JPS5920673Y2 - Hoop material joint detection device between pipe mill runs - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a hoop material seam detection device in pipe mill running in a steel pipe factory.

In general, pipe mill lines that continuously manufacture forge welded or ERW steel pipes at high speed are used for hoop material (3
00 to 1000 m length) is sent out while welding each turn.

The cutter that finishes the hoop material to a predetermined width during this run is retracted from the hoop material just before it approaches the welding point to protect its cutting edge, and quickly returned to its original position after passing.

The uncut parts of the hoop material (before and after the weld seam) due to the withdrawal of the cutter are cut and discarded after forming the steel pipe, and making the dimensions as short as possible is an important factor in improving product yield.

A through-type eddy current flaw detection device in which a hoop material passes through a detector is conventionally used to detect the joint position in a non-contact manner during high-speed running.

This uses one high-frequency excitation coil and two pickup coils for the self-comparison method, and a DC magnetic field coil on the outside.The two pickup coils are placed as close to each other as possible. When one approaches a healthy part of the object and the other approaches a defective part such as a scratch or crack, the impedance of each changes.

This impedance difference is detected as a flaw signal by not outputting gradual changes in the material or dimensions along the length of the test material, but only local rapid changes such as flaws or cracks are detected.

Therefore, when using this device to detect the seam of hoop material, if the welded part is welded continuously and almost uniformly along the width direction of the hoop material, the detection signal will be weak and cannot be detected in practice. There are some drawbacks that cannot be overcome.

There is currently a strong demand in the steel pipe industry for a device that can accurately detect the hoop material seam position with high sensitivity regardless of the welding condition.

In view of the above-mentioned current situation, this idea was developed to solve the drawbacks of the conventional eddy current flaw detection method for detecting hoop material joints in pipe mill lines that use hoop materials such as magnetic steel strips, regardless of the condition of the welded part. The object of the present invention is to provide a device that can detect the joint position of the groove with good precision and high sensitivity, has a simple structure, is robust, and is suitable for high-speed lines.

That is, two coils are arranged close to the magnetic hoop material between the pipe mill runs and wound around the hoop material orthogonally to the running direction thereof, arranged in the order of secondary and primary along the running direction, A detection unit applies a high frequency voltage to the primary coil, and a DC excitation coil is wound concentrically around the outer periphery of the two coils, and the hoop material is magnetized near its maximum magnetic permeability by this DC magnetic field. , two circuits are installed to separate the modulated high-frequency signal induced in the secondary coil by the joint of the hoop material into upper and 1000 half-wave signals and detect them individually, and further synthesize the synchronous parts of these two detected signals. The present invention relates to a hoop material seam detection device between pipe mill runs, which comprises a signal circuit for detecting a hoop material seam and a signal processing section configured to output the synthesized signal as a hoop material seam signal.

An embodiment of this invention will be explained in detail below with reference to the drawings.

FIG. 1 is an external view of the detection section of the hoop material detection device.

Reference numeral 1 denotes a detection unit outer case, which is supported directly or via a spring on a base (not shown).

Reference numeral 2 denotes a hoop material through-hole, and 3 and 3' denote coil protection plates, which are divided into three upper and two lower parts, and are provided alternately in the upper and lower portions as shown in the figure, in order to prevent thin current loss.

The material used is a non-magnetic material such as stainless steel.

Reference numeral 4 denotes a DC power supply connector 5, which is a high-frequency line connector and connects the power supply, signal processing device, and detection unit with cords 4A and 5A, respectively.

The chain double-dashed line 6 indicates a pipe hoop material such as a steel band, which runs in the direction of arrow A at high speed (approximately 1.5 m/sec, although it varies depending on the pipe diameter, etc.).

FIG. 2 is a central sectional view (III) of the detection section, and the outer box 1 is omitted.

6 is a hoop material, and 7 is its welded seam.

Two coils 8 and 9 are wound around the hoop material 6 in contact with the protection plates 3 and 3', one of which is a high-frequency excitation coil, and the other coil 9 is a seam detection coil. The winding ratio of both secondary coils is 1:1,
The arrangement is as shown in FIG. 2 with respect to the running direction A of the hoop material 6.

Reference numeral 10 denotes a DC excitation coil concentrically wound outside the two high-frequency coils.

This configuration is a high frequency transformer with a hoop material 6 as an iron core, 8 as a primary winding, and 9 as a secondary winding.

The coil 10 is for direct current excitation in order to use the hoop material 6 serving as the iron core near the maximum magnetic permeability (μm) of the material.

In order to explain the principle, Figure 3 shows the B-H curve of the magnetic core material, with the horizontal axis showing the magnetizing force H and the vertical axis showing the magnetic flux density B.
is taken.

If we draw a tangent that passes through the 0 point to the rising hysteresis curve OC, the magnetic permeability B/H will be maximum at this contact point, so in this vicinity, the secondary voltage e2>the primary voltage e1.

As a result, the primary voltage e1 of the coil 8 efficiently becomes the secondary voltage e2 and is output to the coil 9.

Next, the configuration and operation of the seam detection device including the detection section will be explained with reference to the block diagram of FIG. 4 and the waveform diagram of FIG. 5.

In these figures, the description of the same symbols as those in FIGS. 1 to 3 will be omitted.

5 is a modulated wave W1 that includes a change value e2' in the output voltage e2 of the detection coil 9 when the hoop material joint 7 passes.

The modulated wave W1 is transmitted through 11 amplifiers, 12 voltage regulators, and 1
The signal voltage is set within a predetermined signal voltage range using attenuator 3, and is input to two circuits 14 and 15 at branch point 13.

The settled modulated wave input to the circuit 14 is directly subjected to half-wave rectification by the half-wave rectifier 16 to form the waveform Wu shown in the left diagram of FIG.

For the settled modulated wave input to the circuit 15, the polarity is inverted by the polarity reversing circuit 17, and then half-wave rectified by the half-wave rectifier 16', resulting in the waveform WDI shown in the right diagram of Figure 5. .

Therefore, the upper seam signal U of Wl and the lower seam signal D are separated.

Next, when the signals are passed through low-pass filters 18 and 18', high frequency components are removed, resulting in signal waves Wu2 and WD2 that include the above-mentioned u, D and changes T such as uneven thickness of the hoop material.

One of the features of the device of this invention is that it screens out the joint signal UD and other signals T.

By passing Wu2°Wl,2 through an integrator 19.19', gradual changes are output as they are, but sudden changes (uJ) are cut out and Wu3. W
As shown in D3, the waveform is changed and the differential amplifier 20, 20
' is input.

On the other hand, the signals that do not pass through the integrators 19 and 19' are Wu2, W
Since n2 is input as is to the differential amplifiers 20 and 20', the outputs of the differential amplifiers 20 and 21' are U,]), and in other words, the signal waves Wu4 and WD4 (
Figure 5 ■).

When this is input to the Schmidts 1 to trigger circuits 21 and 21', the pulse signals Pu and PD shown in FIG.

When this is manually combined with the AND circuit 22, a pulse Ps is output, as shown in FIG.

This becomes a seam signal and is output to the cutter retracting device drive relay R and also to the indicator light.

We explained that this device is designed to eliminate detection signals for relatively gradual changes such as changes in hoop material thickness and material. Detection signals for scratches can also be erased.

The reason for this will be explained below. The above-mentioned flaw detection signal has a similar form to the seam detection signal shown in FIG. Therefore, a sufficiently large signal is returned compared to the sound part of the hoop material 6, whereas the signal from the flawed part of the hoop material 6 is small because it is locally small.

Therefore, by focusing on the difference in the magnitude of the two signals, this device is designed to evaluate only the seam signal by selecting the degree of amplification in the amplifier 11 to such an extent that the scratch signal is not noticeable.

Other signals include, for example, signals generated by mechanical vibrations when the hoop material 6 travels.
This vibration waveform is different from the one shown in Figure 5 ■, and the DC
The entire signal wave becomes undulating due to the influence of the magnetic field.

Therefore, the signals based on mechanical vibrations are clearly separated and eliminated by the above-described signal processing due to the difference in waveform.

The above is an explanation of the structure and operation of this invention.The major feature of this invention is that, unlike the conventional eddy current flaw detection method, seam detection is performed using a high frequency transformer method in which the test material is an iron core.

Therefore, instead of placing two high-frequency coils close together and detecting the difference in impedance between them as in the eddy current testing method, the seam can be accurately detected at the position of a single secondary coil, and changes in magnetic flux density can be detected during welding. Regardless of the quality of the finish, it can be detected as a dango-shaped modulated wave as shown in Figure 5 (2).

By signal processing only this bump-like output, all detection signals other than the thickness of the hoop material, scratches, and other welding can be erased, so that the position can be detected accurately and with high precision.

The detection unit shown in Fig. 1 is supported on a support base via a buffer material such as a spring, and by attaching a roller or the like to the entrance and exit of the hoop material, the vertical vibration caused by the running of the hoop material is absorbed by the spring. It is possible to absorb this and maintain a constant distance from the detection coil.

Since this device is configured as described above, the conventional eddy current flaw detection method used to detect joints in hoop materials between runs of a pipe mill has a large influence on the detection signal depending on the quality of the welding, and is often unable to detect the joints. By solving the disadvantages of the hoop material, incorporating a high frequency transformer system that has never been tried before, and using a signal processing means that eliminates all detection signals other than the joint, the structure is simple and robust, and the joint position of the hoop material can be precisely determined. By detecting scales with good accuracy, we have been able to provide an apparatus that is highly effective in improving the yield of steel pipe manufacturing.

[Brief explanation of the drawing]

Fig. 1 is an external perspective view of the detection part of the hoop material seam detection device according to the embodiment of this invention, Fig. 2 is an explanatory diagram of its internal structure, and Fig. 3
The figure is an explanatory diagram of DC excitation of the hoop material of this invention, FIG. 4 is a block diagram of the circuit configuration of an embodiment of the apparatus of this invention, and FIG. 5 is a waveform diagram of each of the above parts. 1...Detection unit outer box, 2...Detection unit through hole, 3, 3'...Upper and lower coil protection plates (non-magnetic member), 4.5... ...Connector, 4A, 5A...
... Connection cord, 6 ... Hoop material, 7 ...
... Hoop material joint (liquid contact part), 8 ... High frequency secondary coil, 9 ... Detection coil (secondary coil), 10 ... DC excitation coil, A...
Hoop material running direction, ±H... Magnetizing force, ±B...
...Magnetic flux density, μm ... Maximum permeability, +H
]... Magnetizing force due to DC excitation, 10B1...
...Magnetic flux density at maximum permeability, el...Primary high frequency voltage, e2...Secondary high frequency voltage, e2'
... Seam detection voltage (modulated wave), R...
Output terminal to relay circuit, L...output terminal to indicator light, Wl...modulation waveform, U...one side of joint signal, D...・The lower side of the above, Wul
. WDl...Half-wave modulated wave (upper side, lower side), Wu2
．． WD2... Waveform after passing through the low pass filter,
T...Detection signals other than seams (thickness changes, etc.)
, Wu3. WD3...Integrator output signal, Wu4
, WD4... Signal waveform only at the seam, Pu.
...Pulse signal at the upper half-wave joint, PD...
...Pulse signal at the seam of the lower half wave, Ps...
・Joint signal of AND circuit output, tl, t2...
・Rise and fall points of Ps.

Claims (1)

[Scope of utility model registration request] 1. Two coils are arranged in the order of secondary and primary along the running direction of the pipe mill, and two coils are arranged around the hoop material in the vicinity of the magnetic hoop material between the pipe mill runs and perpendicular to the running direction of the hoop material. A detection unit that applies a high-frequency voltage to a primary coil and winds a DC excitation coil concentrically around the outer periphery of the two coils, and magnetizes the hoop material near its maximum magnetic permeability by the DC magnetic field, and a hoop. Two circuits are provided to separate the modulated high-frequency signal induced in the secondary coil by the seams of the material into half-wave signals, half-wave signals, and half-wave signals, and to synthesize the synchronous components of both detected signals. A hoop material seam detection device between pipe mill runs, comprising a circuit and a signal processing section configured to output the synthesized signal as a hoop material seam signal. 2. After converting the modulated high-frequency signal separated into upper and lower half-wave signals into a low-frequency signal, the difference between this signal and the integrated signal is amplified to extract only the hoop material seam signal. A hoop material seam detection device between pipe mill runs as claimed in claim 1.