Aluminum alloy weld straight edge incomplete fusion defect detection method

Abstract

The application discloses a kind of aluminum alloy weld seam straight edge un-melted defect detection methods, the method uses oblique probe in aluminum alloy weld seam and its both sides scanning detection, the scanning path of oblique probe is square wave shape, the direction of oblique probe is perpendicular to the direction of aluminum alloy weld seam in whole scanning process, and 10°-15° left and right deflection is made while moving scanning;Oblique probe moves scanning along the direction perpendicular to aluminum alloy weld seam, and the moving distance is ≥T1×tan beta+L, wherein T1 is the thickness of bevel side workpiece, beta is probe refraction angle, and L is probe length;Oblique probe moves scanning along the direction parallel to aluminum alloy weld seam, and the moving distance is ≤0.9×probe width;The present application can find the straight edge un-melted defect extending to surface and not extending to surface, solves the problem that internal straight edge un-melted defect not extending to surface cannot be detected by penetration detection method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of aluminum alloy defect detection, and particularly relates to a detection method for a 5mm-8mm-thickness aluminum alloy weld seam straight edge un-melted defect. BACKGROUND

[0002] In the aluminum alloy car body structure of a city rail vehicle, there are many weld seams with a thickness of less than 8mm, among which 5HV and 6HV (i.e. 6mm-melted semi-V-shaped weld seam) are the most common weld seam types. The weld seam is a full penetration weld seam, and the weld seam excess height is required to be ground flat after welding. After the welding and the weld seam excess height grinding flat are completed, the weld seam 6 is subjected to penetration detection, and it is found that there is linear display at the joint position of the weld seam 6 and the straight edge side workpiece 1 (the linear display direction is parallel to the weld seam direction, which belongs to longitudinal display). When the defect is removed, it has a certain depth and length, and a part of the area of the defect only exists in the weld seam 6 and does not extend to the surface of the weld seam 6. The defect extension direction is perpendicular to the surface. Through analysis, the defect is a straight edge un-melted 5 defect, and the weld seam structure and the straight edge un-melted 5 defect are shown in Figs. 1 and 2. If the straight edge un-melted 5 defect is not found in time and corresponding rework measures are not taken, the straight edge un-melted 5 defect will continuously extend and expand in the running process of the city rail vehicle, which exists quality and safety hidden dangers. Figure 1 、 Figure 2

[0003] At present, the detection method combining penetration detection and post-slotting penetration detection is adopted for this type of weld seam. The limitation of the penetration detection method is that only the open defects extending to the surface can be detected. During the detection, first, the first penetration detection is performed on the whole weld seam to detect the open straight edge un-melted defect extending to the surface, then the defect is removed by slotting, and the second penetration detection is performed on the slotting to confirm whether the defect is completely removed. If there is still defect display, the third slotting and penetration detection are performed until the defect is completely removed. This detection method is time-consuming, and the randomness of the detection result is great. For the weld seam inside the area without defect display in the first penetration detection, no detection and control will be performed.

[0004] At present, the conventional non-destructive detection methods also include magnetic powder detection, eddy current detection, ray detection, ultrasonic wave detection and the like. The magnetic powder detection is suitable for ferromagnetic materials, and the aluminum alloy material is not magnetized, so it is not suitable. The eddy current detection belongs to the surface and near-surface detection method, and sometimes when a suspicious signal is found, other non-destructive detection methods need to be used for further confirmation. The detection effect is not good and the detection efficiency is low. The ray detection is not suitable because of the radioactive hazard and the fact that the back of the weld seam is in a closed cavity and the photosensitive film cannot be arranged. The conventional detection process of the ultrasonic wave technology is only suitable for full penetration weld seams with a thickness of 8mm and above, and it is not suitable for this weld seam (i.e. weld seam with a thickness of less than 8mm).

[0005] ​How to realize accurate and effective detection of 5HV, 6HV and other 8mm or less thickness of aluminum alloy weld straight edge un-melted defects is a big problem in the existing nondestructive testing technology field. SUMMARY

[0006] The purpose of the present application is to provide an aluminum alloy weld straight edge un-melted defect detection method to solve the problem that the internal straight edge un-melted defect which does not extend to the surface cannot be detected by the penetration detection method, and the problem of long detection time and large randomness of detection results.

[0007] The present application solves the above technical problems by the following technical scheme: an aluminum alloy weld straight edge un-melted defect detection method, comprising the following steps:

[0008] Selecting instrument and probe: selecting a digital ultrasonic flaw detector, and selecting a transverse wave oblique probe with a refraction angle of 68°-72° and a frequency of 2.5MHz-5MHz in aluminum alloy material;

[0009] Instrument calibration: using a standard test block to measure and calibrate the digital ultrasonic flaw detector and the transverse wave oblique probe;

[0010] DAC curve making: adjusting the horizontal scale of the display screen of the digital ultrasonic flaw detector to sound path, and making DAC curve by using the transverse through holes with different depths on the contrast test block;

[0011] Adjusting detection sensitivity: adjusting the height of the starting position of the DAC curve to 80% of the full scale of the display screen of the digital ultrasonic flaw detector, and setting the evaluation line of the digital ultrasonic flaw detector to DAC-14dB, and then increasing the detection sensitivity by 10dB-14dB on this basis;

[0012] Workpiece preparation: polishing the aluminum alloy weld flat, and marking the joint position of the aluminum alloy weld and the straight edge side workpiece;

[0013] Weld scanning: using the transverse wave oblique probe to scan and detect the aluminum alloy weld and its two sides, the scanning path of the transverse wave oblique probe is in the shape of a square wave, the placement direction of the transverse wave oblique probe is perpendicular to the direction of the aluminum alloy weld during the entire scanning process, and the transverse wave oblique probe is deflected left and right by 10°-15° while moving scanning; when the transverse wave oblique probe moves scanning along the direction perpendicular to the aluminum alloy weld, the moving distance is ≥T1*tanβ+L, wherein T1 is the thickness of the bevel side workpiece, β is the probe refraction angle, and L is the length of the probe; when the transverse wave oblique probe moves scanning along the direction parallel to the aluminum alloy weld, the moving distance is ≤0.9*probe width H;

[0014] Defect judgment: obtaining the corresponding echo of the defect according to the weld scanning, judging the defect according to the echo, and determining the defect position.

[0015] Further, the determination and calibration of the digital ultrasonic flaw detector and the oblique transverse wave probe by using the standard test block specifically include:

[0016] The determination and calibration of the time base, the sound velocity and the probe front length of the digital ultrasonic flaw detector and the oblique transverse wave probe are performed by using the two circular arc surfaces with the radius of 100 mm and 50 mm on the CSK-IA standard test block.

[0017] The determination and calibration of the probe K value are performed by using the Φ50 mm hole on the CSK-IA standard test block, wherein the probe K value = (the defect horizontal position display value + the probe front length) / the defect depth value.

[0018] Further, when the DAC curve is made, the depth of the transverse hole at the selected deepest position is greater than the depth of the weld penetration of the aluminum alloy weld to be detected; preferably, the DAC curve is made by using the transverse holes with the depths of 5 mm, 10 mm and 15 mm on the contrast test block in sequence.

[0019] Further, the surface roughness of the polished aluminum alloy weld is not greater than Ra6.3um.

[0020] Further, the identification width of the joint position is 0.25 mm to 1 mm.

[0021] Further, the workpiece preparation further includes: coating the coupling agent on the surface of the workpiece and the scanning area of the oblique transverse wave probe.

[0022] Further, during the weld scanning, the moving speed of the oblique transverse wave probe is 50 mm / s to 100 mm / s.

[0023] Further, when the oblique transverse wave probe moves and scans along the direction parallel to the aluminum alloy weld, 0.5 x the probe width H ≤ the moving distance ≤ 0.9 x the probe width H.

[0024] Further, the weld scanning adopts the single-side and double-side scanning detection, and the specific implementation process includes:

[0025] The aluminum alloy weld and the two sides thereof are scanned and detected by taking the point close to the identification position and the straight side workpiece edge position and located on the straight side workpiece as the starting point of the probe and along the square wave-shaped path.

[0026] The aluminum alloy weld and the two sides thereof are scanned and detected by taking the point close to the identification position and the straight side workpiece edge position and located on the straight side workpiece as the starting point of the probe and along the square wave-shaped path.

[0027] Further, the defect is judged when the defect echo amplitude reaches the evaluation line, and the specific implementation process of the defect judgment is as follows:

[0028] When the straight edge unfused defect does not extend to the workpiece surface, the defect height is determined based on the depth position of the diffraction echo generated by the transverse wave beam at the upper and lower ends of the straight edge unfused defect.

[0029] When a straight-edge unfused defect extends to the workpiece surface, the defect height is determined based on the depth position of the diffraction echo generated by the transverse wave beam at the lower end of the straight-edge unfused defect and the surface opening position of the defect detected by the surface wave.

[0030] The upper endpoint refers to the highest point where the aluminum alloy weld and the straight-edge workpiece meet, while the lower endpoint refers to the junction of the aluminum alloy weld, the straight-edge workpiece, and the welding pad.

[0031] Beneficial effects

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] The present invention provides a method for detecting straight-edge non-fusion defects in aluminum alloy welds. This method utilizes the shear wave main beam axis of a shear wave angle probe incident on the middle region of the aluminum alloy weld, enabling the detection of both straight-edge non-fusion defects extending to and not extending to the surface. This solves the problem that penetrant testing methods cannot detect internal straight-edge non-fusion defects that do not extend to the surface. The invention uses ultrasonic waves for defect detection, eliminating the need for trenching and removal, greatly improving detection efficiency and the reliability of the results. It enables effective detection of the entire weld, effectively ensuring product quality. Attached Figure Description

[0034] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the weld structure in the background art of this invention;

[0036] Figure 2 This is a schematic diagram of a straight-edge non-fusion defect in the background art of this invention;

[0037] Figure 3 This is a scanning path diagram in an embodiment of the present invention when a point on the workpiece on the straight edge is used as the probe starting point (straight edge scanning);

[0038] Figure 4 This is a scanning path diagram in an embodiment of the present invention when a point on the workpiece on the bevel side is used as the probe starting point (bevel side scanning);

[0039] Figure 5is a schematic diagram of the probe moving area when a point on the straight side workpiece is taken as the starting point of the probe in the embodiment of the present application;

[0040] Figure 6 is a schematic diagram of the probe moving area when a point on the groove side workpiece is taken as the starting point of the probe in the embodiment of the present application;

[0041] Figure 7 is a schematic diagram of the detection of the straight side un-melted defect which does not extend to the surface in the embodiment of the present application;

[0042] Figure 8 is a schematic diagram of the detection of the straight side un-melted defect which extends to the surface in the embodiment of the present application.

[0043] Wherein, 1-straight side workpiece, 2-groove side workpiece, 3-welding backing plate, 4-joining position, 5-straight side un-melted, 51-upper end point, 52-lower end point, 6-aluminum alloy weld, 7-transverse wave oblique probe, 8-probe incident point, 9-scan path. DETAILED DESCRIPTION

[0044] The technical solutions in the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0045] The technical solutions of the present application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes can not be described repeatedly in some embodiments.

[0046] The detection method for the straight side un-melted defect of the aluminum alloy weld with the thickness of 5mm-8mm provided by the embodiment of the present application comprises the following steps:

[0047] 1. Selecting the instrument and the probe: a digital ultrasonic flaw detector which is qualified by the relevant department is selected, and a transverse wave oblique probe 7 with the refraction angle of 68°-72° and the frequency of 2.5MHz-5MHz in the aluminum alloy material is selected.

[0048] The limitation of the refraction angle and the frequency parameter makes the transverse wave oblique probe 7 not only refract the sound wave to produce the transverse wave in the workpiece, but also produce certain surface wave which propagates along the surface of the workpiece. The transverse wave and the surface wave exist simultaneously during the detection, which can detect the internal position defect of the workpiece and the surface position defect of the workpiece. In the embodiment, the use of the transverse wave oblique probe 7 can realize the use of the transverse wave and the surface wave, and can detect and position the internal straight side un-melted defect 5 of the surface opening and the surface un-opening.

[0049] 2. Instrument calibration: The digital ultrasonic flaw detector and the oblique transducer are measured and calibrated by using the standard test block.

[0050] In this embodiment, the digital ultrasonic flaw detector and the oblique transducer are measured and calibrated by using the standard test block, which specifically includes:

[0051] The time base, sound velocity and transducer front length of the digital ultrasonic flaw detector and the oblique transducer are measured and calibrated by using the two circular arc surfaces with a radius of 100 mm and 50 mm on the CSK-IA standard test block; the transducer K value is measured and calibrated by using the Φ50 mm hole on the CSK-IA standard test block, wherein the transducer K value = (defect horizontal position display value + transducer front length) / defect depth value.

[0052] The measurement and calibration of the digital ultrasonic flaw detector and the oblique transducer facilitate accurate determination of the position of the echo reflection point in the aluminum alloy weld 6 during detection, and judgment of whether there is a straight side un-melted 5 defect.

[0053] 3. DAC curve making: The horizontal scale of the display screen of the digital ultrasonic flaw detector is adjusted to be the sound path, and the DAC curve is made by using the different depth transverse holes on the contrast test block.

[0054] The DAC curve is made by using the Φ3 mm transverse holes with different depths on the RB-1 contrast test block, the horizontal scale of the display screen of the ultrasonic flaw detector is adjusted to be the sound path, and the DAC curve is made by using the transverse holes with a depth of 5 mm, 10 mm and 15 mm on the RB-1 contrast test block in turn. The depth value of the deepest position transverse hole used for making the DAC curve (15 mm in this embodiment) should be greater than the depth value of the aluminum alloy weld 6 being detected. The DAC curve is used as the DAC reference curve to judge the severity of the reflected echo.

[0055] There are three types of horizontal, depth and sound path for the horizontal scale display of the display screen of the ultrasonic flaw detector. During detection, the surface wave is used to detect the surface opening position defect, and if the depth and horizontal types are set, the surface opening position defect will not be displayed in the display screen and will be missed.

[0056] 4. Adjusting the detection sensitivity: The height of the starting position of the DAC curve is adjusted to be 80% of the full scale of the display screen of the digital ultrasonic flaw detector, and the evaluation line of the digital ultrasonic flaw detector is set to DAC-14 dB. On this basis, the detection sensitivity is further increased by 10 dB to 14 dB, and the detection sensitivity value is higher than that of the Φ3 mm transverse hole of the RB-1 contrast test block by 10 dB to 14 dB, which is conducive to detecting the straight side un-melted 5 defect and improving the detection accuracy.

[0057] 5. Workpiece preparation: After the aluminum alloy weld 6 is polished flat, mark the joint position 4 of the aluminum alloy weld 6 and the straight side workpiece 1.

[0058] Marking the joint position 4 of the aluminum alloy weld 6 and the straight side workpiece 1 is beneficial to accurately determine the position of the echo reflection point in the weld during detection, and to determine whether the straight side un-melted 5 defect exists. The marking line should have the characteristics that it is not washed off by the applied coupling agent during detection, and it does not damage the surface of the aluminum alloy workpiece; at the same time, in order to ensure that the marking line does not affect the positioning of the straight side un-melted 5 defect during detection and is convenient to observe, the width of the marking line (i.e. the marking width) is controlled between 0.25mm and 1mm. In this embodiment, only the joint position 4 needs to be marked, and the entire weld area does not need to be marked.

[0059] In this embodiment, the temperature difference between the weld cooling to room temperature and the calibration temperature of the weld detection and digital ultrasonic detector is not more than 15℃, to ensure the accuracy of the detection result, and the weld surface excess height is polished flat and smooth, and the surface roughness of the polished aluminum alloy weld 6 is not more than Ra6.3um, to maintain good acoustic contact.

[0060] During workpiece preparation, coupling agent is also applied on the workpiece surface and the scanning area of the shear wave oblique probe 7. The coupling agent requires low viscosity and good flowability, and can freely spread and flow after being applied on the workpiece, without accumulation. In this embodiment, the coupling agent is applied on the workpiece by brushing, to exclude air between the probe and the workpiece surface, so that ultrasonic waves can be transmitted into the workpiece, and to avoid reflection of the coupling agent accumulated on the workpiece surface during detection, which affects normal judgment and causes misjudgment. When a coupling agent with high viscosity is used, the coupling agent is easy to accumulate or locally protrude on the workpiece surface, and the surface wave will produce a reflected echo during detection, which affects normal judgment.

[0061] 6. Weld scanning: The shear wave oblique probe 7 is used to scan and detect the aluminum alloy weld 6 and its two sides, and the scanning path 9 of the shear wave oblique probe 7 is in the shape of a square wave, as shown in Figure 3 and 4 During the entire scanning process, the placement direction of the shear wave oblique probe 7 is perpendicular to the direction of the aluminum alloy weld 6, and at the same time of moving scanning, it is deflected left and right by 10°-15° (i.e. the included angle between the probe direction and the weld direction during detection), to ensure that the sound beam is nearly perpendicular to the extension direction of the straight side un-melted 5 defect, at which time the reflected echo is the strongest; when the shear wave oblique probe 7 moves and scans along the direction perpendicular to the aluminum alloy weld 6, the moving distance is ≥T1×tanβ+L, where T1 is the thickness of the bevel side workpiece 2, β is the probe refraction angle, and L is the probe length; when the shear wave oblique probe 7 moves and scans along the direction parallel to the aluminum alloy weld 6, the moving distance is ≤0.9×probe width H, as shown in Figure 5 and 6 .

[0062] In this embodiment, the weld seam scanning adopts single-side double-side scanning detection, and the double-side refers to the straight side workpiece 1 and the groove side workpiece 2. The specific implementation process includes:

[0063] (1) The probe is placed on the outer surface of the straight side workpiece 1 to scan and detect the weld seam (straight side scanning)

[0064] Step 6.11: Taking a point close to the mark position and the edge position of the straight side workpiece 1 and located on the straight side workpiece 1 as the starting point of the probe;

[0065] Step 6.12: Moving from the straight side workpiece 1 to the groove side workpiece 2 (moving along the direction perpendicular to the weld seam, i.e. Y direction), the moving distance P2≥T1×tanβ+L;

[0066] Step 6.13: After moving a distance P2, moving along the direction parallel to the weld seam on the groove side workpiece 2 (i.e. the negative direction of X), the moving distance is ≤0.9×probe width H;

[0067] Step 6.14: After moving a distance ≤0.9×probe width H, moving from the groove side workpiece 2 to the straight side workpiece 1 (moving along the direction perpendicular to the weld seam, i.e. the negative direction of Y), the moving distance P2≥T1×tanβ+L;

[0068] Step 6.15: After moving a distance P2, moving along the direction parallel to the weld seam on the straight side workpiece 1 (i.e. the negative direction of X), the moving distance is ≤0.9×probe width H;

[0069] Repeat steps 6.12-6.15 until the whole weld seam scanning and detection is completed, and the scanning path 9 and direction are as shown in Figure 3 .

[0070] (2) The probe is placed on the outer surface of the groove side workpiece 2 to scan and detect the weld seam (groove side scanning)

[0071] Step 6.21: Taking a point close to the mark position and the edge position of the groove side workpiece 2 and located on the groove side workpiece 2 as the starting point of the probe;

[0072] Step 6.22: Moving from the groove side workpiece 2 to the straight side workpiece 1 (moving along the direction perpendicular to the weld seam, i.e. the negative direction of Y), the moving distance P1≥T1×tanβ+L;

[0073] Step 6.23: After moving a distance P1, moving along the direction parallel to the weld seam on the straight side workpiece 1 (i.e. the negative direction of X), the moving distance is ≤0.9×probe width H;

[0074] Step 6.24: When the moving distance is less than or equal to 0.9 x the probe width H, the probe is moved from the straight side workpiece 1 to the bevel side workpiece 2 (in the direction perpendicular to the weld, Y direction), and the moving distance P1 is greater than or equal to T1 x tan β + L;

[0075] Step 6.25: When the moving distance P1 is reached, the probe is moved along the direction parallel to the weld on the bevel side workpiece 2 (i.e. the negative direction of X), and the moving distance is less than or equal to 0.9 x the probe width H.

[0076] Steps 6.22-6.25 are repeated until the entire weld is scanned and detected, and the scanning path 9 and direction are as shown in Figure 4

[0077] When the probe is placed on the outer surface of the bevel side workpiece 2 and the weld is scanned and detected by the once wave direct method, the probe moving area P1 is greater than or equal to T1 x tan β + L, and the starting position of the probe moving area P1 is that the probe incident point 8 is located at the joint position 4 of the weld and the straight side workpiece 1, as shown in Figure 6 When the probe is placed on the outer surface of the straight side workpiece 1 and the weld is scanned and detected, the probe moving area P2 is greater than or equal to T1 x tan β + L, as shown in Figure 5 The determination of the probe moving area according to the thickness of the bevel side workpiece 2, the tangent value of the probe refraction angle and the probe length can ensure that the probe refraction horizontal wave main beam axis can be incident on the upper end point 51 and the lower end point 52 of the joint position 4 of the weld and the straight side workpiece 1, and the detection of the defect depth is ensured. The upper end point 51 refers to the topmost point of the intersection of the aluminum alloy weld 6 and the straight side workpiece 1, and the lower end point 52 refers to the intersection point of the aluminum alloy weld 6, the straight side workpiece 1 and the welding backing plate 3.

[0078] The moving scanning path 9 is in the shape of a square wave, and during the movement of the probe, the probe horizontal wave main beam is incident on the upper end point 51 and the lower end point 52 of the straight side incomplete fusion 5 defect, and the surface wave propagates along the workpiece surface to detect the surface opening position of the straight side incomplete fusion 5 defect. During the entire movement process, the probe moving speed should be less than or equal to 100 mm / s, and in order to ensure the detection efficiency, the probe moving speed is controlled to be between 50 mm / s and 100 mm / s. When the horizontal wave oblique probe 7 moves and scans along the direction parallel to the aluminum alloy weld 6, the moving distance is greater than or equal to 0.5 x the probe width H and less than or equal to 0.9 x the probe width H.

[0079] ​Sound beam reflection requires a reflecting surface. Because the direction of the straight-edge unfused defect is perpendicular to the workpiece surface, the sound beam usually produces almost no reflected echo at this defect surface in typical scanning methods, thus failing to detect the straight-edge unfused defect. Sound diffraction is the process where the sound beam generates a diffraction signal at the defect endpoint. This diffraction signal propagates in all directions from the defect endpoint, and can be received and identified by the probe. In this embodiment, a transverse wave main sound beam is incident on the upper endpoint 51 and lower endpoint 52 of the straight-edge unfused defect, generating diffraction echoes, thus enabling the identification of the straight-edge unfused defect.

[0080] 7. Defect Judgment: Obtain the echo corresponding to the defect based on the weld scan, judge the defect based on the echo, and determine the defect location.

[0081] (1) Analysis of echoes from straight-edge unfused defects that do not extend to the surface

[0082] like Figure 7 As shown, the probe is placed on the outer surface of the workpiece 2 on the bevel side and moved in a direction perpendicular to the weld to scan and inspect the weld. When the probe moves to position 1 and position 2, that is, when the axis of the probe's refracted transverse wave main sound beam is incident on the upper end point 51 and lower end point 52 of the straight edge unfused defect 5, diffraction echoes will be generated.

[0083] like Figure 7 As shown, the probe is placed on the outer surface of the workpiece 1 on the straight edge and moves along the direction perpendicular to the weld to scan and detect the weld. When the probe moves to position 3 and position 4, that is, when the axis of the probe's refracted transverse wave main sound beam is incident on the upper end point 51 and lower end point 52 of the straight edge unfused defect 5, diffraction echoes will be generated.

[0084] (2) Analysis of echoes from straight-edge unfused defects that have extended to the surface

[0085] like Figure 8 As shown, the probe is placed on the outer surface of the workpiece 2 on the bevel side and moved along the direction perpendicular to the weld to scan and inspect the weld. When the probe moves back and forth to position 5, at this time, the distance from the probe incident point 8 to the opening position of the straight edge unfused defect 5 is less than about 25mm (the smaller the distance value, the more accurate the positioning and the stronger the echo). The surface wave generated by the probe propagates along the surface of the workpiece and can reach the opening position of the straight edge unfused defect 5 and generate a reflected echo. When the probe moves to position 6, the axis of the probe refracted transverse wave main sound beam is incident on the lower end point 52 of the straight edge unfused defect 5, generating a diffracted echo.

[0086] like Figure 8As shown, the probe is placed on the outer surface of the straight side workpiece 1 to move along the direction perpendicular to the weld to scan and detect the weld. When the probe moves to position 7, at this time, the probe incident point 8 is less than about 25mm (the smaller the distance value, the more accurate the positioning, and the stronger the echo) to the opening position of the straight side incomplete fusion 5 defect, the surface wave generated by the probe propagates along the workpiece surface, can reach the opening position of the straight side incomplete fusion 5 defect and can produce a reflected echo; when the probe moves to position 8, the refracted transverse wave main beam axis of the probe is incident to the lower end point 52 of the straight side incomplete fusion 5 defect, and a diffraction echo is generated.

[0087] When the defect echo amplitude reaches the evaluation line (DAC-14dB), the defect is judged, and the specific implementation process of the defect judgment is as follows:

[0088] When the straight side incomplete fusion 5 defect does not extend to the surface of the workpiece, the defect height is determined according to the depth position of the diffraction echo of the transverse wave beam at the upper end point 51 and the lower end point 52 of the straight side incomplete fusion 5 defect (i.e. the difference between the depth positions of the diffraction echoes of the upper end point 51 and the lower end point 52); when the straight side incomplete fusion 5 defect extends to the surface of the workpiece, the defect height is determined according to the depth position of the diffraction echo of the transverse wave beam at the lower end point 52 of the straight side incomplete fusion 5 defect and the surface opening position of the defect detected by the surface wave (i.e. the difference between the depth position of the diffraction echo of the lower end point 52 and the surface opening position). By reading the depth position of the diffraction echo of the defect end point or the reflected echo of the defect opening position, the height and size of the defect itself can be judged.

[0089] After the defect position is determined, the defect position is marked on the workpiece and reworked.

[0090] The above only discloses specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can easily think of changes or modifications within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method of detecting a weld straight side un-fusion defect of an aluminum alloy, characterized by, The method comprises the following steps: Selecting an instrument and a probe: a digital ultrasonic flaw detector is selected, and a transverse wave oblique probe with a refraction angle of 68-72° and a frequency of 2.5-5 MHz in an aluminum alloy material is selected; Calibrating the instrument: a CSK-IA standard block is used to measure and calibrate the time base line, sound velocity, probe front length and K value of the digital ultrasonic flaw detector and the transverse wave oblique probe; Making a DAC curve: the horizontal scale of the display screen of the digital ultrasonic flaw detector is adjusted to be the sound path, a contrast block with transverse through holes with depths of 5 mm, 10 mm and 15 mm is used to make a DAC curve, and the transverse through hole with the deepest position has a depth greater than the penetration depth of the aluminum alloy weld to be detected; Adjusting the detection sensitivity: the height of the starting position of the DAC curve is adjusted to be 80% of the full scale of the display screen of the digital ultrasonic flaw detector, and the evaluation line of the digital ultrasonic flaw detector is set to DAC-14 dB, and then the detection sensitivity is increased by 10-14 dB; Preparing the workpiece: the aluminum alloy weld is polished to be flat, and the surface roughness is not greater than Ra 6.3 μm, and a mark with a width of 0.25-1 mm is made at the joint position of the aluminum alloy weld and the straight side workpiece; Weld scanning: the transverse wave oblique probe is used to scan and detect the aluminum alloy weld and the two sides thereof, the scanning path of the transverse wave oblique probe is in a square wave shape, the placement direction of the transverse wave oblique probe is perpendicular to the direction of the aluminum alloy weld during the whole scanning process, and the transverse wave oblique probe is deflected by 10-15° left and right while moving and scanning, the moving distance of the transverse wave oblique probe when moving and scanning in the direction perpendicular to the aluminum alloy weld is greater than or equal to T1*tanβ+L, T1 is the thickness of the bevel side workpiece, β is the probe refraction angle, and L is the length of the probe, and the moving distance of the transverse wave oblique probe when moving and scanning in the direction parallel to the aluminum alloy weld is less than or equal to 0.9*probe width H; Defect judgment: when the defect echo amplitude reaches the evaluation line, the defect is judged, and the defect is judged according to the diffraction echo of the transverse wave sound beam on the straight side unmelted defect: When the straight side unmelted defect does not extend to the surface of the workpiece, the defect height is determined according to the depth positions of the diffraction echoes of the transverse wave sound beam on the upper end point and the lower end point of the straight side unmelted defect; When the straight side unmelted defect extends to the surface of the workpiece, the defect height is determined according to the depth position of the diffraction echo of the transverse wave sound beam on the lower end point of the straight side unmelted defect and the surface opening position of the defect detected by the surface wave; Wherein, the upper end point refers to the topmost point of the joint of the aluminum alloy weld and the straight side workpiece, and the lower end point refers to the joint of the aluminum alloy weld, the straight side workpiece and the welding backing plate.

2. The method of detecting weld straightened un-fusion defects in an aluminum alloy weld bead of claim 1, wherein, The CSK-IA standard block is used to measure and calibrate the time base line, sound velocity, probe front length and K value of the digital ultrasonic flaw detector and the transverse wave oblique probe, and the measurement and calibration specifically comprises: The CSK-IA standard block is used to measure and calibrate the time base line, sound velocity and probe front length of the digital ultrasonic flaw detector and the transverse wave oblique probe through two circular arc surfaces with radii of 100 mm and 50 mm on the CSK-IA standard block; The probe K value is measured and calibrated by using a Φ50mm hole on the CSK-IA standard test block, wherein the probe K value=(defect horizontal position display value+probe front length) / defect depth value.

3. The method of detecting weld straightened un-fusion defects in an aluminum alloy weld bead of claim 1, wherein, The workpiece preparation further comprises: coating a coupling agent on the surface of the workpiece and the scanning area of the oblique transverse wave probe.

4. The method of detecting weld bead straightened un-fusion defects in an aluminum alloy as defined in claim 1, wherein During the weld scanning process, the moving speed of the oblique transverse wave probe is 50 mm / s-100 mm / s.

5. The method for detecting straight-edge lack of fusion defects in aluminum alloy welds according to any one of claims 1 to 3, characterized in that, When the oblique transverse wave probe moves and scans along the direction parallel to the aluminum alloy weld, 0.5*probe width H≤moving distance≤0.9*probe width H.

6. The method of any of claims 1-3, wherein the aluminum alloy weld straight-sided lack of fusion defect is detected by a method comprising: The weld scanning adopts single-side double-side scanning detection, and the specific implementation process comprises: Taking a point close to the mark position and located on the straight side workpiece as the starting point of the probe, the aluminum alloy weld and its two sides are scanned and detected along the square wave-shaped path; Taking a point close to the mark position and located on the straight side workpiece as the starting point of the probe, the aluminum alloy weld and its two sides are scanned and detected along the square wave-shaped path.

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