Evaluation method for welding quality, evaluation device for welding quality, and welding system having the same

Abstract

To provide an evaluation method for a welding quality capable of simply and surely evaluating a welding quality of the whole welded part.SOLUTION: An evaluation method for a welding quality includes first to seventh steps. The first step sets an evaluation index for the start processing section, and the second step sets a parameter. The third step forms a welding bead 210, and measures a physical amount in welding. The fourth step divides a welding section into a plurality of sections including the start processing section. The fifth step determines a first evaluation score related to the evaluation index. The sixth step calculates a second evaluation score by multiplying the first evaluation score by a weighting coefficient. The seventh step evaluates a welding quality of the welding bead 210 on the basis of the second evaluation score. The start processing section includes a first period T1 until wire feed speed W reaches a predetermined value WS.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a welding quality evaluation method, a welding quality evaluation device, and a welding system including the same. [Background technology]

[0002] In arc welding, in order to improve welding quality, the time variation of the welding current (hereinafter referred to as the welding current waveform) or the time variation of the welding voltage (hereinafter referred to as the welding voltage waveform) or both are precisely controlled.

[0003] For example, Patent Document 1 discloses a method for collecting multiple welding factor data related to the operation of a welding torch in real time during welding, and determining the occurrence of welding defects and welding defect modes based on the presence or absence of abnormalities in the multiple welding factor data and their combination patterns. The welding factor data includes at least three of the welding current, welding voltage, number of short circuits, welding wire feed speed, and welding wire feed load.

[0004] Patent Document 2 discloses a method for acquiring welding data indicating the state of welding at a plurality of welding points, and for each welding point, associating the acquired welding data with the welding point, and judging and evaluating the welding quality according to the input welding data. The plurality of welding points are either a plurality of welding points formed on a base material, or a plurality of sections obtained by virtually dividing one welding point.

[0005] Furthermore, Patent Document 3 discloses a configuration in which the welding current waveform and the welding voltage waveform are measured, and a period in which the welding voltage is below a predetermined threshold is determined as a short-circuit period, and a period in which the welding voltage is above the threshold is determined as an arc period, and an alarm is issued when the ratio of the short-circuit period to the arc period becomes equal to or greater than a set value. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-253538 [Patent Document 2] Japanese Patent Application Publication No. 2022-124799 [Patent Document 3] Japanese Patent Application Publication No. 08-267244 Summary of the Invention [Problem to be solved by the invention]

[0007] In arc welding, the arc state may not be stable until a predetermined period has elapsed since the start of welding, so welding control different from that used for main welding, i.e., when the arc state is stable, is performed. Also, during a predetermined period prior to the end of welding, the arc is reduced and eventually extinguished, so welding control different from that used for main welding is performed.

[0008] For example, arc interruption is likely to occur at the start of welding. If the arc interruption lasts for a long period of time, the welding current waveform and welding voltage waveform can be monitored in real time to detect the abnormality and stop the welding.

[0009] However, if the arc interruption period is short, the welding may continue without detecting the abnormality. During the arc interruption period, the amount of heat input to the base material (the workpiece) is significantly reduced, which can cause local changes in the shape of the weld, and the overall evaluation of the weld may result in a defective weld.

[0010] Similarly, if an abnormality in the welding current or welding voltage occurs at the end of welding and recurs within a short period of time, the abnormality may not be detected and welding may continue. In this case, too, the evaluation of the entire welded area may result in a defective weld.

[0011] However, the conventional configurations disclosed in Patent Documents 1 to 3 do not disclose any method for appropriately detecting abnormalities in welding current or welding voltage that occur at the start or end of welding and evaluating the welding quality of the welded portion.

[0012] The present disclosure has been made in consideration of the above points, and its purpose is to provide a welding quality evaluation method, a welding quality evaluation device, and a welding system equipped with the same that can easily and reliably evaluate the welding quality of a welded portion. [Means for solving the problem]

[0013] In order to achieve the above-mentioned object, a method for evaluating welding quality according to the present disclosure is a method for evaluating welding quality in arc welding, and includes at least the following steps: a first step of setting an evaluation index corresponding to welding quality in at least a start processing section; a second step of setting parameters corresponding to the start processing section; a third step of welding base materials to form a weld and measuring physical quantities during welding; a fourth step of dividing the welding section in the welded section into a plurality of sections including at least the start processing section; a fifth step of determining a first evaluation score related to the evaluation index based at least on the physical quantities measured in the third step; a sixth step of calculating a second evaluation score by weighting the first evaluation score using a weighting coefficient set based on the parameters set in the fourth step; and a seventh step of evaluating the welding quality of the welded section based on the second evaluation score calculated in the sixth step, wherein the start processing section includes a first period from when a switch of a welding torch is turned on to when a feed speed of a welding wire held by the welding torch reaches a predetermined value.

[0014] a parameter setting unit that sets parameters corresponding to at least the start processing section based on at least the physical quantities input to the input unit; an evaluation score calculation unit that determines a first evaluation score for the evaluation index based at least on the physical quantities input to the input unit; a weighting coefficient setting unit that sets a weighting coefficient based on the parameters; and a welding quality evaluation unit that evaluates the welding quality of the welded section based on a second evaluation score, wherein the evaluation score calculation unit weights the first evaluation score using the weighting coefficient to calculate the second evaluation score, and the start processing section includes a first period from when a welding torch is switched on to when a feed speed of a welding wire held by the welding torch reaches a predetermined value.

[0015] The welding system according to the present disclosure is characterized by including at least an arc welding device for welding the base material, and the welding quality evaluation device. [Effects of the Invention]

[0016] According to the present disclosure, by evaluating the welding quality for each of a plurality of sections including a predetermined section after the start of welding or before the end of welding, the welding quality of the entire welding portion can be evaluated simply and reliably. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of a welding system according to a first embodiment. [Figure 2] FIG. 1 is a schematic diagram illustrating the configuration of a welding quality evaluation device. [Figure 3] 10 is a flowchart showing a procedure for evaluating welding quality. [Figure 4]FIG. 10 is a diagram for explaining parameters corresponding to welding sections and time. [Figure 5] FIG. 10 is a diagram for explaining parameters corresponding to a welding section and a bead length. [Figure 6A] 1 shows an example of an evaluation result of welding quality according to the first embodiment. [Figure 6B] 10 is another example of the evaluation results of the welding quality according to the first embodiment. [Figure 7A] 10A and 10B are diagrams showing the welding current waveform and the welding voltage waveform when there is no arc interruption. [Figure 7B] 7B is a plan view schematically illustrating the shape of a weld bead when arc welding is performed in the state shown in FIG. 7A. FIG. [Figure 8A] FIG. 10 is a diagram showing a welding current waveform and a welding voltage waveform when the arc interruption occurs once. [Figure 8B] 8B is a plan view schematically illustrating the shape of a weld bead when arc welding is performed in the state shown in FIG. 8A. FIG. [Figure 9A] FIG. 10 is a diagram showing the welding current waveform and the welding voltage waveform when the arc interruption occurs twice. [Figure 9B] 9B is a plan view schematically illustrating the shape of a weld bead when arc welding is performed in the state shown in FIG. 9A. FIG. [Figure 10] FIG. 10 is a diagram showing another evaluation index in the start processing section according to the second embodiment. [Figure 11] 10 is a flowchart showing a procedure for evaluating welding quality according to a third embodiment. [Figure 12A] 10 is an example of an evaluation result of welding quality according to the third embodiment. [Figure 12B] 10 is another example of the evaluation results of the welding quality according to the third embodiment. [Figure 13] 10A and 10B are diagrams showing welding current waveforms and welding voltage waveforms when a long-term short circuit occurs. [Figure 14] 10A and 10B are diagrams showing various output waveforms during short-circuit welding according to the fourth embodiment. [Figure 15A] 10 is an example of an evaluation result of welding quality according to the fourth embodiment. [Figure 15B]10 is another example of the evaluation results of the welding quality according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses. (Embodiment 1) [Welding system configuration] 1 is a schematic diagram of a welding system according to this embodiment. The welding system 300 includes an arc welding device 20 and a welding quality evaluation device 100.

[0019] Arc welding apparatus 20 performs welding by generating an arc 80 between welding wire 50, which is a consumable electrode, and base metal 200, which is an object to be welded. Note that welding wire 50 is held by welding torch 30, and as welding torch 30 moves at a predetermined speed, the tip of welding wire 50 also moves along a predetermined welding section at the same speed. Note that welding torch 30 has nozzle 30A (see FIG. 13 ), which is a supply port for shielding gas that is sprayed onto base metal 200 during welding. Nozzle 30A protrudes from the tip of welding torch 30. During welding, welding wire 59 protrudes from nozzle 30A toward base metal 200.

[0020] Arc welding apparatus 20 has a main transformer 2, a primary side rectifier 3, a switching unit 4, a DCL (reactor) 5, a secondary side rectifier 6, a welding current detector 7, a welding voltage detector 8, a control switching unit 9, an output controller 10, a wire feed speed controller 13, and a welding torch 30. Arc welding apparatus 20 also has a robot controller 16 that controls the operation of a robot 60 that holds welding torch 30, and a welding speed calculator 17. Arc welding apparatus 20 may also include a wire feeder 40.

[0021] The output control unit 10 has a short-circuit welding control unit 11 and a pulse welding control unit 12. The wire feed speed control unit 13 has a wire feed speed detection unit 14 and a wire feed speed calculation unit 15. The primary side rectification unit 3 rectifies the input voltage input from an input power source (three-phase AC power source) 1 external to the arc welding device 20. The switching unit 4 controls the output of the primary side rectification unit 3 to an output suitable for welding. The main transformer 2 converts the output of the switching unit 4 to an output suitable for welding. The secondary side rectification unit 6 rectifies the output of the main transformer 2. The DCL (reactor) 5 smoothes the output of the secondary side rectification unit 6 to a current suitable for welding.

[0022] Welding current detection unit 7 detects welding current I. Welding voltage detection unit 8 detects welding voltage V. In the following description, the welding current I, welding voltage V, and the time required for welding, i.e., welding time, measured during welding may be referred to as physical quantities. The welding current waveform and welding waveform are also included in the physical quantities.

[0023] The control switching unit 9 has a timing function and is a switching unit that outputs the timing for switching from short circuit welding control to pulse welding control to the output control unit 10. Note that a timer having a timing function may be separately provided in the arc welding device 20.

[0024] The output control unit 10 controls the welding output by outputting a control signal to the switching unit 4. The short circuit welding control unit 11 controls short circuit welding when the control switching unit 9 commands short circuit welding. The pulse welding control unit 12 controls pulse welding when the control switching unit 9 commands pulse welding. As will be described later, welding parameters set according to the welding conditions of the base material 200 are input to the output control unit 10, and short circuit welding and pulse welding are controlled based on these parameters.

[0025] Wire feed speed control unit 13 controls wire feeder 40 to control the feed speed of welding wire 50 (hereinafter referred to as wire feed speed W). Wire feed speed detection unit 14 detects wire feed speed W. Wire feed speed calculation unit 15 calculates the feed speed W and feed amount of welding wire 50 based on a signal from wire feed speed detection unit 14. It also calculates the integrated amount of feed of welding wire 50. Wire feed speed calculation unit 15 also compares a command value and a detected value of wire feed speed W to determine the difference, and performs feedback control based on the integrated amount of the difference to match the actual wire feed speed to the command value.

[0026] Arc welding apparatus 20 is connected to wire feeder 40 and weld quality evaluation apparatus 100. Weld quality evaluation apparatus 100 evaluates the weld quality of a welded portion formed on base material 200, which is weld bead 210 (see FIG. 5 ) in this embodiment, based on physical quantities and the like measured during arc welding. The configuration of weld quality evaluation apparatus 100 and the functions of each unit will be described in detail later.

[0027] The arc welding apparatus 20 and the welding quality evaluation apparatus 100 may each have a communication interface unit (not shown). In this case, data is exchanged between the arc welding apparatus 20 and the welding quality evaluation apparatus 100 via the respective communication interface units. In this case, the arc welding apparatus 20 and the welding quality evaluation apparatus 100 may be connected by Ethernet (registered trademark), an analog cable, a serial cable, or the like.

[0028] Robot 60 is a known articulated axis robot that moves welding torch 30 so that the tip of welding wire 50 held by welding torch 30 moves at a set welding speed along a predetermined weld line (not shown) in base material 200.

[0029] Robot control unit 16 sends commands (also called speed commands) to motors (not shown) that operate each joint axis of robot 60, determining the amount of rotation of each motor. Robot 60 moves welding wire 50 held by welding torch 30 based on the speed command value sent from robot control unit 16. In other words, the speed command value determines the movement speed of the tip of welding torch 30, and ultimately the tip of welding wire 50, relative to base material 200. This movement speed corresponds to the welding speed described above.

[0030] In addition, the rotation amount and rotation speed of each joint axis incorporated in the robot 60 are measured by an encoder (not shown), and based on the measurement results, the welding speed calculation unit 17 calculates a welding speed corresponding to the moving speed of the tip of the welding wire 50.

[0031] When a torch switch (torch SW: not shown) provided on welding torch 30 is turned ON, the welding output of arc welding device 20 is supplied to welding wire 50 via power cable 70 and welding tip 31. Power cable 70 is connected to both welding tip 31 and base material 200. Then, an arc 80 is generated between welding wire 50 and base material 200 by the welding output of arc welding device 20, thereby performing welding.

[0032] [Configuration of welding quality evaluation device] Fig. 2 is a schematic configuration diagram of a welding quality evaluation device. As shown in Fig. 2, welding quality evaluation device 100 has the following multiple functional blocks. Welding quality evaluation device 100 has a first input unit 101A, a second input unit 101B, an output unit 102, a memory unit 103, and a display unit 104. Welding quality evaluation device 100 has a welding section division unit 105, an evaluation index setting unit 106, a parameter setting unit 107, an evaluation score calculation unit 108, a weighting coefficient setting unit 109, and a welding quality evaluation unit 110.

[0033] Typically, the welding quality evaluation device 100 is configured with a known computer. Software implemented on a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit) is executed to operate each of the multiple functional blocks constituting the welding quality evaluation device 100, excluding the first input unit 101A, the second input unit 101B, the output unit 102, the memory unit 103, and the display unit 104.

[0034] The first input unit 101A is an input port, to which the welding current I detected by the welding current detection unit 7 of the arc welding device 20, the welding voltage V detected by the welding voltage detection unit 8, and the time measured by the control switching unit 9 are input.

[0035] The second input unit 101B is also an input port, and receives as input a speed command value sent from the robot control unit 16 of the arc welding device 20. In addition, the time measured by the control switching unit 9, the welding speed calculated by the welding speed calculation unit 17, the wire feed speed W calculated by the wire feed speed calculation unit 15, etc. may also be input to the second input unit 101B. In the following description, the first input unit 101A and the second input unit 101B may be collectively referred to as the input unit 101.

[0036] Output unit 102 is an output port, and outputs the evaluation results of the welding quality evaluated by weld quality evaluation unit 110 to display unit 104. Note that display unit 104 may output physical quantities such as the welding current waveform, welding voltage waveform, and time change of wire feed speed W (hereinafter referred to as feed speed waveform) input to first input unit 101A to display unit 104. Output unit 102 may also output a first evaluation score, a second evaluation score, a comprehensive evaluation score, and a weighting coefficient, which will be described later, to display unit 104. Output unit 102 may also be configured to be able to output these numerical values ​​and charts and the like created based on the numerical values ​​to the outside of welding quality evaluation device 100.

[0037] Memory unit 103 is configured with a known semiconductor memory, HDD (Hard Disk Drive), or the like, and stores the welding current waveform and welding voltage waveform input to first input unit 101A, as well as various values ​​input to second input unit 101B. Memory unit 103 also stores parameters corresponding to one or more sections divided by welding section division unit 105. Memory unit 103 stores weighting coefficients, first evaluation scores, second evaluation scores, and overall evaluation scores, as well as evaluation results of welding quality. As will be described later, an evaluation algorithm for determining the first evaluation score is also stored in memory unit 103.

[0038] Since the parameters can be changed depending on the manner in which the sections are divided, there are multiple types of parameters associated with the type of section. Furthermore, the weighting coefficients are set based on the type of section and the type of parameter. Therefore, it is preferable that the type of section, the type of parameter, and the weighting coefficients are associated with each other and stored in the storage unit 103 in, for example, a table format. However, the weighting coefficients can be changed depending on the level of welding quality required.

[0039] Therefore, the second input unit 101B may be configured with an input port and a known input device, for example, a keyboard or a touch panel, so that the weighting coefficients can be input later to the memory unit 103 and / or the weighting coefficient setting unit 109 of the welding quality evaluation device 100. Also, the evaluation algorithm may be input from the second input unit 101B and stored in the memory unit 103. Also, each parameter of the evaluation algorithm may be input from the second input unit 101B to rewrite the evaluation algorithm stored in the memory unit 103. In this case, it is preferable that the evaluation algorithm be saved with a name or version different from that of the rewritten version.

[0040] The display unit 104 is configured with a known liquid crystal display, organic EL display, or the like. The display unit 104 displays the evaluation results of the welding quality described above. The display unit 104 also displays the weighting coefficients, first evaluation scores, second evaluation scores, and overall evaluation scores described above, as well as charts and graphs created based on these. The display unit 104 may be a touch panel display. In this case, the welding operator inputs data to the welding quality evaluation device 100 via the display unit 104.

[0041] Welding section dividing unit 105 divides the welding section corresponding to weld bead 210 into a plurality of sections including at least a start processing section. The welding section and the start processing section will be described later.

[0042] The evaluation index setting unit 106 sets an evaluation index corresponding to the welding quality at least in the start processing section.

[0043] The parameter setting unit 107 sets at least parameters corresponding to the start processing section based at least on the physical quantities input to the first input unit 101 A. As will be described later, the speed command value input to the second input unit 101 B can also be a value for setting the parameters.

[0044] The evaluation score calculation unit 108 determines a first evaluation score for the evaluation index based at least on the physical quantity input to the first input unit 101A. Furthermore, the evaluation score calculation unit 108 weights the first evaluation score using the weighting coefficient described above to calculate a second evaluation score.

[0045] The weighting coefficient setting unit 109 sets weighting coefficients based on the type of parameter. As mentioned above, the weighting coefficients are also set according to the type of divided section, as will be described later.

[0046] Weld quality evaluation unit 110 evaluates the weld quality of weld bead 210 based on the second evaluation score.

[0047] Furthermore, the welding quality evaluation device 100 may be installed in a single housing together with the arc welding device 20 in such a way that the welding quality evaluation device 100 shares the respective control units and calculation units of the arc welding device 20 .

[0048] [Method for evaluating welding quality] Fig. 3 is a flowchart of the procedure for evaluating weld quality. Fig. 4 is a diagram for explaining parameters corresponding to a welding section and time. Fig. 5 is a diagram for explaining parameters corresponding to a welding section and bead length. For ease of explanation, the feed rate waveform in Fig. 4 is shown in a simplified form and differs from the actual waveform. In this embodiment, weld bead 210 is formed by pulse welding.

[0049] When evaluating the welding quality of weld bead 210, evaluation index setting unit 106 first sets an evaluation index corresponding to the welding quality of weld bead 210 in the start processing section (step S1). In this embodiment, the evaluation index is the number of times arc 80 is lost during welding, that is, the number of times arc interruption occurs. However, the type of evaluation index is not particularly limited to this and can be changed as appropriate. This will be described later.

[0050] Furthermore, parameter setting unit 107 sets parameters corresponding to the start processing section (step S2). In this embodiment, the parameter is the first period T1. However, this is not limiting, and the parameter may be a first bead length L1, which will be described later. Both the first period T1 and the first bead length L1 are calculated based on the welding time acquired in step S4.

[0051] Next, weld bead 210 is formed on base material 200 (step S3). During execution of step S3, welding current detection unit 7 acquires welding current I and welding voltage detection unit 8 acquires welding voltage V. Control switching unit 9 also acquires the measured welding time (step S4). These are input to first input unit 101A.

[0052] Next, welding section dividing unit 105 divides the welding section in weld bead 210 into a plurality of sections including at least a start processing section, and extracts the start processing section (step S5). Here, each divided section including the welding section and the start processing section will be described.

[0053] When forming the weld bead 210, as shown in FIG. 4, the wire feed speed W starts from zero and reaches a predetermined value W S1 The wire feed speed W is increased until it reaches a predetermined value W S1 is maintained for a predetermined period T3, and after the predetermined period T3 has elapsed, the wire feed speed W is reduced until it becomes zero again.

[0054] During a period T from when the wire feed speed W becomes zero to time t5 shown in FIG. 4, a welding current I flows through the welding wire 50. When an arc 80 is generated between the welding wire 50 and the base material 200, the arc 80 periodically grows and shrinks over time and eventually disappears. The welding torch 30 moves along the welding direction at a predetermined welding speed until time t4, when the wire feed speed W becomes zero, and a weld bead 210 is formed. The period from time t3 to time t4 is a period for performing a crater treatment, which will be described later. The period from time t4 to time t5 is a period for performing a stick check, which will be described later. In other words, the period T corresponds to the welding period T for forming the weld bead 210.

[0055] Assuming that welding period T is the aforementioned welding section, period T1 shown in FIG. 4 corresponds to a part of the start processing section (see FIGS. 5 and 7A). Period T2 corresponds to a part of the end processing section, and period T3 corresponds to a part of the main welding section. The start processing section is a period from when the torch SW of welding torch 30 is turned on until the feed speed of welding wire 50 held by welding torch 30, that is, the wire feed speed W, reaches a predetermined value W. S1(time t2 shown in FIG. 4). It takes a certain amount of time (=α) from when the torch SW is turned on until the welding wire 50 starts to move (time t1 shown in FIG. 4). Therefore, the start processing period T1a (see FIG. 5) is expressed by the relationship shown in equation (1).

[0056] T1a=T1+α (1) In addition, during the end processing period T2a, the wire feed speed W is set to a predetermined value W S1 This corresponds to the period T2 from a predetermined time point (time point t3 shown in Figure 4) where T1a is the welding time, to time point t5 shown in Figure 4. The main welding period T3a corresponds to the period obtained by excluding time points T1a and T2 from the welding period T, that is, the period T3 from time point t2 to time point t3 shown in Figure 4. In the following description, the periods T1 to T3 will be referred to as the first to third periods T1 to T3, respectively.

[0057] The first period T1 is divided into a period T11 from the start of feeding of welding wire 50 (time 0) to time t1, and a period T12 from time t1 to time T2. Period T11 is the period from when welding wire 50 is fed and welding current I starts to flow until welding torch 30 starts to move along the welding direction, and period T12 is the period from when welding torch 30 starts to move along the welding direction until wire feed speed W reaches a predetermined value W S1 In pulse welding, it takes a very short time for welding current I to flow through welding wire 50 and for arc 80 to be generated. If welding torch 30 is moved during this time, damage to weld bead 210 may occur. To prevent such damage from occurring, finite period T11 is provided. In the following description, period T11 will be referred to as the first sub-period or first sub-interval T11, and period T12 will be referred to as the second sub-period or second sub-interval T12.

[0058] Alternatively, the welding section can be considered as the length of weld bead 210 along the welding direction (hereinafter referred to as the bead length). In this case, as shown in FIG. 5, the welding section is assumed to have bead length L. In terms of welding time, the start processing section corresponds to the aforementioned period T1a, and when associated with bead length L, it corresponds to length L1 shown in FIG. 5. Similarly, in terms of welding time, the end processing section corresponds to the aforementioned period T2a, and when associated with bead length L, it corresponds to length L2. In terms of welding time, the main welding section corresponds to the aforementioned period T3a, and when associated with bead length L, it corresponds to length L3. Length L1 is a predetermined length along the welding direction from the welding start point of weld bead 210 toward the welding end point. Length L1 can be obtained, for example, by time-integrating the welding speed calculated by welding speed calculation unit 17 over period T1a. Length L2 is a predetermined length along the welding direction from the welding end point of weld bead 210 toward the welding start point. Length L2 is obtained by, for example, integrating the welding speed calculated by welding speed calculation unit 17 over time over the second period T2. Length L3 is the bead length L minus lengths L1 and L2. Length L3 is obtained by, for example, integrating the welding speed calculated by welding speed calculation unit 17 over time over the third period T3. In the following description, lengths L1 to L3 will be referred to as first to third bead lengths L1 to L3, respectively. Also, bead length L11 shown in FIG. 5 corresponds to the first sub-period T11, and bead length L12 corresponds to the second sub-period T12. In the following description, bead length L11 will be referred to as the first sub-bead length or first sub-interval L11, and period L12 will be referred to as the second sub-bead length or second sub-interval L12. As will be described later, the first sub-interval T11, L11 and the second sub-interval T12, L12 may differ in the first evaluation score determined in step S6, or the weighting coefficient set in step S7, or both.

[0059] As described above, the welding speed is calculated based on the speed command value sent from robot control unit 16. Therefore, the first to third bead lengths L1 to L3 can also be calculated based on the first to third periods T1 to T3 and the speed command value, respectively.

[0060] In addition, welding torch 30 may stop moving along the welding direction after the end of third period T3, which is the main welding section, or during second period T2. In this case, crater treatment or stick check, which will be described later, is performed at the welding end point.

[0061] In step S5, only the start processing section is extracted, regardless of whether the welding section is viewed as the welding period T or the bead length L. In the subsequent steps, attention is also focused on only the start processing section.

[0062] Next, the evaluation score calculation unit 108 determines the evaluation index set in step S4, that is, the first evaluation score related to the number of arc interruptions in the start processing section (step S6). The number of arc interruptions in the start processing section and the first evaluation score are associated in advance and stored in the storage unit 103 as an evaluation algorithm. The evaluation algorithm in this embodiment is a correspondence table between the number of arc interruptions and the first evaluation score. In this correspondence table, if the number of arc interruptions is 0, the first evaluation score is 100 points, and if the number of arc interruptions is 1, the first evaluation score is 60 points. If the number of arc interruptions is 2, the first evaluation score is 40 points, and if the number of arc interruptions is 3 or more, the first evaluation score is 20 points (see FIG. 6).

[0063] Furthermore, the weighting coefficient setting unit 109 sets a weighting coefficient according to the type of parameter set in step S5, i.e., time (step S7). In this embodiment, since only the start processing section is selected, the weighting coefficient is set to 1. Note that, as will be described later, when a first evaluation score is determined for each section obtained by dividing the welding section, a weighting coefficient is set for each of the multiple sections.

[0064] Next, the evaluation score calculation unit 108 calculates a second evaluation score by multiplying the first evaluation score determined in step S6 by a weighting coefficient (step S8). In this embodiment, the second evaluation score is the same value as the first evaluation score.

[0065] Finally, weld quality evaluation unit 110 evaluates weld bead 210, more specifically, the weld quality of the starting portion of weld bead 210, based on the second evaluation score (step S9). The weld quality is determined to be good or bad, and if the value of the second evaluation score is equal to or greater than a threshold value, the shape of the starting portion of weld bead 210 is determined to be good, and if the value of the second evaluation score is less than the threshold value, the shape is determined to be bad. The value of the second evaluation score and the threshold value for determining good or bad are associated with each other and stored in advance in storage unit 103. In this embodiment, the threshold value is 80 points.

[0066] 6A and 6B are examples of the evaluation results of the welding quality. Fig. 6A shows a case where the evaluation result is good, and Fig. 6B shows a case where the evaluation result is bad. The tables shown in Figs. 6A and 6B are stored in advance in memory unit 103 and are created by welding quality evaluation unit 110 using the set relationships of each associated value.

[0067] If the base material 200 is evaluated as good in step S9, the base material 200 on which the weld bead 210 is formed is also deemed to be a good product. If the base material 200 is evaluated as poor in step S9, the base material 200 on which the weld bead 210 is formed is also deemed to be a defective product. Note that there are cases where the weld bead 210 can be repaired by re-welding or the like, but this will not be discussed.

[0068] Here, we will explain the effect that the number of arc interruptions has on the weld quality of weld bead 210. Fig. 7A is a diagram showing a welding current waveform and a welding voltage waveform when there is no arc interruption. Fig. 7B is a planar schematic diagram showing the shape of a weld bead when arc welding is performed in the state shown in Fig. 7A. Fig. 8A is a diagram showing a welding current waveform and a welding voltage waveform when the number of arc interruptions is one. Fig. 8B is a planar schematic diagram showing the shape of a weld bead when arc welding is performed in the state shown in Fig. 8A. Fig. 9A is a diagram showing a welding current waveform and a welding voltage waveform when the number of arc interruptions is two. Fig. 9B is a planar schematic diagram showing the shape of a weld bead when arc welding is performed in the state shown in Fig. 9A.

[0069] As shown in FIG. 7A , in the start processing section, a high current is first passed through welding wire 50 to melt welding wire 50 and generate an arc 80 between welding wire 50 and base metal 200. Next, welding current I is reduced and welding voltage V is maintained at a constant value. During this time, welding wire 50 is fed forward toward base metal 200, and when wire feed speed W becomes higher than the melting rate of welding wire 50, welding wire 50 comes into contact with base metal 200. After contact, peak current and base current with a current value lower than the peak current are alternately passed through welding wire 50, and wire feed speed W is set to a predetermined value W S1 The first period T1 is usually 1 second or less, and typically several hundred milliseconds or less.

[0070] In the main welding section, the wire feed speed W is set to a predetermined value W S1 While maintaining the welding wire 50 at this temperature, the peak current and the base current are alternately passed through the welding wire 50. The third period T3 varies depending on the length L of the weld bead 210 to be formed. Typically, the third period T3 is several times to several tens of times longer than the first period T1.

[0071] In the end processing section, to ensure the height of the weld bead 210 from the surface of the base metal 200, arc welding may be performed by passing a welding current I through the welding wire 50 while the welding torch 30 is stopped. This process is also called crater processing. After the crater processing is completed, the wire feed speed W is gradually reduced to zero, and the welding current I and welding voltage V are also reduced to zero. Thereafter, a high voltage is applied as the welding voltage V while controlling the separation of the welding wire 50 from the base metal 200, and a process is performed to confirm that the welding current I does not flow. This process is also called a stick check, and if the welding current I flows, it is determined that the welding wire 50 and the base metal 200 have stuck to each other at the end of the bead 210. In this case, a high current may be passed through the welding wire 50 to melt the welding wire 50 and separate it from the base metal 200. That is, period T21 shown in FIG. 4 is the period from when welding torch 30 is stopped until crater processing is completed and immediately before a stick check is performed, and period T22 is the period from when the stick check is performed until the welding work is completed.

[0072] Normally, arc interruption does not occur during welding, as shown in Fig. 7A. Therefore, as shown by the dashed line in Fig. 7B, the outline of the starting end of weld bead 210 is generally semicircular or generally semielliptical, continuing from the main welded section.

[0073] On the other hand, at the start of welding, a phenomenon like a small explosion may occur due to the influence of the shape of the tip of welding wire 50, causing arc interruption for a short period of time before the welding proceeds to main welding. When such arc interruption occurs, the shape of weld bead 210 may be poor.

[0074] As shown in FIG. 8A, if arc interruption occurs once in the start processing section, the amount of heat input to base material 200 decreases, and the penetration of base material 200 becomes less than the set value. As a result, as shown by the dashed line in FIG. 8B, the width of the starting end of weld bead 210 becomes narrower than that shown in FIG. 7B. Note that the width here refers to the width in the direction perpendicular to the welding direction in a plan view. Furthermore, as shown in FIG. 9A, if arc interruption occurs twice in the start processing section, the amount of heat input to base material 200 further decreases. As a result, as shown by the dashed line in FIG. 9B, the width of the starting end of weld bead 210 becomes even narrower than that shown in FIG. 8B.

[0075] For example, if the welding portion of base material 200 is the butt joint portion of two plate materials, a decrease in the width of weld bead 210 may lead to a defective weld. According to this embodiment, by evaluating the welding quality of weld bead 210 using the above-described method, it is possible to simply and reliably detect the presence or absence of such defective weld portions or portions that may become defective welds.

[0076] [Effects, etc.] As described above, the method for evaluating welding quality according to this embodiment includes at least the following first to seventh steps.

[0077] In the first step (step S1 in FIG. 3), an evaluation index is set for the start processing section. This evaluation index corresponds to the welding quality of weld bead 210, and in this embodiment, the number of arc interruptions is set as the evaluation index.

[0078] In the second step (step S2 in FIG. 3), a parameter corresponding to the start processing section is set. As described above, if the welding section is regarded as time, this parameter corresponds to the first period T1 described above. The first period T1 is the period from when the switch of welding torch 30 is turned on until wire feed speed W, which is the feed speed of welding wire 50 held by welding torch 30, reaches a predetermined value W. S1The start processing section, specifically, the start processing period T1a, includes a first period T1. The first period T1 is derived from the welding time and the change in the wire feed speed W over time.

[0079] In the third step (steps S3 and S4 in FIG. 3), base material 200 is welded to form weld bead 210, and physical quantities during welding are measured. These physical quantities include welding current I, welding voltage V, and welding time.

[0080] In a fourth step (step S5 in FIG. 3), the welding section in weld bead 210 is divided into a plurality of sections including at least a start processing section. In this embodiment, the welding section is divided into a start processing section and other sections.

[0081] On the other hand, when the parameter is considered to be bead length L of weld bead 210, the parameter is the above-mentioned first bead length L1. First bead length L1 is a predetermined length along the welding direction from the welding start point of weld bead 210 as the base point toward the welding end point.

[0082] As described above, first bead length L1 is derived from the time integral of the welding speed. First bead length L1 can also be derived based on the welding time and a speed command value that is sent to robot 60 holding welding torch 30 and determines the movement speed of the tip of welding torch 30.

[0083] In the fifth step (step S6 in FIG. 3), a first evaluation score for the evaluation index is determined based on the physical quantity measured in the third step and an evaluation algorithm for the evaluation index.

[0084] In the sixth step (steps S7 and S8 in FIG. 3), the first evaluation score is weighted using a weighting coefficient set based on the parameters set in the second step to calculate a second evaluation score.

[0085] In a seventh step (step S9 in FIG. 3), the welding quality of weld bead 210 is evaluated based on the second evaluation score calculated in the sixth step.

[0086] The start processing section is a period from when the switch of the welding torch 30 is turned on until the feed speed of the welding wire 50 held by the welding torch 30 reaches a predetermined value W S1 The start processing section includes a first period T1 until the welding start point of weld bead 210 is reached. The start processing section may be defined as first bead length L1. First bead length L1 is a predetermined length along the welding direction from the welding start point of weld bead 210 as the base point toward the welding end point.

[0087] According to this embodiment, when evaluating the welding quality of the weld bead 210, the starting end formed during the start processing period T1a including the first period T1, in other words, the welding quality of the starting end of the first bead length L1, can be easily and reliably evaluated.

[0088] As mentioned above, the conventional methods disclosed in Patent Documents 1 to 3 do not evaluate the welding quality focusing on the start processing section described in the present specification. Patent Document 2 discloses dividing the welding point into multiple sections and evaluating the welding quality for each section using a judgment algorithm corresponding to each section after division.

[0089] However, as shown in this embodiment, Patent Document 2 does not disclose anything about focusing on the start processing section and evaluating the welding quality of the weld bead 210 in the start processing section using an evaluation index suitable for evaluating the quality of the start processing section, in this case the number of arc interruptions.

[0090] In addition, in this welding section, as is conventionally known, it is possible to monitor the welding current waveform and welding voltage waveform in real time and evaluate the welding quality based on the monitoring results.

[0091] However, when the main welding section, in this case the third period T3, is short and not significantly different from the first period T1 corresponding to the start processing section, for example, in tap welding, it is difficult to evaluate the welding quality of the weld bead 210 using conventional methods.

[0092] On the other hand, according to this embodiment, the welding quality of the weld bead 210 in the start processing section can be evaluated, and even if the difference in the period or the length of the weld bead 210 between the start processing section and the main welding section is small, the welding quality of the entire weld bead 210 can be appropriately evaluated.

[0093] Furthermore, as shown in this embodiment, when evaluating the welding quality of weld bead 210 in the start processing section, it is preferable to set the evaluation index to the number of arc interruptions.

[0094] As mentioned above, if arc interruption occurs in the start processing section, even if there is no abnormality in the actual welding section, the width of the starting end of the weld bead 210 will become narrower, which may not only result in poor appearance of the weld bead 210 but also cause poor welding of the base material 200.

[0095] On the other hand, according to this embodiment, the first evaluation score is set in accordance with the number of arc interruptions, so it is possible to easily evaluate whether or not a shape defect has occurred at the starting end of weld bead 210. Also, while the presence or absence of a shape defect in weld bead 210 is usually determined by visual inspection or image recognition, according to this embodiment, the presence or absence and degree of shape defect can be evaluated indirectly from the monitoring results of the welding current waveform and welding voltage waveform, thereby reducing the need for inspection equipment and the number of inspection steps.

[0096] The start processing interval includes a first sub-interval T11, L11 and a second sub-interval T12, L12. First sub-interval T11 is the period from when welding wire 50 starts to be fed and welding current I starts to flow until welding torch 30 starts to move, and first sub-interval L11 is the length along the welding direction of weld bead 210 formed in first sub-interval T11.

[0097] The second sub-section T12 is a period from when the welding torch 30 starts moving until the wire feed speed W reaches a predetermined value W S1 and the start processing section ends, and second sub-section L12 is the length along the welding direction of weld bead 210 formed in second sub-period T12.

[0098] In this case, it is preferable that the first evaluation scores and / or weighting coefficients are different between the first sub-interval T11, L11 and the second sub-interval T12, L12.

[0099] Even if arc interruption occurs before welding torch 30 starts to move, it has little effect on the shape of weld bead 210. On the other hand, if arc interruption occurs after welding torch 30 starts to move, as described above, there is a risk that the width of the starting end of weld bead 210 will become narrower.

[0100] Therefore, when evaluating the welding quality in the start processing section using the first evaluation score, it is preferable to further divide the start processing section into a first sub-section T11, L11 and a second sub-section T12, L12 and perform evaluation for each section. Furthermore, by changing the first evaluation score for the number of arc interruptions in each section, the accuracy of the evaluation of welding quality can be further improved. For example, in the second sub-sections T12, L12, the relationship between the number of arc interruptions and the first evaluation score is as shown in FIG. 6. On the other hand, in the first sub-sections T11, L11, the evaluation algorithm for the number of arc interruptions may be set as follows. For example, if the number of arc interruptions is 0, the first evaluation score is 100 points, and if the number of arc interruptions is 1, the first evaluation score is 90 points. If the number of arc interruptions is 2, the first evaluation score is 80 points, and if the number of arc interruptions is 3 or more, the first evaluation score is 50 points.

[0101] In this case, in the second sub-intervals T12 and L12, for example, the evaluation algorithm is set as follows: if the number of arc interruptions is 0, the first evaluation score is 100 points; if the number of arc interruptions is 1, the first evaluation score is 40 points; if the number of arc interruptions is 2 or more, the first evaluation score is 10 points.

[0102] As described above, arc interruptions that occur in first sub-intervals T11 and L11 have little effect on the shape of the starting end of weld bead 210. Therefore, in first sub-intervals T11 and L11, the degree of decrease in the first evaluation score relative to an increase in the number of arc interruptions may be small.

[0103] On the other hand, an arc interruption that occurs in the second sub-interval T12, L12 may cause a defective shape of the starting end of the weld bead 210. In arc welding, the timing at which the arc interruption occurs is likely to occur after the welding wire 50 first comes into contact with the base material 200 and short-circuits. If the arc interruption occurs after the first short-circuit, there is a possibility that the arc interruption will occur again after the welding wire 50 short-circuits with the base material 200. The first arc interruption occurs before the welding torch 30 starts moving, that is, in the first sub-interval T11, L11.

[0104] Therefore, by making the rate of decrease in the first evaluation score relative to an increase in the number of arc interruptions greater in the second sub-interval T12, L12 than in the first sub-interval T11, L11, it is possible to accurately evaluate whether or not a defective shape has occurred at the starting end of the weld bead 210 by counting the number of arc interruptions.

[0105] Furthermore, even when the start processing section is not divided into a first sub-section and a second sub-section, the presence or absence of a defective shape of weld bead 210 due to arc interruption can be accurately evaluated by increasing the difference in first evaluation score between when the number of arc interruptions is 1 and when it is 2 or more. For example, if the number of arc interruptions is 0, the first evaluation score is 100 points, and if the number of arc interruptions is 1, the first evaluation score is 80 points. Also, if the number of arc interruptions is 2, the first evaluation score is 30 points, and if the number of arc interruptions is 3 or more, the first evaluation score is 20 points.

[0106] In this embodiment, the weighting coefficient is 1, but as will be described later, when evaluating the welding quality of weld bead 210 including the main welding section and the end processing section, the weighting coefficient set in the start processing section will be a value different from 1, for example, smaller than 1. In this case, by making the degree of decrease in the first evaluation score in response to an increase in the number of arc interruptions the same between the first sub-section and the second sub-section, while making the weighting coefficients different, it is possible to accurately evaluate the presence or absence of a shape defect in weld bead 210 due to arc interruption. Specifically, the weighting coefficient set in the second sub-sections T12 and L12 is made larger than the weighting coefficient set in the first sub-sections T11 and L11.

[0107] Furthermore, both the degree of decrease in the first evaluation score in response to an increase in the number of arc interruptions and the weighting coefficient may be made different between the first sub-interval T11, L11 and the second sub-interval T12, L12. These settings can be changed as appropriate depending on the level of welding quality required in the start processing interval.

[0108] The parameter set in the fourth step may be either the time, that is, the first period T1, or the length, that is, the first bead length L1.

[0109] By setting the parameter to the first period T1, it becomes easy to determine whether or not the welding current waveform or welding voltage waveform has changed abnormally during the start processing period T1a, essentially during the first period T1. It also becomes easy to count the number of times the arc has been interrupted.

[0110] On the other hand, when the parameter is first bead length L1, it is possible to easily confirm the consistency between the inspection results of the appearance inspection of weld bead 210 performed after welding and the evaluation results of the welding quality.

[0111] The welding quality evaluation device according to this embodiment includes at least an input unit 101, a welding section division unit 105, an evaluation index setting unit 106, a parameter setting unit 107, an evaluation score calculation unit 108, a weighting coefficient setting unit 109, and a welding quality evaluation unit 110.

[0112] At least physical quantities measured during welding of base material 200 are input to input unit 101. These physical quantities include welding current I, welding voltage V, and welding time.

[0113] Welding section dividing unit 105 divides the welding section of weld bead 210 into a plurality of sections including at least a start processing section.

[0114] The evaluation index setting unit 106 sets an evaluation index corresponding to the welding quality in the start processing section.

[0115] The parameter setting unit 107 sets parameters corresponding to the start processing interval based at least on the physical quantities input to the input unit 101 .

[0116] The weighting coefficient setting unit 109 sets the weighting coefficient based on the parameter, and more specifically, the weighting coefficient setting unit 109 sets the weighting coefficient based on the type of parameter, in this case, time.

[0117] The evaluation score calculation unit 108 determines a first evaluation score related to the evaluation index based on the physical quantity input to the input unit 101 and the evaluation algorithm related to the evaluation index. Furthermore, the evaluation score calculation unit 108 weights the first evaluation score using the weighting coefficient set by the weighting coefficient setting unit 109, and calculates a second evaluation score. Note that the evaluation algorithm is stored in advance in the storage unit 103 in association with the evaluation index, and is read out by the evaluation score calculation unit 108 when determining the first evaluation score.

[0118] Weld quality evaluation unit 110 evaluates the weld quality of weld bead 210 based on the second evaluation score. According to this embodiment, when evaluating the welding quality of the weld bead 210, the starting end formed during the start processing period T1a including the first period T1, in other words, the welding quality of the starting end of the first bead length L1, can be easily and reliably evaluated.

[0119] Furthermore, according to this embodiment, the welding quality of the weld bead 210 in the start processing section can be evaluated, and even if the difference in the period or the length of the weld bead 210 between the start processing section and the main welding section is small, the welding quality of the entire weld bead 210 can be appropriately evaluated.

[0120] Furthermore, welding section dividing unit 105 may further divide the start processing section into a first sub-section T11, L11 and a second sub-section T12, L12. In this case, evaluation score calculation unit 108 may set the degree of decrease in the first evaluation score relative to an increase in the number of arc interruptions, which is the evaluation index, to be different between the first sub-section T11, L11 and the second sub-section T12, L12. Alternatively, weighting coefficient setting unit 109 may set different weighting coefficients between the first sub-section T11, L11 and the second sub-section T12, L12. Alternatively, both evaluation score calculation unit 108 and weighting coefficient setting unit 109 may set different weighting coefficients between the first sub-section T11, L11 and the second sub-section T12, L12, as described above. This further improves the accuracy of the evaluation of the welding quality of weld bead 210.

[0121] The parameter set by parameter setting unit 107 is time, that is, either the first period or the length of weld bead 210 at the starting end. In either case, parameter setting unit 107 can set the parameter based on the welding time and the above-mentioned speed command value.

[0122] The welding system 300 according to this embodiment includes at least an arc welding device 20 that welds a base material 200 and a welding quality evaluation device 100.

[0123] By configuring welding system 300 in this manner, the welding quality of weld bead 210 formed on base material 200 can be evaluated simply and reliably using arc welding device 20.

[0124] (Embodiment 2) Fig. 10 is a diagram showing another evaluation index in the start processing section according to embodiment 2. For ease of explanation, in Fig. 10 and the following drawings, the same parts as those in embodiment 1 are denoted by the same reference numerals, and detailed explanations thereof will be omitted.

[0125] Fig. 10 shows the welding current waveform and the welding voltage waveform in the same way as Fig. 7A, except that the evaluation index shown is different from the number of arc interruptions, which is the evaluation index shown in the first embodiment.

[0126] For example, Figure 10 shows the maximum short circuit time, T Smax Also, Fig. 10 shows the welding current value I 1S Also, Fig. 10 shows the time to the first short circuit T 1S This shows:

[0127] The maximum short circuit duration measured T Smax , welding current value at the first short circuit I 1S , and the time to the first short circuit T 1S Any of these can be used as an evaluation index for the welding quality of weld bead 210 in the start processing section, instead of the number of arc interruptions.

[0128] If the short circuit time exceeds the first predetermined value, the amount of heat input to the base material 200 may be insufficient, and heat may be input to the base material 200 while the welding wire 50 is adhering to the base material 200. In such a case, if the short circuit is released, there is a risk that spatter may occur significantly. There is also a risk that the welding wire 50 may be blown away and scattered on the surface of the base material 200. In either case, the welding quality may be reduced.

[0129] Therefore, the maximum short circuit time T Smax and the first evaluation score are associated with each other to construct an evaluation algorithm, which is then stored in the storage unit 103. If necessary, the evaluation algorithm is read out to the evaluation score calculation unit 108 and used to determine the first evaluation score. In the evaluation algorithm, for example, the maximum value T SmaxWhen the first evaluation score exceeds a first predetermined value, the degree of increase is associated in advance with the degree of decrease in the first evaluation score. In this way, it is possible to easily evaluate whether or not the amount of spatter or other flying matter adhering to the surface of weld bead 210 or base material 200 in the start processing section is more than the allowable number.

[0130] In addition, the welding current value I 1S If the welding current I exceeds the second predetermined value, spatter may occur. 1S When the first evaluation score exceeds the second predetermined value, an evaluation algorithm is prepared that associates the degree of increase with the degree of decrease in the first evaluation score. In this way, it is possible to easily evaluate whether or not the amount of spatter or other debris adhering to the surface of weld bead 210 or base material 200 in the start processing section is more than the allowable number.

[0131] Also, the time until the first short circuit T 1S If the third predetermined value is exceeded, there is a possibility that an arc failure has occurred for some reason. In other words, there is a high possibility that a false arc interruption has occurred before the first short circuit.

[0132] If this occurs, the starting end of weld bead 210 may have a poor shape, which may result in a decrease in welding quality. Alternatively, the amount of heat input to base material 200 may be insufficient, which may result in a decrease in welding quality at the starting end of weld bead 210.

[0133] In such cases, the time to the first short circuit T 1S When the first evaluation score exceeds the third predetermined value, an evaluation algorithm is prepared in advance that associates the degree of increase with the degree of decrease in the first evaluation score. By doing so, it is possible to simply and reliably evaluate the presence or absence of a shape defect at the starting end of weld bead 210, and ultimately the welding quality.

[0134] (Embodiment 3) Fig. 11 is a flowchart showing the procedure for evaluating the weld quality according to embodiment 3. Note that steps S13 and S14 in Fig. 11 are similar to steps S3 and S4 in Fig. 3, respectively, and therefore will not be described.

[0135] The procedure for evaluating the weld quality of this embodiment shown in FIG. 11 differs from the procedure for evaluating the weld quality of the first embodiment shown in FIG. 3 in the following points.

[0136] First, in steps S11, S12, and S17, evaluation indices, parameters, and weighting coefficients are set for each of the three sections. Note that the evaluation indices set in step S11 are different for the start processing section, the main welding section, and the end processing section.

[0137] In step S15, the welding section dividing unit 105 divides the welding section into three sections: a start processing section, a main welding section, and an end processing section, and further extracts these three sections as targets for subsequent evaluation.

[0138] In addition, in step S16, a first evaluation score is determined for each of the three sections. In this case, the first evaluation score is determined for each of the three sections based on the physical quantity acquired in step S14 and the evaluation algorithm associated with each evaluation index and stored in the storage unit 103.

[0139] In step S18, the first evaluation scores determined in step S16 are weighted by multiplying them by the weighting coefficients set in step S17 for each of the three sections, thereby calculating second evaluation scores.

[0140] In step S19, the second evaluation scores for each section calculated in step S18 are added together to calculate a total evaluation score. In step S20, the welding quality of weld bead 210 is evaluated based on the total evaluation score.

[0141] That is, the method for evaluating weld quality according to this embodiment further includes an eighth step in addition to the first to seventh steps described above, but the contents of the first and second steps and the fourth step and thereafter are different from those shown in the first embodiment.

[0142] In the first step (step S11 in FIG. 11), an evaluation index is set for each of the three sections. The evaluation index is different for each of the three sections.

[0143] In the second step (step S12 in FIG. 11), parameters are set for each of the three periods. In this embodiment, the parameters are set for the first to third periods T1 to T3 described above.

[0144] In the fourth step (step S15 in FIG. 11), the welding section is divided into three different sections, that is, a start processing section, a main welding section, and an end processing section.

[0145] In the fifth step (step S16 in FIG. 11), a first evaluation score is determined for each of the three sections based on the physical quantity measured in the third step and an evaluation algorithm related to the evaluation index.

[0146] In the sixth step (steps S17 and S18 in FIG. 11), the first evaluation score is weighted for each of the three sections using the weighting coefficients set based on the parameters set in the second step to calculate a second evaluation score. In this embodiment, the weighting coefficients are different for each of the three sections.

[0147] The eighth step (step S19 in FIG. 11) is executed between the sixth step and the seventh step (step S20 in FIG. 11). In the eighth step, the three second evaluation scores calculated in the sixth step are added together to calculate a total evaluation score.

[0148] In a seventh step, the welding quality of weld bead 210 is evaluated based on the overall evaluation score calculated in the eighth step. Note that the parameters set in the second step may be the first to third bead lengths L1 to L3 described above.

[0149] In the welding quality evaluation device 100 according to this embodiment, the evaluation index setting unit 106 sets an evaluation index for each of the three sections. In this embodiment, the evaluation index setting unit 106 sets a different evaluation index for each of the three sections.

[0150] The parameter setting unit 107 sets parameters corresponding to each of the three periods. In this embodiment, the parameter setting unit 107 sets the parameters for the first to third periods T1 to T3, respectively.

[0151] The weighting coefficient setting unit 109 sets a weighting coefficient for each of the three intervals based on the type of parameter and the type of interval. In this embodiment, the weighting coefficient setting unit 109 sets different weighting coefficients for each of the three intervals.

[0152] The evaluation score calculation unit 108 determines a first evaluation score for each of the three sections based on the aforementioned physical quantities input to the input unit 101 and the aforementioned evaluation algorithm. The evaluation score calculation unit 108 also weights the first evaluation score using the weighting coefficient set by the weighting coefficient setting unit 109 to calculate a second evaluation score. Furthermore, the evaluation score calculation unit 108 adds the second evaluation scores for each of the three sections to calculate a total evaluation score.

[0153] The welding quality evaluation unit 110 evaluates the welding quality of the welded portion based on the overall evaluation score. The parameters set by the parameter setting unit 107 may be the first to third bead lengths L1 to L3 described above.

[0154] According to this embodiment, different evaluation indices are set for the start processing section, the main welding section, and the end processing section, and the welding quality of the entire weld bead 210 is evaluated based on a total evaluation score obtained by adding up the second evaluation scores calculated for each section.

[0155] The state of the arc 80 in pulse welding, the welding speed, and the wire feed speed W are different in the start processing section, the main welding section, and the end processing section. According to this embodiment, by determining the first evaluation score using different evaluation indices for each of the three sections in accordance with these differences, it is possible to appropriately evaluate the welding quality for each section. This makes it easy to identify the location of the abnormality if there is an abnormality in the welding quality of the weld bead 210.

[0156] The evaluation results of the welding quality in this embodiment are shown below. Fig. 12A shows an example of the evaluation results of the welding quality in embodiment 3, and Fig. 12B shows another example of the evaluation results of the welding quality. Fig. 13 shows the welding current waveform and the welding voltage waveform when a long-term short circuit occurs.

[0157] In this embodiment, weld bead 210 was formed using pulse welding, as in embodiments 1 and 2. The evaluation index for each section is as shown in FIGS. 12A and 12B. That is, the evaluation index for the start processing section is the number of arc interruptions described above. The evaluation algorithm, i.e., the degree of decrease in the first evaluation score relative to an increase in the number of arc interruptions, is also the same as that shown in embodiment 1.

[0158] On the other hand, in this embodiment, the evaluation index for the main welding section is set to the long-time short circuit ratio. Note that a long-time short circuit is a short circuit that occurs at a timing other than the set timing, and refers to a short circuit in which the short circuit duration exceeds a predetermined threshold. For example, as shown in FIG. 13, even in the start processing section, a long-time short circuit (period T LS1 ) can occur, and even in this welding section, a long-term short circuit (period T LS2) can occur. If a long-term short circuit occurs at a time other than the set timing, the amount of spatter increases, the width of the weld bead 210 becomes narrower, and other adverse effects are exerted on the welding quality. Furthermore, the effect of a long-term short circuit on the welding quality is more pronounced in the main welding section.

[0159] Therefore, in this embodiment, the evaluation algorithm for the main welding section is set as follows: When no long-term short circuit occurs in the main welding section, the score is set to 100, and the ratio between the main welding period T3a, essentially the third period T3, and the long-term short circuit period (hereinafter referred to as the long-term short circuit ratio) is calculated, and the minor short circuit ratio expressed as a percentage is subtracted from 100 to determine the first evaluation score. Note that the method for determining the first evaluation score is not particularly limited to this. For example, the range of the long-term short circuit ratio may be set in multiple stages, and the first evaluation score may be set according to each stage.

[0160] Furthermore, the evaluation index for the end processing section is the presence or absence of a stick check. When a stick check occurs, the welding wire 50 is melted with a high current and peeled off from the base material 200, causing the molten welding wire 50 to scatter, resulting in a decrease in welding quality. In this embodiment, the evaluation algorithm for the end processing section is set as follows: If a stick check is performed, the first evaluation score is set to 50 points, and if a stick check is not performed, the first evaluation score is set to 100 points. However, this is not particularly limited, and the difference in the first evaluation score depending on the presence or absence of a stick check may be changed as appropriate depending on the level of welding quality required.

[0161] 12A and 12B, the parameter is set to time, and the weighting coefficient is the ratio of each period to the welding period T.

[0162] 12A, weld bead 210 is formed with a shape that extends elongated in the welding direction. Compared to third period T3 (=9.4 sec) corresponding to the main welding period, first period T1 (=0.5 sec) corresponding to the start processing period and second period T2 (=0.1 sec) corresponding to the end processing period are each shorter by one digit or more.

[0163] The example shown in Figure 12B is an evaluation result for weld bead 210 formed by tap welding as described above. In this case, the third period T3 (= 1.4 seconds) is shorter by nearly an order of magnitude than the example shown in Figure 12A. Meanwhile, the first period T1 and the third period T3 have the same values ​​as those shown in Figure 12A. Therefore, the ratio of the first period T1 and the second period T2 (= 0.1 seconds) to the third period T3 is larger than the example shown in Figure 12A.

[0164] In both the examples shown in FIGS. 12A and 12B, arc interruptions occurred twice in the first period T1, and a stick check was performed in the second period T2. However, as mentioned above, the weighting coefficient is determined by the ratio of each period to the welding period. Therefore, in the example shown in FIG. 12B, the ratio of the second evaluation score in the first period T1 or the second period T2 to the overall evaluation score is larger than in the example shown in FIG. 12A. Therefore, in evaluating welding quality, if an overall evaluation score of 80 points or more is considered pass (OK) and an overall evaluation score of less than 80 points is considered fail (NG), the example shown in FIG. 12A has a pass overall evaluation score of 87.6 points. On the other hand, the example shown in FIG. 12B has a fail overall evaluation score of 78 points.

[0165] As described above, according to this embodiment, by selecting an appropriate evaluation index for each section and selecting time as a parameter, the welding quality can be evaluated simply and reliably according to the welding period T.

[0166] In this embodiment, the welding section is divided into three sections and the welding quality is evaluated for each section, but this is not particularly limited. For example, the start processing section and the main welding section may be the subjects of welding quality evaluation, or the main welding section and the end processing section may be the subjects of welding quality evaluation. Furthermore, the start processing section and the end processing section may be the subjects of welding quality evaluation. The sections to be evaluated for welding quality can be changed as appropriate depending on the required welding quality items, level, etc.

[0167] Furthermore, in this embodiment, the welding section is divided into three sections, but it may be divided into two or more sections. In that case, "three" in this embodiment is to be read as "multiple." Furthermore, it is not necessary for all of the multiple sections to be subject to welding quality evaluation. Only the sections that need to be extracted as subjects for welding quality evaluation may be selected depending on the required welding quality items, level, etc.

[0168] (Embodiment 4) Fig. 14 is a diagram showing various output waveforms during short circuit welding according to embodiment 4. Fig. 15A is an example of an evaluation result of welding quality according to embodiment 4. Fig. 15B is another example of an evaluation result of welding quality according to embodiment 4.

[0169] In this embodiment, a case where a weld bead 210 is formed by short-circuit welding will be described as an example. Fig. 14 shows the time variations of the wire feed speed W, welding voltage V, welding current I, and droplet transfer state D at the tip of the welding wire 50 during short-circuit welding.

[0170] First, the torch SW is operated, and feeding of the welding wire 50 is started at the wire feed speed W1 from the time when the torch SW signal is turned on, that is, from the time Wst when the welding start command is issued. Then, from the time Wst when the welding start command is issued, or from the time Ed when the welding start command is issued and the occurrence of a short circuit between the welding wire 50 and the base material 200 is detected, the short circuit welding control unit 11 controls the welding output, and short circuit welding is performed between the welding wire 50 and the base material 200. In this case, the short circuit welding period T SIn this state, a period in which an arc 80 is generated and grows further (see (a) of droplet transfer state D in FIG. 14) and a period in which the welding wire 50 and the base material 200 are short-circuited (see (b) of droplet transfer state D in FIG. 14) are alternately repeated.

[0171] As shown in FIG. 14, the short-circuit welding period T S In this case, the wire feed speed W periodically changes from a positive value to a negative value and from a negative value to a positive value. When the wire feed speed W is a positive value, it is called forward feed or a forward feed state, and when it is a negative value, it is called reverse feed or a reverse feed state. In other words, during the short circuit welding period T S In this example, the welding wire 50 moves relative to the base material 200 while periodically repeating forward and reverse feed.

[0172] During the first period T1, the wire feed speed W alternates between forward and reverse feed, and the time average value is a constant value W S At the end of the first period T1, the time average value of the wire feed speed W becomes a constant value W S 14, the welding torch 30 stops and crater processing is performed. In the example shown in FIG. 14, the welding wire 50 is fixed to the base material 200 before the stick check. Therefore, a high current is passed through the welding wire 50 during the stick check to separate the welding wire 50 from the base material 200.

[0173] In this case, the start processing section begins when the feeding of the welding wire 50 held by the welding torch 30 is started and the feeding speed is kept constant at a constant average value W SAs described above, the first period T1 can be divided into a first sub-period T11 and a second sub-period T12. The first sub-period T11 is the period from when the welding wire 50 starts to be fed and the welding current I starts to flow until the wire feed speed W reaches the above-mentioned time Ed. The second sub-period T12 is the period from when the wire feed speed W reaches the average value W S During the second period T2, the welding current I decreases stepwise and then reaches a peak value higher than the previous value. At this point, a stick check is performed. The completion of the stick check marks the end of welding.

[0174] The method for evaluating the welding quality in this embodiment is the same as that shown in embodiment 3. However, in this embodiment, different evaluation indexes are set for the start processing section and the main welding section, and the welding quality of the entire weld bead 210 is evaluated based on a total evaluation score obtained by adding up the second evaluation scores calculated for each section.

[0175] The state of the arc 80 during short-circuit welding and the change over time in the wire feed speed W are different between the start processing section and the main welding section. According to this embodiment, the first evaluation score is determined using different evaluation indices for each of the two sections in accordance with these differences, thereby making it possible to appropriately evaluate the welding quality for each section. This makes it easy to identify the location of the abnormality if there is an abnormality in the welding quality of the weld bead 210.

[0176] Below, we will show examples of the evaluation results of welding quality in this embodiment. The evaluation index for each section is as shown in Figures 15A and 15B. The evaluation index for the start processing section is the short circuit duration at the time of the initial short circuit. If the heat input at the start of welding is small, a long short circuit occurs, and the shape of weld bead 210 becomes distorted. The evaluation algorithm for the start processing section is set as follows: A predetermined threshold is set for the short circuit duration described above, and if a long short circuit exceeding the threshold occurs, the first evaluation score is set to 40 points, and if it does not occur, the score is set to 100 points.

[0177] In this embodiment, the evaluation index for the main welding section is set to the number of arc interruptions. Arc interruptions during main welding have a significant impact on the appearance of the weld bead 210 and, ultimately, on the welding quality. In this embodiment, the evaluation algorithm for the main welding section is set as follows: If the number of arc interruptions in the main welding section is zero, the first evaluation score is 100 points, and if the number of arc interruptions is one, the first evaluation score is 40 points. If the number of arc interruptions is two or more, the first evaluation score is 20 points. However, the degree to which the first evaluation score decreases with an increase in the number of arc interruptions is not particularly limited to this, and can be changed appropriately depending on the required level of welding quality, etc.

[0178] 15A and 15B, the parameters are set to the bead lengths, specifically the first bead length L1 and the third bead length L3, and the weighting coefficients are set to the ratios of the respective bead lengths to the sum of the first bead length L1 and the third bead length L3.

[0179] 15A, weld bead 210 is formed in a shape that extends long in the welding direction. Compared to first bead length L1 (= 10 mm) corresponding to the start processing section, third bead length L3 (= 190 mm) corresponding to the main welding section is longer by one order of magnitude or more.

[0180] 14B shows the evaluation results for weld bead 210 formed by tap welding. In this case, first bead length L1 (= 10 mm) is the same as third bead length L3 (= 10 mm), so the ratio of first bead length L1 to third bead length L3 is greater than in the example shown in FIG. 15A.

[0181] In both the examples shown in Figures 15A and 15B, there is a short circuit duration exceeding the threshold value during the start processing period, i.e., the aforementioned long-term short circuit. Furthermore, no arc interruption occurred during the actual welding period. However, as previously mentioned, the weighting coefficient is determined by the ratio of each bead length to the sum of the first bead length L1 and the third bead length L3. Therefore, in the example shown in Figure 15B, the ratio of the second evaluation score for the third bead length L3 to the overall evaluation score is larger than in the example shown in Figure 15A. Therefore, in evaluating welding quality, if an overall evaluation score of 80 points or more is considered pass (OK) and one below 80 points is considered fail (NG), the example shown in Figure 15A has a pass overall evaluation score of 97 points. On the other hand, the example shown in Figure 15B has a fail overall evaluation score of 70 points.

[0182] As described above, according to this embodiment, by selecting an appropriate evaluation index for each section and selecting the bead length as a parameter, the welding quality can be simply and reliably evaluated according to the length of weld bead 210.

[0183] In this embodiment, the welding section is divided into two sections and the welding quality is evaluated for each section, but this is not particularly limited. For example, the start processing section, the main welding section, and the end processing section may be the subjects of welding quality evaluation, or the main welding section and the end processing section may be the subjects of welding quality evaluation. Furthermore, the start processing section and the end processing section may be the subjects of welding quality evaluation. The sections to be evaluated for welding quality can be changed as appropriate depending on the required welding quality items, level, etc.

[0184] (Other embodiments) In the first, second, and fourth embodiments, the evaluation algorithm for each section is a correspondence table between numerical values ​​related to the evaluation index and the first evaluation score, and the correspondence table is set in advance. However, this is not particularly limited, and correspondence tables may be added depending on the required welding quality items. Furthermore, the numerical values ​​in the correspondence table may be rewritten later depending on the required level of welding quality, etc.

[0185] The form of the evaluation algorithm is not limited to a correspondence table. For example, the evaluation index may be a variable, and any function relating to the variable may be used as the evaluation algorithm. [Industrial Applicability]

[0186] The welding quality evaluation method according to the present disclosure is useful because it allows for easy and reliable evaluation of the welding quality of the entire welding area by evaluating the welding quality for each of multiple sections, including a specified section after the start of welding or before the end of welding. [Explanation of symbols]

[0187] 1. Input power supply (three-phase AC power supply) 2. Main transformer 3 Primary side rectifier 4 Switching section 5 DCL (reactor) 6 Secondary rectifier 7 Welding current detector 8 Welding voltage detector 9 Control switching unit 10 Output control section 11 Short circuit welding control unit 12 Pulse welding control unit 13 Wire feed speed control unit 14 Wire feed speed detector 15 Wire feed speed calculation section 16 Robot control unit 17 Welding speed calculation section 20 Arc welding equipment 30 Welding Torch 30A nozzle 31 Welding Tip 40 Wire feeder 50 welding wire 60 Robot 70 Power Cable 80 Arc 100 Welding quality evaluation device 101 Input section 101A 1st input section 101B Second input section 102 Output section 103 Storage section 104 Display section 105 Welded section division 106 Evaluation Index Setting Department 107 Parameter setting section 108 Evaluation score calculation section 109 Weighting coefficient setting unit 110 Welding Quality Evaluation Department 200 Base material 210 Weld Bead 300 Welding System

Claims

1. A method for evaluating welding quality in arc welding, comprising: a first step of setting an evaluation index corresponding to welding quality in at least a start processing section; a second step of setting parameters corresponding to the start processing section; a third step of welding the base material to form a weld and measuring a physical quantity during welding; a fourth step of dividing a welding section at the welding location into a plurality of sections including at least the start processing section; a fifth step of determining a first evaluation score based on the physical quantity measured in the third step and an evaluation algorithm related to the evaluation index; a sixth step of weighting the first evaluation score using a weighting coefficient set based on the parameter set in the second step to calculate a second evaluation score; and a seventh step of evaluating the welding quality of the welded portion based on the second evaluation score calculated in the sixth step, a welding quality evaluation method, characterized in that the start processing section includes a first period from when a welding torch switch is turned on to when a feed speed of a welding wire held by the welding torch reaches a predetermined value.

2. The method for evaluating weld quality according to claim 1, the start processing interval includes a first subinterval and a second subinterval, the first sub-section is a period from when the welding wire starts to be fed and when the welding current starts to flow until when the welding torch starts to move, the second sub-section is a period from when the welding torch starts to move until the feed speed of the welding wire reaches the predetermined value and the start processing section ends, A method for evaluating welding quality, wherein the first evaluation score or the weighting coefficient, or both, are different between the first sub-interval and the second sub-interval.

3. The method for evaluating weld quality according to claim 1, A method for evaluating welding quality, wherein the evaluation index is the maximum number of arc interruptions or the maximum short circuit time.

4. The method for evaluating weld quality according to claim 1, In the first step, the evaluation index is set for each of the plurality of sections; In the second step, the parameters are set in each of the plurality of sections; In the fifth step, the first evaluation score is determined for each of the plurality of sections based on the physical quantity measured in the first step and the evaluation algorithm related to the evaluation index; In the sixth step, for each of the plurality of sections, the first evaluation score is weighted using the weighting coefficient set based on the parameters set in the second step to calculate the second evaluation score; An eighth step is further provided between the sixth step and the seventh step, in which a total evaluation score is calculated by adding up the second evaluation scores calculated in the sixth step, In the seventh step, the welding quality of the welded portion is evaluated based on the comprehensive evaluation score calculated in the eighth step; The plurality of sections include at least two of the start processing section, the end processing section, and the main welding section, the main welding section is the section obtained by excluding the start processing section and the end processing section from the welding section, A method for evaluating welding quality, characterized in that the evaluation indexes are different for the start processing section, the end processing section, and the main welding section.

5. The method for evaluating weld quality according to claim 4, the parameter in the start processing section is the first period, the parameter in the end processing section is a second period from a predetermined time point when the feed speed of the welding wire is the predetermined value to a welding end time point when the feed speed of the welding wire becomes zero, A method for evaluating welding quality, characterized in that the parameter in the main welding section is a third period obtained by excluding the first period and the second period from the period from the start of welding to the end of welding.

6. The method for evaluating weld quality according to claim 4, the parameter in the start processing section is a first bead length, which is a length along a welding direction from a welding start point at the welding location as a base point toward a welding end point; the parameter in the end processing section is a second bead length, which is a length along the welding direction from the welding end point as a base point toward the welding start point, a third bead length obtained by subtracting the first bead length and the second bead length from the length of the welded portion along the welding direction;

7. The method for evaluating weld quality according to claim 4, A method for evaluating welding quality, characterized in that the weighting coefficients are different for each of the multiple sections.

8. A welding quality evaluation device for arc welding, comprising: an input unit to which at least physical quantities measured during welding of the base metal are input; a welding section dividing unit that divides a welding section at one welding point into a plurality of sections including at least a start processing section; an evaluation index setting unit that sets an evaluation index corresponding to welding quality at least in the start processing section; a parameter setting unit that sets parameters corresponding to at least the start processing section based at least on the physical quantity input to the input unit; an evaluation score calculation unit that determines a first evaluation score for the evaluation index based on the physical quantity input to the input unit and an evaluation algorithm for the evaluation index; a weighting coefficient setting unit that sets a weighting coefficient based on the parameter; a welding quality evaluation unit that evaluates the welding quality of the welded portion based on the second evaluation score, the evaluation score calculation unit weights the first evaluation score using the weighting coefficient to calculate the second evaluation score; The welding quality evaluation device is characterized in that the start processing section includes a first period from when a welding torch switch is turned on until the feed speed of the welding wire held by the welding torch reaches a predetermined value.

9. The welding quality evaluation device according to claim 8, the evaluation index setting unit sets the evaluation index for each of the plurality of sections; the parameter setting unit sets the parameters corresponding to each of the plurality of sections; the weighting coefficient setting unit sets the weighting coefficient for each of the plurality of sections based on the type of the parameter and the type of the section; the evaluation score calculation unit determines the first evaluation score for each of the plurality of sections based on the physical quantity and the evaluation algorithm; Furthermore, the first evaluation score is weighted using the weighting coefficient to calculate the second evaluation score, and the second evaluation scores for each of the plurality of sections are added together to calculate a comprehensive evaluation score; the welding quality evaluation unit evaluates the welding quality of the welded portion based on the overall evaluation score, The plurality of sections include at least two of the start processing section, the end processing section, and the main welding section, the main welding section is the section obtained by excluding the start processing section and the end processing section from the welding section, The welding quality evaluation device is characterized in that the evaluation index setting unit sets different evaluation indexes for the start processing section, the end processing section, and the main welding section.

10. The welding quality evaluation device according to claim 9, The welding quality evaluation device is characterized in that the weighting coefficient setting unit sets different weighting coefficients for each of the plurality of sections.

11. an arc welding device for welding the base material; A welding system comprising at least the welding quality evaluation device according to any one of claims 8 to 10.

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