JP2005055237A - Ultrasonic inspection method of spot-weld zone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inspecting a spot-weld zone quickly and accurately. <P>SOLUTION: An ultrasonic signal is imparted to the weld zone, while scanning a line-focusing probe, in the direction crossing at least in the two or more directions on the spot-weld zone, and existence of a defect on the weld zone is inspected from a reflection pattern of the signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a spot welding inspection method, and more particularly, to a non-destructive spot welding portion inspection method using ultrasonic waves.

  In the automobile industry, spot welding is frequently used, such as welding a chassis and a door. It is necessary to inspect whether the spot-welded part is welded as intended, but until now, in the automobile industry, there were few nondestructive inspection methods available at the production site and it took time. It was sought after.

  As a method for inspecting the spot portion with ultrasonic waves, Patent Document 1 exists. However, in the technique described in Patent Document 1, it is necessary to repeat scanning of the ultrasonic probe several times, and there is a problem that the analysis takes time.

JP 2000-146828 A

  The object of the present invention is to solve the problems of the existing techniques. An object of the present invention is to provide a method for quickly and accurately inspecting spot welds.

  That is, according to the present invention, an ultrasonic signal is given to a welded portion while scanning the line-focusing probe in at least two intersecting directions on the spot welded portion, and the presence or absence of a defect in the welded portion is determined from the reflected pattern of the signal. This is an ultrasonic inspection method for a spot welded portion.

The width of the tip of the line focusing probe is preferably equal to or wider than the width of the spot weld.

The two intersecting directions are preferably perpendicular directions.

  According to the method of the present invention, since the state of the spot welded portion can be monitored by at least two scans, the shape of the spot welded portion, the joint diameter, the donut shape, and the presence or absence of a crescent weld failure are clearly and easily not detected. By destruction, it can be grasped in a short time such as 2 to 3 seconds. For this reason, quality control of a welded product can be performed online at a welding site of a product that frequently uses spot welding such as an automobile. An apparatus using a water-sealed container can also be used as a method to replace the chisel test and the torsion test that are performed by sampling inspection.

The present invention will be described in detail.
FIG. 1 is a schematic view showing an example of the ultrasonic inspection method of the present invention. In FIG. 1, reference numeral 1 denotes an ultrasonic inspection apparatus, which includes a probe 6, a probe holder 7, and a probe holder fixing / moving member 8. Reference numeral 2 denotes a test piece having a spot weld 3. The test piece is fixed by a fixing member 9 while being filled with water 5 in the container 4.

  Materials that can be inspected by the method of the present invention are spot welded metal materials, preferably metal plates. The metal material is not particularly specified, and examples thereof include iron, titanium, aluminum, copper, and alloys of these metals, such as brass and stainless steel. Among these metallic materials, the method of the present invention can preferably inspect the presence of defects for steel, particularly steel plates.

  As is well known, the spot welded portion that is the object of the inspection of the present invention is that the above-mentioned metals, or one metal and another type of metal are sandwiched between electrodes, a large current is passed, and the metal is heated and melted with its electric energy. The part welded by the spot welding method to weld. The spot welded portion is formed of a nugget portion and a corona bond portion around the nugget portion.

  In the inspection method of the present invention, spot welds are inspected using ultrasonic waves. The ultrasonic wave used for the inspection is usually 0.1 to 100 MHz, preferably 1 to 10 MHz.

  In the inspection method of the present invention, the presence or absence of a defect in the spot weld is inspected using a probe. In the method of the present invention, a special probe is used as the probe. 2A is a perspective view showing an example of a probe used in a conventional ultrasonic inspection method, and FIG. 2B is a perspective view showing an example of a probe used in the ultrasonic inspection method of the present invention. is there. The feature of the probe used in the method of the present invention is that it is not a point focusing terminal like a conventional probe but a line focusing terminal. The probe generates ultrasonic waves from the tip and moves while sliding on the surface of the test piece.

  The probe is fixed to the holder as shown in FIG. 1, and is electrically coupled to a power source, an ultrasonic generator, and an ultrasonic receiver (not shown).

  The spot welded portion is inspected by relatively moving (scanning) the sample and the probe. The scanning direction is preferably moved in a direction perpendicular to the longitudinal direction of the probe, that is, when the probe moves relatively, the measurement portion formed on the sample has a maximum area. For relative movement, the sample plate may be moved, the probe may be moved, or the combined use or scanning may be performed alternately.

  The method of the present invention is characterized in that this scanning is performed in a direction crossing. That is, when the first scan is performed in the longitudinal direction of the test sample, the next scan is performed in a direction intersecting the direction, preferably as shown in FIG. It is desirable to scan in directions that are perpendicular to each other.

  In the scanning in the intersecting direction, if the probe is moved in the first direction and the measurement sample is moved in the second direction, the structure of the entire measuring apparatus becomes simple. When the scanning direction changes from the first direction to the second direction, the probe holder has a function that the probe holder can rotate the probe so that its longitudinal direction is perpendicular to the second direction. It is desirable to have.

  By detecting the probe in such a crossing direction at a position crossing the spot welded portion of the sample, the welded portion can be clearly inspected two-dimensionally as shown below.

  The relative speed between the probe and the measurement sample during scanning is preferably between 1 and 20 mm / second. In scanning, the sample and / or the probe may be moved continuously, intermittently moved and stopped, or may be rotated.

  The ultrasonic wave generated from the probe passes through the sample, is reflected by the sample fixing base, passes through the sample again, passes through the probe again, and is output to the ultrasonic measurement device. This reflected wave can be monitored or recorded with a digital oscilloscope, for example.

  In the inspection, first, an ultrasonic probe is applied to the non-welded portion, and the reflected wave from the upper surface of the upper plate and the first reflected wave (longitudinal wave) of the upper plate are measured. Next, the ultrasonic probe is scanned across the spot weld and the captured bottom plate bottom reflected wave and bottom plate bottom reflected wave are measured, as shown in the examples below. Can be inspected.

  The output voltage value [reflected wave peak] measured by the above method and the movement amount of the ultrasonic probe 6 detected by the movement amount measuring device 8 are preferably stored as a pair of data in the storage device.

  As one embodiment of the present inspection method, the ultrasonic inspection can be performed in water using a water immersion type ultrasonic probe. The sample subjected to spot welding is fixed on a fixing jig 9 in the water tank 4. If a water-sealed container having a measuring part as a film is used instead of the water tank, the test object can be measured without being put in the water tank.

  When carrying out the inspection method of the present invention at the manufacturing site, if an abnormality is observed in the shape of the monitored ultrasonic diagram, the lighting of the lamp, discoloration, or the occurrence of defective products to the inspector with a warning device such as a buzzer. You can also let them know.

  EXAMPLES Next, although an Example is given and this invention is demonstrated concretely, this invention is not restrict | limited at all to these Examples.

(apparatus)
The apparatus shown in FIG. 1 was used.

(sample)
Material Steel plate thickness 0.8-1.2mm
Spot welding method The diameter of the welded weld is 3 to 7 mm in two layers using an AC spot welder.

(Measurement condition)
Ultrasonic Hz 10MHz
Method of relative movement Length of tip of intermittent motion probe of 0.072mm driven by stepping motor 10mm
Relative moving speed 1.8mm / sec reflected wave monitoring method Output voltage is measured using a digital oscilloscope.

(Measurement result)
The result of the monitor is shown in FIG. FIG. 4 is a graph of the output distance detected by the ultrasonic probe on the horizontal axis on the probe moving distance and the vertical axis on the vertical axis. A trapezoidal monitor diagram was obtained when the spot weld was well welded.

  The same procedure as in Example 2 was performed except that a sample with poor spot welding was used instead of the sample in Example 2. The obtained monitoring results are shown in FIG. When the spot welded part was poorly welded, a monitor figure with the center part depressed was obtained.

  Non-destructive inspection useful for inspecting whether spot-welded parts are welded as intended in automobile parts assembly, etc. It can be used for process management at the production site.

FIG. 1 is a schematic view showing an example of an inspection apparatus according to the present invention. FIG. 2 is a perspective view showing the shape of the probe. (A) Probe used in the conventional ultrasonic inspection method (B) Probe used in the ultrasonic inspection method of the present invention FIG. 3 is a diagram showing the relationship between the position of the weld and the scanning direction of the probe. FIG. 4 is a graph showing an example of the monitoring result of the spot welding good portion. FIG. 5 is a graph showing an example of a monitoring result of a spot welding defective portion.

Explanation of symbols

1: Ultrasonic inspection apparatus 2; Test piece 3: Spot welding part 4: Container 5: Water 6: Probe 7: Probe holder 8: Probe holder fixing / moving member

Claims (3)

  An ultrasonic signal is given to the welded part while scanning the line-focusing probe in at least two intersecting directions on the spot welded part, and the presence or absence of a defect in the welded part is inspected from the reflected pattern of the signal. The ultrasonic inspection method of the spot welded part characterized. 2. The spot welded portion ultrasonic inspection method according to claim 1, wherein the width of the tip of the line focusing probe is equal to or wider than the width of the spot welded portion.   The ultrasonic inspection method for spot welds according to claim 1, wherein the two intersecting directions are perpendicular directions.