JPH0534092B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method for preventing the occurrence of squeezing of a steel strip on the entry side of a rolling mill, and particularly to a method that is extremely effective in preventing squeezing of a steel strip in a hot finishing tandem rolling mill. Conventional technology and its problems Hot finishing tandem rolling mill rolls a wide width (for example 1200 mm)
When rolling thin steel strips (for example, finished thickness 1.6 mm or less), the leading and trailing ends of the steel strip tend to come to the drive side or work side of the rolling mill during rolling, and in this case, the inlet side The steel band is pressed against the guide and bent, eventually causing a squeezing accident. This squeezing accident causes major damage to the rolls, forcing roll replacements, reducing productivity and increasing roll consumption.
It is desirable to prevent this from happening as it causes a decline in quality. The reason why the tip and rear ends of the strip tend to lean toward the drive side or work side of the rolling mill is that, taking the rear end of the strip as an example, it is restrained by the front stand rolls until the end of the front stand comes out, but the front end This is due to the fact that the previous stand is no longer restrained from the time the end of the stand exits until the end of the next stand exits. By the way, recently there has been a growing trend to introduce rolling mills with profile control means in the last three to four stands of hot tandem rolling mills for the purpose of improving the thickness distribution in the width direction (plate profile) of hot-finished strip steel. I'm getting used to it. As a rolling mill with this profile control means, for example, a 6-high mill (HC mill) or a 4-high mill in which the intermediate roll can be moved in the axial direction of the roll can be moved in the axial direction according to the width of the strip being rolled. There are known rolling mills (usually called work shift mills) that improve the sudden drop in plate thickness (referred to as edge drop), especially at the edges of the plate, by moving the workpiece. In the case of these rolling mills, compared to ordinary 4-high rolling mills, if there is a misalignment (off-center) between the center of the strip width and the center of the rolling mill roll body length, the parallelism of the upper and lower work rolls tends to be disturbed. Motsu. For this reason,
If such a roll shift mill is used for rolling the wide thin material, even the slightest occurrence of off-center will disturb the parallelism of the upper and lower work rolls, resulting in a difference in elongation between the right and left sides in the width direction of the steel strip. This difference in elongation between the left and right sides causes a camber in the steel strip, which disturbs the angle at which the steel strip enters the rolls on the entry side of the rolling mill, resulting in a further increase in the off-center amount. Due to such an unstable phenomenon, the steel strip is pressed against the entry side guide, and eventually the strip is squeezed by the entry side guide. That is, in order to prevent such squeezing accidents during strip rolling, it is important to prevent so-called meandering of the strip during rolling. As a method to prevent this meandering of the steel strip, for example,
No. 51771 proposes a method for controlling the meandering of a steel strip during rolling by using the difference between the measured rolling loads on the left and right sides. However, in the case of an actual rolling mill, the difference in rolling load between the left and right sides is greater than a certain amount of off-center (for example, 20 mm).
Since it is difficult to detect unless it occurs (more than a certain degree),
The meandering control method described above cannot be said to be effective in preventing squeezing caused by meandering, especially for thin and wide materials. Further, Japanese Patent Publication No. 59-5366 proposes a method of adjusting the rolling reduction amount of a rolling mill by detecting the pressure applied to a side guide at the entrance of the rolling mill. This method is
A pressure detector is provided in the side guide, and the amount of roll reduction is controlled by the contact pressure value signal of the edge of the strip detected by the pressure detector, thereby controlling the meandering. In this method, when the strip moves to the work side or the drive side and comes into contact with the side guide, the rolling screw on the side that made contact is tightened, which reduces the average strip thickness in the width direction on the exit side of the rolling mill. This will cause inconvenience. Also, if there is a camber etc. in the steel strip on the entrance side of the rolling mill and the strip enters diagonally to the roll axis,
Pressure may be applied to the side guides on both the work side and drive side at the same time, and in this case, the rolling screws on both the work side and drive side must be tightened, resulting in an even thinner average sheet thickness at the exit side of the rolling mill. This will cause inconvenience. In addition, although the rolling speed in the 3rd to 4th stands in the latter stage of the finishing mill is usually high, at 300 m/mm or more, the response is slow because an electric motor is used to control the rolling reduction, making it difficult to prevent rolling. be. OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to propose a method capable of reliably preventing narrowing of the steel strip during rolling. Structure of the Invention A method for preventing squeezing in strip rolling according to the present invention includes installing load cells on left and right side guides on the entrance side of a strip rolling mill, and detecting loads in the strip width direction applied to the side guides with the left and right load cells. Then, when the difference between the load cell output values is greater than or equal to a preset dead band width, the roll parallelism correction amount of the rolling mill is determined, and the left and right roll reduction amounts are adjusted in opposite directions based on the roll parallelism correction amount. It is characterized by: In other words, this invention uses a load detector (load cell) instead of a mere pressure detector as a means for detecting the load in the strip width direction applied to the side guide, and detects the meandering tendency of the steel strip during rolling by detecting the difference between the output values of the left and right load cells. This is a method of preventing narrowing down by correcting the parallelism of the upper and lower roll gaps when the difference between the output values exceeds a certain value. In the method of this invention, the inventors used a load cell as a means for detecting the load in the width direction of the plate applied to the side guides, as a result of studies including model rolling experiments and actual rolling tests. This is because it is more practical to detect the force in the plate width direction applied to the side guide with a load cell than with a pressure detector. In this invention, the load cells described above are attached to the left and right side guides at the entrance of the rolling mill, and the load in the width direction of the plate applied to the side guides during rolling is detected by the left and right load cells, and the difference between the output values of both load cells is determined.
Then, when the difference between the output values is greater than or equal to the dead band width, the roll parallelism correction amount of the rolling mill is determined. Note that the dead band width is a dead band width often used in automatic control, and within this width, stability of automatic control can be ensured by not outputting a control output. here,
The dead band width is determined from a built-in table according to the width and thickness of the strip at the entrance to the rolling mill. In this case, it is desirable to keep the dead band width small because the thinner the plate thickness and the wider the plate width, the more likely it is that constriction will occur. The specific method for determining the dead band width is determined by correcting table values corresponding to each strip width and thickness through trial and error while observing actual rolling conditions. Below, as an example, the entrance side plate thickness is 3 mm, the entrance side plate width is
This shows how to find the dead band width in the case of 1000mm. First, let us assume that the dead band width R _D for this size is 600 kg. When rolling a rolled material with the above dimensions, the difference ΔF between the output values of the left and right side guide load cells measured during rolling was detected to be +500 kg, so no reduction correction was performed when ΔF< _RD . However, as a result, the rolled material was squeezed at the rear end. This indicates that the previously assumed dead band width R _D =600Kg was excessive.
Therefore, R _D was revised to 1/2 to 300Kg. On the other hand, when rolling a rolled material with the same dimensions on another stand, ΔF = +400Kg, and in this case, when the reduction correction amount ΔS is calculated using formula (1) described later, ΔS = +0.10mm.
When the rolling reduction amount was corrected accordingly, meandering occurred in the rolled material and control became unstable.
This was because the dead band width R _D was set too low, and based on this result, R _D was revised to 450 kg, and stable rolling was subsequently possible with this value. The table below shows an example of determining the dead band width R _D for other rolled material entrance dimensions (plate thickness, plate width) using such a trial and error method.

[Table] In addition, the roll parallelism correction amount is calculated by taking into account rolling conditions such as the dimensions and rigidity of the rolling mill, rolling reduction, plate width, and hardness of the rolled material. A specific example of how to obtain the roll parallelism correction amount is shown below. ΔS=ΔF・(A ₁・D _M +A ₂・K _M +A ₃・r+A ₄・B+A ₅・kjw) ……(1) Formula where, ΔS: Roll parallelism correction amount ΔF: Output amount of left and right load cells Difference D _M : Work roll diameter of the mill K _M : Rigidity value as seen from the roll gap of the mill (mill spring value) r: Reduction ratio in the rolling pass B: Inlet plate width of the rolled material kjw: Average deformation resistance value of the rolled material A ₁ , A ₂ , A ₃ , A ₄ , and A ₅ are constant coefficients, which are determined in advance by a rolling test. Once the roll parallelism correction amount is determined in this way, this roll parallelism correction amount is applied to the left and right lowering devices, and although not limited to this invention, a hydraulic pressure reducing device with a fast response speed, to adjust the parallelism of the upper and lower rolls. Fix it. When correcting this roll parallelism,
In order to suppress the change in the average plate thickness in the width direction at the exit side of the rolling mill, the correction amount is divided by 1/2 on the left and right sides, and the roll reduction amounts on the left and right sides are adjusted in opposite directions. Next, the method of this invention will be explained based on the apparatus shown in FIGS. 1 and 2. 1 and 2 show an example of an apparatus for carrying out the method of the present invention, in which a steel strip 1 is guided by an entry side guide 3 and rolled by work rolls 2a and 2b of a rolling mill 2. There is. The entrance side guide 3 has a pair of left and right guide plates 3-1 each supported by a guide support stand 3-2 with a side guide guide 3-3 having a built-in ball slide bearing etc. so as to be able to move in and out in the width direction of the steel strip. The meandering tendency of the steel strip during rolling is detected by load cells 3r and 3l installed between each guide plate 3-1 and guide support stand 3-2. In addition,
side guide guide 3-3 and load cell 3r,
From the viewpoint of accuracy in detecting load in the plate width direction, it is desirable that the center of 3l coincides with the height of the strip rolling pass line as much as possible. In Fig. 2, 4 is the left and right load cell 3r, 3
5 is a calculation device for calculating the amount of roll parallelism correction; 6r and 6l are rolling devices on the left and right sides of the rolling mill 2. Function In the above device, when the loads F _R and F _L applied from the strip steel 1 to the left and right side guides 3-1 are detected by the load cells 3r and 3l during rolling, the difference ΔF between the output values of both load cells is detected by the operational amplifier. Calculated in 4,
The value is input to the arithmetic device 5. The calculation device 5 compares the dead band width R _D obtained from the built-in tape according to the pre-given width and thickness of the strip at the entrance side of the rolling mill with the magnitude of the above ΔF, and calculates that ΔF> If R _D , the roll parallelism correction amount ΔS of the rolling mill is determined using the value of ΔF using the above equation (1). Then, the obtained roll parallelism correction amount ΔS is applied to the left and right lowering devices 6r and 6l, respectively.
The parallelism of the upper and lower rolls is corrected by dividing them into two parts and issuing commands. For example, if ΔF>0 (large tendency to shift to the left), the roll parallelism is corrected in opposite directions for the left roll gap by ΔS/2 in the tightening direction and by ΔS/2 in the opening direction for the right roll gap. In addition, if ΔF≦R _D ,
A signal of ΔS=0 is sent to the rolling down device and the roll parallelism is not corrected. By the way, as a result of actually performing hot rolling by installing the above-mentioned method of this invention in the latter three stands of a hot strip steel finishing tandem rolling mill, we found that the finished thickness was 1.6 mm or less.
The number of accidents caused by thin wide materials with a width of 1,100 mm or more was reduced to about 1/4 compared to the conventional method, confirming the effectiveness of the method of this invention. Effects of the invention As explained above, according to the method of the invention,
By adopting a method that uses a load cell to detect the meandering tendency of the steel strip in the width direction of the strip, it is possible to measure the load applied to the side guides in a practical and accurate manner. By using a dead band value that is set according to the thickness and strip width, it is possible to stabilize the control of the roll reduction amount, and to keep the rolls parallel to each other so that the average strip thickness in the width direction at the exit side of the rolling mill does not change. Since the degree can be corrected, it is possible to greatly reduce squeezing accidents even with wide thin sheets, and it is possible to improve productivity and roll consumption.

[Brief explanation of drawings]

FIG. 1 is a partial side view showing an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a plan view showing the overall structure of the same apparatus. DESCRIPTION OF SYMBOLS 1... Steel strip, 2... Rolling machine, 3... Side guide, 3-1... Guide plate, 3-2... Guide support stand, 3-3... Side guide guide, 3r, 3l...
...Load cell, 4... Arithmetic amplifier, 5... Arithmetic mounting, 6r, 6l... Lowering device.

Claims (1)

[Claims] 1 Load cells are installed on the left and right side guides on the entrance side of the strip rolling mill, and the load in the strip width direction applied to the side guides is detected by the left and right load cells, and the difference between the output values of the load cells is determined as a preset dead band width. A method for preventing squeezing in strip steel rolling, which comprises determining the roll parallelism correction amount of the rolling mill in the above case, and adjusting the left and right roll reduction amounts in mutually opposite directions based on the roll parallelism correction amount.