JPH03233352A - Inspecting method for spot weld zone - Google Patents

Abstract

PURPOSE:To make decision processing as to whether a nugget part or not in a short period of time by comparing the height of the reflected waves in the time from the surface waves preset at every slight scanning displacement and the reference value of the height of the reflected waves in the set time. CONSTITUTION:The height of the reflected waves in the time from the surface waves preset at every slight scanning displacement is determined at the time of scanning the weld zone 6 including the nugget part 3 of a spot weld zone and a corona bond part 4 around this part. The attenuation of the multiple reflected waves is faster in the nugget part 3 than in the corona bond part 4 if the nugget part 3 and the corona bond part 4 are compared. The height of the reflected waves and the reference value of the height of the reflected waves in the set time are, thereupon, compared and the case in which the determined height of the reflected waves is smaller than the reference value is decided as to be the nugget part 3 and the case in which the height is larger than the reference value is determined as the corona bond part 4. The scanning displacement quantity in the section decided to be the nugget part 3 is determined as a nugget diameter. The need for computing the degree of attenuation of the multiple reflected waves at every slight scanning is eliminated in this way and the decision processing as to whether the nugget part or not is executed in a shorter period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for inspecting a spot weld, and more particularly to a method for non-destructively inspecting a spot weld using ultrasonic waves.

[Prior Art] In spot welding, which is a type of lap resistance welding, when welding is performed normally, a part of the upper plate and a part of the lower plate are separated at the overlap welding part between the upper plate and the lower plate. It melts and solidifies into one piece, and a melted-resolidified part with a cross section called a nugget is formed in that part. The diameter of this nugget has a strong correlation with the welding strength, and the lower limit of the nugget diameter has traditionally been controlled as a control item for spot welding. That is, the diameter of the nugget is detected, and if the diameter is smaller than the predetermined lower limit of 1 round, the welding strength is determined to be insufficient and the weld is determined to be defective, and if the diameter of the nugget is equal to or greater than the lower limit, it is determined to be acceptable.

In order to carry out such management, it is necessary to detect the nugget diameter, but a conventional method for non-destructively detecting the nugget diameter is to use ultrasonic waves and detect the reflected waves. There is.

A typical example thereof is the method disclosed in Japanese Patent Laid-Open No. 119453/1983.

The method described in this publication involves injecting ultrasonic waves from an ultrasonic probe into the plate from the upper plate surface so as to cross the weld on the surface near the spot weld, and capturing reflected waves at every minute scanning displacement. The diameter of the welded part including the nugget forming part is measured using the difference in the thickness (distance) through which ultrasonic longitudinal waves pass between the welded part including the nugget forming part and the non-welded part. In other words, in the non-welded part, the upper plate and the lower plate are not joined, so the reflected wave of the incident ultrasonic wave becomes a reflected wave from the bottom of the upper plate, while in the welded part, which includes the nugget formation part, the upper plate Since the upper plate and the lower plate are integrally joined, there is no reflected wave from the bottom of the upper plate, but a reflected wave from the bottom of the lower plate occurs. Therefore, there is a difference in ultrasonic propagation time between the non-welded part and the welded part by a thickness corresponding to approximately twice the thickness of the lower plate. Therefore, in the proposed method, the first reflected wave of the multiple reflected waves from the bottom of the upper plate is detected while scanning the ultrasonic probe across the weld, and the first reflected wave from the bottom of the upper plate is detected. The scanning distance from the position where the first reflected wave from the bottom surface of the upper plate disappears to the position where the first reflected wave from the bottom surface of the upper plate is generated is measured as the diameter of the welded portion. Then, treat the diameter of this welded part as the diameter of Nagut 1,
We judge whether spot welding is successful or not based on its size.

In the welded area in spot welding, the area around the nugget where part of the upper plate and part of the lower plate are melted together and resolidified does not immediately become a non-welded area, but is normally shown in Figure 3. As shown in FIG. 2, there is a portion 4 in which the upper plate 1 and the lower plate 2 are solid-phase bonded around the nugget portion 3, that is, a portion generally referred to as a ronabond portion 4, and the corona bond portion 4 is surrounded by is the non-welded part 5. That is, the welded portion 6 where the upper plate 1 and the lower plate 2 are joined together is formed by the nugget portion 3 and the corona bond portion 4 around it. Here, when an ultrasonic wave is incident on the corona bond part 4, no reflected wave is generated from the bottom surface of the upper plate as in the nugget part 3, so the method of the above publication is actually used to measure the ultrasonic wave. Corona bond diameter [)C instead of nugget diameter [)N]
It is. That is, the corona bond diameter DC, which is slightly larger than the nugget diameter DN, is used to determine the quality of spot welding.

In this way, in the above method, the corona bond diameter is actually measured which is larger than the nugget diameter, and therefore, in an inspection that controls the lower limit slope of the nugget diameter, the nugget diameter must meet the lower limit value for pass/fail judgment. There is a danger that even defective items that have not been tested will be judged as acceptable. In other words, the bonding strength of the corona bond part is much lower than that of the nugget part, so
Even if the corona bond diameter is large, sufficient welding strength cannot be obtained if the nugget diameter is small, but even in such a case, there was a risk that the above method would be judged as acceptable.

Therefore, when inspecting spot welds using ultrasonic waves, the present applicant has previously proposed a method that distinguishes between nuggets and corona bond parts and accurately measures the nugget diameter ( (Japanese Patent Application No. 63-238568).

This method calculates the degree of attenuation of the reflected waves when scanning a welded part that includes the nugget and the surrounding corona bond, and then determines the nugget and corona bond based on the difference in attenuation. The amount of scanning displacement at the portion determined to be the nugget diameter is determined as the nugget diameter.

[Problems to be Solved by the Invention] However, in the above method, since the calculation of the degree of attenuation of the reflected wave is complicated, there are problems in that the determination process takes time and the cost of the apparatus increases. This is because complicated calculation processing of the degree of attenuation of multiple reflected waves is required for each minute scanning displacement of the ultrasonic probe, and a device with high calculation processing capacity is required.

The present invention focuses on the above-mentioned problem, eliminates the complicated calculation process of the degree of attenuation of multiple reflected waves for each minute scanning displacement, and realizes an inexpensive inspection device that can perform judgment processing in a short time. The purpose is to provide a method for inspecting spora [・weld parts] that can be detected.

[Means for Solving the Problems] A method for inspecting a spot weld according to the present invention that meets this objective includes scanning an ultrasonic probe across the surface of the spot weld, In a method of capturing ultrasonic reflected waves for each minute scanning displacement and inspecting a spot weld based on the reflected waves, the weld includes the spora 1 to the nugget part of the weld and the surrounding corona bond part. When scanning, calculate the height of the reflected wave at a preset time from the surface wave for each minute scanning displacement, compare the height of the reflected wave with a reference value of the height of the reflected wave at the set time, If the height of the reflected wave determined is smaller than the reference value, it is determined to be a nugget part, and if it is larger than the reference value, it is determined to be a corona bond part, and the amount of scanning displacement in the part determined to be the nugget part is determined. It consists of a method of determining the diameter as the diameter.

[Function] In the spot weld inspection method configured as described above, the welded portion including the nugget portion of the spot weld and the surrounding corona bond portion is scanned by an ultrasonic probe. When the ultrasonic probe is scanned over the surface of the welded part including the nugget part and the corona bond part, the multiple reflected waves for each minute scanning displacement are generated by Caused by reflection.

Comparing the nugget part and the corona bond part, the multiple reflected waves attenuate faster in the nugget part than in the corona bond part.

This is because the nugget part is a metal whose structure is mainly composed of dendrites that have been melted and resolidified, whereas the corona bond part is only solid-phase bonded, so there is no significant change in the structure, and it is normalized. It is a metal whose structure is mainly based on state, and this difference in structure results in attenuation between the two.

In the present invention, the height of the attenuated reflected wave is determined for each minute scanning displacement, and the height of this reflected wave is compared with the reference normal. Here, if the height of the reflected wave is smaller than the reference value,
It is determined to be a nugget portion, and conversely, if the height of the reflected wave is greater than a reference value, it is determined to be a corona bond portion. In other words, whereas in the past, the degree of attenuation of the reflected wave was used as the reference value, in the present invention, the height of the reflected wave at a preset time is used as the reference value, and based on this, it is determined whether it is the nugget part or the corona bond part. A determination will be made.

Therefore, it becomes unnecessary to calculate the degree of attenuation of multiple reflected waves for each minute scanning displacement as in the conventional method, and it is possible to perform the process of determining whether or not there is a nugget portion in a short time.

[Example] Below, a preferred example of the spot weld inspection method according to the present invention will be described with reference to the drawings.

First, the inspection principle of the present invention will be explained.

As shown in FIG. 4, an ultrasonic probe is applied to the surface near the weld 6 so as to cross the center of the weld 6 where the upper plate 1 and the lower plate 2 are overlapped and spot welded. The sensor 7 scans in a straight line. That is, the ultrasonic probe 7 is
Non-welded part 5 where upper plate] and lower plate 2 are not joined together
From the area ■ of the corona bond part 4 of the welding part 6 to the area ■ of the nugget part 3 and again to the area IV of the corona bond part 4
, and exits to the region V of the non-welded portion 5. In this process, reflected waves of the ultrasonic waves emitted from the ultrasonic probe 7 are captured by the ultrasonic probe 7 at every minute scanning displacement.

The received waveform for each minute scanning displacement in each region 1 to V is
As shown in the figure. In FIG. 5, S is a surface wave, BH to B are reflected waves from the bottom surface 1A of the upper plate 1, and B2.1 to B2.3 are reflected waves from the bottom surface 2A of the lower plate 2.

As mentioned above, in the areas ■ and ■ of the non-welded portion 5,
The reflected wave is a reflected wave from the bottom surface IA of the upper plate 1, and the area of the welded part 6 including the corona bond part 4 and the nugget part 3 is
, ■, The reflected waves at IV are reflected waves from the bottom surface 2A of the lower plate 2. Therefore, the ultrasonic propagation distance until each reflected wave is received is approximately twice the thickness of the lower plate 2 in the non-welded part 5 area work, ■ and the welded part 6 areas ■, ■, IV. Because of this difference, there will be a large difference in the spacing between multiple reflected waves.

Therefore, if the area of the non-welded area 5 is ■, then around the time when the first reflected wave B Depending on the presence or absence of reflected waves in the vicinity, it is possible to determine whether the regions (1) and (2) of the non-welded portion 5 or the regions (2) to IV of the welded portion 6 are present.

In other words, the non-welded portion 5 and the welded portion 6 can be determined based on the presence or absence of the first reflected wave BH from the bottom surface IA of the upper plate 1. Specifically, multiple reflections are captured for each minute scanning displacement △× in the scanning process of the ultrasonic probe.
The first one from the bottom surface IA of the upper plate 1 for each minute scanning displacement △X.
The second reflected wave B! The boundary position between the welded portion 6 and the non-welded portion 5 is determined.

In the case of the present invention, the following measurements are roughly performed. The section in which it was determined that there is no first reflected wave 3N from the bottom surface 1A of the upper plate 1 as described above, that is, the area ■ to I of the welding part 6 including the nugget part 3 and the corona bond part 4
In the section determined to be V, apart from game 1 to distinguish between welded and non-welded parts as shown in
Surface wave S is used to distinguish between the nugget part and the corona bond part.
and another gate. Then, focusing on the first reflected wave BH from the bottom surface of the upper plate 1 that occurs in regions I and V of the non-welded part 5, the first reflected wave BH from the bottom surface of the upper plate 1 is generated. A gate GA of a predetermined level is set in a period 1 ( ) near the timing, and the height of the reflected wave exceeding the gate level in the period to is peak-held and used as the gate output.

Here, in the areas ■ and ■ of the non-welded part 5, as already mentioned, the first reflected wave 3H from the bottom surface of the upper plate exists, and its wave height value is higher than a certain level. , if the ultrasonic probe 7 is located in the region ■, game 1
You will get the output to . On the other hand, since there is no reflected wave from the bottom surface of the upper plate 1 in areas (1), (2), and (IV) of the welding part 6 including the corona bond part 4 and the nugget part 3, no gate output is obtained. Therefore, if scanning is performed from area (2) or area (V) toward the center of the recess, gate output is generated at first, but gate output stops occurring from a certain position, and that position is the outer edge boundary position of welded part 6. It will be determined that

On the other hand, in the areas ■, ■, and IV of the welding part 6, a gate GS of a predetermined level is set at a period tO near the timing at which the surface wave S reflected from the surface of the upper plate 1 is generated, and the surface wave exceeding the gate level The height of is peak held and the gate output is P. Also, focusing on the reflected wave B2-111 (m: integer) from the bottom surface 2A of the lower plate 2, 32-m
A predetermined level of G1-GB is set in a period to near the timing at which P is generated, and the height of the reflected wave that exceeds the gate level is held at its peak during that period to, and is used as the gate output P2 complement.

Here, in the areas ■, ■, and IV of the welding part 6, the gate output P of the surface wave S is not constant and varies slightly depending on the contact state between the surface of the upper plate 1 and the ultrasonic probe 7. However, it is not accurate enough to compare the magnitude of the attenuation using the gate output P6. Therefore, as shown in the following equation, if the difference ΔP between the preset height pos of the surface wave S and the measured gate output Pt is corrected, the degree of attenuation becomes more accurate.

△P<r = Pos - P lamp In addition, the gate output P of the m-th reflected wave B from the bottom surface 2A of the lower plate 2 is corrected by △P by the variation of the surface wave S, and the gate output Pζ2-111) H is P, Shrine) H = P2 edition + ΔP
It becomes 8°. Looking at the magnitude of this gate output correction value p(2-111)H, in the corona bond part 4 and the nugget part 3,
Since a difference in the height of multiple reflected waves occurs due to the difference in metal structure, the gate output of the nugget portion 3 becomes smaller than the gate output of the corona bond portion 4. Therefore, if a reference value (threshold 1) is provided for the gate output P2-II+ of this m-th reflected wave B, it is possible to determine whether the scanning position at which the reflected wave height is being captured is the nugget portion 3 or the corona bond portion 4. can be determined.

As shown in Fig. 7, the surface wave S
The difference △P, cr between the height p 24n of the m-th reflected wave B from the surface wave S and the predetermined value of the wave height of the surface wave S is calculated, and the m-th reflection is further corrected by △P g. The correction value p4z-m) H of the wave B2411 is determined, and the threshold 1aPms of the corona bond portion 4 and the nugget portion 3 determined in advance and the correction lit P(2-111) of the m-th reflected wave P2-In are calculated.
By comparing H, it is possible to determine whether it is the nugget portion 3 or the corona bond portion 4.

In other words, the output correction 1 direct P of the gate G8 of the nugget section 3
(2-111) Read out the threshold value Pms set in advance to be intermediate between H(N) and the output correction 1mP(2-111)H(C) of the gate GB of the corona bond section 4, and
The section where (2-n+)H≦Pms is determined to be the nugget portion 3. The total value of the minute scanning displacements ΔX in this section is defined as the nugget diameter DN.

If we organize the above, we get the following.

(2) Determine the presence or absence of the first reflected wave 3H among the multiple reflected waves from the bottom surface FA of the upper plate 1 for each minute scanning displacement ΔX. As a result, the position of the outer edge of the welded portion 6 including the corona bond portion 4 and the nugget portion 3 can be determined.

■In the area determined to be the welding part 6, multiple reflected waves are captured for each minute scanning displacement △
Calculate the variation Δ between the height P of z−m and the set value of the surface wave S height Px, and calculate the correction value p(+) H= p 2
−In−Δ&, is determined.

■Compare the obtained value of Fh-m>H with the threshold 1iPms, and
(□) The section where H≦Pms is determined to be nugget 3.

(2) Calculate the nugget diameter DN from the scanning displacement amount of the section determined to be the nugget portion 3.

Next, a specific embodiment of the present invention will be described with reference to FIG.

FIG. 8 shows an example of an apparatus for carrying out the method of the invention and an example of a situation in which the apparatus is used to carry out the method of the invention.

In FIG. 8, a conical focusing probe 7 is provided at the tip of an ultrasonic probe 10, and this ultrasonic probe 10 is driven by a drive device such as a motor (not shown). The probe 7 is configured to scan the surface of the upper plate 1 by being driven by the probe 7 . A displacement meter 11 is attached to the ultrasonic probe device 10 so that the amount of scanning displacement of the probe 7 can be detected. The head of the ultrasonic probe 10 includes a clear device switch 13 and a scan OK lamp 1.
4. A welding grade selection button 15 is provided.

The probe 7 of the ultrasonic probe bag @10 has an ultrasonic transmitter/receiver 16.
is connected to the ultrasonic transmitting/receiving section 16, and a plate thickness measuring section 17 and a welding zone boundary determining section 18 are connected to the ultrasonic transmitting/receiving section 16. A waveform storage processing section 19 having a built-in unique memory is connected to the welding zone boundary determination section 18 and the above-mentioned displacement meter 11. Furthermore, the waveform storage processing section 19 is a nugget discriminator 20.
The nugget discrimination section 20 is connected to the nugget diameter calculation section 2.
Connected to 1. The nugget diameter calculation section 21 and the above-mentioned plate thickness measurement section 17 are connected to a pass/fail judgment comparison section 22 , and this pass/fail judgment comparison section 22 is connected to a pass/fail judgment display section 23 . , nugget discriminator 2
0, the nugget diameter calculation section 21 and the pass/fail determination comparison section 22 are constituted by a microcomputer 24.

A specific example of a method for actually determining the diameter of the nugget portion 3 and determining the quality of spot welding using the above-mentioned apparatus will be described below.

First, use the ultrasonic probe 7 to measure the recess of the spot weld.
That is, it is pressed against the surface of the upper plate 1 in the area 1 or V in FIG. The multiple reflected waves for the incident ultrasonic pulse are transmitted to the ultrasonic transceiver unit 1 via the ultrasonic probe 7 again.
6 is input. At this time, in the area work or V of the non-welded part 5, the incident ultrasonic longitudinal wave is reflected at the bottom surface of the upper plate 1, so based on the reflected wave, the plate thickness measurement unit 17 determines the plate thickness t of the upper plate 1. , and the upper plate thickness measurement value t is input into the pass/fail judgment comparison section 22 and stored.

Next, the ultrasonic probe 7 is pressed against the center of the recess of the spot weld, that is, the center of area (■) in FIG. However, the plate thickness is similarly measured in the plate thickness measuring section 17, and the measured value is input to the pass/fail determination comparison section 22.

At this time, if no weld is formed, the reflected wave will be a reflected wave from the bottom of the top plate 1, so the measured plate thickness will be close to the thickness of the top plate 1, and in that case, pass/fail judgment will be made. The comparison unit 22 determines that the weld is defective through arithmetic processing, and the pass/fail determination display unit 23 issues a display or alarm indicating the weld defect. On the other hand, if the welded part 6 is formed, that is, if the upper plate 1 and the lower plate 2 are integrated, the reflected wave will be from the bottom of the lower plate 2, so the measured value of the plate thickness will be III close to the total value of the thickness of the upper plate 1 and the thickness of the lower plate 2
It becomes t3. This welded portion plate thickness t3 is input to the pass/fail judgment comparison section 22, and the plate thickness t of the upper plate 1 which is already stored is
, and a comparison operation is performed. That is, t3-t1=t2
One shift of t2 is calculated, and the smaller value of the thickness approximation 111i of the lower plate 2) and the value of t (thickness of the upper plate 1) is the reference plate thickness ts. is selected and stored.

Next, the grade of the spot weld to be inspected is selected using the welding grade selection button 15 provided at the head of the ultrasonic probe 10, and the grade signal generated by the selection or the grade signal read by the selection is passed or rejected. It is input to the determination comparison section 22. When the grade signal is input, a nugget reference diameter serving as a criterion according to the welding grade and the reference plate thickness ts is calculated or read out and stored as a nugget diameter comparison reference ft1IDS.

When this is completed, the ultrasonic probe 7 is pressed against the outside of the recess of the spot weld, that is, the area ■ or area V in FIG.
1 is aligned with the direction in which the probe 7 is to be scanned, that is, the direction line extending from the outside of the recess of the spot weld, passing through the center of the recess, and then exiting to the outside of the recess. In this state, the scan OK lamp 14 provided on the head of the ultrasonic probe 10 lights up, and after confirming that the received ultrasonic waves are being applied to the weld boundary determination unit 18, the ultrasonic The sonic probe 7 starts scanning. In other words, as shown in FIG. 4, scan from the area ■ or V outside the depression to the area ■ or ■v along a straight line passing through the center of the depression, and then roughly scan the area ■
Scan through the area IIV or ■ and scan to the outer area of the depression ■ or the king.

In the above-described scanning process, received waveforms as shown in FIG. 5 are obtained in each scanning area W to V as described above. That is, when the ultrasonic probe 7 is located in the region ■ or region ■ of the non-welded portion 5, multiple reflected waves from the bottom surface of the upper plate 1 are received, while in the region When installing the device in area ■ of nugget part 3,
The reflected waves from the bottom surface of the lower plate 2 are not received, but the multiple reflected waves from the bottom surface of the lower plate 2 are received.

Here, among the outputs p2-111 of the gate GB in the regions ■, ■, and IV, the regions ■, I
The gate output p 2-111 IC) at V and the gate output p 2-+11 (
H) indicates a different shift.

Therefore, in this scanning process, the above-mentioned relationship is utilized to first determine the boundary between the area welding area and area (2) or the boundary between area V and area IV, which is the boundary of the weld. Roughly speaking, the gate G is located at a position determined to be within the boundary of the welding part 6.
Find the output P2-I11 of B and the output p<g of the gate (33) of the surface wave S, find the difference △P between the setting 1IPos of the surface wave S and the gate output P, and calculate the output of the gate GB. P
2-I11 corrected IIIP (open) H (=P2.-△
P-1>, the nugget discriminating section 20 determines whether it is the area (2) or IV of the corona bond part 4 or the area (2) of the nugget part 3.

In this way, from the time when the output of the gate GA disappears, that is, from the time when it is determined that the weld zone boundary exists, the output P24+ of the gate G8 of the multiple reflection waveform and the output P% of the gate GS,
is input to the waveform storage processing unit 19 for each minute scanning displacement ΔX, and its output is stored.

In other words, while scanning the areas ■, ■, and IV determined to be the welded part 6, for each minute scanning displacement △X given from the displacement meter 11, among the multiple reflected waves from the bottom surface of the lower plate 2, The output P2-1 of the gate G8 and the output Peda of the gate 1-GS of the reflected wave from the surface of the upper plate 1 are stored in the waveform storage processing section 19. By inputting these values to the nugget discriminating section 20, the nugget discriminating section 20 reads out the height pos of the surface wave S which has been set and stored in advance, and calculates the difference Δ from the gate output Pz. , is calculated. Roughly speaking, the output p+c of the gate G8 in the corona bond part 4
N) and the output Pz-+ of the gate GB in the nugget section 3
The threshold flIiPms, which has been set and stored in advance as a threshold for determining lC/, is read out, and the correction value R2-m)H(=Pz-m-) of the output of gate G8 is read out.
△PX, ). And Rz-m)H≦P
ms, the scanning position is determined to be in the nugget portion 3, and the total number Y of minute scanning displacements ΔXN at the scanning position determined to be the nugget portion 3 and the smile scanning displacement ΔXN are The data is taken into the nugget calculation section 21. In the nugget diameter calculation unit 21, the minute scanning displacement amount △XN at the position determined to be the nugget portion 3 and its number Y are multiplied, and the product 11 (△XNXY> is equal to the nugget 1 line [)N. be done.

The 1 shift of the nugget defect [)H removed in this way is input to the pass/fail judgment comparison section 22, and the nugget 1
~The diameter comparison reference value Ds is compared. And [)N <[
) S, that is, if it is determined that the measured nugget diameter DNfJ'
The pass/fail determination display section 23 displays a failure or issues a warning. If [)N≧Ds, it means that the nugget failure satisfies the required value, so it is determined to be a pass, and a pass is displayed on the pass/fail determination display section 23.

As described above, by using the apparatus shown in FIG. 8, the nugget diameter DN
can be roughly measured and judged based on the results. The entire inspection procedure is summarized in the flowchart of FIG.

In FIG. 1, first, in step 101, the plate thickness t of the upper plate 1 is taken in, and then in step 102, the total plate thickness t3 at the welding area (total plate thickness of the upper plate 1 and the lower plate 2)
take in. Next, in step 103, step 1
The overall plate thickness t obtained in step 02 and the plate thickness t of the upper plate 1 obtained in step 101 are reduced to obtain the plate thickness t2 of the lower plate 2.

12=ta tt Then, the smaller of the thickness t of the upper plate 1 and the thickness t2 of the lower plate 2 is defined as the reference plate thickness ts.

Next, in step 104, welding grade N (-5,4
or 3), and calculates or reads out the required nugget diameter (nugget diameter comparison standard 1IiI>DS) according to the weld grade N and standard plate thickness ts. is scanned, and the output of the gate Gs, the output of the gate GA, and the output of the gate GB of the multiple reciprocal waves are acquired for each minute scanning displacement.

Next, in step 106, among the multiple reflected waves from the bottom surface IA of the upper plate 1, a section where the first reflected wave B and 1 disappears and the output of the gate GA disappears is determined, and in that section, the surface wave The difference between the output Peda of the gate GS of S and the preset 1st position pos, and the bottom surface 2A of the lower plate 2.
From the output P of the gate G8 at the height of the m-th foul wave B, the correction value P(2-=ll) H(=Pz
-m-△P, s) and compared with the reference peak value (threshold value) pms, the area where mouth+sH≦pms is determined to be the nugget portion 3, and the minute scanning displacement amount △ of the nugget portion 3 is taken. The nugget diameter D is determined by XN and the number Y of its scanning displacement.
N is calculated.

Once the nugget diameter DN has been calculated, the process proceeds to step 107, where the nugget diameter [)N is determined as the comparison standard 1iiiD S
If it is determined that [)N < [)s, an abnormality in the nugget diameter is displayed in step 108, and the flow ends. On the other hand, in step 108, DN≧[)
If it is determined as S, it is normal, and the process ends without displaying any abnormality.

[Effects of the Invention] As explained above, in the spot weld inspection method according to the present invention, the height of the reflected wave at a time from the surface wave set in advance for each minute scanning displacement is determined, and the height of the reflected wave is The height of the reflected wave is compared with the standard value of the height of the reflected wave at the set time, and if the calculated height of the reflected wave is smaller than the standard value, it is called a nugget part, and if it is larger than this reference value, it is called a corona part. Since the nugget diameter is determined as the scanning displacement amount at each portion determined to be a bond portion and the nugget portion, the process for determining whether the portion is a nugget portion is significantly easier than in the conventional method.

Therefore, the judgment processing time can be shortened, and
A device with high processing power is not required, and an inexpensive inspection device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the processing procedure of the spot weld inspection method according to the present invention, FIGS. 2 (A) and (B) are waveform diagrams showing multiple reflection waveforms of the spot weld according to the present invention, and FIG. is an enlarged cross-sectional view of the vicinity of the spot weld, Figure 4 is a cross-sectional view showing the relationship between the spot weld and the scanning position of the ultrasonic probe, and Figure 5 is the reception of ultrasonic pulses in each area of Figure 4. Waveform diagram showing the waveform, Figure 6 is a graph to distinguish between welded areas and non-welded areas]・
FIG. 7 is a waveform diagram showing the degree of attenuation of reflected waves at the welded portion; FIG. 8 is a schematic configuration diagram of an apparatus for carrying out the present invention. 1...Top plate 2...Bottom plate 3...Nugget part 4...Corona bond part 5...Non-welded part 6... ...Welding part 7...Ultrasonic probe S...Surface wave B...Reflected wave License applicant Toyota Motor Corporation Figure 2 (A ) Figure 3

Claims (1)

[Claims] 1. An ultrasonic probe is scanned across the surface of a spot weld, and the reflected waves of the ultrasonic waves are captured at every minute scanning displacement, and the reflected waves are In the method of inspecting a spot weld based on the method, when scanning the weld including the nugget part of the spot weld and the surrounding corona bond part, a preset time from the surface wave for each minute scanning displacement is provided. Find the height of the reflected wave at , compare the height of the reflected wave with a reference value for the height of the reflected wave at the set time, and if the height of the reflected wave determined is smaller than the reference value, the nugget section A method for inspecting spot welding, characterized in that a case where the value is larger than the reference value is determined to be a corona bond portion, and the amount of scanning displacement at the portion determined to be the nugget portion is determined as the nugget diameter.