JP2009085894A - Welded part defect detection method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for detecting welding zone defect, capable of detecting not only the surface but also the internal part or the depth part of the welding zone, and defect of a base material near the welding zone, without applying preprocessing to the welding zone. <P>SOLUTION: An alternating current magnetic field is applied from an exciting coil from an exciting coil to the welding zone where the defect is to be detected, induced electromotive force is generated in an induction coil by the alternating current magnetic field passing the welding zone, and the variation amount of at least one of the amplitude and phase of the induced electromotive force occurring in the induction coil with respect to at least one of the amplitude and phase of a reference induced electromotive force is determined. Thus, the defect in the welding zone is detected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a weld defect detection method and apparatus that can easily and accurately detect the presence or absence of defects in a weld using an electromagnetic induction sensor.

  When joining metals, welding is most commonly used. Welding is widely used in technical fields such as transportation, aviation, vehicles, ships, roads, buildings, structures, and industrial machinery. In recent years, many welding methods suitable for a welding object have been developed, and unmanned work is progressing at welding sites.

  Welding methods can be broadly classified into electric bonding methods, mechanical bonding methods, chemical reaction bonding methods, and crystal bonding methods. Examples of the electric joining method include an arc welding method, a plasma welding method, a high frequency welding method, and a laser welding method. Examples of the mechanical joining method include a friction welding method and an ultrasonic welding method. Examples of chemical bonding methods include thermite welding method, gas welding method, and explosion welding method. Examples of crystal bonding methods include diffusion welding and brazing.

  The welding methods enumerated above enable joining suitable for the purpose. However, each welding method also has a basic problem of stably maintaining the heat input state and the progress of welding, and therefore there is always a problem in the welding process. In particular, when welding is performed in the field related to automobiles, defects in the welding process are a major problem.

  In addition, in the fields of structures, roads, bridges, etc., since a large weight is applied to the welded part and a large vibration is applied to the welded part for a long period of time, there is a possibility that a crack may occur in that part. . For example, it has recently been reported that cracks have occurred in welds on the Metropolitan Expressway. Cracks due to load and vibration can also occur at welds in bridges. In this case, cracks may occur in the base metal in the vicinity of the welded portion together with the weld bead, and the presence or absence of such cracks is confirmed by on-site inspection.

  In the marine field, a huge hull and a huge heavy object float in the waves, so that distortion is accumulated in the welded portion and cracks may occur. For this reason, in a cargo ship etc., the person in charge is obliged to visually inspect the main part during the voyage. In tankers, etc., inspection of the welded part of the balance tank is performed when docked. That is, since seawater enters the balance tank and shells, barnacles, rust and the like are generated, the welded portion is first cleaned, and then crack detection is performed by magnetic particle flaw detection.

  Thus, inspection of welds is very important. However, at present, it is impossible to inspect all welds. That is, although a method of nondestructive inspection has been established, labor for pre-processing and post-processing for inspection, labor costs, inspection costs, etc. are enormous, and inspection requires a lot of time. is there.

  For example, in the inspection method using ultrasonic waves, it is necessary to first perform the cleaning from the weld bead and the vicinity of the weld bead. If there is paint on the part, it is necessary to peel off the paint. Next, it is necessary to apply a medium for facilitating the passage of ultrasonic waves to the inspection unit. Thereafter, the inspection is started, but the inspection speed is generally slow, and the difference due to the skill of the person to be inspected becomes a big problem. Moreover, if the welding location is complicated, malfunctions are likely to occur, and the detection accuracy may be reduced. After the inspection is complete, the media must be removed and painted. Therefore, it is impossible to inspect all the welds in consideration of time and labor. In addition, there is a problem that the materials used for the pretreatment and the posttreatment and the treatment of the remaining materials may cause environmental problems.

  Inspection methods using X-rays are greatly limited in use on site. In addition, the X-ray irradiation side and the light-receiving side need to be paired, but the welded portion is usually in a bag state, and there is a method of installing a dry plate for receiving X-rays. There is no actual situation. Moreover, since X-rays are expensive, they are used only for inspection of special parts. Furthermore, there is also a problem that the inspection time becomes longer because a photograph is taken.

  Similar to the inspection method using ultrasonic flaw detection, the inspection method using penetrating flaw detection needs to start with cleaning of the welded portion, and then the weld opening defect is cleaned using a solvent. At that time, it is processed so that the penetrant can penetrate into the opening defect. Next, the color liquid is infiltrated, the surface is cleaned and the white medium is sprayed, and after a few minutes, the portion where the red color is floating on the white medium portion is visually judged as a crack. After inspection, cleaning and post-processing are performed. The problem is that the depth of the crack is unknown.

  The inspection method using magnetic particle inspection also starts with cleaning. However, this inspection method detects an opening defect in the welded portion, and cannot inspect and detect the inside of the welded portion at all. There is an advantage that the inspection time can be shortened compared to the inspection method using ultrasonic flaw detection or penetration flaw detection.

  In the inspection method using magnetic particle flaw detection, since the fluorescent material is contained in the magnetic particle material, post-processing is troublesome. That is, it is necessary to wash away the fluorescent material for magnetic particle flaw detection with water, collect the waste water, and separate the water and the fluorescent material by a special method. If this treatment is not performed, a large amount of fluorescent material will flow out to the natural environment, which is an environmental problem.

  As described above, the welding method itself has been established, but it is required to simplify the nondestructive inspection of the welded portion.

  On the other hand, in the in-line inspection, it is important to control the welding conditions by quickly feeding back the quality determination information. If this is not done, in lot management, it will be wasteful if it is passed to the next process while the quality is unknown or discarded as a defective product, which directly leads to energy problems and environmental problems.

  In the fields of ships, structures, plants, etc., it is necessary to inspect all the welded parts, but at present, only the important parts are inspected for physical reasons. Today, there is a defect detection method for inspection of welded parts without pre-processing and post-processing, and with a short inspection time, which can detect not only the surface of the welded part but also internal defects, as well as base metal defects near the welded part. The development is urgent.

  In recent years, a nondestructive inspection method of a welded part using magnetism has been proposed (for example, see Patent Document 1). In this nondestructive inspection method, in order to shorten the time required for flaw detection and facilitate the flaw detection of flaw detection results, the flaw detection probe has its flaw detection surface facing the surface near the weld and the flaw detection probe. The detection probe is arranged so that the magnetic sensing surface is parallel to the welding direction of the welded portion, and the flaw detection probe is moved so that the flaw detection surface is displaced along the welding direction of the welded portion. The exciting coil generates an eddy current by generating a magnetic flux extending outward. As a result, when a flaw is present in the welded portion, the state of leakage magnetic flux due to eddy current changes, and the detection coil detects a change in the component of the leakage magnetic flux parallel to the surface of the welded portion, and performs flaw detection in a range not facing the flaw detection surface. Is.

JP 2005-164442 A

  The nondestructive inspection method described in Patent Document 1 is a method generally called an eddy current method. This eddy current method uses an eddy current generated in a test object by an induced electromotive force when a coil to which an alternating current is applied is brought close to a conductive test object.

  However, such an eddy current method is not suitable for detecting a deep portion of an object to be inspected. Moreover, in the eddy current method, the surface condition of the object to be inspected greatly affects the detection sensitivity. For example, welds with bead irregularities in arc welding, painted welds, welds with oxides attached, etc. When it is desired to detect a defect, a pretreatment such as smoothing the surface or removing an oxide film or a coating film is necessarily required. Furthermore, it cannot be detected unless the surface of the weld is open. For this reason, the eddy current method is hardly used in practice for detecting defects in welds.

  Therefore, the present invention solves the above-mentioned problems of the prior art, and its purpose is not to pre-treat the welded part, but also to the surface of the welded part as well as the inside or the deep part thereof, and the welded part. An object of the present invention is to provide a weld defect detection method and apparatus capable of detecting a defect in a nearby base material.

  According to the present invention, an alternating magnetic field is applied from an exciting coil to a weld to be detected for defect, an induced electromotive force is generated in the induction coil by the alternating magnetic field passing through the weld, and the amplitude of the induced electromotive force generated in the induction coil. And a weld defect detection method for detecting a defect in a weld by obtaining a change in at least one of the amplitude and the phase of a reference induced electromotive force in at least one of the phase and the phase.

  In order to detect a defect in the welded portion, an AC magnetic field is applied to the welded portion from the exciting coil, and an induced electromotive force is generated in the induction coil by the AC magnetic field passing through the welded portion. A change amount of at least one of the amplitude and phase of the generated induced electromotive force with respect to at least one of the amplitude and phase of the reference induced electromotive force is obtained. In the present invention, the defect of the welded portion includes not only the surface defect, internal defect and back surface defect of the welded portion itself but also the surface defect, internal defect and back surface defect of the base material in the vicinity of the welded portion. In this way, the magnetic field lines due to the alternating magnetic field are applied to the welded portion, and the minute change in the magnetic field lines is taken out as an induced electromotive force. It is possible to detect a deep part and also a defect of a base material in the vicinity of the welded part.

  It is preferable to obtain the reference induced electromotive force by applying an alternating magnetic field from the exciting coil to the reference welded portion where no defect exists, and generating the induced electromotive force in the induction coil by the alternating magnetic field passing through the reference welded portion.

  It is also preferable to determine the amount of change of both the amplitude and phase of the induced electromotive force generated in the induction coil with respect to the amplitude and phase of the reference induced electromotive force.

  It is also preferable to determine whether or not a defect exists in the weld by determining whether or not the amount of change is zero.

  It is also preferable to determine whether or not a defect exists in the weld by comparing the amount of change in amplitude and the amount of change in phase and determining whether the magnitudes of both have reversed.

  It is also preferable to apply an alternating magnetic field and generate an induced electromotive force using an electromagnetic induction sensor in which an excitation coil and an induction coil are integrally provided.

  It is also preferable to apply an alternating magnetic field and generate an induced electromotive force using an electromagnetic induction sensor in which an exciting coil and an induction coil are wound coaxially.

  Applying an alternating magnetic field and generating an induced electromotive force in a state where the electromagnetic induction sensor and the weld are not in contact, or applying an alternating magnetic field and generating an induced electromotive force in a state where the electromagnetic induction sensor and the weld are in contact It is also preferable to carry out.

  According to the present invention, an exciting coil for applying an AC magnetic field to a weld to be detected for defects, an induction coil for generating an induced electromotive force by an AC magnetic field passing through the weld, and an induction generated in the induction coil Detection of a weld defect including at least one of the amplitude and phase of the electromotive force and a detection unit for detecting a defect of the weld by obtaining a change amount relative to at least one of the amplitude and phase of the reference induced electromotive force An apparatus is provided.

  In order to detect a defect in the welded portion, an AC magnetic field is applied to the welded portion from the exciting coil, and an induced electromotive force is generated in the induction coil by the AC magnetic field passing through the welded portion. The detection unit obtains a change amount of at least one of the amplitude and phase of the induced electromotive force with respect to at least one of the amplitude and phase of the reference induced electromotive force. In the present invention, the defect of the welded portion includes not only the surface defect, internal defect and back surface defect of the welded portion itself but also the surface defect, internal defect and back surface defect of the base material in the vicinity of the welded portion. In this way, the magnetic field lines due to the alternating magnetic field are applied to the welded portion, and the minute change in the magnetic field lines is taken out as an induced electromotive force. It is possible to detect a deep part and also a defect of a base material in the vicinity of the welded part.

  It is preferable to further include an AC power source for supplying an AC current to the exciting coil.

  It is also preferable that the detection unit is configured to obtain a change amount of both the amplitude and phase of the induced electromotive force generated in the induction coil with respect to the amplitude and phase of the reference induced electromotive force.

  It is also preferable that the detection unit includes a circuit that determines whether or not a defect exists in the welded portion by determining whether or not the change amount is zero.

  The detection unit includes a circuit that compares the amount of change in amplitude with the amount of change in phase and determines whether or not a defect exists in the welded portion by determining whether the magnitude of both is reversed. It is also preferable.

  It is also preferable to include an electromagnetic induction sensor in which an excitation coil and an induction coil are integrally provided.

  It is also preferable to include an electromagnetic induction sensor in which an exciting coil and an induction coil are wound coaxially.

  A sensor support that holds the electromagnetic induction sensor so that the electromagnetic induction sensor and the welded part are not in contact with each other, or a sensor support that holds the electromagnetic induction sensor so that the electromagnetic induction sensor and the welded part are in contact with each other. It is also preferable to further include a portion.

  According to the present invention, a magnetic force line due to an alternating magnetic field is applied to the welded portion, and a minute change in the magnetic force line is taken out as an induced electromotive force. It is possible to detect the inside or the deep part, and also the defect in the base material near the welded part.

  FIG. 1 is a diagram schematically showing an overall configuration of an embodiment of a weld defect detection device according to the present invention and an example of its usage, and FIG. 2 is a diagram showing a configuration of an electromagnetic induction sensor in the embodiment of FIG. is there.

  In FIG. 1, 10 is a weld defect detection device, 11 is an electromagnetic induction sensor of the weld defect detection device 10, 12 is a sensor support for holding the electromagnetic induction sensor 11, and 13 is a defect inspection formed on a base material 14. Each weld is to be shown.

  The sensor support unit 12 holds the electromagnetic induction sensor 11 in a state in which the electromagnetic induction sensor 11 is approached to a position away from the surface of the welded part 13 as a measurement object by a predetermined distance. Note that the shape and form of the sensor support 12 are not limited to those shown in the figure. For example, while holding the electromagnetic induction sensor 11 at a position away from the surface of the weld 13 by a predetermined distance, The structure which added the mechanism which can move along the welding part 13 at a predetermined speed may be sufficient.

  As shown in FIG. 2, the electromagnetic induction sensor 11 includes an excitation coil 11 a and an induction coil 11 b, and the excitation coil 11 a is electrically connected to an AC power supply 15, and the induction coil 11 b is connected to the detection unit 16. Electrically connected.

  Specifically, the electromagnetic induction sensor 11 is excited by application of alternating current to form a primary excitation coil 11a, and the excitation coil 11a is excited and electromagnetically induced to generate an electromotive force V. And a secondary induction coil 11b. The exciting coil 11a and the induction coil 11b are coaxial and are integrally wound and wound over the entire length. In this case, the induction coil 11b is wound around the excitation coil 11a. These coils can be realized by winding an insulating film wire around a long cylindrical object.

  The number of turns of the exciting coil 11a is determined by the material of the base material 14 to be welded, the measurement range of the welded portion 13 which is a sample to be inspected, and the like. Further, the frequency f of the alternating current applied to the exciting coil 11a is also determined by the material of the base material 14 to be welded, the measurement range of the welded portion 13, and the like. The frequency f of the alternating current affects the penetration depth δ of the magnetic flux into the welded portion 13 and also affects the electromotive force V generated in the induction coil 11 b by the welded portion 13. In the present embodiment, the frequency f is determined in order to inspect the welded portion 13 located around the electromagnetic induction sensor 11, thereby making it possible to detect subtle changes in internal defects in the welded portion 13.

  Although not shown, the AC power supply 15 includes a sine wave oscillator and a constant current amplifier, and the AC voltage of the angular frequency ω (= 2πf) output from the sine wave oscillator becomes a constant current by the constant current amplifier. It is configured to be supplied to the excitation coil 11 a of the electromagnetic induction sensor 11.

  The detection unit 16 receives the electromotive force V of the induction coil 11b of the electromagnetic induction sensor 11 as an electrical signal, and compares the measured value Vout of the electromotive force with the reference value Vref, thereby comparing and detecting a change in the magnetic field. And a determination circuit 16b for determining the defect state of the welded portion 13 based on the output of the comparison circuit 16a.

  That is, in the comparison circuit 16a of the detection unit 16, the output (reference value Vref) of the induction coil 11b when the electromagnetic induction sensor 11 is applied to a reference welded portion that is a reference sample, and the electromagnetic induction sensor 11 as a sample to be inspected. The output (measured value Vout) of the induction coil 11b when applied to a certain welded portion 13 is compared. In this case, the phase change amount Δθ and the amplitude change amount ΔH of the measured value Vout with respect to the reference value Vref are individually compared.

  FIG. 3 is a model diagram of an electrical signal output from the electromagnetic induction sensor in the embodiment of FIG.

  As shown in the figure, the change amount of the measurement value Vout with respect to the reference value Vref is detected separately for each of the phase change amount Δθ and the amplitude change amount ΔH. This phase change amount Δθ is an amount depending on the magnetic characteristic of the welded portion 13 that is the specimen to be inspected, that is, the magnetic permeability, and the amplitude change amount ΔH is dependent on the electrical characteristic of the welded portion 13, that is, the electric conductivity. The amount to be. In this way, by detecting the magnetic characteristics and electrical characteristics of the welded portion 13 separately, it is possible to detect subtle changes in the defect state of the welded portion 13. That is, it is possible to detect a subtle difference in internal defects of the welded portion 13.

  The determination circuit 16b of the detection unit 16 determines whether or not the welded part 13 is in a normal state based on the output of the comparison circuit 16a. If both the phase change amount Δθ and the amplitude change amount ΔH are zero, it is determined that the welded portion 13 is in a normal state. If the phase change amount Δθ and the amplitude change amount ΔH described above are associated with the state of the welded portion 13 and converted into data in advance in the determination circuit 16b, what is the state of the abnormality in the welded portion 13? It is possible to specifically identify and grasp the state of blowholes, foreign matters, cracks, and the like.

  As shown in FIG. 1, a recording unit 17, a display unit 18, and a storage unit 19 are connected to the detection unit 16. The recording unit 16 records a measurement state, a measurement result, and the like on a recording medium such as a recording sheet. The display unit 18 displays a measurement state, a measurement result, and the like. For example, the display unit 18 displays an installation position of the electromagnetic induction sensor 11 or displays a measurement result. On the display unit 18, the measurement state, the measurement result, and the like can be displayed as graphics or numbers. The storage unit 19 stores the output of the electromagnetic induction sensor 110, the measurement state, the measurement result, and the like, and can read out the stored data when necessary.

  FIG. 4 is a flowchart for explaining the operation of the weld defect detection apparatus in the present embodiment. Hereinafter, the weld defect detection operation will be described with reference to FIG.

  When inspecting whether or not there is a defect in the welded portion, first, prepare a welded portion (not shown) which is a reference sample having no defect, and measure the electromagnetic induction sensor 11 close to the welded portion, This is set as a reference value Vref (step S1). That is, the output of the induction coil 11b from the welded portion, which is a standard sample, is used as a reference threshold value as the reference value Vref.

  Next, the electromagnetic induction sensor 11 is brought close to the surface of the welded portion 13 that is a sample to be inspected, and the sensor support portion 12 is brought close to the position of a predetermined distance from the surface of the welded portion 13 to maintain this state. In this state, an alternating current having a predetermined frequency f is supplied to the exciting coil 11a of the electromagnetic induction sensor 11 to apply an alternating magnetic field to the welding portion 13, and an induced electromotive force V is generated in the induction coil 11b of the electromagnetic induction sensor 11, The value is set as a measured value Vout (step S2). In this case, the induced electromotive force V generated in the induction coil 11 b changes according to the magnetic flux density of the AC magnetic field applied to the welded portion 13, and the magnetic flux density of the AC magnetic field is a defect existing inside the welded portion 13. Varies depending on the degree.

  Next, the measured value Vout, which is the induced electromotive force generated in the induction coil 11b with respect to the welded portion 13, is compared with the reference value Vref, which is the induced electromotive force generated in the induction coil 11b, with respect to the welded portion that is a reference sample and has no defects. Thus, the phase change amount Δθ and the amplitude change amount ΔH are detected (step S3). Both the phase change amount Δθ and the amplitude change amount ΔH may be detected, or one of them may be detected.

  Next, it is determined from the comparison result whether or not the welded portion 13 is in a normal state (step S4). This determination is performed by determining whether or not the phase change amount Δθ and the amplitude change amount ΔH are zero. If both are zero, it is determined that the welded portion 13 is in a normal state (a state without defects) (step S5). On the contrary, if one of them is not zero, it is determined that the welded portion 13 is in an abnormal state (defective state) (step S6). By this determination, it is possible to accurately inspect whether or not a defect exists in the welded portion 13.

  The measurement result and the determination result are recorded in the recording unit 17 as necessary, displayed on the display unit 18, and / or stored in the storage unit 19 (step S7).

  As described above, according to the present embodiment, the electromagnetic induction sensor 11 in which the excitation coil 11 a and the induction coil 11 b are integrally formed as a coaxial as a sensor for detecting whether or not there is a defect in the welded portion 13. The excitation coil 11a is applied with an alternating current to form a magnetic field, the induction coil 11b detects a change in the magnetic field due to the welded portion 13, and the amplitude and / or phase of the induced electromotive force generated in the induction coil 11b, for example. Therefore, the existence of a defect in the weld can be estimated. That is, it is possible to accurately and easily obtain the presence / absence of a weld defect, which has conventionally been impossible, by nondestructive inspection. In other words, it is possible to inspect and detect fine cracks, blowholes, foreign matter entrainment, welding state, and the like occurring in the welded part, the base metal in the vicinity of the welded part, etc. with high resolution and high sensitivity.

  Further, since the electromagnetic induction sensor 11 and the welded portion 13 are not in contact with each other, the surface of the welded portion is smoothed for inspection as in the prior art, or an oxide film or coating film is removed. There is no need for pre-treatment such as stripping barnacles, saving costs and labor, enabling inspection of all welds, and easy identification of weld defect inspections, so the inspection results can be designed. It can be easily reflected. Furthermore, environmental problems can be cleared because chemicals such as solvents and fluorescent paints are not used for inspection. Moreover, since the inspection time is fast, it is possible to finish the welded portion inspection in a desired range in a short time.

  Furthermore, since the distance between the welded portion to be inspected and the sensor can be sufficiently secured, the inspection becomes easy. Further, it is not necessary to direct the sensor vertically to the welded portion to be inspected, and it is possible to inspect at an angle that allows easy inspection. Furthermore, it is easy to handle and anyone can operate. Even if there are corrugations on the weld, especially arc weld beads, it will not be affected by defect inspection detection.

  FIG. 5 is a diagram showing an example of data actually measured by the weld defect inspection apparatus 10 described above.

  This measurement was performed on a welded portion 13 by butt welding for joining a flat base material 14 as shown in FIG. However, the moving speed of the electromagnetic induction sensor 11 was constant. The base material 14 was made of steel and was used for the purpose of detecting an internal blowhole that is an internal defect of the welded portion 13. Since the thickness of the base material is 20 mm, the frequency used was 18.01 KHz. The exciting coil 11b has 300 turns and the conductor thickness is 0.3 mm, and the induction coil 11b has 450 turns and the conductor thickness is 0.2 mm. The configuration of the weld defect inspection apparatus used for this measurement is merely an example, and the configuration of the present invention is not limited to this. For example, the shapes of the exciting coil and the induction coil may not be cylindrical as shown in FIG. 2, or may not be concentric. Moreover, the used frequency and the number of coil turns are not limited to this.

  FIG. 5A shows raw data relating to the phase change amount Δθ that is not subjected to signal processing, and FIG. 5B shows a signal output obtained by filtering the raw data with an electric circuit. In the portion of the output signal A, l is proportional to the blowhole width, and h is proportional to the size of the cavity. Accordingly, the blow hole width is long and the cavity is large in the portion of the output signal B. In the portion of the output signal C, it is a small cavity. In the portion of the output signal D, the blow hole width corresponding to l is about the same as i, but h is large, which means that it is a vertically long defect. Such a good detection result can be obtained by measuring the magnetic characteristics or electrical characteristics of the welded portion 13 using the welded portion defect inspection apparatus 10 and further performing signal processing.

  FIG. 6 is a diagram for explaining a case where a crack on the back surface of the welded portion is detected by the welded defect inspection apparatus 10 described above.

  As shown in FIG. 2A, it is assumed that butt welding is performed on a base material 64 made of SUS321 and having a thickness of 40 mm, and a crack 63a having a depth of 11 mm is present on the back surface portion of the welded portion 63. As shown in FIG. 5B, an electromagnetic induction sensor 61 attached to a vehicle sensor support 62 is brought close to the surface of the weld 63 via a plastic plate 60 having a thickness of 1.5 mm. (C)) is applied with an alternating current to form a magnetic field, and the induction coil 61b (FIG. (C)) detects a change in the magnetic field in the weld 63, and the amplitude of the induced electromotive force generated in the induction coil 61b and Measure the amount of phase change. As shown in FIG. 6C, the exciting coil 61a and the induction coil 61b are coaxially integrated, the use frequency is 10.1 KHz, the number of turns of the exciting coil 61a is 210 turns, and the wire thickness is φ0. 0.1 mm, the number of turns of the induction coil 61b was 400 turns, and the thickness of the conducting wire was φ0.1 mm. However, when detecting cracks on the back surface of the welded portion in this way, the operating frequency, the number of turns of the coil, and the thickness of the conducting wire are not limited to the above values.

  FIG. 3D shows a signal output obtained by reciprocating the electromagnetic induction sensor 61 at a constant speed and filtering the phase change amount Δθ of the induced electromotive force. It can be seen that waveform changes (two places for reciprocation) occur in the crack 63a.

  In FIG. 5E, the electromagnetic induction sensor 61 is not moved at a constant speed as described above, but fixed point measurement is performed in a state where it is stopped at a desired position, and the phase change amount Δθ and amplitude change amount ΔH of the induced electromotive force are measured. The results of detecting whether or not there is a crack in the welded part by comparing the two and determining whether or not the sizes of the two are reversed are shown. The phase change amount Δθ is larger than the amplitude change amount ΔH at a position where there is no crack, and this is reversed at the position where the crack exists, so that the amplitude change amount ΔH is larger than the phase change amount Δθ. At a position where there is a crack, the interval S between the phase change amount Δθ and the amplitude change amount ΔH is output as a signal proportional to the depth of the crack.

  FIG. 7 is a flowchart for explaining the operation of the weld defect detection apparatus in the fixed point measurement method shown in FIG. Hereinafter, the weld defect detection operation in this case will be described with reference to FIG.

  First, a welded part (not shown), which is a reference sample having no defect, is prepared, the electromagnetic induction sensor 61 is brought close to the welded part, measurement is performed, and this is set as a reference value Vref (step S11). That is, the output of the induction coil 61b from the welded portion, which is a standard sample, is used as the determination threshold value as the reference value Vref.

  Next, the electromagnetic induction sensor 61 is brought close to the surface of the welded portion 63 that is a sample to be inspected, and is brought close to a predetermined distance from the surface of the welded portion 63 by the sensor support portion 62, and this state is maintained. In this state, an alternating current having a predetermined frequency f is supplied to the exciting coil 61a of the electromagnetic induction sensor 61 to apply an alternating magnetic field to the welding portion 63, and an induced electromotive force V is generated in the induction coil 61b of the electromagnetic induction sensor 61. The value is set as a measured value Vout (step S12). In this case, the induced electromotive force V generated in the induction coil 61 b changes in accordance with the magnetic flux density of the AC magnetic field applied to the welded portion 63, and the magnetic flux density of the AC magnetic field is a defect existing inside the welded portion 63. Varies depending on the degree.

  Next, the measured value Vout, which is the induced electromotive force generated in the induction coil 61b with respect to the welded portion 63, is compared with the reference value Vref, which is the induced electromotive force generated in the induction coil 61b, with respect to the welded portion that is a reference sample and has no defects. Then, the phase change amount Δθ and the amplitude change amount ΔH are detected (step S13).

  Next, the phase change amount Δθ and the amplitude change amount ΔH are compared, and it is determined whether or not the welded portion 63 is in a normal state based on whether the magnitudes of both are reversed (step S14). That is, when the welding portion 63 is in a normal state, the phase change amount Δθ is set to be larger than the amplitude change amount ΔH (the amplitude change amount ΔH is set to be larger than the phase change amount Δθ. If there is no reversal and the phase change amount Δθ remains larger than the amplitude change amount ΔH, it is determined that the position of the welded portion 63 is in a normal state (no defect state) (step S15). ). Conversely, when there is a reverse rotation and the phase change amount Δθ is smaller than the amplitude change amount ΔH, it is determined that the position of the welded portion 63 is in an abnormal state (defective state) (step S16). .

  By performing the above detection by changing the position of the electromagnetic induction sensor 61, it is possible to accurately inspect whether or not a defect exists in the welded portion 63.

  The measurement result and the determination result are recorded in the recording unit 17 as necessary, displayed on the display unit 18, and / or stored in the storage unit 19 (step S17).

  FIG. 8 is a diagram for explaining a case where a weld penetration state with respect to the base material of the fillet weld is detected by the weld defect inspection apparatus 10.

  As shown in FIGS. 6A and 6B, fillet welding is performed on a base material 84 made of steel and having a thickness of 25 mm. As shown in FIG. It is detected whether welding penetration has not been made in the base material 84, or whether welding penetration has been made in the base material 84 and the penetration portion 83a exists as shown in FIG.

In this detection, fixed-point measurement is performed in a state where an electromagnetic induction sensor 81 having the same structure as that shown in FIG. 1 is stopped at a desired position, and a phase change amount Δθ and an amplitude change amount ΔH of the induced electromotive force are detected. Then, the two are compared, and it is determined whether or not the melted portion 83a exists in the welded portion 83 by determining whether or not the sizes of both are reversed. FIG. 3C shows the result. The phase change amount Δθ is larger than the amplitude change amount ΔH at the position where the welding penetration is present and is OK, and the position where welding penetration exists is reversed and the amplitude change amount ΔH is larger than the phase change amount Δθ and is NG. . Penetration is the spacing S ₁ between the phase change amount Δθ and the amplitude change amount ΔH at position (OK portion) that is adapted outputted as a signal which is proportional to the welding penetration depth, at a position where the penetration is not performed (NG section) spacing S ₂ between the phase change amount Δθ and the amplitude change amount ΔH is output as a signal which is proportional to the magnitude of the welding penetration observed defect.

  In this welding penetration state detection, the operating frequency is 18.01 KHz, the number of turns of the exciting coil of the electromagnetic induction sensor 81 is 300 turns, the conductor thickness is φ0.3 mm, the number of induction coil turns is 450 turns, the conductor thickness. Was φ0.2 mm. However, when detecting the weld penetration state in this way, the operating frequency, the number of turns of the coil, and the thickness of the conducting wire are not limited to the above values.

  FIG. 9 is a diagram for explaining a case where a defect in a fillet weld is detected by the weld defect inspection apparatus 10.

  As shown in FIGS. 2A and 2B, fillet welding is performed on a base material 94 made of a steel material having a thickness of 25 mm, a depth of 200 mm, and a width of 300 mm. Specifically, (a) slab entrainment, (b) cracking, (c) blow hole, and (d) blow hole are formed in the welded portion 93 in a pseudo manner at predetermined intervals (60 mm). However, the size of the defect is unknown.

  With respect to such a welded portion 93, the electromagnetic induction sensor 91 having the same structure as that shown in FIG. 1 is reciprocated at a constant speed on the weld bead while being in contact with the welded portion 93 at an appropriate angle. . That is, an alternating current is applied to the exciting coil of the electromagnetic induction sensor 91 to form a magnetic field, a change in the magnetic field in the welded portion 93 is detected by the induction coil, and the amount of change in amplitude and phase of the induced electromotive force generated in the induction coil Was measured. The operating frequency was 18.01 KHz, the number of excitation coil turns was 300 turns, the conductor thickness was 0.3 mm, the induction coil was 450 turns, and the conductor thickness was 0.2 mm. However, when detecting a defect in the welded portion 93 in this way, the operating frequency, the number of turns of the coil, and the thickness of the conducting wire are not limited to the above values.

  FIG. 4C shows a signal output obtained by filtering the phase change amount Δθ of the induced electromotive force of the electromagnetic induction sensor 91. Waveform changes are recognized corresponding to the pseudo defects (a) to (d). Since it is reciprocating, a symmetrically inverted signal appears and the reproducibility is very good.

  FIG. 10 is a diagram for explaining a case where a defect in an aluminum plate butt weld is detected by the weld defect inspection apparatus 10.

  As shown in FIG. 2A, butt welding (bead width 10 mm) is made on a base material 104 made of an aluminum plate and having a thickness of 5.0 mm and a depth of 60 mm, and a crack 103 a is formed on the back surface of the welded portion 103. Existing. As shown in FIG. 5B, the electromagnetic induction sensor 101 is brought close to the surface of the welded portion 103, and an alternating current is applied to the excitation coil 101a (FIG. 5C) in a state where it does not come into contact (a separation distance of 3 mm). Then, the magnetic field is formed, the change of the magnetic field in the welded portion 103 is detected by the induction coil 101b (FIG. 3C), and the amount of change in the amplitude and phase of the induced electromotive force generated in the induction coil 101b is measured. As shown in FIG. 5C, the exciting coil 101a and the induction coil 101b are coaxially integrated, the use frequency is 12.05 KHz, the number of turns of the exciting coil 101a is 300 turns, and the conductor thickness is φ0. 0.1 mm, the number of turns of the induction coil 101b was 500 turns, and the thickness of the conductive wire was 0.1 mm. However, when detecting cracks on the back surface of the welded portion in this way, the operating frequency, the number of turns of the coil, and the thickness of the conducting wire are not limited to the above values.

  In FIG. 4D, the electromagnetic induction sensor 101 is reciprocally moved relative to the base material 104 at a constant speed (in this example, the electromagnetic induction sensor 101 is fixed and the base material 104 is moved). A signal output obtained by filtering the phase change amount Δθ of the electromotive force is shown. It can be seen that waveform changes (two places for reciprocation) occur in the crack 103a. h is proportional to the depth of the crack 103a, and l is proportional to the length of the crack 103a.

  All the embodiments described above are illustrative of the present invention and are not intended to be limiting, and the present invention can be implemented in other various modifications and changes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

It is a figure which shows roughly the whole structure of one Embodiment of the welding part defect detection apparatus in this invention, and its usage example. It is a figure which shows the structure of the electromagnetic induction sensor in embodiment of FIG. It is a model figure of the electrical signal output from the electromagnetic induction sensor in embodiment of FIG. It is a flowchart explaining operation | movement of the welding part defect detection apparatus in embodiment of FIG. It is a figure which shows an example of the data actually measured by the welding part defect inspection apparatus in embodiment of FIG. It is a figure explaining the case where the crack in the back surface of a welding part is detected by the welding part defect inspection apparatus in embodiment of FIG. It is a flowchart explaining operation | movement of the welding part defect detection apparatus in the fixed point measuring method of FIG.6 (E). It is a figure explaining the case where the welding penetration state with respect to the base material of a fillet weld part is detected by the weld part defect inspection apparatus in the embodiment of FIG. It is a figure explaining the case where the defect of a fillet weld part is detected by the weld part defect inspection apparatus in embodiment of FIG. It is a figure explaining the case where the defect of the butt-welding part of an aluminum plate is detected by the welding part defect inspection apparatus in embodiment of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Welding part defect detection apparatus 11, 61, 81, 91, 101 Electromagnetic induction sensor 11a, 61a, 101a Excitation coil 11b, 61b, 101b Induction coil 12 Sensor support part 13, 63, 83, 93, 103 Welding part 14, 64 , 84, 94, 104 Base material 15 AC power supply 16 Detection unit 16a Comparison circuit 16b Judgment circuit 17 Recording unit 18 Display unit 19 Storage unit 60 Plastic plate 62 Car sensor support unit 63a, 103a Crack 83a Melting location

Claims (18)

  An alternating magnetic field is applied from the exciting coil to the weld to be detected for defect detection, an induced electromotive force is generated in the induction coil by the alternating magnetic field passing through the weld, and the amplitude and phase of the induced electromotive force generated in the induction coil are A weld defect detection method, comprising: detecting a defect in the weld by obtaining a change amount relative to at least one of an amplitude and a phase of a reference induced electromotive force.   The reference induced electromotive force is obtained by applying an alternating magnetic field from the exciting coil to a reference welded portion having no defect and generating the induced electromotive force in the induction coil by the alternating magnetic field passing through the reference welded portion. The weld defect detection method according to claim 1.   3. The weld defect detection method according to claim 1, wherein a change amount of both the amplitude and phase of the induced electromotive force generated in the induction coil with respect to the amplitude and phase of the reference induced electromotive force is obtained.   4. The weld defect according to claim 1, wherein it is determined whether or not a defect exists in the weld by determining whether or not the amount of change is zero. 5. Detection method.   Comparing the amount of change in amplitude and the amount of change in phase, and determining whether or not the magnitudes of both have reversed, it is determined whether or not there is a defect in the weld. The weld defect detection method according to claim 3.   The application of the alternating magnetic field and generation of the induced electromotive force are performed using an electromagnetic induction sensor in which the excitation coil and the induction coil are integrally provided. The weld part defect detection method as described in any one of Claims 1-3.   The weld defect detection according to claim 6, wherein the application of the alternating magnetic field and generation of the induced electromotive force are performed using an electromagnetic induction sensor in which the excitation coil and the induction coil are coaxially wound. Method.   8. The weld defect detection method according to claim 6, wherein application of the AC magnetic field and generation of the induced electromotive force are performed in a state where the electromagnetic induction sensor and the weld are not in contact with each other.   The weld defect detection method according to claim 6 or 7, wherein the application of the alternating magnetic field and generation of the induced electromotive force are performed in a state where the electromagnetic induction sensor and the weld are in contact with each other.   An excitation coil for applying an AC magnetic field to a weld to be detected for defects, an induction coil for generating an induced electromotive force by an AC magnetic field passing through the weld, and the amplitude and phase of the induced electromotive force generated in the induction coil And a detection unit for detecting a defect of the weld by obtaining a change in at least one of the amplitude and phase of the reference induced electromotive force. .   The weld defect detection device according to claim 10, further comprising an AC power supply for supplying an AC current to the exciting coil.   11. The detection unit is configured to obtain a change amount of both the amplitude and phase of the induced electromotive force generated in the induction coil with respect to the amplitude and phase of the reference induced electromotive force. Or the weld defect detection device according to 11.   The detection unit includes a circuit for determining whether or not a defect exists in the weld by determining whether or not the amount of change is zero. The welding part defect detection apparatus of any one of Claims.   The detection unit compares the amount of change in amplitude and the amount of change in phase, and determines whether or not there is a defect in the welded portion by determining whether the magnitude of both is reversed. The weld defect detection device according to claim 12, further comprising a circuit.   The weld defect detection device according to any one of claims 10 to 14, further comprising an electromagnetic induction sensor in which the excitation coil and the induction coil are integrally provided.   The weld defect detection device according to any one of claims 10 to 14, further comprising an electromagnetic induction sensor in which the excitation coil and the induction coil are coaxially wound.   17. The weld defect detection according to claim 15, further comprising a sensor support that holds the electromagnetic induction sensor so that the electromagnetic induction sensor and the weld are in a non-contact state. apparatus.   The welded part defect detection apparatus according to claim 15 or 16, further comprising a sensor support part that holds the electromagnetic induction sensor so that the electromagnetic induction sensor and the welded part are in contact with each other. .

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