Welding current waveform modification method, welding current waveform modification device, and program

Abstract

This welding current waveform modification method comprises at least a first step and a second step. In the first step, a basic waveform of a welding current Aw is prepared. In the second step, the basic waveform is modified to a welding current waveform having a different waveform pattern, in accordance with the plate thickness of a base material 200, which is an object to be welded, the penetration depth, or the penetration ratio.

Description

Welding current waveform correction method, welding current waveform correction device, and program

[0001] The present disclosure relates to a method for correcting a welding current waveform, and more particularly to a method for correcting a welding current waveform in DC arc welding, and a welding current waveform correction device and program.

[0002] Typically, a current command value for the welding current and the like are input to a welding power source to complete the setting of welding conditions, and then arc welding is performed (see, for example, Patent Document 1).

[0003] For example, a basic waveform stored in a memory unit provided in the welding power source is read out, and the current command value is adjusted according to the structure and thickness of the base material to be welded, before arc welding is performed.

[0004] Japanese Patent Application Laid-Open No. 60-064773

[0005] However, in actual DC arc welding, simply adjusting the current command value to change the welding conditions is sometimes insufficient. For example, when applying a basic waveform set for a medium-thickness base metal to a thin base metal, lowering the current command value reduces the heat input to the base metal. However, depending on the shape of the basic waveform, the heat input to the base metal may become too large, resulting in poor welding, such as burn-through.

[0006] The present disclosure has been made in consideration of these points, and its purpose is to provide a welding current waveform correction method, welding current waveform correction device, and program that can appropriately correct the welding current waveform in accordance with the plate thickness and penetration depth of the base material and the frequency of the welding current during welding.

[0007] In order to achieve the above object, the method of correcting a welding current waveform according to the present disclosure is a method of correcting a welding current waveform in DC arc welding, wherein a welding machine for performing the DC arc welding has at least a welding output unit, a welding torch, and a control unit, and the control unit has at least a calculation unit and a memory unit, and the method comprises at least a first step of preparing a basic waveform of a welding current, and a second step of correcting the basic waveform to a welding current waveform having a different waveform pattern in accordance with a plate thickness or penetration depth of a base metal that is a workpiece to be welded or a frequency of the welding current during welding, and the basic waveform is a waveform having a different waveform pattern in accordance with a plate thickness or penetration depth of a base metal that is a workpiece to be welded or a frequency of the welding current during welding, The welding current waveform is a waveform in which the current value of the welding current is plotted against the discrete time at a predetermined time interval when the plate thickness is the actual plate thickness used for welding the base material and the penetration depth is the initial penetration depth, or when the penetration ratio is the initial penetration ratio, and the welding current waveform is a waveform in which the current value of the welding current is plotted against the discrete time at the time interval when the plate thickness is the actual plate thickness used for welding the base material and the penetration depth is the actual penetration depth, which is the desired penetration depth, or when the penetration ratio is the actual penetration ratio, which is the ratio of the actual penetration depth to the actual plate thickness.

[0008] The welding current waveform correction device according to the present disclosure is a welding current waveform correction device having at least the calculation unit, wherein the calculation unit executes the welding current waveform correction method.

[0009] The program according to the present disclosure causes one or more processors to execute the welding current waveform correction method.

[0010] According to the present disclosure, the welding current waveform can be appropriately corrected depending on the plate thickness and penetration depth of the base metal and the frequency of the welding current during welding.

[0011] FIG. 1 is a schematic diagram of an arc welding machine according to a first embodiment. FIG. 2 is a flowchart showing a procedure for correcting a welding current waveform. FIG. 3 is a schematic diagram showing a basic waveform of a welding current. FIG. 4 is an enlarged view of a portion surrounded by a dashed line in FIG. 3. FIG. 5 is a schematic diagram showing an example of waveform pattern A. FIG. 6 is a schematic diagram showing another example of waveform pattern A. FIG. 7 is a schematic diagram showing an example of waveform pattern B. FIG. 8 is a flowchart showing a procedure for correcting a welding current waveform according to a second embodiment. FIG. 9 is a conceptual diagram for explaining a procedure for halving the period of a basic waveform. FIG. 10 is a conceptual diagram for explaining a procedure for doubling the period of a basic waveform. FIG. 11 is a flowchart showing a procedure for correcting a welding current waveform according to a third embodiment. FIG. 12 is a flowchart showing a procedure for correcting a welding current waveform according to a modified example.

[0012] 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.

[0013] First Embodiment [Configuration of Arc Welding Machine] FIG. 1 shows a schematic configuration diagram of an arc welding machine according to a first embodiment. An arc welding machine 100 includes a welding power source 40 and a welding torch 60.

[0014] The welding power source 40 converts AC power supplied from the three-phase AC power source PS into DC power suitable for arc welding and outputs it to the electrode 70 held by the welding torch 60. In this embodiment, a welding current Aw is supplied from the welding power source 40 to the electrode 70. An arc ARC is generated between the tip of the electrode 70 to which the welding current Aw is supplied and the base material 200, thereby welding the base material 200. In other words, DC TIG welding is performed by the arc welder 100. The output of the welding power source 40 can be changed depending on the type of arc welding. For example, the output of the welding power source 40 may be a welding voltage Vw applied between the base material 200 and the electrode 70.

[0015] The welding power source 40 has at least a welding output unit 10, a welding output detection unit 20, a control unit 30, and an input unit 32, and the welding output unit 10 has a first rectification unit 11, a first switching unit 12, a transformer 13, a second rectification unit 14, a reactor (DCL) 15, and a second switching unit 16.

[0016] The first rectifier 11 is composed of rectifying elements such as diodes and rectifies AC power received from the three-phase AC power source PS. The first switching unit 12 is, for example, an inverter circuit composed of multiple transistors. The first switching unit 12 switches the multiple transistors at timings according to control commands from the control unit 30 to control the output of the first rectifier 11 to an output suitable for welding. The transformer 13 is, for example, a transformer having an iron core and converts the output of the first switching unit 12 to an output suitable for welding. The second rectifier 14 has a configuration similar to that of the first rectifier 11 and rectifies the output of the transformer 13. The reactor 15 is connected in series with the second rectifier 14 and smooths the output of the second rectifier 14. The second switching unit 16 has a configuration similar to that of the first switching unit 12. In other words, the second switching unit 16 is an inverter circuit composed of multiple transistors and switches the multiple transistors at timings according to control commands from the control unit 30 to adjust the output of the reactor 15.

[0017] In this embodiment, the output of second switching unit 16 is the aforementioned welding current Aw, which is supplied to electrode 70 held by welding torch 60 via power cable 51. When the output of second switching unit 16 is welding voltage Vw, a predetermined voltage is applied between electrode 70 and base material 200 via power cables 51 and 52, respectively.

[0018] Welding output detection unit 20 has a welding current detection unit 21 and a welding voltage detection unit 22. Welding current detection unit 21 detects the welding current Aw supplied to electrode 70, and welding voltage detection unit 22 detects the welding voltage Vw applied between electrode 70 and base material 200. The results detected by welding current detection unit 21 and welding voltage detection unit 22 are sent to control unit 30 and used to control the arc welding.

[0019] The control unit 30 is configured with one or more central processing units (CPUs). Alternatively, the control unit 30 is configured with one or more micro control units (MCUs). The control unit 30 also has a calculation unit 30A configured with one or more CPUs. The calculation unit 30A calculates the actual thickness D of the base material 200, which will be described later. １ and actual penetration depth dw １ Alternatively, when actual penetration ratio R1 is input, calculation unit 30A determines whether or not to execute a welding current waveform correction process based on the input values, and executes the welding current waveform correction process as necessary. In other words, calculation unit 30A can be said to be a correction device that executes the welding current waveform correction process. Note that memory unit 31 may be incorporated into the correction device.

[0020] In the example shown in FIG. 1 , a memory unit 31 is provided independent of the control unit 30. The memory unit 31 is configured with semiconductor memory such as a random access memory (RAM) or a read-only memory (ROM). The memory unit 31 may also be configured with a hard disk drive (HDD) or a solid state drive (SSD). The memory unit 31 may be a functional block of a CPU or an MCU, i.e., a ROM or RAM built into the CPU or MCU. The memory unit 31 stores control programs and welding parameters for various devices used in arc welding. The memory unit 31 also stores a program describing a welding current waveform correction procedure, which will be described later.

[0021] The control unit 30 controls the switching operations of the first switching unit 12 and the second switching unit 16 in accordance with a predetermined welding program. For example, the control unit 30 controls the switching operation of the second switching unit 16 based on a preset current command value and the pulse period of the welding current Aw. The control unit 30 also receives the detection result of the welding current detection unit 21 and controls the switching operations of the first switching unit 12 and the second switching unit 16 based on the detection result so that the welding current Aw becomes the preset current command value. The current command value refers to the moving average value of the welding current Aw during a preset welding period Tw.

[0022] The input unit 32 is composed of, for example, a display device such as a liquid crystal display and an input device such as a keyboard, input buttons, a rotary encoder with a switch, etc. If the display device is a touch panel, the input device may be omitted.

[0023] The input unit 32 inputs welding conditions during arc welding, for example, the actual thickness D of the base material 200. １ and actual penetration depth dw １ It is used to input the following:

[0024] Welding torch 60 may be held by a robot (not shown). In this case, the robot moves welding torch 60 at a predetermined speed (welding speed) along a predetermined weld line (not shown) so that the distance between the tip of electrode 70 and the surface of base material 200 is within a predetermined range.

[0025] 1, input unit 32 is provided in welding power source 40, but input unit 32 may be provided outside welding power source 40 as long as it is capable of communicating with control unit 30. For example, a teaching pendant (TP) 33 for teaching the robot the movement trajectory of welding torch 60 may be input unit 32. In this case, communication between teaching pendant 33, which is input unit 32, and control unit 30 may be wired or wireless.

[0026] Although not shown, a filler metal may be used when performing arc welding. The filler metal is made of the same metal as the base metal 200, and is melted in the arc ARC to be used as a metal supply source for maintaining the strength and appearance of the welded portion. Note that the filler metal is not essential, and can be omitted depending on the conditions required for the welded portion and the shape of the base metal 200.

[0027] [Procedure for correcting welding current waveform] Normally, when performing DC TIG welding using the arc welding machine 100, the basic waveform of the welding current Aw (hereinafter simply referred to as the basic waveform) stored in the memory unit 31 is read into the control unit 30, and the current command value is changed to a value suitable for welding the base material 200.

[0028] However, as already mentioned, if the basic waveform is maintained and only the current command value is changed, for example, if the base material 200 is a thin plate, there is a risk of burn-through occurring depending on the shape of the waveform.

[0029] Therefore, in this embodiment, a method is proposed in which the time waveform of the welding current (hereinafter referred to as the welding current waveform) is obtained by modifying the basic waveform in accordance with the plate thickness or penetration depth of the base material 200 or the penetration ratio, which will be described later. This will be further explained below with reference to the drawings.

[0030] Fig. 2 is a flowchart showing the procedure for correcting the welding current waveform, Fig. 3 is a schematic diagram showing the basic waveform of the welding current, and Fig. 4 is an enlarged view of the portion surrounded by the dashed line in Fig. 3.

[0031] As shown in Fig. 2, a basic waveform is prepared (step S1). The basic waveform is stored in the storage unit 31 as described above, and is read out by the control unit 30. Note that the basic waveform in this embodiment is a pulse current waveform as shown in Fig. 3. More specifically, the basic waveform is a waveform in which the current value is I ｐ０ The peak current period Tp and the current value I ｂ The period T of the basic waveform is the sum of the peak current period Tp and the base current period Tb. In other words, the relationship shown in equation (1) holds.

[0032] T = Tp + Tb (1) Also, the pulse frequency f of the welding current Aw ０ (Hereinafter, the initial frequency f ０ ) is the reciprocal of the period T. In other words, the relationship shown in equation (2) holds.

[0033] f ０ = 1 / T (2) At the start of the peak current period Tp, there is a finite rise time T ｒ０ (Hereinafter, the initial rise time T ｒ０ The welding current Aw is sometimes called I ｂ From I ｐ０ At the end of the peak current period Tp, the voltage rises to a finite fall time T ｆ０ (Hereinafter, the initial fall time T ｆ０) and the current value of the welding current Aw is I ｐ０ From I ｂ Stand up.

[0034] As shown in FIG. 4, the welding current Aw is ＩＮＶ This is a waveform in which the current value is plotted against discrete time t. Here, the time interval T ＩＮＶ is the control period of the second switching unit 16 by the control unit 30.

[0035] Furthermore, the basic waveform in this embodiment is such that the current command value of the welding current Aw is a preset initial command value I ｓ０ The thickness of the base material 200 is a preset initial thickness D ０ If the time interval T ＩＮＶ 1 is a waveform obtained by plotting the current value of the welding current Aw against discrete time t.

[0036] The actual thickness D, which is the thickness of the base material 200 to be welded, is input from the input unit 32. １ and actual penetration depth dw １ Or actual penetration ratio R １ (Step S2). Here, the actual penetration depth dw １ is the penetration depth required when welding the base material 200, in other words, the desired penetration depth. １ (=dw １ / D １ ) is the actual thickness D of the base material 200 １ Actual penetration depth dw １ In this specification, the penetration depth when the welding current Aw has a basic waveform is referred to as the initial penetration depth dw ０ Also, the initial plate thickness D ０ Initial penetration depth dw ０ The ratio of the initial penetration ratio R ０ (=dw ０ / D ０ ) is called the initial command value I ｓ０ , initial penetration depth dw ０ , initial penetration ratio R ０ and initial plate thickness D ０ The value of is stored in advance in the storage unit 31.

[0037] Next, the calculation unit 30A calculates the actual plate thickness D １ is the initial plate thickness D ０ (Step S3). If the determination result of Step S3 is affirmative, that is, the actual plate thickness D １ is the initial plate thickness D ０ If the value is the same as the actual penetration depth dw １ and initial penetration depth dw ０ are the same as the actual penetration ratio R １ and initial penetration ratio R ０ On the other hand, if the result of the determination in step S3 is negative, that is, the actual plate thickness D １ is the initial plate thickness D ０ If the value is different from the value, the process proceeds to step S5.

[0038] If the judgment result in step S4 is affirmative, in other words, the actual penetration depth dw １ and initial penetration depth dw ０ and the actual penetration ratio R １ and initial penetration ratio R ０ If the values ​​are the same, it is determined that there is no need to modify the fundamental waveform, and the process ends.

[0039] In step S5, the calculation unit 30A calculates the actual plate thickness D １ is the initial plate thickness D ０ If the determination result in step S5 is affirmative, that is, if the thickness is greater than the actual thickness D １ is the initial plate thickness D ０ If the thickness is greater than 100 μm, the calculation unit 30A changes the basic waveform to waveform pattern A (step S6).

[0040] Fig. 5 is a schematic diagram showing an example of waveform pattern A. Fig. 6 is a schematic diagram showing another example of waveform pattern A.

[0041] When the welding current waveform is changed to waveform pattern A, for example, as shown in FIG. 5, the welding current waveform changes to the peak current value I of the basic waveform at the start of period T. ｐ０ A first peak current value I ｐ１The waveform pattern is changed to waveform pattern A, which rises at the first peak current value I and then falls stepwise until the period T has elapsed. ｐ１ The peak current value of the basic waveform I ｐ０ By making it higher than the actual thickness D １ is the initial plate thickness D ０ Even if the thickness is greater than 100 mm, an appropriate penetration depth can be obtained, and the occurrence of welding defects and the like can be suppressed.

[0042] 5 is merely an example, and is not particularly limited to this. For example, in the example shown in FIG. 5, the peak current period Tp is divided into three periods, and the first peak current value I ｐ１ During the next periods T2 and T3, the welding current Aw is increased to a second peak current value I ｐ２ , and the third peak current value I ｐ３ Then, during the base current period Tb, the welding current Aw is reduced stepwise to I ｂ However, the number of divisions into which the peak current period Tp is divided and the current value of the welding current Aw in periods other than the first divided period can be changed as appropriate.

[0043] 6, for example, the peak current period Tp is divided into two periods, and the first peak current value I ｐ１ The welding current Aw is increased to and maintained at this value, and in the next period T5, the welding current Aw is continuously decreased until the current value of the welding current Aw reaches I ｂ The length of the period T4 may be changed as appropriate. The decrease curve of the welding current Aw during the period T5 is not limited to a straight line.

[0044] The calculation unit 30A calculates the actual plate thickness D １ In response to the first peak current value I ｐ１ (Step S7). ｐ１ is the actual plate thickness D １ The function is stored in the storage unit 31. ｐ１ is the actual penetration depth dw １ and actual penetration ratio R １The function is stored in the storage unit 31. That is, the first peak current value I ｐ１ is the actual plate thickness D １ , actual penetration depth dw １ and actual penetration ratio R １ increases as either of these increases.

[0045] Note that this function is not unique and takes a different form depending on, for example, the material of the base material 200. Therefore, the memory unit 31 stores the first peak current value I ｐ１ and the actual thickness D １ , actual penetration depth dw １ and actual penetration ratio R １ The calculation unit 30A calls up the function as needed and uses it when executing step S6. Note that instead of the function, the calculation unit 30A may store a table of the first peak current value I ｐ１ and the actual thickness D １ , actual penetration depth dw １ and actual penetration ratio R １ The relationship may be described.

[0046] After step S6 is executed, the welding current waveform correction process ends.

[0047] If the determination result in step S5 is negative, that is, the actual plate thickness D １ is the initial plate thickness D ０ If the thickness is thinner than the reference value, the calculation unit 30A changes the basic waveform to waveform pattern B (step S8). The original forms of waveform patterns A and B are stored in advance in the storage unit 31. As will be described later, the shapes of waveform patterns A and B can be changed in step S2 according to values ​​input from the input unit 32.

[0048] 7 is a schematic diagram showing an example of waveform pattern B. When the welding current waveform is changed to waveform pattern B, the rising period and falling period in the peak current period Tp are changed from the basic waveform. For example, as shown in FIG. 7, ｒ１ is the initial rise period T ｒ０The welding current waveform is corrected so that the falling period T in the peak current period Tp is longer than ｆ１ is the initial falling period T ｆ０ The welding current waveform is modified so that the welding current is longer than the

[0049] The calculation unit 30A calculates the actual plate thickness D １ Depending on the rise period T ｒ１ and the falling period T ｆ１ (step S9).

[0050] Start-up period T ｒ１ and the falling period T ｆ１ The values ​​of each are the actual plate thickness D １ The function is stored in the storage unit 31. ｒ１ and the falling period T ｆ１ The actual penetration depth dw １ and actual penetration ratio R １ The function is stored in the storage unit 31. ｒ１ and the falling period T ｆ１ The values ​​of each are the actual plate thickness D １ , actual penetration depth dw １ and actual penetration ratio R １ increases as either of these increases.

[0051] Note that this function is not unique and takes a different form depending on, for example, the material of the base material 200. Therefore, the memory unit 31 stores the rising period T ｒ１ and the falling period T ｆ１ The respective values ​​and the actual plate thickness D １ , actual penetration depth dw １ and actual penetration ratio R １ The calculation unit 30A calls the function as appropriate and uses it when executing step S6. ｒ１ and the falling period T ｆ１ The respective values ​​and the actual plate thickness D １, actual penetration depth dw １ and actual penetration ratio R １ The relationship may be described.

[0052] In the example shown in FIG. ｒ１ and the falling period T ｆ１ are included in the peak current period Tp, but are not limited to this. For example, a rising period T ｒ１ Alternatively, a falling period T may be provided across the peak current period Tp and the base current period Tb. ｆ１ may be provided.

[0053] After step S9 is executed, the welding current waveform correction process ends.

[0054] If the determination result in step S4 is negative, that is, the actual penetration depth dw １ is the initial penetration depth dw ０ or the actual penetration ratio R １ is the initial penetration ratio R ０ If the value is different from the value, the process proceeds to step S10.

[0055] In step S10, the calculation unit 30A calculates the actual penetration depth dw １ is the initial penetration depth dw ０ or actual penetration ratio R １ is the initial penetration ratio R ０ If the determination result in step S10 is affirmative, that is, the actual penetration depth dw １ is the initial penetration depth dw ０ or the actual penetration ratio R １ is the initial penetration ratio R ０ If the difference is higher than , the calculation unit 30A changes the basic waveform to waveform pattern A (step S11). The process of step S11 is the same as the process of step S7. As waveform pattern A, for example, the waveform patterns shown in Figs. 5 and 6 are selected.

[0056] Next, the calculation unit 30A calculates the actual penetration depth dw １ Or actual penetration ratio R １In response to the first peak current value I ｐ１ (Step S12) After step S12 is executed, the welding current waveform correction process is terminated.

[0057] If the determination result in step S10 is negative, that is, the actual penetration depth dw １ is the initial penetration depth dw ０ shallower than the actual penetration ratio R １ is the initial penetration ratio R ０ , the calculation unit 30A changes the basic waveform to waveform pattern B (step S13). In step S13, the same process as in step S9 is executed. That is, as shown in FIG. 7, ｒ１ is the initial rise period T ｒ０ The welding current waveform is corrected so that the falling period T in the peak current period Tp is longer than ｆ１ is the initial falling period T ｆ０ The welding current waveform is modified so that the welding current is longer than the

[0058] In addition, the calculation unit 30A calculates the actual penetration depth dw １ Or actual penetration ratio R １ Depending on the rise period T ｒ１ and the falling period T ｆ１ (Step S14) After step S14 is executed, the welding current waveform correction process is terminated.

[0059] The welding current waveform acquired in steps S7 and S12 is the thickness of the base material 200 when the actual thickness D １ In the case of the aforementioned time interval T ＩＮＶ The welding current waveform obtained in steps S7 and S12 is at least temporarily stored in the memory unit 31, and the current command value is set to the initial command value I ｓ０ The thickness of the base material 200 is the actual thickness D １ This is used as the basic waveform when welding.

[0060] The welding current waveform acquired in steps S9 and S14 is the actual penetration depth dw １Or the penetration ratio during welding is the actual penetration ratio R １ If ＩＮＶ The welding current waveform obtained in steps S9 and S14 is at least temporarily stored in the memory unit 31, and the current command value is set to the initial command value I ｓ０ The penetration depth during welding is the actual penetration depth dw １ Or, the penetration ratio during welding is set to the actual penetration ratio R １ This is used as the basic waveform when welding.

[0061] [Effects, etc.] As described above, the method for correcting a welding current waveform in DC arc welding according to this embodiment uses arc welder 100 having at least welding output unit 10, welding torch 60, and control unit 30 to perform the first and second steps described below. Control unit 30 has at least calculation unit 30A and memory unit 31.

[0062] In the first step, a basic waveform of the welding current Aw is prepared (step S1 in FIG. 2).

[0063] In the second step, the basic waveform is modified to a welding current waveform having a different waveform pattern depending on the plate thickness, penetration depth, or penetration ratio of the base material 200 to be welded (steps S6 to S9, S11 to S14 in FIG. 2). The basic waveform is modified to a different waveform pattern depending on the plate thickness, penetration depth, or penetration ratio of the base material 200 to be welded (steps S6 to S9, S11 to S14 in FIG. 2). ０ And the penetration depth during welding is the initial penetration depth dw ０ Is the penetration ratio equal to the initial penetration ratio R ０ If the predetermined time interval T ＩＮＶ The waveform is a plot of the current value of the welding current Aw against discrete time t. The current command value of the welding current Aw represented by the basic waveform is the initial command value I ｓ０ is.

[0064] The welding current waveform is such that the thickness of the base material 200 is the actual thickness D １ The penetration depth during welding is the actual penetration depth dw １ Whether the penetration ratio is the actual penetration ratio R １ If the predetermined time interval TＩＮＶ The waveform is a plot of the current value of the welding current Aw against the discrete time t. In this case, the current command value of the welding current Aw is also the initial command value I ｓ０ is.

[0065] As described above, the preset initial plate thickness D ０ Using the basic waveform corresponding to the initial plate thickness D ０ The actual thickness D is significantly thinner than １ When welding the base material 200, depending on the shape of the basic waveform, burn-through of the base material 200 may occur.

[0066] On the other hand, according to the present embodiment, the basic waveform is modified to a welding current waveform having a different waveform pattern depending on the plate thickness, penetration depth, or penetration ratio of the base material 200. In this way, the waveform of the welding current Aw used in actual welding can be easily and appropriately obtained. Furthermore, when inputting welding conditions, the current command value is set to the initial command value I ｓ０ The input conditions, for example, the actual thickness D １ This allows the welding current waveform to be appropriately changed.

[0067] The basic waveform in this embodiment is a pulse current waveform that varies with time at a predetermined period T. １ is the initial plate thickness D ０ Thicker than the actual penetration depth dw １ is the initial penetration depth dw ０ or the actual penetration ratio R １ is the initial penetration ratio R ０ If the peak current value I of the basic waveform is higher than the peak current value I of the basic waveform, the basic waveform is modified to waveform pattern A. ｐ０ A first peak current value I ｐ１ The welding current waveform rises at a period T and then decreases stepwise or continuously until the period T has elapsed. The period T of waveform pattern A is equal to the period T of the basic waveform.

[0068] For example, the first peak current value I ｐ１may be written as the relational expressions shown in equations (3) to (8), and the relational expressions may be stored in the storage unit 31 and used when steps S7 and S12 are executed.

[0069] I ｐ１ = a × (D １ / D ０ ) ... (3) I ｐ１ = b × (D １ -D ０ ) ... (4) I ｐ１ = c × (dw １ / dw ０ ) ... (5) I ｐ１ = d × (dw １ -dw ０ ) ... (6) I ｐ１ = e × (R １ / R ０ ) ... (7) I ｐ１ = f × (R １ -R ０ ) (8) where a to f are positive constants. The first peak current value I ｐ１ The relational expressions describing the above are not particularly limited to the expressions (3) to (8).

[0070] By doing so, the concentration of the arc ARC can be strengthened at the beginning of the cycle T, thereby obtaining a deep penetration. After that, by gradually or continuously decreasing the welding current Aw, excessive heat input to the base material 200 can be suppressed, and the actual penetration depth dw, which is the desired penetration depth, can be obtained. １ If the thickness of the base material 200 is the same and it is desired to change the penetration depth, it is preferable to modify the welding current waveform using the penetration ratio as a parameter.

[0071] In addition, the actual thickness D １ becomes thicker or the actual penetration depth dw １ becomes deeper, or the actual penetration ratio R １ As the first peak current value I ｐ１ In this way, it is possible to prevent insufficient penetration of the base material 200 during welding, and to obtain a desired penetration depth.

[0072] In addition, the actual thickness D １is the initial plate thickness D ０ or the actual penetration depth dw １ is the initial penetration depth dw ０ Or the actual penetration ratio R １ is the initial penetration ratio R ０ If the basic waveform is lower than the rising period T ｒ１ and the falling period T ｆ１ is the rising period T of the fundamental waveform ｒ０ and the falling period T ｆ０ are longer than

[0073] In other words, the rising period T of the welding current Aw in the welding current waveform ｒ１ is the rising period T of the welding current Aw in the basic waveform. ｒ０ Furthermore, the basic waveform is modified so that the falling period T of the welding current Aw in the welding current waveform is longer than ｆ１ is the falling period T of the welding current Aw in the basic waveform. ｆ０ The fundamental waveform is modified so that it is longer than the period T of the waveform pattern B. The period T of the waveform pattern B is equal to the period T of the fundamental waveform.

[0074] For example, the rising period T ｒ１ and the falling period T ｆ１ may be written as the relational expressions shown in equations (9) to (20), and the relational expressions may be stored in the storage unit 31 and used when steps S9 and S14 are executed.

[0075] T ｒ１ = g × (D １ / D ０ ) ... (9) T ｒ１ = h × (D １ -D ０ ) ...(10) T ｒ１ = i × (dw １ / dw ０ ) ...(11) T ｒ１ = j × (dw １ -dw ０ ) ...(12) T ｒ１ = k × (R １ / R ０ ) ...(13) Tｒ１ = l × (R １ -R ０ ) ...(14) T ｆ１ = m × (D １ / D ０ ) ...(15) T ｆ１ = n × (D １ -D ０ ) ...(16) T ｆ１ = o × (dw １ / dw ０ ) ...(17) T ｆ１ = p × (dw １ -dw ０ ) ...(18) T ｆ１ = q × (R １ / R ０ ) ...(19) T ｆ１ = r × (R １ -R ０ ) (20) where g to r are positive constants. ｒ１ and the falling period T ｆ１ The relational expressions describing the above are not particularly limited to the expressions (9) to (20).

[0076] This weakens the concentration of the arc ARC at the beginning and end of the cycle T, thereby preventing burn-through of the base material 200. If the thickness of the base material 200 is the same but the penetration depth is to be changed, it is preferable to modify the welding current waveform using the penetration ratio as a parameter.

[0077] Actual plate thickness D １ becomes thinner or the actual penetration depth dw １ becomes shallower, or the actual penetration ratio R １ As the value of T decreases, the rise time T ｒ１ and the falling period T ｆ１ In other words, it is preferable that the actual plate thickness D １ becomes thinner or the actual penetration depth dw １ becomes shallower, or the actual penetration ratio R １ As the value of T decreases, the rise time T ｒ１It is preferable that the time gradient of the welding current Aw is set small during the falling period T ｆ１ It is preferable to set the welding current Aw so that the absolute value of the time gradient in the welding current Aw is small. By doing so, it is possible to reliably prevent burn-through of the base material 200 from occurring.

[0078] The welding output unit 10 in the arc welding machine 100 has a second switching unit 16 which is an inverter that controls the time variation of the welding current Aw. ＩＮＶ is the control period of the inverter. ＩＮＶ In other words, the control frequency of the inverter is a fixed value.

[0079] Time interval T ＩＮＶ By setting in this way, the period change process of the basic waveform, which will be described later, can be easily performed. Note that the frequency of the basic waveform, that is, the initial frequency f ０ If the frequency is 10 Hz, the period T is 100 msec. ＩＮＶ If the time is 12.5 μsec, the fundamental waveform will be data consisting of 8000 points.

[0080] It is preferable to further include a third step of at least temporarily storing the welding current waveform obtained in the second step in the memory unit 31. By doing so, when welding the same type of base material 200 again after a period of time, the corrected welding current waveform can be used as is, simplifying the work of setting welding conditions. Note that if multiple waveform patterns of the welding current waveform are stored in the memory unit 31, there is no need to store the corrected welding current waveform in the memory unit 31 for a long period of time. This is because the desired welding current waveform can be obtained by changing the basic waveform to an appropriate waveform pattern according to the purpose and then further modifying the waveform pattern.

[0081] The program according to this embodiment causes one or more CPUs (processors) to execute the welding current waveform correction method described above. From another perspective, the welding current waveform correction device according to this embodiment has at least a calculation unit 30A, and calculation unit 30A executes the welding current waveform correction process according to this embodiment.

[0082] In this way, the calculation unit 30A, which is composed of a CPU, executes the welding current waveform correction process, and by programming the welding current waveform correction procedure, the basic waveform can be easily corrected to obtain the desired welding current waveform.

[0083] In the waveform pattern A, the first peak current value I ｐ１ The waveform during the period T5 shown in FIG. 6 may be an upwardly convex curve or a downwardly convex curve. In addition, in the waveform pattern B, the waveform during the rising period T ｒ１ and the falling period T ｆ１ Each waveform in may be, for example, an upwardly convex curve or a downwardly convex curve.

[0084] In step S3 of the flowchart shown in FIG. 2, the actual plate thickness D １ is the initial plate thickness D ０ However, the actual thickness D １ and initial plate thickness D ０ If the difference is small, the actual thickness D １ is the initial plate thickness D ０ and proceed to step S4.

[0085] In view of this, in step S3, the actual plate thickness D １ and initial plate thickness D ０ In step S5, it is determined whether the difference is equal to or less than the first range, and the actual plate thickness D １ is the initial plate thickness D ０ It may be determined whether the thickness exceeds a first range or not. Here, the first range is the thickness D １ is the initial plate thickness D ０ This range can be considered equivalent to the actual thickness D １ is the initial plate thickness D ０The negative result of the determination in step S5 means that the actual plate thickness D １ is the initial plate thickness D ０ That is, the thickness is thinner than the first range by more than the first range.

[0086] For the same reason, in step S4, the actual penetration depth dw １ and initial penetration depth dw ０ Whether the difference between the actual penetration ratio R １ and initial penetration ratio R ０ In this case, in step S10, it may be determined whether the difference between the actual penetration depth dw and the actual penetration depth dw is equal to or less than a third range. １ exceeds the second range and the initial penetration depth dw ０ or whether it is deeper than the actual penetration ratio R １ exceeds the third range and the initial penetration ratio R ０ Here, the second range is the actual penetration depth dw １ is the initial penetration depth dw ０ The third range can be considered to be equivalent to the actual penetration ratio R １ is the initial penetration ratio R ０ This range can be considered equivalent to the above, and can be changed as appropriate depending on the welding conditions, the thickness of the base material 200, etc.

[0087] In this case, if the determination result in step S10 is affirmative, the actual penetration depth dw １ exceeds the second range and the initial penetration depth dw ０ or the actual penetration ratio R １ exceeds the third range and the initial penetration ratio R ０ If the determination result in step S10 is negative, the actual penetration depth dw １ exceeds the second range and the initial penetration depth dw ０ or the actual penetration ratio R １ exceeds the third range and the initial penetration ratio R ０ This means that it is lower than

[0088] (Embodiment 2) Fig. 8 is a flowchart showing the procedure for correcting a welding current waveform according to embodiment 2. Fig. 9 is a conceptual diagram for explaining the procedure for halving the period of the basic waveform. Fig. 10 is a conceptual diagram for explaining the procedure for doubling the period of the basic waveform. Note that in Figs. 8 to 10, for the sake of convenience, parts that are the same as those in embodiment 1 are given the same reference numerals, and detailed explanations thereof will be omitted.

[0089] In the flowchart shown in Fig. 8, steps S20 and S22 to S34 are the same as steps S1 to S14 in the flowchart shown in Fig. 2, and therefore description thereof will be omitted. The flowchart shown in Fig. 8 differs from the flowchart shown in Fig. 2 in that a fundamental waveform period change process shown in step S21 is added.

[0090] Step S21 (fourth step) is executed between step S20 (first step) and step S22. Specifically, in step S21, the basic waveform is corrected in accordance with the cycle (hereinafter referred to as the actual use cycle) of the welding current Aw used to weld the base material 200. This will be further explained.

[0091] In the basic waveform, a fundamental period T (hereinafter simply referred to as period T) is predetermined. As described above, period T is a time interval T ＩＮＶ is an integer multiple of

[0092] T = n × T ＩＮＶ ...(21) where n is an integer, and the period T is the time interval T ＩＮＶ This is the value divided by .

[0093] Therefore, the period T is the time interval T ＩＮＶ By utilizing the fact that the period T is n times the period T, it is possible to easily change the period T. In step S21, the period of the fundamental waveform is changed in the following procedure.

[0094] When the actual use period is half the period T of the fundamental waveform, data is thinned out from the fundamental waveform as shown in FIG. ＩＮＶ After extracting the current value of the welding current Aw at every double of time, the extracted multiple current values ​​are arranged on the time axis at time intervals T ＩＮＶ By placing it every time, the basic waveform is modified.

[0095] When the actual use period is twice the period T of the fundamental waveform, as shown in FIG. 10, the first time point and the time interval T ＩＮＶ After interpolating the current value of one welding current Aw between the first time point and the second time point after the time interval T, the interpolated current values ​​are arranged on the time axis at time intervals T ＩＮＶ By placing it every time, the basic waveform is modified.

[0096] In DC TIG welding, it may be desirable to change the period of the welding current waveform, in other words, the frequency. Increasing the frequency improves the directionality and concentration of the arc ARC, enabling the formation of a weld bead with a narrow width and deep penetration. Therefore, it is preferable to change the frequency of the welding current waveform, taking into consideration the material of the base metal 200 and the aesthetic appearance of the weld bead.

[0097] According to this embodiment, the period T of the basic waveform, and therefore the frequency of the corrected welding current waveform, can be easily changed by simple data processing.

[0098] In the welding current waveform correction method according to this embodiment, the fourth step can be expanded as follows.

[0099] If the actual use period is 1 / m times the period T of the fundamental waveform (m is an integer of 2 or more), the time interval T ＩＮＶ The current value of the welding current Aw extracted every m times is plotted on the time axis at time intervals T ＩＮＶ By placing it every time, the basic waveform is modified.

[0100] When the actual use period is m times the period T of the fundamental waveform, the first time point and the time interval T from the first time point are ＩＮＶ (m-1) current values ​​of the welding current Aw are interpolated between the second point in time after the time interval T ＩＮＶ By placing it every time, the basic waveform is modified.

[0101] It should be noted that the period T can be set to any value by combining a process of changing the period T by (1 / i) times (i is an integer of 2 or more) with a process of changing the period (T / i) by j times (j is an integer of 2 or more). For example, if T=100 msec and i=100, the changed period will be 1 msec. If the period is then multiplied by j (=33), the changed period will be 33 msec. When the period T is 100 msec, the frequency of the fundamental waveform (initial frequency f ０ ) is 10 Hz, and the frequency of the fundamental waveform after the two-stage change process (initial frequency f ０ ) is approximately 30 Hz.

[0102] Furthermore, the program according to this embodiment causes one or more CPUs (processors) to execute the welding current waveform correction method, including step 4. From another perspective, the welding current waveform correction device according to this embodiment has at least calculation unit 30A, and calculation unit 30A executes the welding current waveform correction process according to this embodiment.

[0103] In this way, the calculation unit 30A, which is composed of a CPU, executes the welding current waveform correction process, and by programming the welding current waveform correction procedure, the period T of the basic waveform can be easily changed and the basic waveform can be corrected to obtain the desired welding current waveform.

[0104] Third Embodiment FIG. 11 is a flowchart showing a procedure for correcting a welding current waveform according to a third embodiment.

[0105] For example, as shown in the second embodiment, the initial frequency f ０ In some cases, the basic waveform may be modified as necessary after changing the frequency. In this case, if the changed frequency is within a specified range, it may cause problems during welding work.

[0106] Increasing the frequency of the welding current Aw improves the directionality and concentration of the arc ARC, allowing for deeper penetration compared to when the frequency is low, even with the same current value. It also allows for narrower weld bead widths. Meanwhile, the width of the arc ARC periodically fluctuates depending on the frequency of the welding current Aw. Changes in the surrounding pressure at this time can sometimes cause noise, known as arc noise.

[0107] Arc noise occurs when the frequency of the welding current Aw is in the range of 20 Hz to 20 kHz, in other words, in the audible range. In particular, when the frequency of the welding current Aw is in the range of 2 kHz to 5 kHz, this is a range to which the human ear is highly sensitive, so the impact of the arc noise becomes significant. For example, when the arc noise level exceeds 100 dB, the permissible exposure time per day is limited to 15 minutes according to the noise tolerance standards established for hearing protection. This limits the amount of time that welding work can be done.

[0108] On the other hand, as mentioned above, there are cases where it is desirable to set the frequency of the welding current Aw to 2 kHz or higher in order to increase the directivity and concentration of the arc ARC.

[0109] Therefore, in this embodiment, the first frequency f １ A method for correcting the basic waveform in accordance with the above will be described with reference to FIG.

[0110] Step S41 (first step) shown in FIG. 11 is the same process as step S2 shown in FIG. 2, and therefore a description thereof will be omitted.

[0111] Next, the first frequency f １ (Step S42). The calculation unit 30A inputs the first frequency f １ It is determined whether the frequency is higher than a predetermined frequency (step S43). Here, the predetermined frequency is, for example, 1.5 kHz. However, the predetermined frequency is not particularly limited to this and can be changed as appropriate depending on the level of the arc sound generated during actual welding, the standard for the quality of the welded portion, etc.

[0112] If the determination result in step S43 is negative, that is, the first frequency f １ If the frequency is equal to or less than the predetermined frequency, the welding current waveform correction process is terminated.

[0113] On the other hand, if the determination result in step S43 is affirmative, that is, the first frequency f １ is higher than the predetermined frequency, the calculation unit 30A changes the basic waveform to waveform pattern B (step S44).

[0114] The calculation unit 30A also calculates the first frequency f１ Depending on the rise period T ｒ１ and the falling period T ｆ１ (step S45).

[0115] As described above, in the welding current waveform correction method according to this embodiment, the first step is to prepare a basic waveform of the welding current Aw (step S41 in FIG. 11).

[0116] In the second step, the first frequency f １ In response to this, the basic waveform is modified to a waveform pattern B, which is a different waveform pattern (step S44 in FIG. 11).

[0117] Specifically, the first frequency f １ is higher than a predetermined frequency, the rising period T ｒ１ is the rising period T of the basic waveform ｒ０ The falling period T ｆ１ is the falling period T of the basic waveform ｆ０ The basic waveform is corrected so that it is longer than (steps S43 to S45 in FIG. 11).

[0118] According to this embodiment, the first frequency f １ is higher than a predetermined frequency, the rising period T ｒ１ and the falling period T ｆ１ By increasing the length, it is possible to reduce the degree of change in the width of the arc ARC, thereby reducing the arc noise, for example. In addition, it is possible to weaken the concentration of the arc ARC and adjust the penetration depth.

[0119] The first frequency f １ and the initial frequency f ０ 8 may be executed before step S43. In this way, the frequency of the welding current waveform can be easily and reliably adjusted to the first frequency f １ can be changed to.

[0120] The program according to the present embodiment causes one or more CPUs (processors) to execute the welding current waveform correction method according to the present embodiment. From another perspective, the welding current waveform correction device according to the present embodiment has at least calculation unit 30A, and calculation unit 30A executes the welding current waveform correction process according to the present embodiment.

[0121] In this way, the calculation unit 30A, which is composed of a CPU, executes the welding current waveform correction process, and by programming the welding current waveform correction procedure, the basic waveform can be easily corrected to obtain the desired welding current waveform.

[0122] <Modification> FIG. 12 is a flowchart showing a procedure for correcting a welding current waveform according to a modification.

[0123] The flowchart of this modified example shown in FIG. 12 differs from the flowchart of the third embodiment shown in FIG. 11 in the following respects.

[0124] First, the first frequency f １ In addition to the first command value I ｓ１ (Step S52). ｓ１ is the current command value used in actual welding.

[0125] The calculation unit 30A calculates the first frequency f １ is higher than a predetermined frequency and the first command value I ｓ１ is the initial command value I ｓ０ It is determined whether or not it is greater than (step S53).

[0126] If the determination result in step S43 is negative, that is, the first frequency f １ is equal to or lower than a predetermined frequency, and the first command value I ｓ１ is the initial command value I ｓ０ If it is equal to or less than this, the welding current waveform correction process is terminated.

[0127] On the other hand, if the determination result in step S43 is affirmative, that is, the first frequency f １ is higher than a predetermined frequency, or the first command value I ｓ１ is the initial command value I ｓ０If it is greater than , the calculation unit 30A changes the basic waveform to waveform pattern B (step S54).

[0128] The calculation unit 30A also calculates the first frequency f １ Depending on the rise period T ｒ１ and the falling period T ｆ１ is changed (step S55).

[0129] First command value I ｓ１ is the initial command value I ｓ０ , the pressure in the arc is correspondingly lower, so that the first frequency f １ Even if the frequency is higher than a predetermined frequency, the arc noise may be at an acceptable level.

[0130] In this modified example, this point is taken into consideration, and the first frequency f １ and a predetermined frequency, as well as the first command value I ｓ１ and the initial command value I ｓ０ By determining the magnitude relationship between the arc width and the arc ARC, it is possible to appropriately reduce the degree of change in the width of the arc ARC, thereby reducing, for example, the arc noise. In addition, it is possible to weaken the concentration of the arc ARC and adjust the penetration depth.

[0131] The first frequency f １ and the initial frequency f ０ 8 may be executed before step S53. In this way, the frequency of the welding current waveform can be easily and reliably adjusted to the first frequency f １ can be changed to.

[0132] The program according to this modification causes one or more CPUs (processors) to execute the welding current waveform correction method according to this modification. From another perspective, the welding current waveform correction device according to this modification has at least calculation unit 30A, and calculation unit 30A executes the welding current waveform correction process according to this modification.

[0133] In this way, the calculation unit 30A, which is composed of a CPU, executes the welding current waveform correction process, and by programming the welding current waveform correction procedure, the basic waveform can be easily corrected to obtain the desired welding current waveform.

[0134] In step S53 of the flowchart shown in FIG. 12, the first command value I ｓ１ is the initial command value I ｓ０ However, it is determined whether the first command value I ｓ１ and the initial command value I ｓ０ When the difference between the first command value I ｓ１ is the initial command value I ｓ０ Even if the first command value I ｓ１ is the initial command value I ｓ０ That is, it may be determined that the determination result in step S53 is negative.

[0135] In view of this, in step S53, the first command value I ｓ１ exceeds the fourth range and the initial command value I ｓ０ Here, the fourth range is a range in which the first command value I ｓ１ is the initial command value I ｓ０ The first frequency f is within a range that can be considered equivalent to the first frequency f and can be changed as appropriate depending on the welding conditions, the thickness of the base material 200, etc. １ If the frequency is higher than the predetermined frequency, the determination result in step S53 is affirmative, which means that the first command value I ｓ１ exceeds the fourth range and the initial command value I ｓ０ If the determination result in step S53 is negative, the first command value I ｓ１ exceeds the fourth range and the initial command value I ｓ０ This means that it is smaller than

[0136] Other Embodiments The components described in the first to third embodiments and the modified examples can be combined as appropriate to create new embodiments. For example, if the determination result in step S43 of the flowchart shown in Figure 11 is negative, steps S2 to S14 shown in Figure 2 may be executed. Similarly, if the determination result in step S53 of the flowchart shown in Figure 12 is negative, steps S2 to S14 shown in Figure 2 may be executed.

[0137] Although the present specification has been described using DC TIG welding as an example, the present invention is not limited to this and can be applied to consumable electrode DC pulse arc welding, such as pulse MIG welding and pulse MAG welding.

[0138] The welding current waveform correction method in the present specification also includes the following aspect. For example, a welding operator can check the quality of the weld bead after welding and correct the welding current waveform for subsequent welding so as to obtain the desired quality (fifth step). In other words, the fifth step is performed after the second step is performed.

[0139] For example, if it is desired to deepen the penetration after welding the base material 200, in the example shown in FIG. 5, the first peak current value I ｐ１ Specifically, the welding current waveform is corrected so that only the first peak current value I ｐ１ is 100 A, and the second peak current value I ｐ２ is 75 A, and the third peak current value I ｐ３ If the welding current is 50A, it is assumed that after checking the welding result, it is desired to make the penetration a little deeper.

[0140] In this case, the welding operator operates the jog dial or teaching pendant 33 provided on the input unit 32 of the arc welding machine 100 to set the first peak current value I ｐ１Alternatively, the welding current waveform may be changed or adjusted from 100 A to 110 A. It goes without saying that the welding operator does not have to give instructions using a jog dial or teaching pendant 33, as long as the welding operator can instruct the adjustment of the current waveform so as to obtain the desired results. Furthermore, the welding current waveform can be corrected in the same manner as described above depending on the condition of the base material 200 before or after welding.

[0141] The welding current waveform correction method disclosed herein is useful for DC arc welding because it can appropriately correct the welding current waveform depending on the plate thickness and penetration depth of the base material and the frequency of the welding current during welding.

[0142] REFERENCE SIGNS LIST 10 Welding output unit 11 First rectifier unit 12 First switching unit 13 Transformer 14 Second rectifier unit 15 Reactor 16 Second switching unit 20 Welding output detection unit 21 Welding current detection unit 22 Welding voltage detection unit 30 Control unit 30A Calculation unit 31 Memory unit 32 Input unit 33 Teaching pendant (input unit) 40 Welding power source 51 Power cable 52 Power cable 60 Welding torch 70 Electrode 100 Arc welding machine 200 Base material ARC Arc PS Three-phase AC power supply

Claims

1. A method for correcting a welding current waveform in DC arc welding, wherein a welding machine for performing DC arc welding has at least a welding output unit, a welding torch, and a control unit, and the control unit has at least a calculation unit and a memory unit, and the method comprises at least a first step of preparing a basic waveform of a welding current, and a second step of correcting the basic waveform to a welding current waveform having a different waveform pattern in accordance with the plate thickness or penetration depth of a base metal that is an object to be welded, or the frequency of the welding current during welding, wherein the basic waveform is a waveform obtained by plotting the current value of the welding current against discrete times at predetermined time intervals when the plate thickness is the initial plate thickness and the penetration depth is the initial penetration depth, or when the penetration ratio is the initial penetration ratio, A method for correcting a welding current waveform, characterized in that the welding current waveform is a waveform obtained by plotting the current value of the welding current against the time discrete at the time intervals when the plate thickness is the actual plate thickness used for welding the base material and the penetration depth is an actual penetration depth that is the desired penetration depth, or when the penetration ratio is an actual penetration ratio that is the ratio of the actual penetration depth to the actual plate thickness.

2. A method for correcting a welding current waveform as defined in claim 1, wherein the basic waveform fluctuates at a predetermined cycle with respect to the time, and when the actual plate thickness is thicker than the initial plate thickness by more than a first range, or the actual penetration depth is deeper than the initial penetration depth by more than a second range, or the actual penetration ratio is higher than the initial penetration ratio by more than a third range, the welding current waveform has a waveform pattern that rises at a first peak current value higher than the peak current value of the basic waveform and then decreases stepwise or continuously until the cycle has elapsed.

3. A method for correcting a welding current waveform as set forth in claim 2, characterized in that the first peak current value is set to increase as the actual plate thickness increases, or as the actual penetration depth increases, or as the actual penetration ratio increases.

4. A method for correcting a welding current waveform as defined in claim 1, wherein the basic waveform fluctuates at a predetermined cycle with respect to the time, and when the actual plate thickness is thinner than the initial plate thickness by more than a first range, or the actual penetration depth is shallower than the initial penetration depth by more than a second range, or the actual penetration ratio is lower than the initial penetration ratio by more than a third range, the cycle of the welding current waveform is equal to the cycle of the basic waveform, and the basic waveform is corrected so that the rise period of the welding current in the welding current waveform is longer than the rise period of the welding current in the basic waveform, and so that the fall period of the welding current in the welding current waveform is longer than the fall period of the welding current in the basic waveform.

5. A method for correcting a welding current waveform as set forth in claim 4, characterized in that the rise period and fall period are set to become longer as the actual plate thickness becomes thinner, the actual penetration depth becomes shallower, or the actual penetration ratio becomes lower.

6. A welding current waveform correction method as set forth in claim 1, further comprising a third step of at least temporarily storing the welding current waveform obtained in the second step in the memory unit.

7. A method for correcting a welding current waveform as set forth in claim 1, further comprising, after execution of said first step, a fourth step of correcting said basic waveform in accordance with an actual use cycle of said welding current used to weld said base metal, wherein said fourth step, if said actual use cycle is 1 / m times (m is an integer of 2 or more) the cycle of said basic waveform, corrects said basic waveform by arranging on the time axis for each of said time intervals said current values ​​of said welding current extracted from said basic waveform at each of said m times the time interval; and if said actual use cycle is m times the cycle of said basic waveform, corrects said basic waveform by interpolating with respect to said basic waveform (m-1) current values ​​of said welding current between a first time point and a second time point which is the elapsed time interval from said first time point, and then arranging on said time axis for each of said time intervals said interpolated current values.

8. A method for correcting a welding current waveform as set forth in claim 1, wherein in the second step, the basic waveform is corrected to a welding current waveform having a different waveform pattern in accordance with a first frequency which is the frequency of the welding current during welding, the welding current fluctuates with respect to the time at a predetermined cycle, the frequency being the reciprocal of the cycle, the cycle of the welding current waveform being equal to the cycle of the basic waveform, and when the first frequency is higher than the predetermined frequency, the basic waveform is corrected so that the rise period of the welding current in the welding current waveform is longer than the rise period of the welding current in the basic waveform, and so that the fall period of the welding current in the welding current waveform is longer than the fall period of the welding current in the basic waveform.

9. A method for correcting a welding current waveform as set forth in claim 8, wherein in the second step, the basic waveform is corrected to a welding current waveform having a different waveform pattern in accordance with the first frequency and a first command value which is a current command value for the welding current during welding; and when the first frequency is higher than a predetermined frequency and the first command value is greater than a fourth range, the basic waveform is corrected so that the rise period of the welding current in the welding current waveform is longer than the rise period of the welding current in the basic waveform and so that the fall period of the welding current in the welding current waveform is longer than the fall period of the welding current in the basic waveform; and the current command value is a moving average value of the welding current during a predetermined welding period.

10. A method for correcting a welding current waveform as set forth in claim 1, further comprising a fifth step, after execution of said second step, of operating said welding machine to correct said welding current waveform in accordance with the welding result of said base metal or the condition of said base metal.

11. A program for causing one or more processors to execute the welding current waveform correction method according to any one of claims 1 to 10.

12. A welding current waveform correction device, comprising at least the calculation unit, wherein the calculation unit executes the welding current waveform correction method according to any one of claims 1 to 10.

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