JPS6328688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting the crown and flatness of rolled material.

In general, the flatness of a rolled material refers to shapes such as mid-elongation, edge elongation, and waving, as well as warping throughout the length or width direction, and the crown of a rolled material refers to the profile of the cross section of the material.

In recent years, demands on the accuracy of crown and flatness of rolled products such as steel plates have become stricter. In conventional rolling mills, the thickness of the rolled material in the longitudinal direction can be controlled with relatively high accuracy using an automatic thickness control device, but the thickness of the material in the width direction is controlled by a roll bender, making it difficult to control the thickness. has its limits.

Therefore, rolling mills equipped with axially movable rolls, rolling mills equipped with variable crown rolls, etc. have been developed to replace roll benders and improve the accuracy of the crown and shape of materials. The former rolling mill controls the back-up force of the work rolls by moving intermediate rolls of six stacked rolls in opposite directions in the axial direction. The latter rolling mill has a pressure receiving chamber between the roll arbor and the sleeve,
A pressure medium is supplied to this pressure receiving chamber, and the amount of crowning of the roll is controlled by adjusting the pressure of the medium.

All of these conventional techniques improve the rolling mill to improve the ability to control roll deflection and minimize the crown of the material (quantitatively small, ranging from 0.5 to 2% of the thickness). However, there is a limit to this, and a completely rectangular cross section cannot be achieved.
Furthermore, if the crown of the material is made smaller during rolling, the material tends to meander, making the work unstable. Furthermore, in rolling mills, the crown of the material can be reduced to some extent by reducing the deflection of the rolls, but it is impossible to eliminate edge drops. Additionally, remodeling the rolling mill requires a large capital investment.

As an inexpensive method, it is possible to control the cross section of the rolled material into a rectangular shape by rolling down the middle and high parts in the thickness direction of the rolled material using light reduction rolling, but this would severely deteriorate the shape of the rolled material and make it impossible to operate. becomes.

In view of the above facts, the present invention is a brand new attempt to correct the crown of material generated in a rolling mill by bending and tensile plastic deformation.

Shape defects in rolled materials are caused by differences in longitudinal elongation of the material, and cannot be corrected unless plastic elongation is imparted to the material.

Roller levelers are designed to correct warpage defects (particularly warpage in the longitudinal direction) and reduce residual stress, so their ability to correct shape defects is low.
In order to give plastic elongation to a material with a roller leveler, it is necessary to actively apply axial force. With conventional roller levelers, the residual stress within the material and the frictional force generated between the roll and the material only act as a slight axial force, and basically they cannot impart plastic elongation, and their ability to correct shape defects is low. .

Tension levelers have been developed to correct shape defects in rolled materials. Tension levelers apply bending and tension to materials to correct shape defects. The difference in elongation length of materials due to rolling mills is usually about 0.1%, which causes shape defects such as mid-elongation and ear waves. If this is stretched by 0.2 to 0.5% using a tension leveler, the material will become flat. For this reason, the maximum elongation rate of conventional tension levelers is approximately 1 to 1.5%. but,
Since it is usually used at the minimum required elongation rate, the reduction in thickness and width of the material due to tension levelers is extremely small and is ignored in practice.
After all, in the conventional method, there was no idea of using a tension leveler to straighten the crown of the rolled material.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for correcting the crown and flatness of a rolled material inexpensively and accurately by making maximum use of existing techniques.

Before explaining the method of the present invention, the crown (CR) _S and edge drop (ED) _se of the rolled material used herein will be defined as follows with reference to FIG.

(CR) _s = h _c − h _s (ED) _se = h _s − _h ewhere h _c : Thickness at the center of the cross section of the rolled material with a width of 2C h _s : Thickness from the edge of the cross section of the rolled material to the center side Thickness at a distance S distance h _e : Thickness at a distance e from the edge of the cross section of the rolled material toward the center The method of the present invention applies the rolled material to a plurality of roll rows arranged in a staggered manner. passing the material through, applying bending tension in the longitudinal direction of the material, applying bending in the width direction of the material by some roll groups of the roll rows, depending on the entrance thickness distribution of the material. It is made by adjusting the bending in the width direction and the plastic elongation in the longitudinal direction.

There are three specific methods for bending the rolled material in the width direction:

First, the first method is to widen the horizontal roll spacing of some of the roll groups in the roll row, and to bend the roll shafts or provide crowns to the rolls.

A second method is to widen the horizontal roll spacing of some of the roll groups in the roll row, form a crown on one side of at least one pair of rolls among the roll groups, and set the crowns opposite to each other. and the pair of rolls are moved in opposite directions in the axial direction. This method can respond to changes in the width of the material and is highly effective for any size.

The third method is a combination of the first method and the second method, in which the pair of rolls is moved in the axial direction and at least one roll other than the pair of rolls is moved. The shaft is deflected or the roll is crowned.

Next, the method of the present invention will be specifically explained with reference to the drawings. A bending tension was applied to the rolled material 2 using a conventional tension leveler 1 shown in FIG. 2, giving the material 2 a plastic elongation of 5%. This 5% plastic elongation is about 0.2 to 0.5% in normal shape correction, so it can be said to be an extremely large elongation that cannot be expected from the concept of shape correction. Test rolled material 2 is a cold rolled steel strip, and its dimensions are 1.0 mm thick x 200 mm wide.
It is. The diameter of the roll 11 of the tension leveler 1 is 50 mm, and the number of rolls is 8.

FIG. 3 shows the cross-sectional profile of the rolled material 2 when bending tension is applied to the rolled material 2 under the above conditions. In Fig. 3, the solid line m is the base material (the thickness is uniform in the width direction because it is a slit material made from a wide material), the solid line g is the material without roll bending, and the dotted line k is the base material without roll bending.・Indicate each item that was bent.

As can be seen from Figure 3, when an extremely large plastic elongation, which has never been applied before, is applied to a rolled material using a tension leveler, the thickness of the material's widthwise edge becomes thicker (hereinafter referred to as ) occurs. The cause of this edge-up is currently under investigation, but it can be estimated as follows.

When a strong bending tension is applied to a rolled material, the edges of the material are bent in the longitudinal direction as well as in the width direction, which increases the strain in the width direction of the material, resulting in a decrease in the thickness of the edge. It is understood that this is because it becomes smaller.

In other words, the following equation is generally established according to the law of constant volume due to plastic deformation of materials.

(1) Regarding the center part of the material in the width direction with only longitudinal bending and no bending in the width direction, ε _e + ε _b + ε _h = 0, where ε _e : Strain in the longitudinal direction of the center part of the material ε _b : Width direction of the center part of the material Strain ε _h : Strain in the thickness direction at the center of the material (2) Regarding the edge part in the width direction of the material where longitudinal bending and width direction bending coexist, ε' _e + ε' _b + ε' _h = 0. However, ε' _e : Material Strain in the longitudinal direction of the edge portion ε′ _b : Strain in the width direction of the material edge portion ε′ _h : Strain in the thickness direction of the material edge portion In this example, ε _e =ε′ _e , but the edge portion of the material has a width Due to the occurrence of directional bending, the strain in the width direction increases, and ε _b < ε′ _b . As a result, ε _h > ε′ _h (edge up) holds true. Note that this bending of the edge portion in the width direction is a phenomenon that occurs because the material is bent in the longitudinal direction, and the edge swelling phenomenon does not occur simply by stretching.

It should be noted that since ε _e =ε′ _e , the flatness correction of the material is also achieved at the same time.

Therefore, by using edge up, it is possible to eliminate edge drop. However, this is limited to the edges of the material, so if you develop this edge up to the center of the width of the material,
In other words, it can be easily assumed that if the widthwise bending is applied not only to the edges of the material but also to the center of the width of the material, the crown of the material can also be controlled.

As a method of bending the material in the width direction from the edge of the material to the center of the width of the material, as shown in FIGS. Spread it out and deflect the roll shaft. The reason for widening the roll interval as shown in FIG. 4 is to make it easier to bend the material in the width direction. The roll shaft can be deflected by a hydraulic cylinder (Fig. 5), by a split backup roll 12 (Fig. 6), or by supplying fluid to a pressure chamber formed between the arbor and the sleeve. A variable crown roll (not shown) may be used to change the crown of the roll.
A conventional crowning roll may also be used.

When a bending tension is applied to the material with the roll 11 bent, the thickness distribution in the width direction of the material becomes like the curve k shown by the dotted line in FIG. The more severe the bending, the more concave crown size the thickness distribution becomes.

Instead of deflecting the roll shaft, as shown in FIGS. 7 and 8, the roll 1 on the upstream side of the leveler 1
Increase the horizontal roll spacing of 1 and increase the horizontal roll spacing of at least 1
A crown may be formed on one side of the pair of rolls 11, the crowns may be provided on opposite sides, and the pair of rolls may be moved in opposite directions in the axial direction.

When such a crown roll is used, the thickness distribution of the material in the width direction becomes as shown by the curve k shown by the dotted line in FIG. 3, as described above.

Note that the thickness distribution changes significantly depending on whether the deflection shape or crown shape of the roll is convex, concave, or has a complex waveform. It was also confirmed that a uniform thickness distribution in the width direction can be achieved simultaneously with flatness correction.

The above has mainly explained the case where the rolled material is a cold-rolled steel strip, but since the higher the temperature of the material, the greater the plastic elongation of the material at lower tensions, this also applies to hot-rolled materials. The method of the invention is fully applicable. For example, the method of the present invention can be effectively applied to hot rolling lines, continuous annealing lines, galvanizing lines, etc.

As a method of applying tension to rolled material, the ninth
As shown in the figure, a bridle roll 3A, a pinch roll 4B, a rolling mill 5C, or a combination thereof can be provided on the entrance/exit side of the leveler 1 to which the method of the present invention is applied.

When the tension is low, the roll width is wide, the roll deflection is maximum, and the roll crown amount is large, the rolled material does not adhere tightly to the roll over the entire width, and some parts may float, resulting in small bending in the width direction. In such a case, the effects of the present invention will be enhanced if the method shown in FIG. 10 is used to achieve close contact. That is, the degree of adhesion is increased by applying pressure to the strip from the opposite side of the leveler roll 11 using the presser roll 13, or by lowering the tension distribution changing roll 14 installed before (after) the leveler roll 11. can be done. Instead of applying pressure using the presser roll 13, it is also effective to apply pressure by spraying fluid. Even when the leveler roll and the rolled material are in perfect contact, it is possible to change the thickness distribution in the width direction by changing the tension distribution in the width direction using the tension distribution changing roll 14.

Although the present invention describes a method in which bending and tensioning is performed using rolls arranged in a staggered manner, the same applies to bending and tensioning using a fixed tool other than rolls, and the present invention also includes a fixed tool method. included.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the rolled material. Figure 2 is an explanatory diagram of a normal tension leveler. Figure 3 is a graph showing the cross-sectional profile of a rolled material when large plastic elongation is applied. FIG. 4 is an explanatory diagram of a tension leveler to which the method of the present invention is applied. Figure 5 is a front view taken from the - line in Figure 4. FIG. 6 shows a modification of FIG. 5. FIG. 7 shows a modification of FIG. 4. Figure 8 is a plan view taken from the - line in Figure 7.
FIG. 9 is an explanatory diagram showing a method of applying tension to rolled material. FIG. 10 is an explanatory diagram showing a method for reducing poor adhesion between the roll and the rolled material. 1: Tension leveler, 2: Rolling material, 1
1: Leveler roll, 12: Split backup
Roll, 13: Presser roll, 14: Roll for changing tension distribution.

Claims (1)

[Scope of Claims] 1. Passing a rolled material through a plurality of roll rows arranged in a staggered manner, applying bending tension in the longitudinal direction of the material, and applying a bending tension to the material by some roll groups of the roll rows. A method for correcting the crown and flatness of a rolled material, which comprises applying bending in the width direction of the material, and adjusting width direction bending and longitudinal direction plastic elongation according to the entry side thickness distribution of the material. 2. Applying bending in the axial direction of the rolled material by widening the horizontal roll interval of some of the roll groups in the roll row and bending the roll axis, or adding a crown to the rolls. A method according to claim 1, characterized in that: 3. The roll spacing in the horizontal direction of some of the roll groups in the roll row is widened, a crown is formed on one side of at least one pair of rolls in the roll group, the crowns are provided on opposite sides, and 2. A method as claimed in claim 1, characterized in that bending is applied in the width direction of the rolled material by moving pairs of rolls axially in opposite directions. 4. The horizontal roll spacing of some of the roll groups in the roll row is widened, a crown is formed on one side of at least one pair of rolls in the roll group, the crowns are provided on opposite sides, and said rolled material by moving pairs of rolls relative to each other in the axial direction and deflecting at least one roll axis of said roll group other than said pair of rolls or by crowning said rolls; The method according to claim 1, characterized in that the bending is applied in the width direction.