JPS62244511A - Tension controlling method for mandrel mill - Google Patents

Abstract

PURPOSE:To uniformize wall thickness of pipe by calculating the coefft. of friction between a mandrel bar and pipe stock and calculating a torque arm coefft. common to respective stands, then adjusting the roll gap and rotating speed in accordance with the calculated value. CONSTITUTION:One piece each of roll gap adjuster 1 and rotating speed adjuster 2 are respectively provided to plural pieces of stands A1-An, and a load cell 3 for measuring rolling load is disposed. The force acting in the thrust direction of a mandrel bar 4 and rolling load are detected or calculated and the coefft. of friction between the bar 4 and the pipe stock 8 is calculated. The torque arm coefft. common to the respective stands is determined from the calculated coefft. of friction and the rolling torque of a motor 7. The roll gap and rotating speed are then adjusted in accordance with the tension of the pipe stock 8 determined from the calculated values, etc. Since the tension of the pipe stock 8 is maintained optimum, the product pipe has the uniform wall thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a tension control method when a blank pipe is completely rolled by a mandrel mill. .

[Conventional technology]

When rolling a blank pipe with a mandrel mill, the magnitude of the tension or compressive force acting in the axial direction of the blank pipe between each stand in the mandrel mill is calculated, and based on the calculation result, the tension ``!, fc is It is necessary to adjust the spacing and rotation speed of each roll of the mandrel mill so that the compression force is at an appropriate value. If this is not done, the wall thickness of the rolled raw pipe in the axial direction will not be uniform. It disappears.

For example, in a tandem mill for manufacturing all bars i#, the tension acting in the axial direction of the steel bar being rolled is caused by the rolling load acting on each roll of the tandem mill, the torque of the motor for driving each roll, etc. Alternatively, the magnitude of the compression force is calculated, and based on the calculation result, the interval and rotation speed of each roll are adjusted so that the tension or compression force becomes an appropriate value.

However, when rolling raw pipes using a mandrel mill, it is difficult to quantify the magnitude of the force acting on the mandrel bar used for rolling, so each The spacing and rotation speed of the rolls were adjusted. For this reason, it is difficult to make the wall thickness of the raw tube uniform in the axial direction after rolling, and it has been desired to detect the tension during rolling.

Conventionally, as a method to meet such demands, Japanese Patent Application Laid-Open No. 1986-
Japanese Patent Application No. 221107 discloses a method for detecting and controlling tension during rolling of a tube material. This tension detection/control method consists of: ■Detecting the rolling load of each stand; ■Converting the roll rolling torque to the current of the roll drive motor.

Calculate the voltage from the number of rotations per rotation, ■ Calculate the torque arm during tube passing from the above rolling load, roll rolling torque, etc., ■ Calculate and correct the initial friction coefficient between the tube material and mandrel bar tonneau between each stand, and calculate the torque arm during rolling. The friction coefficient is fully calculated, ■ The pipe material tension between each stand is estimated from the rolling load detected above, the calculated roll rolling torque, etc., and ■ The tension of the rolls is adjusted so that the estimated tension value is maintained at zero or a small positive value. The forward rate or backward rate is corrected.

[Problem that the invention seeks to solve]

The conventional tension detection/control method described above calculates the friction coefficient when calculating the tension, but it calculates only the torque arm during pipe passage, resulting in large errors, and the torque arm is the torque arm of the upstream stand. Errors accumulate because the values are sequentially used.

For this reason, there is a problem in that the tension of the tube material during pipe passage calculated using this torque arm also has an error, making it difficult to control it properly and making it difficult to set the tension to an appropriate value.

This invention was made to solve this problem, and it is possible to easily and accurately detect the tension or compression force acting on the raw pipe between each stand when rolling the raw pipe with a mandrel mill. The purpose of this study is to propose a complete tension control method for a mandrel mill that can maintain the tension or compression force at an appropriate value.

[Means for solving problems]

The tension control method for a mandrel mill according to the present invention is as follows: (1) Detecting or calculating the force and rolling load acting in the thrust direction of the mandrel bar during rolling on all stands and at each passing/cutting of each stand; Mandrel bar on each stand due to force and rolling load distribution
Calculate the coefficient of friction between the pipe and the raw pipe, and use the fact that the tension or compression force acting on the pipe between each stand is zero due to the friction coefficient above, the rolling load of each stand, and the rolling torque of the roll drive motor. Calculate the torque arm coefficient common to each stand, ■ Calculate the tension acting on the raw pipe during rolling from the above torque arm coefficient, friction coefficient of each stand, rolling load, and rolling torque of the roll drive motor, ■ Calculate the above j - The tension of the mandrel mill is fully controlled by changing the roll spacing and roll rotation speed so that the tension becomes the appropriate tension value between each stand.

[For production]

In this invention, since the friction coefficient between the mandrel bar and the blank pipe is determined by the force acting in the thrust direction of the mandrel bar and the distribution of the rolling load, an accurate friction coefficient can be obtained, and this friction coefficient and torque arm coefficient The tension detection accuracy is improved by calculating the tension using .

Furthermore, since the speed of the mandrel bar is controlled based on the detected tension, the tension between each stand can always be kept at an appropriate value.

〔Example〕

FIG. 1 is a block diagram showing an example of the invention.

As shown in FIG.
C) One and several roll speed regulators (ASfL)
2 is a plurality of stands A1 to An of the mandrel mill (
One stand is installed in each of the following stands: A: first stand, An: final stand). A plurality of load cells 6 for measuring rolling carts are installed one each in a plurality of stands A1 to An. The rear end of the mandrel bar 4 is fixed to a cart (not shown) that moves at a constant speed in the same direction as the moving direction of the raw pipe 8.

The mandrel per speed regulator adjusts the rotation speed of the cart drive motor 6 based on the calculation result from the calculation control device 9. The voltage, current, and roll rotation speed of the roll drive motor 7 of each of the plurality of stands A1 to An are measured by a measuring device (not shown) and sent to the arithmetic and control unit 9 at the same timing. It will be done. The arithmetic and control unit 9 issues an adjustment command to each roll interval adjuster 1 and each roll rotation speed adjuster 2 before rolling one raw pipe so that the wall thickness of the raw pipe after rolling becomes a predetermined thickness, Then, as will be described later, the moving speed of the mandrel bar 4 at which the axial wall thickness of the raw pipe after rolling becomes uniform is calculated, and the calculated result is sent to the total mandrel bar speed regulator 5.

Next, a method of calculating and detecting the magnitude of the tension or compression force of the raw pipe between the stands during rolling will be explained using the above embodiment.

The tension or compression force applied to the raw tubes on the inlet and outlet sides of the stand is calculated based on the following equation (1), which is a calculation equation for the rolling torque G of the roll shaft per roll of each stand.

However, a: Torque arm coefficient R, roll radius of the bottom of the two-roll caliber (average value of the roll radius of the part in contact with the raw tube), H: Wall thickness of the raw tube on the stand entrance side, h: Stand exit side The wall thickness of the raw pipe, μ: G friction t of the mandrel bar, qb: Tension or compression force applied to the raw pipe on the stand entry side, qf: Tension or compression force applied to the raw pipe on the stand exit side, P: Rolling Load, i: Subscript indicating stand number.

Explanations of each of the above symbols are shown in FIG.

The left side of the above equation (1) is the rolling torque of the roll drive motor 7, and is calculated according to the following equation.

However, η: Torque transmission efficiency C: Conversion factor ■：Motor voltage ■: Motor current ra: armature resistance N: Roll rotation number.

The above-mentioned torque transmission efficiency η, conversion coefficient C1, armature resistance ra can be determined in advance, and motor voltage v1 motor current 11 roll rotation speed N can be measured during rolling, so the rolling torque G is , can be calculated during rolling.

The first term on the right side of the above equation (1) represents the first moment of the rolling load, the second term on the right side represents the tension or compression force acting in the axial direction of the raw pipe on the entrance and exit sides of the stand, and , the sixth term on the right side represents the J station friction force between the mandrel bar 4 and the blank pipe 8.

On the right side of equation (1), the roll radii R and U at the bottom of the roll caliber can be determined in advance, and the rolling load P can be measured by the load cell 6. Also, the wall thickness Hj of the stock pipe on the stand entry side and the wall thickness of the stock pipe on the stand exit side are 6th.
As shown in the figure, it is determined by the roll caliber shape of the roll 10, the geometric shapes of the mandrel bar 4, the roll gear C, etc.

Therefore, by determining the friction coefficient μi between the mandrel bar 4 and the raw pipe 8 and the torque arm coefficient ai of each stand, the tension or compression force of the raw pipe between each stand can be obtained.

Hereinafter, a method for determining the friction coefficient μi and the torque arm coefficient ai will be explained using the case where the stand has eight stages as an example.

First, the friction coefficient μi is determined.

The force F acting in the thrust direction of the mandrel bar 4 and the rolling load ff1Pi of each stand are measured in time series over a period of time n, and the time series data F1. ...+B'+...Fn
and Pi(1),...' Pi(k), "'
``1(n) 'l: Obtain: Using this time series data, the variance S+ of the rolling load P1 of each stand, the covariance Sij of the rolling loads Pi and Pj of the i-th stand and the first stand Sij
(j, 'go) and the covariance of the force F acting on the mandrel bar 4 and the rolling load Pi of each stand 5ij (j=0)
From each variance of the above time-series data, the friction coefficient μm of the mandrel bar of the first stand is determined by the following equation.

μ,...(6) μ2. μ3...μ8 can be found in the same way.

If time series data is processed as is using equations (3), (4), and (5) above, the average value of the interval from =1 to k = n will be calculated at time.◇However, in online processing,
It is reasonable to emphasize newer data than past data. Therefore, time series data is weighted using the following method 1.

Now time series data k XI + X2 + ”' X
B(+"' xn = 1]-1 = IXk-X, + 7.A1

In addition, ■ of 17n in the above equations (3), (4), f5) can be expressed by the following equation from the force equation.

By calculating n, it is possible to perform online data processing that takes weighting into consideration.

The entire friction coefficient can be calculated by the above calculation in any of the following states: when the tip of the blank pipe is being passed through, when all the stands are being engaged, and when the rear end is being removed. As a result, it is possible to accurately grasp the friction coefficient μm of each stand in each state.

Next, find the torque arm coefficient ai.

The front tension Qf, i of the i-th stand and the rear tension qb, i+1 of the i+1-th stand are equal, and the rear tension qb, I of the first stand and the front tension qf, 9 of the 8th stand are zero, so the mountain (qf, iQl,, 1) "" O... (9) Therefore, if we take the sum of i = 1 to 8 for equation (1), here the torque arm coefficient ai at each stand has small fluctuations, so if it is a constant value a, then the following equation is obtained. is required.

In equation (11), Qi is from equation (2), μiPi is (
Since 1-Ii, hi and 几i can be calculated based on the geometric shape of the roll, etc., the torque arm coefficient af can be calculated using Equation 09.

The difference between the front tension qf,i and the rear tension qb,i of the i-th stand can be found from equation (1) using the friction coefficient μI, the lux arm coefficient a, etc. calculated above using the following equation.

Also, forward tension qf, i is qb, 1 = 0IQf,
Since i""qb and i+1, it can be determined by the following equation.

Next, a method of adjusting the roll interval and the roll rotation speed so that the tension or compression force acting on the raw pipe between each stand, estimated and calculated as described above, becomes an appropriate value will be described.

As shown in Figure 6, the wall thickness of the raw tube at the bottom of the roll caliber is
k hcs Mandrel bar diameter 'il) B, roll caliber depth D1 rolling load fi: Ps When the mill rigidity is K, the roll interval Ci of the first stand can be determined by the following equation.

Ci = 2hc, i -1-1), 3-21)i
-Pi/Ki +・+・・・・＋＋＋・+a4) In formula 04, hc, i, l)B and DI are determined by the geometric shape of the rolls, etc., and the rolling load Pi is determined by the load cell 6.
or estimated using the following formula.

However, fl: function A: Cross-sectional area of the raw pipe r: Deformation resistance of raw pipe ■B: 8-motion M degree of mandrel bar.

Further, the roll rotation speed Ni of the first stand is determined by the following equation, assuming that the moving speed of the raw pipe is 'Fr-vH.

Ni = v 4 / 2rR'i (1+φρ...
Turn/Pause/Song/αe Here, the moving speed V+ of the element- is as follows, assuming that the cross-sectional area of the raw pipe of the final stand is i7 An and the moving speed of the raw pipe of the final stand is vn.

vi・vnAn/Ai...αη (In equation 10, R'i is the equivalent roll radius, the roll radius f Rc at the bottom of the roll caliber, and θ is the circumferential contact angle between the roll and the raw pipe. passed away, φ
i is the advanced rate and is obtained from the following formula: 0 φ1-= f2(hc,, l-1, hc,, l +
A1-7+ AI * Q(,,i-1+ qf,i
+ ri + DB + VB) ``'α shown in the above formula I and (10).Roll interval Ci and roll rotation speed N
The arithmetic and control unit 9 calculates l.

Now, assuming that there is an error i Δqfi between the detected value q of the tension or compression force detected during the rolling and its target value q'f, i, the tension or compression force input to the arithmetic and control unit 9 is The data is the detected value qfi with the error ΔQf
Correct and input each stand with i. Thereby, the tension or compression force of the raw pipe between each stand can be controlled to an appropriate value.

〔Effect of the invention〕

As explained above, this invention detects the tension or compression force of the raw pipe between each stand with high precision, and controls the roll interval and roll rotation speed online so that the detected tension or compression force becomes an appropriate value. This has the effect of making the wall thickness uniform over the entire length of the rolled raw pipe.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the rolling state of a blank pipe, and FIG. 6 is a longitudinal sectional view showing the rolling state of plan α. A1~An...Stand, 1...Roll spacing adjuster, 2...Roll rotation speed adjuster, 6...Load cell,
4... Mandrel bar 15... Mandrel bar speed regulator, 8... Base tube, 9... Arithmetic control device. Agent Patent Attorney Masaru Sato Figure 1〒-〇shi Tomariishi T-Tai 7〈), to

Claims (1)

[Claims] (1) Detect or calculate the force and rolling load acting in the thrust direction of the mandrel bar during rolling on all stands and each stand passing/cutting, and distribute the force acting in the thrust direction and rolling load to the mandrel bar in each stand. The friction coefficient between the bar and the blank pipe is calculated, and the torque arm coefficient common to each stand is calculated using the friction coefficient, the rolling load of each stand, and the rolling torque of the roll drive motor, and the torque arm coefficient and the friction of each stand are calculated. Tension of a mandrel mill that calculates the tension acting on the raw pipe during rolling from the coefficient, rolling load, and rolling torque of the roll drive motor, and changes the roll spacing and roll rotation speed so that the calculated value of tension becomes an appropriate value. Control method.