JP2750844B2 - Uranami monitoring method for one-sided wet underwater welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for monitoring a back side of a wet underwater one-sided welding, and more particularly, to a real-time three-dimensional image of a welding back side of a seam formed at the time of wet underwater welding. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring a backwash of wet underwater one-side welding, which is recognized as information and is preferably used for quality control of a submerged weld.

[0002]

2. Description of the Related Art In recent years, technology for constructing ultra-large floating steel structures such as offshore airports, distribution bases, and marine cities by offshore joining has been developed. Such structures are usually box-shaped structures of large area, with the upper part being above the water but the lower part being submerged. As a construction method, a method is generally adopted in which the floating structure of the unit is joined by butt welding to increase the size, but underwater welding is required as this step.

[0003] In the case of constructing such a long and large marine structure by butt welding underwater, or in the case of joining or repairing various steel structures such as submarine oil-related facilities and port facilities, steel plates are required. In many cases, it is necessary to omit the situation where the inversion cannot be performed or to omit the inversion step. Under such construction conditions, one-sided welding in which welding is performed only from the surface side of the steel sheet is employed. In this one-sided welding, the reverse undulation of the first layer sufficiently fuses the joint at the lower part of the welded part, and the weld metal is formed into the proper shape to the back surface, which is the static and dynamic mechanical strength of the joint. And corrosion resistance are extremely important. Therefore, it is important to accurately detect the shape of the Uranami in real time in terms of quality control of the underwater welded joint.

[0004] In the case of one-side welding on land, as is practiced in shipyards and the like, the hull outer plate is welded by submerged arc welding in order to omit the step of reversing the steel plate by large plate joint welding or the like. Welding from one side using a backing device to obtain a sound backwash where the weld metal is sufficiently melted into the back side, or welding method that applies flux from the back side to prevent the molten metal from burning through Have been.
In the case of such one-side welding on land, as a non-destructive quality evaluation method of the Uranami, a manual and automatic ultrasonic bevel flaw detection method is mainly used. This is because the surface of the weld usually has irregularities and is rough, so ultrasonic vertical flaw detection cannot be applied from above the weld bead, and therefore ultrasonic waves are obliquely incident from the base material adjacent to the weld. This is because it is necessary to inspect the welded portion. In this method, for example,
Sound waves must be obliquely injected using an acrylic resin wedge with a fixed angle selected from the thickness of the board, etc.In order to reduce the transmission loss of sound waves, oil or water applied on the surface to be inspected through a couplant such as oil or water Therefore, there is inconvenience that an ultrasonic wave must be incident on the steel plate to detect a welding wave or a reflected wave intensity signal from a back wave. As for the degree of automation, scanning the probe along the welding line and recording the reflection waveform of the defective part has been performed, but it has not been possible to recognize by performing three-dimensional imaging. Not done.

On the other hand, underwater wet welding and the inspection of the surface and inside of the welded portion are performed manually by divers, and are affected by surrounding water and water pressure. And no automatic inspection of Uranami by ultrasonic waves has been performed.

In the future, it is essential that the technology of offshore joining of large floating structures is established as a trend of the times, the demand for automatic welding underwater is increased, and the assurance of joint quality is required. Therefore, it is important to accurately and in real time grasp the shape of the back seam of the joint by wet underwater welding, and to establish an automatic quality control technique for the joint.

[0007]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a real-time, accurate, three-dimensional image information of the welding undulation shape of a seam formed during one-sided wet underwater welding. It is an object of the present invention to provide an underwater monitoring device for wet underwater one-sided welding that is recognized and suitably used for quality control of a wet underwater weld.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to develop a device capable of accurately and accurately recognizing a reverse wake shape of a wet underwater one-sided welding as three-dimensional image information in real time. The measurement system consisting of
The inventors have found that the object can be achieved, and have completed the present invention based on the knowledge.

That is, according to the present invention, an underwater ultrasonic probe is used to butt the two metal plates together from one side of the base material and to form a welding undulation on the back side of the seam formed when performing wet underwater arc welding. The back of wet underwater one-sided welding, characterized by non-destructively measuring and recognizing as three-dimensional image information by a measurement system consisting of a probe, an ultrasonic flaw detector, a probe drive mechanism and a signal processing device A wave monitoring method is provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A system for measuring the shape of a weld penetration wave used in the method of the present invention comprises an underwater ultrasonic probe, an ultrasonic flaw detector, a probe driving device, and a signal processing device. The underwater ultrasonic probe is used as a sensor. One or two underwater ultrasonic probes are installed on the surface of the welding base material, and are automatically scanned along a welding line by a probe driving device to perform ultrasonic waves. Is incident. With this ultrasonic wave incident, the ultrasonic reflected signal obtained from the Uranami bead is observed as an analog waveform by an ultrasonic flaw detector, and is converted from analog to digital to digitize the signal. This is tertiary processed by a signal processing device such as a personal computer. Let it be the original image.

Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing a different example of a joint portion in one-sided welding. 3 shows an example of a V groove when butt welding is performed from one side of the V-shaped groove. Depending on the thickness of the metal plate to be joined, an I-groove or a V-groove is selected as the welding groove, but this example is a V-groove.

In FIG. 1, in one-side welding, it is important that a sufficient penetration of the molten metal is ensured up to the back surface of the seam, and that a well-shaped backwash 2 without molten metal is formed. is there. Insufficient penetration into the back, poor fusion,
If there is a defect such as misalignment, the structure becomes a notch, causing stress corrosion cracking and the like, and often causes destruction and damage of the entire structure. Therefore, it is necessary to pay more attention to the good and bad of the undercut than to the defect inside the welded part so that the proper weld bead formation is performed. FIG.
In these figures, 3, 3 'and 3 "indicate a first layer bead, a second layer bead, and a third layer bead, respectively.

FIG. 2 is a sectional view of an example using a backing metal. In the case of welding in the atmosphere, a band-shaped backing metal 4 made of the same kind of metal material as the base materials 1 and 1 'is used. It is often welded together with the base material and left in general structures.
However, in the sea, the gap 5 between the substrates 1 and 1 'and the backing metal 4 causes corrosion to be promoted. This method is not preferable because the resistance of the fluid increases inside the pipe. Therefore, in the underwater welding, as shown in FIG. 3, an inert gas is used for the backing of the back surface without using the backing metal as much as possible (a water reservoir is locally removed to create a gas reservoir). It is necessary to take measures such as using a flexible backing ring 6 as described above. However, improper backwash may be formed due to melting of the molten metal or poor penetration due to fluctuations in welding conditions and construction conditions, so that it is necessary to monitor these and repair defective parts. In addition, in FIG. 3, 7 is a frame.

FIG. 4 is an explanatory view of an example for explaining the method of the present invention. On the surface side of the substrate 1, one or two underwater ultrasonic probes (sensors) 8 are arranged along a welding line 9. In normal measurement, transmission and reception of ultrasonic waves are performed by one sensor, so one probe may be used. However, in the case where inspection is performed separately from transmission and reception, two probes are used. In other words, two probes are used depending on the shape of the member or the condition of the seam portion, and when inspecting at a high speed.

The ultrasonic probe 8 can be moved along the welding line 9 by using a self-propelled traveling vehicle for underwater welding or a moving mechanism of a welding robot. In addition,
The probe 8 is scanned back and forth within a certain range perpendicular to the welding line 9 in order to cover the inspection area widely and prevent oversight of welding defects, as is also performed in the oblique flaw detection method in air. Is preferred. For this purpose, a front-back scanning mechanism 10 of the probe (by an air motor or a waterproof electric motor) is used. The probe 8 forms a zigzag movement (zigzag scanning) by a combination of the scanning along the welding line 9 and the front-back scanning. The ultrasonic reflected signal obtained from the Uranami bead by such zigzag scanning is observed as an analog waveform on the cathode ray tube of the general-purpose ultrasonic flaw detector 11, and is subjected to A / D conversion (analog / digital conversion) and digital conversion. The image data is recorded and analyzed by a signal processing device (such as a personal computer) 12 to obtain a three-dimensional image. If it is necessary to separate the reflected wave from the noise, a frequency analyzer or the like may be used. In FIG. 4, 13
Is a welding torch, and 14 is an automatic welding device arm (robot arm).

FIG. 5 is a cross-sectional view showing the arrangement of the ultrasonic probe. Here, one vertical ultrasonic probe 81 is used. This is an example in which the probe 8 is inclined with respect to the surface of the substrate 1 and an inspection is performed by a so-called oblique flaw detection method using longitudinal waves in water and transverse waves in steel. For an ultrasonic wave through the water surrounding the probe enters into the steel, couplant such as the case in the air (such as oil) is not required, the incident angle theta ₁ of the ultrasound probe 8 By simply changing the inclination angle of the steel sheet, an appropriate angle can be selected according to the thickness of the steel sheet. That is, this method
In addition to being able to measure the shape of the Uranami 2 in a non-contact manner without being affected by the surface of the base material, it is possible to perform oblique flaw detection at several incident angles θ ₁ and refraction angles θ ₂ with one vertical probe. The advantages of underwater inspection, such as those that are available, can be used and are advantageous. When the inspection of the Uranami 2 is performed at the same time as the welding, the moving speed of the probe 8 is set to be the same as the speed of the underwater welding, but the welding speed is relatively slow, about 20 to 50 cm / min. Scanning the stylus back and forth does not affect the accuracy of the inspection. After the welding is completed, it is of course possible to perform the inspection of the reverse side by using the traveling mechanism of the welding device. In addition, 9 shows a welding part.

FIG. 6 is a cross-sectional view in the case of using two probes, a transmission probe 8A and a reception probe 8B. It is advantageous to apply this two-probe method when the position of the seam part and the back seam do not match due to the difference of the welding joint, or when the inspection is performed without moving back and forth while moving at high speed. It is. Also, it is difficult to distinguish the reflected wave from the unbonded part and the Uranami bead with one probe,
In such a case, the two-probe method is advantageous.

[0018]

Next, the present invention will be described in more detail with reference to examples.

EXAMPLE A steel sheet test piece having a back side model on the back side was measured for the back side shape by the method of the present invention. As a test piece, a mild steel plate having a thickness of 10 mm and a Uranami model having a width of about 2 mm and a height of about 1.5 mm on the surface was used. A part of the back bead was intentionally deleted to form a defective backside bead B to approximate a defective portion where an appropriate bead was not formed. A vertical ultrasonic probe having an effective diameter of 10 mm and a frequency of 1 MHz was used as a sensor. The angle of incidence was selected such that the angle of refraction in the steel was 45 degrees.

FIG. 7 shows the ultrasonic reflection waveform measured in this way as a three-dimensional figure. In this figure, it can be seen that there is a good correlation with the Uranami model having the defect, and at a glance, the quality of the Uranami at each welding position can be identified.

[0021]

According to the method of the present invention, (1) it is possible to measure the shape of a backwash from the substrate surface side in a non-contact manner. ) The sensor part is small and can be easily integrated with the welding torch, and the drive mechanism of the automatic welding device can be used for scanning the sensor. (4) The sensor behind the torch immediately after welding for inspection of Uranami bead There is an advantage that the inspection can be performed again after the welding is completed or after the welding is completed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one-side welding.

FIG. 2 is a cross-sectional view of one-side welding using a backing metal.

FIG. 3 is a cross-sectional view of one-side welding using a flexible backing ring.

FIG. 4 is an explanatory view of the method of the present invention.

FIG. 5 is a sectional view showing an arrangement of an ultrasonic probe in the method of the present invention.

FIG. 6 is a sectional view when two probes are used in the method of the present invention.

FIG. 7 is a three-dimensional ultrasonic reflection waveform diagram in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1 'Substrate 2 Backing wave 3, 3', 3 "bead 4 Backing metal 6 Backing ring 8 Ultrasonic probe 10 Front-back scanning mechanism 11 Ultrasonic flaw detector 12 Signal processing device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-27551 (JP, A) JP-A-52-82382 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 9/095 515 B23K 9/095 510 B23K 31/00 G01B 17/00 G01N 29/10

Claims (1)

(57) [Claims] 1. An underwater ultrasonic probe, an ultrasonic probe, wherein two metal plates are butted from one side of a base material, and a welding undulation shape on a back surface side of a seam formed when wet underwater arc welding is performed. A method for monitoring a back-wave of a single-sided wet underwater welding, wherein the measurement is performed nondestructively by a measurement system including a flaw detector, a probe drive mechanism, and a signal processing device, and recognized as three-dimensional image information.