JPH0373363B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a piercing rolling mill equipped with a pair of grooved rolls and a plug in the center of the groove, by means of a pushing device disposed at the entrance side of the rolling mill. The present invention relates to an indentation control method in a press roll perforation rolling method for seamless steel pipes in which rolling is performed while applying an indentation force to the material in the axial direction.

(Prior art) The press roll rolling method is, for example,
23675, etc., and as shown in Fig. 1, a square billet is rotated by a pinion mechanism 1 and a motor 11 via a pusher rod 2, and a roll is rotationally driven by a motor 10 different from the previously mentioned one. The material 3, that is, the square billet 3-1 and the round blank tube 3-2 formed from the square billet are placed in front of and behind the rolls 4 and 4' along the mill center line X-X. An entrance guide 5 and an exit guide 6 are arranged in order to maintain the temperature.

Further, the rolls 4, 4' have a circular caliber,
A plug 7 is supported by a mandrel 8 at the center of the caliber formed by these two rolls 4, 4'. Therefore, the square billet 3-1 during rolling
is advanced by the pushing force given by the motor and the forward force given by the rolls 4, 4',
The inner surface is perforated and expanded by the plug 7, and the outer surface continues to be formed into a circular shape by the roll caliber, and the processing is almost completed at the roll axis Y-Y. that time,
The round tube 3-2 and the mandrel 8 are the guide rolls 9
guided by. In addition, the pushing device and the roll motors 11 and 10 are controlled by thyristor Leonard devices 12 and 13, respectively, to each command value.
V _P (pushing speed) and V _R (roll caliber bottom peripheral speed)
It is operated under constant rotation control.

Conventional pushing speed and roll caliber bottom peripheral speed
The control method for V _P and V _R is, for example, as in Japanese Patent Publication No. 56-3124, where the material transitions from the biting state to the rolling state while keeping V _P /V _R constant. In this case, vibration may occur when the material is biting, which may cause the material to jam or cause abnormal vibrations to the machine.

In general, in a rolling mechanism that has a small biting angle and can bite independently without the need for back-up such as a pushing device, the momentary material speed from the start of biting to the completion of biting is determined by the area where the material is in contact with the roll. determined by the mechanical balance between the roll and the material. For this reason, the inlet speed of the material immediately after biting (the speed of the part of the material that has not been rolled down) increases temporarily, decreases as biting progresses, and when biting is completed, the steady rolling state is reached. Match the entrance speed.
In the rolling method where grooved rolls are used and the starting point of contact of the material with the roll is far from the bottom of the roll groove,
This tendency is greater than in plate rolling where the roll speed is uniform. In this piercing rolling method, unless the roll surface is treated with large knurling, individual biting is difficult and requires backup of the pushing device, etc. However, the speed of the pushing device is V _P
A control method that does not distinguish between the groove bottom speed V _R and the roll groove bottom speed V R during biting and steady state, and keeps V _P /V _R constant, often generates vibrations during biting.

In other words, at the initial stage of biting when the plug can perforate with the pulling force from the rolls, the entrance speed of the material is temporarily higher than the speed at the completion of biting, similar to the above-mentioned rolling mechanism that allows single biting. If the piercing resistance of the plug increases, it becomes impossible to punch the hole with a roll alone, and a backup device such as a pushing device is required. However, because the material speed has temporarily increased, the pushing device is no longer able to apply an effective pushing force to the material, and at this point slips occur between the roll and the material. In this state, as the material is advanced by the pushing device and the drilling progresses, the elongation of the material increases, and the relationship between the material speed and the roll groove bottom speed continues until a state where no slip occurs is reached, resulting in vibration phenomena. Become.
Also, since the material is compressed and deformed by the pushing device,
The fact that the speed of the pushing device cannot directly match the entrance speed of the material is one of the factors that easily generates and sustains vibrations.

(Object of the Invention) In view of the above circumstances, the present invention aims to prevent the above-mentioned vibration by adjusting the pushing speed according to the position of the material with respect to the roll, and to provide a smooth and stable piercing rolling method. In a piercing rolling mill, the position of the tip of the material is constantly monitored and the pushing speed of the material is controlled according to the position of the tip of the material, thereby making the material pushing speed match the material speed. This is a control method for efficient and smooth rolling with less vibration during rolling.

(Structure and operation of the invention) The present invention will be specifically described below based on embodiments shown in the drawings.

First, the basic idea of the present invention will be explained based on FIG.

In the piercing mill, the mass flow of the material 3 is determined by the mandrel 8 and the slotted rolls 4, 4'. From the biting start position of the tip of the material 3 (i.e., the point where the tip of the material first hits the bullet-shaped plug 7 at the tip of the mandrel) to the biting speed (i.e., the tip of the material passes the plug 7 position and reaches the flat part) In the process of reaching the latter speed), the speed of the material in the portion that is in contact with the roll is constantly changing and is not constant, depending on the shape of the tip plug of the mandrel mentioned above.

In other words, the material tip speed V″ at the start of biting is
Since the plug 7 of the mandrel is not yet present at the center of the material 3, the material tip speed V is slower than the biting speed when the mandrel (plug) is at the center of the material. (Depending on the mass flow side) On the other hand, if the material tip speed at this time is not made to match the circumferential speed of the grooved roll, it will generate vibrations, causing the material to jam or abnormal vibrations, causing damage to the machine.
Interfering with operations.

In response to such a situation, the speed of the roll is generally changed (in this case, the speed is increased). but,
Since the roll has a large inertia, it requires a large amount of acceleration power, and the output of the drive motor becomes excessive, making it impractical.

In view of this, the present invention solves the above problem by keeping the roll speed V _R constant without changing it, and changing the pushing speed V _P of the pushing device (in this case, decelerating it). That is, biting start speed>biting speed.

Furthermore, an entry guide is provided on the entry side of the rolling mill. The time it takes for the material tip to pass through this entrance guide and contact the plug at the mandrel tip is:
This is a waste of time in the rolling operation, so it must be kept as short as possible. This material feeding speed is called the idle feeding speed.

If the idle feed speed and the biting start speed are made the same and the biting start speed is increased, the impact during biting becomes excessive and problems such as biting stoppage due to material buckling occur. Therefore, the relationship between the respective speeds in the pushing process is as follows: idle feed speed > biting start speed > biting speed.

In this way, by changing the pushing speed of the pushing device (sequentially decelerating) so that the material speed and roll speed at the part where the material and roll are in contact are constant, stable piercing rolling can be performed with high efficiency. can.

Note that the timing of each speed change is usually detected using a load cell embedded in the rear end of the mandrel. However, since the plug at the tip of the mandrel is shaped like a bullet to improve the biting performance, it is difficult to distinguish the timing of switching to the biting speed.
Therefore, the present invention employs a method described later, in which a value calculated from the geometrical positional relationship is confirmed and grasped using a position detector (pulse generator) provided in the pushing device.

FIG. 2 is a diagram showing the positional relationship between the pushing device, the rolls, and the material. In the figure (roll center Y-
each position from Y), Lpo: special position of the pushing device,
Lo: Distance limited by roll entrance guide device, etc., lx: Material length, Lg: Margin.

Figure 3 shows the rotation speed increase curve of the motor for driving the pushing device, where Vx _B is the upper limit speed of the voltage control range of the motor, Vx ₁ is the maximum speed of the motor, and the speed reached from speed 0 to Vx _B Time τ _B , from 0
Let τ _T be the time taken to reach Vx ₁ . From 0 in the diagram
The difference between the acceleration up to Vx _B and the acceleration from Vx _B to Vx ₁ is due to voltage control up to Vx _B and field control above Vx _B.

Since Lo in Figure 2 is large in a piercing rolling mill, the material should be conveyed between Lo in the shortest possible time in order to prevent instability of biting due to a drop in the starting temperature of piercing due to a delay in conveyance time, and from the standpoint of production efficiency. The material free feed speed Vx ₁ should be the maximum rotation speed of the motor,
In addition, it is necessary to make the acceleration/deceleration to Vx ₁ as fast as the motor allows.

FIG. 4 is a diagram showing a speed pattern of the pushing method of the present invention. In the figure, Vx ₁ is the empty feed speed to convey the material a distance of Lo as quickly as possible,
Vx ₂ is a pushing speed synchronized with the material speed at the start of biting, and Vx ₃ is a pushing speed synchronized with the material speed at the end of biting. The deceleration distance from Vx ₁ to Vx ₂ is determined by the following formula as the shaded area S ₁₂ in the figure.

(1) When Vx ₂ ≦Vx _B S ₁₂ = 1/2 (Vx ₁ + Vx _B ) (τ _T − τ _B ) + 1/2 (Vx _B + Vx ₂ )・Vx _B −VX ₂ /Vx _B・τ _B (2) When Vx ₂ > Vx _B , S ₁₂ = 1/2 (Vx ₁ + Vx ₂ ) ・Vx ₁ −Vx ₂ /Vx ₁ −Vx _B・(τ _T −τ _B ) The traveling distance at Vx ₂ is Vx If the traveling time at ₂ is Tsec, then S ₂ =Vx ₂ ·T.

Therefore, these biting start speed V _X2 and biting speed
V _X3 is actually determined, for example, by the following method.

First, the biting start speed _V Consider the following inclination.

When applying plugs with sharp shapes, use V _X2 faster.

When the plug tip position is on the pushing device side,
V _X2 is faster.

When the material temperature is high, V _X2 should be set faster.

When the material is soft, V _X2 should be faster.

~When the conditions are reversed, V _X2 should be slower.

The specific speed value is determined by adding past experience.

Next, the biting speed V _X3 is determined by a computer based on the biting start speed V _X2 according to the mass flow law.

For example, when the cross-sectional area of the material is A, the plug diameter is d, and the hole bottom diameter is D, from the mass flow law, _V
×K ₁ =V _X3 ×π(D ² −d ² ) ×K ₂ . _{Therefore , V} ^{_ _} _{_ _ K 1} ≦1.0) K ₂ : Shape factor (Since the material is slightly irregular from a perfect circle and has some corners, this coefficient is used to correct it. _{K 2} ≧1.0) , biting start speed V _X2 , and biting speed V _X3 are calculated.

Fig _. 1 shows an example of a combination of the control system of the present invention and a piercing rolling mill. Distance lp, push speed Vx ₂ synchronized with roll speed at the start of biting, set by each setter 21, 16, 22, 1
8, then from Vx ₁ , Vx _B , τ _T , τ _B and Lg, Lo, which are input as fixed values in advance,
Compare the size of Vx ₂ and Vx _B , calculate S ₁₂ , and calculate Vx ₂
Calculate S ₂ from and T. The pushing device 1 is driven by a motor 11 driven by a thyristor Leonard device 12 for driving the pushing device in accordance with a speed command Vp given by a general control device 15. Furthermore, with the mill core as the origin, the distance from the mill core to the tip of the pushing device 2.
Lp (Lp = Lpo - Lg at the standby position, Lp = lx + lp at the position where the tip of material 3 touches the tip of plug 7)
A signal from a pulse transmitter 14 directly connected to the pushing device drive motor 11 is input to the general control device 15 and constantly monitored. Material 3 is operated with a force that does not change in the cross-sectional direction, so Lp
This is equivalent to monitoring the position of the tip of the material 3 by monitoring. First of all, the pushing device 1 is operated from the standby position Lpo by the general control device 15.
It is operated with a command of Vp≡Vx ₁ . The change in acceleration at Vx _B during the process is controlled and operated by a thyristor Leonard device 12. Also,
The speed change point (FIG. 4) is determined as follows.
The first deceleration starting point is the point where the material tip reaches the sum of the distance lp from the mill core to the plug tip, the distance _S12 required for deceleration, and the distance _S2 taking into account the delay of the control system. In reality, it is managed by the Lp that monitors the location. That is, the point is Lp=lx+lp+S ₁₂ +S ₂ . At this point, the general control device 15 is Vp≡
Give Vx ₂ command and start decelerating from Vx ₁ to Vx ₂ . Next, the second deceleration start point is the point where the tip of the material reaches the distance lp from the mill core to the plug tip, that is, by giving the command Vp≡Vx ₃ at the Lp = lx + lp point, Vx ₂ The material starts to bite at the timing when the speed decreases to Vx ₃ at a deceleration α. The deceleration α ₁ is set based on empirical values obtained based on the material of the material to be drilled, its temperature, and the shapes of the roll and plug, so the vibration at the start of biting ensures that the material and roll follow each other. decrease due to _Vx2
The running time T is set for the purpose of absorbing the delay in the control system when decelerating from Vx ₁ to Vx ₂ . _Vx2 ,
Vx ₃ also depends on the material being drilled, temperature and roll speed.
Determined by V _R1 . Good results can be obtained by setting the relationship between Vx ₂ , Vx ₃ and V _R1 as Vx ₂ > V _R1 > Vx ₃ .

Furthermore, the relationship of Vx ₂ > V _R1 > Vx ₃ causes a problem, so in other cases, for example, when Vx ₃ is fixed and V _R1 is varied, the motor power will decrease, so it is necessary to have a power margin. Furthermore, production efficiency is improved because the production speed is always maintained at a high rate.

(Effects of the invention) As detailed above, by using the signal from the pulse oscillator directly connected to the driving motor of the pushing device, the exact position of the tip of the material is grasped and the material deformation situation is predicted as a result. By changing the speed of the device, there was no slippage between the roll surface and the material, and vibrations during biting were prevented.

In addition, since the pushing speed is reduced from the maximum speed (Vx ₁ > Vx ₂ > Vx ₃ ), the motor power is lower than the rolling method in which the roll speed is lower than usual at the time of biting and then raised at the same time as biting starts. Processing was possible with relatively little power. Furthermore, since the speed of the pushing device is controlled to gradually decrease, it has been confirmed that productivity also increases by 2%.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a combination of the control device of the present invention and a piercing rolling mill, Fig. 2 is a diagram showing the positional relationship between the material and the pushing device in the piercing rolling mill, and Fig. 3 is a diagram of the motor for driving the pushing device. The rotation speed increase curve is shown. FIG. 4 shows the speed pattern of the pushing device. FIG. 5 is an explanatory diagram for explaining the principle of the present invention. In the figure, 1... Pinion mechanism, 2... Pusher rod, 3... Rolled material, 3-1... Entry side material, 3-2... Perforated material, 4... Caliber roll, 5... Input side material. Side guide, 6... Exit guide, 7... Plug, 8... Mandrel, 9... Guide roll, 10... Roll drive motor, 1
DESCRIPTION OF SYMBOLS 1... Motor for driving the pushing device, 12... Thyristor Leonard device for driving the pushing device, 13... Thyristor Leonard device for driving the roll, 14...
Pulse oscillator, 15... General control device, 16...
Vx ₂ time setter, 17...V _R1 setter, 8...
Vx ₂ setting device, 19...Vx ₃ setting device, 20...α ₁ setting device, 21...Material length (lx) setting device, 22...lp
Setting device.

Claims (1)

[Claims] 1. In a piercing rolling mill comprising a pair of grooved rolls and a plug at the center of the groove, a position detector is provided in a pushing device disposed on the entry side of the rolling machine to detect the tip position of the material. is monitored, and when the leading edge of the material reaches a pre-calculated speed change point, the speed of the pushing device is adjusted to the material conveyance speed (empty feed speed), biting start speed, and biting speed to match the advancing speed of the material. , a method for controlling indentation of a piercing rolling mill, characterized by sequentially reducing the speed. However, empty feed speed > biting start speed > biting speed.