JP2002254105A - Threading method for thin plate hot finishing roll mill and looper controlling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a threading method between stands of the tip end portion of a material and a looper controlling method of the tip end portion of the material capable of preventing the generation of an excessive material tensile force originating in the threading time of the tip end portion of the material between stands and in the above mentioned peculiar state immediately after the threading time or in the vicinity of the peculiar state in the thin plate hot finishing roll mill. SOLUTION: In the thin plate hot finishing roll mill provided with a looper 4 between stands 2, 3 when the tip end portion of the rolling material is threaded from the upstream side stand to the downstream side stand, the looper roll 12 rises from the standby position to the upper position than the pass line during the period from the time when the tip end portion of the rolling material passes through the upper part of the looper roll 12 to the time when the rolling material is engaged with the downstream side stand 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for passing a stand between a stand and a looper control method for a leading end of a rolled material (hereinafter referred to as "material") of a hot strip finishing mill, and more specifically to a method for controlling the leading end of a material. TECHNICAL FIELD The present invention relates to a method of passing a material between the stands at a front end portion of a thin sheet hot finishing rolling mill and a method of controlling a looper at the front end portion of the material, which are suitable for preventing shortage of the width of a material after rolling which occurs when a portion is passed between stands.

[0002]

2. Description of the Related Art A thin-plate hot finishing mill called a hot strip mill is composed of a plurality of (for example, 4 to 7) rolling mills (hereinafter, referred to as stands) arranged in tandem every 6 m, for example. . Usually, the rolled material on the entering side of the finishing mill called hot sheet bar is about 30 mm thick, about 700-210
It is 0mm wide, about 70m long and at about 1000 ° C. For this material, apply rolling reduction at each stand of the finishing mill,
In the final stand, the product is rolled to a predetermined product thickness of 1.2 to several mm. In order to achieve a finishing temperature of 850 ° C or higher, which is required on steel materials, high-speed rolling is performed at a maximum speed of about 1200 mpm.

In a hot finishing mill, as shown in FIG.
A looper roll 12 is attached to the end of the frame 11 between the stands.
And a buffer device 4 called a looper for forming an appropriate slack (loop) in the material 1 being rolled. This realizes that the material 1 is pushed up by the looper roll 12 to give an appropriate tension to the material 1 between the stands, so that the material 1 can run stably at the center of the rolling mill, and can be moved forward and backward (upstream and downstream). Breaking / breaking of material 1 by controlling the tension by moving up and down the looper roll 12 against over tension / no tension caused by imbalance of the volume velocity of the stand (approximately the product of the material thickness of the stand and the material velocity) This is to prevent intrusion.

Usually, the target (unit) tension to be controlled is 1 kg /
It is a little less than mm ^2. When the tension is reduced and decreased, the material is meandered, and when the tension is increased, the material width is reduced, and a width dimension defect called width necking as shown in the width chart of FIG. 2 is generated, thereby deteriorating the product yield.

[0005] In the finish rolling step, the tip of the sheet bar is passed through a group of stands of the above-mentioned rolling mill (this is referred to as a passing plate).
The operation is the most unsteady operation in the rolling of the entire length of the sheet bar, and is a difficult control regarding the product size.

A method of controlling a rolling mill and a looper at the time of threading in the prior art will be described below. The operator or the process computer predicts the elongation deformation of the stand and the material temperature due to the reaction force of the material for each stand of the finishing mill before passing through the sheet, and calculates the unloaded roll gap and roll speed of each stand. It is set (this is called a rolling mill preset), and the leading end of the material is sequentially bitten into each stand.

[0007] For example, a description will be given of a method of controlling a looper by passing a leading end portion of a material between an I stand and an I + 1 stand so as to be bitten by the I + 1 stand. FIG. 3 shows a state in which the material tip has passed through a looper roll between the I stand and the I + 1 stand. In FIG. 3, 1 is the material, 2 is the I stand, and 3 is
The I + 1 stand, 4 is a looper, 5 is a guide for guiding the leading end of the material to the roll bite of the I + 1 stand, and 6 is a looper control device. The looper 4 includes a frame 11 and a looper roll 12 disposed at the tip of the frame 11, and rotates the frame 11 around a looper rotation axis (not shown) to move the looper roll 12 up and down. 13 is a stopper (lower limit stopper).
θ is the looper angle, which is the elevation angle of the frame 11 from the horizontal plane.

The leading end of the material 1 that has exited the I stand 2 advances while being supported by the upper surface of the frame 11 of the looper 4 supported at the lower limit position by the stopper 13, passes through the looper roll 12, and guides the I + 1 stand 3 entering side Entered the roll bite at I + 1 stand 3 supported by 5.

The level connecting the front and rear stands 2 and 3 is called a pass line. The position of the stopper 13 is adjusted so that the standby height of the upper surface of the looper roll 12 at the time of passing the leading end of the material is near the pass line (but below the pass line). This means that when the looper roll 12 is at a position higher than the pass line,
This is because, while the material 1 exiting the machine is traveling at a high speed of about 10 m / s, the material 1 collides with the looper roll 12 and the material tip jumps up, making it difficult to enter the I + 1 stand 3. Looper angle θ of looper 4 supported at the lower limit position by stopper 13
Is usually about 5 to 8 degrees.

At the same time when the generation of the rolling reaction force of the I + 1 stand 3 is detected by the load cell 17b, the looper control device 6
A rising command is sent to the looper motor 14 of the looper 4 between 2 and 3, the looper roll 12 is first raised until the looper angle θ becomes a predetermined looper angle (target angle) θ ₀ , and then the material tension control is started. Incidentally, when the looper roll 12 of the looper 4 can not be increased is constrained to the material 1 to a predetermined looper angle theta _0, looper control system 6 may also starting the material tension control in a predetermined timer time after a backup . As the looper motor 14, an electric motor, a hydraulic motor, or the like is used.

The target angle θ ₀ is, for example, about 20 degrees, and is empirically set in consideration of the running stability of the material in the rolling mill, the tension controllability, and the like from the viewpoints described above.

The material tension is controlled by first detecting a material tension from a strain gauge 15 provided on a looper roll bearing (not shown) (this is referred to as a looper tension meter). Detect the looper angle. The speed of the rolling motor 18 of the I stand 2 and the torque of the looper motor 14 are controlled so that the detected actual tension and looper angle become the respective target values.

The effect of the positional relationship between the material 1 and the looper roll 12 on the material tension T will be described with reference to FIG. For simplicity of explanation, the looper roll 12 is the material 1
And the material 1 is running at an elevation angle β with respect to the pass line. From the geometric relationship, the following equation holds.

T = F / (2 sin β) (1) That is, the material 1 is bitten into both the front and rear stands, and the material 1 is not sagged on the pass line (that is, β = 0). When a force is applied from the looper roll 12, infinite material tension can be generated. This is called a singular state. Even without this singular state, a large material tension is generated at β ≒ 0 (near the singular state), and width necking occurs in the material 1. In particular, this phenomenon is remarkable in a thin material having a small material tension F as compared with the large inertia force of the looper.

In order to prevent this, as a passive method, the volume velocity of the front and rear stands (upstream and downstream) is not fixed at the time of presetting the rolling mill. It is also practiced to modify the volume velocity so as to be less than 1%. In this way, the material is passed between the stands in a loop-like manner, and the looper is raised at the point where no tension is generated to prevent the occurrence of a peculiar state. However, due to this modification, the occurrence of excessive loops at the time of passing the sheet increases, the timing of starting to follow the material of the looper roll 12 is delayed, and the start of the control of the material tension of the looper is delayed. There is a problem that occurs.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin-plate hot finishing mill in which excessive material tension is generated due to the above-mentioned peculiar state or near the peculiar state immediately after the front end of the material passes between the stands and during the plate passing. It is an object of the present invention to provide a method of passing a material between a stand and a looper control method of a material front end portion, which can prevent the occurrence of the problem.

[0017]

The means of the present invention for solving the above problems are as follows. (1) When passing the leading end of a rolled material from an upstream stand to a downstream stand in a sheet hot finishing rolling mill having a looper between stands, when the leading end of the rolled material passes through the upper portion of the looper roll, the leading end of the rolled material is transferred to the downstream stand. A thread passing method for a thin hot finishing rolling mill, wherein the looper roll is raised from a standby position to a position above a pass line before being bitten.

(2) In a thin sheet hot finishing rolling mill having a looper between stands, the looper roll is moved from the standby position to the pass line from the time when the leading end of the rolled material passes through the upper portion of the looper roll to the time when the leading end of the rolled material bites into the downstream stand. A looper control method for a hot strip rolling mill, comprising: raising a rolled material to an upper position;

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be specifically described with reference to FIG. In FIG. 5, reference numeral 6a denotes a looper control device. The same reference numerals are given to the other portions in FIG. 5 that have the same functions as the portions described in FIG. 3 described above. The present invention is to realize a looper roll following a material at an early stage by avoiding a singular state at the time of material passing, and to speed up the initial output timing of the looper tensiometer to speed up the start of material tension control. Yes,
As a result, it is possible to reduce the width defect of the overtensioned material tip.

More specifically, as shown in FIG.
When the leading end of the material passes through the upper part of the looper roll 12 when the material leading end is passed between the 2 and the I + 1 stand 3, the looper roll 12 is raised before the biting into the I + 1 stand 3 and the I + When the one stand 3 is bitten, the looper roll 12 is already located at a position that is considerably higher than the pass line.

The considerable amount mentioned here is preferably the target angle θ ₀ at the time of tension control. However, if the rise to the target angle θ ₀ cannot be made in time due to the relationship between the material speed and the looper drive system capability, it is possible during this time. Up to a certain height.

[0022] Consequently, at the same time biting into the material the tip of the I + 1 stand 3, looper angle theta is the target angle theta ₀ or target angle theta ₀ material tension control is effective and Nariru by looper 4 nearby. In addition, the singular state described above has been escaped. Also, when the volume velocity is unbalanced due to the error of the presetting of the rolling mill and that of I + 1 stand 3 becomes larger than that of I stand 2, that is, when passing through the plate with a slight tension, the frame 11 is Since it does not hit the stopper 13, the material tension has an advantage that the over tension is released mechanically by pushing down the looper roll 12.

The method of starting the looper up to the above-mentioned considerable height is not particularly limited in the present invention.
Various methods can be adopted. For example, the following methods can be exemplified, but the present invention is not limited to these methods.

For example, feedback control is performed by supplying a constant voltage to the looper torque motor and starting up, and operating the looper torque command value so as to maintain this height as soon as the height reaches the above-mentioned considerable amount. Alternatively, the material tension control may be started after the downstream stand is engaged.

Also, as in so-called bang-bang control, a maximum positive torque is commanded to the torque motor of the looper, and the position is switched to the maximum negative torque at a position half the height of the considerable amount, to reach the above-mentioned substantial amount of height. Later, feedback control for operating the looper torque command value so as to maintain this height may be performed, and the material tension control may be started after the downstream stand is engaged. It should be noted that, if the downstream stand bites before it rises to a considerable height, the material tension control starts immediately.

The threading method and the looper control method according to the present invention need not necessarily be performed between all of a plurality of rolling stands, but may be performed by selecting an appropriate stand where width necking easily occurs.

In the present invention, the method of controlling the material tension of the looper performed after the front end of the material is engaged with the downstream stand is not particularly limited. Various conventional methods can be employed. For example, a tension control method described in Japanese Patent Publication No. 02-030766 can be exemplified, but the present invention is not limited to this method.

When the looper roll pushes up the material after passing through the front end of the material, the material must bend downward and be supported by the guide to advance to the roll bite of the next stand. Assuming that the material length (overhang length) on the downstream side from the looper roll is L, the amount of deflection of the cantilever is proportional to the fourth power of L and inversely proportional to the square of the plate thickness according to the teaching of material mechanics. According to our calculations, L = 1000 mm and the sheet thickness is 4 m
At m, this deflection is about 60 mm. Considering that the distance between the looper roll and the next stand is 2000 mm or more in the actual machine, sufficient bending can be obtained with a thin material of 4 mm or less, which is a problem.

[0029]

EXAMPLE An example in which the method of the present invention is applied to a looper of a finish rolling mill will be described. In the present embodiment, the looper control method described in the embodiment of the present invention is applied to a looper between stands having a predicted inter-stand thickness of 4 mm or less, in which material width necking is likely to occur. For the other inter-stand looper, a conventional method, that is, a method in which a rise command is given to the looper for the first time when the material is caught in the downstream stand and tension control is performed by the looper is applied.

First, the characteristics of the looper to which the method of the present invention is applied (the looper 4 between the I stand 2 and the I + 1 stand 3 shown in FIG. 5) under no load were examined. The dead time τ until the start of the rising of the frame 11 of the looper 4 when the looper control device 6a issues a rising command to the looper 4 is obtained,
The rotational angular velocity ω at a looper angle θ of around 15 degrees was determined. In the measurement example of the inventors, τ = 0.2 sec and ω = 7 degrees / sec.

The looper control device 6a has τ obtained above,
ω data, distance between I stand 2 and looper roll 12
d ₁ , data of the distance d ₂ between the looper roll 12 and the I + 1 stand 3, and a target angle θ _{0 of the} looper preset based on the material size, the rolling speed, and the like are input.

When the looper controller 6a detects that the load cell 17a has caught the material into the I-stand 2, the looper controller 6a is supported by the stopper 13 and the standby angle θs of the looper 4 at the standby position.
Is measured. Next, the material speed Vi on the exit side of the I stand 2 is calculated by multiplying the peripheral speed of the rolling roll of the I stand 2 detected by the tachometer 19 by the advance ratio. Also based on the distance d ₁ between the I stands 2 and looper roll 12, calculates the time to reach looper roll 12 of material tip _{Tr (= d 1 / Vi)} , further (Tr-tau) seconds after the looper roll 12 is substantially The rising command timer is set so that the rising starts. Further, based on the distance d ₂ between the looper roll 12 and the I + 1 stand 3, and calculates the increase target angle theta _t of the looper 4 at the time of rise command by the following equation. θ _t = Min (θ ₀ , (θs + ωd ₂ / Vi)) (2) That is, when the material speed is low, it is requested that the looper 4 be raised to the target angle θ ₀ at the time of the tension control, and the material speed is If the speed is fast, the looper 4 is raised as far as possible until just before the tip of the material bites into the I + 1 stand 3.

After (Tr-τ) seconds, the calculation result is instructed to the looper motor 14, and the looper roll 12 is raised.
Starts materials tension control of the looper 4 as the target angle theta ₀ at the same time the material tip biting I + 1 stand 3.

As a result of implementing the method of the present invention, the looper roll lifts the material constrained by both stands at the tip end of the material generated by the conventional threading method, causing the looper roll to lift up from below (in some cases, a collision phenomenon) and a unique state. The resulting necking phenomenon of the width could be greatly reduced.

Further, as a result of implementing the method of the present invention, the material is pulled from the rear by the riser of the looper roll before the leading end portion of the material is bitten into the downstream stand, so that the material is uniformly bittened to the downstream stand in the width direction. Realize
There was also obtained a secondary effect that operation abnormalities such as end bending due to flapping of the material shown in 6 can be reduced as compared with the conventional threading method.

Although the above-described embodiment of the present invention is a basic example of the embodiment of the present invention, one or two of the following adjustment methods are adjusted according to the characteristics of each finishing mill. It is also possible to combine the above.

1. After the leading end of the material passes through the position of the looper roll 12 and is sufficiently separated from the looper roll 12,
To prevent the running of the material tip from being hindered. For example, in the formula Tr = d ₁ / Vi for calculating an arrival time until the looper roll 12 of material tip _{Tr (= d 1 / Vi)} , d 1
And (d ₁ + δ). Here, δ is the material tip when moving up the looper roll 12 and the looper roll 12.
Is, for example, δ = 500 mm.

2. Considering the dispersion of the processing and signal transmission delays of the controller and the measuring device, the substantial start-up timing of the looper roll 12 is set after the material tip has definitely passed, and the material tip is engaged with the downstream stand 3 Sometimes it is necessary that the rising of the looper roll 12 has been completed.
For example, it is necessary to calculate d ₂ in equation (2) as (d ₂ −Δ), where Δ is a margin, for example, Δ = 500 mm.

[0039] 3. For tip bounce preventing the increase target angle theta _t of the looper at elevated command to looper during the sheet passing,
Keep a few degrees above the pass line to avoid falling into the toughest range of singularities.

[0040]

According to the present invention, it is possible to avoid a peculiar state at the time of material passing and to make the looper roll follow the material at an early stage, so that the width necking due to over tension at the leading end of the rolled product is greatly reduced. it can.

Further, since the material is pulled from behind by the rise of the looper roll before the leading end of the material bites into the outlet stand, the material is uniformly bittened into the outlet stand in the width direction. As compared with the conventional threading method, it is possible to reduce operation abnormalities such as end breaking due to flapping of the material.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an arrangement of a main part of a looper installed between stands of a hot rolling mill.

FIG. 2 is a diagram illustrating an example of a width chart of a strip in which width necking has occurred.

FIG. 3 is a diagram illustrating a state in which a leading end portion of a material is passed between stands including a looper and a looper control system in the related art.

FIG. 4 is a schematic diagram illustrating a relationship between a pushing force F from a looper roll to a material and a material tension T.

FIG. 5 is a diagram illustrating a situation in which a leading end of a material is passed between stands provided with a looper and a looper control system in the method of the present invention.

FIG. 6 is a view for explaining a trouble of passing a plate between ends of a material front end portion (end bending).

[Explanation of symbols]

 1 Material (hot rolled material) 2 I stand 3 I + 1 stand 4 Shock absorber (looper) 5 Guide 6, 6a Looper controller 11 Frame 12 Looper roll 13 Stopper (lower limit stopper) 14 Looper motor 15 Strain gauge 16 Angle meter 17a, 17b Load cell 18 Rolling motor 19 Tachometer θ Looper angle

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoyuki Kato 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Masahiro Yonezawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) The inventor, Tsutomu Takahara, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan

Claims (2)

[Claims] When a leading end of a rolled material is passed from an upstream stand to a downstream stand in a thin sheet hot finishing rolling mill having a looper between stands, the leading end of the rolled material passes from the upper side of the looper roll to the downstream side. A thread passing method for a thin hot finishing rolling mill, wherein a looper roll is raised from a standby position to a position above a pass line before being bitten by a stand. 2. A sheet hot finishing rolling mill having a looper between stands, wherein the looper roll is moved from a standby position to a position above a pass line from the time when the leading end of the rolling material passes through the upper part of the looper roll to the time when the rolled material bites into the downstream stand. And controlling the material tension with a looper after the rolled material has caught the downstream stand and reached the position of the rolled material.