JP7509727B2 - Shield jig and gas shielded arc welding device - Google Patents

Description

The present invention relates to a shield jig and a gas shielded arc welding device.

Gas-shielded arc welding is known, in which a shielding gas (inert gas) is supplied to the weld to shield the weld from the air and prevent oxidation. A gas-shielded welding torch used in this type of gas-shielded arc welding is described, for example, in Patent Document 1.

The welding torch in Patent Document 1 has a configuration in which the shielding gas passage provided in the welding torch and the control gas passage that controls the cross-sectional shape of the weld bead are each independent passages, and the above-mentioned respective passages are arranged in a vertical row at positions symmetrical in the forward and backward directions of the welding, with the welding arc at the center. According to this, Patent Document 1 states that in narrow gap welding, the cross-sectional shape and penetration of the weld bead are improved by providing a front shielding gas passage and a rear shielding gas passage and controlling the gas flow rate.

Japanese Patent Application Laid-Open No. 1-48678

When gas-shielded arc welding is performed using a base material or filler metal (welding wire) made of an active metal, the affinity of the active metal with the atmosphere becomes particularly strong at high temperatures, and it is easy for the active metal to react with oxygen and nitrogen in the air to form oxides and nitrides. As a result, the hardening and weakening of the oxide and nitride-formed parts after welding becomes significant. Therefore, when gas-shielded arc welding of active metals is performed, an after-shield jig is generally used to prevent contact between the atmosphere and the active metal, and localized gas shielding is performed near the welding torch. However, when melting a filler metal such as pure titanium or a titanium alloy for additive manufacturing, it is still difficult to suppress the intrusion of oxygen and nitrogen into the molded body below the specified value just by using an after-shield jig.

For example, oxygen and nitrogen attached to other materials such as air and the base material are present ahead in the direction of welding, making it difficult to prevent these from being entrained. In addition, current shielding jigs only have a small shielding area that is covered by shielding gas, making it difficult to ensure gas shielding of the surrounding weld beads that become hot adjacent to the weld bead during welding during additive manufacturing. Furthermore, depending on the direction of welding, gas shielding may be insufficient, which could limit additive manufacturing using a manipulator.

The present invention aims to provide a shielding jig and gas-shielded arc welding device that can always ensure stable, wide-range gas shielding during gas-shielded arc welding.

The present invention comprises the following configurations.
(1) A shield jig that is attached to a welding torch for shield welding that melts and solidifies a metal filler metal to form a weld bead,
An annular member having a cylindrical outer circumferential surface, the annular member being provided radially outward of the welding torch;
an outer shell member disposed outside the outer circumferential surface of the annular member with a radial gap between the outer shell member and the annular member, the outer shell member defining an annular space having a lid portion at an upper portion and an opening at a bottom portion;
a gas supply member for supplying a shielding gas to the annular space;
Equipped with
In a cross section perpendicular to the axial direction of the welding torch, the cross-sectional area of the opening is smaller than the cross-sectional area of the annular member.
Shielding fixture.
(2) A gas shielded arc welding apparatus equipped with the shield jig described in (1).

The present invention ensures stable and wide-range gas shielding during gas-shielded arc welding.

FIG. 1 is a schematic diagram of a gas-shielded arc welding apparatus. FIG. 2 is a perspective view of a shield nozzle at the tip of a welding torch and a shield jig provided on the outer periphery of the shield nozzle. FIG. 3 is a schematic cross-sectional view showing the internal structure of the shield nozzle. FIG. 4 is a schematic cross-sectional view showing the internal structure of the shielding jig. FIG. 5 is a schematic cross-sectional view taken along line VV of the welding torch and the shield jig shown in FIG. FIG. 6 is an explanatory diagram that shows a schematic diagram of a welding torch during welding and a flow of shielding gas by a shield jig. FIG. 7 is a schematic perspective view showing a configuration in which a flow straightening section is provided in the annular space inside the outer shell member of the shield jig. FIG. 8 is an explanatory diagram showing the state of shielding gas sprayed from a shielding jig, in which (A) is a partial cross-sectional view of the bottom of the shielding jig, and (B) is a cross-sectional view of the formed gas curtain taken along line VIII-VIII shown in (A).

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
The shielding jig according to the present invention will be described here taking as an example a case in which a layered object is manufactured by gas shielded arc welding, but the present invention is not limited to this.

FIG. 1 is a schematic diagram of a gas-shielded arc welding apparatus.
The gas shielded arc welding apparatus 100, which is an apparatus for manufacturing an additive manufacturing object, includes a welding robot 11, a robot driving unit 13, a filler metal supply unit 15, a shielding gas supply unit 17, a welding power supply unit 19, and a control unit 21.

The welding robot 11 is an articulated robot, and a welding torch 23 is supported on the tip shaft. The position and posture of the welding torch 23 can be set arbitrarily in three dimensions within the range of the degrees of freedom of the robot arm. The welding torch 23 holds the filler material M, which is continuously supplied from the filler material supply unit 15, in a state where it protrudes from the tip of the welding torch.

The shielding gas supply unit 17 supplies an inert gas to the welded area. In MIG welding, argon, helium (or a mixture of these), or a gas with a small amount of an active gas such as oxygen or carbon dioxide added, is used as the shielding gas. On the other hand, in MAG welding, carbon dioxide gas or a mixture of argon and carbon dioxide gas is used as the shielding gas, and in TIG welding, argon gas is used. Furthermore, in laser welding, nitrogen, argon, helium, etc. are used as the shielding gas.

The welding torch 23 is a welding torch for shielded welding that melts and solidifies a metal filler material M to form a weld bead. Specifically, the welding torch 23 has a shield nozzle 25 that receives shielding gas supplied from the shielding gas supply unit 17 (see Figures 2 and 3), and the shielding gas is supplied to the weld from the shield nozzle 25. The arc welding method may be either a consumable electrode type such as shielded metal arc welding or carbon dioxide gas arc welding, or a non-consumable electrode type such as TIG welding or plasma arc welding, and is appropriately selected depending on the additive manufacturing product to be produced.

The heat source for melting the filler material M is not limited to the arc described above. For example, other heat sources may be used, such as a heating method that combines an arc and a laser, a heating method that uses plasma, or a heating method that uses an electron beam or laser. When heating with an electron beam or laser, the amount of heat can be controlled more precisely, and the state of the weld bead can be more appropriately maintained, contributing to further improving the quality of the additive manufacturing product.

The filler metal is, for example, a welding wire made of pure titanium or a titanium alloy for welding titanium and titanium alloys (see, for example, JIS Z 3331). If the filler metal is pure titanium or a titanium alloy, appropriate welding can be performed even if the welding base metal is a titanium-based material. Note that the filler metal is not limited to the above materials and may be other materials.

A shielding jig 31 is attached to the outer periphery of the welding torch 23. The shielding jig 31 receives shielding gas from the shielding gas supply unit 17 and sprays the shielding gas toward the weld. Details of the shielding jig 31 will be described later.

The robot driving unit 13 receives instructions from the control unit 21 to drive each part of the welding robot 11 and control the output of the welding power source as necessary.

The control unit 21 is configured with a computer device equipped with a CPU, memory, storage, etc., and executes a drive program prepared in advance or a drive program created under desired conditions to drive each part such as the welding robot 11. As a result, the welding torch 23 moves according to the drive program, and multiple layers of weld beads B are stacked on the base plate 29, thereby forming a multi-layered laminated object.

FIG. 2 is a perspective view of the shield nozzle 25 at the tip of the welding torch 23 and a shield jig 31 provided on the outer periphery of the shield nozzle 25 .
As described above, the shielding gas supply unit 17 supplies shielding gas to both the welding torch 23 and the shielding jig 31. The shielding nozzle 25 of the welding torch 23 projects the filler material M at the nozzle tip, and sprays the shielding gas G1 supplied from the shielding gas supply unit 17 toward the welded portion below.

FIG. 3 is a schematic cross-sectional view showing the internal structure of the shield nozzle 25. As shown in FIG.
The shield nozzle 25 shown here is of a consumable electrode type. A contact tip 27 is disposed inside the shield nozzle 25, and a filler material M to which a melting current is supplied is held by the contact tip 27. The welding torch 23 generates an arc from the tip of the filler material M in a shielding gas atmosphere while holding the filler material M. The filler material M is fed to the welding torch 23 by a feed mechanism (not shown) attached to a part of the welding robot 11 shown in FIG. 1. As the welding torch 23 moves, the continuously fed filler material M is melted and solidified, and a weld bead B, which is a molten solidified body of the filler material M, is formed on the base plate 29. At this time, the shield gas G1 supplied from the shield gas supply unit 17 is sprayed from the welding torch 23 through an internal space S1 defined inside the shield nozzle 25 to shield the filler material M.

A gas supply pipe 33 is connected to the shielding jig 31 shown in FIG. 2. The tip of the gas supply pipe 33 penetrates the top surface of the shielding jig 31 and is inserted into the jig, and is connected to an annular hollow pipe 35. The hollow pipe 35 is disposed above an annular space S2 having an opening 37 at the bottom inside the jig, and has multiple injection ports 35a formed at equal intervals around its entire circumference. The shielding gas supplied from the gas supply pipe 33 is injected upward from the injection ports 35a of the hollow pipe 35, and then injected downward from the opening 37 of the annular space S2.

FIG. 4 is a schematic cross-sectional view showing the internal structure of the shielding jig 31. As shown in FIG.
The shield jig 31 is provided on the outer periphery of the shield nozzle 25 provided at the tip of the welding torch 23 , and comprises an annular member 39 , an outer shell member 41 , and a gas supply member 43 consisting of a gas supply pipe 33 and a hollow pipe 35 .

The annular member 39 is provided radially outside the shield nozzle 25 of the welding torch 23, and includes an outer housing 39a and a heat insulating member 39b filled inside the outer housing 39a. The outer housing 39a has an annular plate portion 39a1 into whose center the shield nozzle 25 is inserted, and a cylindrical plate portion 39a2 connected to the outer periphery of the annular plate portion 39a1 and having a cylindrical outer periphery. The annular member 39 and the shield nozzle 25 are fixed by an appropriate method such as welding, screwing, or a clamping mechanism.

The insulating member 39b is made of an insulating material such as glass wool, stainless steel, or ceramics, but the material is not particularly limited. The annular member 39 may be made of an integral solid member whose material itself has insulating properties, in addition to being configured with the outer housing 39a and the insulating member 39b arranged separately. Because the annular member 39 includes the insulating member 39b, it is possible to prevent the heat generated by welding from reaching the surrounding members.

The outer shell member 41 is disposed outside the cylindrical plate portion 39a2 of the annular member 39 with a radial gap between it and the annular member 39. The outer shell member 41 has a lid portion 41a at the top and an opening 37 at the bottom. This defines an annular space S2 that covers the outside of the annular member 39. The outer shell member 41 may be formed integrally from sheet metal, or may be formed by cutting a solid body, etc.

In the shield jig 31 of this configuration, a narrowed portion 45 is formed at the bottom of the outer shell member 41, the cross-sectional area of which gradually decreases along the axial direction of the welding torch 23. In conjunction with the formation of this narrowed portion 45, a corresponding narrowed portion 47 is also formed at the bottom of the annular member 39. The radial gap between the narrowed portion 45 and the narrowed portion 47 is constant along the circumferential direction and is set equal to the size of the radial gap other than the bottom, which is (d2-d1)/2. The shield jig 31 may be formed as a straight cylinder without the narrowed portions 45, 47.

The hollow pipe 35 constituting the gas supply member 43 supplies the shielding gas supplied from the shielding gas supply unit 17 to the annular space S2 from the upward nozzle 35a. The shielding gas sprayed from the nozzle 35a is stirred above the hollow pipe 35 in the annular space S2, and then flows downward from the hollow pipe 35. The shielding gas then flows uniformly in the circumferential direction in the annular space S2, and heads toward the opening 37 formed on the bottom surface of the annular space S2. Note that if the shielding gas can be supplied to the annular space S2 evenly in the circumferential direction, the hollow pipe 35 may be omitted.

The opening 37, which serves as the outlet for the shielding gas from the shielding jig 31, has a continuous annular shape in the circumferential direction. Therefore, the shielding gas G2 sprayed downward from the opening 37 forms a cylindrical gas flow (hereinafter also referred to as a gas curtain). The opening 37 has an annular shape formed along the circumferential direction, but the shape of the opening 37 is not particularly limited. For example, the opening 37 may be divided by multiple slits along the circumferential direction, and the slits may be used to taper the flow of the shielding gas, thereby further improving the flow rate of the shielding gas.

Next, the dimensional characteristics of the shielding jig 31 will be described.
In the shielding jig 31 of this configuration, the relative sizes of the annular member 39 and the outer shell member 41 are designed to satisfy the following relationship.
FIG. 5 is a schematic cross-sectional view of the welding torch 23 and the shield jig 31 taken along line VV shown in FIG.
As shown in FIG. 5, in a cross section perpendicular to the axial direction of the welding torch 23, when the cross-sectional area of the annular space S2 is As and the cross-sectional area of the annular member 39 is Ak, the following formula (1) is established.
A>A... (1)
The relationship of formula (1) is satisfied at any height position of the welding torch 23.

Specifically, as shown in FIG. 4, when the outer diameter of the welding torch 23 (shield nozzle 25) is _d0 , the outer diameter of the annular member 39 is _d1 , and the inner diameter of the outer shell member 41 is _d2 , the following equations (2) and (3) hold.
d ₁ −d ₀ >d ₂ −d ₁ ... (2)
d ₀ >d ₂ -d ₁ ... (3)

The shielding gas supply source in this configuration is a single shielding gas supply unit 17 shown in FIG. 2. Therefore, the shielding gas supply unit 17 supplies shielding gas to the welding torch 23 and the shielding jig 31 at the same gas supply pressure. The shielding gas supply unit 17 sets the supply of shielding gas to the welding torch 23 at a constant supply pressure so that the supply of shielding gas G1 from the welding torch 23 is stably maintained at a constant specified amount. Therefore, the shielding jig 31 sprays shielding gas G2 under the same gas supply pressure as the gas supply pressure of the welding torch 23, so the smaller the cross-sectional area As of the annular space S2, the faster the flow rate of the shielding gas.

FIG. 6 is an explanatory diagram that shows a schematic diagram of the welding torch 23 during welding and the flow of shielding gas by the shield jig 31. As shown in FIG.
The welding torch 23 moves to stack multiple layers of weld beads B on the base plate 29, thereby forming a multi-layered laminated object W. At this time, a shielding gas G1 is sprayed from the shield nozzle 25 at the tip of the welding torch 23. The shielding jig 31 also sprays the shielding gas G2 supplied to the annular space S2 in an annular manner from the opening 37 toward the welded portion (the tip side of the welding torch 23).

When the shielding jig 31 satisfies the above formulas (2) and (3), the shielding gas G2 sprayed from the opening 37 forms an annular gas curtain. The shielding gas G2 also confines the shielding gas G1 sprayed from the welding torch 23 inside the formed gas curtain, and blocks the inflow of air Air from the outside. This promotes the retention of the shielding gas G1 sprayed from the welding torch 23, enhancing the gas shielding effect at the welded portion. As a result, the weld bead B during welding is effectively isolated from the outside air, oxygen attached to other members, nitrogen, etc., and intrusion into the layered object W can be suppressed.

On the other hand, if the shielding jig 31 does not satisfy the above-mentioned formulas (2) and (3) and the cross-sectional area As of the annular space S2 is larger than the cross-sectional area Ak of the annular member 39, the shielding gas will not continue to stagnate, and a large flow rate of shielding gas will be required to improve the shielding performance.
However, the shielding jig 31 of this configuration can obtain reliable shielding performance even with a small amount of gas by using the gas curtain of the shielding gas G2 and the shielding gas G2 supplied into the gas curtain. As a result, a wide-area gas shielding effect can be obtained while suppressing the consumption of the shielding gas.

Furthermore, in the shielding jig 31 of this configuration, narrowed portions 45, 47 are formed at the bottom between the outer shell member 41 and the annular member 39, so that the direction in which the shielding gas G2 is sprayed from the shielding jig 31 approaches the welding torch 23. As a result, the position where the shielding gas G1 from the welding torch 23 hits the welded portion and the position where the shielding gas G2 from the shielding jig 31 hits the welded portion are closer to each other, which is expected to enhance the retention effect of the shielding gas.

Next, a modified example of the shielding jig 31 will be described.
7 is a schematic perspective view showing a configuration in which a flow straightening section 48 is provided in the annular space S2 inside the outer shell member 41 of the shield jig. In FIG. 7, only the lower portion of the gas supply member is shown.

The modified shielding jig 31A has the same configuration as the shielding jig 31 described above, except that a straightening section 48 is provided in the annular space S2 inside the outer shell member 41. The straightening section 48 makes the flow of the shielding gas G2 in the annular space S2 spiral. The straightening section 48 can be formed, for example, by arranging multiple fins 49 between the outer peripheral surface of the annular member 39 (cylindrical plate section 39a2) and the inner peripheral surface of the outer shell member 41. The fins 49 are arranged at equal intervals along the circumferential direction to define multiple rows of spiral gas flow paths 51. The shielding gas G2 flowing through each gas flow path 51 has its flow direction regulated by the fins 49, and is sprayed from the opening 37 as a spiral airflow. This forms a circular gas curtain.

The flow straightening section 48 is formed of fins 49, but is not limited to this. For example, a spiral hole or groove like rifling may be formed on the outer peripheral surface of the annular member 39 or the inner peripheral surface of the outer shell member 41. The flow straightening section 48 may also be configured such that multiple injection nozzles that inject shielding gas are arranged at the bottom of the annular space S2 with the injection direction tilted circumferentially.

Figure 8 is an explanatory diagram showing the state of the shielding gas G2 being sprayed from the shielding jig 31A, where (A) is a partial cross-sectional view of the bottom of the shielding jig 31A, and (B) is a cross-sectional view of the formed gas curtain along line VIII-VIII shown in (A).

As shown in FIG. 8A, the shielding gas G2 sprayed from the opening 37 of the annular space S2 forms a gas curtain CT that has a spiral flow due to the flow straightening section 48 described above, and as shown in FIG. 8B, the cross section has a continuous circular ring shape.
The gas curtain CT with this spiral flow applies a rotational motion to the shielding gas, so that it is possible to more reliably prevent the inflow of air into the welded portion, and further improve the gas shielding effect of the welded portion. In addition, because the shielding gas is ejected while rotating, it is possible to prevent the entrainment of remaining air in the shielding gas piping.

In addition, fumes generated during welding may be sucked in by providing a separate suction path within the gas curtain.

The shielding jigs 31, 31A described above have a cylindrical shape centered on the welding torch 23, so that an annular gas curtain is formed centered on the welding torch 23. This provides a gas shielding effect for any movement direction of the welding torch 23, and does not restrict the trajectory of the welding torch 23. For example, compared to a before shield and an after shield that are provided according to the traveling direction of the welding torch 23, this reduces restrictions on the movement direction of the welding torch 23, allowing for welding with a high degree of freedom in construction.

As such, the present invention is not limited to the above-described embodiment, and it is intended that the various components of the embodiment be combined with each other, and that those skilled in the art may modify and apply the invention based on the description in the specification and well-known technology, and this is included in the scope of the protection sought.

As described above, the present specification discloses the following:
(1) A shield jig that is attached to a welding torch for shield welding that melts and solidifies a metal filler metal to form a weld bead,
An annular member having a cylindrical outer circumferential surface, the annular member being provided radially outward of the welding torch;
an outer shell member disposed outside the outer circumferential surface of the annular member with a radial gap between the outer shell member and the annular member, the outer shell member defining an annular space having a lid portion at an upper portion and an opening at a bottom portion;
a gas supply member for supplying a shielding gas to the annular space;
Equipped with
In a cross section perpendicular to the axial direction of the welding torch, the cross-sectional area of the opening is smaller than the cross-sectional area of the annular member.
Shielding fixture.
According to this shielding jig, the shielding gas injected from the annular space blocks the inflow of air from the outside and promotes the retention of the shielding gas injected from the welding torch, thereby enhancing the gas shielding effect. In addition, since the cross-sectional area of the annular space is smaller than the cross-sectional area of the annular member, it is possible to save shielding gas compared to a configuration in which the shielding gas is flowed over a wide area toward the weld.

(2) When the outer circumferential diameter of the welding torch is d ₀ , the outer circumferential diameter of the annular member is d ₁ , and the inner circumferential diameter of the outer shell member is d ₂ ,
d ₁ −d ₀ >d ₂ −d ₁
The shielding jig according to (1), wherein the following holds true.
With this shielding jig, the difference in radial length between the outer periphery of the annular member and the outer periphery of the welding torch is greater than the radial width of the annular space, so that the shielding gas can be sprayed from a position farther away from the welding torch than the radial width of the annular space, thereby allowing the shielding gas to remain in the space centered on the welding torch.

(3) _d0 > _d2 - _d1
The shielding jig according to (2), wherein the following holds true.
According to this shielding jig, the radial width of the annular space is smaller than the outer diameter of the welding torch, so that the flow velocity of the shielding gas ejected from the annular space can be increased, thereby improving the gas shielding effect.

(4) The shielding jig according to any one of (1) to (3), wherein a flow straightening section for making the flow direction of the shielding gas spiral is provided in the annular space.
This shielding jig can more reliably prevent air from entering the welded portion, and can further improve the gas shielding effect of the welded portion. In addition, because the shielding gas is ejected while rotating, it is possible to prevent the entrainment of air remaining in the shielding gas piping.

(5) The shielding jig according to any one of (1) to (4), wherein a narrowed portion is formed at a bottom of the outer shell member, the cross-sectional area of which gradually decreases along an axial direction of the welding torch.
With this shielding jig, the point where the shielding gas sprayed from the welding torch and the shielding gas sprayed from the annular space collide with each other is brought closer to the welding torch, further enhancing the retention effect of the shielding gas.

(6) The shielding jig according to any one of (1) to (5), wherein the annular member includes a heat insulating member.
This shielding jig can prevent the heat generated by welding from reaching the surrounding members.

(7) The shielding jig according to any one of (1) to (6), wherein the filler material is pure titanium or a titanium alloy.
This shielding jig makes it possible to perform high-quality welding even on welding base materials that are susceptible to the intrusion of oxygen and nitrogen.

(8) A gas shielded arc welding device comprising the shield jig according to any one of (1) to (7).
This gas-shielded arc welding apparatus provides high shielding properties and enables stable gas-shielded arc welding.

REFERENCE SIGNS LIST 11 Welding robot 13 Robot driving unit 15 Filler metal supply unit 17 Shielding gas supply unit 19 Welding power supply unit 21 Control unit 23 Welding torch 25 Shielding nozzle 27 Contact tip 29 Base plate 31 Shielding jig 33 Gas supply pipe 35 Hollow pipe 35a Jet nozzle 37 Opening 39 Annular member 39a Outer housing 39a1 Annular plate portion 39a2 Cylindrical plate portion 39b Heat insulating member 41 Outer shell member 43 Gas supply member 45, 47 Narrowed portion 48 Flow straightening portion 49 Fin 51 Gas flow path 100 Gas shielded arc welding device B Weld bead M Filler metal W Layered object

Claims (7)

A shield jig that is attached to a welding torch for shield welding in which a metal filler material is melted and solidified to form a weld bead,
An annular member having a cylindrical outer circumferential surface, the annular member being provided radially outward of the welding torch;
an outer shell member disposed outside the outer circumferential surface of the annular member with a radial gap between the outer shell member and the annular member, the outer shell member defining an annular space having a lid portion at an upper portion and an opening at a bottom portion;
a gas supply member for supplying a shielding gas to the annular space;
Equipped with
In a cross section perpendicular to the axial direction of the welding torch, a cross-sectional area of the opening is smaller than a cross-sectional area of the annular member;
A narrowed portion is formed at the bottom of the outer shell member, the cross-sectional area of which gradually decreases along the axial direction of the welding torch.
Shielding fixture. When the outer circumferential diameter of the welding torch is d ₀ , the outer circumferential diameter of the annular member is d ₁ , and the inner circumferential diameter of the outer shell member is d ₂ ,
d ₁ −d ₀ >d ₂ −d ₁
The shielding jig according to claim 1 , wherein the following expression is satisfied: d ₀ >d ₂ -d ₁
The shielding jig according to claim 2 , wherein the following expression is satisfied: The shielding jig according to any one of claims 1 to 3, wherein a flow straightening section is provided in the annular space to make the flow direction of the shielding gas spiral. The shielding jig according to claim 1 , wherein the annular member includes a heat insulating member. The shielding jig according to any one of claims 1 to 5 , wherein the filler material is pure titanium or a titanium alloy. A gas shielded arc welding device comprising the shield jig according to any one of claims 1 to 6 .

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