JPS5976609A - Method for controlling tension of mandrel bar in piercing mill - Google Patents

Abstract

PURPOSE:To make the wall thickness and roundness of a product highly accurate, by providing a tension detector to a mandrel bar, and keeping a tension of mandrel bar constant by changing the rotating speed of barrel-shaped rolls in accordance with the variation of the tension. CONSTITUTION:A piercing mill has a rolling device consisting of a plug 2 held by a mandrel bar 1 and two barrel-shaped rolls 3a, 3b, and rolls a blank pipe 6 by the plug 2 and the rolls 3a, 3b. A tension detector 10 detecting a tension TB acting on the mandrel bar 1 and a load cell 11 detecting a rolling load of the roll 3b are provided to the device. Respective detecting signals S1, S2 are transmitted to a calculator 12 to calculate so that the mandrel tension conforms with a tension value set by a tension setter 16. This signal is transmitted to a motor through a speed controller 17 and a motor power source 18 to change the rotating speeds of rolls 3a, 3b thereby the tension TB acting on the mandrel bar 1 is kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a mandrel par tension control method for a piercer mill, which maintains the tension acting on the mandrel pars constant to perform uniform rolling.

[Technical field of invention]

This type of piercer mill, as shown in Item 1, has a rolling device consisting of a plug 2 held at the tip of a mandrel part 1, and barrel-shaped rolls 3a+ and 3b arranged vertically to face each other. Have a mandrel,? , -1 is shown with a thrust block 4 connected to the proximal end side through a rack 5 7
The hollow thick-walled raw pipe 6 is perforated by moving it with a motor. - The thrust block 4 is provided with a launch device 7 for mechanically preventing it from being pushed back through the mandrel parts 1 during rolling.

In the case of a small-diameter pipe, for example, the raw pipe rolled by a piercer mill is rolled into a predetermined wall thickness by a mandrel machine, which is a continuous rolling mill, after inserting a mandrel into the raw pipe in the shape of a skewer. There are many things to be done.

[Problems with dorsal plasma technology]

However, with the above type of piercer mill, due to changes in the temperature distribution of the raw tube and changes in the thermal expansion of the plug that occurs during rolling,
The diameter and wall thickness of the raw pipe fluctuate! , the compressive tension (hereinafter referred to as tension) acting on the mandrel pass ζ- causes the wall thickness of the rolled product to become uneven, making it difficult to produce a product with a desired wall thickness.

[Purpose of the invention]

The present invention has been made in view of the above points, and when the diameter and wall thickness of the raw pipe changes, the mandrel parts change accordingly.
Taking into consideration the fact that the tension acting on the mandrel varies, the barrel-shaped roll of the piercer mill is installed to detect the tension acting on the mandrel and respond to this, thereby reducing the tension acting on the mandrel. Piercer mill mandrels that maintain a constant value and achieve high precision in product wall thickness and roundness.
The purpose is to provide a tension control method.

[Summary of the invention]

An object of the present invention is to attach a tension detector to the mandrel parts that hold the plug, and to vary the rotational speed of the barrel-shaped roll according to fluctuations in the tension of the mandrel parts measured by the tension detector. This is achieved by a piercer mill mandrel tension control method that keeps the tension constant.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, the same members as in FIG. 1 are given the same reference numerals.

In FIG. 2, the reference numeral 10 denotes a tension detector, which is disposed between the thrust lever 4 and the mandrel lever 1, and the tension TB applied to the mandrel member 1. I am trying to detect it. A load cell 11 for detecting the rolling load is attached to the frozen barrel-shaped roll 3b, and a detection signal S of the tension detector 1 (1) is attached to the frozen barrel-shaped roll 3b.
1 and the detection signal S2 of the load cell 11 is detected by the computer 12.
It is now sent to

On the other hand, a motor current detector 13, a motor rotational speed detector 14, and a motor pressure detector 15 are attached to the drive motor of the barrel-shaped roll 3b, and each detection signal S3+
S4+S5 are sent to the computer 12.

Then, in the computer 12, the detection signal S1? S
2 +S3. S4. S5 is calculated, and the tension setting device 16
The tension value is set at , and the calculated signal is
The speed control device 17 and the motor power supply device 181C are sent to control the voltage of the motor 12, thereby controlling the voltage of the motor 12.
The rotation speed of is controlled.

Next, the relationship between rolling load and rolling torque when rolling the raw pipe 6 will be explained.

If the rolling load of the barrel roll is P1, the rolling torque is 01, the friction coefficient between the plug and the raw pipe is μ, then G=TB-R+2a-
P・・・・・・・・・(1) Here, R is the average roll radius of the barrel-shaped roll, and a is 2a = G in rolling of plate materials, etc.
/P f The value corresponding to the physical quantity expressed, TB is the tension acting on the mandrel par.

Since the plug and the raw pipe always have a relative velocity, μ is the coefficient of kinetic friction, and T −2・μ・P satisfies the following relational expression.
・・・・・・・・・(2) − From equations (1) and (2), G = (2μR+2a) P −−・(3)
As is clear from the above equation, if the tension TB acting on the mandrel pass ζ- fluctuates, the rolling torque and rolling load will fluctuate, thereby preventing stable rolling.

Generally, the rolling torque G is calculated by the following formula when a torque converter is not installed.

Here, V is the motor voltage, ■ is the motor current, R is the armature resistance, N is the motor rotation speed, and β+r+δ is a constant.

The first term on the right side is motor torque, the second term is acceleration/deceleration torque, and the third term is loss torque.

However, when rolling the raw pipe 6 in the piercer mill,
The tension acting on the mandrel-1 is detected by the tension detector 10, and its output value TB and the rolling load value P detected by the load cell 11 are sent to the computer 12, and at the same time, the detection by the motor current detector 13 is sent to the computer 12. Current value detected by the detector 13 11 Output value N detected by the motor rotation speed detector 14
1 and the voltage value V detected by the motor voltage detector 15 are also sent to the computer 12, where they are calculated.
The rotational speed of the barrel-shaped roll 3b is adjusted by controlling the rotational speed of the drive motor of the speed control device W17 so that the tension value set by the tension setting value 16 is reached, and the tension acting on the man plate is reduced. It will be kept constant.

〔Effect of the invention〕

As described above, according to the present invention, since the rotational speed of the barrel roll changes in accordance with fluctuations in the tension of the mandrel nozzles, the tension acting on the mandrel nozzles can be kept constant.
Therefore, the diameter, wall thickness, and roundness of the raw tube to be rolled are more uniform than in the conventional method, and the quality of the product can be improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of a piercer mill, and FIG. 2 is a schematic diagram of an apparatus for carrying out the method for controlling mandrel knot tension in a piercer mill according to the present invention. ■...Mandrellino-12...Hula f, 3 a
, 3 b... Barrel-shaped roll, 4... Thrust block, 6... Base tube, 10... Tension detector, 11...
Load cell, 12... Calculator, 16... Tension setting device. Applicant's agent Kiyohato Inomata 11] a.

Claims (1)

[Claims] A piercer mill has a rolling device consisting of a plug held by a mandrel parr and two barrel-shaped rolls, and the raw pipe is rolled by the practo barrel-shaped rolls.
Mandrel? - A tension detector is attached to the mandrel parts, and the rotation speed of the barrel-shaped roll is varied according to the fluctuation of the tension of the mandrel parts being screened by this tension detector.
A tension control method for mandrel pars in piercer mills that takes advantage of keeping the tension acting on the piercer mill constant.