JPH07130293A - Non-destructive inspection method for welded member - Google Patents

Abstract

PURPOSE:To provide a non-destructive inspection method for a welded member which can guarantee the welding strength of all numbers without breaking welded members. CONSTITUTION:A four-terminal probe 8 is abutted against the faces of a welded holder 31 and the holder 31 of a frame 32, and the resistance value of the welded zone is measured with a digital microohm meter 3 by constant-current four-terminal measure method. After this, the nugget diameter of the section is computed from the relation between a resistance value sought in advance and a nugget diameter, and based on this nugget diameter, it is judged whether the welding strength is good or bad.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nondestructive inspection method for welding members which can be applied to the manufacturing process of, for example, color selection electrodes for cathode ray tubes and electron guns.

[0002]

2. Description of the Related Art Generally, in the process of manufacturing a color cathode ray tube, spot welding or laser welding is performed on constituent members when assembling a color selection electrode or an electron gun. Conventionally, the welding strength of such a color selection electrode or electron gun has been measured by peeling the welded portion.

[0003]

However, in the case of such a conventional method, since the welded portion was peeled off and the nugget diameter was measured, the constituent members had to be destroyed, resulting in a sampling inspection. We were unable to guarantee the total welding strength. In addition, regarding wire welding of electron guns, since the members are small, conventionally it is only necessary to check the contact state by all the continuity checks, and the welding strength is determined for all electron guns by measuring the nugget diameter. I couldn't.

The present invention has been made in view of the above points of the conventional example, and its purpose is to perform nondestructive inspection of welded members capable of guaranteeing the total welding strength without breaking the welded members. To provide a method.

[0005]

According to the present invention, for example, as shown in FIG. 1, a probe 8 having four terminals is brought into contact with one surface S of the welded members 31 and 32 in the vicinity of the welded portion to measure the resistance value. From the relationship between the resistance value and the nugget diameter obtained in advance for the same member as this member 31, 32,
The nugget diameter is calculated and whether the welding strength is acceptable or not is determined based on the nugget diameter.

[0006]

According to the present invention having such a structure, the resistance values of the welded members 31, 32 in the vicinity of the welded portion are measured, and the resistance value of the same member is determined in advance from the relationship between the resistance value and the nugget diameter. Since the nugget diameter is calculated and the weld strength pass / fail is determined based on the nugget diameter, it is possible to determine the nugget diameter, and thus the weld strength pass / fail, without destroying the welded members 31 and 32.

[0007]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows the configuration of a system for carrying out the method of the present invention. As shown in the figure, this system includes a computer 1 that collects resistance values measured by a method described below and determines acceptance. This computer 1 is a digital micro ohm meter (for example, Tecrad DMO-350) for measuring a resistance value.
Etc.) 3 and interface 2 (eg RS-232 etc.)
Connected by. The computer 1 is also connected by an I / O cable 22 to a sequence controller 23 for controlling the system and a probe switch 5 for switching the probes 8, 15, 18, 21.

The digital micro ohm meter 3 is provided with a measuring cable 4 for connecting the contacts 6 of the probe switching device 5 to each other.
It is connected to 13, 16, and 19. In this case, contact 6
Is connected to the first probe 8 by a measuring cable 7. Further, the contacts 13, 16 and 19 are connected to the second, third and fourth probes 15, 18, 21 by measuring cables 14, 17 and 20, respectively.

The first probe 8 has pins 9 and 12 for supplying a constant current and pins 10 and 11 for measuring a potential difference.
And are provided at equal intervals. Also, although not shown,
The second to fourth probes 15, 18 and 21 are also provided with the constant current pin and the potential difference measuring pin similar to the first probe 8.

Next, the principle of measuring the nugget diameter by the method of this embodiment will be described. FIG. 3A shows a welded state of the frame 32 of the color selection electrode and the holder 31 in the cathode ray tube, and a hatched portion 33 is a welded portion. Here, the holder 31 shown in FIG.
When peeled from 2, the nugget 36 remains as shown in FIG. 3B, and the diameter X of the joint surface between the frame 32 and the nugget 36 becomes the nugget diameter.

FIG. 3C is a view of the nugget 36 seen from above, and the actually measured nugget diameter Z is a value obtained by adding the measured values of the diameter X in the horizontal direction and the diameter Y in the vertical direction and dividing by two. is there.

FIG. 4 shows the holder 31 and the frame 3 described above.
It is a graph which shows the resistance value at the time of welding of No. 2, and a nugget diameter. This graph shows 14 sizes (nugget diameter)
Different materials are prepared, the resistance value is measured by the resistance value measuring system shown in FIG. 1, and the holder 3 is attached as shown in FIGS. 3A and 3B.
1 is peeled off, the nugget diameter Z is measured, and the correlation between the two is graphed.

As can be seen from FIG. 4, the nugget diameter Z
Is smaller, the resistance value is larger, and as the nugget diameter Z is larger, the resistance value is smaller. For example, in the case of the frame 32 and the holder 31 shown in FIG. 3, since the welding strength of the frame 32 and the holder 31 is a standard that can be guaranteed if the nugget diameter is 5 mm or more, the broken line b indicating the nugget diameter of 5 mm or less in FIG. If the resistance value is equal to or lower than the resistance value (the resistance value indicated by the one-dot chain line c) where the solid line a indicating the measured value intersects, the nugget diameter Z can be guaranteed to be 5 mm or more, and the desired welding strength can be obtained. Become.

Next, the operation in the case of making a pass / fail judgment of an actually welded member using the method of this embodiment will be described with reference to FIG. In this case, based on the graph of FIG. 4, the resistance value when the nugget diameter Z is 5 mm is set as the acceptance reference resistance value.

First, when a tube type size selection switch (not shown) is turned on, for example, at 25 inches, the tube type size is positioned at 25 inches (steps 1 and 2). Then, when the positioning of the tube type size is completed, the tube type code is transmitted to the computer (step 3). If the positioning of the pipe type size is not completed due to some trouble, a pipe type size positioning error is displayed (step 18), and the operation is stopped because a trouble occurs (step 19).

After that, an automatic switch (not shown) is turned on (step 4) and the automatic mode operation state is set (step 5). Then, a start switch (not shown) is turned on (step 6), the contact 6 of the probe switch 5 is operated, and the first probe 8 is connected to the digital ohm meter 3 (step 7).

Next, the first probe 8 is moved to the measurement point (near the welded portion), and as shown in FIG.
2 is brought into contact with the measurement surface S of the holder 31 to perform the positioning operation (step 8). Then, when the positioning of the first probe 8 is completed, the resistance value is measured using the first probe 8 and the signal of the measured value is transmitted to the computer 1 (steps 9 to 12). In this case, as shown in FIG. 1, a constant current 34 is passed between the pins 9 and 12, and the potential difference is measured by the pins 10 and 11 located inside these (constant current four-terminal measurement method). According to this method, the contact resistance between the pins 9 to 12 and the measuring surface S can be ignored. Further, since the pin intervals of the probes 8, 15, 18, 21 are unified, it is assumed that there is no measurement error due to the probes.

On the other hand, for some reason, the first probe 8
If the positioning of the first probe 8 is not completed,
The positioning error is displayed (step 20), and the operation is stopped because trouble has occurred (step 21). Further, even if the measurement by the first probe 8 is not completed for some reason, the measurement error of the first probe 8 is displayed (step 22), and the operation is stopped because a trouble occurs (step 23).

In the computer 1, the measured value is compared with the pass reference value calculated based on FIG. 4, and if the pass reference value is equal to or smaller than the pass reference value, the pass is accepted (step 13). . On the other hand, when the measured value is larger than the pass standard value, it is judged as a failure and a defect is displayed on the monitor (step 24).

When the measurement by the first probe 8 is completed in this way, the probe switch 5 is operated to switch to the second probe 15 (step 14), and the above-mentioned measurement operation a is performed.
The measurement operation a2 similar to 1 is performed. Furthermore, the third probe 18 and the fourth probe 21 are sequentially switched (step 1
5, 16), a measurement operation a similar to the measurement operation a1 described above.
3 and a4 are performed. Then, when the measurement by the fourth probe 21 is completed, the measurement for one cycle is completed (step 17), and the start switch is returned to the ON state (step 6).

As described above, in the case of the method of this embodiment,
Since the resistance value of the nugget portion is measured using the digital micro ohm meter 3 and analyzed, the size of the nugget diameter, that is, the welding strength can be determined without breaking (peeling) the part. . As a result, quality assurance by 100% inspection of welded parts becomes possible.

Next, another embodiment of the present invention will be described with reference to FIG. Incidentally, the same reference numerals are given to the portions corresponding to those in the above-mentioned embodiment for explanation.

The present embodiment is used when measuring the resistance value of a wire welded portion of an electron gun of a cathode ray tube. As shown in FIG. 5, in the device according to the present embodiment, the probes 25, 28 obtained by dividing the above-mentioned probes 8, 15, 18, 21 into two are used. In this case, the probe 25 is provided with a pin 26 for constant current and a pin 27 for measuring potential difference. On the other hand, the probe 28 is similarly provided with a pin 29 for measuring a potential difference and a pin 30 for constant current. The probe 25 and the probe 28 are connected to the terminal 24.
In the above, they are electrically connected to each other, and these are further connected to the digital ohmmeter 3 via the above-mentioned probe switching device 5. Further, the probes 25, 28 are fixed by a fixing means (not shown) so that the distance between them is constant.

Then, the fifth grid (G5) 36 of the electron gun and the H connector 37 are formed by using the apparatus having the above structure.
In order to inspect the welding state of, the following resistance value is measured, for example.

First, also in this embodiment, operations such as the above-mentioned tube type size selection are performed. And the probes 25, 2
Position 8 In this case, the pins 26 and 27 of the one probe 25 are brought into contact with the surface of the fifth grid 36,
Connect the pins 29 and 30 of the other probe 28 to the H connector 3
Contact the surface of 7.

After that, a constant current is passed between the constant current pins 26 and 30 of the probes 25 and 28 to measure the potential difference between the potential difference measurement pins 27 and 29.

Further, the measurement data signal is transmitted to the computer 1, and as described above, the pass / fail judgment is made based on the pass standard value preset by actual measurement. Other configurations and operations are the same as those of the above-described embodiment, and detailed description thereof will be omitted.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made. For example, the number of probes for measuring the resistance value can be increased or decreased according to the number of welds to be measured. In this case, if the number of welded portions and the number of probes are equal, the measurement operation can be efficiently performed by switching the connection of the probes as in the first embodiment. This point is the same as in the case of the second embodiment in which the resistance value of the wire welding of the electron gun is measured. Further, in the case of one probe, the probe and the digital micro ohm meter can be directly connected without using the probe switch.

[0030]

As described above, according to the present invention, the resistance value of a welded member in the vicinity of the welded portion is measured, and the resistance value and the nugget diameter of the same member are calculated in advance from the relationship between the members. By calculating the nugget diameter and determining the weld strength pass / fail based on this nugget diameter, the weld strength pass / fail determination can be made without destroying the welded members, and as a result, it is possible to inspect all welded members. Therefore, the reliability of the product, especially the cathode ray tube can be improved. Further, according to the present invention, the pass / fail judgment of welding strength can be performed regardless of spot welding, laser welding, or the like. Further, according to the present invention, it is possible to perform pass / fail judgment of welding strength for all of the wire welding of electron guns, which has been difficult in the past.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a system for carrying out the present invention.

FIG. 2 is a flow chart showing a specific embodiment of the method of the present invention.

FIG. 3 is an explanatory diagram showing a nugget in a welded portion.

FIG. 4 is a graph (actually measured value) showing a relationship between a resistance value and a nugget diameter.

FIG. 5 is a configuration diagram showing another example of a probe.

[Explanation of symbols]

 1 Computer 3 Digital Micro-Ohm Meter 5 Probe Switcher 8 First Probe 15 Second Probe 18 Third Probe 21 Fourth Probe 31 Holder 32 Frame 33 Welded Part 36 Nugget

Claims (1)

[Claims] 1. A surface of a welded member in the vicinity of a welded portion
The resistance value is measured by abutting the probe of the terminal, the nugget diameter of the member is calculated from the relationship between the resistance value and the nugget diameter previously obtained for the same member as the above member, and the welding strength of the nugget diameter is calculated based on the nugget diameter. A nondestructive inspection method for a welded member, characterized by determining pass / fail.