JP2020025965A - Arc welding method and arc welding equipment - Google Patents

Abstract

To provide an arc welding method that can suppress a spatter generation amount and stabilize welding, even when a welding-current is in a current range of 650-800A in GMA welding.SOLUTION: In a consumable electrode type arc welding method carried out by using a welding-current of 650-800 A, welding is performed by using carbon dioxide with a capacitance ratio of 10% or more and less than 17.5%, argon with a capacitance ratio of 82.5% or more and less than 90%, and triple shield gas having the remnant composed of helium.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an arc welding method and an arc welding device.

  In recent years, in order to improve welding efficiency, a high-efficiency GMA (Gas Metal Arc) welding technique for the purpose of achieving a high welding amount or a large leg length has been developed.

  GMA welding includes MIG welding using only an inert gas such as argon or helium as a shielding gas, and MAG welding using an active gas such as carbon dioxide or a mixed gas of an active gas and an inert gas such as argon. Among MAG welding, the case where only carbon dioxide is used is sometimes called carbon dioxide gas arc welding. It is generally known that, compared to carbon dioxide arc welding, GMA welding containing argon in the gas composition is easy to stabilize welding and provides good welding results, that is, good mechanical properties, bead appearance, and the like. I have.

  Patent Literature 1 and Patent Literature 2 disclose a technique for improving welding efficiency by adding helium to the shielding gas in GMA welding including argon and carbon dioxide as shielding gases.

Japanese Patent No. 5319595 JP 2013-046932 A

  However, in the techniques according to Patent Documents 1 and 2, the welding current is limited to 500 A or less. In order to further improve the welding efficiency, GMA welding technology at over 500 A is expected.

  Typical examples of GMA welding containing argon as a shielding gas include MAG welding using 80% argon-20% carbon dioxide and MIG welding using 100% argon. In particular, the former is generally used for welding steel materials. However, in MAG welding using 80% argon-20% carbon dioxide, the amount of spatters increases when the welding current is 650 A or more, and the welding becomes extremely unstable when the welding current is 700 A or more. The specific causes of instability are as follows.

For example, in the case of V-down fillet welding with a protrusion length of 35 mm, in a current range of less than 650 A, the droplet transfer mode is any of a drop transfer, a pendulum transfer, and a rotating transfer depending on the current, or a combination thereof. Among them, a plurality of transition modes can be mixed, but in any of the transition modes, welding is stable and there is no problem.
Pendulum transition, the liquid column and the arc formed at the tip of the welding wire, while swinging in a pendulum shape on the same plane, the plane rotates little by little with the projecting direction of the welding wire as the central axis. This is a characteristic droplet transfer mode.

  In the current range of 650 A or more and less than 700 A, a drop transition, a pendulum transition, and a rotating transition are mixed. In this current range, the length of the molten metal liquid column formed at the tip of the welding wire becomes long due to the high current, but when exhibiting the pendulum transition, this long liquid column swings greatly and reciprocates, causing the wire tip to reciprocate. The liquid column is blown out of the molten pool. As a result, although the welding stability is not extremely deteriorated, the amount of spatter generated is significantly increased.

  In the current region of 700 A or more and less than 800 A, the rotation transition is mainly performed, but the transition may be a pendulum transition or a drop transition. In this current range, if a drop transition or a pendulum transition is exhibited, a very strong arc force with a high current is concentrated in a specific direction, and as a result, the molten metal fluctuates and welding becomes unstable. In the drop transition, the arc concentrates downward, and in the pendulum transition, the arc concentrates in the reciprocating plane direction. In the case of a rotating transition, the arc force is dispersed in the rotating direction and rotates at a constant period, so that the force applied to the molten metal is dispersed, so that instability can be suppressed.

  In the current range of 800 A or more, the current becomes excessively large, causing a so-called pinch unstable state, and the droplet transfer mode is undefined. As a result, the arc phenomenon changes extremely in a short time, and the welding becomes unstable.

  In the above description, instability in MAG welding using 80% argon-20% carbon dioxide was mainly described. However, in MIG welding using 100% argon, when the welding current becomes 650 A or more, the welding becomes unstable. A similar problem occurs.

  The present invention has been made in view of such circumstances, and an object of the present invention is to suppress the amount of spatter generated and stabilize welding even when the welding current is in a current range of 650 A to 800 A in GMA welding. It is an object of the present invention to provide an arc welding method and an arc welding apparatus that can perform the method.

  In the arc welding method according to the present invention, the welding wire is supplied while supplying a welding gas while supplying a shielding gas to a portion to be welded of the base material, and a welding current of 650 A to 800 A is supplied to the welding wire. A consumable electrode type arc welding method for welding the base material by generating an arc between the tip portion and the portion to be welded, wherein the shielding gas has a capacity ratio of 10% or more and less than 17.5%. It is a mixed gas of three types consisting of carbon, argon having a capacity ratio of 82.5% or more and less than 90%, and the balance being helium.

  The arc welding apparatus according to the present invention supplies the welding wire while supplying a shielding gas to a portion to be welded of the base material, and supplies a welding current of 650 A to 800 A to the welding wire. An arc welding device of a consumable electrode type for generating an arc between the tip portion and the portion to be welded and welding the base material, wherein a volume ratio of carbon dioxide having a capacity ratio of 10% or more and less than 17.5% is obtained. A shield gas supply unit for supplying a shield gas of three or more of 82.5% or more and less than 90% of argon and a balance of helium to the portion to be welded is provided.

According to this aspect, in GMA welding performed in a current region where the welding current is 650 A or more and 800 A or less, carbon dioxide having a capacity ratio of 10% or more and less than 17.5%, and argon having a capacity ratio of 82.5% or more and less than 90%. By using a mixture of three types of shielding gas consisting of helium, the amount of spatter generated can be suppressed and welding can be stabilized (see FIGS. 2 to 4).
The above current range when the welding current fluctuates means that the average value of the welding current is 650A or more and 800A or less.

  The arc welding method according to the present invention supplies a DC welding current to the welding wire using a power supply having a constant voltage specification of −20 V / 100 A or more and −2 V / 100 A or less.

  According to this aspect, the arc length can be kept constant while the fluctuation of the welding current is suppressed, and the welding can be stabilized. When the external characteristic is on the constant voltage characteristic side from -2 V / 100 A, the welding current moves violently to make the arc length constant, and the welding becomes unstable. If the external characteristic is closer to the constant current characteristic side than -20 A / 100 V, it becomes difficult to keep the arc length constant.

  ADVANTAGE OF THE INVENTION According to this invention, even if the welding current in GMA welding is in the electric current range of 650 A or more and 800 A or less, the amount of spatters generated can be suppressed and welding can be stabilized.

It is a schematic diagram which shows the arc welding apparatus for implementing the arc welding method concerning this embodiment. FIG. 3 is a ternary diagram of gas components showing a relationship between welding stability and a gas mixture ratio at a welding current of 650 A. FIG. 3 is a ternary diagram of gas components showing a relationship between welding stability and a gas mixture ratio at a welding current of 800 A. FIG. 4 is a ternary diagram of gas components showing a mixture ratio capable of suppressing a spatter generation amount and stabilizing welding in a current region where a welding current is 650 A or more and 800 A or less.

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments.
<Arc welding equipment>
FIG. 1 is a schematic diagram showing an arc welding apparatus for performing the arc welding method according to the present embodiment. The arc welding apparatus according to the present embodiment is a consumable electrode type gas shielded arc welding machine capable of performing high current arc welding of at least 650 A to 800, and a welding robot to which a welding torch 11 and a wire feeding unit 12 are attached. 1, a welding power source 2, a control device 3, and a shielding gas supply unit 4. In FIG. 1, a thick line is a power supply cable L, a thin line is a control communication line, and a double line is a gas pipe 4a. The control device 3 controls the operations of the welding robot 1 and the welding power source 2 by outputting an operation control signal to the welding robot 1 and outputting a welding control signal to the welding power source 2 at a predetermined timing.

  The welding robot 1 includes a base 13 fixed to an appropriate location on the floor. A plurality of arms 14 are rotatably connected to the base 13 via a shaft. A welding torch 11 is held at a distal end portion of the arm 14 connected to the distal end side. A servo motor is provided at a connection portion of the arms 14, and each arm 14 rotates around a shaft portion by the rotational driving force of the servo motor. The rotation of the servomotor is controlled by the control device 3. The control device 3 can move the welding torch 11 up, down, front, back, left and right with respect to the base material 5 by rotating each arm 14. An encoder that outputs a signal indicating the rotational position of the arm 14 to the control device 3 is provided at a connection portion of each arm 14, and the control device 3 performs the welding torch 11 based on the signal output from the encoder. Recognize the position of. The control device 3 communicates with the welding power source 2 to control the supply of the welding wire W and the supply of the welding current.

The shielding gas supply unit 4 supplies a shielding gas to the welding torch 11. The shielding gas is for preventing the base material 5 and the welding wire W melted by the arc from being oxidized. The shielding gas is, for example, argon Ar, carbon dioxide CO ₂ and helium He.
It is a seed mixed gas. The flow rate of the shielding gas is preferably 40 L / min or more, more preferably 50 L / min or more. Various gases constituting the shielding gas may be mixed immediately before being supplied to the welding torch 11, or various gases may be mixed in advance and supplied to the welding torch 11 for a predetermined time, for example, several days. You may do it.

  The welding torch 11 is made of a conductive material such as a copper alloy, and has a cylindrical contact tip that guides the welding wire W to the welded portion 51 of the base material 5 and supplies a welding current necessary for generating an arc. . The contact tip contacts a welding wire W passing through the inside thereof and supplies a welding current to the welding wire W. Further, the welding torch 11 has a hollow cylindrical shape surrounding the contact tip, and has a nozzle for injecting the shielding gas supplied from the shielding gas supply unit 4 to the welded portion 51.

  The welding wire W is, for example, a solid wire, a metal cored wire, or a flux cored wire, and functions as a consumable electrode. The diameter of the welding wire W is 0.8 mm or more and 1.6 mm or less. The welding wire W is, for example, a pack wire stored in a pail pack in a spirally wound state, or a reel wire wound on a wire reel.

  The wire feeder 12 includes a feed roller that feeds the welding wire W to the welding torch 11, and a motor that rotates the feed roller. The wire feeding unit 12 draws out the welding wire W from the pail pack or the wire reel by rotating the feeding roller, and supplies the pulled out welding wire W to the welding torch 11 at a constant speed. The feeding speed of the welding wire W is, for example, about 5 to 100 m / min. The method of feeding the welding wire W is an example, and is not particularly limited.

  The welding power supply 2 is a power supply having a constant voltage characteristic, and includes a power supply circuit connected to a contact tip of the welding torch 11 and the base material 5 via a power supply cable L. The power supply circuit is a circuit that outputs a PWM-controlled direct current, and supplies a welding current by applying a welding voltage between the welding wire W and the base material 5. In particular, the welding power supply 2 according to the present embodiment supplies a welding current of 650 A or more and 800 A or less. The welding current is preferably a direct current or a direct current pulse, but is not particularly limited, and may be, for example, an alternating current or an alternating current pulse. 650 A when the welding current fluctuates means the average value of the welding current.

  According to the arc welding apparatus configured as described above, by supplying the welding wire W while supplying the shielding gas to the welded portion 51 of the base material 5 and supplying the welding current to the welding wire W, the welding is performed. The base material 5 can be welded by generating an arc between the distal end portion of the wire W and the portion 51 to be welded.

<Arc welding method>
The arc welding method according to the present embodiment stabilizes welding by stably maintaining the rotation transition in a current range of 650 A to 800 A. Specifically, it is a sealing gas composed of a mixed gas of three types of carbon dioxide, argon and helium, and its composition ratio is 10% or more and less than 17.5% by volume of carbon dioxide, and the volume ratio of argon is 82. By setting the helium: balance (%) to 5% or more and less than 90%, stabilization of welding is realized in the same manner.

  FIG. 2 is a ternary diagram of gas components showing the relationship between the welding stability and the gas mixture ratio when the welding current is 650 A, and FIG. 3 is a gas showing the relationship between the welding stability and the gas mixture ratio when the welding current is 800 A. FIG. 3 is a ternary diagram of components. 2 and 3 show the results of the experiment. The experimental conditions are as follows. The welding wire W has a protrusion length of 35 mm, V receiving down fillet welding, the shielding gas is a mixed gas of three types of carbon dioxide, argon and helium, the flow rate of the shielding gas is 50 L / min, and the welding wire W has a wire diameter of 1.4 mm. Solid wire, wire feeding speed is 34 m / min, and external characteristics are -10 V / 100 A DC welding current.

  The white circles indicate the composition ratio of the mixed gas in which the rotation transfer is stably maintained and the welding is stabilized. The black circles indicate the composition ratio of the mixed gas in which the rotation transfer is not stably maintained, the drop transfer and the pendulum transfer are performed, and the arc may be disturbed. The black triangles indicate the composition ratio of the mixed gas in which rotation transfer, pendulum transfer, and drop transfer are mixed and the welding result is good, but the amount of spatter generated is large. The X mark indicates the composition ratio of the mixed gas in which the droplet transfer mode becomes indefinite and the welding becomes unstable.

  As shown in FIG. 2, when the welding current is 650 A, the rotation transfer can be stably maintained in the region of the composition range A in which the composition ratio of carbon dioxide and helium is low and the composition ratio of argon is high, and the welding becomes stable. In the region of the composition range B where the composition ratio of carbon or He is high, the rotation transfer cannot be stably maintained, and the arc becomes unstable or the amount of spatters increases.

  As shown in FIG. 3, when the welding current is 800 A, in the composition range C, the transfer of the droplet becomes indefinite, the rotation transfer cannot be stably maintained, and the welding becomes unstable. In the range of the composition range D, rotation transfer cannot be stably maintained, and welding becomes unstable. In the region between the composition range C and the composition range D, and in the region of the composition range E where the composition ratio of carbon dioxide or helium is sufficiently large, the rotation transfer can be stably maintained, and the welding is stabilized.

FIG. 4 is a ternary diagram of gas components showing a mixture ratio capable of suppressing the amount of spatter generation and stabilizing welding in a current region where the welding current is 650 A or more and 800 A or less. FIG. 4 shows a composition range (hatched area) in which the composition range A in which the welding is stabilized shown in FIG. 2 and the composition range E in which the welding is stabilized shown in FIG. 3 are superimposed. . In FIG. 4, a part of the ternary diagram, the vicinity of an appropriate range of the composition ratio, is enlarged.
The composition range is a region where the welding current can be stabilized at both 650 A and 800 A. Even when the welding current is changed in the range of 650A to 800A, the welding is stabilized at least in the region.
More preferably, the volume ratio of argon is 82.5% or more and less than 90% and the volume ratio of carbon dioxide is 10% or more and less than 17.5, that is, the left oblique side indicating the composition ratio of argon, It is preferable to perform welding in a region surrounded by a two-dot chain line. One two-dot chain line indicates that the volume ratio of argon is 82.5%, and the other two-dot chain line indicates that the volume ratio of carbon dioxide is 10%. Since the area surrounded by the left oblique side and the two-dot chain line is included in the appropriate area with hatching, the welding is stable within the range.

<Details of welding conditions>
Hereinafter, details or modifications of the welding conditions will be described.
An appropriate protrusion length of the welding wire W is 20 mm to 45 mm. The protrusion length is the distance between the tip of the welding torch 11 and the surface of the base material 5. If the protruding length is less than 20 mm, the distance from the tip of the chip to the surface of the molten metal becomes short, and the molten metal contacts the contact tip due to disturbance, etc., or the arc generation point becomes too close to the tip of the chip, causing chip welding. Frequency and chip consumption rate. On the other hand, when the protrusion exceeds 45 mm, the nozzle of the welding torch 11 is too far from the tip of the welding wire W, so that a shield failure is likely to occur or a target deviation due to the bending of the welding wire W increases. In the V-receiving fillet welding, the above problem can be more effectively prevented particularly in the range of the protrusion of 25 mm to 40 mm.

The posture of the welding torch 11 is preferably downward. In the case of horizontal, vertical or upward welding, the molten metal drips because of the large amount of molten metal. However, there is no problem in the construction as long as the general advance angle, the sweep angle, and the target angle are up to 30 °. The target angle is a tilt angle of the welding torch 11 in a plane substantially perpendicular to the moving direction of the welding torch 11 moving along the welding line.
In addition, from the viewpoint of receiving a large amount of molten metal, the joint is preferably V-shaped fillet welding downward or butt-down welding inside a groove.

Further, it is known that when the rotation shifts by welding in a general so-called open arc, the molten metal detached from the distal end of the welding wire W becomes spatter and scatters to generate a large amount of spatter. However, if welding is performed so that the extension of the liquid column at the tip of the welding wire W falls within the bead width at the time of rotating transition, spatter can be absorbed by the weld bead and stable while preventing the generation of a large amount of spatter. Welding is feasible.
Further, in the high current MAG welding, a concave portion is formed in the molten metal on the base metal 5 side by a strong arc, but a semi-buried arc in which the tip of a liquid column formed on the welding wire W moves at a position deeper than the molten metal surface. (That is, the upper part of the arc is located above the surface of the molten metal), so that generation of spatter can be more effectively suppressed.
Further, it is more effective to form a buried arc in which the leading end portion enters a space surrounded by a concave molten portion formed in the base material 5 by the arc to weld the base material 5, that is, a completely buried arc. Sputtering can be suppressed.

  Further, the type of the welding wire W is not limited, but a solid wire or a metal-cored wire is preferable because the rotation transfer can be more stably maintained as compared with the flux cored wire. The metal cored wire is more preferable to be a solid wire because the rotation transfer may be prevented depending on the composition.

  Further, the diameter of the welding wire W is preferably 0.8 mm to 1.6 mm. However, since the transfer of droplets is likely to be uncertain with a thin wire, the diameter is preferably 1.2 mm to 1.6 mm, more preferably 1.4 mm to 1.6 mm. In addition, 1.4 mm is particularly desirable because the transition to the rotation does not easily occur with a large diameter wire.

  Furthermore, as the welding method, DC welding or DC pulse welding of general constant voltage characteristic control is desirable, but AC welding, AC pulse welding, or the like may be used. In pulse welding, the droplet transfer form is likely to be unstable at the time of peak current, and therefore DC welding with constant voltage characteristic control is more desirable. In this case, the external characteristics are desirably from -20 V / 100 A to -2 V / 100 A. When the external characteristic is on the constant voltage characteristic side from -2 V / 100 A, the welding current moves violently to make the arc length constant, and the welding becomes unstable. If the external characteristic is closer to the constant current characteristic side than -20 A / 100 V, it becomes difficult to keep the arc length constant.

<Example>
It has been confirmed that when GMA welding is performed under the following welding conditions, the rotation transfer can be stably maintained with the droplet transfer form being quasi-buried, and stable welding can be performed. The composition ratio of the shielding gas is 15% carbon dioxide-83% argon-2% helium, total gas flow rate 50L / min, welding current 800A, welding voltage 58V, protrusion length 35mm, V receiving downward welding, base material 5 thickness Stable welding can be performed by performing DC welding of a constant voltage external characteristic control of an external characteristic of −10 V / 100 A under a condition of a solid wire having a diameter of 25 mm and a wire diameter of 1.4 mm and a wire feeding speed of 34 m / min.

  As described above, according to the arc welding method and the arc welding apparatus according to the present embodiment, even when the welding current is in the current range of 650 A to 800 A in GMA welding, the amount of spatters generated is suppressed and the welding is stabilized. Can be done.

  Further, by setting the external characteristics of the welding power source 2 to be −20 V / 100 A or more and −2 V / 100 A or less, the arc length can be kept constant while the fluctuation of the welding current is suppressed, and the welding can be stabilized.

  Furthermore, by using a cored wire as the welding wire W, it is possible to easily maintain the rotation transition stably, and to further stabilize welding.

  In the above embodiment, the shielding gas containing argon, carbon dioxide and helium has been described, but another gas such as oxygen may be supplementarily added while maintaining the volume ratio of each gas.

  The embodiment disclosed this time is an example in all respects, and should be considered as non-limiting. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Welding robot 2 Welding power supply 3 Control device 4 Shield gas supply part 4a Gas pipe 5 Base material 51 Welded part 11 Welding torch 12 Wire feeding part 13 Base 14 Arm W Welding wire L Feeding cable

Claims (3)

By supplying the welding wire while supplying the shielding gas to the portion to be welded of the base material and supplying a welding current of 650 A to 800 A to the welding wire, a gap between the tip portion of the welding wire and the portion to be welded is provided. A consumable electrode type arc welding method of generating an arc to weld the base material,
An arc welding method, wherein the shielding gas is a mixed gas of three kinds consisting of carbon dioxide having a capacity ratio of 10% or more and less than 17.5%, argon having a capacity ratio of 82.5% or more and less than 90%, and the balance being helium. The arc welding method according to claim 1, wherein a DC welding current is supplied to the welding wire using a power supply having a constant voltage specification of -20V / 100A or more and -2V / 100A or less. By supplying the welding wire while supplying the shielding gas to the portion to be welded of the base material and supplying a welding current of 650 A to 800 A to the welding wire, a gap between the tip portion of the welding wire and the portion to be welded is provided. A consumable electrode type arc welding apparatus that generates an arc to weld the base material,
Shielding gas for supplying to the welded portion a mixture of three types of shielding gas consisting of carbon dioxide having a capacity ratio of 10% or more and less than 17.5%, argon having a capacity ratio of 82.5% or more and less than 90%, and a balance of helium. Arc welding equipment with a supply unit.