JP2001121203A - Thickness non-uniformity monitoring method of seamless pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly estimate and identify the causes of thickness non-uniformity, and to take an appropriate thickness non-uniformity preventive action in an early stage in manufacturing a seamless pipe. SOLUTION: In a thickness non-uniformity monitoring method of the seamless pipe, the condition of generating the thickness non-uniformity is monitored by continuously measuring the vibrating condition of a bored or rolled stock pipe by using a two-axis CCD camera arranged orthogonal to each other on the outlet side of inclined rolls in the case of manufacturing the seamless pipe obtained by boring or rolling the stock pipe by a pair of the inclined rolls and plugs located between the inclined rolls. Further, in the thickness non-uniformity monitoring method of the seamless pipe, the measurement value is Fourier-transformed to estimate the causes of generating the thickness non-uniformity from he periodicity of the vibration. Still further, in the thickness non-uniformity monitoring method of the seamless pipe, the causes of generating the thickness non-uniformity is identified based on the measurement value obtained by continuously measuring temperature distribution in the longitudinal direction of the stock material or the stock pipe and/or the load distribution of the inclined rolls.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring the state of uneven wall thickness that occurs when a seamless pipe is pierced or rolled by using a pair of inclined rolls and a plug. By measuring the vibration condition of the raw or perforated tube as a vibration vector and simultaneously measuring the temperature distribution in the longitudinal direction of the material or the tube or / and the load distribution of the inclined roll, the cause of uneven wall thickness The present invention relates to a method for predicting and specifying a thickness variation of a seamless pipe.

[0002]

2. Description of the Related Art As a method of manufacturing a seamless tube by hot working,
The so-called Mannesmann pipe manufacturing method is widely used. In this pipe making method, a solid material billet heated to a high temperature is used as a material to be rolled, and the material billet is fed to a drilling machine (a so-called piercer), and the shaft center portion is bored to form a hollow material. Get the tube. Next, the obtained hollow shell is passed through an elongator having the same configuration as that of the drilling machine as it is or if necessary, after being expanded and thinned, fed to a subsequent elongation rolling machine such as a plug mill or a mandrel mill. And stretch-roll. After that, it passes through a stretch reducer, a reeler, a sizer, and the like, and then undergoes a polishing process for correcting the shape and performing a sizing process to produce a seamless tube as a product.

Conventionally, there is no means for effectively monitoring the occurrence of wall thickness unevenness during drilling or rolling, and the wall thickness of the pipe is measured in the refining process, which is the final stage of the above-mentioned pipe manufacturing, to measure the wall thickness. In the case where has occurred, a method of controlling the setting conditions of the heating furnace and the rolling mill based on the measurement result has been adopted. However, according to such a method, many defective thickness deviation materials were manufactured until the occurrence of deviation in thickness was found, and a practical effect could not be expected.

[0004] Therefore, during piercing rolling or elongation rolling, vibrations appearing in a rolled shell (shell) are measured,
Various methods for monitoring the occurrence of uneven thickness have been proposed. For example, in JP-A-59-159218, a line sensor camera is used to continuously measure the vibration condition of the longitudinal method of a raw tube during rolling, and the measured value is subjected to Fourier transform to generate uneven thickness. There has been proposed a method of monitoring the thickness deviation state from the cycle.

In Japanese Patent Application Laid-Open No. 61-119318, a wobble amplitude of a mandrel bar and a hollow shell whose center is deviated due to uneven wall thickness is measured by using a displacement measuring device of a laser beam irradiation type, so that it can be drilled or drilled. A method for monitoring the occurrence of uneven thickness during rolling has been proposed.

Further, in Japanese Patent Application Laid-Open No. Hei 4-1577705, the vibration width of the shell on the exit side of the drilling machine is continuously measured using a single-axis CCD camera, and the average of the peak values of the measured vibration width of the shell is measured. A method for detecting occurrence of uneven thickness from a value is disclosed.

[0007]

Generally, when a seamless pipe is pierced or rolled, the vibration displacement of the pipe moving while turning along the pass line is not only the vertical vibration displacement but also the horizontal vibration displacement. The displacement is also combined. On the other hand, in the conventionally proposed method of monitoring uneven wall thickness, a line sensor camera, a laser beam irradiation type displacement measuring device, or a one-axis CCD camera is used for measuring the vibration of the raw tube,
It is limited to one-dimensional vibration displacement measurement. Therefore, even if the vibration appearing in the raw pipe on the exit side of the drilling machine or rolling mill is measured to monitor the occurrence of uneven wall thickness, the actual vibration displacement of the raw pipe cannot be measured, and the accurate uneven wall thickness cannot be measured. It is difficult to grasp the occurrence.

In the production of seamless pipes in actual operation, upon detecting the occurrence of wall thickness deviation, immediately prevent the material billet from being thermally deviated, adjust the eccentricity of the drilling plug, or adjust the eccentricity of the drilling machine. Unless the meat improvement treatment is performed, it is not possible to prevent a large amount of uneven thickness defective material from being generated. However, simply monitoring and detecting the occurrence of uneven thickness as in the conventional uneven thickness monitoring method cannot predict and identify the cause of occurrence of uneven thickness, so that appropriate measures cannot be taken at an early stage. For this reason, the occurrence of some uneven thickness defective material has been unavoidable.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems associated with the conventional method for monitoring the uneven thickness of a seamless pipe. Vibration displacement is measured as a vibration vector, which enables accurate monitoring of the occurrence of thickness unevenness, predicts and specifies the cause of thickness unevenness, and enables early and appropriate measures to prevent thickness unevenness. It is an object of the present invention to provide a seamless pipe uneven thickness monitoring method capable of minimizing the occurrence of defects even when the occurrence of cracks.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides the following (1) to (3) methods of monitoring uneven thickness of a seamless pipe.

(1) Manufacture of a seamless pipe in which a raw material is pierced or rolled by a pair of inclined rolls opposed to each other around a pass line and plugs arranged along the pass line so as to be located between the inclined rolls At this time, the vibration state of the perforated or rolled tube is continuously measured using a biaxial CCD camera arranged orthogonally on the exit side of the inclined roll, and the occurrence of uneven thickness is monitored based on the measured value. This is a seamless pipe thickness variation monitoring method characterized in that:

(2) In the seamless pipe thickness variation monitoring method of the above (1), the measured value is subjected to Fourier transform, and the cause of the thickness variation is predicted from the periodicity of the vibration. This is a method for monitoring uneven thickness without pipes.

(3) In the method for monitoring uneven wall thickness of a seamless pipe of the above (2), the temperature distribution in the longitudinal direction of the raw material or the raw pipe or / and the load distribution of the inclined rolls are continuously measured, and these measurements are performed. This is a seamless pipe thickness variation monitoring method characterized by specifying the cause of the thickness variation based on a value.

The present invention has been completed based on the following findings. The present inventors examined various seamless pipe thickness variation monitoring means and prediction methods of the cause of occurrence in order to more accurately grasp the thickness variation situation, and as a result, switched to the conventional one-dimensional vibration displacement measurement. Then, the vibration displacement was measured using a two-axis CCD camera arranged orthogonally, and the vibration displacement was determined.

FIG. 1 is a diagram for explaining a situation in which the vibration displacement of a raw tube is measured by a two-axis CCD camera which is arranged orthogonally so that scanning lines intersect at 90 °. FIG. FIG. 3B shows a planar arrangement, and FIG. 3B shows an operation of measuring a two-dimensionally generated vibration displacement of the raw tube as a vibration vector.
As shown in FIG. 1A, the two-axis CCD camera 5 includes a camera 5a that scans in the horizontal direction and a camera 5b that scans in the vertical direction on the paper. Then, the two-dimensionally generated vibration of the element tube 2p is measured separately for the vibration a which can be measured by the camera 5a and the vibration b which can be measured by the camera 5b. Thereafter, as shown in (b), the vibration a and the vibration b are combined and grasped as a vibration vector.

Since the vibration vector measured by the two-axis CCD camera 5 is raw data of the vibration displacement, the vibration characteristic cannot be recognized by itself. Therefore, by performing a Fourier transform on the measured value of the vibration vector,
The cause of the uneven thickness can be predicted from the periodicity of the vibration. Furthermore, the temperature distribution in the longitudinal direction of the material or raw tube,
It has been found that, by continuously measuring the load distribution of the inclined rolls and / or by combining these measured values, accurate wall thickness analysis becomes possible and the cause of the wall thickness unevenness can be specified.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The first characteristic feature of the uneven thickness monitoring method of the present invention is that two CCD cameras are arranged orthogonally to measure the vibration displacement of a raw tube after rolling, and to grasp it as a vibration vector. It is. Next, the second feature is that the cause of the occurrence of uneven thickness can be accurately predicted by performing Fourier analysis on the measured value of the vibration vector.

Further, by measuring the temperature distribution in the longitudinal direction of the raw material or the raw tube, it is possible to judge the state of heat deviation of the raw material billet before perforation or rolling, and to measure the tool distribution by measuring the load distribution of the inclined roll. Alternatively, a third feature is that a defect of the drilling machine or the rolling mill can be determined. Hereinafter, the first to third features of the present invention will be described with reference to the drawings and specific measurement data.

FIG. 2 is a schematic diagram showing the configuration of a drilling machine to which the thickness variation monitoring method of the present invention is applied. The pair of inclined rolls 1 and 1 are arranged to face a target with respect to a pass line XX serving as a movement axis of the material 2 to be rolled in the rolling direction in the rolling direction. In the punching machine in which the inclined rolls 1 and 1 are arranged as described above, the material 2 fed on the pass line XX is bitten between the inclined rolls 1 and 1 and then rotates while passing through the pass line XX. After moving on the X, a hole is made in the axial core portion by the plug 3 to form a hollow shell (pierced shell) 2p.
During this time, the plug 3 is supported by the mandrel bar 4 so as to be located between the inclined rolls 1 and 1 along the pass line.

In the piercing and rolling having such a configuration, uneven wall thickness occurs in the raw tube after piercing due to factors such as uneven heat of the material billet, eccentricity of the plug, bending of the mandrel bar, or misalignment of the piercing machine. . For this reason, two CCD cameras 5 arranged so as to intersect at 90 ° are arranged in order to measure the vibration displacement of the tube after drilling. However, in the drawing,
For convenience, two CCD cameras 5, 5 are shown facing each other with the tube 2p interposed therebetween.

Next, in order to measure the temperature distribution in the longitudinal direction of the raw tube 2p, a radiation thermometer 6 is installed on the exit side of the inclined roll 1. Since the measurement of the temperature distribution is for confirming whether or not the material billet is deflected, a radiation thermometer 6 may be provided on the entrance side of the inclined roll 1 to measure the temperature distribution of the material 2. Further, a load cell 7 for measuring the load distribution of the pair of upper and lower inclined rolls is arranged.

The raw data measured by the CCD camera 5, the radiation thermometer 6, and the load cell 7 are processed by the analog / digital converter 8, and thereafter, the monitor 9 observes the digitally converted measured values. Can be.

According to the thickness variation monitoring method of the present invention, by employing the above-described configuration, it is possible to not only monitor the occurrence state of the thickness variation but also to predict and specify the cause of the occurrence. The contents will be described using the drilling machine shown in FIG.

1. Monitoring of the state of occurrence of uneven wall thickness FIG. 3 is a diagram showing the vibration displacement of a raw tube measured by two CCD cameras as a vectorized amount of vibration.
The drilling conditions at this time were low alloy steel (0.2
% C-2% Cr) and heated at 1230 ° C, starting from the material (billet) size 191φ × L, the raw tube size 196φ × 20mm wall thickness × L
Perforated.

FIG. 4 is a diagram showing the relationship between the amount of vibration shown in FIG. 3 and the uneven wall ratio {(maximum thickness-minimum thickness) / maximum thickness} at that time. As can be seen from FIG.
As the vibration amount of the raw tube increases, the wall thickness deviation rate of the raw tube increases accordingly. Therefore, the occurrence of uneven wall thickness can be monitored by continuously measuring the vibration of the pipe after drilling. In particular, by using a two-axis CCD camera as in the monitoring method of the present invention, the occurrence state of uneven thickness can be accurately grasped.

2. Prediction of Cause of Thickness Variation Since the vibration amount shown in FIG. 3 is raw data obtained from a CCD camera, it is not possible to grasp the occurrence characteristics of thickness deviation based on periodicity alone. Therefore, a power spectrum is obtained by Fourier-transforming the measured data, and the power spectrum is associated with a cause of occurrence of each uneven thickness. The thickness variation caused by each of the occurrence factors has a periodicity, and the cycle differs from one to another.

FIG. 5 is a diagram showing the result of Fourier transform of the vibration amount shown in FIG. This makes it possible to predict the cause of the uneven thickness. In the figure, the strong occurrence in the frequency range of 0 to 0.5 Hz indicates that the vibration of the raw tube 2p increases in a period of 2 to 3 m. This period coincides with the pitch of the twist generated by the difference between the rotation speed of the raw tube 2p and the rotation speed of the material 2, and the cause is as follows.
It is predicted that the material 2 is deviated in the heating furnace.

Next, the reason why the vibration is strongly generated in the frequency range of 1 to 2 Hz is that the vibration of the raw tube 2p is strongly generated in a cycle of 1 to 1.5 m. This cycle is a pitch caused by a difference in peripheral speed between the raw tube 2p and the plug 3, and is caused by a swing of the plug 3 itself. The cause of the deflection of the plug 3 is caused by the bending of the mandrel bar 4 or the misalignment of the rolling mill body. Therefore, the vibration amount of the raw tube is
If it falls within the range of 25 Hz, it can be predicted that the cause is insufficient setting of the mandrel bar 4 or the rolling mill body.

Further, the strong occurrence in the frequency range of 6 to 7 Hz indicates that the vibration of the raw tube 2p increases in a cycle of 130 mm to 150 mm. This cycle coincides with the pitch of one rotation of the raw tube 2p, and can be predicted to be caused by the eccentricity of the plug 3, that is, the irregular surface shape of the plug 3.

3. Identifying the cause of uneven wall thickness Further, by measuring the temperature distribution in the longitudinal direction of the raw material or raw tube or the load distribution of the inclined roll, the cause of occurrence can be accurately identified. In the present invention, the measurement of the temperature distribution and the measurement of the roll load may be performed simultaneously or independently.

FIG. 6 is a diagram showing the result of measuring the temperature distribution in the longitudinal direction of a rotating pipe by a radiation thermometer. There is uneven heat in the material, and due to this temperature difference, the temperature oscillates each time the tube rotates once. The vibration width of this temperature and the wall thickness deviation ｛(maximum thickness-minimum thickness) / maximum In order to grasp the relationship with the thickness｝, the maximum value of the vibration width is defined as the amount of heat deviation.

FIG. 7 is a diagram showing the relationship between the amount of heat deviation of the raw tube and the wall thickness deviation generated at that time. From FIG. 7, as the amount of heat deviation increases, the amount of wall thickness deviation of the raw tube increases accordingly.

As described above with reference to FIG.
It is predicted that the cause of the vibration of the raw tube 2p that is strongly generated in the range of z is the uneven temperature of the raw material 2 in the heating furnace. Furthermore, by grasping the state of unbalanced heat of the material from FIG.
The cause of the vibration can be specified, and immediately, the uneven thickness improvement measure by changing the setting of the heating furnace can be implemented. In addition, the uneven thickness ratio generated in the raw tube at this time can be estimated from FIG.

FIG. 8 is a view showing the result of measuring the load distribution of the inclined roll by the load cell. In FIG. 8, it is possible to grasp the state of the drilling and the trouble of the drilling machine from the angle at which the roll load increases from the initial value, the roll load waving at the time of punching, or the balance of the right and left roll loads.

For example, the vibration of the raw tube 2p that is strongly generated in the frequency range of 1 to 2 Hz is caused by the vibration of the plug 3 itself. At this time, when the right and left roll loads are different from each other in the load distribution of the inclined rolls shown in FIG. 8, it can be specified that the run-out of the plug 3 is caused by the misalignment of the rolling mill main body. When the roll loads are not different, it can be specified that the deflection of the plug 3 is caused by the bending of the mandrel bar 4.

As described above, in the method for monitoring uneven thickness of the present invention,
Combination of vibration measurement with a two-axis CCD camera, measurement of temperature distribution with a radiation thermometer, and measurement of load distribution of an inclined roll with a load cell, convert the measured values and display them on a monitor, thereby immediately causing uneven thickness. The situation and the cause of occurrence can be predicted and specified, and measures for preventing uneven thickness such as a change in the operating conditions of the heating furnace, a change in the setting of the drilling machine, and a change in the tool can be taken early and appropriately.

[0037]

According to the seamless pipe unevenness monitoring method of the present invention, it is possible to grasp the state of uneven wall thickness that occurs during pipe making by drilling or rolling and accurately predict and specify the cause of the occurrence.
As a result, it is possible to take early and appropriate measures for preventing uneven thickness, to significantly reduce uneven thickness and improve the yield of the final product.

[Brief description of the drawings]

FIG. 1 is a view for explaining a situation in which vibration displacement of a raw tube is measured by a two-axis CCD camera which is arranged orthogonally so that scanning lines cross at 90 °.

FIG. 2 is a schematic diagram showing a configuration of a drilling machine to which the thickness unevenness monitoring method of the present invention is applied.

FIG. 3 is a diagram showing a vectorized vibration displacement of a raw tube measured by two CCD cameras and showing it as a vibration amount.

FIG. 4 is a diagram showing the relationship between the amount of vibration shown in FIG. 3 and the uneven wall thickness ratio {(maximum thickness−minimum thickness) / maximum thickness} at that time.

FIG. 5 is a diagram showing a result of Fourier transform of the vibration amount shown in FIG. 3;

FIG. 6 is a view showing a result of measuring a temperature distribution in a longitudinal direction of a turning pipe by a radiation thermometer.

FIG. 7 is a diagram showing a relationship between the amount of heat deviation of the raw tube and the wall thickness deviation generated at that time.

FIG. 8 is a diagram showing a result of measuring a load distribution of an inclined roll by a load cell.

[Explanation of symbols]

 1: inclined roll 2: material, 2p: pipe 3: plug 4, mandrel bar 5: CCD camera, 6: radiation thermometer 7: load cell 8: analog / digital converter 9: monitor

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Claims (3)

[Claims] 1. A method of manufacturing a seamless pipe in which a raw material is pierced or rolled by a pair of inclined rolls arranged opposite to each other around a pass line and a plug arranged along the pass line so as to be located between the inclined rolls. Continuously measuring the vibration state of the perforated or rolled raw tube using a two-axis CCD camera arranged orthogonally on the exit side of the inclined roll, and monitoring the occurrence state of uneven thickness based on the measured value. A method for monitoring uneven wall thickness of a seamless pipe, characterized by the following. 2. A method for monitoring uneven thickness of a seamless pipe according to claim 1, wherein the measured value is subjected to Fourier transform to predict a cause of occurrence of uneven thickness of the seamless pipe. . 3. The method for monitoring uneven thickness of a seamless pipe according to claim 2, further comprising continuously measuring the temperature distribution in the longitudinal direction of the raw material or the raw pipe and / or the load distribution of the inclined roll. A method for monitoring uneven thickness of a seamless pipe, characterized in that a cause of occurrence of uneven thickness is specified based on a value.