Arc welding method and arc welding control program

Abstract

To provide an arc welding method capable of reducing spatters when a set voltage is changed while keeping a set current at a predetermined value.SOLUTION: In the consumable electrode type arc welding method, a base material 35 is arc-welded by alternately repeating a short circuit period Ts in which a welding wire 34 and the base material 35 are short-circuited and an arc period Ta in which an arc is generated between the welding wire 34 and the base material 35. The arc welding method includes a step of calculating an electric power integrated value by integrating the electric power supplied to the welding wire 34 after the short circuit of the welding wire 34 is detected, and a step of reducing the welding current supplied to the welding wire 34 when the electric power integrated value exceeds a predetermined threshold. The thresholds are changed according to the set voltage V1.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an arc welding method and an arc welding control program. [Background technology]

[0002] In consumable electrode arc welding, just before the short circuit between the welding wire and the base metal is released, a constriction (also called a neck) occurs between the welding wire and the molten part formed on the base metal. By detecting the occurrence of this constriction, the release of the short circuit is detected and the control of the welding current is switched.

[0003] However, when the welding wire is made of a material with low resistivity, such as copper or aluminum, even if a constriction occurs, the change in welding voltage due to the constriction is small and the variation is large, which may lead to an erroneous determination of the presence or absence of a constriction. In this case, for example, if a constriction is not detected despite its occurrence, a large welding current may continue to flow even after the short circuit is released, which may result in the generation of a large amount of spatter.

[0004] Therefore, in arc welding using a welding wire made of a material with low resistivity, a method has been proposed in which the welding current is controlled using an integrated value of power during welding, rather than by detecting necking (see, for example, Patent Document 1).

[0005] In the conventional method disclosed in Patent Document 1, spatter is reduced by reducing the welding current when the integrated power value is greater than a predetermined threshold. This threshold varies depending on the set current, and the magnitude relationship between the integrated power value and the threshold is determined immediately before or near the time of short circuit release. This threshold is also set to an optimal value for reducing spatter. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2020 / 235293 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional method disclosed in Patent Document 1, when the set voltage is changed without changing the set current, the threshold value described above does not change.

[0008] However, changing the set voltage also changes the short-circuit period, i.e., the period during which the welding wire is in contact with the base material. Therefore, in the conventional method disclosed in Patent Document 1, if the threshold is not changed, there is a risk of problems such as a deviation in the timing of reducing the welding current, resulting in an increase in the amount of spatter. For example, if the timing of reducing the welding current is earlier than appropriate, the welding current may decrease before the short circuit is released, which could result in the welding wire being torn off. Furthermore, if the timing of reducing the welding current is later than appropriate, there may be a period during which a large welding current continues to flow even after the short circuit is released, which could result in a large amount of spatter.

[0009] The present disclosure has been made in consideration of the above points, and its purpose is to provide an arc welding method and an arc welding control program that can reduce spatter when the set voltage is changed. [Means for solving the problem]

[0010] In order to achieve the above object, the arc welding method according to the present disclosure is a consumable electrode arc welding method in which the base material is arc-welded by alternately repeating a short-circuit period in which a short-circuit state occurs in which a welding wire is short-circuited to the base material and an arc period in which an arc occurs between the welding wire and the base material, and the method includes the steps of: integrating power supplied to the welding wire after a short circuit of the welding wire is detected to calculate an integrated power value; and reducing the welding current supplied to the welding wire when the integrated power value exceeds a predetermined threshold value, wherein the threshold value is changed according to a set voltage.

[0011] An arc welding control program according to the present disclosure causes one or more processors to execute the arc welding method. [Effects of the Invention]

[0012] According to the present disclosure, in consumable electrode arc welding, when the set voltage is changed while the set current is kept at a predetermined value, spatter can be reduced. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of an arc welding device according to an embodiment; [Figure 2] 10 is a time chart of various output waveforms when the set voltage is a unitary voltage. [Figure 3] 10 is a time chart of various output waveforms when the set voltage is increased by 2 V from the unitary voltage. [Figure 4] 10 is a time chart of various output waveforms when the set voltage is reduced by 2 V from the unitary voltage. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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.

[0015] (Embodiment) [Configuration of arc welding equipment] FIG. 1 is a schematic diagram of an arc welding apparatus according to an embodiment. As shown in FIG. 1, an arc welding apparatus 40 includes a welding power source 10, a welding torch 30, a wire feeder 32, and a setting unit 22.

[0016] The welding power source 10 has a first rectifier unit 11, a first switching unit 12, a transformer 13, a second rectifier unit 14, a second switching unit 15, a resistor 16, a reactor 17, a welding current detection unit 18, a welding voltage detection unit 19, and a control unit 20.

[0017] First rectifier 11 rectifies the input voltage input from input power source S external to welding power source 10. First switching unit 12 adjusts the output of first rectifier 11 by switching operation. Transformer 13 converts the output of first switching unit 12 into an output suitable for welding.

[0018] The second rectifier 14 rectifies the output of the transformer 13. The second switching unit 15 adjusts the output of the second rectifier 14 by switching operation. The resistor 16 is connected in parallel with the second switching unit 15.

[0019] The reactor 17 is connected in series with the second switching unit 15. The reactor 17 smoothes the output of the second switching unit 15.

[0020] Welding current detection unit 18 detects the welding current supplied between welding wire 34, which is a consumable electrode, and base material 35. A detection signal indicating the welding current detected by welding current detection unit 18 is transmitted to control unit 20.

[0021] The welding voltage detection unit 19 detects the welding voltage supplied between the welding wire 34 and the base material 35. A detection signal indicating the welding voltage detected by the welding voltage detection unit 19 is sent to the control unit 20.

[0022] The control unit 20 is configured with one or more CPUs (Central Processing Units) (not shown) and a memory electrically connected to the CPUs for storing programs and information for operating the CPUs. The memory also stores an arc welding control program, which will be described later.

[0023] Control unit 20 transmits signals between each unit of welding power source 10 and wire feeder 32 or setting unit 22. For example, control unit 20 controls the welding output by outputting a control signal to first switching unit 12 and second switching unit 15. Control unit 20 outputs a control signal to wire feeder 32 to control the wire feed speed.

[0024] The control unit 20 has a calculation unit 21, which calculates an integrated power value by integrating the power supplied to the welding wire 34 within a predetermined period after the welding wire 34 is short-circuited. The power supplied to the welding wire 34 is calculated based on the product of the welding current and the welding voltage.

[0025] Control unit 20 compares the welding voltage detected by welding voltage detection unit 19 with a preset threshold voltage. If the welding voltage is equal to or less than the threshold voltage, it determines that a short circuit has occurred. On the other hand, if the welding voltage exceeds the threshold voltage, it determines that an arc has occurred.

[0026] The welding torch 30 is provided with a welding tip 31 for supplying power to a welding wire 34 .

[0027] Wire feeder 32 controls the feeding of welding wire 34 based on a signal from controller 20. Specifically, wire feeder 32 performs constant feed control to feed welding wire 34 toward base material 35 at a predetermined feed speed. Wire feeder 32 also performs forward / reverse feed control to alternately feed welding wire 34 in a forward direction toward base material 35 and in a reverse direction opposite to the forward feed.

[0028] When forward and reverse feed control is performed, the welding wire 34 alternates between forward and reverse feed at a predetermined cycle. This alternates between a short circuit state in which the welding wire 34 is short-circuited with the base metal 35, which is the workpiece, and an arc state in which an arc 36 is generated between the welding wire 34 and the base metal 35. In other words, by performing forward and reverse feed control, the short circuit state and the arc state are mechanically alternated.

[0029] It should be noted that wire feeder 32 may switch between forward and reverse feed depending on the state of the welding phenomenon, rather than periodically switching between forward and reverse feed, when feeding welding wire 34. Specifically, when welding wire 34 and base material 35 are short-circuited and a short circuit state occurs, welding wire 34 may be fed in the reverse direction, and when the short circuit is released and an arc state occurs, welding wire 34 may be fed in the forward direction.

[0030] Setting unit 22 is used to set welding conditions in welding power source 10. For example, setting unit 22 is an input unit such as a touch panel or a keyboard. When a welding operator operates setting unit 22, a set current and a set voltage, which will be described later, are set in the arc welding control program.

[0031] The welding output of the welding power source 10 is supplied to the welding wire 34 via the welding tip 31. The welding output generates an arc 36 between the welding wire 34 and the base material 35, thereby performing welding.

[0032] [Arc welding method] FIG. 2 is a time chart of various output waveforms when the set voltage is a unified voltage.

[0033] 2, arc welding is performed with a welding period Tw as one cycle. The welding period Tw includes a short-circuit period Ts in which a short circuit state occurs and an arc period Ta in which an arc state occurs. That is, in the example shown in this embodiment, arc welding is performed using arc welding device 40 so that the short-circuit period Ts in which a short circuit state occurs and the arc period Ta in which an arc state occurs alternately.

[0034] In this specification, the term "set voltage" refers to the average voltage of the welding voltage in the welding section when welding base material 35, and the term "set current" refers to the average current of the welding current in the welding section. The term "unitary voltage" refers to a voltage value set for the set current so that arc 36 has an appropriate arc length. Usually, when the set current is set, the control unit 20 of welding power source 10 automatically sets the feed rate of welding wire 34 (hereinafter also referred to as wire feed rate). The unitary voltage is also automatically set by control unit 20 of welding power source 10 according to the wire feed rate, or more specifically, the value of the set current.

[0035] 2, the short circuit period Ts starts from time t1 when a short circuit is detected between the welding wire 34 and the base metal 35, and calculation of the integrated power value also starts. Strictly speaking, the integrated power value is calculated from the time point after time t1 when the control unit 20 starts to control the welding current so that the current increases at a predetermined current increasing rate (hereinafter referred to as the slope control start time).

[0036] When a short circuit is detected at time t1, the welding current is reduced to the initial current by adjusting the output of first switching unit 12. At this time, second switching unit 15 remains in the conductive state.

[0037] Thereafter, the control unit 20 adjusts the output of the first switching unit 12 so that the welding current increases at a predetermined current increase rate from the start point of the slope control. At this time, the control unit 20 controls the operation of the wire feeder 32 to feed the welding wire 34 in the reverse direction. Alternatively, the welding wire 34 may be fed in the reverse direction after a predetermined time has elapsed since the short circuit occurred, in other words, after the short circuit state has stabilized. By feeding the welding wire 34 in the reverse direction during the short circuit period Ts, it is possible to promote release of the short circuit between the welding wire 34 and the base metal 35. Furthermore, controlling the forward and reverse feeding of the welding wire 34 by periodically switching between the forward and reverse feeding modes in particular stabilizes droplet formation at the tip end of the welding wire 34 and improves the stability of droplet transfer from the welding wire 34 to the base metal 35. Note that the forward and reverse feeding control of the welding wire 34 does not necessarily have to be performed. For example, the welding wire 34 may be fed at a constant speed without reverse feeding.

[0038] The calculation unit 21 calculates the integrated power value by integrating the power from the start point of the slope control described above.

[0039] The control unit 20 determines whether the integrated power value is greater than the first threshold value P1. In the example shown in Fig. 2, the integrated power value is greater than the first threshold value P1 at time point t2. When the integrated power value exceeds the first threshold value P1, that is, at time point t2 shown in Fig. 2, the control unit 20 switches the second switching unit 15 from the conductive state to the non-conductive state, thereby reducing the welding current supplied to the welding wire 34.

[0040] Just before time t3 following time t3, release of the short circuit between welding wire 34 and base metal 35 is detected. Control unit 20 adjusts the output of first switching unit 12 so that the welding current becomes a predetermined current. At this time, second switching unit 15 remains in the conductive state. Then, at time t3, the short circuit is released and a transition to arc period Ta occurs.

[0041] The integrated power value is calculated during the period from the start of slope control to time t2 when the integrated power value exceeds the first threshold value P1. The calculation of the integrated power value is not performed from time t2 to the start of the next slope control. For the above reasons, in Figures 2 to 4, the integrated power value is shown as the value at time t2, which in this case is a constant value, during the period from time t2 to the start of the next slope control.

[0042] Next, when a short circuit between the welding wire 34 and the base material 35 is detected, the arc period Ta ends and the short circuit period Ts begins. When the next slope control starts, the integrated power value is reset and the integration of power starts again from zero.

[0043] When the set voltage is V1 and the unitary voltage is V0, the differential voltage Vd is expressed by the relationship shown in equation (1).

[0044] Vd = V1 - V0 (1) That is, in the example shown in FIG. 2, the set voltage V1 is the same as the unitary voltage V0, and the differential voltage Vd is zero.

[0045] Now, consider the case where the set voltage V1 is changed independently without changing the set current. By changing the set voltage V1, for example, it is possible to change the arc length of the arc 36. Furthermore, by making the set voltage V1 higher than the unitary voltage V0, it is possible to adjust the penetration of the base material 35 to be deeper.

[0046] First, consider the case where the set voltage V1 is higher than the unitary voltage V0, that is, Vd > 0. Figure 3 is a time chart of various output waveforms when the set voltage is increased by 2 V from the unitary voltage.

[0047] As shown in Fig. 3, by setting the set voltage V1 higher than the unitary voltage V0, the short-circuit period Ts is shortened compared to the example shown in Fig. 2. In this case, if the timing for reducing the welding current is the same as the example shown in Fig. 2, there will be a period in which a large welding current continues to flow even after the short circuit is released, which may result in the generation of a large amount of spatter.

[0048] Therefore, in the example shown in Fig. 3, a second threshold value P2 smaller than the first threshold value P1 shown in Fig. 2 is set as the threshold value for the integrated power value. When the integrated power value exceeds the second threshold value P2, that is, at time t21 shown in Fig. 3, the control unit 20 switches the second switching unit 15 from the conductive state to the non-conductive state, thereby reducing the welding current supplied to the welding wire 34. In this way, the timing for reducing the welding current can be advanced, the period during which a large welding current flows after the short circuit is released can be shortened, and the generation of spatter can be suppressed.

[0049] Furthermore, the second threshold value P2 satisfies the relationship shown in equation (2). In this case, V1>V0.

[0050] P2=P1-{(P1×Vd×K1)×(J1 / 100)} =P1-{(P1×(V1-V0)×K1)×(J1 / 100)} ···(2) Here, K1 is a positive coefficient, and J1 is a coefficient that satisfies 0≦J1≦100. J1 changes depending on the set current, and the higher the set current, the larger the value becomes.

[0051] Furthermore, as is clear from equation (2), the second threshold value P2 decreases as the differential voltage Vd increases.

[0052] Next, consider the case where the set voltage V1 is lower than the unitary voltage V0, that is, Vd<0. Figure 4 is a time chart of various output waveforms when the set voltage is reduced by 2 V from the unitary voltage.

[0053] As shown in FIG. 4, by setting the set voltage V1 lower than the unitary voltage V0, the short-circuit period Ts becomes longer than in the example shown in FIG. 2. In this case, if the timing for reducing the welding current is the same as in the example shown in FIG. 2, the welding current will decrease before the short circuit is released, and the output for melting the welding wire 34 will be reduced. As a result, the welding wire 34 will not melt and will tend to plunge into the base material 35. As a result, a large amount of spatter will be generated.

[0054] Therefore, in the example shown in Fig. 4, a third threshold value P3 that is greater than the first threshold value P1 shown in Fig. 2 is set as the threshold for the integrated power value. When the integrated power value exceeds the third threshold value P3, that is, at time t22 shown in Fig. 4, the control unit 20 switches the second switching unit 15 from the conductive state to the non-conductive state, thereby reducing the welding current supplied to the welding wire 34. In this way, the timing for reducing the welding current is delayed, and it is possible to prevent the welding current from decreasing before the short circuit is released, and to prevent the welding wire 34 from plunging into the base material 35 and causing spatter.

[0055] Furthermore, the third threshold P3 satisfies the relationship shown in equation (3). <V0である。

[0056] P3=P1-{(P1×Vd×K2}×(J2 / 100)} =P1-{(P1×(V1-V0)×K2}×(J2 / 100)}···(3) Here, K2 is a positive coefficient, and J2 is a coefficient that satisfies 0≦J2≦100. Note that J2 changes depending on the set current, and the higher the set current, the larger the value becomes.

[0057] Furthermore, as is clear from equation (3), the third threshold P3 increases as the differential voltage Vd decreases, in other words, as the absolute value of the differential voltage Vd increases.

[0058] To perform the above-described arc welding method, an arc welding control program stored in the memory of control unit 20 is read by the CPU. In addition, a set current and a set voltage V1 input from setting unit 22 are set in the arc welding control program. Control unit 20 controls the operations of first switching unit 12, second switching unit 15, and wire feeder 32 in accordance with the arc welding control program into which each condition has been input.

[0059] [Effects, etc.] As described above, the arc welding method according to this embodiment is a consumable electrode arc welding method. That is, the base metal 35 is arc-welded by alternately repeating a short circuit period Ts in which a short circuit state occurs where the welding wire 34 and the base metal 35 are short-circuited and an arc period Ta in which an arc occurs between the welding wire 34 and the base metal 35.

[0060] The arc welding method includes a step of calculating an integrated power value by integrating the power supplied to the welding wire 34 after detecting a short circuit in the welding wire 34, and a step of reducing the welding current supplied to the welding wire 34 when the integrated power value exceeds a predetermined threshold value. This threshold value is changed according to the set voltage V1.

[0061] According to this embodiment, in consumable electrode arc welding, when the set voltage V1 is changed while the set current is kept at a predetermined value, spatter can be reduced.

[0062] When the set voltage V1 is the unitary voltage V0, the threshold is a preset first threshold P1. When the set voltage V1 is greater than the unitary voltage V0, the threshold is changed to a second threshold P2 that is smaller than the first threshold P1. When the set voltage V1 is smaller than the unitary voltage V0, the threshold is changed to a third threshold P3 that is larger than the first threshold P1.

[0063] When set voltage V1 is greater than unitary voltage V0, short circuit period Ts is shortened, and therefore the timing for reducing the welding current is advanced, thereby shortening the period during which a large welding current flows after the short circuit is released, and thereby suppressing the generation of spatter. Also, when set voltage V1 is less than unitary voltage V0, short circuit period Ts is lengthened, and therefore the timing for reducing the welding current is delayed, preventing the welding current from decreasing before the short circuit is released, and suppressing the welding wire 34 from plunging into base material 35 and causing spatter.

[0064] When the differential voltage Vd between the set voltage V1 and the reference voltage V0 is a positive value, it is preferable that the second threshold value P2 decreases as the differential voltage Vd increases. Also, when the differential voltage Vd is a negative value, it is preferable that the third threshold value P3 increases as the differential voltage Vd decreases, that is, as the absolute value of the differential voltage Vd increases.

[0065] When the differential voltage Vd is a positive value, as the differential voltage Vd increases, the short - circuit period Ts becomes shorter. Therefore, by decreasing the second threshold value P2 as the differential voltage Vd increases, the timing for reducing the welding current can be made appropriate, and the generation of spatter can be suppressed.

[0066] Also, when the differential voltage Vd is a negative value, as the differential voltage Vd decreases, the short - circuit period Ts becomes longer. Therefore, by increasing the third threshold value P3 as the differential voltage Vd decreases, the timing for reducing the welding current can be made appropriate, and the generation of spatter can be suppressed.

[0067] It is preferable that the second threshold value P2 satisfies the relationship shown in Equation (2) and V1 > V0, and the third threshold value P3 satisfies the relationship shown in Equation (3) and V1 < V0.

[0068] P2 = P1 - {(P1×Vd×K1}×(J1 / 100)} = P1 - {(P1×(V1 - V0)×K1}×(J1 / 100)} ···(2) [[ID=2))P3 = P1 - {(P1×Vd×K2}×(J2 / 100)} = P1 - {(P1×(V1 - V0)×K2}×(J2 / 100)}···(3) Here, K1 and K2 are positive coefficients, and J1 and J2 are coefficients that satisfy 0≦(J1, J2)≦100. Note that J1 and J2 change according to the set current, and the higher the set current, the larger the values.

[0069] In this way, the second threshold value P2 and the third threshold value P3 can be simply and appropriately set based on the first threshold value P1 and the differential voltage Vd, so that even when the set voltage is changed while the set current is kept at a predetermined value, the timing for reducing the welding current can be set to an appropriate timing, thereby suppressing the generation of spatter.

[0070] The arc welding control program according to this embodiment causes one or more CPUs (processors) to execute the above-described arc welding method.

[0071] By programming the control procedure for arc welding in this way, the timing for reducing the welding current can be set to an appropriate timing, thereby suppressing the generation of spatter. [Industrial Applicability]

[0072] The arc welding method of the present disclosure is useful in consumable electrode arc welding because it can reduce spatter when the set voltage is changed while the set current is kept at a predetermined value. [Explanation of symbols]

[0073] 10 Welding power source 11 1st rectifier 12 First Switching Section 13. Transformer 14 2nd rectifier 15 Second Switching Section 16 Resistance 17 Reactor 18 Welding current detector 19 Welding voltage detector 20 Control Unit 21 Calculation section 22 Setting section 30 Welding Torch 31 Welding Tip 32 Wire feeder 34 Welding wire 35 Base material 36 Arc 40 Arc welding equipment

Claims

1. A consumable electrode arc welding method for arc-welding a base metal by alternately repeating a short circuit period in which a short circuit state occurs in which a welding wire and a base metal are short-circuited and an arc period in which an arc state occurs between the welding wire and the base metal, calculating an integrated power value by integrating power supplied to the welding wire after a short circuit in the welding wire is detected; and reducing a welding current supplied to the welding wire when the integrated power value exceeds a predetermined threshold value, The arc welding method is characterized in that the threshold value is changed according to a set voltage.

2. The arc welding method according to claim 1, When the set voltage is a unitary voltage, the threshold is a first threshold set in advance; If the set voltage is greater than the unitary voltage, the threshold is changed to a second threshold which is smaller than the first threshold; When the set voltage is smaller than the unitary voltage, the threshold value is changed to a third threshold value that is larger than the first threshold value.

3. The arc welding method according to claim 2, When a differential voltage between the set voltage and the unitary voltage is a positive value, the second threshold value decreases as the differential voltage increases, An arc welding method, characterized in that, when the differential voltage is a negative value, the third threshold value increases as the differential voltage decreases.

4. The arc welding method according to claim 3, When the set voltage is V1, the unitary voltage is V0, the differential voltage is Vd, and the first threshold is P1, The second threshold value P2 satisfies the relationship shown in Equation (2) and V1>V0, The third threshold value P3 satisfies the relationship shown in Equation (3) and V1<V0, P2=P1-{(P1×Vd×K1}×(J1 / 100)} =P1-{(P1×(V1-V0)×K1}×(J1 / 100)}...(2) P3=P1-{(P1×Vd×K2}×(J2 / 100)} =P1-{(P1×(V1-V0)×K2}×(J2 / 100)}...(3) An arc welding method, wherein K1 and K2 are positive coefficients, and J1 and J2 are coefficients that satisfy 0≦(J1, J2)≦100.

5. 5. An arc welding control program for causing one or more processors to execute the arc welding method according to claim 1.

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