JP3331990B2 - Inflection point judgment method of material curve at temper rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for judging an inflection point of a material curve showing a relationship between a roll gap and a rolling force in temper rolling of a steel sheet after annealing.

[0002]

2. Description of the Related Art When temper rolling of a thin steel sheet such as a tinplate sheet after annealing is performed, at the inflection point of a material curve showing a relationship between a roll gap and a rolling force, when a rolling force is continuously changed. A jumping phenomenon occurs in which the elongation changes abruptly. This is the same phenomenon as the yield point elongation phenomenon observed in the stress-strain relationship of a general tensile test. When the elongation rate changes suddenly, the jumping phenomenon occurs because the elongation rate is actively controlled. Occurs, the elongation rate fluctuates greatly, and quality defects such as abnormal elongation rate occur.

[0003] The jumping phenomenon is likely to occur in a low-pressure region where the elongation rate of the temper rolling (hereinafter, wet rolling) using a rolling liquid is about 15% or less. In temper rolling (hereinafter, dry rolling) that does not use a rolling liquid, a jumping phenomenon is unlikely to occur, but may occur during rolling at an elongation of about 2 to 5%.

[0004] A method for preventing the occurrence of a jumping phenomenon in a low-pressure region where the elongation percentage of wet rolling is about 15% or less is disclosed in Iron Making Research No. 319 (1985), p. 52 to 59 (hereinafter, Prior Art 1). In Prior Art 1,
At the time of temper rolling of the steel sheet after annealing, an appropriate roll diameter and a large rolling fluid having a large coefficient of friction are used to narrow the area where the jumping phenomenon occurs, and to set the tension set value, the rolling reduction, the elongation, etc. Rolling is performed under conditions to avoid the occurrence of a jumping phenomenon.

[0005] However, in the prior art 1, in the vicinity of the inflection point of the material curve showing the relationship between the roll gap and the rolling force where a jumping phenomenon occurs due to the change of the temper rolling cycle itself, the influence of the variation of individual material characteristics, and the like. Temper rolling is performed in the region, and a jumping phenomenon occurs by controlling the elongation at that time, and the occurrence of this jumping phenomenon cannot be reliably prevented.

Further, in the prior art 1, since it is necessary to employ a rolling fluid having an appropriate roll diameter and a large friction coefficient, equipment remodeling and a change in the rolling fluid are required, and the operation restriction is increased, and the existing operation is greatly restricted. There is also a problem that many points cannot be easily implemented in the temper rolling mill.

[0007] Since the jumping phenomenon is less likely to occur in the low pressure reduction region of dry rolling, dry rolling has conventionally been used for temper rolling of annealed steel sheets such as tin original sheets having a small thickness. For the DR material requiring an elongation (up to about 35%), wet rolling is adopted. Jumping phenomena occur frequently in wet rolling, and it is particularly important in operation to prevent jumping phenomena. In particular, when a temper rolling mill is connected in series with a so-called continuous line, such as a continuous annealing furnace, the occurrence of a jumping phenomenon causes a temper rolling condition,
As a result, the operating conditions of the entire line need to be changed, causing significant inconvenience in the quality and operation of products.

In dry rolling, the elongation is about 2%.
There has not been proposed any effective means for grasping in advance the occurrence of a jumping phenomenon during rolling of up to 5% and reliably preventing the occurrence of the jumping phenomenon.

[0009]

That is, in the conventional temper rolling, since the occurrence of a jumping phenomenon cannot be grasped in advance, the operator takes some measures only after confirming a jumping phenomenon such as an abnormal elongation rate. The response was delayed, or the response could not be taken, or even if the response was made, the situation was erroneously determined and an operation error occurred, thereby expanding the influence range of the quality abnormality.

At the time of temper rolling, if it is possible to accurately grasp the inflection point or approaching the inflection point of the material curve showing the relationship between the roll gap and the rolling force, the rolling conditions are changed at an early stage, and the above-mentioned wet rolling or dry rolling is performed. The occurrence of the jumping phenomenon can be prevented.

The present invention provides a method capable of accurately determining an inflection point of a material curve showing a relationship between a roll gap and a rolling force when a tempered steel sheet is subjected to temper rolling in consideration of the above circumstances. With the goal.

[0012]

Means for Solving the Problems The present inventors have studied various methods for accurately grasping the inflection point of the material curve showing the relationship between the roll gap and the rolling force. As a result, when the frequency analysis of the time series data of the sheet thickness or the elongation or the rolling force or the roll gap was performed, at the inflection point of the material curve, the intensity level of the frequency in the frequency band of the specific region of the data became higher. It has been found that the inflection point of the material curve can be accurately grasped by grasping the frequency intensity level.

The present invention is based on the above findings, and the means of the present invention for solving the above problems are as follows.

In the first invention, when temper rolling of an annealed steel sheet, a frequency analysis is performed based on time series data of any one of a thickness, an elongation, a rolling force, and a roll gap, and a frequency of a specific region is determined. When the intensity level of the frequency in the band exceeds a preset value, it is determined that the point of inflection of the material curve indicating the relationship between the roll gap and the rolling force is the inflection point of the material curve during temper rolling. This is an extreme point determination method.

According to a second aspect of the invention, when temper rolling of the annealed steel sheet, frequency analysis is performed based on time series data of any one of the sheet thickness, elongation, rolling force, and roll gap, and the frequency of a specific region is determined. When the intensity level of the frequency in the band approaches a preset value, the material curve at the time of temper rolling is characterized by determining that it is near the inflection point of the material curve indicating the relationship between the roll gap and the rolling force. This is an inflection point determination method.

According to a third invention, in the first invention or the second invention, a frequency band of a specific region is changed in accordance with a line speed at the time of temper rolling. This is an extreme point determination method.

FIG. 1 shows a material curve showing a relationship between a roll gap and a rolling force in a low rolling region of a steel sheet after annealing in temper rolling. In this case, (1) when the rolling force is increased and the mill elasticity curve is moved to →, the moment the milling elasticity curve slightly exceeds the intersection point a with the material curve, jumps to a point b. (2) As the rolling force is further increased to →, the rolling force and the roll gap show a stable relationship along point b → point c. (3) In order to obtain a low elongation, the mill elastic curve is
The mill elasticity curve intersects with the material curve d
When the value falls below the point, it jumps to the point e.

That is, the hysteresis history of abcde is drawn. It is considered that the jumping phenomenon occurs when the control is destabilized due to the sudden jump from point a to point b and point d to point e.

In FIG. 1, when the rolling force is decreased and the mill elasticity curve is moved to →, the region from point d to point e is shown. The region from the point b to the point b is an unstable region where a jumping phenomenon occurs. In the present invention, a point having a different roll gap with respect to the same rolling force when the rolling force is continuously changed, such as points a and d, is used to change the material curve showing the relationship between the roll gap and the rolling force. It is called an extreme point.

When frequency analysis is performed based on time series data of any one of the sheet thickness, elongation, rolling force, and roll gap, the intersection of the mill elasticity curve and the material curve is a point d.
Or, when approaching the point a, the intensity level of the frequency in the frequency band of the specific region increases. Therefore, the frequency intensity level in the specific frequency band at the point d of the material curve when the rolling force is continuously reduced in advance and the point a of the material curve when the rolling force is continuously increased is determined in advance. Every other (hereinafter, set value), performing a frequency analysis in the frequency band of the specific region at the time of temper rolling to obtain an intensity level of the frequency band (hereinafter, measured value), and comparing the measured value with the set value. By determining whether the mill elastic curve is approaching the inflection point d or point a of the material curve, that is,
If the measured value is somewhat smaller than the set value, it can be determined that it is close to the inflection point, and if the measured value exceeds the set value, it can be determined that it is the inflection point.

FIG. 1 illustrates the case of wet rolling in a low rolling region. Even in the case of dry rolling, in a region where a jumping phenomenon occurs when the rolling force is continuously changed, a specific rolling is performed in advance. By investigating the frequency intensity level in the frequency band, it can be determined in the same manner as described above whether the material curve is at or near the inflection point.

According to the present invention, the inflection point of the material curve showing the relationship between the roll gap and the rolling force can be accurately determined. Based on this judgment, the operator or automatic control takes action such as changing the output tension or reducing the speed at the inflection point of the material curve, thereby suppressing the occurrence of quality abnormalities due to fluctuations in elongation or thickness. Becomes possible.

If an alarm is issued to the operator when the vehicle approaches the inflection point, the above-mentioned action can be taken earlier and more reliably.

It has been found that the frequency band in which the strength level increases changes depending on the line speed during temper rolling. Therefore, by changing the frequency band of the specific region at the time of judgment according to the line speed at the time of temper rolling, it becomes possible to more accurately grasp the inflection point of the material curve.

In addition, the method of determining the inflection point has an advantage that it can be installed inexpensively not only in a new temper rolling mill but also in an existing temper rolling mill.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be further described.

FIG. 2 is a block diagram showing a control system of a temper rolling mill for explaining an embodiment of the present invention. FIG.
In the above, S is an annealed steel sheet, 1 is a temper roll, 2
Is a hydraulic pressure reduction device, 3a is an entrance bridle roll, 3b is an exit bridle roll, 4 is a thickness gauge, 6 is a rolling load cell,
7a is the feed length of the incoming bridle, 7b is the feed length of the outgoing bridle, 8 is the elongation calculator, 9 is the frequency analyzer, 10 is the inflection point discriminator that determines the inflection point of the material curve, and 16 is the alarm. Generator.

In the temper rolling mill shown in FIG. 2, when the temper rolling is performed on the annealed steel sheet, the rolling force or the like is controlled by the hydraulic pressure reducing device 2 so that the elongation calculated by the elongation calculating device 8 is a predetermined value. Feedback control is performed so that the elongation rate is obtained or the steel sheet thickness detected by the thickness gauge 4 becomes a predetermined thickness. At that time, the inflection point of the material curve indicating the relationship between the roll gap and the rolling force is determined as described below.

In FIG. 2, the entrance bridle roll 3a
The feed length of the temper rolling mill 1 is determined from the rotation speed of the temper rolling mill 1 and the feed length of the temper rolling mill is determined from the rotation speed of the output bridle roll 3b. To calculate the elongation. The data of the elongation calculated in the above, the roll gap detected from the position of the oil column of the hydraulic pressure reduction device 2, the thickness detected by the thickness gauge 4, and the reduction force detected by the rolling load meter 6 are each analyzed by a frequency analyzer. 9 is output.

The frequency analyzer 9 performs a frequency analysis based on the input data of the thickness, elongation, rolling force, and roll gap, and outputs the analysis result to the inflection point discriminator 10.

In the inflection point discriminating apparatus 10, the frequency band f _{0 to} f _{1 of the} specific region and the total intensity S ₁ of the frequency band S ₁ in the frequency band are previously determined for the sheet thickness, elongation, rolling force and roll gap. _With respect to the ratio S ₁ / S _{0 to 0} , set values k ₁ and k _{2 of} two levels of high and low can be set. Set value k ₁ high level side,
Set at the inflection point of the material curve and set value k ₂ on the low level side
Is set near the inflection point of the material curve.

The inflection point discriminating device 10 discriminates the frequency analysis result of the time series data of the sheet thickness, elongation, rolling force or roll gap sent from the frequency analyzing device 9. That is, when the frequency intensity of the frequency band f _{0 to} f ₁ set in advance of the frequency analysis data exceeds the set value k ₂ on the low level side, it is determined that the inflection point of the material curve is approaching, and the high level side is determined. when it exceeds the set value k _1, determines that the inflection point of the material curve showing the relationship between the roll gap and rolling force.

The case where the inflection point of the material curve is determined by performing frequency analysis based on the time series data of the measured values of the rolling force will be specifically described with reference to FIG.

FIG. 3A is a diagram of time series data of the rolling force of the rolling load cell 6. FIG. 3B is a diagram in which the time series data is output to the frequency analysis device 9 and frequency components of the time series data of the rolling force are extracted as a frequency spectrum from 0 to 500 Hz. The result is input to the inflection point discriminating device 10 for the material curve.

In the inflection point discriminating apparatus 10, the frequency band f _{0 to} f _{1 of} the specific region is set to 200 to 400 Hz, and the ratio S ₁ / S ₀ of the frequency intensity S _{1 to} the total intensity S ₀ in this frequency band is set. The set value k ₁ on the high level side is set at a level where the ratio is 50%, and the set value k ₂ on the low level side is set at a level where the ratio S ₁ / S ₀ is 30%. Set value k ₁ high level side corresponds to the inflection point of the material curve, set value k ₂ of the low level side is set in the vicinity of the inflection point of the material curve.

If the measured value of the intensity level of the frequency within the frequency band from 200 to 400 Hz of the frequency spectrum input to the inflection point discriminating device 10 exceeds the set value k ₂ on the low level side, the vicinity of the inflection point of the material curve is determined to be, it is determined that the inflection point where the material curves further exceeds the set value k ₁ high level side.

Frequency band f of specific region₀~ F₁And this frequency
Set value k of frequency intensity in several bands ₁, K_Twoabout,
In or near the area where jumping occurs
Frequency analysis of the time series data of the rolling force
You can ask.

Depending on the line speed during temper rolling, the frequency band at which the strength level is increased slightly changes. By changing the set values k ₁ and k ₂ of the frequency intensity according to the line speed, the inflection point of the material curve can be grasped more accurately even if the line speed of the temper rolling changes.

In the above description, the frequency analysis is performed based on the time series data of the rolling force to determine the inflection point of the material curve. However, the time series data of the sheet thickness, the elongation rate or the roll gap is also used. The same applies to the case where the frequency analysis is performed to determine the inflection point of the material curve.

When the frequency intensity measured by the inflection point discriminating device 10 exceeds the set value k ₂ on the low level side, a signal is output to the alarm generating device 16 and an alarm is issued from the alarm generating device 16 to notify the operator. An alarm is issued by the alarm generator 16. While the frequency intensity is within the range of set values k ₁ set value k ₂ and the high-level side of the low-level side, the operator takes an action, such as the exit side tension and speed down, preventing the occurrence of the jumping phenomenon.

According to the present invention, the inflection point of the material curve can be accurately determined at the time of rolling in the low rolling region of wet rolling or the high elongation rolling region of dry rolling where the jumping phenomenon easily occurs. Based on this determination, the operator can take an action such as the output side tension or the speed reduction, so that the occurrence of a jumping phenomenon can be prevented, and the occurrence of quality abnormalities such as an abnormal elongation or an abnormal thickness can be prevented.

[0042]

According to the present invention, the inflection point of the material curve can be accurately determined. Based on this determination, the operator can take action such as changing the output side tension or reducing the speed at the inflection point, thereby preventing the occurrence of quality abnormalities such as abnormal elongation or abnormal thickness due to fluctuations in elongation. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram of a material curve showing a relationship between a roll gap and a rolling force in temper rolling.

FIG. 2 is a block diagram showing a control system of a temper rolling mill for describing an embodiment of the present invention.

FIG. 3 is a diagram showing time-series data of a measured value of a rolling force and a spectrum of a frequency component thereof.
(B) shows a frequency spectrum.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Temper rolling mill 2 Hydraulic pressure reduction device 3a Inlet bridle roll 3b Outlet bridle roll 4 Thickness gauge 6 Rolling load meter 7a Inlet bridle plate feed length 7b Outgoing bridle plate feed length 8 Elongation rate calculator 9 Frequency analyzer 10 Inflection point discriminator 16 Alarm generator S Steel plate

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2000-140917 (JP, A) JP-A-7-75803 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 37/00-37/78 B21B 1/00-1/46

Claims (3)

(57) [Claims] When performing temper rolling on a steel sheet after annealing, frequency analysis is performed based on time series data of any one of a thickness, an elongation, a rolling force, and a roll gap, and a frequency in a frequency band of a specific region is obtained. Determining the inflection point of the material curve at the time of temper rolling, wherein when the strength level of the steel sheet exceeds a preset value, it is determined that the inflection point is the inflection point of the material curve indicating the relationship between the roll gap and the rolling force. . 2. When temper rolling of an annealed steel sheet, frequency analysis is performed based on time series data of any one of a sheet thickness, an elongation, a rolling force, and a roll gap, and a frequency in a frequency band of a specific region is obtained. When the strength level of the material curve approaches a preset value, it is determined that the inflection point of the material curve at the time of temper rolling is determined to be near the inflection point of the material curve indicating the relationship between the roll gap and the rolling force. Method. 3. The inflection point judgment of the material curve at the time of the temper rolling according to claim 1 or 2, wherein the frequency band of the specific region is changed according to the line speed at the time of the temper rolling. Method.