JP5078926B2 - Defect detection method - Google Patents

Description

  The present invention relates to a defect detection method, and more specifically, to a technique that eliminates the need for a skin cut that greatly reduces the thickness of a site to be inspected when inspecting creep damage or creep fatigue damage.

  Among pressure-resistant members used in boilers and turbines of thermal power plants and the like, creep damage and creep fatigue damage are likely to occur particularly in regions where the temperature and pressure are high. When such damage occurs, voids are generated in the metal structure, and they merge together to grow and propagate into the crack, leading to destruction. For example, in addition to the main steam pipe and reheat steam pipe, containers such as drums and pipes in the boiler ceiling housing, and other stub pipes that connect the container and the heat transfer panel in the furnace are used for high-temperature steam in the atmosphere outside the furnace. Therefore, oxygen in the atmosphere and the member chemically react to generate an oxide film on the surface of the member. The above-mentioned creep damage and creep fatigue damage also occur in such a member, and in particular, such damage often appears remarkably in a weld heat-affected zone that receives a more complicated temperature history at the time of construction than a base metal or weld metal.

  In crack defect detection technology for detecting such damage, for example, there is a method of performing penetration inspection and magnetic particle inspection after grinding the surface of a metal member in order to remove the oxide film on the surface of the member and accustom the surface. Commonly used. When a crack is detected, the crack occurrence part is skin-cut from the surface and removed within a range in which the necessary minimum thickness of the pressure-resistant member is ensured. In addition, when the necessary minimum wall thickness is interrupted at the stage where cracks are removed by such skin cut processing, welding repair or the like is performed on the corresponding part. As for the skin cut processing, the processing history is managed (for example, see Patent Document 1).

JP 2000-97815 A

  In the conventional crack defect detection technology, the surface of the inspection target part (welding heat affected part, etc.) is ground (= skin cut) in order to remove the oxide film. It tends to reduce the wall thickness. Therefore, as described above, it is necessary to manage the machining allowance up to the necessary minimum thickness required for pressure resistance by recording the grinding depth for each inspection or measuring the remaining thickness. In addition, when the cutting allowance of the corresponding part is reduced, it may be necessary to adopt a higher cost inspection method, or welding repair of the corresponding part may be required. Furthermore, depending on the case, even if the thickness of the base material portion or the weld metal portion remains sufficiently, replacement work for the entire member may be required.

  Accordingly, the present invention has been made in view of the above problems, and a main object of the present invention is to provide a technique that eliminates the need for a skin cut that greatly reduces the thickness of a region to be inspected when inspecting creep damage or creep fatigue damage.

  The defect detection method of the present invention that solves the above problem is a technique for detecting creep damage or creep fatigue damage that is likely to occur in, for example, pressure-resistant members used in boilers and turbines of thermal power plants, etc. This is a method employing a potential difference method for detecting defects in a conductive material.

  The potential difference method is an inspection method for detecting a defect (such as a crack) generated in a conductive material, and is a non-destructive test in which processing such as cutting and cutting is not performed on a site where a defect is suspected. This potential difference method uses the fact that if there is a defect such as a crack in a metal member or the like, a voltage drop occurs due to the current flowing around the defective part when a voltage is applied around the relevant part, and the voltage drop is measured. Then, the size and position of the defect are estimated by analysis.

The defect detection method according to the present invention is a potential difference method for detecting defects in a conductive material. In the potential difference method, welding history information relating to the conductive material is marked or recorded on a recording medium at a corresponding position on the surface of the conductive material. In performing the recording process and the potential difference measurement regarding the conductive material, a first determination step for determining whether the measurement is performed for the conductive material for the first time, based on the presence or absence of information in the welding history, and the result of the first determination When it is found that the potential difference measurement is performed for the conductive material for the first time, the information on the surface of the conductive material or the welding history indicated by the recording medium is read to avoid the heat affected range indicated by the welding history. A first oxide film removing step for removing the oxide film by applying impact or friction with a predetermined strength to the surface of the conductive material, and the potential of the corresponding conductive material in the past as a result of the first determination. When it is found that the measurement is being performed, the second determination for determining the presence or absence of the low melting point glass sealing portion on the surface of the corresponding conductive material is executed, and as a result of the second determination, the low melting point glass sealing portion The second oxide film removing step of removing the low melting point glass by applying a predetermined strength impact or friction to the portion sealed with the low melting point glass on the surface of the conductive material, As a result of the second determination, when there is no low melting point glass sealing portion, the mark on the surface of the conductive material or the welding history information indicated by the recording medium, and the mark on the surface of the conductive material or the recording medium indicate Read the information of the electrode installation position, avoid the heat affected range indicated by the welding history and the place where the oxide film has been removed in the past, and perform the oxide film removal by applying impact or friction of a predetermined strength to the surface of the conductive material. The electrode is brought into contact with the electrode installation position of the conductive material from which the oxide film has been removed by the third oxide film removing step and any one of the first to third oxide film removing steps, and current is applied between the electrodes. And measuring the potential difference, marking the corresponding electrode installation position on the conductive material surface or recording the information on the electrode installation position on the recording medium, and after performing the potential difference measurement and after removing the oxide film And a potential difference measuring step of sealing the electrode installation position with a low-melting glass .

It is a figure which shows process example 1 of the defect detection method of this embodiment. It is a figure which shows the example of a friction apparatus of this embodiment. It is a figure which shows process example 2 of the defect detection method of this embodiment. It is a figure which shows process example 3 of the defect detection method of this embodiment. It is a flowchart which shows the example of a procedure of the defect detection method of this embodiment. It is a figure which shows the example of the electrically-conductive material of this embodiment, and an electrode installation position. It is a figure which shows the example of an analysis result in this embodiment.

--- Actual defect detection method ---
Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a process example 1 of the defect detection method of the present embodiment. As an example of the defect detection target here, a pressure-resistant member 10 made of metal (ie, a conductive material) used in a boiler or turbine of a thermal power plant or the like can be assumed. Further, among the pressure-resistant members 10, the welding heat affected zone 12 existing in the form of a thin film around the weld metal 12 a where defects 11 such as creep damage and creep fatigue damage are likely to occur is illustrated as an inspection target part. . The weld heat affected zone 12 includes a coarse grain region 12b just outside the weld metal 12a and a fine grain region 12c outside the coarse grain region 12b. In addition, the pressure-resistant member 10 (e.g., main steam pipe, reheat steam pipe, drum or boiler container in the boiler ceiling housing, and other stub pipes connecting the container and the heat transfer panel in the furnace) Since the high temperature steam is passed through, oxygen in the atmosphere and the member chemically react, and the oxide film 13 is generated on the member surface.

  Of course, in the defect detection method of the present embodiment, the pressure-resistant member 10 is not limited to a defect detection target, and any member that should detect a defect by applying a potential difference method can be a target. .

  Note that the potential difference method is an inspection method for detecting a defect (such as a crack) generated in a conductive material, and is a nondestructive test in which processing such as cutting and cutting is not performed on a site where a defect is suspected. This potential difference method uses the fact that if there is a defect such as a crack in a metal member or the like, a voltage drop occurs due to the current flowing around the defective part when a voltage is applied around the relevant part, and the voltage drop is measured. Then, the size and position of the defect are estimated by analysis.

  In the defect detection method of the present embodiment, first, the electrode installation position 14 of the pressure-resistant member 10 as the conductive material is subjected to a predetermined strength impact or friction to remove the oxide film 13 on the surface of the electrode installation position. (First step). In removing the oxide film 13, it can be assumed that a striking device 20 that strikes the oxide film 13 at the electrode installation position 14 with a predetermined strength is used. The striking device 20 is, for example, a device in which a casing 21 is provided with a punch 21 that punches a hole having a diameter necessary for abutting the electrode tip, and a spring mechanism 22 that biases the punch 21. When the hitting device 20 is pressed on the electrode installation position 14 and a button 24 attached to the punch 21 via a spring is pressed, the punch 21 that has been held in the housing by the button 24 until then is The spring mechanism 22 extends outward from the housing due to the repulsive force. Then, the tip of the punch 21 collides with the oxide film 13 and penetrates to a fresh portion (meaning a non-oxidized layer) of the pressure-resistant member 10, thereby forming an opening for electrode installation.

  In removing the oxide film 13, the friction device 30 illustrated in FIG. 2 may be used instead of the impact device 20. The friction device 30 includes, for example, a brush 31 and a support 32 to which the brush 31 is attached in order to apply a predetermined strength of friction to the oxide film 13 at the electrode installation position 14, and the brush 31 through the support 32. This is a device in which a spring mechanism 33 for energizing is housed in a housing 34. When the brush 31 of the friction device 30 is brought into contact with the electrode installation position 14 and a button 35 attached to the support body 32 via a spring is pressed, the button 35 has been retained in the casing until then. The support body 32 extends outward from the housing by the repulsive force of the spring mechanism 33. Then, the brush 31 fixed to the front end of the support 32 rubs and scrapes off the oxide film 13 to expose a fresh portion (meaning a non-oxidized layer) of the pressure-resistant member 10. An opening can be formed.

  Thus, the state where the oxide film 13 is removed at the electrode installation position 14 is a state A in FIG. In this state, one oxide film is removed from the electrode installation position 14 of the pressure-resistant member 10. Such an oxide film removal process is repeatedly executed for the number of electrode installation positions 14. In the state B in the figure, a state is shown in which the oxide film removal process relating to a total of four electrode installation positions 14 is performed.

  Thereafter, the electrode is brought into contact with the opening after the oxide film 13 is removed, that is, the electrode installation position 14. As an electrode to be installed, a voltage measuring device 3 is used to measure a voltage value between a current application electrode 2 for applying a current from a power source 1 and a portion to be inspected such as the welding heat affected zone 12. There is an electrode 4 for potential difference measurement. These electrodes are electrically connected to the power source 1 and the voltage measuring device 2 by a conductive wire 5. When the abutting of the electrodes 2 and 4 to the electrode installation position 14 is completed, the current application between the current application electrodes 2 and the potential difference measurement between the potential difference measurement electrodes 3 are executed ( State C in Fig. 1. Second step).

  Subsequently, after the execution of the second step, the electrodes 2, 4 and the like are pulled up from the electrode installation position 14, and the oxide film removal site on the surface of the pressure-resistant member 10 is sealed with the low melting point glass 40. According to this, it is possible to prevent the oxide film from being formed again by leaving the electrode installation position 14 on the surface of the conductive material from which the oxide film has been removed, as it is after the second step.

  The electrodes or the like may be integrated with the striking device 20 (or the friction device 30) in advance. FIG. 3 is a diagram showing a process example 2 of the defect detection method of the present embodiment. In this example, as shown in FIG. 3, the impacting device 20 includes an electrode 25 at the tip of the punch 21 described above, and a conductive wire 26 is connected to the electrode 25. Each striking device 20 is arranged in a plane so as to correspond to each predetermined electrode installation position 14 and is fixed to the frame 27. The frame 27 is, for example, a structure in which a structural material having a predetermined strength is assembled and fixed in a lattice shape, and a holding mechanism (for example, the striking device 20) of the striking device 20 according to the number and positions of the electrode installation positions 14. Equipped with clamps and clips).

  In this case, first, the striking device 20 is attached in order to apply a striking (or friction) with a predetermined strength to the electrode installation position 14 in the pressure-resistant member 10 and to remove the oxide film 13 on the surface of the electrode installation position. On the electrode installation position 14 (state A), the frame body 27 is pressed down on the buttons 24 attached to the punches 21 via springs (the buttons 24 are all linked to each other, and one button is pressed down). Any mechanism that can be used to press all the buttons is preferable). Then, the punch 21 that has been retained in the casing by the button 24 is extended outward from the casing by the repulsive force of the spring mechanism 22. At this time, the tip of the punch 21 collides with the oxide film 13 and penetrates to a fresh portion (meaning a non-oxidized layer) of the pressure-resistant member 10, thereby forming an electrode installation opening.

  Thus, the state where the oxide film 13 is removed at the electrode installation position 14 is a state B in FIG. Thereafter, the punch 21 of the striking device 20 remains in contact with the opening after the oxide film 13 is removed, that is, the electrode installation position 14. In this state, the electrode 25 provided at the tip of the punch 21 is in contact with the opening. Depending on each electrode installation position 14, the electrode 25 becomes the current application electrode 2 or the potential difference measurement electrode 4. The conducting wire 26 of the electrode 25 is electrically connected to the power source 1 and the voltage measuring device 2 through the conducting wire 5. When the contact of the electrode 25 with the electrode installation position 14 is completed, the current application between the current application electrodes 2 and the potential difference measurement between the potential difference measurement electrodes 3 are executed (FIG. 3). State C. Second step).

  Subsequently, after the execution of the second step, the electrode 25 together with the frame body 27 is pulled up from the electrode installation position 14, and the oxide film removal site on the surface of the pressure-resistant member 10 is sealed with the low melting point glass 40. According to this, it is possible to prevent the oxide film from being formed again by leaving the electrode installation position 14 on the surface of the conductive material from which the oxide film has been removed, as it is after the second step.

  If the electrode installation position 14 from which the oxide film has been removed is marked 50 at the corresponding location on the surface of the pressure-resistant member or the third step of recording the information on the electrode installation position 14 on the recording medium is executed. Is preferred. For example, in the example of FIG. 4, on the surface of the pressure-resistant member 10, after execution of the oxide film removal process, a mark 50 indicating that the oxide film has been removed is marked at the edge of the electrode installation position 14 (state A in FIG. 4). . Alternatively, on the interface 61 of the computer 60 on which a predetermined drawing creation application or the like is executed, data input for arranging the mark 50 in association with the electrode installation position 14 on a figure having a size and shape corresponding to the pressure-resistant member 10 The data input here may be stored in the storage device (= recording medium) of the computer 60.

  In such a case, in the first step, the information on the electrode installation position 14 indicated by the mark 50 on the surface of the pressure-resistant member is read, and the portion where the oxide film has been removed in the past is avoided, and the surface of the pressure-resistant member has a predetermined strength. The oxide film may be removed by applying impact or friction (state B in FIG. 4). Alternatively, the data may be read from the storage device of the computer 60 and displayed on the interface 61 to read the information on the electrode installation position 14 from which the oxide film has been removed on the surface of the pressure-resistant member.

  In the example of FIG. 4, the frame body 27 is set on the surface of the pressure-resistant member 10 from above the pressure-resistant member 10 while avoiding the position of the mark 50 and the welding heat affected zone 12 (state B). If the oxide film removal step is executed in this state, the removal process can be performed on the oxide film at the position of the mark 50 and the position where the welding heat affected zone 12 is avoided (state C in FIG. 4). According to this, the process of the oxide film removal (first step), which is originally performed very shallowly in an extremely narrow region (= electrode installation position), is dispersed while avoiding the overlap of the processing positions. The thinning of the material can be further suppressed.

  In addition, you may perform the process of marking the information of the welding history regarding the said pressure | voltage resistant member 10 in the applicable location of the said pressure | voltage resistant member surface, or recording on a recording medium. This is because, as already described, the welded portion becomes a region to be inspected because it receives a more complicated temperature history during construction than the base metal or weld metal. The mark method and the data recording method on the recording medium may be the same as those in the embodiment shown on the basis of FIG. In this case, in the first step, a mark on the pressure-resistant member surface or information on a welding history indicated by the recording medium is read, and a heat affected range indicated by the welding history (eg, a range from a boundary of a welded part to a predetermined distance). The oxide film may be removed by applying impact or friction with a predetermined strength to the surface of the pressure-resistant member. According to this, it is possible to avoid the process of removing the oxide film with respect to a heat-affected range that is easily affected by a decrease in strength due to thinning.

  Alternatively, when the electrode installation position 14 in FIG. 4 is sealed with the low-melting glass after the execution of the second process, the electrode installation position 14 (= sealed with the low-melting glass in the first process after that). The low melting point glass may be removed by hitting or rubbing with a predetermined strength with respect to the stopped portion). After the low melting point glass is removed, the fresh electrode installation position 14 where the oxide film is not formed is exposed. Accordingly, in the subsequent second step, an electrode is brought into contact with the electrode installation position after the low melting point glass is removed, and current application and potential difference measurement between the electrodes are executed. In other words, instead of avoiding the place where the oxide film has been previously removed, only the place where the oxide film has been removed and sealed with the low melting point glass is used as the electrode installation position 14 in a fixed manner. . According to this, once the oxide film has been removed, it is possible to suppress the formation of the oxide film again and to fix the electrode installation position to the sealing position with the low melting point glass, The frequency and location for film removal are not increased unnecessarily. That is, it is possible to suppress an increase in the thinned portion other than the sealed portion with the low melting point glass.

--- Flow example of defect detection method ---
Subsequently, a flow of the defect detection method of the present embodiment will be described. FIG. 5 is a flowchart showing a procedure example of the defect detection method of the present embodiment. In this flow, the details of each process have already been described above, and will be omitted. Here, first, the information of the welding history related to the conductive material is marked at a corresponding location or recorded on a recording medium (s100). Then, when performing the defect detection procedure by the defect detection method of this embodiment, it is determined whether it is the first defect detection for the conductive material to be inspected (s101). This determination may be made by referring to the presence or absence of the mark written on the conductive material and the presence or absence of the corresponding data on the recording medium.

  For example, when it is determined in step s101 that the conductive material to be inspected is the first defect detection process (s101: YES), the welding history information recorded in step s100 is read (s102), and the heat is detected. Stroke or friction with a predetermined strength is applied to the electrode installation position where the influence range is avoided (s103). Then, the electrode is brought into contact with the electrode installation position from which the oxide film has been removed by striking the electrode installation position 14 or the like (s104).

  On the other hand, if it is determined in step s101 that the conductive material to be inspected is not the first defect detection process (s101: NO), it is determined whether there is a portion sealed with low-melting glass on the surface of the conductive material ( s109). If there is no portion sealed with the low melting point glass (s109: NO), the welding history information recorded in step s100 is read (s110). Further, information on the electrode installation position 14 where the oxide film has been removed in the past with respect to the corresponding conductive material is read from a mark on the surface of the conductive material or a recording medium (s111). Then, an impact or friction with a predetermined strength is applied to the location where the oxide film has been removed in the past and the electrode installation position that avoids the heat-affected range (s112). Further, the electrode is brought into contact with the electrode installation position from which the oxide film has been removed by this blow or the like (s104).

  On the other hand, when it is determined in step s109 that there is a portion sealed with the low-melting glass (s109: YES), the low-melting glass is subjected to striking or rubbing with a predetermined strength, and Removal is performed (s113), and as a result, the electrode is brought into contact with the exposed electrode installation position 14 (s114).

  Subsequently, current application and potential difference measurement are performed between the electrodes in contact with the electrode installation position 14 (s105), and then the corresponding electrode installation position is marked at the corresponding position, or the electrode installation position is set on the recording medium. Is recorded (s106). The oxide film removal site is sealed with the low melting point glass 40 (s107). Finally, an analysis based on a potential difference method is performed on the potential difference data measured in step s105 (s108), and the presence of the defect 11 in the conductive material is detected.

--- Specific examples of defect detection targets and detection results ---
Subsequently, the pressure resistant member 10 to which the defect detection method of the present embodiment is actually applied and the defect detection result will be described. FIG. 6 is a diagram showing an example of the conductive material and the electrode installation position of the present embodiment. The pressure-resistant member 10 shown here is a container in the boiler ceiling housing. As a structure, the header 10 includes a header portion 70 that receives the open ends of a plurality of tubes, and a pipe portion 71 that collects and passes the fluid from the pipes that are gathered by the header portion 70. The nozzle part 70 and the pipe part 71 are connected by welding. Therefore, the joint portion between the nozzle portion 70 and the pipe portion 71 is the welding heat affected zone 12. Further, the surface of the nozzle 10 is covered with an oxide film 13.

  In addition, on the surface of the nozzle 10, through the oxide film removal process, there are four current application electrodes 2 of “+1” to “+4” and 4 of “−1” to “−4”. A total of eight books are installed (see FIG. 6). Similarly, a total of three potential difference measuring electrodes 4 from “1” pin to “3” pin are installed (see FIG. 6). As shown in the table in the lower part of FIG. 6, the combination examples for measuring the potential difference measuring electrode 4 are Pair Nos. 1 and 2. That is, the potential difference between the potential difference measuring electrodes 4 of each pair is measured by the voltage measuring device 3.

  In order to verify the defect detection method of the present embodiment, a crack is artificially introduced in advance to the tube holder 10, and a potential difference at a portion sandwiching the artificial crack is measured. A plurality of types of artificial cracks are introduced step by step. The first crack (first stage) is introduced on the second pin of the potential difference measuring electrode 4 and has a depth of 0.1 mm. The second crack (second stage) is obtained by further deepening the crack already introduced as the first crack (first stage) on the second pin of the potential difference measuring electrode 4 by 0.2 mm.

Each time the crack was introduced stepwise, a potential difference was measured by applying a current in each of the following patterns (1) to (4), and the output (potential difference change amount) was summed.
(1) The amount of change in potential difference during current application is measured between the current application electrodes “+1” ← → “−1”.
(2) The amount of change in potential difference during current application is measured between the current application electrodes “+2” ← → “−2”.
(3) The amount of change in potential difference during current application is measured between the current application electrodes “+3” ← → “−3”.
(4) The amount of change in potential difference during current application is measured between the current application electrodes “+4” ← → “−4”.

  Moreover, the FC value obtained by the formula FC = (Bs / As × Ai / Bi−1) × 1000 (ppt) was calculated.

here,
As: Potential difference of Pair A at the start of monitoring.
Bs: Potential difference of the standard test piece at the start of monitoring.
Ai: Pair A potential difference at time i.
Bi: Potential difference of the standard test piece at time i.
As a result of potential difference measurement using a pair of potential difference measurement electrodes straddling artificial cracks at different depths and positions as described above, for example, for Pair1, the first stage: FC = 136.6, increase / decrease 136.6, second stage Eye: Measurement results such as FC = 333.1 and increase / decrease 214.2 were obtained. In addition, regarding the FC value increase / decrease amount among the measurement results, if the data is arranged focusing on the crack introduction site, the correspondence between the FC increase / decrease amount and the crack depth can be seen.

  FIG. 7 is a graph showing the relationship between the crack depth and the FC value increase / decrease amount by analyzing the measurement results as described above. As shown in the graph of FIG. 7, the average value of the FC1 increase / decrease amount of Pair1 and Pair2 obtained for the first stage crack is “80.7”, and the FC of Pair1 and Pair2 obtained for the second stage crack. The average value “150.1” of the value increase / decrease amount, and the average value “230.8” of the FC value increase / decrease amount of Pair1 and Pair2 obtained for the first stage + second stage crack, according to the depth of the corresponding crack When plotted on the graph, the relationship between the crack depth and the FC value increase / decrease amount (also referred to as potential difference change) was almost proportional. After that, if this graph is used as a master curve for defect detection related to the pipe 10 and the result of the potential difference measurement by the potentiometric method is applied to the pressure resistant member similar to the pipe 10, the defect size such as a crack is quantified. It will be possible.

  As described above, according to the present embodiment, by performing the oxide film removal in the inspection for creep damage or creep fatigue damage, it is possible to avoid the execution of skin cut that greatly reduces the thickness of the inspection target portion. Further, it is possible to disperse the oxide film removal (first step), which is originally performed very shallowly in a very narrow region (= electrode installation position), while avoiding overlapping of the processing positions. Can be further suppressed.

  Furthermore, it is possible to perform the oxide film removal process by the impacting device or the friction device as it is after the electrode is arranged at the electrode installation position, and the efficient defect detection method can be executed.

  Further, with respect to the electrode installation position on the surface of the conductive material from which the oxide film has been removed, by performing a sealing process with low-melting glass, the oxide film is generated again by leaving it as it is after the execution of the second step. Can be prevented. In this way, once the oxide film is removed, it is possible to suppress the formation of the oxide film again, and to fix the electrode installation position to the sealing position with the low melting point glass, and to remove the oxide film. The frequency and location are not increased unnecessarily.

  Furthermore, it is possible to avoid the oxide film removal process from being performed on a heat-affected range that is easily affected by strength reduction due to thinning.

  Therefore, according to the present embodiment, when inspecting creep damage or creep fatigue damage, a skin cut that greatly reduces the thickness of the site to be inspected becomes unnecessary.

As mentioned above, although embodiment of this invention was described concretely based on the embodiment, it is not limited to this and can be variously changed in the range which does not deviate from the summary.

DESCRIPTION OF SYMBOLS 1 Power supply 2 Current application electrode 3 Voltage measuring device 4 Potential difference measurement electrodes 5 and 26 Conductor 10 Pressure-resistant member (conductive material)
DESCRIPTION OF SYMBOLS 11 Defect 12 Welding heat affected zone 13 Oxide film 14 Electrode installation position 20 Impact device 21 Punch 22, 33 Spring mechanism 23, 34 Case 24, 35 Button 25 Electrode 27 Frame body 30 Friction device 31 Brush 32 Support body 40 Low melting point glass 50 mark 60 computer 61 interface

Claims (1)

In the potentiometric method for detecting defects in conductive materials,
Welding history recording process for recording information on the welding history related to the conductive material, or recording the recording material on the recording medium or a mark on the relevant portion of the surface of the conductive material
In performing the potential difference measurement for the conductive material, a first determination step of determining whether the measurement is the first time for the corresponding conductive material, based on the presence or absence of information of the welding history,
As a result of the first determination, when it is found that the potential difference measurement is performed for the conductive material for the first time, the mark on the surface of the conductive material or the welding history information indicated by the recording medium is read, and the heat indicated by the welding history A first oxide film removing step of performing an oxide film removal by applying impact or friction of a predetermined strength to the surface of the conductive material while avoiding an influence range;
As a result of the first determination, when it is found that potential difference measurement has been performed in the past for the corresponding conductive material, a second determination for determining the presence or absence of the low melting point glass sealing portion on the surface of the corresponding conductive material is performed. As a result of the second determination, when there is a low melting point glass sealing portion, a low melting point glass is applied by applying a predetermined strength of striking or friction to the portion sealed with the low melting point glass on the surface of the conductive material. Removing a second oxide film,
As a result of the second determination, if there is no low melting point glass sealing location, the mark on the surface of the conductive material or the welding history information indicated by the recording medium, and the mark on the surface of the conductive material or the recording medium are Read the information of the electrode installation position shown, avoid the heat affected range indicated by the welding history and the location where the oxide film has been removed in the past, and apply a predetermined intensity of striking or friction to the surface of the conductive material to remove the oxide film Performing a third oxide film removing step;
The electrode is brought into contact with the electrode installation position of the conductive material from which the oxide film has been removed by any one of the first to third oxide film removal steps, current application and potential difference measurement are performed between the electrodes, and the corresponding electrode is installed. For the position, mark the corresponding position on the surface of the conductive material or record the information of the electrode installation position on the recording medium, and after performing the potential difference measurement, seal the electrode installation position after removing the oxide film with a low melting point glass. A potential difference measurement process to be stopped;
The defect detection method characterized by performing.