Inspection method for dissimilar metal connection joint, inspection device for dissimilar metal connection joint, welding method, and welding system

Abstract

To provide an inspection method for a dissimilar metal connection joint, an inspection device for the dissimilar metal connection joint, a welding method, and a welding system capable of highly reliabily inspecting a joint strength when dissimilar metals are spot-welded, performing instantaneous inspection after welding, and facilitating automation.SOLUTION: This inspection method for the dissimilar metal connection joint in which a plate set stacking at least one steel first member 11 having a through-hole 11a in a plate thickness direction and a non-iron metal second member 13 together is spot-welded at the position of the through-hole 11a measures the projecting height H of a welded metal 15 formed through spot-welding and projecting from the surface of the first member 11 opposite to the second member 13, and determines the welding state of the spot-welding according to the measured projection height H.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for inspecting a dissimilar metal joint, a welding method, and a welding system. [Background technology]

[0002] Conventionally, there has been a demand for improving the safety of passengers in vehicles, and the strength of the vehicle body has been improved for this purpose. On the other hand, against the background of the worsening of the global warming problem, the movement to improve the fuel efficiency of automobiles is accelerating. It is known that reducing the weight of the vehicle body is effective for improving fuel efficiency. As one measure for reducing the weight of the vehicle body, attempts to replace steel, which is currently the main material, with light metals such as aluminum and magnesium, which are lightweight materials, are being actively promoted. In order to combine steel and light metals, it is inevitable to provide a place where they are joined, but compared to the conventional welding that joins the same type of materials, welding dissimilar materials together is often difficult, and it is important to ensure the reliability and soundness of the welded part.

[0003] In general, it is required to inspect welded joints of structures including spot welds after welding to ensure the reliability and soundness of the joints. This is also true in the field of dissimilar material joining. For example, dissimilar metal arc spot welding (hereinafter also referred to as dissimilar arc spot welding: DASW) has been developed as a dissimilar material joining method of iron and aluminum using aluminum welding wire (see, for example, Patent Document 1). In addition to this, spot welding methods of dissimilar materials using laser welding, in which a laser beam is used as a heat source and a welding wire is supplied to a laser beam irradiated portion, and hybrid welding, in which a laser and an arc are used in combination, are also being studied. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 52-114446 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the above-mentioned spot welding methods such as DASW, laser welding, and hybrid welding, it is possible to firmly join steel and light metals such as aluminum. However, a standard joint inspection method has not yet been established for these joining methods and joining mechanisms. On the other hand, there are several inspection methods for joints by resistance spot welding that have been widely used in the past, and non-destructive inspection of welded parts by destructive testing using a chisel and ultrasonic testing (UT) are known. In addition, non-destructive inspection such as radiographic testing (RT) and magnetic particle testing (MT) are also known. However, there are the following problems in applying these methods to DASW.

[0006] In the case of destructive testing using a chisel, damage to the weld and base material is unavoidable, and it is difficult to completely restore the weld to its post-weld state. In the case of ultrasonic testing, there are problems such as the difficulty of contacting the probe with the DASW weld because of the protrusions, the difficulty of contacting the probe at high temperatures after welding, and the difficulty of immediate inspection. In the case of aluminum weld metal, there are often fine blowholes in the weld metal, making it difficult to obtain the desired reflected waves. Laser UT can inspect welds without contacting them without using a probe, but the above-mentioned problems remain regarding blowholes. In addition, the propagation characteristics of ultrasonic waves in welds are temperature-dependent, making it difficult to apply it to immediate inspection after welding. In radiographic testing, the introduction of equipment that takes safety into consideration is essential, and although it is suitable for checking internal defects, it is difficult to determine the important nugget diameter and excess reinforcement shape. Magnetic flaw testing is a method used for magnetic steel, and the desired inspection results cannot be obtained for dissimilar metal joints such as DASW.

[0007] Therefore, an object of the present invention is to provide an inspection method, an inspection device, a welding method, and a welding system for dissimilar metal joints that can inspect the joint strength with high reliability when spot welding dissimilar metals together, and that can perform inspection immediately after welding and can be easily automated. [Means for solving the problem]

[0008] The present invention comprises the following configurations. (1) A method for inspecting a dissimilar metal joint, in which at least one steel first member having a through hole in the thickness direction and a non-ferrous metal second member are stacked on top of each other, and the sheet assembly is spot-welded at the position of the through hole, measuring a protruding height of a weld metal formed by the spot welding from a surface of the first member opposite to the second member; determining a welding condition of the spot welding in accordance with the measured protruding height; Inspection methods for dissimilar metal joints. (2) a welding process in which at least one steel first member having a through hole in the plate thickness direction and a non-ferrous metal second member are overlapped with each other to form a dissimilar metal joint by spot welding the plate assembly at the positions of the through holes; a measuring step of measuring at least one of a protruding height of a weld metal formed by the spot welding protruding from a surface of the first member opposite to the second member and a protruding height of a weld metal formed by the spot welding protruding from a back surface of the second member opposite to the first member; a determination step of determining a welding condition of the spot welding based on the measured protrusion height; a repairing step of repairing a welding position of the spot weld when the welding state of the spot weld is determined to be defective; A welding method comprising the steps of: (3) An inspection device for a dissimilar metal joint in which at least one steel first member having a through hole in the plate thickness direction and a non-ferrous metal second member are stacked on top of each other and spot-welded at the positions of the through holes, a height measuring unit that measures a protruding height of a weld metal formed by the spot welding from a surface of the first member opposite to the second member; a determination unit that determines a welding state of the spot welding based on the measured height; An inspection device for dissimilar metal joints comprising: (4) An inspection device for a dissimilar metal joint according to (3), a welding device that joins the first member and the second member by the spot welding to form the dissimilar metal joint; Equipped with a repair function for repairing a welding position of the spot weld that is determined to be defective by driving the welding device when the welding state of the spot weld is determined to be defective; Welding system. Effect of the Invention

[0009] According to the present invention, when dissimilar metals are spot-welded together, the joint strength can be inspected with high reliability. Moreover, the inspection can be performed immediately after welding, and automation can be easily achieved. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing a main portion of a dissimilar metal joint. [Diagram 2] FIG. 2 is a plan view of the dissimilar metal joint shown in FIG. [Figure 3A] FIG. 3A is a process explanatory view showing a procedure for forming a dissimilar metal joint between a steel plate and an aluminum plate having a through hole. [Figure 3B] FIG. 3B is a process explanatory view showing a procedure for forming a dissimilar metal joint between a steel plate having a through hole and an aluminum plate. [Figure 3C] FIG. 3C is a process explanatory view showing a procedure for forming a dissimilar metal joint between a steel plate having a through hole and an aluminum plate. [Figure 4] FIG. 4 is a schematic diagram of a welding system including a welding robot equipped with a height measuring device. [Diagram 5]FIG. 5 is an explanatory diagram that shows a schematic view of a state in which the height of a dissimilar metal joint of a joined body is measured by a height measuring device. [Figure 6] FIG. 6 is a flow chart showing the basic steps of the inspection method for a dissimilar metal joint. [Figure 7] FIG. 7 is an explanatory diagram that shows a schematic view of how the height of a dissimilar metal joint of a joint body is measured from the front and back sides by a height measuring device. [Figure 8A] FIG. 8A is a cross-sectional photograph of a cut surface of a dissimilar metal joint determined to be normal. [Figure 8B] FIG. 8B is a cross-sectional photograph of a cut surface of a dissimilar metal joint determined to be defective. [Figure 9] FIG. 9 is a graph showing a height profile obtained from measurement data from a height measuring device. [Figure 10] FIG. 10 is a graph showing the height profile and the reference height distribution. [Figure 11] FIG. 11 is a graph showing the height profile and the reference height distribution. [Figure 12] FIG. 12 is an explanatory diagram showing a height profile when the through hole of the first member is measured before welding. [Figure 13] FIG. 13 is an explanatory diagram showing a reference height distribution created based on the center line shown in FIG. [Figure 14] FIG. 14 is an explanatory diagram showing a comparison between the measured height profile and the reference height distribution shown in FIG. [Figure 15] FIG. 15 is an explanatory diagram showing a comparison between the measured height profile and the reference height distribution shown in FIG. [Figure 16] FIG. 16 is an explanatory diagram showing a height profile when the protruding shape of the welded portion is measured after welding. [Figure 17] FIG. 17 is an explanatory diagram showing a reference height distribution created based on the center line shown in FIG. [Figure 18] FIG. 18 is an explanatory diagram showing how the positional relationship of representative points extracted from a measured height profile is compared with a reference. [Figure 19] FIG. 19 is an explanatory diagram showing how the positional relationship of representative points extracted from a measured height profile is compared with a reference. [Figure 20] FIG. 20 is an explanatory diagram showing a height profile of the weld metal measured after welding and a height profile measured at the through hole, which is the welding position, before welding. [Figure 21] FIG. 21 is an explanatory diagram illustrating the volume of the weld metal formed in the through hole of the first member after welding. [Figure 22] FIG. 22 is an explanatory diagram showing a cross-sectional view and a front view of a weld metal that joins a first member and a second member. [Figure 23] FIG. 23 is an explanatory diagram showing the outer edge shape of the surface reinforcement of the weld metal in the XY plane. [Figure 24] FIG. 24 is an explanatory diagram showing the outer edge shape of the surface reinforcement of the weld metal in the XY plane. [Diagram 25] FIG. 25 is a flow chart showing an inspection procedure including detection of the positions of preliminary holes, welding and height measurement, and a process of repairing welds determined to be defective. [Figure 26] FIG. 26 is a flow chart showing an inspection procedure in which the inspection shown in FIG. 25 is modified so that the inspection is performed for a plurality of points at once instead of one point at a time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In this specification, a dissimilar metal joint in which a steel plate having a through hole and a non-ferrous aluminum plate are overlapped and joined to each other by arc spot welding (MIG welding) will be described as an example, but the structure and materials of the joint are not limited to this and various modifications are possible.

[0012] <Configuration of dissimilar metal joints> FIG. 1 is a cross-sectional view showing a main part of a dissimilar metal joint. The dissimilar metal joint 100 has a first member 11 made of a steel plate and having a through hole 11a in the plate thickness direction, a second member 13 made of a non-ferrous metal, and a weld metal 15. The second member 13 shown here is made of aluminum or an aluminum alloy (hereinafter also referred to as an aluminum material). The first member 11 and the second member 13 are not limited to plate materials, and may be die-cast or extruded materials. The weld metal 15 is formed by arc spot welding, which will be described later, and joins the overlapped first member 11 and second member 13 to each other. This weld metal 15 is formed by melting a joining auxiliary member (welding wire) and is joined to the second member 13. The weld metal 15 of this configuration forms a back wave (back excess) from the back surface (lower surface) of the second member 13, but the back excess may not be provided. The welding wire forming the joining auxiliary member is preferably made of the same material as the second member 13. In this configuration, the welding wire is made of an aluminum alloy.

[0013] 2 is a plan view of the dissimilar metal joint 100 shown in FIG. 1. The weld metal 15 is formed by arc spot welding in a substantially circular shape in a plan view, and has a front weld 15a that spreads over the surface (upper surface) of the first member 11. The weld metal 15 may also have a back weld 15b that penetrates the second member 13 from the through hole 11a of the first member 11 and protrudes from the back surface of the second member 13. In this way, the first member 11 is sandwiched between the front weld 15a arranged on one end side in the plate thickness direction and the second member 13 arranged on the other end side of the first member 11 and connected to the weld metal 15, and is joined to the second member 13. As described above, the formation of the back weld 15b is optional, and the weld metal 15 does not have to protrude from the second member 13.

[0014] The dissimilar metal joint 100 can obtain sufficient joint strength even without the back weld 15b. In addition, omitting the back weld 15b can contribute to reducing the weight of the joint. In addition, when the back weld 15b is provided, the larger the back weld 15b is, the higher the joint strength can be improved, but there is a possibility of interference with other parts, an increase in consumption of consumables, and an increase in weight, so the above items may be balanced according to the situation.

[0015] The first member 11 may be a single steel plate or a plate assembly in which multiple steel plates having through holes at the same position are stacked. The shape of the through holes 11a is not limited to a circle and can be any shape. The second member 13 may be made of other light metals such as magnesium, magnesium alloys, etc., other than aluminum material.

[0016] <Welding of dissimilar metal joints> 3A to 3C are process explanatory views showing the procedure for forming a dissimilar metal joint 100 between a steel plate having a through hole and an aluminum plate. To form the dissimilar metal joint 100 shown in Fig. 1 and Fig. 2, first, a first member 11 and a second member 13 are overlapped in the plate thickness direction as shown in Fig. 3A.

[0017] As shown in FIG. 3B, a welding torch 17 is placed toward a recess formed by the through hole 11a (also called a preliminary hole) of the overlapped first member 11 and the second member 13, and an arc Ak is generated from the tip of the welding wire 19 held by the welding torch 17 to melt the welding wire 19. This arc welding is performed in a shielding gas G atmosphere. The part exposed to the inside of the preliminary hole of the second member 13 is melted by the arc Ak, and a through portion 13a penetrating in the plate thickness direction is formed as shown in FIG. 3C. In this way, the preliminary hole of the first member 11 and the through portion 13a of the second member 13 are filled with the weld metal of the welding wire 19 melted and the molten metal of the second member 13 melted. In addition, a surface excess fill 15a is formed on the outside of the through hole 11a of the first member 11 by the molten metal spreading radially outward.

[0018] As the above-mentioned arc welding, (a) consumable electrode gas-shielded arc welding is used, but other welding methods such as (b) non-gas arc welding, (c) consumable electrode gas tungsten arc welding, (d) plasma arc welding, and (e) shielded metal arc welding may also be used.

[0019] (a) Consumable gas-shielded arc welding is a welding method commonly known as MAG (Metal Active Gas) welding or MIG (Metal Inert Gas) welding. It uses a solid wire or flux-cored wire as a filler and an arc-generating consumable electrode, and isolates the weld from the atmosphere with an inert gas such as CO2, Ar or He to form a sound weld. (b) Non-gas arc welding, also known as self-shielded arc welding, uses a special flux-cored welding wire as both a filler and an arc-generating electrode. This welding method does not require shielding gas G and produces a sounder weld. (c) Gas tungsten arc welding is a type of gas-shielded arc welding method that uses a non-consumable electrode and is generally called TIG (Tungsten Inert Gas) welding. Inert gases such as Ar or He are used as the shielding gas G. An arc is generated between the tungsten electrode and the base material, and the filler wire is fed laterally into the arc. Generally, no current is passed through the filler wire, but there is also a hot-wire type TIG in which electricity is passed through the filler wire to increase the melting rate. In this case, no arc is generated in the filler wire. (d) Plasma arc welding is a welding method that uses the same principle as TIG, but it uses a double gas system and high speed to constrict the arc and increase the arc force. (e) Shielded metal arc welding is an arc welding method that uses a shielded metal arc welding rod with a flux coated metal core as a filler, eliminating the need for shielding gas. Although the spot welding using an arc will be described here, the spot welding may be laser welding or hybrid welding using both a laser and an arc, and the spot welding may be performed with better controllability and higher accuracy.

[0020] <Inspection of dissimilar metal joints> As a height measuring device for measuring the height of the weld metal 15 after spot welding as described above, a contact height gauge, a non-contact laser displacement meter, an image sensor (camera), etc. can be used. With an image sensor, the height may be calculated using image data captured from multiple directions using one sensor, or the height may be calculated from information from two or more sensors, such as a twin-lens camera or a 3D camera. It is difficult to bring a contact height gauge into contact with a high-temperature part and it is not suitable for measurement immediately after welding, but it is highly reliable because it can measure the height directly. On the other hand, a non-contact laser displacement meter, an image sensor, etc. can measure the high-temperature welded part immediately after welding.

[0021] Measurement methods include a method of measuring the displacement (height) of a single point, a method of measuring the displacement of multiple points by repeatedly measuring the displacement of a single point and shifting the measurement position, a method of acquiring the displacement distribution of a single line, a method of measuring the displacement distribution of multiple lines by repeatedly acquiring the displacement distribution of a single line and shifting the measurement position, and a method of acquiring three-dimensional displacement distribution all at once.

[0022] The various measurement data may be subjected to various filtering processes such as averaging filter and Gaussian filter, data thinning process, etc. as pre-processing in order to remove noise, speed up data processing, etc.

[0023] The measurement data obtained by height measurement may be two-dimensional (e.g., x-coordinate and height) data or three-dimensional (e.g., x, y-coordinate and height) data. The two-dimensional or three-dimensional data may be processed as is, or may be subjected to a process of reducing the dimension. For example, the height value on a specific line of the three-dimensional data may be extracted and converted into two-dimensional data, thereby simplifying the subsequent processing. The line may be selected by a diameter line passing through the center of the through hole 11a (preparatory hole) of the first member 11, a line having a preset height value, or a line selected by a specific algorithm. In addition, a plurality of lines including the various lines described above may be selected.

[0024] <Welding system> The height measuring device 21 may be mounted on a welding device that performs spot welding. 4 is a schematic diagram of a welding system 200 including a welding robot 23 provided with a height measuring device 21. The welding robot 23 shown as an example is a multi-axis robot, and a welding torch 17 is provided on a tip axis 25 of a robot arm.

[0025] Welding system 200 shown in Fig. 4 exemplifies a welding system that performs the above-mentioned (a) consumable electrode gas-shielded arc welding. This welding system 200 includes welding robot 23 equipped with height measuring device 21, control device 31, and determination device (determination unit) 33. Control device 31 has robot control unit 35 that drives welding robot 23, a power supply device (not shown), and welding control unit 37 that controls a wire feeder that feeds welding wire (not shown) to welding torch 17. Determination device 33 may be included in control device 31. Furthermore, height measuring device 21 may be arranged in welding robot 23, or may be fixed to a specific position, or may be arranged in another drive mechanism that operates height measuring device 21.

[0026] The position and posture of the welding torch 17 can be freely set by controlling the robot arm. The height measuring device 21 is supported on the tip shaft 25 of the robot arm or in the vicinity of the tip shaft 25, and the measurement position and measurement direction can be freely set by driving control of the robot arm, similar to the operation of the welding torch 17. The movement of the robot arm during measurement may be a movement to scan within a two-dimensional plane. In this way, when the height measuring device 21 is attached to the tip shaft 25 of the robot arm holding the welding torch 17, the welding robot 23 is provided with both welding and inspection functions, so that the installation space and capital investment costs can be reduced. In addition, inspection can be easily performed immediately after welding, which has the effect of shortening the tact time.

[0027] The welding robot 23 is not limited to a multi-axis robot, and may be a movable stage with one axis or two orthogonal axes. For example, the height measuring device 21 may be attached to a movable stage and the welded joint may be scanned for measurement. The height measuring device 21 may be fixed to a fixed part that is not movable, and the welded joint to be measured may be transported to the position of the height measuring device 21 for measurement.

[0028] The welding robot 23 and the control device 31 function as a welding device that performs spot welding. The welding robot 23, the control device 31, the judgment device 33, and the height measuring device 21 function as an inspection device that measures the protruding height of the weld metal of the welded portion and judges the welding condition.

[0029] FIG. 5 is an explanatory diagram showing a state where the height of the dissimilar metal joint 100 of the joint 27 is measured by the height measuring device 21. The joint 27 shown here is a joint of a first member 11, which is a steel material having a hat-shaped cross section perpendicular to the longitudinal direction, and a flat plate-shaped second member 13, which is an aluminum material. A pair of flanges 11b, 11c of the first member 11 have a plurality of through holes 11a, and dissimilar metal joints 100 are formed at a plurality of locations within the region where the flanges 11b, 11c and the second member 13 overlap. FIG. 5 shows a state where the dissimilar metal joint 100 is formed by spot welding at one location on one longitudinal end of the flange 11b on the near side.

[0030] <Testing Procedure> Next, a procedure for the inspection method of the above-mentioned dissimilar metal joint 100 will be described. Fig. 6 is a flow chart showing the basic procedure for the inspection method of the dissimilar metal joint 100. To explain using the example shown in Fig. 5, first, the first member 11 and the second member 13 are overlapped as described above, and spot welding is performed at the position of the through hole 11a (preparatory hole) based on a command from the control device 31 (Fig. 4) (S1).

[0031] Next, control device 31 causes height measuring device 21 to measure height H (FIG. 1) of weld metal 15 after spot welding (S2). Specifically, robot control unit 35 drives welding robot 23 to place height measuring device 21 at a height measurement position as shown in FIG. 5. Height measuring device 21 illustrated here is a laser displacement meter, which irradiates laser light LB onto a predetermined inspection area At including weld metal 15 at the measurement position, and measures height H of weld metal 15.

[0032] The measurement results from the height measuring device 21 are input to the determination device 33. The determination device 33 compares the obtained measurement data of the height H with a predetermined standard to determine whether or not the dissimilar metal joint 100 satisfies the desired conditions (S3). If the conditions are satisfied, the determination device 33 determines that the joint is normal (S4), and if the conditions are not satisfied, the determination device 33 determines that the joint is defective (S5).

[0033] The measurement data obtained here may be compared with a reference, or may be compared with a predetermined reference height, by taking the information on the height distribution of the weld metal 15 as information and comparing it with a predetermined threshold distribution, or by comparing the maximum value of the height H or the height at a preset position with a predetermined threshold. In addition to measuring the height H, the excess portion of the weld metal 15 may be extracted using the reflectance from the measurement position when a laser displacement meter is used, or the brightness of the captured image when an image sensor is used, and the excess portion may be included in the width W (FIG. 1) to determine whether it is normal or defective. Furthermore, by processing the measurement data using the first-order differential (difference), second-order differential (difference of differences), or the like, the feature amount of the shape of the weld metal 15 can be accurately captured, thereby enabling accurate determination.

[0034] As described above, in steps S3 to S5, the judgment device 33 judges the soundness of the dissimilar metal joint 100 using the measurement data or data appropriately processed after the measurement. In the judgment of the soundness, representative values ​​of various characteristic quantities such as the height H and width W of the front reinforcement 15a which is the reinforcement part of the weld metal 15 may be calculated from the data acquired by the height measuring device 21, and when each representative value satisfies a preset condition, the measured dissimilar metal joint 100 may be judged to be a good joint. The judgment condition at this time may be changed to an appropriate condition depending on the plate assembly used for the joint (conditions such as material type, heat treatment, plate thickness, etc.), the required joint performance, etc. For example, the maximum value of the height measurement data may be used as the height H of the reinforcement, or the height at the center of the width W of the reinforcement or any other specific position may be used. In addition, a plurality of heights or a distribution of heights may be used. Furthermore, in addition to the height H and width W of the reinforcement, values ​​such as the contact angle and center of gravity of the weld metal 15 may be used for the judgment. The volume of the excess portion of the weld metal 15 may be calculated from the acquired measurement data, and the determination may be made using the calculated volume value.

[0035] In this way, the above-mentioned method of inspecting the dissimilar metal joint 100 by measuring the height of the excess weld portion allows inspection without destroying the weld or base material, and allows immediate inspection even in a high temperature state immediately after welding. In addition, inspection can be performed easily and safely without requiring any particularly large-scale equipment, and can be easily automated.

[0036] FIG. 7 is an explanatory diagram showing a state where the height of the dissimilar metal joint 100 of the joint 27 is measured from the front side and the back side by the height measuring device 21. In the welded portion of the dissimilar metal joint 100 described above, in addition to measuring the height of the weld metal 15 on the front side (upper side of FIG. 7), the height of the weld metal 15 on the back side (lower side of FIG. 7) may be measured. That is, the protruding height h of the backside excess metal 15b of the weld metal 15 shown in FIG. 1 from the second member 13 may be measured and used to judge the soundness of the joint. In that case, more accurate inspection is possible. Also, the soundness of the joint can be judged only from the measurement data of the height h of the weld metal 15 on the back side. When measuring the height h of the back side of the welded portion, the height measuring device 21 for measuring the front side may be used for measurement, or a plurality of height measuring devices 21 may be prepared and the front side and the back side may be measured by separate measuring devices.

[0037] Furthermore, instead of measuring the height h of the back side of weld metal 15, the volume of front weld metal 15a, which is the excess portion of front weld metal 15, may be measured, and the shape of back weld metal 15b of back weld metal 15 may be estimated by taking into consideration this volume, the internal volume of through hole 11a, and the consumption of consumables (welding wire 19). Such estimation based on the volume of weld metal 15 is particularly useful when second member 13 is an aluminum extrusion, when the back side excess cannot be observed for structural reasons, when it is desired to perform inspection in a short time, when it is desired to reduce the cost of measuring equipment, etc.

[0038] When a large number of measurements of feature quantities such as the height of the weld metal 15 are performed, a learning model may be generated using machine learning, and the soundness of the welded joint may be judged using this learning model.

[0039] FIG. 8A is a cross-sectional photograph of a cut surface of a dissimilar metal joint 100 judged to be normal. FIG. 8B is a cross-sectional photograph of a cut surface of a dissimilar metal joint 100 judged to be defective. As shown in FIG. 8A, the dissimilar metal joint 100 is formed with a front excess weld 15a having a diameter larger than the through hole 11a of the first member 11, covering the through hole 11a and protruding in the plate thickness direction. The back excess weld 15b in this example is formed with a diameter larger than the diameter of the through part 13a of the second member 13 on the back side surface (the surface opposite to the first member 11 side) of the second member 13, and protruding in the plate thickness direction. This back excess weld 15b may be provided as necessary, and its shape may be arbitrary. Similarly, the shape of the front excess weld 15a may be arbitrary, and it may be omitted.

[0040] In this case, the front reinforcement 15a of the weld metal 15 adheres closely to the first member 11 without any gaps, improving the joint strength between the first member 11 and the second member 13. That is, in addition to the joint strength due to welding, an anchor effect is exhibited by sandwiching the first member 11 and the second member 13 between the front reinforcement 15a and the back reinforcement 15b, and a stronger joint is obtained against external stress in the plate thickness direction. Also, against shear force in the plate surface direction, high shear strength is obtained by the shaft portion 15c of the weld metal 15 penetrating the first member 11 and the second member 13.

[0041] 8B, when the weld metal 15 of the dissimilar metal joint 100 barely protrudes from the front side surface of the first member 11 and falls through the through hole 11a to the second member 13 side, the joint strength between the weld metal 15 and the first member 11 decreases. In this case, the above-mentioned anchor effect cannot be obtained, and the soundness of the joint becomes insufficient.

[0042] <Criteria for determining the soundness of dissimilar metal joints> The judgment device 33 can set judgment criteria for the soundness of the dissimilar metal joint 100 based on various criteria such as the width W of the surface reinforcement 15a, which is the reinforcement portion of the weld metal 15 shown in Figure 1 described above, and the height H from the surface of the first member 11.

[0043] FIG. 9 is a graph showing a height profile M obtained from measurement data from the height measuring instrument 21. The height profile M shown in FIG. 9 represents the measurement data output from the height measuring instrument 21 as a height distribution on a single axis (line) when the shape of the welded portion is measured by the height measuring instrument 21. As described above, the measurement data may be subjected to various filter processes, decimation processes, and the like. The height profile M represents the protruding shape of the weld metal 15 from the first member 11, and the width W and height H of the excess portion of the weld metal 15 can be obtained by calculation from the height profile M. Information such as the obtained width W and height H is used for comparison with the reference in step S3 of FIG. 6, that is, comparison with the reference width W0 and reference height H0.

[0044] FIG. 10 is a graph showing the height profile M and the reference height distribution SF. As described above, the soundness of the joint can be determined by extracting parameters such as the width W and height H of the weld metal 15 from the height profile M shown in FIG. 9, but in addition, it may also be determined by comparison with the reference height distribution SF. Here, a reference height distribution SF in which the reference height is set for each position is prepared, and the determination condition is whether the height profile M is equal to or higher than the height of the reference height distribution SF (M≧SF). The height profile M shown in FIG. 10 is higher than the reference height distribution SF at any position and satisfies the determination condition (M≧SF), so it is determined as "normal".

[0045] FIG. 11 is a graph showing the height profile M and the reference height distribution SF. The height profile M shown in FIG. 11 has a height of the protruding shape of the welded portion lower than the reference height distribution SF (region where M < SF). In this case, since the determination condition (M≧SF) is not satisfied, it is determined as "defective".

[0046] The above-mentioned reference height distribution SF can be set based on predetermined design conditions such as the diameter of the through-hole 11a of the dissimilar metal joint 100, the target height, the feeding speed of the welding wire, the welding current, the welding voltage, and the welding time. Further, the height of a sample product created in an ideal shape may be measured, and the reference height distribution may be set based on the measurement results of the sample product.

[0047] FIG. 12 is an explanatory diagram showing a height profile M when the through hole 11a of the first member 11 is measured before welding. FIG. 13 is an explanatory diagram showing a reference height distribution SF created based on the center line CL shown in FIG. 12. As shown in FIG. 12, the center line CL of the through hole 11a (preparatory hole) can be calculated from the measured height profile M. The reference height can be set within a predetermined range centered on the position of this center line CL, and the reference height distribution SF as shown in FIG. 13 can be set. In this way, the position of the preliminary hole may be measured and recorded before spot welding is performed, and the soundness of the joint may be judged by comparing the height profile M of the weld metal 15 measured after welding with the reference height distribution SF including the position information of the preliminary hole recorded in advance. In this case, even if the position of the preliminary hole is shifted, the position of the preliminary hole is actually measured and found, and a comparison and judgment are performed according to the amount of shift of the preliminary hole, so that the reliability of the judgment can be improved. Therefore, the influence of the position shift does not affect the judgment result.

[0048] 14 and 15 are explanatory diagrams showing a comparison between the measured height profile M and the reference height distribution SF shown in FIG. 13. As shown in FIG. 14, when the height profile M is equal to or greater than the reference height distribution SF, it is determined to be "normal". On the other hand, as shown in FIG. 15, when at least a part of the height profile M has a height lower than the reference height distribution SF, it is determined to be "defective". In this way, if the reference height distribution SF is set offset from the position of the original center line CL, accurate determination becomes difficult, but as described above, if the center position of the reference height distribution SF is set accurately, highly accurate determination can be stably performed.

[0049] FIG. 16 is an explanatory diagram showing a height profile M when the protruding shape of the welded portion is measured after welding. FIG. 17 is an explanatory diagram showing a reference height distribution SF created based on the position of the center line CL shown in FIG. 15. As shown in FIG. 16, the center line CL of the height distribution of the weld metal 15 can be calculated from the height profile M in which the protruding shape of the weld metal 15 from the first member 11 is measured. The reference height distribution SF shown in FIG. 17 can be set with the position of this center line CL as the center. In other words, the center line CL, which is the center position of the protruding shape of the weld metal 15 measured after welding, is obtained, and a threshold value is set with the center line CL as the center, so that the reference height distribution SF based on the position of the actually formed weld metal 15 can be set.

[0050] In the above-described judgment, the measured height profile M and the reference height distribution SF are judged over the entire profile, but it is also possible to make the comparison using specific representative points. 18 and 19 are explanatory diagrams showing how the positional relationship of the representative points extracted from the measured height profile M is compared with a reference. As shown in Fig. 18, a vertex P1, which is the maximum height of the protruding shape, and end points P2 and P3 of the rising parts on both sides of the vertex P1 are extracted from the measured height profile M.

[0051] Here, the height from the apex P1 of the height profile M to the point P4 where the line connecting the end points P2 and P3 intersects with the apex P1 in the vertical direction below the apex P1 is defined as the protruding height H. Also, the minimum height that is required to protrude vertically upward from the line connecting the end points P2 and P3 is defined as the reference height H. th The length of the line segment connecting the end points P2 and P3 is defined as the width W of the protruding weld metal, and the minimum allowable width of this width W is the reference width W th In other words, the judgment condition in this case is H ≥ H th , W ≧ W th It becomes.

[0052] When the height profile M shown in Figure 18 is evaluated in terms of height H and width W, the protruding height H is the reference height H th Higher than the standard width W th Since it is longer, H ≥ H th , W ≧ Wth On the other hand, in the height profile M shown in FIG. 19, the width W is equal to the reference width W th longer, but the protruding height H is equal to the reference height H th Lower, H ≥ H th , W ≧ W th Therefore, it is judged as "defective."

[0053] Furthermore, the determination may be made based on the volume of the weld metal 15. Here, a method is shown for predicting the state (volume, shape) of the backside excess metal 15b on the back side of the weld from the height profile M of the weld metal 15 measured after welding and the total amount of welding wire 19 fed during welding. Fig. 20 is an explanatory diagram showing the height profile M of the weld metal 15 measured after welding and a height profile M0 obtained by measuring the through hole 11a (pre-hole) which is the welding position before welding. Fig. 21 is an explanatory diagram for explaining the volume of the weld metal 15 formed in the through hole 11a of the first member 11 after welding.

[0054] 20, the volumes of the portion of weld metal 15 filled in through hole 11a and the portion protruding from first member 11, including front reinforcement 15a, can be estimated from the measured height profiles M and M0. In addition, weld metal 15 has a volume according to the total amount of fed welding wire, and the volume of back reinforcement 15b can be estimated from the relationship between the volumes of the above-mentioned portions.

[0055] Specifically, the volume Vb of the back weld 15b is calculated by multiplying the volume Vw of the fed welding wire 19, the volume Vout of the protruding portion of the weld metal 15 calculated from the height profile M measured after welding, and the volume V h Based on this relationship, it is expressed by equation (1). Vb= Vw-Vout-Vh-C ··· Formula (1) Here, C is a constant that corrects for the effects of losses due to spatters and the like that occur during welding, and the protrusion of weld metal into the gap between the first member 11 and the second member 13. The value of the constant C may be set empirically, may be set by machine learning, or may be set to zero.

[0056] Also, the surface reinforcement 15a of the weld metal 15 formed at the weld position may be determined based on the area of ​​the surface reinforcement 15a when viewed from above. Fig. 22 is an explanatory diagram showing a cross-sectional view and a front view of the weld metal 15 that joins the first member 11 and the second member 13. Here, the plate thickness direction is the Z direction, and the plate surface directions perpendicular to the Z direction are the X direction and the Y direction. The surface reinforcement 15a of the weld metal 15 is a portion that exerts an anchor effect by being in close contact with the first member 11, and it is preferable that the surface reinforcement 15a has a sufficient area when viewed from the front (on the XY plane). Therefore, the area of ​​the surface reinforcement 15a is measured and compared with a predetermined reference area to evaluate the soundness of the joint.

[0057] 23 and 24 are explanatory diagrams showing, in the XY plane, the outer edge shape of the surface reinforcement 15a of the weld metal 15. The shape of the surface reinforcement 15a can be measured by the height measuring device 21 of the laser displacement meter described above (FIG. 4), but it may also be detected by combining multiple pieces of measurement information, such as detecting the outer edge shape of the surface reinforcement 15a from image data obtained by capturing an image using an image sensor.

[0058] As shown in Fig. 23, when the profile Prf representing the outer edge of the surface reinforcement 15a of the weld metal 15 measured after welding has a large area so as to cover the predetermined reference height distribution SP, it is judged as "normal". On the other hand, as shown in Fig. 24, when the profile Prf representing the outer edge of the measured surface reinforcement 15a is smaller than the predetermined reference height distribution SP or is deviated from the center of the reference height distribution SP so that the reference height distribution SP protrudes from the profile Prf, it is judged as "defective". As described above, various forms of criteria can be adopted for comparing with the measured profile Prf.

[0059] <Repair of defective parts> In the above-mentioned inspection of the welded portion, a step of repairing the welded portion determined to be "defective" may be further provided. FIG. 25 is a flow chart showing an inspection procedure including detection of the position of the preliminary hole, welding and height measurement, and a repair process of the welded portion determined to be defective. In the inspection procedure shown in FIG. 25, as a premise, the control device 31 shown in FIG. 4 is operated according to a program including information of a welding procedure for joining the first member 11 and the second member 13. In this program, information on the welding position, which is the position of the through hole 11a (preliminary hole) of the first member 11, and welding conditions such as the welding current, welding voltage, and feeding speed of the welding wire are registered. The control device 31 reads the prepared program, drives the welding robot 23 according to the program, and performs spot welding at the designated position of the preliminary hole.

[0060] In such a welding procedure, the control device 31 drives the welding robot 23 according to the program, and places the height measuring device 21 at the position of the preliminary hole that will be the welding position. Then, the height measuring device 21 measures the height of the preliminary hole, and detects the exact position of the preliminary hole (S11). The control device 31 compares the detected position of the preliminary hole with the position of the preliminary hole registered in the program, and if there is a deviation between the relative positions, changes the teaching position of the welding robot 23 so that the welding position becomes the position of the detected preliminary hole (S12). For example, the control device 31 corrects the position information of the preliminary hole registered in the program, and outputs the corrected position information to the welding robot 23 as target position information.

[0061] In this way, the position of the preliminary hole measured before welding is fed back to the welding system 200, and the point previously taught as the welding point is corrected, thereby reducing the deviation during welding and obtaining a higher quality joint. It is preferable to correct the center position of the preliminary hole for this correction of the target position, but a position shifted from the center may be set as the target position depending on the plate assembly, part shape, required performance, etc. Also, by measuring the depth of the preliminary hole, the plate gap between the first member 11 and the second member 13 can be estimated. For example, if a steel plate with a plate thickness of 1.4 mm is used and the depth of the preliminary hole is 1.9 mm, the plate gap can be estimated to be 0.5 mm. This is fed back to the welding conditions, and the welding conditions such as the welding current value and the arc time are changed to conditions suitable for the plate gap, thereby obtaining a higher quality joint.

[0062] Next, the control device 31 starts the welding operation according to the program, positions the welding torch 17 at the corrected preliminary hole position, and performs spot welding (S13). After welding, the height of the weld metal 15 at the welded portion is measured as described above (S14). The judgment device 33 checks whether the conditions are satisfied based on information such as the height profile measured by the height measuring device 21 (S15), and judges whether it is "normal" or "failed" (S16, S17). If it is judged to be "normal", the process is terminated, and if it is judged to be "failed", it is judged whether repair is possible (S18). If repair is possible, the welding torch 17 is again positioned at the preliminary hole to perform repair welding (S19), and the process is repeated from step S14 of measuring the height of the welded portion. In repair welding, selective welding may be performed to fill in the portion where the weld metal is insufficient, or spot welding may be performed by changing conditions such as the welding current, welding voltage, and welding wire feed speed, or spot welding may be performed again without changing the conditions. It is preferable to set the repair welding process depending on the measured height profile. On the other hand, if the repair is difficult, it is determined that a check is required in a separate process (S20), and the process is terminated.

[0063] In this procedure, the above steps S18, S19, and S20 are added as a repair process ST. In this way, the judgment result of the welded portion is fed back to the welding system 200, and the repair process ST is performed when it is judged to be defective, thereby reducing the effort of repairing the defective portion in a later process. It is preferable to prepare multiple specific treatment contents of the repair process ST for each defective judgment pattern. For example, it is possible to take appropriate treatment depending on the situation, such as a pattern in which the excess fill height is insufficient, a pattern in which the weld metal is significantly displaced from the preliminary hole, etc. In addition, when it is judged to be defective, the welding conditions such as the welding current and welding voltage at that time, and measurement data such as the amount of displacement can be saved and used to build a database, which can be used to investigate the cause of the defective judgment.

[0064] In this manner, the present welding system 200 has a correction function for correcting the application position of spot welding, and a repair function for repairing the welded portion as necessary.

[0065] In the above procedure, inspection is performed after each welding point, but multiple welding points may be inspected together after welding. Fig. 26 is a flow chart showing an inspection procedure in which the inspection shown in Fig. 25 is modified from one point at a time to a multiple point inspection. In this inspection procedure, first, the above-mentioned detection of the preliminary hole position (S31) and the change of the teaching position (S32) are repeatedly performed for all points to be welded (S33). Then, welding torch 17 is positioned at the corrected preliminary hole position and spot welding is performed (S34). This process is repeated for all points to be welded (S35).

[0066] After welding, the height of the weld metal 15 at the welded portion is measured (S36) as described above. It is checked whether the conditions are satisfied (S37) to determine whether the welded portion is "normal" or "failed." If the welded portion is determined to be "failed," then, as in the repair process ST described above, if repair is possible, repair measures are implemented (S38), and the process is started over from step S36 of measuring the height of the welded portion. If repair is difficult, the process proceeds to measuring the height of the next welded portion (S36). If the welded portion is determined to be "normal," the process from step S36 onward is repeated until inspection of all welded portions is completed (S39). According to this procedure, multiple welded portions can be continuously welded, determined, and repaired, and the joined body 27 can be efficiently manufactured.

[0067] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates mutual combinations of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the descriptions in the specification and well-known techniques, and these are included in the scope of the protection sought.

[0068] As described above, the present specification discloses the following: (1) A method for inspecting a dissimilar metal joint, in which at least one steel first member having a through hole in the thickness direction and a non-ferrous metal second member are stacked on top of each other, and the sheet assembly is spot-welded at the position of the through hole, measuring a protruding height of a weld metal formed by the spot welding from a surface of the first member opposite to the second member; determining a welding condition of the spot welding in accordance with the measured protruding height; Inspection methods for dissimilar metal joints. According to this inspection method for dissimilar metal joints, the protruding height of the weld metal formed by spot welding a first member and a second member from the first member can be measured, and the welding condition, such as the joint strength, can be determined based on this protruding height.

[0069] (2) measuring a protruding height of a weld metal formed by the spot welding from a back surface of the second member opposite to the first member; The method for inspecting a dissimilar metal joint according to (1), further comprising determining a welding condition of the spot weld based on the measured protruding height from the front surface and the measured protruding height from the back surface. According to this method for inspecting a dissimilar metal joint, by measuring the protruding height of the weld metal from the second member, the weld condition, such as the joint strength, can be determined with high accuracy based on this protruding height.

[0070] (3) The method for inspecting a dissimilar metal joint according to (1) or (2), further comprising the step of judging a welding condition of the spot welds using the protruding heights of three or more points of the weld metal. According to this method for inspecting dissimilar metal joints, the maximum protruding height and width can be obtained from the protruding heights of three or more points, simplifying the assessment process.

[0071] (4) The method for inspecting a dissimilar metal joint according to any one of (1) to (3), further comprising measuring the protruding height of the weld metal using a laser displacement meter. According to this method for inspecting dissimilar metal joints, the inspection can be performed immediately and without contact with the object to be measured by irradiating it with laser light.

[0072] (5) The method for inspecting a dissimilar metal joint according to any one of (1) to (3), further comprising measuring the protruding height of the weld metal from an image captured by an image sensor. According to this method for inspecting dissimilar metal joints, height information is extracted from information in a captured image, allowing for real-time inspection without contacting the object to be measured.

[0073] (6) The inspection method for a dissimilar metal joint according to any one of (1) to (5), wherein the second member is aluminum or an aluminum alloy, or magnesium or a magnesium alloy. According to this inspection method for dissimilar metal joints, the strength of joints between steel and light metals such as aluminum and magnesium can be determined with high accuracy.

[0074] (7) measuring the position of the through hole before performing the spot welding; The method for inspecting a dissimilar metal joint according to any one of (1) to (6), further comprising: judging the welding condition based on the protruding height of the weld metal corresponding to the measured position of the through hole. According to this method for inspecting dissimilar metal joints, the protruding height of the weld metal is measured in correspondence with the position of the through hole, so that the measurement position can be accurately determined and measurement accuracy can be improved.

[0075] (8) The method for inspecting a dissimilar metal joint according to (7), wherein the position of the through hole is measured using a height gauge that measures the protruding height of the weld metal. According to this method of inspecting dissimilar metal joints, the position of the through hole is measured using a height gauge that measures the protrusion height, so that the position of the through hole can be measured by adding a simple process, and equipment costs can be reduced.

[0076] (9) a welding process in which at least one steel first member having a through hole in the plate thickness direction and a non-ferrous metal second member are overlapped with each other to form a dissimilar metal joint by spot welding the plate assembly at the positions of the through holes; a measuring step of measuring at least one of a protruding height of a weld metal formed by the spot welding protruding from a surface of the first member opposite to the second member and a protruding height of a weld metal formed by the spot welding protruding from a back surface of the second member opposite to the first member; a determination step of determining a welding condition of the spot welding based on the measured protrusion height; a repairing step of repairing a welding position of the spot weld when the welding state of the spot weld is determined to be defective; A welding method comprising the steps of: According to this welding method, for a dissimilar metal joint formed by spot welding a first member and a second member in a welding process, at least one of the protruding heights of the weld metal from the first member or the second member is measured in a measurement process. The welding condition of the spot weld is judged in a determination process based on the measured protruding height. If the welding condition is judged to be defective, the weld position is repaired in a repair process. In this way, by feeding back the judgment result of the welding condition and repairing the parts judged to be defective, it is possible to reduce the effort of repairing the defective parts in a later process.

[0077] (10) A step of measuring the position of the through hole before the spot welding, The welding method according to (9), wherein in the welding step, the measured position of the through hole is feedback-controlled to a target position of the spot welding, thereby correcting a construction position of the next spot welding. According to this welding method, spot welding can be performed at accurate positions with any misalignment corrected, making it easier to obtain the desired joint strength.

[0078] (11) An inspection device for a dissimilar metal joint, in which at least one steel first member having a through hole in the thickness direction and a non-ferrous metal second member are stacked on top of each other, and the sheet assembly is spot-welded at the position of the through hole, a height measuring unit that measures a protruding height of a weld metal formed by the spot welding from a surface of the first member opposite to the second member; a determination unit that determines a welding state of the spot welding based on the measured height; An inspection device for dissimilar metal joints comprising: According to this inspection device for dissimilar metal joints, the height measuring unit measures the protruding height of the weld metal formed by spot welding a first member and a second member from the first member, and the judging unit can judge the welding condition, such as the joint strength, based on this protruding height.

[0079] (12) The height measuring unit measures a protruding height of a weld metal formed by the spot welding from a back surface of the second member opposite to the first member side, The inspection device for dissimilar metal joints described in (11), wherein the judgment unit judges the welding condition of the spot weld based on the measured protruding height of the first member from the front surface and the measured protruding height of the second member from the back surface. According to this method for inspecting a dissimilar metal joint, by measuring the protruding height of the weld metal from the second member, the weld condition, such as the joint strength, can be determined with high accuracy based on this protruding height.

[0080] (13) An inspection device for a dissimilar metal joint according to (11) or (12), a welding device that joins the first member and the second member by the spot welding to form the dissimilar metal joint; Equipped with a repair function for repairing a welding position of the spot weld determined to be defective by driving the welding device when the welding state of the spot weld is determined to be defective. According to this welding system, for a dissimilar metal joint formed by spot welding a first member and a second member with a welding device, at least one of the protruding heights of the weld metal from the first member or the second member is measured by an inspection device. The welding condition of the spot weld is judged in a judgment process based on the measured protruding height. If the welding condition is judged to be defective, the welding position is repaired by a repair device. In this way, by feeding back the judgment result of the welding condition and repairing the parts judged to be defective, the effort of repairing the defective parts in a later process can be reduced.

[0081] (14) The welding system described in (13) has a correction function of measuring the position of the through hole before performing the spot welding, and feedback-controlling the measured position of the through hole to a target position of the spot welding to correct the construction position of the spot welding. According to this welding system, spot welding can be performed at accurate positions with positional deviation corrected, making it easier to obtain the desired joint strength.

[0082] (15) The welding device has a welding robot that performs the spot welding, The welding system according to (13) or (14), wherein the height measuring unit is provided on a movable part of the welding robot. This welding system can reduce installation space and capital investment costs. In addition, the height measuring unit can be easily positioned at the desired measurement position by driving the welding robot, so inspection can be easily performed immediately after welding. In addition, the tact time can be shortened. [Explanation of symbols]

[0083] 11 First member 11a Through hole 11b,11c Tsuba 13 Second member 13a Penetration 15 Welding metal 15a Omote Yomori 15b Back side 15c Shaft 17 Welding torch 19 Welding Wire 21 Height measuring device 23 Welding robot 25 Tip shaft 27 Zygote 31 Control device 33 Judgment device (judgment unit) 35 Robot control unit 37 Welding control unit 100 Dissimilar metal joints 200 Welding System Ak Arc At Inspection area G Shielding gas LB laser light

Claims

1. A method for inspecting a dissimilar metal joint in which at least one steel first member having a through hole in a plate thickness direction and a non-ferrous metal second member are stacked on each other, and the plate assembly is spot-welded at the position of the through hole, measuring a protruding height of a weld metal formed by the spot welding from a surface of the first member opposite to the second member; determining a welding condition of the spot welding in accordance with the measured protruding height; Inspection methods for dissimilar metal joints.

2. measuring a protruding height of a weld metal formed by the spot welding from a back surface of the second member opposite to the first member; determining a welding condition of the spot welding based on the measured protruding height from the front surface and the measured protruding height from the back surface; The method for inspecting a dissimilar metal joint according to claim 1.

3. The welding condition of the spot welds is determined using the protruding heights of three or more points of the weld metal. The method for inspecting a dissimilar metal joint according to claim 1.

4. The protruding height of the weld metal is measured by a laser displacement meter. The method for inspecting a dissimilar metal joint according to claim 1.

5. The protruding height of the weld metal is measured from an image captured by an image sensor. The method for inspecting a dissimilar metal joint according to claim 1.

6. The second member is aluminum or an aluminum alloy, or magnesium or a magnesium alloy. The method for inspecting a dissimilar metal joint according to claim 1.

7. measuring the position of the through hole before performing the spot welding; determining the welding condition according to the protruding height of the weld metal corresponding to the measured position of the through hole; The method for inspecting a dissimilar metal joint according to claim 1.

8. The position of the through hole is measured using a height gauge that measures the protruding height of the weld metal. The method for inspecting a dissimilar metal joint according to claim 7.

9. A welding process in which a plate assembly in which at least one steel first member having a through hole in the plate thickness direction and a non-ferrous metal second member are overlapped with each other is spot-welded at the positions of the through holes to form a dissimilar metal joint; a measuring step of measuring at least one of a protruding height of a weld metal formed by the spot welding protruding from a surface of the first member opposite to the second member and a protruding height of a weld metal formed by the spot welding protruding from a back surface of the second member opposite to the first member; a determination step of determining a welding condition of the spot welding based on the measured protrusion height; a repairing step of repairing a welding position of the spot weld when the welding state of the spot weld is determined to be defective; A welding method comprising the steps of:

10. measuring the position of the through hole before the spot welding; In the welding step, the measured position of the through hole is feedback-controlled to a target position of the spot welding, thereby correcting a construction position of the next spot welding. The welding method according to claim 9.

11. An inspection device for a dissimilar metal joint in which at least one steel first member having a through hole in the plate thickness direction and a non-ferrous metal second member are stacked on top of each other, and the plate assembly is spot-welded at the position of the through hole, a height measuring unit that measures a protruding height of a weld metal formed by the spot welding from a surface of the first member opposite to the second member; a determination unit that determines a welding state of the spot welding based on the measured height; An inspection device for dissimilar metal joints comprising:

12. The height measuring unit measures a protruding height of a weld metal formed by the spot welding from a back surface of the second member opposite to the first member side, The determination unit determines a welding state of the spot welding based on a measured protruding height of the first member from the front surface and a measured protruding height of the second member from the back surface. The inspection device for a dissimilar metal joint according to claim 11.

13. The inspection device for a dissimilar metal joint according to claim 11 or 12, a welding device for joining the first member and the second member by the spot welding to form the dissimilar metal joint; Equipped with a repair function for repairing a welding position of the spot weld that is determined to be defective by driving the welding device when the welding state of the spot weld is determined to be defective; Welding system.

14. a correction function of measuring a position of the through hole before performing the spot welding, and feedback-controlling the measured position of the through hole to a target position of the spot welding to correct the execution position of the spot welding; The welding system of claim 13.

15. the welding device has a welding robot that performs the spot welding, The height measuring unit is provided on a movable part of the welding robot. The welding system of claim 13.

Images