JPS6138721Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a control device for a mandrel bar insertion machine in an SFM (semi-float type mandrel mill).

It has a conventional pair of grooved rolls, and has multiple stands with the roll positions of the odd and even stands shifted by 90 degrees.A mandrel bar is inserted into the raw pipe that is the material to be rolled, and the rolls are inserted between the rolls. The continuous steel pipe rolling mill that reduces the wall thickness of raw pipe is called FFM (Full Float Mandrel Mill). In this type of product, a mandrel bar is inserted into the raw tube to be rolled on the input side of the mandrel mill, and the mandrel bar and the raw tube are inserted into the mill and rolled. That is, in such a mill, there is no restraint device for holding the mandrel bar in a predetermined position, so the mandrel bar is held by friction with the raw tube and can freely move in the axial direction, which is called FFM.

In response to this, recently SFM and RRM have been developed which have a bar insertion machine equipped with a mandrel bar restraint mechanism, but the present invention is to obtain a product with extremely low thickness deviation in accordance with the purpose of such a mill. The object of the present invention is to provide a control device for a mandre mill insertion machine that can perform the following operations.

A detailed explanation will be given below with reference to the drawings shown in FIGS. 1 and 2. Fig. 1 is a schematic configuration diagram showing the relationship between a mandrel mill and a bar insertion machine. In the figure, 1 is a group of stands of the mandrel mill, for example, eight sets of stands are provided, but in this embodiment, there are four sets of stands. It shows. 2a, 2b, 2c, 2
d is a load detector provided on each stand. 3 is a material to be rolled, and a mandrel bar 4 restrained by a bar restraint mechanism 5 attached to an insertion machine 6 is inserted into the hollow part of the material. This restraint mechanism 5 can be opened and closed by, for example, a solenoid valve, and the mandrel bar 4 can be opened by a control signal to the solenoid valve. The insertion machine 6 is driven by a DC machine 8 via a reduction gear 7, and its rotational speed is detected by a speed detector 9.

FIG. 2 is a block diagram showing the configuration of the present invention. A DC machine 8 that drives the insertion machine 6 is operated by a thyristor Leonard device 11 with an AC power supply 10 as input. 12 is the master control device and speed setting device 13
Alternatively, the speed setting value or tension setting value set by the tension setting device 14 is processed according to the signals of each stand load detector 2a to 2d, and the speed setting value or the tension setting value set by the tension setting device 14 is processed according to the signal from each stand load detector 2a to 2d, and the speed setting value or the tension setting value set by the tension setting device 14 is processed according to the signal of the speed control or current control selection signal 12a to be sent to the thyristor Leonard device 11. to provide a speed reference signal 13a or a current reference signal 14a. That is, the main control device 1
2, first, the selection signal 12a is used as speed control until the tip of the material to be rolled 3 has bitten into all stands from the first stand to the fourth stand, and the signal is controlled according to the setting value of the speed setting device 13. The speed standard 13a
The signal is output to the thyristor Leonard device 11 as a signal. Then, the thyristor Leonard device 11 compares the signal 13a with the speed feedback signal detected by the speed detector 9, and performs speed control so that the set speed is achieved. Further, the fact that the rolled material 3 is caught in all the stands can be obtained from the logical product of the detection signals of the load detectors 2a to 2d. Therefore, when it is detected from the logical product value of these detection signals that all the stands 1 are in a state where the material to be rolled 3 is rolled, the selection signal 1 is generated.
2a switches to current control, and outputs a signal corresponding to the setting value of the tension setting device 14 to the thyristor Leonard device 11 as a current reference signal 14a. The thyristor Leonard device 11 compares a current value obtained from an internal current detection circuit with a current reference signal 14a, and performs current control. Then, as the rolling of the material to be rolled 3 progresses and the rear end of the material to be rolled 3 passes through the first stand, the selection signal 12a is again set to speed control, and the rear end passes through the stand in the same manner as when the leading end passes through the stand. Speed control is also performed inside. Here, the fact that the rear end of the rolled material 3 has passed through the first stand can be obtained from a change in the detection signal of the first stand load detector 2a.
In the case of SFM, the restraint mechanism is opened and the mandrel bar 4 is released by a signal when the rear end passes through the intermediate stand, for example, a third stand exit signal (2c off).

Also, depending on the type of mill, the speed reference signal 13a may be in the same direction or in the opposite direction to the advancing direction of the rolled material 3. Therefore, the mandrel bar can be differentiated by positive and negative polarity signals depending on the direction. Control is also possible by moving 4 forward or backward.

In this way, the present invention controls the mandrel bar insertion speed to a constant speed when the material to be rolled is bitten by the stands and slips out, and also maintains a constant tension during rolling when the material to be rolled is bitten by all the stands. It is designed to be controlled.

Here, tension control and the relationship between driving the mandrel bar and tension will be explained.

In this device, tension control is performed by current control of the DC motor 8 for driving the mandrel bar insertion machine. In other words, this device corresponds to the payoff reel of a cold rolling mill, and during rolling of the raw pipe (pipe), it is pulled in the direction of pipe movement by the frictional force between the pipe and the mandrel bar, and the tension is released from the mandrel bar insertion machine. If you look at it, it becomes a (-) load (it generates torque in the opposite direction to the direction of rotation). Therefore, in practice, the tension is controlled by providing a current reference corresponding to the tension and controlling the current by feeding back the current of the DC motor 8.

Such control is well known in the reel control described above.

In addition, the relationship between the pipe feed speed and the work content, the tension acting on the mandrel bar insertion machine, and the DC motor 8
The correspondence with current control is shown in Fig. 3.

Further, #1 to #n are stand numbers, ON indicates that the pipe is caught in the stand, and OFF indicates that the pipe has come off the stand. After the pipe is caught in the final stand, tension control is performed to maintain a constant tension until the pipe is removed from the first stand.

In addition, in the present invention, the relationship between the speed of the mandrel bar and the movement of the rolling neutral point when the pipe, which is the material to be rolled, is biting or falling off, and the speed of the mandrel bar is controlled to be constant during biting or falling off. .
The significance of this will be explained below.

When rolling a pipe, a mandrel bar is passed through the hollow pipe, and the bar is used as a medium roll for rolling with a circular caliber. There are multiple rolling stands (usually 7 to 8 stands), and the peripheral speed increases as you go to the later stages, so the forward tension increases as the rolling stands progress, and the neutral point within the stand during rolling increases. Moving. Conventional mills use a full-float system and do not have a restraining mechanism for the mandrel bar, and as the number of rolling stands changes, the wall thickness at the front and rear ends of the pipe increases. With the new mill, the mandrel bar is engaged and restrained by the bar insertion machine during uncoupling and rolling, and can be controlled at a constant speed, so there is no tension fluctuation compared to the full float method, and the front and rear ends of the pipe are almost uniform with the center. Can be made thicker. This mill is called the bar retained method. In this case, the speed of the mandrel bar is maintained at approximately the speed of the material on the inlet side of the #2 stand during rolling. However, even in this case, tension fluctuations occur during rolling due to uneven lubrication of the contact surfaces between the bar and the pipe. This idea is
When rolling with all stands, the bar insertion machine is controlled with a constant current so that the tension remains constant even if the friction coefficient between the bar and the pipe to be rolled changes.
This ensures more reliable control of tension fluctuations, which is the original purpose. It is desirable to control the tension by sequentially changing the tension standard according to the change in the number of rolling stands, even when the #1 stand to the final stand is being rolled while being sequentially engaged and released. Even if this were done, it would not be possible to control the tension balance (balance of front tension and rear tension) to be the same as the rolling state of the central part, so speed control is used.

As detailed above, in this invention, the mandrel bar insertion speed is controlled to a constant speed when the material to be rolled is bitten by the stand and when the bottom falls out, and controlled to be at a constant tension when the material is bitten by all the stands and is being rolled. That's what I do. Therefore, the conventional drawbacks of full-flow mandrel mills are biting, movement of the rolling neutral point due to fluctuations in bar speed during bottom slip-out, and problems between the bar and the material to be rolled during rolling on all stands. It is possible to provide a control device for a mandrel bar insertion machine that can prevent uneven thickness due to changes in the coefficient of friction and produce high-quality products that take advantage of the characteristics of a new mill.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of a semi-float mandrel mill, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a diagram for explaining the operation of the present device. 1... Mandrel mill stand group, 2a to 2d
... Load detector, 3 ... Rolled material, 4 ... Mandrel bar, 5 ... Bar restraint mechanism, 6 ... Bar insertion machine, 7 ... Speed reducer, 8 ... DC motor, 9 ... Speed detection device, 10... AC power supply, 11... Thyristor Leonard device, 12... Main control device, 13
...Speed setting device, 14...Tension setting device.

Claims (1)

[Scope of utility model registration request] 90 sets of facing grooved rolls in sequence
In a control device for a mandrel bar insertion machine of a continuous steel pipe rolling mill, which rolls a raw pipe with a mandrel bar inserted in a hollow portion at a position shifted by 100 degrees, the mandrel bar is driven. Compare the motor inserted into the hollow part of the blank tube, the speed detector that detects the speed of this motor, the current detection circuit that detects the current value of the motor, and the speed detection output and the given speed setting value. and current control that compares the detected current value with a reference value corresponding to the given set tension and controls the output so that the current value corresponds to the reference value. a thyristor Leonard device for controlling the electric motor which has a function and selects one of these control functions in response to a selection signal; a detector provided in each stand to detect the rolling load; and a detector for detecting the rolling load. The detection signal from the detector is given to detect the passage timing of the raw pipe, and when any of the stands of the raw pipe is caught or tailed out, the selection signal and speed set by the speed setting device select speed control. The set value was given to the thyristor Leonard device to control the speed at a constant speed, and the selection signal for selecting tension control during rolling in all stands and the set value of the tension setting device were obtained by converting it into a current value corresponding to the set value. A control device for a mandrel bar insertion machine, comprising a main control device that applies a reference value to the thyristor Leonard device to control the tension to a constant tension through current control.