JPH07314291A - Monitoring device for bead cut state of electro-resistance-welded tube inner surface - Google Patents

Abstract

PURPOSE:To detect the cut state of an inner surace bead surely and speedily, suppress the generation of the cutting trouble of the inner surface bead to the min. and avert the reduction pf yield of an electro-resistance-welded tube and the deterioration of the operation rate of a manufacturing line. CONSTITUTION:A monitoring device is equipped with an inner surface mandrel bar 7 having a cutting tool for cutting the inner surface bead of a seam welded pipe, element (e.g. vibration sensor) 1 for detecting the vibration of the inner surface mandrel bar 7, and a means 4 which compares the vibration output supplied from the element for detecting the vibration and the set standard vibration and judges the cut state. The standard vibration state is divided into the case where the standard value of the vibration level is used, the case where the standard value of the amplitude difference is used, and the case where the standard value of the inclination of the vibration level is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner bead cutting condition monitoring device for an electric resistance welded pipe, and more particularly to wear, breakage of an inner bead cutting tool and damage to an inner mandrel bar for mounting the cutting tool, and inner bead. The present invention relates to an electric resistance welded pipe inner surface bead cutting state monitoring device for detecting height defects, internal surface flaws, and micro-bead or flash hooking flaws.

[0002]

2. Description of the Related Art A method of manufacturing an electric resistance welded pipe is a method in which a strip steel inserted from an entry facility is roll-formed into a tubular shape, formed into a predetermined shape that is easy to weld, and then continuously welded, which is excellent in productivity. It is a pipe making method. FIG. 2 is a diagram showing an outline of a process for manufacturing an electric resistance welded pipe, which will be described later. As shown in the drawing, in the electric resistance welded pipe manufacturing line, the strip steel inserted into the forming roll stand 8 is sequentially piped as an open pipe 9. After being molded into a work coil (inductor) 12
It is heated and melted by the induced current. After that, the open pipe 9 is pressure-bonded by the squeeze roll 13 to form the continuously welded electric resistance welded pipe 10.

When the open pipes 9 are continuously welded, after pressure-bonding by the squeeze roll 13, a surplus called "bead" is formed on the inner edge portion of the electric resistance welded pipe which is the pressure-bonded portion. The shape of the inner bead changes depending on the crimping conditions,
Further, the allowable range of the inner bead height differs depending on the application of the electric resistance welded pipe, and the inner bead is cut so as to meet a predetermined accuracy. Although bead cutting may be done off-line outside the production line, squeeze rolls are generally used.
The online cutting that is performed immediately after leaving is adopted.

In the online cutting of the inner bead, a cutting tool 11 is attached to the tip of an inner mandrel bar 7 detachably attached to the forming roll stand 8 on the side where the manufacturing line enters, and the cutting tool 11 is installed in the line advancing direction of the electric resistance welded pipe. The beads are cut by the cutting tool 11 by using the transfer force.

A problem with bead cutting of electric resistance welded pipes is that the cutting bite is worn or chipped, or bead cuttings and welding flash are clogged in the gap between the inner surface of the electric resistance welded pipe and the inner mandrel bar. As a result, the inner mandrel bar is damaged, resulting in defective cutting of the inner bead and deterioration of the operating rate of the manufacturing line. In addition, the inner bead is not cut within the specified tolerance range, so-called defective inner bead height occurs, or inner surface flaws or hook defects due to bead scraps, etc., also deteriorate the quality of the electric resistance welded pipe. However, it causes a decrease in yield and must be avoided.

In general, the quality of the inner bead cutting state in the manufacturing line, that is, the presence or absence of wear or loss of the cutting bite or the inner bead height defect, is determined at the rear of the line considerably separated from the place where the bead cutting is performed. After the pipe is cut by the traveling cutting machine provided, it is performed by touching the end of the pipe with a finger or by a micrometer. Therefore, even if the operator finds an abnormal cutting of the inner bead and immediately stops the machine, the electric resistance welded pipe after the place where the bead cutting is performed becomes a defective product or a downgraded product, which reduces the yield and quality. Not only that, but also the productivity of the production line is significantly deteriorated.

In order to solve the above-mentioned problem of bead cutting on the inner surface of the electric resistance welded pipe manufacturing line, the following monitoring device has been conventionally proposed.

In Japanese Patent Laid-Open No. 54-102681, a strain gauge for detecting the cutting reaction force and its variation is attached to the holding portion of the inner surface mandrel, and the output from this strain gauge changes below a set reference value. There is a proposal for an apparatus for detecting tool wear and tool breakage, which comprises a means for judging the change and a means for judging that this change has continued for a certain time. In other words, this device detects the cutting reaction force of the cutting tool through the strain gauge, and detects the cutting tool loss by comparing it with the set reference value. It is difficult to set the reference value for the output of. This set reference value is based on a number of parameters such as specifications of the inner mandrel bar (dimensions, materials, etc.), cutting tool conditions (shape, support method, etc.), pipe making conditions (materials, dimensions, cutting resistance, etc.). This is because there is always the problem of how to use the judgment criteria that match the operating conditions of the production line, and it is not possible to set an appropriate reference value for each condition of the production line. Further, the fact that the strain gauge itself for detecting the cutting reaction force of the cutting tool has a relatively short life is another reason why it cannot be applied in practice.

On the other hand, an apparatus has been developed which detects wear and damage of a cutting tool by directly monitoring the cutting shape of the inner bead in the electric resistance welded pipe manufacturing line. For example, a cutting device, a detection device for detecting a state after cutting, and a device for accurately controlling a cutting cross section based on a brightness difference between a cutting portion and a base material portion which is a non-cutting portion on the basis of the result (Japanese Patent Application Laid-Open No. Hei 5- 6921
No. 8) or a device for monitoring the cutting condition of the inner bead provided with means for transmitting the light projected to the inner bead and the reflected light from the inner bead at the tip of the inner mandrel bar (JP-A-3). -234444 gazette and other references). However, in these device configurations, a device for detecting a bead cutting condition such as a camera has to be inserted into the inner surface of the electric resistance welded pipe, and there is a limitation that it cannot be applied to the electric resistance welded pipe having a small diameter. Further, these apparatuses have a problem that not only the structure of the apparatus but also the method for determining the abnormal cutting are complicated, and the operator cannot deal with them and cannot be applied to the production line.

Japanese Unexamined Patent Publication (Kokai) No. 54-21372 features an ultrasonic probe provided with an ultrasonic lens for inputting a minute spot-shaped ultrasonic wave to an electric resistance welded tube and further receiving a reflected echo signal. An inner bead cutting shape measuring device has been proposed. This device not only detects the wear of the cutting tool and the breakage of the cutting tool by online ultrasonic flaw detection, but also directly monitors the shape of the cutting bead by the monitor during the manufacturing of the electric resistance welded pipe. Therefore, it is becoming the mainstream of the device for monitoring the inner bead cutting shape. However, this device is expensive and, on the other hand, there is a problem in that the S / N ratio deteriorates due to vibrations and the like that accompany bead cutting, and the detection performance such as breakage of the cutting bite decreases.

[0011]

SUMMARY OF THE INVENTION The present invention overcomes the problems of the prior art described above, has a simple device configuration, is easily applied to a production line, and is compatible with all pipe making sizes. It is an object of the present invention to provide an inexpensive electric resistance welded pipe inner surface bead cutting condition monitoring device at low cost.

[0012] Further, all of the conventional devices mainly detect the wear and breakage of the cutting tool,
Since damage to the inner mandrel bar cannot be ignored as a factor that lowers the yield of the electric resistance welded pipe and further deteriorates the operating rate, the present invention also covers the monitoring of inner mandrel bar damage.

Further, the quality of the electric resistance welded pipe is affected as well as the extreme abnormal cutting such as the wear of the cutting bite, the breakage of the inner surface mandrel bar and the immediate failure of the electric resistance welded pipe and the stop of the production line. It is also an object of the present invention to provide an apparatus capable of determining the occurrence of internal surface bead height failure, internal surface flaws, or hooking flaws due to bead scraps or the like.

[0014]

The gist of the present invention is, as shown in FIGS. 1 and 2, the following apparatus (1) to (4) for monitoring the bead cutting state on the inner surface of the electric resistance welded pipe.

(1) An inner surface mandrel bar 7 equipped with a cutting tool 11 for cutting an inner surface bead of an electric resistance welded pipe 10, an element (for example, a vibration sensor) 1 for detecting the vibration of the inner surface mandrel bar, and the vibration. And a means 4 for judging a cutting state by comparing the output of the vibration from the element with a set reference vibration.

(2) The means for determining the cutting state described in (1) is used for a predetermined time when the vibration output exceeds a preset vibration level reference value or a vibration level reference value determined by the following equation (A). A bead cutting state monitoring device for an inner surface of an electric resistance welded pipe, which is a means for determining whether or not it has continued.

Vibration level reference value = K · a ₀ ... (A) where K: coefficient, a ₀ : vibration level at normal time (3) The means for determining the cutting state described in (1) is vibration. Is a means for judging whether or not the output exceeds the reference value of the amplitude deviation defined by the following formula (B) and continues for a certain period of time.

Amplitude deviation reference value = K · b ₀ (B) where K: coefficient, b ₀ : normal amplitude deviation (4) The means for determining the cutting state described in (1) is as follows. The reference slope (Δ of the vibration level determined by the equation (C)
g) or a means for determining whether or not a reference value of a preset vibration level has been exceeded, a bead cutting state monitoring device for an inner surface of an electric resistance welded pipe.

Reference slope (Δg) of vibration level = K · c ₀ / T (C) where K: coefficient, c ₀ : normal vibration level,
T: Elapsed time In applying the electric resistance welded pipe inner surface bead cutting state monitoring device according to (1) to (4) above to a production line, the recorder 3 and an alarm are provided from the viewpoint of operator convenience and skill improvement of sensory judgment. It is desirable to provide the machine 5.

[0020]

In order to solve the problems of the conventional bead cutting state monitoring device for electric resistance welded pipes individually and complete the device applicable to the actual manufacturing line, the structure of the device is simple and Is easy to put on and take off, can be used not only for large-diameter ERW pipes, but also for small-diameter sizes, and it is easy to set criteria for determining abnormal bead cutting on the inner surface. It is necessary to overcome such technical issues.

In order to complete such a device, attention is paid to the fact that the vibration of the inner surface mandrel bar caused by the abnormal cutting of the inner surface bead changes depending on the cutting condition during the inner surface bead cutting. It was decided to use an element for detection, for example, a vibration sensor.

FIG. 2 is a diagram showing a schematic arrangement of equipment in a production line (forming-welding-bead cutting process) of an electric resistance welded pipe and a schematic configuration of an inner bead cutting state monitoring device of the present invention. Since the manufactured electric resistance welded pipe 10 is continuously transferred in the advancing direction of the production line, the bite 11 for cutting the inner bead, the inner mandrel bar 7 for mounting the bead, and the holder 6 for supporting these are provided. Has a specific tensile force and has an inherent vibration. Then, when the cutting bite 11 is worn or chipped, or when the bead scraps or the welding flash are clogged, or when the inner surface bead height defect, the inner surface flaw or the micro bead or the hooking flaw of the flash occurs, the inner surface The tensile force exerted on the mandrel bar and the holder changes, and at the same time, the inherent vibration of the mandrel bar changes.

The change in the vibration of the inner surface mandrel bar described above varies depending on the cause of the abnormality and can be roughly classified into three patterns. That is, the first is damage to the inner mandrel bar due to wear and breakage of the cutting tool and clogging of bead scraps and welding flash (hereinafter,
It is a change in vibration caused by "absence of cutting bite, etc.)" and secondly caused by defective cutting bead height and internal surface flaws (hereinafter abbreviated as "improper cutting bead height"). The third is a change in vibration, and the third is a change in vibration caused by a scratching defect of a minute bead or a flash (hereinafter, abbreviated as "hit defect of a minute bead or the like"). Therefore, the criteria for monitoring the inner bead cutting state of the electric resistance welded pipe are set based on the vibration patterns of these inner mandrel bars.
Here, regarding the changes in the vibration of the inner surface mandrel bar caused by each abnormal cutting and the setting procedure of the judgment standard, when the cutting bite defect etc. is targeted, the defective bead height etc. and the minute bead etc. The explanation will be given separately for the case where each of the above scratches is targeted.

1. Vibration due to cutting bit loss, etc., and setting of judgment criteria Representative vibration changes due to cutting bit loss etc. are shown as vibration levels as shown in FIG. 3 and FIG.
A difference in vibration level appears due to the abnormal cutting caused.

FIG. 3 shows an electric resistance welded pipe having an outer diameter of 42.7 mm and a wall thickness of 5.5 mm.
(JIS SGP) is a diagram showing the vibration level (displayed in both amplitudes) detected when a vibration sensor measures the vibration generated when manufacturing (mill speed 45 m / min), and (a) shows a normal bead. The vibration level when cutting is performed,
(B) shows the vibration level when the cutting bite is worn, (c) shows the vibration level when the cutting bite is broken, and (d) shows the vibration level when the bead chips or the welding flash are clogged. On the other hand, Fig. 4 shows the result of measuring the vibration generated when an electric resistance welded pipe (JIS SGP) with an outer diameter of 27.2 mm and a wall thickness of 2.9 mm (mill speed 85 m / min) was measured in the same manner as in Fig. 3. ing.

As is apparent from the measurement results of FIGS. 3 and 4, even when the dimensions of the electric resistance welded pipe are different and the pipe making conditions are also different, the basic vibration of the vibration caused by the abnormal cutting is caused. Level, that is, reference vibration (amplitude of vibration, amplitude change amount, change speed,
Duration, etc.) depends on each cause.

For example, the vibration generated by the wear of the cutting tool (see (b) in the figure) gradually increases in amplitude from the normal state, and after a lapse of a predetermined time, the vibration level during normal bead cutting is 1.5 to 2 Doubles. On the other hand, the vibration caused by the loss of the cutting tool (see (c) in the figure) causes the amplitude to increase instantaneously when the tip of the cutting tool is damaged due to the impact during cutting from the vibration level in the normal state, and the vibration level increases.
It jumps up about 2 to 3 times. In addition, when the inner mandrel bar is damaged due to bead debris clogging (see (d) in the figure)
In the same way as when the cutting bit is missing, the vibration level instantaneously increases three times or more from the normal vibration level.
The inner mandrel bar is damaged.

Therefore, in order to detect a cutting abnormality due to a cutting bit missing or the like, a reference vibration generated due to wear of the cutting bit or damage to the inner surface mandrel bar is set in advance, and a change in vibration generated during cutting is detected. It becomes possible by detecting and continuously determining the cutting situation. As a concrete setting of the reference vibration, the reference value (threshold value) of the vibration level and the duration of the vibration are provided in advance.

A reference vibration (reference value of vibration level and duration of vibration) due to a cutting bit loss or the like is set in advance, and an absolute value determination method and a relative value determination method are used as methods for determining the cutting situation. is there.

FIG. 5 is a diagram for explaining the procedure for setting the reference vibration in the method of determining the cutting situation by the absolute value determination method and the relative value determination method. FIG. 5A shows the case of the absolute value determination method, and FIG. (D) shows the setting procedure in the case of the relative value determination method. However, in FIG. 5, the vibration level is shown as a single amplitude level.

The absolute value determination method is a method of presetting a reference value (a ₁ ) of a predetermined vibration level based on the pipe making line, pipe making size, material, pipe making speed and the like. The vibration level detected during operation is compared, and if it exceeds the reference value and continues for a certain period of time (for example, 5 seconds to 10 seconds or more), it is determined as abnormal cutting.

For example, FIG. 5A shows a change in the vibration level when the inner surface mandrel bar is damaged due to the clogging of the bead scraps or the like. However, the reference value (a ₁ ) of the vibration level is set in advance and set to a predetermined value. It can be understood that the inner mandrel bar can be prevented from being damaged if the judgment is made. When the inner mandrel bar is damaged during the operation, the reference value (a ₁ ) of the vibration level is updated each time, and the determination accuracy can be improved.

In the relative value determination method, the reference value of the vibration level is set for each cause of abnormality as follows, with the vibration level (a ₀ ) in the normal state as a unit.

Reference value of cutting bite wear (a ₂ : FIG. 5
(See (b)) As described above, the change in the vibration level in the case of wear of the cutting tool gradually increases in amplitude from the normal vibration level (a ₀ ). Normally, the rate at which the amplitude increases in this case is 1.2 a ₀ /
10 seconds is a standard, and the reference value is the vibration level (a
_It is set to 1.5 to 2.0 times of ₀ ) and judged by the reference value and the change time of the vibration level.

Reference value of cutting bit loss (a ₃ : FIG. 5
(See (c)) The vibration level (a ₀ ) at the normal time instantly jumps up to about 2 to 3 times, and then a certain constant vibration level is continued. The reference value (a ₃ ) of cutting bit loss is set to 2 to 3 times the normal vibration level (a ₀ ).

Reference value of bead waste and welding flash clogging (a ₄ : see FIG. 5 (d)) Similar to the case of a cutting bite defect, the vibration level (a ₀ ) at the normal time is about 2 to 3 times instantaneously. Bounce up to and continue a certain vibration level. The reference value (a ₄ ) for the clogging of beads and welding flash is set to 3 times the normal vibration level (a ₀ ).

Therefore, in the relative value determination method, the reference value (a _{2 to} a ₄ ) of the vibration level is preset based on the following formula (A), and it is determined whether or not the vibration exceeding the reference value continues for a certain time. judge.

A ₂ , a ₃ , a ₄ = K · a ₀ (A) where K: coefficient (1.5 to 3.0), a ₀ : normal vibration level In the examples described later, cutting It has been confirmed that whether the absolute value judgment method or the relative value judgment method is adopted for judging the state has no problem in the judgment accuracy. However, the reference value of the vibration level in the absolute value judgment method and the relative value judgment method (a
_{Since 1 to} a ₄ ) vary slightly depending on the ERW pipe manufacturing line, it is desirable to set them for each individual equipment.

When the cutting abnormality is detected in this way, the production line can be immediately stopped to prevent the occurrence of a defect in the electric resistance welded pipe due to a cutting bit loss or the like.

2. Vibration due to defective cutting bead height and setting of judgment standard Since the allowable range of the inner bead height of the electric resistance welded pipe differs depending on the application, it is necessary to cut the inner bead to match the predetermined accuracy. If the product is out of the allowable range and cannot be used for other purposes, it becomes a defective product. Also, if there are significant internal surface flaws that occur during bead cutting, the product will be downgraded for quality assurance. Therefore, it is desirable to constantly monitor the cutting bead height defect and the like on the ERW pipe manufacturing line. However, the change in vibration due to defective cutting bead height or the like is different from that due to the above-mentioned cutting bit loss or the like, and therefore cannot be determined based on the above-mentioned reference vibration.

FIG. 6 is a diagram showing a vibration level (displayed by one-sided amplitude) when a cutting bead height defect occurs in comparison with a normal vibration level. In the figure, the outer diameter is 25.4.
The vibration level generated when an ERW pipe (JIS SGP) with a wall thickness of 3.2 mm and a wall thickness of 3.2 mm was manufactured (mill speed 64 m / min) with a specified bead cutting depth of ± 0.2 mm is shown as the vibration level measured by the vibration sensor. In the figure, (a) shows the vibration level under normal conditions (bead cutting depth ± 0.1 mm with respect to the pipe inner surface), and (b) shows the vibration level when the inner bead cutting depth is cut deeper than the specified value. (For example, a bead cutting depth of -0.5 to -0.8 mm) is shown. When the cutting depth of the inner bead does not reach the specified value and becomes too small, the maintenance of the inner bead offline is required.

FIG. 7 is a diagram showing the vibration level (displayed by one-sided amplitude) in the case where the internal surface flaw is generated, in comparison with the vibration level in the normal state. In the figure, an electric resistance welded pipe (JIS SGP) with an outer diameter of 31.8 mm and a wall thickness of 1.6 mm is manufactured (mill speed 85 m / min)
Fig. 6 shows the vibration generated when the
Shows the vibration level in the normal state, and (b) shows the vibration level in the case where the inner surface flaw is generated during the cutting of the inner bead.

From the measurement results of FIGS. 6 and 7, even when the cutting bead height defect or the internal surface flaw is generated,
It can be seen that the vibration level is the same as the vibration level (a ₀ ) in the normal state. However, if attention is paid to the change in the amplitude of each vibration, there is a clear difference between when an abnormality occurs and when it is normal. Here, if the difference between the maximum (single) amplitude and the minimum (single) amplitude of vibration is defined as “amplitude deviation” (b ₀ , b ₁ , b ₂ in the figure), the amplitude deviation increases with the occurrence of abnormality. is doing.

For example, the change in vibration due to defective cutting bead height (see (b) in FIG. 6) has no change in the vibration level, but the amplitude deviation (b ₁ ) is the amplitude deviation (b ₀ when normal). ) Is 1.5 to 2 times larger than On the other hand, the change in the vibration caused by the inner surface flaw (see (b) in Fig. 7) changes greatly when the amplitude deviation (b ₂ ) is normal, as in the case of the defective cutting bead height. 2 to 3 times as large as the amplitude deviation (b ₀ ).

In the production of the electric resistance welded pipe in which a defective cutting bead height or the like was measured by vibration, the production line was not stopped in operation, but the target electric resistance welded pipe was finally obtained. The product will be downgraded because it does not meet the intended use or the internal quality is poor.

Since the above-mentioned characteristics are observed in the change in vibration caused by defective cutting bead height and the like, the reference vibration is set in advance and is set during cutting in the same manner as the above-mentioned cutting bit defect. It is possible to prevent the occurrence by detecting the change of the generated vibration and continuously judging the cutting situation. As a concrete reference vibration setting,
The reference value of the amplitude deviation and the duration of vibration are set in advance. The procedure for setting the reference vibration will be described below with reference to FIGS. 6 and 7.

The amplitude deviation is set for each cause of abnormal cutting with the amplitude deviation (b ₀ ) under normal conditions as a unit.

Reference value of cutting bead height defect (b ₁ :
(See FIG. 6B) As described above, the amplitude deviation due to the defective cutting bead height increases from the amplitude deviation (b ₀ ) at the normal time and increases at the same time as the abnormality occurs, and continues as it is. Therefore, the reference value (b ₁ ) of the amplitude deviation is 1.5 of the amplitude deviation (b ₀ ) under normal conditions.
It is set to 2 times.

Reference value of internal muscle defect (b ₂ : FIG. 7B)
With the occurrence of the internal muscle defect, the amplitude deviation resulting from this increases from the amplitude deviation (b ₀ ) in the normal state and reaches 2-3 times and continues. Therefore, the reference value (b
₂ ) is set to 2 to 3 times the amplitude deviation (b ₀ ) under normal conditions.

As described above, the reference value (b ₁ , b ₂ ) of the amplitude deviation in the determination of the cutting bead height defect or the like is set based on the following equation (B), and the vibration is constant beyond this reference value. The occurrence of abnormality is determined by whether or not the time has continued.

B ₁ , b ₂ = K · b ₀ (B) Here, K: coefficient (1.5 to 3.0), b ₀ : vibration deviation in normal state The above-mentioned reference value of vibration deviation (b ₁ , B ₂ ) changes slightly depending on the production line of the electric resistance welded pipe, and it is desirable to set them for each equipment in order to improve the monitoring accuracy.

In operation, when a defective cutting bead height or the like is detected, the production line is immediately stopped and the cutting bead height is adjusted. Can be prevented.

3. Vibration caused by catching flaws such as minute beads and setting of judgment standard Minute bead chips and welding flash fall on the inner surface of the pipe due to melting of the edge part of the electric resistance welded pipe and pressure bonding. Normally these are removed without scratching the inner surface,
Some of them may adhere to the inner surface mandrel bar, causing hooking flaws on the inner surface of the pipe. If the hooking flaw is small, no problem in quality assurance will occur, but if the hooking flaw becomes significant and the hooking flaw becomes remarkable, the product will be downgraded for quality assurance. Therefore, as in the case of defective cutting bead height, it is desirable to constantly monitor hooking flaws such as minute beads on the ERW pipe manufacturing line.

FIG. 8 is a diagram showing the transition of the vibration level (displayed by one-sided amplitude) when a catch flaw such as a minute bead occurs. In the figure, among the measured vibration generated when an electric resistance welded pipe (JIS SGP) with an outer diameter of 25.4 mm and a wall thickness of 3.2 mm (mill speed 64 m / min) was measured, scratches such as micro beads were detected. Typical examples of the vibrations caused by are shown as vibration A and vibration B. In both cases, it was determined that the vibration level increased with the passage of time and a quality defect occurred.

As is clear from FIG. 8, in order to prevent a defect caused by a catch flaw such as a minute bead, it is necessary to pay attention to the gradient of the changing vibration level. That is, in the vibration A, the inconvenience A is brought about by the rapid increase in the inclination of the vibration level. Therefore, by setting a reference inclination of the vibration level as the reference vibration in advance, measuring the inclination of the vibration level that occurs during cutting, and making continuous determinations, it is possible to prevent the occurrence of defects. However, at a vibration level caused by a catching flaw such as a minute bead, even if the vibration level has a small inclination and is constant like the vibration B, the problem B is caused by continuing it for a long time. There are cases. This can be prevented by setting the reference value (c ₁ ) of the vibration level in advance.

Since the above-mentioned characteristics are seen in the vibration level caused by the scratches such as micro beads, the standard inclination of the vibration level and the standard of the vibration level are based on the normal vibration level (c ₀ ). The values are set as follows.

From various examination results, it is possible to prevent the occurrence of troubles by setting a concrete reference gradient Δg of the vibration level based on the following equation (C).

Δg = K · c ₀ / T (C) where K: coefficient (1.5 to 3.0), c ₀ : vibration level at normal time T: elapsed time (10 seconds) Therefore, continuous measurement was performed. When the inclination of the vibration level exceeds the reference inclination Δg, it is predicted that a defect due to a catch flaw such as a minute bead will occur.

On the other hand, even if the inclination of the vibration level is equal to or less than the reference inclination Δg, in order to prevent the occurrence of troubles due to the continuous operation for a long time, the reference value (c ₁ ) of the vibration level is used.
To set. That is, the reference value (c ₁ ) of the vibration level is set to three times the normal vibration level (c ₀ ), and when a vibration level exceeding this is generated, the occurrence of a defect is predicted. In this case, the vibration level reference value (c ₁ )
It is not necessary to determine whether or not to continue for a certain period of time after exceeding the reference value, and it is immediately determined that a failure occurs when the reference value (c ₁ ) is exceeded.

Since the reference gradient Δg of the vibration level slightly changes depending on the production line of the electric resistance welded pipe, it is desirable to set it for each equipment in order to improve the monitoring accuracy. Further, when a defect caused by a catching flaw such as a minute bead is determined during operation, the production line can be immediately stopped to prevent the generation of a downgrade product.

The procedure for setting the reference vibration is as follows: when the cutting bite is to be broken, when the cutting bead height is to be defective, and when a defect due to a catching flaw such as a minute bead is to be determined. Although different, in the production line of the electric resistance welded pipe, the cutting state determination means may be set individually or may be set redundantly without any problem.

[0062]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing an example of the construction of an internal cutting tool cutting abnormality monitoring apparatus according to the present invention.

In the internal cutting tool cutting abnormality monitoring apparatus of the present invention, as shown in FIGS. 1 and 2, a vibration sensor 1 which is an element for detecting the vibration of the internal mandrel bar 7 is attached to the internal mandrel holder 6. When the vibration sensor 1 is attached, it is desirable to attach it to a place where the vibration of the inner surface mandrel bar 7 can be detected most easily. However, in order to replace the inner surface mandrel bar 7 for each pipe manufacturing size, the inner surface mandrel holding portion 6 must be attached. did.

There are two types of vibration sensor 1 which are a magnet type and a fixed type. In this embodiment, a magnet type vibration sensor is used in which the vibration sensor is attached by magnetically attaching and detaching. This is because when the inner surface mandrel holder 6 is replaced, it can be easily attached and detached, and the vibration detection of the inner surface mandrel bar 7 has the same performance as the fixed type. Of course, even if a fixed vibration sensor is used, there is no problem in the cutting abnormality monitoring performance.

The vibration signal output from the vibration sensor 1 is taken into the cutting state determination device 4 via the amplifier 2. Here, the cutting state is determined by comparison with a preset reference vibration.

In setting the reference vibration, the reference value (a _{1 to} a ₄ ) of the vibration level is set in the judgment of the cutting bit missing or the like.
Amplitude deviation reference values (b ₁ , b ₂ ) are used to determine cutting bead height defects and internal muscle defects, and vibration level reference slopes (Δg) and vibration level reference values are used to determine hooking defects such as small beads. (C ₁ ) must be set, but even if each is set individually based on the cutting abnormality to be judged,
Alternatively, it is confirmed that there is no problem in the determination accuracy even if the settings are duplicated. Vibration level reference value (a _{1 to} a ₄ )
Alternatively, when the vibration duration exceeding the reference value (b ₁ , b ₂ ) of the amplitude deviation exceeds 5 to 10 seconds, it is determined that a cutting abnormality is determined to occur.

The amplifier 2 is also connected to a recorder (memory monitor) 3. This is because it is desirable to reduce abnormal cutting by allowing the operator to constantly monitor and recognize by visually inputting the vibration signal to the recorder.

When the cutting state judging device 4 judges a cutting abnormality, the alarm device 5 instantly gives a warning of the inner bead cutting abnormality. This alarm shuts down the production line,
Appropriate means such as exchanging the cutting tool and the inner surface mandrel bar can be taken to prevent the occurrence of defective cutting of the inner beads and the generation of defective products or downgraded products due to defective cutting of the inner beads.

[0069]

According to the apparatus of the present invention, the cutting state of the inner bead can be detected reliably and quickly. Therefore, even if the cutting position of the inner bead and the cutting position of the electric resistance welded pipe are separated, It is possible to prevent the occurrence of defective cutting, and to prevent the yield of ERW pipes from decreasing, the number of downgraded products due to quality deterioration, and the deterioration of the operating rate of the manufacturing line.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of the configuration of an internal cutting tool cutting abnormality monitoring device of the present invention.

FIG. 2 is a diagram showing a schematic arrangement of equipment in a production line (forming-welding-bead cutting process) of an electric resistance welded pipe and a schematic configuration of an inner bead cutting state monitoring device of the present invention.

[Fig. 3] Fig. 3 is a diagram showing a vibration level generated when an electric resistance welded pipe (JIS SGP) having an outer diameter of 42.7 mm and a wall thickness of 5.5 mm was manufactured (mill speed: 45 m / min), and (a) shows a normal bead. If the cutting tool is worn,
(C) shows detection signals of the respective vibrations when the cutting tool is missing, and (d) shows the respective vibration detection signals when the inner surface mandrel bar is damaged.

FIG. 4 is a diagram showing vibration levels generated when an electric resistance welded pipe (JIS SGP) having an outer diameter of 27.2 mm and a wall thickness of 2.9 mm is manufactured (mill speed 85 m / min) ((a) to (d)). Is the same as in FIG. 3).

FIG. 5 is a diagram illustrating a procedure for setting a reference value of a reference vibration in a method of determining a cutting situation by an absolute value determination method and a relative value determination method. FIG. b) to (d) show a setting procedure in the case of the relative value determination method.

[Fig. 6] Fig. 6 is a diagram showing a vibration level generated when an electric resistance welded pipe (JIS SGP) having an outer diameter of 25.4 mm and a wall thickness of 3.2 mm is manufactured (mill speed 64 m / min). Vibration level,
(B) shows the vibration level when the inner bead cutting depth is excessively deeper than the specified value.

FIG. 7 is a diagram showing a vibration level generated when an electric resistance welded pipe (JIS SGP) having an outer diameter of 31.8 mm and a wall thickness of 1.6 mm was manufactured (mill speed 85 m / min). ((A)-(b) is the same as FIG. 6).

FIG. 8 is a diagram showing a transition of a vibration level (displayed by one-sided amplitude) when a catch flaw such as a minute bead occurs.

[Explanation of symbols]

1 ... Vibration meter, 2 ... Amplifier, 3 ... Recorder, 4 ... Cutting condition determination device, 5 ... Alarm device, 6 ... Inner surface mandrel holder, 7 ... Inner surface mandrel bar, 8 ... Forming roll stand, 9 ... Open pipe, 10 ... ERW pipe 11… Cutting tool, 12… Work coil, 13… Squeeze roll

Claims (4)

[Claims] 1. An inner surface mandrel bar equipped with a cutting tool for cutting an inner surface bead of an electric resistance welded pipe, an element for detecting the vibration of the inner surface mandrel bar, and an output of vibration from the element for detecting the vibration, which is set as a reference. An electric resistance welded pipe inner surface bead cutting state monitoring device comprising means for comparing a vibration with a cutting state to determine a cutting state. 2. An inner surface mandrel bar equipped with a cutting tool for cutting an inner surface bead of an electric resistance welded pipe, an element for detecting the vibration of the inner surface mandrel bar, and an output of the vibration from the element for detecting the vibration are set in advance. And a means for determining whether or not the reference value of the vibration level or the reference value of the vibration level determined by the following formula (A) is continued for a certain period of time. apparatus. Vibration level reference value = K · a ₀ (A) where K: coefficient, a ₀ : normal vibration level 3. An inner surface mandrel bar equipped with a cutting tool for cutting an inner surface bead of an electric resistance welded pipe, an element for detecting the vibration of the inner surface mandrel bar, and an output of the vibration from the element for detecting the vibration is as follows. And a means for determining whether or not the amplitude deviation reference value defined by the equation (B) has been exceeded for a certain period of time, and a bead cutting state monitoring device for an electric resistance welded pipe inner surface. Amplitude deviation reference value = K · b ₀ (B) where K: coefficient, b ₀ : normal amplitude deviation 4. An inner surface mandrel bar equipped with a cutting tool for cutting an inner surface bead of an electric resistance welded pipe, an element for detecting the vibration of the inner surface mandrel bar, and an output of the vibration from the element for detecting the vibration is as follows. An apparatus for monitoring a bead cutting state on an inner surface of an electric resistance welded pipe, comprising: a means for determining whether or not a reference inclination of a vibration level defined by the formula C) or a preset reference value of the vibration level is exceeded. Reference slope of vibration level = K · c ₀ / T (C) where K: coefficient, c ₀ : normal vibration level,
T: elapsed time