JPH0586291B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a tension detection method and a tension control method when rolling a blank pipe using a mandrel mill. [Prior art] When rolling a raw pipe with a mandrel mill,
The magnitude of the tension or compression force acting in the axial direction of the raw pipe between each stand in the mandrel mill is calculated, and based on the calculation result, the mandrel mill is adjusted so that the tension or compression force becomes an appropriate value. It is necessary to adjust the interval and rotation speed of each roll, and if this is not done, the wall thickness of the rolled raw pipe in the axial direction will not be uniform. For example, in a tandem mill for producing steel bars, tension or compression is applied in the axial direction of the steel bar during rolling due to the rolling load acting on each roll of the tandem mill, the torque of the motor for driving each roll, etc. The magnitude of the 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 with a mandrel mill, it is difficult to quantify the magnitude of the force acting on the mandrel bar used for rolling, so it is difficult to quantify the force acting on the mandrel bar used for rolling. Therefore, the spacing and rotation speed of each roll 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 tension during rolling. In order to meet these demands, Japanese Patent Laid-Open Publication No. 60-221107 discloses a method for detecting tension in rolling pipe material. This tension detection method detects the rolling load of each stand, calculates the roll rolling torque from the current, voltage, and rotation speed of the roll drive motor, and calculates the torque arm during pipe passage from the above rolling load, roll rolling torque, etc. Then, the friction coefficient during rolling is calculated by calculating and correcting the initial friction coefficient between the pipe material and the mandrel bar between each stand, and the pipe material tension between each stand is calculated using the rolling load detected above, the calculated roll rolling torque, etc. This is a method of estimation. [Problems to be solved by the invention] The conventional tension detection method described above has a large error because it calculates the friction coefficient during rolling by calculating only the torque arm during pipe passing. The torque arm is determined by sequentially using the torque arms of the upstream stand, so errors accumulate. Therefore, there is a problem in that an error occurs in the tube material tension during pipe passage calculated using this torque arm. This invention was made to improve 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 object of the present invention is to propose a tension detection method and a tension control method for a mandrel mill that can maintain the detected tension or compression force within an appropriate range. [Means for Solving the Problems] The tension detection method for a mandrel mill according to the present invention detects the force acting in the thrust direction of the mandrel bar and the rolling load during rolling on all stands and at each stand passing/cutting. The friction coefficient between the mandrel bar and the blank pipe in each stand is calculated by the force acting in the thrust direction and the distribution of the rolling load, and the Using the fact that the sum of tension or compression forces acting on the pipes between stands is zero, calculate the torque arm coefficient common to each stand, and calculate the torque arm coefficient, friction coefficient of each stand, rolling load, and roll drive motor. Calculate the tension acting on the raw pipe during rolling using the rolling torque. In addition, the tension control method for a mandrel mill according to the present invention includes detecting or calculating the force and rolling load acting in the thrust direction of the mandrel bar during rolling on all stands and each time the plate is passed through and through each stand, and acting in the thrust direction. The friction coefficient between the mandrel bar and the raw pipe in each stand is calculated by distributing the force and rolling load, and the tension or The torque arm coefficient common to each stand is calculated by using the fact that the sum of the compressive forces is zero, and the element during rolling is calculated using the torque arm coefficient, friction coefficient of each stand, rolling load, and rolling torque of the roll drive motor. The tension acting on the pipe is calculated, and the above calculated value is sent to the mandrel bar speed regulator so that the calculated tension falls within the appropriate tension range between each stand. This changes the moving speed of the mandrel bar and controls the speed of the mandrel mill. Control tension. [Operation] 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 Tension detection accuracy is improved by calculating tension using the torque arm coefficient. Furthermore, since the speed of the mandrel bar is controlled based on the detected tension, the tension between each stand can always be kept within an appropriate range. [Embodiment] FIG. 1 is a block diagram showing an embodiment of the present invention. As shown in FIG. 1, a plurality of roll spacing regulators (APC) 1 and a plurality of roll rotation speed regulators (ASR) 2 are connected to a plurality of stands A1 to An (A1: first stand, An: One of each is installed in each of the final stands. A plurality of load cells 3 for measuring the rolling load are installed in each of the plurality of stands A1 to An. The rear end of the mandrel bar 4 is restrained by a bar restraining rack 10 that moves at a constant speed in the same direction as the moving direction of the blank tube 8. 11 is a pinion, as shown in FIG.
The rear end of the mandrel bar 4 is attached to a rack 10 for bar restraint.
Motor 6 is restrained by the rack and pinion system.
It is controlled at a constant speed by The mandrel bar speed regulator adjusts the rotation speed of the drive motor 6 of the pinion 11 meshed with the bar restraining rack 10 based on the calculation result from the calculation control device 9. The voltage, current, and roll rotation speed of each of the roll drive motors 7 of the plurality of stands A1 to An are measured by a measuring device (not shown), and are sent to the arithmetic and control unit 9 at the same timing. Sent. 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 the 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 this calculation result is sent to the 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 blank tubes on the inlet and outlet sides of the stand is calculated based on the following equation (1), which is the calculation equation for the rolling torque G of the roll shaft per roll of each stand. Gi=ai√2(−)Pi−1/2 Ri(q _fi −q _bi )+μiRiPi ……(1) R: Roll radius at the bottom of the roll caliber (average value of the roll radius of the part not in contact with the raw pipe) ) H: Wall thickness of the raw pipe on the stand entrance side h: Wall thickness of the raw pipe on the stand exit side μ: Friction coefficient of the mandrel bar qb: Tension or compression force applied to the raw pipe on the stand entrance side qf: At the stand exit side Tension or compression force applied to the raw pipe 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. G=ηC(V-Ira)I/N...(2) where η: Torque transmission efficiency C: Conversion coefficient V: Motor voltage I: Motor current ra: Armature resistance N: Roll rotation speed. The torque transmission efficiency η, conversion coefficient C, and armature resistance ra can be determined in advance, and the motor voltage V, motor current I, and roll rotation speed N can be measured during rolling. Torque G
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 second term on the right side represents the frictional force between the mandrel bar 4 and the raw pipe 8. On the right side of equation (1), the roll radius R at the bottom of the roll caliber can be determined in advance, and the rolling load P
can be measured by the load cell 3. In addition, the wall thickness Hi of the raw pipe on the stand entry side and the wall thickness hi of the raw pipe on the stand exit side are as shown in Figure 3.
It is determined by the shape of the roll caliber, the geometric shape of the mandrel bar 4, the roll gap 11, 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 between each stand can be obtained. Below, the friction coefficient μi is taken as an example when the stand has 8 stages.
This section explains how to calculate the torque arm coefficient ai. First, find the friction coefficient μi. The force F acting in the thrust direction of the mandrel bar 4 and the rolling load P _i between each stand are measured in time series over a period of time n, and time series data F ₁ ,...F _k ,...
Obtain F _o and P _i (1),..., P _i(k) ,...P _i(o) . Here, the force F acting in the thrust direction is determined by the following procedure. F=G/R...(2a) G=ηC(V-Ira)I/N...(2b) Here, G: Shaft torque of pinion 11 for restraining mandrel bar 4 R: Radius of pinion 11 η: Torque Transmission efficiency C: Conversion coefficient V: Voltage of motor 6 I: Current of motor 6 ra: Armature resistance of motor 6 N: Number of rotations of pinion 11 (detected by a pulse generator, etc.) Based on this time series data Variance S _i ² of rolling load P _i of each stand, covariance S _ij (j≠0) of rolling loads P _i and P _j of the i-th stand and j-th stand, force F acting on the mandrel bar 4 and each stand rolling load of
The covariance S _ij (j=0) with P _i is calculated using the following equations. S _i ² = 1/n _o 〓 ^k=1 (P _i(k) − _i ) ² = _o 〓 ^k=1 P ² _i(k) −1/n ( _o 〓 ^k=1 P _i(k) ) ² ……(3) S _ij = l/n _o 〓 ^k=1 (P _i(k) − _i ) (P _j(k) − _j )= _o 〓 ^k=1 P _i(k) P _{j(k )} −1/n(ΣP _i(k) P _j(k) )……(4) S _ip =1/n _o 〓 ^k=1 (F _k −)(P _i(k) − _i )= _o 〓 ^k=1 F _k P _i(k) −1/n ( _o 〓 ^k=1 F _k P _i(k) ) ……(5) However, _i = 1/n _o 〓 ^k=1 P _i(k) , = 1/n _o 〓 ^k=1 F _k The reason why the following equation (6) holds true from the above equations (3), (4), and (5) will be described below. μ ₁ P _1(k) + μ ₂ P _2(k) +……μ ₈ P _8(k) =F _(k) ……(6a) Equation (6a) shows the balance equation of the force acting on the mandrel bar 4 . The left side shows the force acting on the bar through the raw tube being rolled by each stand, and the right side shows the force restraining the mandrel bar 4. Equation (6a) holds true at each time point of 1, 2, 3...k... Therefore, (k) is defined as time k
When the subscript is expressed as , equation (6b) holds true. μ ₁ [P _1(k) − ₁ ] + μ ₂ [P _2(k) − ₂ ] + ... μ ₈ [P _8(k) − ₈ ] = F _(k) − ... (6b) Here, _i represents the average value of P _{i (1)} , P _i (2), ... P _{i (k)} .... Also, represents the average value of F ₍₁₎ , F ₍₂₎ , ...F _(k) .... Next, [P _1(k) − ₁ ] and [P _2(k) −
P ₂ ]..., respectively, and calculate the average for the time series k, the following formula is established. μ ₁ S ₁ ² + μ ₂ S ₁₂ +……+ μ ₈ S ₁₈ = S ₁₀ … (7a) μ ₁ S ₂₁ + μ ₂ S ₂ ² +……+ μ ₈ S ₂₈ = S ₂₀ … (7b) … … … μ ₁ S ₈₁ + μ ₂ S ₂₈ +……+ μ ₈ S ₈ ² = S ₈₀ … (7h) When equations (7a) to (7h) are solved simultaneously, μ ₁ , μ ₂ …
Find μ ₈ . As mentioned above, from each variance of the above time series data, the friction coefficient μ ₁ of the mandrel bar of the first stand
is calculated using the following formula.

【table】

Claims (1)

[Scope of Claims] 1. The force and rolling load acting in the thrust direction of the mandrel bar are detected or calculated during rolling on all stands and each time the plate is passed through and through each stand, and the force acting in the thrust direction and the rolling load are distributed. Calculate the friction coefficient between the mandrel bar and the blank pipe in each stand, calculate the torque arm coefficient common to each stand from the friction coefficient, the rolling load of each stand, and the rolling torque of the roll drive motor, and calculate the torque arm coefficient, A method for detecting tension in a mandrel mill, characterized in that the tension acting on a raw pipe during rolling is calculated based on the friction coefficient of each stand, the rolling load, and the rolling torque of a roll drive motor. 2. 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 through/cutting, and calculate the force and rolling load acting on the mandrel bar in each stand by distributing the force acting in the thrust direction and the rolling load. Calculate the friction coefficient between the raw pipes, calculate the torque arm coefficient of each stand using the friction coefficient, the rolling load of each stand, and the rolling torque of the roll drive motor, and calculate the torque arm coefficient, the friction coefficient of each stand, and the rolling A mandrel characterized in that the tension acting on the raw pipe during rolling is calculated based on the load and the rolling torque of a roll drive motor, and the calculated value is sent to a mandrel bar speed regulator, thereby changing the moving speed of the mandrel bar. Mill tension control method.