JPH04157005A - Method for detecting generation of thickness deviation of seamless tube - Google Patents

Abstract

PURPOSE:To reduce defective products by measuring the amplitude of vibration of a shell on the outlet side of an elongator with the measuring sensor of a single axis CCD camera, sending these signals to a means for judging amplitude of vibration, calculating the average value of peak value and raising an alarm when set threshold value is exceeded. CONSTITUTION:The amplitude of vibration of the shell in red heated state on the outlet side of the elongator is continuously measured with the measuring sensor 1 in which the single axis CCD camera 11 is used. The signal of this measured amplitude of vibration is sent to the means 3 for judging amplitude of vibration and the average value of the peak value of amplitude of vibration of the shell per one seamless tube is calculated. When the calculated average value exceeds the threshold value that is preliminarily set, the alarm is raised by sending a signal to an alarming means. When the amplitude of vibration of the shell is grasped, the generation of thickness deviation can be naturally detected. In this way, the thickness deviation that is generated in the shell can be detected on the outlet of the elongator and the generation of defective products due to thickness deviation can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting uneven thickness of a shell that occurs in an elongator during seamless pipe manufacturing.

[Prior Art] Manufacturing of seamless pipes, for example, using a plug mill, is carried out through steps as shown in the process diagram of FIG.

That is, after the round billet 21 is heated to a predetermined temperature in a rotary heating furnace 22, a through hole is opened in the center of the billet 21 in a piercer 23, and a hollow shell 24 is formed.

After the hollow part of the hollow tube 24 is further expanded by an elongator 25, it is passed to a plug mill 26 using upper and lower rolls 27 having semicircular grooves and a cylindrical core metal ( A thin and long seamless pipe 29 is finished by reciprocating between the pipe and the mandrel bar 28 for 2 to 3 passes.

Then, the thin-walled and long seamless pipe 29 is placed on a girder 30 and passed between two inclined left and right cylindrical rolls 31 and a cylindrical mandrel bar 32. The thickness is averaged and the surface is smoothed.

Furthermore, it is passed through a sizing mill 33 and finished into the shape and dimensions of the final product. Then, after being cooled on a cooling stand 34, it is straightened by a straightening machine 35, and then sent to the finishing process. In the manufacturing process of such a seamless pipe, the hollow part of the Elongator 25 is greatly expanded, so it is difficult to form a shell evenly along the entire circumference of the hollow pipe 24, and it is difficult to form a shell evenly along the entire circumference of the hollow pipe 24. Meat occurs.

It is difficult to correct the uneven thickness that occurs in the Elongator 25 in a subsequent process, and it remains as an uneven thickness in the final product, which is disposed of as a product of inferior quality.

[Problems to be Solved by the Invention] The uneven thickness that occurs in the seamless pipe as described above can be solved by conveyor roller i for conveying the seamless steel pipe from the straightening machine 35 shown in FIG. 4 to the finishing line. This condition was discovered only after measuring the wall thickness with a conventional ultrasonic wall thickness gauge, so by the time the uneven wall thickness was noticed, many seamless steel pipes with uneven wall thickness had been manufactured, and many were found at one time. There was a problem that some rejected products occurred.

This invention solves the above-mentioned problems of the prior art,
By detecting the uneven thickness that occurs in the elongator during seamless pipe manufacturing at the elongator outlet, it is possible to reduce the incidence of rejected seamless steel pipes due to uneven thickness.Detection of uneven thickness in seamless pipes. The purpose is to provide a method.

[Means for Solving the Problems] A method for detecting the occurrence of uneven thickness in a seamless pipe according to the present invention is to measure the vibration amplitude of a red-hot shell on the outlet side of an elongator using a uniaxial CC.
A length measurement sensor using a D camera measures the vibration amplitude continuously, and sends the measured vibration amplitude signal to the vibration amplitude pass/fail judgment means, which calculates the average value of the peak value of the shell vibration amplitude per seamless pipe. This is a method for detecting the occurrence of uneven wall thickness in a seamless pipe, in which a signal is sent to an alarm means to issue an alarm when the calculated average value exceeds a preset threshold.

[Operation] The method for detecting the occurrence of uneven thickness in a seamless pipe according to the present invention is based on the uniaxial CC of the vibration amplitude of the red-hot shell on the outlet side of the elongator.
A length measurement sensor using a D camera measures the vibration amplitude continuously, and sends the measured vibration amplitude signal to the vibration amplitude pass/fail judgment means, which calculates the average value of the peak value of the shell vibration amplitude per seamless pipe. When the calculated average value exceeds a preset threshold, a signal is sent to an alarm means to issue an alarm. This is done for the following reasons. That is, the uneven thickness that occurs in the elongator is largely due to the swinging of the mandrel bar.

Therefore, when uneven thickness occurs, the shell of the raw pipe being stretched vibrates vertically and horizontally. Therefore, we investigated the relationship with the thickness unevenness rate. The magnitude of the vibration amplitude of the shell (A) here is the average value of the peak values of multiple amplitudes obtained for each shell, and the thickness unevenness rate α (%) is expressed by the formula (1) It is defined by the formula shown below.

α=100 X (t ma, -t, +,)/l,,,
−(1>However, tllm,・maximum wall thickness (m+o)t,
1. : Minimum wall thickness (mad) fm*m: Nominal wall thickness (am) As a result of the investigation, as shown in Figure 5, there is a difference between the magnitude of the vibration amplitude of the shell (A) and the thickness unevenness rate α (%). were found to have a strong correlation.

Therefore, if you know the vibration amplitude of the shell, you can naturally detect the occurrence of uneven thickness.

In addition, the reason for measuring the vibration amplitude of the shell on the exit side of the elongator is that when uneven thickness occurs, by immediately removing the cause of uneven thickness in the elongator, seamless pipes with uneven thickness can be This is because with only one pipe, uneven thickness can be prevented from occurring in the subsequent seamless pipe.

[Example] A method for detecting the occurrence of uneven thickness in a seamless pipe according to an example of the present invention will be explained with reference to FIGS. 1 to 3. FIG. 1 is a block diagram showing the configuration of equipment used in a method for detecting uneven thickness of a seamless pipe according to an embodiment of the present invention. -Length measurement sensor using axis COD camera! The vibration amplitude of the red-hot shell is continuously measured for one raw tube. Since the shell is stretched and at the same time a rotational force is applied by an inclined roll, the vibration amplitude is measured by tracing the surface of the raw pipe in a spiral shape. Therefore, we are not measuring the amplitude of only one cross section parallel to the axis of the shell's raw pipe, but are measuring the amplitude of all cross sections of the raw pipe, and the state of uneven thickness of the whole raw pipe. can be grasped.

A signal indicating the magnitude of the vibration amplitude measured by the length measurement sensor 1 is sent to the controller unit 2, and is sent to the vibration amplitude pass/fail determination calculation unit 3 as a voltage output proportional to the magnitude of the signal.

The vibration amplitude pass/fail judgment calculation unit 3 includes an Elongator
A signal is sent from the rotation detection unit 4, which detects the rotation of the inclined roll of the elongator, that is, detects that the raw pipe is being stretched by the elongator, and this signal is sent from the An average value of the peak values of vibration amplitude is calculated.

In addition, a setting device 5 that can set a threshold value of vibration amplitude is connected to the vibration amplitude pass/fail judgment calculation unit 3, and it is possible to set a threshold value of vibration amplitude corresponding to the size of the raw pipe and the steel type. It is now possible to do so. Then, when the average value of the peak values of the plurality of vibration amplitudes mentioned above is larger than the set threshold value, a signal is sent to the alarm device 6 to sound an alarm for the breast where uneven thickness has occurred. In addition, a CRT 7 is connected to the vibration amplitude pass/fail judgment calculation unit 3, and the vibration waveform of the shell can be displayed, so the degree of uneven thickness of the shell can be determined from this vibration waveform. .

FIG. 2 is a perspective view showing a state in which the amplitude of the vertical vibration of the red-hot shell while the raw pipe is being stretched by an elongator is measured by a length measurement sensor using a -axis CCD camera. -Axis C
CD camera! In the field of view, the axis 13 of the red-hot shell 12
Only one cross-section in the direction perpendicular to is included. In addition, the vertical field of view of this cross section is that the downward direction is the axis center! 3
The upper end is slightly above the top of the shell.

Single axis CCD camera! (2) An image of the field of view is formed on the built-in image sensor. This signal is then transmitted to the controller 14i:1. Send it, and even D/
It is D/A converted by the A converter 15 and output as a voltage magnitude.

FIG. 3 is an explanatory diagram showing the principle of measuring the amplitude of the vertical vibration of the red-hot shell 12 during elongation of the raw pipe with an elongator, using a length measurement sensor using the -axis CCD camera 11. This measurement method is a method of measuring the amplitude of the vertical vibration of the red-hot shell 12, and is designed to detect fluctuations in the uppermost surface of the red-hot shell 12.

The lens system 16 of the uniaxial CCD camera 11, which is set parallel to the vertical plane passing through the axis 13 of the red-hot shell 12, receives light from the dark light source (hatched part) corresponding to the vertical plane, and the same light from the dark light source (hatched part). Light from bright light sources corresponding to vertical planes enters, and dark areas (l3
part) and bright part 1, and the image of part) is formed.

In order to output photoelectric power according to the illuminance, the image sensor 17 performs binarization of brightness and darkness using the threshold level (THR) of the controller 14, and outputs the number of light-receiving elements of the image sensor in bright and dark areas. Then, a D/A converter outputs a voltage proportional to the number of light receiving elements of the image sensor, and changes in the L2 dimension (changes in the shell) are measured.

[Effects of the Invention] According to the present invention, uneven thickness that occurs in the shell during seamless pipe manufacturing can be detected at the elongator outlet, and the occurrence of rejected products due to uneven thickness can be reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a method for detecting the occurrence of uneven thickness in a seamless pipe according to an embodiment of the present invention, and Fig. 2 is a perspective view showing a state in which the amplitude of vertical vibration of a red-hot shell is measured by a length measurement sensor. , Figure 3 is an explanatory diagram showing the principle of measuring the amplitude of the vertical vibration of the red-hot shell with a length measurement sensor, Figure 4 is a process diagram showing the manufacturing process of seamless pipes, and Figure 5 is an illustration of the vibration amplitude of the red-hot shell. It is a graph showing the relationship between size and thickness unevenness rate α. 1. Length measurement sensor, 2. Controller unit, 3.
... Vibration amplitude pass/fail judgment calculation unit, 4... Rotation detection unit, 5 Setting device, 6... Signal alarm device, 7.
CRT, 11...-axis CCD camera, 16... Lens system 16.17... Image sensor.

Claims (1)

[Claims] The vibration amplitude of the red-hot shell on the exit side of Elongator is continuously measured with a length measurement sensor using a uniaxial CCD camera, and the measured vibration amplitude signal is sent to the vibration amplitude pass/fail judgment means. A seamless pipe characterized in that the average value of the peak values of the shell vibration amplitudes per hit is calculated, and when the calculated average value exceeds a preset threshold value, a signal is sent to an alarm means to issue an alarm. Method for detecting uneven thickness.