Method and program for modifying a welding current waveform

Abstract

The correction method of the welding current waveform of the present disclosure includes first to third steps. In the first step, a basic waveform of a welding current (Aw) is prepared. In the second step, the basic waveform is described as a function with a current command value (Is), a plate thickness (D) of a material to be welded, i.e., a base material (200), and time (t) as variables. In the third step, the basic waveform is corrected as the current command value (Is) in the function described in the second step (S2) is substituted with an actual use command value (I s1 ) used in welding of the base material (200), and the plate thickness (D) in the function is substituted with an actual use plate thickness (D1) used in welding of the base material (200). The corrected basic waveform is acquired as a welding current waveform.

Description

Technical Field

[0001] This disclosure relates to a method for correcting welding current waveforms, and more particularly to a method and procedure for correcting welding current waveforms in AC arc welding. Background Technology

[0002] Typically, the welding current command value is input to the welding power source, and after the welding conditions are set, arc welding is performed (see, for example, Patent Document 1).

[0003] For example, the basic waveform stored in the storage unit of the welding power source is read, and the current command value is adjusted according to the structure and thickness of the workpiece, i.e. the base material, before arc welding is performed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 60-064773 Summary of the Invention

[0007] -The technical problem the invention aims to solve-

[0008] However, in actual arc welding, simply adjusting the current command value to change the welding conditions is sometimes insufficient. For example, when applying a basic waveform designed for medium-thick base materials to welding thin base materials, reducing the current command value can decrease the heat input to the base material. However, depending on the shape of the basic waveform, the heat input to the base material may be excessive, potentially leading to welding defects such as burn-through.

[0009] This disclosure was made in view of the above circumstances, and its purpose is to provide a method and procedure for correcting the welding current waveform that can appropriately correct the welding current waveform according to the thickness of the base material and the current command value.

[0010] - Technical solutions used to solve technical problems -

[0011] To achieve the above objectives, the welding current waveform correction method disclosed herein is a method for correcting the welding current waveform in alternating current arc welding. The method is characterized by: the welding machine performing the alternating current arc welding having at least a welding output unit, a welding torch, and a control unit; the control unit having at least a calculation unit and a storage unit; and the welding current waveform correction method comprising at least a first step, a second step, and a third step. In the first step, a basic waveform of the welding current is prepared. In the second step, the basic waveform is described as a function of a current command value, the thickness of the base material being welded, and time as variables. In the third step, the current command value in the function is substituted into the actual current used in welding the base material. The basic waveform is corrected by substituting the command value, which is also the plate thickness in the function, into the actual plate thickness used in the welding of the base material, thereby obtaining the welding current waveform. The current command value is the moving average of the welding current in the period of the basic waveform. The basic waveform is a waveform obtained by plotting the current value of the welding current at a specified time interval when the current command value is the initial command value and the plate thickness is the initial plate thickness. The welding current waveform is a waveform obtained by plotting the current value of the welding current at the time interval when the current command value is the actual usage command value and the plate thickness is the actual usage plate thickness.

[0012] The program disclosed herein is used to cause one or more processors to execute the method for correcting the welding current waveform.

[0013] -The effects of the invention-

[0014] According to this disclosure, the welding current waveform can be appropriately modified based on the thickness of the base material and the current command value. Attached Figure Description

[0015] Figure 1 This is a schematic structural diagram of the arc welding machine according to the first embodiment.

[0016] Figure 2 This is a flowchart illustrating the steps for correcting the welding current waveform.

[0017] Figure 3 This is a schematic diagram showing the basic waveform of welding current.

[0018] Figure 4 yes Figure 3 An enlarged view of the portion surrounded by dashed lines.

[0019] Figure 5 This is a schematic diagram showing the change in the rising portion of the basic waveform as the plate thickness decreases.

[0020] Figure 6 This is a schematic diagram showing the change in the rising portion of the basic waveform as the current command value decreases.

[0021] Figure 7 This is a flowchart illustrating the steps for correcting the welding current waveform according to the second embodiment.

[0022] Figure 8 This is a conceptual diagram used to illustrate the steps involved in halving the period of a basic waveform.

[0023] Figure 9 This is a conceptual diagram used to illustrate the steps involved in doubling the period of a basic waveform. Detailed Implementation

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the following description of preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0025] (First Implementation)

[0026] [Structure of an arc welding machine]

[0027] Figure 1 A schematic structural diagram of an arc welding machine according to the first embodiment is shown. The arc welding machine 100 includes a welding power source 40 and a welding torch 60.

[0028] The welding power source 40 converts the AC power supplied from the three-phase AC power source PS into AC power suitable for arc welding and outputs it to the electrode 70 held on the welding torch 60. In this embodiment, a welding current Aw is supplied from the welding power source 40 to the electrode 70. The base material 200 is welded by generating an arc ARC between the tip of the electrode 70, to which the welding current Aw is supplied, and the base material 200. That is, AC TIG welding is performed by the arc welding machine 100. It should be noted that the output of the welding power source 40 can be changed depending on the arc welding method. For example, the output of the welding power source 40 can also be a welding voltage Vw applied between the base material 200 and the electrode 70.

[0029] The welding power supply 40 has at least a welding output section 10, a welding output detection section 20, a control section 30, and an input section 32. The welding output section 10 has a first rectifier section 11, a first switch section 12, a transformer 13, a second rectifier section 14, a reactor (DCL) 15, and a second switch section 16.

[0030] The first rectifier section 11, composed of rectifier elements such as diodes, rectifies the AC power received from the three-phase AC power supply PS. The first switching section 12, for example, is a DC-AC converter circuit composed of multiple transistors. At a timing corresponding to a control command from the control unit 30, the multiple transistors are switched, thereby controlling the output of the first rectifier section 11 to an output suitable for welding. The transformer 13, for example, is a transformer with an iron core, converting the output of the first switching section 12 into an output suitable for welding. The second rectifier section 14 has the same structure as the first rectifier section 11 and rectifies the output of the transformer 13. The reactor 15 is connected in series with the second rectifier section 14, and the reactor 15 smooths the output of the second rectifier section 14. The second switching section 16 has the same structure as the first switching section 12. That is, the second switching section 16 is a DC-AC converter circuit composed of multiple transistors. At a timing corresponding to a control command from the control unit 30, the multiple transistors are switched, thereby adjusting the output of the reactor 15.

[0031] In this embodiment, the output of the second switch unit 16 is the aforementioned welding current Aw, which is supplied to the electrode 70 held in the welding torch 60 via the power cable 51. It should be noted that when the output of the second switch unit 16 is the welding voltage Vw, a predetermined voltage is applied between the electrode 70 and the base material 200 via the power cables 51 and 52, respectively.

[0032] The welding output detection unit 20 includes a welding current detection unit 21 and a welding voltage detection unit 22. The welding current detection unit 21 detects the welding current Aw supplied to the electrode 70, and the welding voltage detection unit 22 detects the welding voltage Vw applied between the electrode 70 and the base material 200. The results detected by the welding current detection unit 21 and the welding voltage detection unit 22 are respectively sent to the control unit 30 for controlling the arc welding.

[0033] The control unit 30 is composed of one or more CPUs (Central Processing Units). Alternatively, the control unit 30 is composed of one or more MCUs (Micro Control Units). Furthermore, the control unit 30 has an arithmetic unit 30A composed of one or more CPUs. If at least one of the current command value (described later) and the thickness of the base material 200 is input to the arithmetic unit 30A, the arithmetic unit 30A performs welding current waveform correction processing. In other words, the arithmetic unit 30A performs welding current waveform correction processing in three modes: when only the current command value is input, when only the plate thickness is input, and when both the current command value and the plate thickness are input.

[0034] It should be noted that, in Figure 1In the example shown, the storage unit 31 is set independently of the control unit 30. The storage unit 31 is composed of semiconductor memory such as RAM (Random Access Memory) or ROM (Read Only Memory). The storage unit 31 can also be composed of HDD (Hard Disk Drive) or SSD (Solid State Drive). It should be noted that the storage unit 31 can also be a functional block of the CPU or MCU, i.e., a ROM or RAM built into the CPU or MCU. The storage unit 31 stores the control programs and welding parameters for various equipment used in arc welding. Furthermore, the storage unit 31 stores a program that describes the correction steps for the welding current waveform, which will be described later.

[0035] The control unit 30 controls the switching actions of the first switch unit 12 and the second switch unit 16 according to the prescribed welding procedure. Specifically, the control unit 30 controls the switching action of the second switch unit 16 based on a preset current command value Is and the AC cycle (hereinafter referred to as the cycle) of the welding current Aw. Furthermore, the control unit 30 receives the detection result from the welding current detection unit 21 and, based on this result, controls the switching actions of the first switch unit 12 and the second switch unit 16 to make the welding current Aw reach the preset current command value Is. It should be noted that the current command value Is refers to the moving average value of the welding current Aw during the set welding period Tw.

[0036] The input unit 32 may consist of a display device such as a liquid crystal display and input devices such as a keyboard, input buttons, and a rotary encoder with a switch. When the display device is a touch panel or the like, the input devices may be omitted.

[0037] Input unit 32 is used to input welding conditions during arc welding, such as the actual use command value I described later. s1 The actual thickness of the base material is D1, which is 200 mm.

[0038] It should be noted that the welding torch 60 can also be held by a robot (not shown). In this case, the robot moves the welding torch 60 at a predetermined speed (welding speed) along a pre-set welding line (not shown) such that the distance between the tip of the electrode 70 and the surface of the base material 200 is within a pre-set range.

[0039] It should be noted that, in Figure 1In the example shown, the input unit 32 is located within the welding power supply 40, but it can also be located outside the welding power supply 40 as long as it can communicate with the control unit 30. For example, the teach pendant (TP) 33 used to teach the robot the movement trajectory of the welding torch 60 can also be the input unit 32. It should be noted that in this case, the communication method between the teach pendant 33, which serves as the input unit 32, and the control unit 30 can be either wired or wireless.

[0040] Furthermore, although not illustrated, filler metal can also be used during arc welding. The filler metal is composed of a metal of the same material as the base metal 200, melted by the arc welding (ARC), and serves as a source of metal supply to maintain the strength and appearance of the weld. It should be noted that filler metal is not mandatory and can be omitted depending on the requirements of the weld and the shape of the base metal 200.

[0041] [Steps for correcting welding current waveform]

[0042] Normally, when using the arc welding machine 100 to perform AC TIG welding, the basic waveform of the welding current Aw stored in the storage unit 31 (hereinafter referred to as the basic waveform) is read out to the control unit 30, and the current command value is changed to a value suitable for welding the base material 200.

[0043] However, when the basic waveform remains unchanged but the current command value is changed, for example when the base material 200 is a thin plate, burn-through may sometimes occur depending on the shape of the waveform, which is consistent with the previous description.

[0044] Therefore, in this embodiment, a method is proposed to obtain a time waveform of the welding current (hereinafter referred to as the welding current waveform) by modifying the basic waveform according to the thickness of the base material 200 and the current command value. The following description will further elaborate on this method with reference to the accompanying drawings.

[0045] Figure 2 This is a flowchart illustrating the steps for correcting the welding current waveform. Figure 3 This is a schematic diagram showing the basic waveform of welding current. Figure 4 yes Figure 3 An enlarged view of the portion surrounded by dashed lines.

[0046] like Figure 2 As shown, a basic waveform is prepared (step S1). The basic waveform is stored in the storage unit 31 as described above and read out to the control unit 30. It should be noted that, as... Figure 3 As shown, the basic waveform in this embodiment is during the period T when the base material 200 is positive and the electrode 70 is negative. EN (Also known as the period of negative electrode polarity T) ENThe process includes three periods, T1 to T3. Period T1 is when the welding current Aw rises from zero to a constant positive value I. EN The period up to this point. Period T2 is the period during which the welding current Aw remains at a constant positive value I. EN During the period T3, the welding current Aw changes from a constant value I. EN The period until it drops to zero. Furthermore, during the period T when the base material 200 is negative polarity and the electrode 70 is positive polarity. EP (Also known as the period of positive electrode polarity T) EP The process includes the following three periods, T4 to T6. Period T4 is when the welding current Aw decreases from zero to a constant negative value I. EP The period up to this point. During period T5, the welding current Aw remains at a negative constant value I. EP During the period T6, the welding current Aw changes from a constant value I. EP The period from rising to zero.

[0047] It should be noted that, as Figure 4 As shown, the welding current Aw is for a time interval T. INV The waveform of the current value is obtained by plotting the discrete time interval t. Here, the time interval T is... INV This is the control cycle of the control unit 30 to the second switching unit 16. Furthermore, the basic waveform is based on the welding current Aw having a current command value of the initial command value I. s0 And given that the thickness of the base material 200 is the initial thickness D0, for a time interval T INV The waveform of the welding current Aw is obtained by plotting the discrete time t.

[0048] Next, the basic waveform is described using a function with the current command value Is, the thickness D of the base material 200, and time t as variables (step S2). This function is a collection of multiple sub-functions. Figure 3 In the example shown, during the period T1 (time 0 to time ta), the welding current Aw is described by the sub-function shown in equation (1).

[0049] Aw = I EN (1-e) （－t／A） ) ···(1)

[0050] Furthermore, the sub-function A, as a function of the plate thickness D, is described in the form shown in equation (2).

[0051] A = α × D / D0 ···(2)

[0052] In addition, the current value I EN When considered as a subfunction of the current command value Is and the plate thickness D, the subfunction I ENIt is described in the form shown in equation (3).

[0053] I EN =β×Is / I s0 ×(D / D0)···(3)

[0054] Here, α and β are positive constants. Furthermore, in the following explanation, D0 will be referred to as the initial plate thickness, and I... s0 This is called the initial instruction value.

[0055] Furthermore, during the period T2 (time ta to time tb), the welding current Aw is described as a subfunction with at least one of the current command value Is and the plate thickness D as variables, in the form shown in equation (3). That is, during the period T2, the welding current Aw does not depend on time t.

[0056] During the period T3 (time tb ~ time tc), the welding current Aw is described by the sub-function shown in equation (4).

[0057] Aw = B × (1 / e) （（t―tc）／A） -1) = B × (e （（tc―t）／A） -1)···(4)

[0058] Here, B is the coefficient that satisfies the relationship shown in equation (5).

[0059] B = I EN / (e （（tc―tb）／A） )-1) ···(5)

[0060] The welding current Aw during period T4 (time tc to time td) is described by a transformation of the subfunction shown by equation (4), so the explanation is omitted. Similarly, the welding current Aw during period T5 (time td to time te) and the welding current Aw during period T6 (time te to time tn) are described by transformations of the subfunctions shown by equations (3) and (1), respectively, so the explanation is omitted.

[0061] It should be noted that the sub-function describing the waveform of the welding current Aw can be appropriately changed according to the shape of the basic waveform. For example, when the time gradient of the current, that is, the increase or decrease of the welding current Aw relative to time t, is linear, equations (1) and (4) can be transformed into equations (1A) and (4A) as shown below.

[0062] Aw = I EN ×a×t ···(1A)

[0063] Aw = I EN ×b×(tc-t)···(4A)

[0064] Here, a and b are positive constants, and b = 1 / (tc - tb). Alternatively, equation (2) can be transformed into equation (2A) as shown below.

[0065] A=α1×((D-D0) / D0)···(2A)

[0066] Here, α1 is a positive constant.

[0067] Next, the actual current command value used in welding, i.e., the actual current command value I, will be used. s1 The actual plate thickness D1 and the actual plate thickness used are substituted into the sub-functions shown in step S2 (step S3). For example, according to equation (2), the value of sub-function A varies according to the ratio of the actual plate thickness D1 to the initial plate thickness D0. Thus, the time gradient of welding current Aw varies according to the actual plate thickness D1.

[0068] Based on the values ​​substituted in step S3, change and correct the basic waveform. Use the result as the welding current waveform (step S4).

[0069] As can be seen from the above explanation, the basic waveform is based on the welding current Aw with the initial command value I. s0 And given that the thickness of the base material 200 is the initial thickness D0, for the aforementioned time interval T INV The waveform of the welding current Aw is obtained by plotting the discrete time t.

[0070] The welding current waveform obtained in step S4 is based on the welding current Aw current command value being the actual usage command value I. s1 And if the thickness of the base material 200 is the actual thickness D1 used, then for the aforementioned time interval T INV The waveform of the welding current Aw is obtained by plotting the current value over discrete time t. The welding current waveform obtained in step S4 is temporarily stored in the storage unit 31 and used as the actual use command value I when the current command value is used. s1 The basic waveform is used when welding with a base material thickness of 200mm as the actual plate thickness D1.

[0071] [Effects, etc.]

[0072] As described above, the method for correcting the welding current waveform in AC arc welding according to this embodiment uses an arc welding machine 100 having at least a welding output unit 10, a welding torch 60, and a control unit 30 when performing the first to third steps shown below. The control unit 30 has at least an arithmetic unit 30A and a storage unit 31.

[0073] In the first step, prepare the basic waveform of the welding current Aw ( Figure 2Step S1).

[0074] In the second step, the basic waveform is described as a function of the current command value Is, the thickness D of the substrate 200, and time t. Figure 2 Step S2).

[0075] In the third step, the current command value Is, which is the function described in step S2, is substituted into the actual usage command value I used in the welding of the base material 200. s1 Furthermore, the plate thickness D in this function is substituted into the actual plate thickness D1 used in welding the base material 200 to correct the basic waveform. The corrected basic waveform is then used as the welding current waveform. Figure 2 Steps S3 and S4).

[0076] The current command value Is is the moving average of the welding current Aw over the period T of the basic waveform. The basic waveform is based on the welding current Aw with the initial command value Is. s0 And given that the thickness of the base material 200 is the initial thickness D0, for a specified time interval T INV The waveform of the welding current Aw is obtained by plotting the current value over a discrete time period t. The welding current waveform is based on the current command value of welding current Aw and the actual usage command value I. s1 Furthermore, when the thickness of the base material 200 is the actual thickness D1 used, the waveform of the welding current Aw is obtained by plotting the current value for time t, which is discrete with the aforementioned time interval TINV.

[0077] As mentioned above, when welding a base material 200 with an actual usable thickness D1 that is much thinner than the initial thickness D0, using a basic waveform that corresponds to the preset initial plate thickness D0 and initial command value Is0, the base material 200 may burn through depending on the shape of the basic waveform.

[0078] On the other hand, according to this embodiment, the basic waveform is described as a function of the current command value Is, the thickness D of the substrate 200 being welded, and time t, specifically using a set of multiple sub-functions, and is based on the actual command value I used. s1 The actual plate thickness D1 is used to correct each sub-function. This allows for a simple and appropriate acquisition of the waveform of the welding current Aw used in actual welding. Further explanation follows.

[0079] Figure 5 This is a schematic diagram illustrating the change in the rising portion of the basic waveform as the plate thickness decreases. For example... Figure 5 As shown, when the actual plate thickness D1 is reduced, the welding current Aw reaches a constant value I. ENThe current rise period T1a is longer than the rise period T1 when the base material thickness is 200 mm and the initial thickness D0. This is because, as shown in equation (2), the value of the sub-function A increases. That is, when the actual used thickness D1 is smaller than the initial thickness D0, the welding current Aw reaches a constant value I. EN The rising period T1a becomes longer, which makes the heat input to the base material 200 more gradual, thereby suppressing the burn-through of the base material 200.

[0080] Furthermore, it can be seen from equation (3) that the constant value I of the welding current Aw is... EN Based on the actual usage instruction value I s1 With the initial instruction value I s0 It changes according to the ratio.

[0081] Figure 6 This is a schematic diagram illustrating the change in the rising portion of the basic waveform when the current command value is reduced. For example... Figure 6 As shown, when the actual instruction value I is used s1 When decreasing, the constant value I EN Decrease to a constant value I EN1 This is because, as can be seen from equation (3), the sub-function I... EN The value decreases. Furthermore, the welding current Aw reaches a constant value I. EN1 During the rising period up to this point, T1 remains unchanged, but due to the constant value of the welding current Aw from I... EN Reduce to I EN1 Therefore, the time gradient of the welding current Aw during period T1 is greater than the current command value of the welding current Aw, which is the initial command value I. s0 Low time.

[0082] In this case, the heat input to the base material 200 can be reduced, and the heat input to the base material 200 becomes gradual in the early stage of welding, thus suppressing the burn-through of the base material 200.

[0083] Furthermore, in AC TIG welding, during the negative polarity period of the electrode, T EN This generates a highly directional arc (ARC), thus enabling the formation of narrow, deep welds. Furthermore, during the positive polarity period of the electrode, T... EP A cathode point, serving as the electron release point, is formed on the surface of the base material 200, and then the cathode point moves on the surface of the base material 200. That is, during the positive polarity period T... EP This process cleans the surface of the base material 200. Thus, for example in an aluminum-based base material 200, the oxide film formed on the surface can be removed, resulting in a clean surface suitable for welding.

[0084] On the other hand, according to this embodiment, the basic waveform of the welding current Aw, which is an alternating waveform, is corrected according to the aforementioned steps. During the negative polarity period of the electrode TEP By describing the rising, falling, and constant current periods using appropriate sub-functions, the generation and growth of the electric arc (ARC) can be properly controlled. Therefore, the actual command value I can be determined based on the specific application. s1 The actual plate thickness D1 is used to generate an electric arc ARC for the desired welding, which irradiates the base material 200. Furthermore, during the positive polarity of the electrode, T... EP Similarly, by describing the rising period, falling period, and constant current period with appropriate sub-functions, the cleaning effect on the surface of the base material 200 can be appropriately controlled.

[0085] The sub-function describing the rise period of the welding current Aw in the basic waveform is preferably an increasing function with respect to both time t and plate thickness D. This allows the time gradient of the welding current Aw to decrease as the plate thickness D decreases, thereby suppressing burn-through in the thin base material 200.

[0086] In the second step, different sub-functions can also be used to describe the different periods of the time gradient of the welding current Aw in the basic waveform. For example, it is preferable to make the sub-function forms different for the rising and falling periods of the current. Taking the negative electrode polarity period T... EN For example, during the rising period of the current, an arc ARC is generated and allowed to grow to the desired arc length. Furthermore, during the falling period of the current, the arc ARC shrinks but is not extinguished. Thus, in order to appropriately utilize the respective functions of the arc ARC during different periods of its influence, the sub-functions describing the welding current Aw can be made different.

[0087] The welding output unit 10 of the arc welding machine 100 has a second switching unit 16, which is an inverter for controlling the time variation of the welding current Aw. Time interval T INV This is the control cycle of the inverter. It should be noted that in the arc welding machine 100, the time interval T... INV In other words, the inverter's control frequency is a fixed value.

[0088] By time interval T INV This setting allows for easy handling of the basic waveform period change process, which will be described later. It should be noted that if the frequency of the basic waveform is 10Hz, then the period T is 100ms. If the time interval T... INV If the time interval is 12.5 μsec, then the basic waveform consists of data composed of 8000 point clouds.

[0089] Preferably, a fifth step is also included, in which the welding current waveform obtained in the third step is at least temporarily stored in the storage unit 31. This allows the modified welding current waveform to be directly used when welding again at an interval for the same type of base material 200, thereby simplifying the setting of welding conditions. It should be noted that if the storage unit 31 stores multiple patterns of various sub-functions, it is not necessary to permanently store the modified welding current waveform in the storage unit 31. This is because the desired welding current waveform can be obtained by modifying the basic waveform using each sub-function.

[0090] The program involved in this embodiment causes one or more CPUs (processors) to execute the aforementioned method for correcting welding current waveforms.

[0091] By proceduralizing the steps for correcting the welding current waveform as described above, the basic waveform can be easily corrected to obtain the desired welding current waveform.

[0092] (Second Implementation)

[0093] Figure 7 This is a flowchart of the steps for correcting the welding current waveform according to the second embodiment. Figure 8 This is a conceptual diagram used to illustrate the steps involved in halving the period of a basic waveform. Figure 9 This is a conceptual diagram illustrating the steps involved in doubling the period of a basic waveform. It should be noted that... Figures 7-9 In this document, for ease of explanation, the same symbols are used for the parts that are the same as in the first embodiment, and detailed descriptions are omitted.

[0094] exist Figure 7 In the flowchart shown, steps S11, S13-S15 and Figure 2 Steps S1 to S4 in the flowchart shown are the same, so the explanation is omitted. Figure 7 The flowchart shown is Figure 2 The difference in the flowchart shown is that the basic waveform period change process shown in step S12 has been added.

[0095] Step S12 (fourth step) is performed between step S11 (first step) and step S13 (second step). Specifically, in step S12, the basic waveform is corrected based on the period of the welding current Aw used in welding the base material 200 (hereinafter referred to as the actual usage period). This will be further explained.

[0096] In the basic waveform, the fundamental period T (hereinafter simply referred to as period T) is predetermined. Furthermore, as mentioned earlier, the period T is the time interval T. INV Integer multiples of.

[0097] T = n × TINV ···(6)

[0098] Here, n is an integer, which is the period T divided by the time interval T. INV The obtained value.

[0099] Therefore, using the period T as the time interval T INV In the case of n times the value of the basic waveform, the period T can be easily changed. In step S12, the period of the basic waveform is changed according to the steps shown below.

[0100] When the actual usage period is half the period T of the basic waveform, such as Figure 8 As shown, data is extracted from the basic waveform at each time interval T. INV The welding current Aw is extracted over twice the period, and then the extracted current values ​​are plotted at each time interval T on the time axis. INV The internal arrangement is carried out to correct the basic waveform.

[0101] When the actual usage period is twice the period T of the basic waveform, such as Figure 9 As shown, for the basic waveform, the time interval T between the first moment and the time elapsed since the first moment is... INV Between the second and third moments, interpolate a welding current value Aw, and then record the interpolated multiple current values ​​at each time interval T on the time axis. INV The internal arrangement is carried out to correct the basic waveform.

[0102] In AC TIG welding, it is sometimes desirable to change the period, or frequency, of the welding current waveform. By increasing the frequency, the directionality and focus of the arc (ARC) are improved, resulting in a narrower weld with deeper penetration. On the other hand, by decreasing the frequency, the width of the cleaned surface of the base material 200 in the direction intersecting with the welding direction can be increased. Therefore, it is preferable to change the frequency of the welding current waveform by considering factors such as the material of the base material 200 and the aesthetic appearance of the weld.

[0103] According to this embodiment, the period T of the basic waveform can be easily changed through simple data processing, thereby easily changing the frequency of the modified welding current waveform.

[0104] It should be noted that in the welding current waveform correction method of this embodiment, the fourth step can be extended as follows.

[0105] When the actual usage period is 1 / m times the period T of the basic waveform (where m is an integer greater than or equal to 2), each m-time interval T in the basic waveform will be used. INV The extracted welding current Aw value is displayed at each time interval T on the time axis. INVThe internal arrangement is carried out to correct the basic waveform.

[0106] When the actual usage period is m times the period T of the basic waveform, for the basic waveform, the time interval T between the first moment and the time interval T elapsed from the first moment... INV Between the second and third moments, interpolate the current values ​​of (m-1) welding currents Aw, and then plot the interpolated current values ​​at each time interval T on the time axis. INV The internal arrangement is carried out to correct the basic waveform.

[0107] It should be noted that, in Figure 7 In the example shown, the period T is changed by directly extracting or interpolating data from the basic waveform. However, when the period T is extended to a factor of m, sometimes, preferably, after the second step—in other words, for the basic waveform described as a set of multiple sub-functions—the period T is changed by interpolating data. This allows one or more data points to be interpolated between the first and second time points at a position closer to the actual waveform, thus ensuring that the shape of the basic waveform after the period T change remains similar to the original basic waveform. That is, the shape of the basic waveform is deformed into an undesirable shape, thereby preventing burn-through and other issues caused by imbalances in the heat input to the base material 200.

[0108] It should be noted that by combining the process of changing the period T to a multiple of (1 / i) (where i is an integer greater than or equal to 2) with the process of changing the period (T / i) to a multiple of j (where j is an integer greater than or equal to 2), the period T can be set to any value. For example, if T = 100 msec and i = 100, the changed period is 1 msec. Then, if the period is changed to a multiple of j (= 33), the changed period is 33 msec. When the period T is 100 msec, the frequency of the basic waveform is 10 Hz, and the frequency of the basic waveform after the two-stage change process is approximately 30 Hz.

[0109] Furthermore, the program involved in this embodiment causes one or more CPUs (processors) to execute a method for correcting the welding current waveform, including the fourth step.

[0110] By proceduralizing the steps for correcting the welding current waveform as described above, the period T of the basic waveform can be easily changed and the basic waveform corrected to obtain the desired welding current waveform.

[0111] (Other implementation methods)

[0112] This application specification uses AC TIG welding as an example, but it is not limited to this and can also be applied to consumable electrode AC arc welding, such as AC MIG welding and AC MAG welding.

[0113] -Industry Applicability-

[0114] The welding current waveform correction method disclosed herein is useful for AC arc welding because it can appropriately correct the welding current waveform according to the thickness of the base material and the current command value.

[0115] - Symbol Explanation -

[0116] 10 Welding Output Section

[0117] 11 First Rectifier Section

[0118] 12 First Switch Section

[0119] 13 Transformers

[0120] 14 Second Rectifier Section

[0121] 15 Reactors

[0122] 16 Second Switch Section

[0123] 20 Welding Output Inspection Department

[0124] 21 Welding Current Detection Department

[0125] 22 Welding Voltage Detection Department

[0126] 30 Control Department

[0127] 30A Computing Unit

[0128] 31 Storage Department

[0129] 32 Input Section

[0130] 33. Teach pendant (input section)

[0131] 40 Welding Power Supply

[0132] 51 Power Cables

[0133] 52 Power cables

[0134] 60 welding torch

[0135] 70 electrodes

[0136] 100 Arc Welding Machine

[0137] 200 base material

[0138] ARC arc

[0139] PS Three-phase AC power supply.

Claims

1. A method for correcting the welding current waveform in alternating current arc welding, characterized in that: The welding machine for performing the AC arc welding has at least a welding output unit, a welding torch, and a control unit. The control unit has at least a computing unit and a storage unit. The method for correcting the welding current waveform includes at least a first step, a second step, and a third step. In the first step, the basic waveform of the welding current is prepared. In the second step, the basic waveform is described as a function of the current command value, the thickness of the substrate (i.e., the base material), and time as variables. In the third step, the actual usage command value used in welding the base material is substituted into the current command value in the function, and the actual usage plate thickness used in welding the base material is substituted into the plate thickness in the function to correct the basic waveform and obtain the welding current waveform. The current command value is a moving average of the welding current over the period of the basic waveform. The basic waveform is obtained by plotting the welding current value at specified time intervals, given that the current command value is the initial command value and the plate thickness is the initial plate thickness. The welding current waveform is a waveform obtained by plotting the current value of the welding current for the time interval discretely when the current command value is the actual use command value and the plate thickness is the actual use plate thickness.

2. The method for correcting welding current waveform according to claim 1, characterized in that: In the second step, the welding current in the basic waveform is described by different sub-functions during different time gradients.

3. The method for correcting welding current waveform according to claim 2, characterized in that: The sub-function describing the rise period of the welding current in the basic waveform is an increasing function of both the time and the plate thickness.

4. The method for correcting welding current waveform according to claim 1, characterized in that: The method for correcting the welding current waveform further includes a fourth step, in which, after performing the first or second step, the basic waveform is corrected according to the actual usage cycle of the welding current used in the welding of the base material. In the fourth step, When the actual usage period is 1 / m times the period of the basic waveform, the current values ​​of the welding current extracted from the basic waveform in each time interval of m times the basic waveform are arranged on the time axis in each time interval, thereby correcting the basic waveform, where m is an integer greater than or equal to 2. When the actual usage period is m times the period of the basic waveform, for the basic waveform, between the first moment and the second moment after the time interval has elapsed from the first moment, (m-1) current values ​​of the welding current are interpolated, and multiple interpolated current values ​​are arranged in each time interval on the time axis, thereby correcting the basic waveform.

5. The method for correcting welding current waveform according to claim 1, characterized in that: The method for correcting the welding current waveform further includes a fifth step, in which the welding current waveform obtained in the third step is at least temporarily stored in the storage unit.

6. A program, characterized in that: The program is used to cause one or more processors to execute the method for correcting the welding current waveform as described in any one of claims 1 to 5.

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