JP4380447B2 - Spot welding evaluation method and spot welding evaluation system - Google Patents

Description

  The present invention relates to a spot welding evaluation method and a spot welding evaluation system.

  The spot welding evaluation method is known to evaluate the strength of spot welding by the nugget diameter. Specific methods include press fitting between two spot-welded steel plates, peeling off the spot welded part, so-called flare inspection to directly measure the nugget diameter, and cutting the spot welded part to directly determine the nugget diameter. Individual destruction measurement such as cutting inspection to be measured is performed.

Nondestructive measurement techniques relating to spot welding are those using ultrasonic waves (Japanese Patent Laid-Open Nos. 62-119453 and 4-265854), those using vibration (Japanese Patent Laid-Open No. 9-171007), and intermittent light. Various proposals have been made, such as detecting a sound wave accompanying irradiation (Japanese Patent Laid-Open No. 3-2659) and detecting a reflected wave of an elastic wave emitted from a welding electrode (Japanese Patent Laid-Open No. 4-40359). Japanese Patent Laid-Open No. 2001-165911 discloses a diameter of an annular high-inductance portion at the periphery of a nugget of a spot welded portion measured when a magnetic field line is passed through a pot welded portion, and the high-inductance portion and the nugget central portion. Are used to express each variable as a predicted value of the nugget diameter with a discriminant and set a threshold value for discriminating whether the nugget diameter is good or bad.
JP 2001-165911 A

  The chisel inspection can evaluate the strength of spot welding for those subjected to fracture measurement, but cannot directly evaluate the strength of spot welding for those not subjected to fracture measurement. In recent years, high-tensile (high-tensile steel) materials are often used to reduce the weight of automobile bodies, but the spot-welded part of high-tensile material is harder than the part welded with normal steel plates. It was unsuitable for performing an inspection by punching on the production line.

  Therefore, it is desired to establish a spot welding evaluation method capable of performing individual evaluation of spot welding by nondestructive inspection. Non-destructive inspection is disclosed in Japanese Patent Application Laid-Open No. 2001-165911. However, in view of equipment cost and workability, an inspection method that can be easily inspected with simple equipment and has high reliability is desirable. .

  In the spot welding evaluation method according to the present invention, a pair of electrodes in which a recess is formed on the surface of one of the first electrode and the second electrode is used. In addition, as for a pair of electrode, the shape and magnitude | size of the recessed part formed in which electrode the recessed part is formed in the surface of an electrode are arbitrary. Using such a pair of electrodes, as shown in FIG. 2, a plurality of metal bodies (in the illustrated example, two metal bodies 1 and 2) are overlapped and sandwiched between such a pair of electrodes 3 and 4, and added. When spot welding is performed by applying pressure and joining, a convex portion 6 is formed on the upper surface of the upper metal body 1 corresponding to the concave portion 5 formed on the surface of the upper electrode 3.

  As shown in FIG. 1, the present inventors paid attention to the convex portion 6 and examined the correlation between the nugget 7 diameter (nugget diameter) and tensile shear strength (TSS). As a result, there was a correlation between them, and the knowledge that the nugget diameter and the tensile shear strength (TSS) can be estimated from the height of the convex portion 6 was obtained.

The spot welding evaluation method according to the present invention is devised based on the knowledge obtained here. That is, in the spot welding evaluation method in which a plurality of metal bodies are overlapped, sandwiched between a pair of electrodes composed of a first electrode and a second electrode, and spot welding joined by applying pressure is non-destructive, Spot welding is performed using a pair of electrodes in which a concave portion is formed on the surface of one of the electrode and the second electrode, and the height of the convex portion formed in the spot welded portion by the electrode in which the concave portion is formed. The quality of spot welding is evaluated based on this. Here, the evaluation of the quality of the spot welding is the data indicating the correlation between the height of the convex portion formed in the spot welded portion of the sample created by performing spot welding in advance using a pair of electrodes and the nugget diameter, or The determination is based on data indicating the correlation between the height of the convex portion formed in the spot welded portion of the sample and the tensile shear strength of the spot welded portion.

  According to the spot welding evaluation method according to the present invention, the quality of spot welding is evaluated based on the height of the convex portion formed in the spot welded portion by the electrode in which the concave portion is formed. Can be evaluated. Moreover, since the quality of spot welding can be evaluated only by measuring the height of the convex part formed in a spot welding part also about the site | part which joined the high tensile material, spot welding evaluation work becomes easy. . In addition, because spot welding evaluation work is easy, it is possible to manage product quality with higher accuracy without impairing work efficiency even if spot welding of all products is evaluated individually, regardless of spot inspection. It becomes possible. Further, in order to use this spot welding evaluation method, a pair of electrodes in which a concave portion is formed on the surface of one of the first electrode and the second electrode is used. According to such an electrode, , Spatter can be prevented.

  Hereinafter, a spot welding evaluation method according to an embodiment of the present invention will be described with reference to the drawings.

  In this spot welding evaluation method, as shown in FIG. 2, a pair of electrodes 3, 4 in which a recess 5 is formed on the surface of one of the first electrode and the second electrode is used. When spot welding is performed by sandwiching the pair of electrodes 3 and 4 and joining them by applying pressure, as shown in FIG. 2, the metal body 1 is raised in the recess 5 formed on the surface of the upper electrode 3. Thus, the convex portion 6 is formed on the upper surface of the metal body 1.

  This spot welding evaluation method determines the quality of spot welding based on the correlation between the height of the convex portion 6 formed by such spot welding, the nugget diameter, and the tensile shear strength (TSS). . In this embodiment, basic data regarding the correlation among the height of the convex portion 6, the nugget diameter, and the tensile shear strength (TSS) is prepared in advance to determine whether or not the spot welding is acceptable. In order to apply the basic data to the actual production line, the same electrodes as those used in the actual production line are prepared in accordance with the spot welding performed in the actual production line. And a spot welder having the same or the same function as above, and made based on a sample which was spot-welded by stacking metal plates of the same material as the actually manufactured product and the same thickness.

  To create the basic data, first, change the conditions (current, energization time, applied pressure), and create multiple samples. Next, for each sample, as shown in FIG. 1, the height of the convex portion 6 formed on the surface of the metal body is measured. And some of the samples prepared under the same conditions were measured for tensile shear strength (TSS) by checking the tensile strength of welded metal bodies in opposite directions, and the others were nugget diameters by means of a chisel inspection or cutting inspection. Measure. Thereby, between samples prepared under the same conditions, the correlation between the height of the convex portion and the tensile shear strength (TSS), the correlation between the height of the convex portion and the nugget diameter, and the tensile shear strength (TSS) and the nugget. Each of the diameter correlations is obtained.

  FIG. 3 shows an example of data showing the correlation between the height of the convex portion and the nugget diameter, FIG. 4 shows an example of data showing the correlation between the height of the convex portion and the tensile shear strength (TSS), and FIG. One example of data indicating the correlation between the nugget diameter and the tensile shear strength (TSS) is shown.

  In this embodiment, as shown in FIG. 2, an electrode in which a cylindrical recess having a predetermined diameter (3 mm and 5 mm) is formed as a recess 5 on the surface of the upper electrode 3 of the pair of upper and lower electrodes 3 and 4. Used. In the correlation diagrams of FIGS. 3 to 5, data was taken with two types of electrodes, with the diameter of the cylindrical recess formed as the recess 5 on the surface of the electrode 3 being 3 mm and 5 mm. Each of the applied pressure is 250 kgf (about 2.45 kN) and 150 kgf (about 1.47 kN), the current value is changed between 5 kA and 13 kA, the energization time is changed between 4 cycles and 10 cycles and the energy of spot welding is changed. Samples with different heights, nugget diameters, and tensile shear strength (TSS) were prepared. A plurality of samples were prepared for each different condition. In this embodiment, spot welding is performed with an alternating current having a frequency of 60 Hz, cycle is a unit for setting the energization time, and 1 cycle is 1/60 sec.

  Next, the height of the convex portion 6 formed on the surface of the metal body was measured for each sample, and some of the samples prepared under the same conditions were measured for tensile shear strength (TSS), and some of the other samples were rivets. By measuring the nugget diameter by inspection or cutting inspection, the correlation between the height of the convex portion and the tensile shear strength (TSS) between the samples prepared under the same conditions, the correlation between the height of the convex portion and the nugget diameter, and The correlation between the tensile shear strength (TSS) and the nugget diameter was obtained. The correlation diagrams of FIGS. 3 to 5 show the correlation between the height of the convex portion and the tensile shear strength (TSS) between samples prepared under the same conditions, the correlation between the height of the convex portion and the nugget diameter, and The correlation between the tensile shear strength (TSS) and the nugget diameter is calculated and shown in each coordinate.

  As a result, the height, nugget diameter, and tensile shear strength (TSS) of the convex portion formed in the spot weld are different by changing the welding conditions, and the height of the convex portion, the nugget diameter, It was also found that there was a correlation between the tensile shear strength (TSS).

  In the actual production line, the height of the convex part formed on the spot welded part of the product is measured, and the measurement result is compared with the above correlation, so that the nugget diameter and the tensile shear strength are calculated from the height of the convex part. (TSS) can be estimated and the quality of spot welding can be evaluated.

  According to this spot welding evaluation method, in an actual production line, a pair of electrodes 3, 4 in which a recess 5 is formed on the surface of one of the first electrode 3 and the second electrode 4, a recess is formed. Since the quality of spot welding is evaluated based on the height of the convex portion 6 formed in the spot welded portion by the electrode on which 5 is formed, individual evaluation of spot welding by nondestructive inspection can be performed. Moreover, since the quality of spot welding can be evaluated only by measuring the height of the convex part 6 formed in the spot welded part even at the site where the high-tensile material is joined, the spot welding evaluation work is easy. become. In order to use this spot welding evaluation method, a pair of electrodes 3 and 4 in which a recess 5 is formed on the surface of one of the first electrode 3 and the second electrode 4 are used. Such an electrode can prevent the occurrence of sputtering.

  The spot welding evaluation method according to one embodiment of the present invention has been described above, but the spot welding evaluation method according to the present invention is not limited to the above.

  The above-described correlation between the height of the convex portion 6 and the nugget diameter, the correlation between the height of the convex portion 6 and the tensile shear strength (TSS), and the basis showing the correlation between the nugget diameter and the tensile shear strength (TSS). The method of collecting data and the method of displaying the data are not limited to the above example.

  Further, if the material or thickness of the metal body used in the product is different, it is preferable to take basic data related to the above-described correlation and determine whether the spot welding is good or bad based on such basic data.

  In addition, since the correlation between nugget diameter and tensile shear strength (TSS) is generally known, the basic data used to determine whether or not spot welding is good is data indicating the correlation between the height of the protrusion and the nugget diameter. Only the data indicating the correlation between the height of the convex portion and the tensile shear strength (TSS) of the spot welded portion may be used.

  Further, the spot welding evaluation method described above can be embodied as a spot welding evaluation system using a computer. For example, in such a spot welding evaluation system, a recess is formed in a sample prepared by spot welding using a pair of electrodes in which a recess is formed on the surface of one of the first electrode and the second electrode. Data indicating the correlation between the height of the convex portion formed on the spot welded portion by the electrode formed and the nugget diameter, or the height of the convex portion formed on the spot welded portion of the sample and the tensile shear strength of the spot welded portion. A storage unit that stores at least one of the data indicating the correlation between the two, an input unit that inputs the height information of the convex portion formed on the spot welded part of the product by spot welding using a pair of electrodes, and an input The height information of the convex part input to the part, data indicating the correlation between the convex part height stored in the storage part and the nugget diameter, or the correlation between the convex part height and the tensile shear strength of the spot welded part Seki The on the basis of the data shown, can be that a judging section that judges acceptability of spot welding.

  According to such a spot welding evaluation system, spot welding is performed using a pair of electrodes, and the height of the convex portion formed on the spot welded portion of the product is measured. It is possible to determine whether the product is good or bad, and the determination work can be simplified.

  As a method of measuring the height of the convex portion formed in the spot welded portion, it is preferable to measure with a caliper, but for example, it may be measured using a dedicated measuring instrument 10 as shown in FIG. In FIG. 6, which shows the measuring device 10, 11 is a positioning portion that contacts the surface of the welded metal body and sets a reference position of the measuring device 10, and 12 is a contact type that advances and retreats relative to the positioning portion 11. A displacement sensor unit 13 indicates a measurement unit that measures a relative displacement amount between a reference position determined by the positioning unit 11 and the position of the tip of the displacement sensor unit 12. As shown in FIG. 6, the measuring instrument 10 has a positioning unit 11 in contact with the surface of the metal body, and a displacement sensor unit 12 is applied to the top of the convex portion 6 formed in the spot welded portion. 13, the height of the convex portion 6 is measured.

  In addition, a known shape recognition means using a computer is used to perform spot welding using a pair of electrodes to measure the height of the convex portion formed on the spot welded portion of the product and to input the measurement result. By combining and spot welding using a pair of electrodes, the height of the convex part formed in the spot welded part of the product is automatically measured, and the measurement result is automatically input, so that the spot is It is possible to further simplify the welding quality determination work.

  For example, in the measuring instrument 10 shown in FIG. 6, the measurement result measured by the measuring instrument 10 is automatically input from the measuring unit 13 to the input unit 14 of the computer as the height information of the convex portion 6. Configure. As known shape recognition means, those using a laser displacement sensor and those using an image processing measurement are known. The laser displacement sensor, for example, irradiates laser light so as to traverse or vertically cross a convex portion formed in a spot welded portion, and receives reflected light reflected from the surface of the spot welded portion and the metal body. It was formed in the spot welded part by combining the displacement measuring device that analyzes the reflected light received by the laser displacement sensor and measures the height of the convex part (displacement of the metal body surface) formed in the spot welded part You may make it obtain the height information of a convex part. In the image processing measurement, the height information of the convex portion is obtained based on an image obtained by photographing the convex portion formed on the spot welded portion.

It is sectional drawing of a spot weld part. It is a vertical side view which shows the process of the spot welding in the spot welding evaluation method which concerns on one Embodiment of this invention. It is a figure which shows an example of the correlation with the height of the convex part formed by spot welding, and a nugget diameter. It is a figure which shows an example of the correlation of the height of the convex part formed by spot welding, and tensile shear strength (TSS). It is a figure which shows an example of correlation with a nugget diameter and tensile shear strength (TSS). It is a figure which shows an example of the measuring device which measures the height of the convex part formed in the spot welding part.

Explanation of symbols

1, 2 Metal body 3, 4 Electrode 5 Concave part 6 Convex part 7 Nugget

Claims (2)

In a spot welding evaluation method in which a plurality of metal bodies are overlapped, sandwiched between a pair of electrodes consisting of a first electrode and a second electrode, and non-destructively inspecting the quality of spot welding that is joined by applying a pressure,
Spot welding is performed using a pair of electrodes in which a concave portion is formed on the surface of one of the first electrode and the second electrode, and the convex portion formed in the spot welded portion by the electrode in which the concave portion is formed. to evaluate the quality of the spot welding on the basis of the height,
The evaluation of the quality of the spot welding is data indicating the correlation between the height of the convex portion formed in the spot welded portion of the sample created by performing spot welding in advance using the pair of electrodes and the nugget diameter, or A spot welding evaluation method, wherein the determination is based on data indicating a correlation between a height of a convex portion formed on a spot welded portion of the sample and a tensile shear strength of the spot welded portion . A spot welding evaluation system using a computer,
In a sample prepared by spot welding using a pair of electrodes in which a recess is formed on the surface of one of the first electrode and the second electrode, the electrode having the recess is formed in a spot weld. At least data indicating a correlation between the height of the projected portion and the nugget diameter, or data indicating a correlation between the height of the projection formed on the spot welded portion of the sample and the tensile shear strength of the spot welded portion A storage unit storing one of them,
An input unit for performing spot welding using the pair of electrodes and inputting height information of a convex portion formed in a spot welded part of the product;
The height information of the convex part input to the input part, the data indicating the correlation between the convex part height and the nugget diameter stored in the storage part, or the tensile shear strength of the convex part height and the spot welded part A spot welding evaluation system comprising: a determination unit that determines whether the spot welding is good or bad based on data indicating a correlation with the spot welding.

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