JPH08257637A - Method for flattening tapered thick steel plate - Google Patents

Abstract

PURPOSE: To flatten a tapered thick steel plate in high accuracy without using a complicate control system by keeping a correcting reaction acted to a leveller roll group to the constant, at the time of flattening the tapered thick steel plate. CONSTITUTION: At the time of executing the flattening of the tapered thick steel plate 4 with the roll leveller, at first, the rolling reduction degree of the leveller roll 1 before starting the correction is calculated with a calculator 2 by using a material, temp., thickness, tapered degree, etc., of the steel plate to be corrected and set through a controlling device 3. When the tip part of the tapered thick steel plate 4 as the material to be corrected progresses into the leveller, the pressure in a hydraulic cylinder 6 arranged on a carriage 5 supporting the leveller rolls 1, 1,... group, is risen. The controlling device 3 stores the pressure of the hydraulic cylinder 6 for the fixed time as the reference pressure and also, the present pressure outputted from the hydraulic cylinder 6 and the reference pressure are compared. The liquid quantity in the hydraulic cylinder 6 is adjusted so that the deviation between both pressures equalizes and the correcting load giving to the tapered thick steel plate 4 is made to be the constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting the flatness of a tapered thick steel plate whose plate thickness changes continuously by using a roller leveler.

[0002]

2. Description of the Related Art The leveler reduction amount when flattening a steel sheet by using a roller leveler has an optimum value depending on the material, width, thickness and temperature of the steel sheet to be flattened. In the case of a normal steel plate, the plate width, the plate thickness and the temperature are almost constant in the plate. Therefore, when performing flatness correction, once the leveler opening is set, it is not necessary to change it thereafter.

However, when flattening a so-called tapered thick steel plate in which the plate thickness continuously changes in the longitudinal direction, there is a temperature change in the longitudinal direction due to this plate thickness change in addition to the plate thickness of the steel plate. . This temperature change appears as a phenomenon in which the thin portion has a larger temperature drop during rolling and conveyance than the thick portion, and the temperature during flattening becomes low.

Therefore, for example, Japanese Patent Laid-Open No. 62-18752.
In Japanese Patent No. 1 gazette, the thickness and temperature of the steel sheet to be corrected on the entrance side of the roller leveler are measured, and the traveling speed of the steel sheet is measured. When the part reaches each roller, predict the roller straightening load to keep the preset straightening effect constant, predict the shared load on the upstream and downstream sides of the roller leveler from this predicted straightening load, and use this predicted share. The load and the measured load measured on the upstream side and the downstream side in the roller straightening machine are compared, and the straightening load of the leveling roller is adjusted so that the upstream corrective load and the measured load and the downstream predicted straightening load and the measured load are equal. A defined reduction control method is disclosed.

[0005]

However, the rolling reduction method disclosed in the above publication has some fundamental problems.

The first problem is the difficulty of measuring the plate thickness.
That is, for a thick steel plate whose measurement target is a high temperature, it is necessary to use a radiation plate thickness gauge or the like, which increases the equipment cost.

Secondly, it is difficult to measure the traveling speed of the steel sheet. That is, in order to detect the traveling speed of the steel sheet, a speed detector is required in addition to the tip detector of the steel sheet. Even if these detectors themselves can be obtained relatively inexpensively, high accuracy cannot be obtained in speed detection, and this point is also specified in the publication.

This speed detection error accumulates as a prediction error of the amount of progress as the steel sheet to be straightened becomes longer, and has a great influence on the control accuracy of the reduction amount.

Thirdly, if the measurement results of the temperature, thickness and traveling speed of the steel sheet are all reflected to perform the correction, an extremely complicated control system must be constructed, which not only increases the equipment cost. The point is that the accuracy commensurate with the cost cannot be obtained.

Therefore, an object of the present invention is to enable flatness correction of a tapered thick steel plate with relatively high accuracy under simple equipment without using a complicated control system.

[0011]

A first aspect of a flattening method for a tapered thick steel plate according to the present invention, which has solved the above-mentioned problems, is for flattening a tapered thick steel plate whose plate thickness continuously changes by a roller leveler. The flattening of the tapered thick steel plate is performed while keeping the straightening reaction force acting on the leveler roll group in the roller leveler constant.

In a second aspect, when flattening a tapered thick steel plate having a continuously changing plate thickness using a roller leveler, a straightening reaction force acting on a leveler roll group in the roller leveler is kept constant and the leveler roll is also used. The roll opening of the taper thick steel plate is estimated, the plate thickness of the tapered thick steel plate is estimated from the detected value of the leveler opening, and the flattening of the tapered thick steel plate is performed while changing the straightening speed according to the estimated plate thickness. It is a feature.

[0013]

Function When flattening a tapered thick steel plate, it is necessary to adjust the leveler reduction amount according to the change in plate thickness and the change in plate temperature due to the taper being applied.

However, the leveler reduction correction load according to the plate thickness change and the leveler reduction adjustment amount according to the plate temperature change act in opposite directions.

Based on the experiments described in the following examples, the present inventors found that the leveler reduction correction load according to the change in plate thickness and the leveler reduction correction load according to the change in plate temperature are almost the same in opposite directions. It was found to change with quantity. Therefore, since the leveler reduction correction loads for both of them cancel each other out, as a result, by performing the flatness correction while keeping the leveler reduction correction load constant, it is possible to perform the flatness correction with relatively high accuracy. The inventors have found that it is possible and have completed the present invention.

On the other hand, in many cases, the correction of only one pass does not provide sufficient flatness, and therefore correction of two or more passes is often performed. In this case, the tapered thick steel plate comes into contact with the leveler roll during the straightening process to be cooled and a temperature drop occurs. The amount of temperature drop is larger in the thin plate portion of the tapered thick steel plate than in the thick plate portion, and therefore, in the second and subsequent passes, the straightening load applied during straightening adopted in the case of only one pass. It is not possible to secure the optimum amount of reduction according to the temperature drop simply by directly adopting the method of keeping the temperature constant.

As described above, in the second and subsequent passes, the element of temperature change becomes stronger than the element of plate thickness change. Therefore, in the second aspect of the present invention, the correction reaction force acting on the leveler roll group in the roller leveler is kept constant, the leveler opening of the leveler roll is detected, and the plate of the tapered thick steel plate is detected by the detected value of the leveler opening. The thickness is estimated, and the flattening of the tapered thick steel plate is performed while changing the correction speed according to the estimated plate thickness.

Specifically, for the thin plate portion,
The flattening is performed by increasing the straightening speed faster than the thick portion. In this case, it is necessary to detect the current plate thickness of the tapered thick steel plate, but by detecting the leveler opening of the leveler roll without using a plate thickness gauge, etc., that is, the reduction screw height of the reduction cylinder and the liquid level. We have found that this can be substituted by adopting the column height as it is.

[0019]

EXAMPLES Before describing specific examples of the present invention, model experiments conducted by the present inventors in the course of completing the present invention will be described.

Assuming that the plate temperature of the tapered thick steel plate is uniform in the lengthwise direction, it is sufficient to control the leveler reduction amount by paying attention to only the change of the plate thickness. Therefore, as a first model experiment, when the change in the straightening load in the length direction of the tapered thick steel plate was obtained when the plate temperature in the length direction of the tapered thick steel plate was constant, it was as shown in FIG. In the example of Fig. 2, the yield stress is 400 N / mm ² class and the plate width is 3000 m.
The taper thick steel sheet having a temperature of 800 m and a temperature of 800 ° C. is straightened with an optimum reduction amount. As the optimum reduction amount, a value calculated so that the plastic deformation rate in the plate thickness direction of each part of the steel plate was 80% was used.

The straightening load at this time is shown in FIG. According to FIG. 3, the straightening load in the thin plate portion is smaller than that in the thick plate portion, and the ratio of the minimum straightening load to the maximum straightening load is about 1: 1.3. I understand.

Next, as a second model experiment, assuming that the plate thickness of the tapered thick steel plate is 18 mm and uniform in the length direction, the steel plate in which only the plate temperature changes in the length direction is corrected by the optimum reduction amount. The experiment was done. In this experiment, contrary to the first model experiment, the leveler reduction amount may be controlled by focusing only on the change in the plate temperature in the length direction of the steel plate to be straightened.

The change in the straightening load depending on the optimum amount of reduction in this case was as shown in FIG. According to FIG. 5, it is found that the straightening load in the low temperature portion is larger than the straightening load in the high temperature portion and the ratio of the maximum straightening load to the minimum straightening load is 1.25: 1.

From these model experiments, when the two factors that affect the straightening load of the tapered thick steel plate, that is, the plate thickness change and the temperature change are independently considered, the change of the optimum straightening load is completely opposite. There is a trend, and the amount of change is approximately equal for each amount. This means that even if the plate thickness change and the temperature change are detected and the leveler reduction control is performed, the two elements cancel each other out, and as a result, the straightening load becomes almost constant during straightening. ing.

Actually, the straightening load of the taper thick steel sheet having both the plate thickness distribution shown in FIG. 2 and the plate temperature distribution shown in FIG. The change is as shown in FIG. 6, and it can be seen that the correction load is substantially constant.

The above facts have been proved by the inventors of the present invention also as a result of studying various other tapered thick steel plates. Therefore, according to the present invention, even if the plate thickness change and the temperature change are not detected online like the conventional proposal example, keeping the straightening load constant during straightening is substantially performed by the target optimum reduction amount. It can be performed.

FIG. 1 is a schematic view of a roller leveler facility for flattening according to the present invention. Under the first aspect of the present invention, the reduction opening of the leveler roll 1 before the start of straightening is calculated in advance by the computer 2 according to the material, temperature, thickness, taper amount, etc. of the steel sheet to be straightened, and the controller 3 is set. Has been set. After that, when the tip of the tapered thick steel plate 4 as the material to be straightened enters the leveler, the leveler rolls 1, 1
The pressure in the hydraulic cylinder 6 arranged above the carriage 5 that supports the group increases.

Then, in the control device 3,
For example, the pressure of the hydraulic cylinder 6 after a lapse of 0.1 seconds is stored as a reference pressure, and the control device 3 compares the current pressure output from the hydraulic cylinder 6 with the previously stored reference pressure to obtain the current pressure. The amount of liquid in the hydraulic cylinder 6 is adjusted so that the deviation between the pressure and the reference pressure becomes equal, and the straightening load applied to the tapered thick steel plate 4 is made constant. Here, the correction load control of each hydraulic cylinder 6 is independently performed.

Under the second mode, the leveler operation speed at the start of correction is calculated by the computer 2 in advance, and the controller 3 is operated.
It is set through. When setting the speed, when the tapered thick steel plate has a thin tip with respect to the traveling direction, the speed should be as high as possible. Set to slow down so that the limit is not exceeded. Under such a speed setting, when the tapered thick steel plate 4 is bitten in, the straightening load is made constant as in the first mode, and the hydraulic cylinder 6 at that time is fixed.
The opening degree of the leveler roll 1 is estimated based on the reduction screw height and the liquid column height, and the operating speed of the leveler is increased or decreased via the control system 7 of the drive motor according to the increase or decrease of the opening degree.

<Embodiment> Next, an example of a concrete implementation result of the present invention will be described. Flattening of a tapered thick steel plate was performed using the roller leveler shown in FIG. In flattening in the present embodiment, the taper thick steel plate used as the material to be straightened has a plate width of 2000 to 3000 mm, the thinnest part has a plate thickness of 12 mm, and the thickest part has a plate thickness of 18 mm. Twenty taper thick steel plates of this size were flattened, and the flatness of each taper thick steel plate before and after straightening was measured. A histogram of the number of tapered thick steel plates divided by the flatness before straightening is shown in FIG. 7, and a histogram of the number of tapered thick steel plates divided by the flatness after straightening is shown in FIGS. 8 and 9, respectively. Here, FIG. 8 shows the results of performing three-pass correction at a constant speed, and FIG. 9 shows the results of performing three-pass correction while increasing or decreasing the correction speed according to the estimated plate thickness. The value defined by the following equation (1) was used for the flatness.

[0031]

[Equation 1]

As can be seen from FIGS. 7, 8 and 9, the flatness of the tapered thick steel plate is greatly improved by the method according to the present invention, and many tapered thick steel plates generally have the desired target value after straightening. The flatness within ± 0.2% was achieved.
It can also be seen that the correction accuracy is higher in the case of FIG. 9 than in the case of FIG.

[0033]

As is apparent from the above description, according to the present invention, there is no need for equipment such as a plate thickness meter and a plate thermometer, and there is no complicated control. It becomes possible to straighten the steel sheet. Therefore, in terms of cost, it is about 5
One-half the equipment cost will suffice.

[Brief description of drawings]

FIG. 1 is a schematic view of a roller leveler facility for flattening according to the present invention.

FIG. 2 is a graph showing a plate thickness distribution in a length direction of a steel plate used in a first model experiment.

FIG. 3 is a graph showing the distribution of the correction load.

FIG. 4 is a graph showing a temperature distribution in a temperature length direction of a steel sheet used in a second model experiment.

FIG. 5 is a graph showing the distribution of the correction load.

FIG. 6 is a graph showing plate thickness distributions of steel plates used in the first and second model experiments, and distributions of straightening loads of tapered thick steel plates having a temperature distribution.

FIG. 7 is a histogram of the number of tapered thick steel plates divided by flatness before straightening in the example.

FIG. 8 is a histogram of the number of tapered thick steel plates divided by the flatness after correction according to the first mode.

FIG. 9 is a histogram of the number of tapered thick steel plates divided by the flatness after correction according to the second mode.

[Explanation of symbols]

1 ... Leveler roll, 2 ... Calculator, 3 ... Control device, 4 ... Tapered steel plate, 5 ... Carriage, 6 ... Hydraulic cylinder.

Claims (2)

[Claims] 1. When flattening a tapered thick steel plate whose plate thickness continuously changes by a roller leveler, flattening a tapered thick steel plate is performed while keeping a constant correction reaction force acting on a leveler roll group in the roller leveler. A flattening method for a tapered thick steel plate, which is characterized in that: 2. When flattening a tapered thick steel plate whose plate thickness continuously changes by using a roller leveler, a straightening correction reaction force acting on a leveler roll group in the roller leveler is kept constant and a roll opening of the leveler roll is maintained. Is detected, the plate thickness of the tapered thick steel plate is estimated from the detected value of the leveler opening, and the flattening of the tapered thick steel plate is performed while changing the correction speed according to the estimated plate thickness. A method for straightening thick steel plates.