Arc welding method and arc welding device

Abstract

Provided is a consumable electrode-type arc welding method, in which welding is performed while supplying a welding current I between a workpiece W and a welding wire 13 to generate an arc A and supplying a shield gas S around the arc A. An arc length L defined by the position of a tip 13a of the welding wire 13 relative to a surface Wa of the workpiece W is within ±2 mm. The shield gas S is composed of 100% argon. The welding current I is composed of a pulse wave in which a base current IB and a peak current IP are periodically and alternately repeated. An average current IA per cycle T in the welding current I is 250 A or greater. The base current IB is 200 A or greater. The peak current IP is 600 A or less.

Description

Arc welding method and arc welding device

[0001] The present disclosure relates to a consumable electrode arc welding method and apparatus.

[0002] In arc welding, a welding current is generally supplied between the workpiece and the electrode to generate an arc, and a shielding gas, such as argon, is supplied around the arc while welding. The welding current is a pulse wave consisting of a base current and a peak current that are periodically alternated.

[0003] In arc welding, when deep penetration into the workpiece is desired, it is possible to simply increase the average current per cycle (set current) of the welding current, but simply increasing the average current can result in welding defects such as smut and puckering.

[0004] In the arc welding method disclosed in Patent Document 1, a mixture of argon and helium is used as the shielding gas.

[0005] Japanese Patent Application Laid-Open No. 2003-019564

[0006] In the arc welding method disclosed in Patent Document 1, helium is mixed with argon in the shielding gas, thereby suppressing welding defects such as smut and puckering, while increasing the concentration of the arc and achieving deep penetration.

[0007] However, in recent years, due to reasons such as the rising price of helium, it has become difficult to obtain helium, making it difficult to produce a shielding gas consisting of a mixture of argon and helium as shown in Patent Document 1.

[0008] Another method is to mix about 1% oxygen into the argon shielding gas, but this method causes the bead surface to oxidize and become black, or smut to adhere, damaging the bead appearance.

[0009] The present disclosure has been made in consideration of these points, and its purpose is to obtain deep penetration while suppressing welding defects, even when 100% argon is used as the shielding gas in arc welding.

[0010] The arc welding method according to the present disclosure is a consumable electrode arc welding method in which a welding current is supplied between a workpiece and an electrode which is a welding wire to generate an arc, and welding is performed while supplying a shielding gas around the arc, wherein the arc length, which is indicated by the relative position of the tip of the electrode with respect to the surface of the workpiece, is within ±2 mm, the shielding gas is composed of 100% argon, the welding current is composed of a pulse wave in which a base current and a peak current are periodically alternately repeated, and the average current per cycle of the welding current is 250 A or more, the base current is 200 A or more, and the peak current is 600 A or less.

[0011] The arc welding apparatus according to the present disclosure is a consumable electrode arc welding apparatus that supplies a welding current between a workpiece and an electrode that is a welding wire to generate an arc and performs welding while supplying a shielding gas around the arc, wherein the arc length, indicated by the relative position of the tip of the electrode with respect to the surface of the workpiece, is within ±2 mm, the shielding gas is composed of 100% argon, the welding current is composed of a pulse wave in which a base current and a peak current are periodically alternately repeated, and the average current per cycle of the welding current is 250 A or more, the base current is 200 A or more, and the peak current is 600 A or less.

[0012] According to the present disclosure, in arc welding, even when 100% argon is used as the shielding gas, deep penetration can be obtained while suppressing welding defects.

[0013] Fig. 1 shows an arc welding apparatus. Fig. 2 shows the arc length. Fig. 3 shows the penetration depth. Fig. 4 shows the change in welding current over time. Fig. 5 shows a first embodiment. Fig. 6 shows a second embodiment. Fig. 7 shows a third embodiment.

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 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] (Arc Welding Apparatus) An arc welding method will be described. The arc welding method is performed by an arc welding apparatus 1. The arc welding method and the arc welding apparatus 1 are of the consumable electrode type. FIG. 1 shows the arc welding apparatus 1.

[0016] The arc welding apparatus 1 performs an arc welding method. In the arc welding method, a welding current I is supplied between a workpiece W as an object to be welded and a welding wire 13 as an electrode to generate an arc A, and welding is performed while supplying a shielding gas S around the arc A. The workpiece W is metal. The electrode is the welding wire 13. In this example, the arc welding apparatus 1 performs MIG (Metal Inert Gas) welding.

[0017] An arc A is generated between the workpiece W and the welding wire 13. The welding wire (electrode wire) 13 is a metal filler used in arc welding. The welding wire 13 is held by a torch (not shown). As the torch moves at a predetermined speed, the welding wire 13 also moves at the same speed in the welding direction along a predetermined welding section.

[0018] The arc welding apparatus 1 includes a main transformer 2, a primary side rectifier 3, a switching unit 4, a DCL (reactor) 5, a secondary side rectifier 6, a welding current detector 7, a welding voltage detector 8, a control switching unit 9, an output controller 10, a wire feed speed controller 11, a welding tip 12, a welding wire 13, a nozzle 14, a wire feeder 16, and a welding condition setting unit 17. The arc welding apparatus 1 also includes a robot controller (not shown) that controls the operation of a robot (not shown) that holds a torch (not shown).

[0019] The primary side rectifier 3 rectifies the input voltage input from an input power source (three-phase AC power source) 15 external to the arc welding device 1. The switching unit 4 controls the output of the primary side rectifier 3 to an output suitable for welding. The main transformer 2 converts the output of the switching unit 4 into an output suitable for welding.

[0020] A secondary side rectifier 6 rectifies the output of the main transformer 2. A DCL (reactor) 5 smoothes the output of the secondary side rectifier 6 to a current suitable for welding. A welding current detector 7 detects a welding current I flowing through the welding wire 13. A welding voltage detector 8 detects a welding voltage applied between the welding wire 13 and the workpiece W.

[0021] The control switching unit 9, the output control unit 10, the wire feed speed control unit 11, and the welding condition setting unit 17 are each composed of one or more central processing units (CPUs) or one or more micro control units (MCUs), and are also referred to as controllers.

[0022] The control switching unit 9 outputs a signal for short-circuit welding control or pulse welding control to the output control unit 10 based on the determination by the welding voltage detection unit 8 of whether the welding voltage detection unit 8 is in a short-circuit state or an arc state.

[0023] The wire feeder 16 feeds the welding wire 13 toward the workpiece W. The wire feed speed controller 11 controls the feed speed of the welding wire 13. The welding condition setting unit 17 sets the welding conditions.

[0024] The output control unit 10 outputs a control signal to the switching unit 4 to control the welding output. The output control unit 10 controls the welding current I so that it becomes an average current IA. The output control unit 10 sets the welding current I to the average current IA. The average current IA is also called a set current. The average current IA is a moving average value of the welding current I over a predetermined period. Specifically, the average current IA is an average value per one period T of the pulsed welding current I described below.

[0025] The arc welding device 1 supplies a welding current I to a welding wire 13 via a welding tip 12. The arc welding device 1 supplies the welding current I between a workpiece W and the welding wire 13 to generate an arc A.

[0026] The nozzle 14 surrounds the welding tip 12. Shielding gas S supplied from a shielding gas supply unit (not shown) flows between the nozzle 14 and the welding tip 12 and is sprayed toward the workpiece W. This supplies the shielding gas S to the periphery of the arc A. As will be described in detail later, the shielding gas S is composed of 100% argon.

[0027] In this way, the arc welding apparatus 1 (arc welding method) supplies a welding current I between the workpiece W and the welding wire 13 to generate an arc A, and performs welding while supplying a shielding gas S around the arc A.

[0028] (Arc Length) Figure 2 shows the arc length L. The arc length L is the distance between both ends of the arc between the tip 13a of the welding wire 13 and the surface Wa of the workpiece W when arc welding is performed. In this example, the arc length L is indicated by the relative position of the tip 13a of the welding wire 13 with respect to the surface Wa of the workpiece W. The inside of the workpiece W with respect to the surface Wa of the workpiece W (the lower side in Figure 2, the side opposite the welding tip 12) is set to be negative, and the side opposite the inside of the workpiece W with respect to the surface Wa of the workpiece W (the upper side in Figure 2, the side toward the welding tip 12) is set to be positive.

[0029] When the arc length L is negative (see the thick two-dot chain line), buried arc welding is performed, in which the tip 13a of the welding wire 13 is embedded in (buried within) the workpiece W. When the arc length L is positive, welding is performed with the tip 13a of the welding wire 13 and the workpiece W spaced apart.

[0030] The workpiece W and the welding wire 13 are melted by the heat of the arc A, forming a molten pool Wb. The welding wire 13 is an electrode and is fed toward the workpiece W.

[0031] The arc length L is within ±2 mm relative to the surface Wa of the workpiece W.

[0032] The welding wire 13 moves at a moving speed V along the direction in which the surface Wa of the workpiece W extends.

[0033] 3 shows a widthwise cross section of the weld bead, showing the penetration depth (amount of penetration) U. The penetration depth U is indicated by the distance between the apex (bottom end) Wc1 of the fusion zone Wc, which is the portion of the workpiece W that has been melted by welding, and the surface Wa of the workpiece W. A weld bead Wd is formed on the surface Wa of the workpiece W so as to protrude upward.

[0034] (Welding Current) Figure 4 is a graph showing the change in welding current I over time. The horizontal axis represents time t [s]. The vertical axis represents welding current I [A]. The welding current I is composed of a pulse wave in which base current IB and peak current IP are periodically repeated alternately. The value of peak current IP is greater than the value of base current IB. In the welding current I, base current IB is the valley and peak current IP is the peak.

[0035] The base current IB may have a predetermined fluctuation range IBa, and the peak current IP may have a predetermined fluctuation range IPa.

[0036] As described above, the average current IA is the average value per period T of the pulsed welding current I. The period T [s] is the reciprocal of the frequency f [Hz] (T=1 / f).

[0037] The average current I can be kept constant by adjusting the difference in level between the base current IB and the peak current Ip and the frequency f. Specifically, to keep the average current I constant, the peak current Ip should be reduced when the base current IB increases, and the peak current Ip should be increased when the base current IB decreases. In some cases, it may be necessary to adjust the frequency f to keep the average current I constant.

[0038] (Welding Conditions) Welding conditions will be explained.

[0039] As described above, the arc length L is within ±2 mm with respect to the surface Wa of the workpiece W.

[0040] As described above, the shielding gas S is composed of 100% argon. The shielding gas S does not contain any elements other than argon (for example, helium, oxygen, carbon dioxide, etc.).

[0041] The average current IA is 250 A or more. The base current IB is 200 A or more. The peak current IP is 600 A or less.

[0042] When the average current IA is around 300 A (preferably when the average current IA is constant at 300 A), it is preferable that the base current IB be 200 A or more (preferably 220 A or more) and 300 A or less, and the peak current IP be 300 A or more and 500 A or less.

[0043] When the average current IA is around 400 A (preferably when the average current IA is constant at 400 A), it is preferable that the base current IB is 200 A or more and 400 A or less, and the peak current IP is 400 A or more and 600 A or less.

[0044] When the average current IA is around 500 A (preferably when the average current IA is constant at 500 A), it is preferable that the base current IB is 400 A or more and 500 A or less, and the peak current IP is 500 A or more and 600 A or less.

[0045] Smut here refers to fine metal oxides that are generated when part of a droplet evaporates from the tip of the welding wire 13 due to arc heat, moves out of the shielded area shielded by the shielding gas S, and then oxidizes and solidifies. Bucking is a phenomenon in which, when the shielding gas is ineffective, such as when the shielding gas moves out of the shielded area, air (outside air) is drawn in from the periphery of the molten pool, causing a thick, wrinkled oxide film to form on the surface of the weld bead, resulting in the formation of a defective bead that resembles elephant skin.

[0046] (First Example) A first example will be described below. Table 1 and Fig. 5 show the first example.

[0047] In the first embodiment, the average current IA is set to approximately 300 A. Specifically, in the first embodiment, the average current IA is set to a constant value of 300 A.

[0048] In the first example, the welding speed V (the speed at which the welding wire 13 moves in the direction in which the surface Wa of the workpiece W extends (welding direction), see FIG. 2 ) was set to 40 cm / min. The thickness of the workpiece W was set to 10 mm. The material of the workpiece W and the material of the welding wire 13 serving as the electrode were aluminum or an alloy containing aluminum as its main component. The torch advance angle (for a plate thickness of 8 mm or more and less than 12 mm) was set to 15°.

[0049] A pass was given when the arc length L was within ±2 mm of the surface Wa of the workpiece W, and a fail was given when the arc length L was greater than +2 mm or less than -2 mm. A pass was given when the penetration depth U was 50% or more of the plate thickness (10 mm x 0.5 = 5 mm or more in the first example), and a fail was given in all other cases. The appearance of the bead Wd was evaluated by visually inspecting it. In the visual inspection, a pass was given when no welding defects such as smut or puckering were visible, and a fail was given when these welding defects were visible.

[0050] As shown in Table 1 and FIG. 5, in the first example, good results were obtained under condition numbers A to C.

[0051] As shown in Fig. 5, the horizontal axis, which is one axis of a Cartesian coordinate system, represents the base current IB [A]. The vertical axis, which is the other axis of the Cartesian coordinate system, represents the peak current IP [A]. When good results are obtained, the base current IB and peak current IP (welding current I) belong to the region sandwiched between a first line L1 and a second line L2, which represent the relationship between the base current IB and the peak current IP.

[0052] In this example, the first line L1 and the second line L2 are linear lines. In the first line L1 and the second line L2, one of the base current IB and the peak current IP is a function of the other. In the first line L1 and the second line L2, the base current IB is a function of the peak current IP, and the peak current IP is a function of the base current IB.

[0053] The conditions under which good results were obtained in the first example were as follows, as shown in Figure 5: The base current IB was 220 A or more and 300 A or less. The peak current IP was 300 A or more and 500 A or less. The first line L1 is IP = -0.75 x IB + 525. The second line L2 is IP = -2.5 x IB + 1050.

[0054]

[0055] Second Example A second example will now be described. Table 2 and Fig. 6 show the second example.

[0056] In the second embodiment, the average current IA is set to approximately 400 A. Specifically, in the second embodiment, the average current IA is set to a constant value of 400 A.

[0057] In the second example, the welding speed V was 40 cm / min. The thickness of the workpiece W was 15 mm. The material of the workpiece W and the material of the welding wire 13 serving as the electrode were aluminum or an alloy containing aluminum as its main component. The torch advance angle (for a plate thickness of 12 mm or more and less than 18 mm) was 15°. A penetration depth U of 50% or more of the plate thickness (in the second example, 15 mm x 0.5 = 7.5 mm or more) was considered to be acceptable. The other conditions were the same as those in the first example.

[0058] As shown in Table 2 and FIG. 6, in the first example, good results were obtained under condition numbers A to G.

[0059] The conditions under which good results were obtained in the second example were as follows, as shown in Figure 6: The base current IB was 200 A or more and 400 A or less. The peak current IP was 400 A or more and 600 A or less. The first line L1 was IP = -IB + 800. The second line L2 was IP = -2 x IB + 1200.

[0060]

[0061] Third Example A third example will now be described. Table 3 and FIG.

[0062] In the third embodiment, the average current IA is set to approximately 500 A. Specifically, in the third embodiment, the average current IA is set to a constant value of 500 A.

[0063] In the third example, the welding speed V was 40 cm / min. The thickness of the workpiece W was 20 mm. The material of the workpiece W and the material of the welding wire 13 serving as the electrode were aluminum or an alloy containing aluminum as its main component. The torch advance angle (for a plate thickness of 18 mm or more and less than 25 mm) was 15°. A penetration depth U of 50% or more of the plate thickness (in the third example, 20 mm x 0.5 = 10 mm or more) was considered to be acceptable. Other conditions were the same as those in the first and second examples.

[0064] As shown in Table 3 and FIG. 7, in the third embodiment, good results were obtained under condition numbers A to D.

[0065] The conditions under which good results were obtained in the third example were as follows, as shown in Figure 7: The base current IB was 400 A or more and 500 A or less. The peak current IP was 500 A or more and 600 A or less. The first line L1 was IP = -IB + 1000. The second line L2 was IP = -5 x IB + 3000.

[0066]

[0067] (Effects) By setting the average current IA to a high current range of 250 A or more, the base current IB to 200 A or more, and the peak current IP to 600 A or less, it is possible to increase the penetration depth (penetration amount) U while suppressing welding defects.

[0068] By using 100% argon as the shielding gas S, the arc A can be constricted and the concentration of the arc A can be increased, which is advantageous in further increasing the penetration depth U.

[0069] If the arc length L is long, the shielding effect of the shielding gas S deteriorates, and external air is drawn into the arc A, causing welding defects such as puckering. Conversely, if the arc length L is short, the frequency of short circuits increases, and when the short circuit is released, the high current causes re-arcing, which causes the molten pool to vibrate, resulting in welding defects such as smut.

[0070] By keeping the arc length L within ±2 mm relative to the surface Wa of the workpiece W, it is possible to suppress the entrainment of outside air into the arc A due to the deterioration of shielding properties caused by the shielding gas S, and to suppress vibration of the molten pool, which is advantageous in suppressing welding defects such as puckering and smut.

[0071] As described above, in regard to arc welding, even when 100% argon is used as the shielding gas S, deep penetration can be obtained while suppressing welding defects.

[0072] Since helium is not used as the shielding gas S, it is advantageous in terms of cost.

[0073] In this embodiment, the average current IA is kept constant at a predetermined value, the base current IB and peak current IP are kept within predetermined ranges, and the base current IB and peak current IP (welding current I) are set to fall within the region between the first line L1 and the second line L2 (which represent the relationship between the base current IB and the peak current IP). This more effectively achieves both suppression of welding defects and deep penetration.

[0074] (Other Embodiments) Although the present disclosure has been described above with reference to preferred embodiments, such descriptions are not limiting, and it goes without saying that various modifications, substitutions, and combinations are possible.

[0075] The present disclosure is applicable to arc welding methods and arc welding apparatuses, and is therefore extremely useful and has high industrial applicability.

[0076] 1 Arc welding device 13 Welding wire (electrode) 13a Tip A Arc S Shielding gas W Work (object to be welded) Wa Surface L Arc length U Penetration depth I Welding current IA Average current IB Base current IP Peak current T Period L1 First line L2 Second line

Claims

1. A consumable electrode arc welding method in which a welding current is supplied between a workpiece and an electrode which is a welding wire to generate an arc and welding is performed while supplying shielding gas around the arc, wherein the arc length indicated by the relative position of the tip of the electrode to the surface of the workpiece is within ±2 mm, the shielding gas is composed of 100% argon, the welding current is composed of a pulse wave in which a base current and a peak current are periodically repeated alternately, the average current per cycle of the welding current is 250 A or more, the base current is 200 A or more, and the peak current is 600 A or less.

2. The arc welding method according to claim 1, wherein the base current is 200 A or more and 300 A or less, and the peak current is 300 A or more and 500 A or less.

3. The arc welding method according to claim 1, wherein the base current is 200 A or more and 400 A or less, and the peak current is 400 A or more and 600 A or less.

4. The arc welding method according to claim 1, wherein the base current is 400 A or more and 500 A or less, and the peak current is 500 A or more and 600 A or less.

5. The arc welding method according to claim 1, wherein, when IB is taken as the base current on one axis of a Cartesian coordinate system and IP is taken as the peak current on the other axis of the Cartesian coordinate system, IB as the base current and IP as the peak current belong to a region sandwiched between a first line and a second line which represent the relationship between IB as the base current and IP as the peak current.

6. The method of claim 1, wherein the average current is constant.

7. The arc welding method according to claim 5, wherein the base current is 220 A or more and 300 A or less, the peak current is 300 A or more and 500 A or less, the first straight line is IP = -0.75 x IB + 525, and the second straight line is IP = -2.5 x IB + 1050.

8. The arc welding method according to claim 2 or 7, wherein the average current is 300A.

9. The arc welding method according to claim 5, wherein the base current is 200 A or more and 400 A or less, the peak current is 400 A or more and 600 A or less, the first straight line is IP = -IB + 800, and the second straight line is IP = -2 x IB + 1200.

10. An arc welding method as claimed in claim 3 or 9, wherein the average current is 400A.

11. The arc welding method according to claim 5, wherein the base current is equal to or greater than 400 A and equal to or less than 500 A, the peak current is equal to or greater than 500 A and equal to or less than 600 A, the first straight line is IP = -IB + 1000, and the second straight line is IP = -5 x IB + 3000.

12. The arc welding method according to claim 4 or 11, wherein the average current is 500A.

13. A consumable electrode type arc welding device which supplies a welding current between a workpiece and an electrode which is a welding wire to generate an arc and performs welding while supplying a shielding gas around the arc, wherein the arc length indicated by the relative position of the tip of the electrode to the surface of the workpiece is within ±2 mm, the shielding gas is composed of 100% argon, the welding current is composed of a pulse wave in which a base current and a peak current are periodically repeated alternately, the average current per cycle of the welding current is 250 A or more, the base current is 200 A or more, and the peak current is 600 A or less.

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