JPS6351505B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting welding defects by acoustic emission, and in particular detects internal defects and their locations by detecting acoustic emission sounds generated from the weld metal being cooled behind the arc during welding. Concerning how to detect.

It is well known that when welding with deep penetration using high current welding, such as submerged arc welding and MIG welding, hot cracking is likely to occur as a welding defect. These hot cracks occur at or just below the solidification temperature range of the weld metal, and include vertical cracks, horizontal cracks, root cracks, and even minute cracks that can be seen under a microscope, but all of them result in a decrease in mechanical properties. This is extremely dangerous as it can lead to These hot cracks can occur not only in the weld metal, but also in coarse grain areas in the heat affected zone adjacent to it.
Internal defects in these parts are difficult to detect by visual inspection.

The purpose of this invention is to provide a method for non-destructively and real-time detection of the extent and location of welding defects, particularly hot cracks, behind the arc during welding, and thereby detecting the extent and location of welding defects in welded joints. The aim is to improve quality.

In other words, this invention recognizes the occurrence of a welding defect by detecting the accompanying acoustic emission sound.
It is possible to accurately detect the extent and location of defects in real time without being disturbed by arc noise, flux cracking sounds, weld metal transformation sounds, etc.

In one aspect of the detection method of the present invention, a master sensor is installed at a position corresponding to a time when defects are likely to occur in the cooling process of a welded part behind a point directly below the arc of a welding torch moving at a predetermined welding speed. A first slave sensor is arranged in front of the master sensor and at a position behind the welding torch, and a second slave sensor is arranged in a position rearward of the master sensor, so that the master sensor and the first While moving the first and second slave sensors integrally with the welding torch without changing their mutual positional relationship, the three detecting with the sensor, comparing the signal arrival order of the detection signal by the master sensor and the detection signal by the first and second slave sensors, and capturing the signal only when the detection signal by the master sensor is in the first arrival order; In this way, only the acoustic emission sound generated near the master sensor is extracted, and from the value of its energy, ringdown count, or effective voltage value, it is calculated from the midpoint position between the first slave sensor and the master sensor to the second The size and position of a defect within the weld bead corresponding to the range up to the midpoint between the slave sensor and the master sensor are determined.

Further, in another aspect of the detection method of the present invention, the welding torch moves at a predetermined welding speed.
A second master sensor is arranged at a second position further rear than the first position, a first slave sensor is arranged immediately before the first master sensor, and a first slave sensor is arranged immediately before the first master sensor. A second slave sensor is disposed immediately after the second master sensor so that the first and second master sensors and the first and second slave sensors are integrally and in mutual positional relationship with the welding torch during welding. These four sensors detect the acoustic emission sound of the weld metal during cooling, which propagates through the base metal and weld metal while moving without changing the and the detection signal from the second slave sensor, and only if the signal arrival order of the detection signal of the first and second master sensors is earlier than that of the first and second spray sensors, the signal is By taking in only the acoustic emission sound generated within the weld bead corresponding to the range between the first and second master sensors, the magnitude and the position of occurrence are detected.

To illustrate an embodiment of the present invention, in FIG. 1, 1 is a base material, 2 is a flux layer, 3 is a welding torch, 4 is a flux hopper nozzle, and 5 is a weld metal, in this example submerged arc welding. This shows the case where it is applied to. A master sensor (M) for detecting acoustic emitted sound is arranged at a distance l ₀ behind the arc point directly below the welding torch 3 in the direction of welding progress (arrow) of the torch, and immediately in front of this master sensor M is a distance l 0. A similar _first slave sensor S ₁ is arranged at a distance l _{1 , and a similar second slave sensor S 2 is} arranged behind the master sensor M at a distance l 2 . These sensors M, S ₁ , and S ₂ are arranged in a line along the joint line on the surface side of the base metal, and are integrally attached to the groove 17 along with the torch 3 without changing their mutual positional relationship as welding progresses. It is designed to move along. The distance l ₀
, that is, the position where the master sensor M is placed is a position behind the welding torch where the sensor is not adversely affected by the thermal effects of the welding arc, and at a predetermined welding speed, the position where the master sensor M is placed is a position where the sensor is not affected by defects in the cooling process of the welded part at a predetermined welding speed. This position corresponds to the period when this is likely to occur.
6 is a signal processing device that processes detection signals from these sensors M, S ₁ and S ₂ , and the output data thereof is recorded and displayed by a recording device 7. That is, within the signal processing device 6, noise removal based on the detection results of the slave sensors S ₁ and S ₂ and quantities related to the magnitude of the acoustic emission sound based on the detection results of the master sensor M, such as ring down count, voltage effective value,
Energy, etc., and temporal determinations are made. The position where the acoustic emission occurs is expressed by a certain constant length a. In other words, as shown in Figure 2, this means that the master sensor M and slave sensor
It is expressed as a region closer to the master sensor M from the midpoint of each of S ₁ and S ₂ . These detection results are recorded by the recording device 7 as data for each welding material. Furthermore, if the defect is determined to be harmful, it is convenient to mark the location where the harmful defect occurs using the marker 16, which will be convenient for cleaning in the subsequent process. This marker 1
It goes without saying that 6 moves integrally with the sensors M, S ₁ , S ₂ and the like.

In FIG. 1, the signal processing device 6 has the following configuration. That is, sensors M, S ₁ , S ₂
The signals captured by the sensors are passed through the preamplifier 8, filter 9, and main amplifier 10, respectively, and these amplify only the necessary frequency components in the signals for easy electrical processing. Enter circuit 11. Here, the detection signal of the master sensor M is compared with the detection signals of both slave sensors S ₁ and S ₂ in terms of signal arrival order, and the result shows that only when the detection signal of the master sensor M is in the first arrival order. This is extracted as a defect detection signal, the rest is removed as noise, and only this defect signal is sent to the signal detection circuit 12. The signal detection circuit 12 detects the amplitude, duration, etc. of the defect signal, sends the detection results to the harmfulness evaluation circuit 14 for judgment, and then sends the output to the recording device 7, and at the same time sends the output to the recording device 7 for harmful defects to the marker activation circuit 15. It instructs the operation of the marker 16.

FIG. 3 shows another embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate equivalent parts.

This example also shows the case of submerged arc welding, in which the first master sensor M ₁ is placed at a first position at a distance l ₀ behind the arc point directly below the torch in the direction of welding progress (arrow) of the torch.
At a second position further backward by a distance L, a second
A master sensor M ₂ is arranged, and a first master sensor M ₂ is arranged immediately before the first master sensor M 1 at a spacing distance l ₁ .
A slave sensor S ₁ is arranged, and also a second slave sensor S ₂ is arranged immediately after the second master sensor M ₂ at a spacing distance l ₂ . These sensors
M ₁ , M ₂ , S ₁ , and S ₂ are all arranged in a line along the joint line on the base metal surface side in order to detect the acoustic emission sound caused by cracks that occur in the weld metal 5 during cooling. As it advances, it moves together with the torch 3 without changing its relative positional relationship. A position at a distance l ₀ from the torch, that is, a first position where the master sensor M ₁ is located, is
The sensor is located behind the welding torch and is not thermally affected by the welding arc, and the distance L, that is, the second position where the master sensor _M2 is located, is
If a flux removal device linked to the welding torch 3 is used, the location will not be affected by the flux removal device, and if the flux removal device is not used, the location will take into account the attenuation of the acoustic emission sound. In addition, the distance l ₁ and
The lower limit of l ₂ is determined by the responses of sensors M ₁ , M ₂ , S ₁ , and S ₂ and the resolution of the signal processing system described below, and is selected to be as small as possible within this lower limit, but usually the sensor diameter It is about twice as large as the previous year. The signal processing device 6 removes noise based on the detection signals of the slave sensors S ₁ and S ₂ and removes the noise from the master sensors M ₁ ,
The magnitude and position of the acoustic emission sound are detected by the detection signal of _M2 , and the detection results are recorded by the recording device 7 as data for each welding material. Furthermore, in the case of a harmful defect, it is possible to mark the position where the harmful defect occurs using 16 markers, as in the previous embodiment.

In the signal processing device 6, first, among the detected sounds of the master sensors M ₁ and M ₂ , the first master sensor
The acoustic component generated near the torch ahead of the position of M ₁ is removed by comparing the relative arrival order with the detection output of slave sensor S ₁ , and similarly, the acoustic component generated near the torch from the position of master sensor M ₁ and M ₂ is removed. 2. The acoustic components generated behind the position of the master sensor _M2 are removed by comparison with the detection output of the slave sensor _S2 ,
As a result, arc noise, which accounts for the majority of the former acoustic component, and flux cracks or flux, which account for the majority of the latter acoustic component, such as crackling noise, are removed as noise. Furthermore, the signal processing device 6 uses master sensors M ₁ and M ₂ from which noise has been removed as described above.
Detecting the harmfulness and position of the defect from the acoustic emission sound generated only within the range of distance L by the detection signal of
This is output to the recording device 7. In this case, the degree of harmfulness of the defect is determined by the amplitude and duration of the master sensor output, and the position of occurrence is determined by the distance x from the master sensor that previously detected the acoustic emission sound, x = (L - Δt・V)/2. In this equation, Δt is the difference in detection time of the acoustic emission sound between the two master sensors, and v is the sound velocity in the weld metal or base material.

In FIG. 3, the signal processing device 6 has the following configuration. That is, sensors M ₁ , M ₂ ,
The signals captured by S ₁ and S ₂ are respectively amplified by a preamplifier 8, a filter 9, and a main amplifier 10 so that only the necessary frequency components in the signals can be easily processed electrically. There is. Here, it is determined whether the signal is a defective signal or noise based on the order in which the signals arrive at the master sensor and the spray sensor, and only those recognized as defective signals are sent to the signal detection circuit 12 and the position locating circuit 13. Position locating circuit 13
Then, the position of the defect is calculated from the difference Δt in signal arrival time to the master sensors M ₁ and M ₂ measured by the time difference comparison circuit 11, and the result is sent to the harmfulness evaluation circuit 14.
send to The signal detection circuit 12 determines the amplitude, duration, etc. of the defective signal, and sends these results to the harmfulness evaluation circuit 14. The harmfulness evaluation circuit 14 determines the harmfulness of the detected defect based on the information sent from the position evaluation circuit 13 and the signal detection circuit 12, outputs it to the recording device 7, and determines whether rework is necessary. Regarding the defective part, the marker operation circuit 15 is operated to mark the position calculated by the position locating circuit 13 with the marker 16.

As described above, in this invention, it is possible to continuously monitor the acoustic emission of only a certain part of the weld metal that is being cooled behind the torch during welding. Therefore, the acoustic emission sound detected by continuous monitoring according to the present invention can be considered to be caused by a welding defect such as hot cracking in the weld metal or heat affected zone, and therefore It is easy to mark welded joints as defects based on recorded data on the location and size of defects, and early repair work on the marked locations can significantly improve the quality of welded joints. It is possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a system configuration according to an embodiment of the present invention, FIG. 2 is a schematic diagram for explaining the area where the sound generation position is limited by the master sensor, and FIG. 3 is a block diagram of a system configuration according to an embodiment of the present invention. FIG. 3 is a block diagram showing another embodiment. 1: base metal, 2: flux, 3: welding torch,
4: Flux hopper, 5: Weld metal, 6: Signal processing device, 7: Recording device, 8: Preamplifier, 9:
filter, 10: main amplifier, 11: time difference comparison circuit, 12: signal detection circuit, 13: position location circuit,
14: Harmfulness evaluation circuit, 15: Marker operation circuit, 16: Marker, 17: Welding groove, M ₁ ,
_M2 , M: Master sensor, _S1 , _S2 : Slave sensor.

Claims (1)

[Claims] 1. A master sensor is arranged at a position directly below the arc of a welding torch that moves at a predetermined welding speed, and a first sensor is arranged at a position in front of this master sensor and at a position behind the welding torch. A slave sensor is arranged, and a second sensor is arranged behind the master sensor.
The master sensor and the first and second slave sensors are moved integrally with the welding torch and without changing their mutual positional relationship while propagating through the base metal and the weld metal during welding. Acoustic emitted sound during cooling of the weld metal is detected by these sensors, and the signal arrival order of the detection signal by the master sensor and the detection signals by the first and second slave sensors is compared, and the detection signal by the master sensor is the first. The signal is taken in only when the arrival order is 1, and from the midpoint position between the first slave sensor and the master sensor to the middle point between the second slave sensor and the master sensor based on the value of its energy, ringdown count, or effective voltage value. A method for detecting a welding defect by acoustic emission, characterized by determining the presence or absence of a defect within a weld bead corresponding to a point position. 2 A first welding torch is placed at a first position behind the point directly below the arc of the welding torch that moves at a predetermined welding speed.
A second master sensor is arranged at a second position further rear than the first position, a first slave sensor is arranged immediately before the first master sensor, and a first slave sensor is arranged immediately before the first master sensor. A second slave sensor is disposed immediately after the second master sensor so that the first and second master sensors and the first and second slave sensors are integrally and in mutual positional relationship with the welding torch during welding. These sensors detect the acoustic emission sound of the weld metal during cooling, which propagates through the base metal and the weld metal while moving without changing the Comparing the signal arrival order with the detected signal by the second slave sensor, it is determined that the signal arrival order to the first and second master sensors is the first and second
By capturing the signal only when it is earlier than that of the slave sensor, only the acoustic emission sound generated within the welding beat corresponding to the range between the first and second master sensors can be extracted and the location of its occurrence can be determined. A method for detecting welding defects by acoustic emission characterized by: