JP2004314160A - Method for drawing cast billet in continuous casting equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for drawing a cast billet in continuous casting equipment by which the cast billet can be drawn at a regular speed by preventing a fluctuation in the casting speed of the cast billet. <P>SOLUTION: In the method for drawing the cast billet for drawing the cast billet at the regular speed by means of a plurality of pairs of pinch rolls in the continuous casting equipment, the speeds of driving motors 14a, 15a to 14c, 15c are respectively independently controlled for all the pinch rolls 10a, 11a to 10c, 11c and the presence or absence of the fluctuation in the cast billet drawing speeds due to mechanical backlash is detected from the summation of the driving motor currents of all the pinch rolls 10a, 11a to 10c, 11c and the torque or speed control of the driving motors 14a, 15a to 14c, 15c for all the pinch rolls 10a, 11a to 10c, 11c is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

Ｔａ、ＴｂおよびＴｃ：図１に示すピンチロールの引抜トルク
Ｔｍ：鋳型振動摩擦力をピンチロール引抜トルクに換算した値
Ｔｐ：全ピンチロールの無負荷回転トルク
α、β：調整代
まず、全ピンチロールを速度制御で運転開始する。ついで、全ピンチロール１０ａ、１１ａ〜１０ｃ、１１ｃの合計トルクの監視を開始し、全ピンチロールの電流値の総和から鋳片引抜に必要なトルクＴを算出する。
【００１５】
▲１▼ Ｔ＜Ｔａの場合、全ピンチロール１０ａ、１１ａ〜１０ｃ、１１ｃをそれぞれ速度制御する。この状態では、各ピンチロール１０ａ、１１ａ〜１０ｃ、１１ｃは、安定して制動側トルクで運転され、機械バックラッシュによる速度変動は発生しない。
▲２▼ Ｔａ≦Ｔ＜Ｔｂの場合、ピンチロール１０ａ、１１ａをトルクＴｘでトルク制御（引抜側）し、その他のピンチロール１０ｂ、１１ｂ、１０ｃ、１１ｃをそれぞれ速度制御する。ピンチロール１０ａ、１１ａは引抜側トルク、その他のピンチロール１０ｂ、１１ｂ、１０ｃ、１１ｃは制動側トルクで安定して運転され、機械バックラッシュによる速度変動は発生しない。
▲３▼ Ｔｂ≦Ｔ≦Ｔｃの場合、ピンチロール１０ａ、１１ａをトルクＴｙでトルク制御（制動側）し、その他のピンチロール１０ｂ、１１ｂ、１０ｃ、１１ｃを速度制御する。ピンチロール１０ａ、１１ａは制動側トルク、その他のピンチロール１０ｂ、１１ｂ、１０ｃ、１１ｃは引抜側トルクで安定して運転され、機械バックラッシュによる速度変動は発生しない。
▲４▼ Ｔｃ＜Ｔの場合、全ピンチロール１０ａ、１１ａ〜１０ｃ、１１ｃを速度制御する。この状態では、各ピンチロール１０ａ、１１ａ〜１０ｃ、１１ｃは、安定して引抜側トルクで運転され、機械バックラッシュによる速度変動は発生しない。
全ピンチロールの合計トルクＴを常に監視し、合計トルクＴの変動に対応して▲１▼〜▲４▼の制御を実施する。
【００１６】
上記鋳片引抜方法において、全ピンチロール１０ａ、１１ａ〜１０ｃ、１１ｃの合計トルクＴを監視し、合計トルクＴの変動に対応してピンチロール１０ａ、１１ａの制御を上述のように変更することにより、鋳造条件（鋳造サイズ、鋳造速度、冷却条件、設備状況）の大きな変動に対して、機械バックラッシュ起因の引抜速度変動を防止できる。また、機械バックラッシュ起因の速度変動が生じない条件下での鋳造において、不要な負荷が作用することを防止でき、電力が節減される。ピンチロール群に必要とされる引抜能力を削減できる。さらに、上記▲２▼と▲３▼の条件区分を設けることによりピンチロール１０ａ、１１ａの必要トルク能力を削減できる。
【００１７】
本発明は上記実施の形態に限られるものではない。例えば、ピンチロールは４対以上あってもよく、トルクおよび速度制御可能なピンチロールは２対以上あってもよい。
【００１８】
【発明の効果】
本発明の効果は、次のとおりである。
鋳片引抜速度変動の発生を予知し、速度変動を未然に防止することができる。
ピンチロール駆動系の機械バックラッシュ起因の引抜速度変動を防止することができる。その結果、鋳型駆動と鋳片との相対速度を正常に保ち、かつ速度変動起因による湯面レベル変動を抑制することによって鋳片の表面性状が安定し、表面品位が向上する。
機械バックラッシュ起因の速度変動が発生しない条件下では全ピンチロールを速度制御とし、各ピンチロールに余分な負荷が作用することを防止する。この結果、省電力化、設備仕様の削減（ピンチロール引抜能力を最小化）が可能となった。
【図面の簡単な説明】
【図１】本発明の引抜装置の一例を模式的に示す装置構成図である。
【図２】本発明の鋳片引抜方法の手順を示すフローチャートである。
【図３】ピンチロール駆動装置の機械バックラッシュに起因する引抜速度変動の発生メカニズムを説明する図面である。
【符号の説明】
１ 鋳片 ５ 案内支持ロール群
１０、１１ ピンチロール １２、１３ 駆動機械系
１４、１５ 駆動モーター １６、１７ 制御装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a slab drawing method in a continuous casting facility.
[0002]
[Prior art]
In a continuous casting facility for steel slabs, depending on casting conditions, fluctuations in slab withdrawal speed occur due to mechanical backlash of a pinch roll drive system. Fluctuations in the slab drawing speed cause deterioration of the surface quality, so it is necessary to minimize fluctuations in the slab drawing speed.
[0003]
The slab drawing speed fluctuation due to the mechanical backlash occurs as follows. As shown in FIG. 3, the slab S is being drawn, the slab's own weight (slab drop force) W is applied downward, and the total extraction resistance R by the guide support roll group 5 is applied upward. Further, a mold vibration friction force is applied to the slab S upward or downward depending on the vibration direction. The pinch roll 10 supports cast slab dropping when the cast slab weight W is greater than the total pull resistance R, and pulls the cast slab when it is small.
[0004]
When the slab's own weight W and the total pull-out resistance R are substantially equal, the load on the pinch roll becomes small, and the load becomes almost no load. In such a case, the mold vibration friction force is transmitted to the pinch roll 10, and when the mold 1 is vibrating down, the slab S precedes the rotation of the pinch roll drive motor by the mechanical backlash. That is, the slab S falls faster than the originally set original drawing speed. Further, when the mold 1 is at the time of vibration rise, the slab S does not receive the driving force of the pinch roll 10 until the rotation of the motor catches up with the mechanical backlash, and is almost stopped. As a result, the slab S repeatedly drops and stops, and the slab withdrawal speed fluctuates.
[0005]
As a technique for suppressing the fluctuation of the slab drawing speed, for example, there is a method of arranging a plurality of pairs of pinch rolls and controlling the rotation speed of each pinch roll by a drive control device so as to be different from each other. In this method, a torque in a fixed direction is applied to each pinch roll, so that even if load fluctuation of the pinch roll is generated, speed fluctuation due to backlash does not occur (for example, see Patent Document 1).
[0006]
However, the above method has no means for detecting the occurrence of the drawing speed fluctuation caused by the mechanical backlash, and even under the condition where the speed fluctuation does not occur, the extra load due to the difference in the rotation speed command between the pinch rolls acts. Will do. Therefore, power consumption increases and excessive pinch roll capability is required. Further, a rotation speed command different from the original pulling speed is given to each pinch roll, and the torque generated between the pinch rolls is controlled in a certain direction. As a result, the original drawing speed control becomes difficult and complicated, and when the required slab drawing torque changes due to a change in casting conditions, the load balance of each pinch roll changes, and the actual slab drawing speed also changes.
[0007]
[Patent Document 1]
JP-A-63-215359 (see page 2, upper left column)
[0008]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a method for drawing a slab in a continuous casting facility capable of preventing a change in a slab drawing speed and capable of drawing a slab at a constant speed. I have.
[0009]
[Means for Solving the Problems]
The present inventor has clarified that the drawing speed fluctuation caused by the mechanical backlash of the drive system of the pinch roll as described above occurs when the total drawing resistance R and the slab weight W of the continuous casting machine are substantially balanced. did. Further, torque control is performed on at least one pair of pinch rolls out of a plurality of pairs of pinch rolls only under conditions where speed fluctuations due to mechanical backlash occur, and each pinch roll can be operated stably with a torque in a certain direction. Was found. The present invention has been made based on these findings.
[0010]
The slab pulling method in the continuous casting facility of the present invention is a slab pulling method in which the slab is drawn at a constant speed by a plurality of pairs of pinch rolls in the continuous casting facility. And controlling whether the slab pull-out speed has fluctuated due to mechanical backlash from the sum of the drive motor currents of all pinch rolls, and controlling the torque or speed of the drive motors of the pinch rolls. According to the slab drawing method, it is possible to predict the occurrence of the slab drawing speed fluctuation and prevent the speed fluctuation from occurring.
[0011]
In the above slab drawing method, when a change in the slab drawing speed is detected, at least one pair of pinch roll drive motors can be torque controlled, and the other pair of pinch roll drive motors can be speed controlled. By this method, even when the pulling force required for the pinch roll fluctuates greatly due to fluctuations in casting conditions, the load on the pinch roll is stabilized in the braking direction or on the pulling side so that the load on the pinch roll is fixed. Since it is stable, it is possible to prevent fluctuation of the slab drawing speed due to mechanical backlash.
[0012]
Further, in the above slab drawing method, a total torque T required for slab drawing is obtained from a sum of drive motor currents of all the pinch rolls.
−Tm + Tp ≦ T ≦ Tm + Tp
Here, Tm: a value obtained by converting the mold vibration frictional force into a pinch roll pulling torque Tp: it is determined that a fluctuation in the slab pulling speed due to the mechanical backlash has occurred at the no-load rotation torque of all the pinch rolls, The torque or speed of the drive motor of each pinch roll may be controlled. According to this method, it is possible to determine whether or not the speed fluctuation has occurred, based on whether or not the total torque T required for slab drawing calculated from the total sum of all the pinch roll drive motors is within the range of the above expression.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 schematically shows a slab drawing apparatus for performing the slab drawing method of the present invention. The slab drawing device includes three pairs of pinch rolls 10a, 11a, 10b, 11b, 10c, 11c that apply a drawing force to the slab S. The pinch rolls 10a, 11a to 10c, 11c are connected to drive motors 14a, 15a to 14c, 15c via drive mechanical systems 12a, 13a to 12c, 13c including a reduction gear, a joint, and the like. The drive motors 14a, 15a of the pinch rolls 10a, 11a are connected to torque / speed control devices 16a, 17a capable of controlling torque and speed. The speed controllers 16b, 17b, 16c, 17c are connected to the drive motors 14b, 15b, 14c, 15c of the other pinch rolls 10b, 11b, 10c, 11c, respectively.
[0014]
Here, a slab drawing method using the slab drawing apparatus configured as described above will be described with reference to the flowchart shown in FIG. In FIG. 2,

Ta, Tb and Tc: pulling torque of pinch roll shown in FIG. 1 Tm: value obtained by converting mold vibration friction force into pinch roll pulling torque Tp: no-load rotation torque of all pinch rolls α, β: no adjustment allowance, all pinches Start the roll with speed control. Then, monitoring of the total torque of all the pinch rolls 10a, 11a to 10c, and 11c is started, and the torque T required for drawing the slab is calculated from the sum of the current values of all the pinch rolls.
[0015]
{Circle around (1)} When T <Ta, all the pinch rolls 10a, 11a to 10c, 11c are speed-controlled respectively. In this state, the pinch rolls 10a, 11a to 10c, and 11c are stably operated at the braking torque, and no speed fluctuation occurs due to mechanical backlash.
{Circle around (2)} When Ta ≦ T <Tb, the pinch rolls 10a and 11a are torque-controlled (pull-out side) by the torque Tx, and the other pinch rolls 10b, 11b, 10c and 11c are speed-controlled respectively. The pinch rolls 10a and 11a operate stably with the pull-out torque and the other pinch rolls 10b, 11b, 10c and 11c operate stably with the braking torque, and there is no speed fluctuation due to mechanical backlash.
{Circle around (3)} When Tb ≦ T ≦ Tc, the pinch rolls 10a and 11a are torque-controlled (braking side) by the torque Ty, and the other pinch rolls 10b, 11b, 10c and 11c are speed-controlled. The pinch rolls 10a and 11a operate stably with the braking torque, and the other pinch rolls 10b, 11b, 10c and 11c operate stably with the pull-out torque, and there is no speed fluctuation due to mechanical backlash.
{Circle around (4)} When Tc <T, all the pinch rolls 10a, 11a to 10c, 11c are speed-controlled. In this state, the pinch rolls 10a, 11a to 10c, and 11c are stably operated at the pull-out torque, and no speed fluctuation occurs due to mechanical backlash.
The total torque T of all the pinch rolls is constantly monitored, and the control of (1) to (4) is performed according to the fluctuation of the total torque T.
[0016]
In the above slab drawing method, the total torque T of all the pinch rolls 10a, 11a to 10c, and 11c is monitored, and the control of the pinch rolls 10a and 11a is changed as described above in accordance with the fluctuation of the total torque T. With respect to large fluctuations in casting conditions (casting size, casting speed, cooling conditions, equipment conditions), it is possible to prevent a drawing speed fluctuation caused by mechanical backlash. Further, in casting under a condition in which speed fluctuation due to mechanical backlash does not occur, it is possible to prevent an unnecessary load from acting, thereby saving power. The pull-out capacity required for the pinch roll group can be reduced. Further, by providing the above conditions (2) and (3), the required torque capacity of the pinch rolls 10a and 11a can be reduced.
[0017]
The present invention is not limited to the above embodiment. For example, there may be four or more pairs of pinch rolls, and two or more pairs of pinch rolls capable of controlling torque and speed.
[0018]
【The invention's effect】
The effects of the present invention are as follows.
It is possible to predict occurrence of a slab drawing speed variation and prevent the speed variation before it occurs.
It is possible to prevent a change in the drawing speed caused by mechanical backlash of the pinch roll drive system. As a result, the relative speed between the mold drive and the slab is kept normal, and the fluctuation of the molten metal level caused by the speed fluctuation is suppressed, whereby the surface properties of the slab are stabilized and the surface quality is improved.
Under conditions in which speed fluctuations due to mechanical backlash do not occur, all pinch rolls are speed controlled to prevent an extra load from acting on each pinch roll. As a result, it has become possible to save power and reduce equipment specifications (minimize pinch roll pull-out capability).
[Brief description of the drawings]
FIG. 1 is a device configuration diagram schematically illustrating an example of a drawing device of the present invention.
FIG. 2 is a flowchart showing a procedure of a slab drawing method of the present invention.
FIG. 3 is a view for explaining a mechanism of generating a drawing speed fluctuation caused by a mechanical backlash of the pinch roll driving device.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 cast piece 5 guide support roll group 10, 11 pinch roll 12, 13 drive mechanical system 14, 15 drive motor 16, 17 controller

Claims (3)

A slab drawing method in which a slab is drawn at a constant speed by a plurality of pairs of pinch rolls in a continuous casting facility, wherein the drive motors are independently controlled for all the pinch rolls, and the sum of the drive motor currents of all the pinch rolls A method for extracting slabs in a continuous casting facility, comprising detecting presence or absence of a change in slab extraction speed due to mechanical backlash, and controlling torque or speed of a drive motor of a pinch roll. 2. The slab drawing in the continuous casting equipment according to claim 1, wherein when a change in the slab drawing speed is detected, the drive motors of at least one pair of pinch rolls are torque-controlled, and the drive motors of the other pair of pinch rolls are speed-controlled. Method. From the total sum of the driving motor currents of all the pinch rolls, a total torque T required for slab drawing is obtained,
−Tm + Tp ≦ T ≦ Tm + Tp
Here, Tm: a value obtained by converting the mold vibration frictional force into a pinch roll pulling torque Tp: a request for determining that the fluctuation of the slab pulling speed due to the mechanical backlash has occurred when the no-load rotation torque of all the pinch rolls. 3. A method for drawing a slab in a continuous casting facility according to claim 1 or 2.

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