using the width schedule shown in FIG. 11, and shows the case of an F5 mill as an example.

FIG. 12(a) shows the case of the conventional CVC method, in which the work roll shift position is determined according to the rolling conditions of the strip width and rolling load so that the strip can be rolled to the exit target strip crown. On the other hand, Fig. 12 et al.) shows the CVC method of the present invention.In the present invention, when the width is the same for low carbon materials and high tensile materials, the work roll shift position is 1O- with respect to the preceding material. ■ Set up the work roll shift position while adjusting the work roll bending force so that the work roll contact position 1 at the edge of the sheet width shifts by more than 10 degrees if the sheet widths are different. Is going. The amount of deviation mentioned above may be changed depending on the rolling schedule.

As a result, when continuously rolling low carbon materials of the same width,
It can be seen that abrasion thermal expansion dispersion work roll shift of 150- is performed.

Table 2 summarizes the plate profile data of the actual finished plate crown of the rolled material indicated by the → mark in the figure.

In the existing mill, the plate crown of the low carbon material for the cold-rolled base material of the 20th roll did not reach the target plate crown of 60μ.This is because the work roll crown became large due to thermal expansion in the upstream stand of the finishing mill. Because the temporary crown becomes smaller, the plate crown is made thicker on the downstream stand (rolling causes shape defects, so the finished plate crown cannot be made larger).

In addition, it is difficult to create a low plate crown for high-strength materials, and basically in the mixed rolling of low-carbon and high-strength materials as in this rolling schedule, the temporary crown control ability is insufficient, and the conventional However, the CVC method satisfies the target plate crown of the cold-rolled paper carbon material, and it is possible to reduce the finished plate crown of high-tensile steel material to about 20 to 30μ, and it is possible to reduce the temporary crown and shape control. However, as explained in Fig. 5 (C), there is a problem with the high tensile strength material near the edge of the board width, as explained in Fig. 5 (C).
An abnormal profile in which the plate thickness changes in a protruding manner has occurred, and it is considered that mixed rolling of low carbon material and high tensile strength material is impossible.

However, in contrast to the above-mentioned conventional technology, the CVC method of the present invention makes it possible to roll a temporary crown of high tensile strength material to a thickness of 10μ or less without generating an abnormal profile. especially,
Compared to the conventional CVC method, the CVC method of the present invention is more effective.
The reason why the sheet crown becomes larger in the cold-rolled base material and smaller in the high-strength material is that in the conventional CVC method, the finishing rolling mill F
This is because defects in shape caused by abnormal plate profiles occur in stands 1 to F6, making it impossible to fully utilize the original CVC method's ability to control the plate crown and shape.

From the results shown in the above examples, it can be seen that according to the present invention, the effect of crown shape control is very large.

Table 2 (Effects of the Invention) By using the plate crown control method according to the present invention, the plate crown control ability can be dramatically improved with low equipment costs, and high dimensional accuracy can be achieved without causing abnormal profiles. It not only becomes possible to manufacture hot-rolled steel strips and hot-rolled steel sheets (
It is possible to perform mixed rolling of different steel types with significantly different rolling loads or reverse width rolling from narrow to wide materials, greatly promoting schedule freedom, improving production efficiency, reducing costs by reducing the number of work rolls owned, etc. Effectiveness and short delivery times can be achieved.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams of a conventional rolling mill with a high temporary crown and shape control function; Figure 3 is a schematic diagram of the roll arrangement of the CVC method; ), (C) are CVs performed on work rolls with bottle-shaped profiles.
A schematic explanatory diagram of the C method; FIGS. 5(a), Φ), and (C) are explanatory diagrams of the problems of the conventional CVC method; FIGS. 6, 7, and 8 are diagrams showing the CVC of the present invention. Fig. 9 is a schematic diagram of a rolling mill for implementing the temporary crown shape control method according to the present invention; Fig. 10 is an illustration of the work roll used in the present invention. An explanatory diagram of a bottle shape profile; FIG. 11 is an explanatory diagram of an example of a width schedule after roll change in hot rolling in an example; and FIG. 12 (a), (
b) is an explanatory diagram of the difference in work roll shift position between the conventional method and the present invention. 1: Bank up roll 2: Intermediate roll 3 (3a, 3b): '7-roll 4: Rolled material 5: Work roll bender 2! Figure 71

Claims (4)

[Claims] (1) using a hot rolling mill equipped with a plate crown control mechanism and a work roll bending device by axially shifting a pair of upper and lower work rolls having a bottle-shaped profile in opposite directions; Shifting the upper and lower work rolls in the axial direction in opposite directions to each other by a predetermined amount from the work roll shift position at the time of rolling the preceding material in order to alleviate local wear of the work rolls and their heat crown, and shifting of the work rolls. 1. A method for controlling plate crown during hot rolling, comprising: maintaining rolling conditions to obtain a target plate crown by adjusting a combination of bending force and bending force by the work roll bending device. (2) Claim (1) characterized in that the work roll shift reference position when determining the shift amount of the work roll is the work roll position at the time of rolling a preceding material of the same steel type.
The plate crown control method described. (3) Claim (1) characterized in that the work roll shift position is set so that the work roll contact position at the edge of the plate width deviates from the contact position during rolling of the preceding material by a predetermined amount or more. Or the plate crown control method described in (2). (4) Claims (1) to (3) characterized in that the variable amount of the work roll bending force is set within a range determined by the following formula.
) The plate crown control method described in any of the above. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ΔP_J: Variable amount of work roll bending force per chock (ton) [∂C_R/∂ΔS]: Amount of sheet crown after rolling that changes with a 1 mm work roll shift change (μ/mm ) [∂C_R/∂P_J]: The amount of plate crown after rolling that changes with a change in work roll bending force of 1 ton per chock (μ/ton)