JP2016059930A - Laser welding equipment and laser welding process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide laser welding equipment which can reduce construction period.SOLUTION: A laser welding equipment comprises: an oscillator generating laser beam; a transmission mechanism transmitting the laser beam generated by the oscillator; an irradiation mechanism irradiating the laser beam transmitted through the transmission mechanism to a welding point; a feeding mechanism feeding a weld material to the welding point; a shape measurement mechanism measuring a shape of the weld material after the welding; a verifier inspecting stability of the weld material after the welding; and a control unit controlling the position of the verifier on the basis of the measurement result of the shape measurement mechanism.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser welding apparatus and a laser welding method.

  For example, in-furnace structures and equipment of a nuclear power plant may cause defects such as stress corrosion cracking when used for a long period of time. When a defect occurs, measures are taken such as replacing the entire structure or attaching an auxiliary metal fitting.

  Moreover, the method of repairing by the laser welding is proposed as a defect repairing method of the valve seat overlay construction part of a steam valve. In this method, a welding material (wax) is provided in the defective portion of the valve seat overlay construction portion of the steam valve, a shield plate is provided so that the defective portion becomes an inert gas atmosphere, and an inert gas is provided near the defective portion. Diffusion brazing is performed in which the welding material penetrates into the defect by irradiating and heating the laser beam while spraying.

  In the defect repairing method by diffusion brazing described above, there is a step corresponding to placing the welding material in the repaired part. However, for example, in the repair of defects in a nuclear reactor, this step corresponding to the placing is not desirable.

  Moreover, when repairing the reactor internal structure by laser welding, it is necessary to inspect the soundness of the welded portion after the repair. Ultrasonic flaw inspection, eddy current flaw inspection, etc. are used as inspection methods, but inspection is performed after the surface of the weld is processed, so if an abnormality is detected in the weld, it will be re-worked and the construction period will be prolonged. It is a factor.

Japanese Patent No. 4284052

  As described above, the conventional technique has a problem that it takes time to repair defects by laser welding, and the construction period tends to be prolonged. In addition, when laser welding is performed by inserting instead of placing, there is a problem that it is difficult to keep the welding state in a good state.

  The present invention has been made in response to the above-described conventional circumstances, and an object thereof is to provide a laser welding apparatus and a laser welding method capable of shortening the work period.

  One aspect of the laser welding apparatus of the present invention includes an oscillator that generates laser light, a transmission mechanism that transmits the laser light generated by the oscillator, and an irradiation mechanism that irradiates the welding spot with the laser light transmitted through the transmission mechanism. A supply mechanism for supplying the welding material to the welding location, a shape measuring mechanism for measuring the shape of the welded material after welding, an inspection mechanism for inspecting the soundness of the welded material after welding, and the shape And a control unit that controls the position of the inspection mechanism based on the measurement result of the measurement mechanism.

  According to one aspect of the laser welding method of the present invention, a welding part is irradiated with a laser beam and heated, and a welding material supply mechanism supplies a welding material to the heated welding part to melt the welding material. The step of welding, the step of measuring the shape of the welded material after welding by the shape measuring mechanism, the step of adjusting the position of the inspection mechanism based on the shape measurement result by the shape measuring mechanism, and the position adjusted And a step of inspecting the soundness of the welded material after the welding by an inspection mechanism.

  According to the present invention, the construction period can be shortened.

The figure which shows schematic structure of the laser welding apparatus which concerns on one Embodiment of this invention. The figure which shows the structure of an example of a shape measurement mechanism. The figure which shows the example of energy distribution of a laser beam. The flowchart which shows the process of welding. The figure for demonstrating the example of the detection signal obtained by eddy current flaw detection. The figure for demonstrating the example of the detection signal of the eddy current flaw detection sensor of a square wave drive. The figure for demonstrating the relationship between an attenuation coefficient and thickness. The figure for demonstrating the method of making the shape of a repair material flatter. The figure for demonstrating the case where defect repair is performed by remote control.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 schematically shows a schematic configuration of a laser welding apparatus 100 according to an embodiment of the present invention. In order to prevent the defect 102 from progressing with respect to the defect (crack) 102 generated in the repair target 101 made of a metal member, it is effective to block it from the surrounding environment. In the embodiment shown in FIG. 1, a case where overlay welding is performed on the defect 102 by the laser welding apparatus 100 is shown as a method for interrupting the environment.

  The laser welding apparatus 100 includes an oscillator 103 for generating a laser beam 104, a transmission mechanism 105 for transmitting the laser beam 104, and an irradiation head 130 disposed at a repair site. The irradiation head 130 includes a casing 131. The casing 131 includes a container-like structure having an opening on the lower side in FIG. 1, and an environment for isolating the repair site and its periphery from the outside. A shielding mechanism 118 is provided.

  In the housing 131 and the environment shielding mechanism 118, the irradiation mechanism 106 for irradiating the welding part with the laser beam 104 transmitted by the transmission mechanism 105, and the welding material (repair material) 112 for supplying the welding part to the welding part. And a shape measuring mechanism 110 for measuring the shape of the welded material (weld bead) 116 after welding welded to the welded portion. In addition, an inspection mechanism 117 supported by a fixed arm 121 is disposed on the outer side of the housing 131 (left side in FIG. 1). The inspection mechanism 117 is for detecting abnormalities such as blow holes and poor fusion of the welding material 116 after welding.

  Further, the laser welding apparatus 100 includes a control unit 150 including a computer or the like. The control unit 150 comprehensively controls the operations of the oscillator 103, the irradiation mechanism 106, the shape measurement mechanism 110, the supply mechanism 113, the inspection mechanism 117, and the like (the entire operation of the laser welding apparatus 100), and the shape measurement mechanism. A detection signal from 110 and a detection signal from the inspection mechanism 117 are input.

  For example, an optical fiber can be used as the transmission mechanism 105. Laser light 104 generated from the oscillator 103 is transmitted to the irradiation mechanism 106 through the transmission mechanism 105. Inside the irradiation mechanism 106, the laser beam 104 passes through the condenser lens 107, and then the welding laser beam 109 is irradiated to the welding location by the branch lens 108 and the shape measurement laser beam 111 sent to the shape measurement mechanism 110. It is divided into.

  The welding material 112 is supplied to the welding site by the supply mechanism 113. In the present embodiment, the welding material 112 has a wire shape and is wound around the wire supply source 114 in a reel shape. The wire-shaped welding material 112 is supplied from the wire supply source 114 to the welding site through the cylindrical welding material heating mechanism 115 by a power source (not shown) such as a motor drive. The welding material heating mechanism 115 includes heating means (not shown), and the welding material 112 is supplied to a welding location in a state where the temperature is raised to a predetermined temperature in the process of passing through the welding material heating mechanism 115. As the heating mechanism, Joule heating by energization, laser heating, induction heating, or the like can be used.

  Inside the supply mechanism 113, the wire supply source 114 is movable in the xyz direction by a drive mechanism (not shown), and the welding material heating mechanism 115 is rotatable in the θ direction by a drive mechanism (not shown). . As a result, the supply mechanism 113 can adjust the supply position of the welding material 112 to a desired position.

  In the present embodiment, the shape measuring mechanism 110 is configured by a laser displacement meter, and laser light is used as a measurement medium. The shape measuring laser beam 111 branched from the welding laser beam 109 by the branch lens 108 passes through the inside of the shape measuring mechanism 110 and is irradiated to the welding material 116 after welding. And the height of the welding material 116 after welding is detected by detecting the reflected light with the shape measuring mechanism 110. In addition, the shape measuring mechanism 110 may be configured to perform measurement at one point in the central portion of the welding material 116 after welding, or as a configuration to perform measurement at a plurality of points in the y direction (width direction of the weld bead) in FIG. Also good. When the measurement is performed at a plurality of points, when the welding material is unevenly distributed in the y direction, the unevenly distributed state can be detected.

  The shape measuring mechanism 110 is not limited to the laser displacement meter described above, and any other sensor can be used as long as it can measure the shape of the welded material (weld bead) 116 after welding. FIG. 2 shows a configuration example when a contact sensor is used as the shape measuring mechanism 110. In this case, the shape of the welding material 116 after welding is measured by the contact 201 directly contacting the welding material 116 after welding. For example, the contact point with the welding material 116 after welding is obtained by using the surface of the contactor 201 as a contact point detection sensor. A buffer mechanism 202 is provided so that the contact 201 is not damaged by contact with the welding material 116 after welding. The contactor 201 is prevented from being damaged by the buffer mechanism 202 rotating in the θ direction. The cylinder 203 absorbs the displacement in the z direction of the contact sensor support mechanism 204. Finally, the shape of the welding material 116 after welding is calculated from the z-direction absorption amount of the cylinder 203, the total length of the contact sensor support mechanism 204, the absorption angle θ of the buffer mechanism 202, and the contact point coordinates of the contactor 201.

  When the shape of the welded material 116 after welding measured by the shape measuring mechanism 110 is different from a predetermined reference shape of the welded material 116 after welding beyond an allowable range, the control unit 150 may At least one of the irradiation state of the welding laser beam 109 and the supply state of the welding material 112 is adjusted so that the shape of the welding material 116 becomes the reference shape. The irradiation state of the welding laser beam 109 is adjusted by changing the output of the laser beam 104 or changing the work distance that is the distance from the branch lens 108 to the welding location. Further, the supply state of the welding material 112 is adjusted by changing the supply amount, the heating temperature, the supply angle, the supply position, and the like of the welding material 112 by the supply mechanism 113. As a result, the welding state can be kept in a good state even in welding performed by soldering.

  As described above, the laser welding apparatus 100 of the present embodiment includes the environment shielding mechanism 118 that shields the atmosphere around the welding location from the surroundings. The environmental shielding mechanism 118 is provided with a gas supply mechanism 133 for supplying an inert gas 119 and the like for preventing oxidation therein, and the atmosphere of the environmental shielding mechanism 118 is set to an inert gas 119 atmosphere. it can. The inert gas 119 introduced into the environment shielding mechanism 118 is released to the outside through the gap 120 between the environment shielding mechanism 118 and the object to be repaired 101 to prevent water and outside air from entering the environment shielding mechanism 118. It can be done.

  As the laser beam 104, as shown in FIG. 3B, it is desirable to use a laser beam (top hat type laser beam) having a uniform energy distribution. As a result, it is possible to prevent the energy from concentrating at a certain point of the welded portion and overheating, or the generation of a low energy portion and insufficient heating. Furthermore, by heating the welding material 112 in advance, the effect of spreading the welding material 112 uniformly over the welded portion heated by the welding laser beam 109 can be obtained. Therefore, as compared with the case of using a Gaussian laser beam as shown in FIG. 3A, it is possible to perform overlay welding with the same oscillation output and wider. In this case, a direct diode laser can be used as the oscillator 103.

  The inspection mechanism 117 is used for abnormality detection (soundness inspection) when a blow hole or poor fusion occurs in the welded material 116 after welding. In the present embodiment, an example in which an eddy current flaw detection sensor 123 is used as a sensor of the inspection mechanism 117 is shown. When the inspection is performed by the eddy current flaw detection sensor 123, it is necessary to dispose the eddy current flaw detection sensor 123 close to the welding material 116 after welding. Therefore, the inspection is performed with the eddy current flaw detection sensor 123 held by the movable arm 122 or the like.

  In the present embodiment, when the inspection by the eddy current flaw detection sensor 123 is performed, the eddy current flaw detection sensor is controlled by controlling the driving of the movable arm 122 based on the shape of the welded material 116 after welding measured by the shape measurement mechanism 110. 123 is adjusted. As a result, damage due to contact between the eddy current flaw detection sensor 123 and the welded material 116 after welding can be prevented, and the eddy current flaw detection sensor 123 can be arranged substantially perpendicular to the inspection surface to perform high-precision inspection. it can.

  The laser welding process in this embodiment is shown in the flowchart of FIG. As shown in FIG. 4, first, welding is performed (step 601), and then the shape of the welded material 116 after welding is measured by the shape measuring mechanism 110 (step 602). Then, the position of the inspection mechanism 117 is adjusted based on the shape measurement result (step 603), and the soundness of the welded material 116 after welding is inspected (step 604).

  If the welded material 116 after welding is sound as a result of the soundness inspection, the process is terminated. On the other hand, when abnormalities such as blow holes and poor fusion are found and the welding material 116 after welding is not healthy, the welding is performed again (steps 605 and 606). And when welding is performed again, the process from the said process 602 is repeated.

  Here, in the inspection result of the eddy current flaw detection sensor 123, the noise from the surface shape of the welded material 116 after welding is shown in the graph of FIG. 5A where the vertical axis represents the detection voltage and the horizontal axis represents time. It is assumed that 401 may occur. As a method for easily determining the signal 402 due to the abnormality inside the welding material 116 after welding, there is a method in which a threshold value 403 is provided in the signal and a signal exceeding the threshold value 403 is determined as abnormal.

  However, as shown in FIG. 5A, when the noise 401 due to the surface shape of the welding material 116 after welding exceeds a threshold value, it leads to erroneous determination of abnormality. Therefore, the noise 401 generated by eddy current flaw detection is predicted in advance from the shape of the welded material 116 after welding measured by the shape measuring mechanism 110, and the noise is removed from the detection signal. As a result, a detection signal that can easily determine the signal 404 due to abnormality can be obtained as shown in the graph of FIG. 5B where the vertical axis represents the detection voltage and the horizontal axis represents time.

  Further, by driving the eddy current flaw detection sensor 123, which is normally driven by a sine wave, with a rectangular current (for example, a rectangular pulse current), an eddy current that is transiently attenuated is generated inside the welding material 116 after welding. . The decay rate of the transient eddy current is determined by the thickness of the metal where the eddy current is generated. That is, as shown in the graph of FIG. 6 where the vertical axis represents the detection voltage and the horizontal axis represents time, the attenuation decreases as the metal thickness increases. Therefore, as shown in the graph of FIG. 7 in which the vertical axis represents the attenuation coefficient and the horizontal axis represents the thickness, the relationship between the attenuation coefficient of the attenuation curve 501 and the thickness of the welded material 116 after welding is obtained, and the eddy current flaw detection sensor is obtained. By detecting the decay time of the eddy current by 123, the thickness of the welding material 116 after welding can be obtained.

  In addition, since it is possible to avoid interference at the time of signal detection by making the frequency of the sine wave of the normal drive and the frequency of the odd-numbered harmonic component of the fundamental wave of the rectangular wave different, one eddy current flaw detection is possible. The sensor 123 can detect an abnormality inside the welding material 116 after welding and measure its thickness.

  As described above, in this embodiment, by using the inspection mechanism 117, it is possible to detect a defect in the welding state at an early stage after performing welding, and re-welding can be performed. Can be reduced. Moreover, since the shape measuring mechanism 110 measures the shape of the welded material 116 after welding and adjusts the position of the inspection mechanism 117 to perform the inspection, the inspection can be performed with high accuracy.

  When no abnormality is detected in the welded material 116 after welding, when performing multi-layer welding, the second and subsequent layers are welded. In this case, the supply amount and supply position of the welding material 112 in the second and subsequent layers are determined from the shape measurement result and thickness measurement result in the welding material 116a after the first layer welding, for example, the second layer welding shown in FIG. By adjusting so that it becomes the later welding material 116b, the shape after welding in multiple layers can be flattened. That is, the welding material 112 is supplied between the welding materials 116a after the first layer welding, and the supply amount of the welding material 112 is set so that the height of the welding material 116b after the second layer welding is the first layer. It adjusts so that the height of the welding material 116a after welding may not be exceeded.

  In the laser welding apparatus 100 of the present embodiment, the irradiation mechanism 106, the supply mechanism 113, the shape measuring mechanism 110, the inspection mechanism 117, and the environment shielding mechanism 118 are gripped by a scanning mechanism (not shown) and scan around the repaired portion of the repair target 101. . Therefore, as shown in FIG. 9, repair can be performed remotely on the repair target 101 that is remote from the oscillator 103.

  As described above, according to the present embodiment, the time required for defect repair and the like can be shortened, the work period can be shortened, and the welded state can be maintained in a good state.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 100 ... Laser welding apparatus, 101 ... Repair object, 102 ... Defect, 103 ... Laser oscillator, 104 ... Laser beam, 105 ... Laser beam transmission mechanism, 106 ... Irradiation mechanism, 107 ... Condensing lens , 108 …… branching lens, 109 …… welding laser beam, 110 …… shape measuring mechanism, 111 …… shape measuring laser beam, 112 …… welding material (repair material), 113 …… supply mechanism, 114 …… wire supply 115 ... Welding material heating mechanism, 116 ... Welding material after welding (weld bead), 117 ... Inspection mechanism, 118 ... Environment shielding mechanism, 119 ... Inert gas, 120 ... Gap, 121 ... ... fixed arm, 122 ... movable arm, 123 ... eddy current flaw sensor, 130 ... irradiation head, 131 ... housing, 133 ... gas supply mechanism, 150 ... control unit.

Claims (9)

An oscillator that generates laser light;
A transmission mechanism for transmitting laser light generated by the oscillator;
An irradiation mechanism for irradiating a welding spot with laser light transmitted through the transmission mechanism;
A supply mechanism for supplying a welding material to the welding point;
A shape measuring mechanism for measuring the shape of the welding material after welding;
An inspection mechanism for inspecting the soundness of the welding material after the welding;
Based on the measurement result by the shape measurement mechanism, a control unit that controls the position of the inspection mechanism;
A laser welding apparatus comprising:   The laser welding apparatus according to claim 1, wherein the control unit controls a supply state of the welding material by the supply mechanism based on a measurement result by the shape measurement mechanism.   3. The laser welding apparatus according to claim 1, wherein the control unit controls an irradiation state of the laser light based on a measurement result by the shape measurement mechanism.   The said control part removes the noise signal which generate | occur | produces with the surface shape of the welding material after the said welding from the inspection signal obtained by the said inspection mechanism based on the measurement result by the said shape measurement mechanism. The laser welding apparatus of any one of 1-3.   The laser welding apparatus according to any one of claims 1 to 4, further comprising a heating mechanism that preheats the welding material before the welding material is supplied to the welding location.   The laser welding apparatus according to claim 1, wherein the inspection mechanism includes an eddy current flaw detection sensor.   The control unit supplies a rectangular current to the eddy current flaw detection sensor, measures the decay rate of eddy current generated in the weld material after welding, and determines the thickness of the weld material after welding obtained in advance. The laser welding apparatus according to claim 6, wherein the thickness of the welding material after the welding is obtained from a relationship between the eddy current and the attenuation coefficient of the eddy current.   The control unit supplies the welding material in the second and subsequent layers so as to flatten the shape of the welding material after welding after multilayer welding from the obtained thickness of the welding material after welding. The laser welding apparatus according to claim 7, wherein the supply position is adjusted. Irradiating a laser beam to the weld and heating it;
A step of supplying a welding material to the heated welded portion by a welding material supply mechanism to melt and weld the welding material;
A step of measuring the shape of the welded material after welding by the shape measuring mechanism;
Adjusting the position of the inspection mechanism based on the shape measurement result by the shape measurement mechanism;
A step of inspecting the soundness of the welded material after the welding by the inspection mechanism adjusted in position;
A laser welding method comprising:

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