JPH05248846A - Method and apparatus for detecting defective cutting of bead at inner surface of pipe - Google Patents

Abstract

PURPOSE:To improve measuring accuracy by providing an apparatus, which judges the presence of a cutting remnant when the number of the reflected waves from the inner surface of a pipe is 2 or more. CONSTITUTION:The ultrasonic wave from an ultrasonic wave probe 5 is sent into a pipe body 1 by the application of the pulse voltage of a transmitting and receiving circuit 6. When a burr-shaped cutting remnant 1a is present, present, the reflected wave from the cutting remnant 1a is received in addition to the reflected waves from the outer surface and the inner surface of the pipe. The reflected wave, which is received with the probe 5, is converted into the electric signal in the circuit 6. The signal is sent into a thickness measuring circuit 8 and a wave-number counting circuit 9, respectively. In the thickness measuring circuit 8, the thickness of the pipe body is obtained based on the reflected waves from the outer surface 1A and the inner surface 1B of the pipe body 1. Meanwhile, in the wave-number counting circuit 9, only the reflected wave from the inner surface of the pipe body 1 is received, and the number of the detected pulses is counted. When the pulse is 1, it is judged that no burr-shaped cutting remnant is absent. When the pulses are 2 or more, the presence is judged. The signal is sent into a protruding-amount operating circuit 10, and the protruding amount (c) is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a cutting failure of an inner bead of a welded steel pipe by using ultrasonic waves, and more particularly to a method and an apparatus for detecting even small pieces of cutting residue.

[0002]

2. Description of the Related Art Generally, in an electric resistance welded pipe, a steel strip is bent into a cylindrical shape through a group of forming rolls so that both side edge portions face each other, and a high frequency current is passed through the end surface to heat the both side edge portions. While being passed between squeeze rolls, both edges are abutted and welded, the beads formed at the welds are cut and removed on the inner and outer surfaces, shaped by a shaping machine, and then cut to a prescribed length. .. In the electric resistance welded pipe manufactured in this way, in addition to quality control of the welded part (butting part), in order to meet the quality demand for the cylinder tube body, which has been in increasing demand in recent years, the inner bead The cutting condition is also managed.

Conventionally, the inner surface bead of electric resistance welded pipes was mainly controlled by detecting from the inner surface side of the pipe, but it was difficult to detect it when the pipe diameter was small. In Japanese Patent Laid-Open No. 61-273273, ultrasonic waves are transmitted from the outer side of the electric resistance welded pipe and reflected waves from the outer side and the inner side of the welded portion are received in order to accurately detect the inner bead shape from the outer side of the pipe. Then, a device for detecting the protrusion amount of the inner bead from the time difference is disclosed. Specifically, the inner bead detection device first scans the ultrasonic probe at a predetermined scanning pitch interval in a direction orthogonal to the tube axis, and the outer surface reflected wave and the inner surface reflected wave of the tube body at each scanning pitch. After obtaining the time difference of the detection timing; t ₁ ... t _n , this time difference t _n
Is assumed constant value the time difference, and therefore the thickness of Without projecting on the inner surface beats tube component takes (t _h), if there is a stepped portion, only the reflection distance is increased the thickness of the step portion Paying attention to the fact that the time difference t _n becomes large because the inner surface reflected wave returns with a delay, the step portion occurrence position of the inner surface bead is specified, and the difference Δt (t _n −t _h ) from the above-mentioned t _h is determined. Then, from the relationship with the ultrasonic longitudinal wave propagation velocity of the electric resistance welded pipe material; C ₀ , the protrusion amount of the inner bead; h is obtained by the following formula (1). h = Co · Δt / 2 −−−−−−−−−− (1) Also, in Japanese Patent Laid-Open No. 54-21372, the thickness of the pipe is obtained by receiving the external reflection echo and the internal reflection echo of the pipe body. A detection device for measuring is disclosed.

[0004]

In the case of the inner surface bead detection device described in the above two publications, as shown in FIG. 5A, the effective beam on the inner surface 1B of the tube of the focus type probe 20 is detected. Assuming that the burr-shaped cutting residue 1a narrower than the width d _s remains, the reflected wave from the pipe inner surface 1B returns with a slight delay from the burr-shaped cutting residue 1a. As shown, the burr-like cutting residue 1a
There are two reflections, a reflected wave B ₁ from the other portion and a reflected wave B _b from the burr-like stepped portion 1a. However, in the case of the inner bead detection device, the step portion is detected from the time difference t _n between the reflected wave S ₁ from the outer tube surface 1A and the first reflected wave B ₁ from the inner tube surface 1B, and the thickness of the bead portion is detected. Since the secondary reflected wave B _b from the pipe inner surface 1B is not detected, the burr-like cutting residue 1a cannot be detected. That is, the effective beam width d _s of the focus type probe 20.
Therefore, the measurement limit of defective cutting is determined, and it becomes impossible to measure the minimum width burr-like cutting residue.

Therefore, it is possible to reduce the effective beam width d _s in order to improve the measurement accuracy of cutting defects, but the measurement accuracy is improved in a limited range, but the water distance (probe and pipe It becomes less sensitive to changes in the distance to the outer surface), and even fine surface flaws on the outer surface are detected.

Therefore, the main object of the present invention is to provide a method for detecting defective cutting of a bead on the inner surface of a pipe, which enables confirmation of the presence of even a very small width of cutting residue left on the inner surface of the pipe, thereby improving the measurement accuracy. To do.

[0007]

[Means for Solving the Problems] The problem is to detect a defective cutting of an inner bead after cutting a butt welded portion of a pipe, and then to detect a defective bead of an inner bead with an ultrasonic probe facing the bead line. In the method of detecting the cutting failure of the bead on the inner surface of the pipe by transmitting the ultrasonic wave while scanning in the direction orthogonal to, and receiving the reflected wave, paying attention to the number of reflected waves from the inner surface side of the pipe. This can be solved by determining that there is no cutting left when the number of reflected waves from the pipe inner surface side is 1, and that there is cutting left when the number of reflected waves from the pipe inner surface side is 2 or more. Further, when the number of reflected waves from the inner surface of the pipe is 2 or more, the protrusion amount of the uncut portion can be obtained from the time difference between the reception timings of the earliest reflected wave and the last reflected wave. As the ultrasonic probe, one having a high frequency, a focused beam and a high damping property is preferably used.

On the other hand, the apparatus is arranged so as to be movable in the direction orthogonal to the bead line from the outer surface side of the pipe so as to face the butt-welded portion, and to transmit an ultrasonic wave toward the pipe and to reflect it. An ultrasonic probe that receives a wave and a wave number counting circuit that counts the number of reflected waves limited to the reflected waves from the inner surface of the tube are provided. Further, when the wave number is 2 or more in the wave number counting circuit, the projecting amount can be obtained by an arithmetic circuit which obtains the projecting amount of the uncut portion from the time difference between the reception timings of the earliest reflected wave and the last reflected wave.

[0009]

The inner surface bead failure is detected by the conventional ultrasonic probe based on the time difference between the detection timings of the reflected waves reflected from each of the inner and outer surfaces of the tube. Was to find the wall thickness as.
On the other hand, the present invention basically focuses on the reflected wave from the inner surface side of the pipe to detect the cutting residue of the inner surface bead.

When a burr-like cutting residue having a minimum width within the effective beam width remains on the inner surface of the pipe, the reflected wave from the inner surface of the pipe is from the inner surface of the base material of the pipe excluding the burr-like cutting residue. Since two reflected waves, a reflected wave and a reflected wave from the burr-like cutting residue, are received, the number of reflected waves from the inner surface side of the pipe is focused and this number of reflected waves is detected. This makes it possible to detect the presence or absence of a burr-like cutting defect. Further, based on the time difference (t) between the reception timings of the two reflected waves from the inner surface of the pipe, h
The amount of protrusion of this cutting defect can be obtained by the arithmetic expression of = Co · t / 2. Since the two reflected waves from the inner surface of the tube are continuous waves that are close to each other, use of a high-frequency wave, a focused beam, and a high damping property increases the decomposition performance and improves the accuracy.

[0011]

The present invention will be described in detail below with reference to the drawings. In the present invention, the steel strip is bent into a cylindrical shape so that both side edge portions thereof face each other through a forming roll group, and a high frequency current is passed through the end face to pass between the squeeze rolls while heating the both side edge portions. In the process of manufacturing electric resistance welded pipes that are manufactured by abutting the edges on both sides, removing the beads formed on the welds on the inner and outer surfaces, shaping them with a shaping machine, and then cutting them to a specified length. The cutting defect detection device for an inner bead according to the present invention is used at an appropriate stage after cutting the inner and outer faces of the bead. In detecting the cutting failure of the inner bead, as shown in FIG. 1, the ultrasonic probe 5 is attached in a direction perpendicular to the outer surface 1A of the tubular body 1. The ultrasonic probe 5 is a movable base along a guide rail 3 concentrically arranged with the tube body 1 in a state where water is interposed as an ultrasonic wave propagation medium between the ultrasonic probe 5 and the tube body 1. The servo motor 4 is mounted on the table 2 and is driven by a command from the probe moving circuit 7 in a direction orthogonal to the bead line while keeping a certain distance from the bead portion 1C, and the scanning movement of the bead to the left and right is controlled.

The ultrasonic waves emitted from the ultrasonic probe 5 are transmitted toward the tubular body 1 by exciting the oscillator in the ultrasonic probe 5 by applying a pulse voltage from the transmitting / receiving circuit 6. To be done. The ultrasonic wave transmitted by the ultrasonic probe 5 is reflected wave S ₁ from the outer surface 1A of the tubular body 1 if there is no burr-like cutting residue on the inner surface side of the bead portion 1C.
When the reflected wave B ₁ from the tube inner surface 1B is received and the burr-shaped cutting residue 1a is present, as shown in FIG. 2, in addition to the reflected waves S ₁ and B ₁ , burr-shaped cutting residue 1a. The reflected wave B _b from 1a is received.

The reflected waves S ₁ , B ₁ , and B _b received by the ultrasonic probe 5 are converted into electric signals by the transmission / reception circuit 6, and the wall thickness measuring circuit 8 and the wave number counting circuit 9 are converted.
Sent to each. In detecting the reflected wave, a certain threshold level R is set so that even minute irregularities on the inner and outer surfaces 1A and 1B of the tube are not detected, and those below this echo value are ignored.

In the wall thickness measuring circuit 8, as shown in the middle part of FIG.
The capturing range is limited to the pulse echoes of the reflected waves S ₁ and B ₁ from the outer surface 1A and the inner surface 1B, and the detection pulse is received at the corresponding position at the same time as the signal reception of the pulse echoes of the reflected waves S ₁ and B _1. Outputs e ₁ and e ₂ . Then, if the time difference t _n between the detection pulses e ₁ and e ₂ is obtained, the wall thickness (T) of the tubular body can be obtained by the following equation (2). Thickness of the tube _{(T) = Co · t n} / 2 ------- (2) where, C _0; an ultrasonic longitudinal wave propagation velocity of the tube. The calculation result of the wall thickness value T is sent to, for example, a storage device, a recording device, a display device or the like (not shown). By the wall thickness measurement, it is possible to effectively detect the excessive shaving of the entire inner bead shown in FIG. 3 and the insufficient shaving of the entire inner bead shown in FIG. 4, which are not detected by the burr-like cutting residue detection system described later. ..

On the other hand, in the wave number counting circuit 9, a wave number counting gate is provided to limit the reflected waves B ₁ and B _b from the inner surface 1B side of the tubular body 1 to the pulse echoes thereof, and the reflected wave B At the same time when the pulse echo signals of ₁ and B _b are received, detection pulses e ₂ and e
While outputting ₃ , the number of this detection pulse is counted. Here, if the detection pulse is 1, it is determined that there is no burr-like cutting residue, and if the detection pulse is 2 or more, it is determined that there is a burr-like cutting residue and the presence or absence thereof. Then, as shown in the figure, when the detection pulse is 2, the time difference t _s between the detection pulses e ₂ and e ₃ is obtained,
This signal is sent to the protrusion amount calculation circuit 10 and the protrusion amount (h) is obtained by the following equation (3). When the number of detection pulses is 3 or more, the time difference t _s is calculated with the earliest detection pulse and the last detection pulse. Protrusion amount _{(h) = Co · t s} / 2 ------- (2) the burr-like cutting remainder of the presence or absence of the determination result and calculation result of the amount of projection h, like the meat thickness value T , A storage device, a recording device, a display device, etc. Even if a part is over-cut as shown in FIG. 5B, the echo from the bottom of the over-cut recess 1b becomes B ₁ and the echo from the same surface as the inner surface 1B becomes B _b. , Is processed in the same manner and judged to be abnormal.

[Example] A cutting defect detection device according to the present invention was installed on a production line for medium-sized electric resistance welded pipes, and a defective cutting portion of an inner bead after bead cutting was detected. The detection conditions are shown in Table 1.

[0017]

[Table 1]

As a result of the test, the conventional detection performance of the inner surface bead cutting defect was limited to the detection of the uncut portion having the width of 5 mm and the protrusion amount of 0.5 mm, whereas according to the present invention, the width of 2 mm and the protrusion. It is possible to detect up to a cutting residue of 0.3 mm and greatly improve the measurement accuracy.

[0019]

As described above in detail, according to the present invention, it is possible to detect even a minute burr-like cutting residue which could not be measured conventionally, by greatly improving the cutting residue detection capability of the inner surface bead. As a result, it becomes possible to stably supply high-quality products, especially when supplying to applications where internal precision is required.

[Brief description of drawings]

FIG. 1 is a block diagram of an internal bead cutting failure detection device according to the present invention.

FIG. 2 is a time chart diagram of processing in each circuit in the apparatus.

FIG. 3 is a diagram showing an example of defective cutting of an inner bead.

FIG. 4 is a diagram showing an example of defective cutting of an inner bead.

FIG. 5 is an explanatory diagram of a problem in the conventional ultrasonic detecting device.

FIG. 6 is a supplementary diagram for explaining a problem in the conventional ultrasonic detecting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pipe material, 2 ... Substrate, 3 ... Guide rail, 4 ... Servo motor, 5 ... Ultrasonic probe, 6 ... Transceiver circuit, 7 ... Probe drive circuit, 8 ... Thickness measurement circuit, 9 ... Wave number count circuit,
10 ... projection amount calculation circuit, S ₁ to S ₃ ... reflected wave

Claims (5)

[Claims] 1. An inner surface and an outer surface of a butt welded portion of a pipe are cut, and then, in detecting a cutting defect of an inner surface bead, an ultrasonic probe is scanned facing the bead in a direction orthogonal to a bead line. In the method of detecting the cutting failure of the bead on the inner surface of the pipe by transmitting the ultrasonic wave and receiving the reflected wave, pay attention to the number of reflected waves from the inner surface of the pipe, and the number of reflected waves from the inner surface of the pipe. When the value is 1, it is judged that there is no cutting left, and when the number of reflected waves from the tube inner surface side is 2 or more, it is judged that there is cutting left, and a cutting failure detection method for a bead inside the tube. 2. The inner surface of the pipe according to claim 1, wherein when the number of reflected waves from the inner surface of the pipe is 2 or more, the protrusion amount of the uncut portion is obtained from the time difference between the reception timings of the earliest reflected wave and the last reflected wave. A method for detecting defective cutting of beads. 3. The ultrasonic probe having a high frequency, a focused beam and a high damping property is used as the ultrasonic probe.
A method for detecting defective cutting of a bead on the inner surface of a pipe described in 4. A pipe is arranged so as to be movable in a direction orthogonal to the bead line, facing the butt-welded portion from the outer surface side of the pipe, and transmits ultrasonic waves toward the pipe and receives the reflected wave. And a wave number counting circuit that counts the number of reflected waves from the inner surface of the tube. 5. The wave number counting circuit further comprises an arithmetic circuit for obtaining the protrusion amount of the uncut portion from the time difference between the reception timings of the earliest reflected wave and the last reflected wave when the wave number is 2 or more. The device for detecting cutting defects of the bead on the inner surface of the pipe described.