JP2003311419A - Mig-welding method for stainless steel and tool for gas shield - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MIG welding method and a tool for gas shield with which in the case of performing the MIG welding to a stainless steel, oxidizing of a bead is prevented and the good welding can be performed. <P>SOLUTION: The MIG welding is performed by using the tool 10 for gas shield which has a bead shield part 1 provided with a top cover plate 1a and side walls 1b suspended from this periphery and a torch 2 having a shield gas supplying part 2b for supplying the shield gas into the bead shield part 1 and using the shield gas composed of 1-9 vol.% carbon dioxide gas concentration and the balance argon gas. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to stainless steel M.
The present invention relates to an IG welding method and a gas shield jig used for the method.

[0002]

2. Description of the Related Art In arc welding of stainless steel, it is required to prevent deterioration of mechanical properties and corrosion resistance of metal. Conventionally, in the MIG welding method using a solid wire in the arc welding method of stainless steel, for example, a shield gas obtained by adding 2% by volume of oxygen gas to argon gas has been used. This method enables welding with a small amount of slag, a small amount of carbon pickup, and a small amount of spatter. However, this method is unsuitable for welding a structure where appearance is important because the bead is heavily oxidized.

Therefore, for MIG welding of this kind of structure made of stainless steel, a flux cored wire, which is a slag type welding, in which flux is mixed, is used, and a shield gas of 100% by volume of carbon dioxide gas and argon are used. A shield gas in which 20% by volume of carbon dioxide gas is added to the gas is used. In MIG welding using a flux-cored wire, the slag covers the bead after welding, so that the bead is not oxidized and the appearance of the object to be welded can be improved. However, MI using flux-cored wire
In the G welding, there is a problem that it is necessary to remove the slag after welding, and the work is troublesome. Moreover, since the slag is scattered around the work, there is a problem in that it is not preferable for environmental protection.

[0004]

In order to prevent oxidation during arc welding, there is a method of shielding with an inert gas. However, in MIG welding, when shielding with only an inert gas, the generated arc is There is an inconvenience that good welding cannot be performed due to the influence of the shielding gas. The present invention has been made in view of the above circumstances, and provides a MIG welding method and a gas shield jig capable of preventing bead oxidation and performing good welding during MIG welding of stainless steel. With the goal.

[0005]

According to the MIG welding method of stainless steel of the present invention, a shield gas having a carbon dioxide gas concentration of 1% by volume or more and 9% by volume or less and a balance of argon gas is used. Characterize. MI of the present invention
In the G welding method, a shield gas having a carbon dioxide concentration of 1% by volume or more and 9% by volume or less and the balance of argon gas and helium gas can be used. In the MIG welding method of the present invention, the shielding gas can be supplied together with the arc and the molten pool so as to shield the bead after welding. In the present invention, the arc and the molten pool are shielded by using the first shield gas, and the bead portion after welding is shielded by using the mixed gas of the first shield gas and the second shield gas. The carbon dioxide concentration of the mixed gas supplied to the section can be 1% by volume or more and 9% by volume or less, and the balance can be argon gas. In the present invention, the arc and the molten pool are shielded by using the first shield gas, and the bead portion after welding is shielded by using the mixed gas of the first shield gas and the second shield gas. The concentration of carbon dioxide in the mixed gas supplied to the section is 1% by volume or more and 9% by volume or less
The balance may be argon gas and helium gas.

The gas shield jig of the present invention comprises a bead shield part having a canopy plate and side walls hanging down from the peripheral edge thereof, and a torch having a shield gas supply part for supplying shield gas into the bead shield part. It is characterized by The gas shield jig of the present invention comprises a bead shield part having a canopy plate and side walls hanging down from the periphery thereof, and a torch having a first shield gas supply part for supplying a first shield gas into the bead shield part. The bead shield part may be provided with a second shield gas supply port for supplying a second shield gas for shielding the bead after welding.

[0007]

1 is a schematic sectional view showing a first embodiment of a gas shield jig of the present invention. The gas shield jig 10 shown here is a rectangular canopy plate 1a.
The torch 2 is provided at one end 1c of the bead shield part 1 having a side wall 1b hanging from the periphery thereof. The tip 2a of the torch 2 has a shield gas supply unit 2 for supplying the shield gas G1 into the bead shield unit 1.
b and the arc-soluble solid electrode 3 are provided.
The torch 2 is inserted into the insertion hole 1e provided in the one end portion 1c of the bead shield portion 1 in the bead shield portion 1
It is detachably attached to. The torch 2 is arranged such that the tip 2 a is located inside the bead shield part 1.

Next, using the gas shield jig 10, M
A method of performing IG welding will be described. The bead shield part 1 is arranged on the welding base material M. At this time, the bead shield part 1 is arranged so as to be separated from the lower end of the side wall 1b and the welding base material M so as to form a slight gap C therebetween. The shield gas G1 supplied from a supply source (not shown) is supplied from the shield gas supply unit 2b of the torch 2 to the arc-soluble solid electrode 3
Also, the arc 4 is surrounded and supplied so as to cover the entire molten pool 5. As a result, the shield gas G1 is simultaneously supplied into the bead shield part 1. In this state, the arc-melting solid electrode 3 is used while advancing the gas shield jig 10 in the direction of the arrow in the drawing, and the welding base metal M is
MIG welding is performed.

As the shield gas G1, one having a carbon dioxide gas concentration of 1% by volume or more and 9% by volume or less and the balance being argon gas can be used. Shield gas G1
It is also possible to use a carbon dioxide gas having a carbon dioxide concentration of 1% by volume or more and 9% by volume or less and the balance of argon gas and helium gas. If the carbon dioxide concentration is less than the above range, the arc 4 becomes unstable, and if it exceeds the above range, the beads 6 are easily oxidized, which is not preferable.

The shield gas G1 supplied into the bead shield portion 1 fills the bead shield portion 1, flows so as to cover the bead 6 immediately after welding in the bead shield portion 1, and is discharged to the outside from the gap C. It With this method, the arc 4 can be stabilized by the shield gas G1, welding can be performed well, and oxidation of the beads 6 can be prevented.

FIG. 2 is a schematic sectional view showing a second embodiment of the gas shield jig of the present invention. In this gas shield jig 20, a torch 2 is provided at one end 11c of a bead shield portion 11 having a jig body 11a including a canopy plate 13 and a side wall 16 hanging down from the peripheral edge thereof, and a partition plate 12. It is considered as a structure. The torch 2 is detachably attached to the bead shield part 11 in a state of being inserted into an insertion hole 11e provided at one end 11c of the bead shield part 11.

The gas shield jig 20 is a canopy plate 1.
3, the second shield gas G2 in the bead shield part 11
A second shield gas supply port 15 for introducing the is provided. The partition plate 12 is provided below the side wall 16 substantially parallel to the canopy plate 13. The partition plate 12 is provided with a plurality of shield gas ejection holes 12a. In the gas shield jig 20, the canopy plate 13, the side wall 16, and the partition plate 12 allow the second shield gas from the shield gas supply port 15.
The gas storage chamber 17 in which the shield gas G2 of FIG. In the bead shield portion 11, the gas reservoir chamber 17 and the insertion hole 1e are defined by the shielding plate 14. The shield plate 14 is preferably formed so that the lower portion 14 a thereof projects below the partition plate 12.

When performing MIG welding using the gas shield jig 20, the first shield gas G1 is supplied from the shield gas supply portion 2b into the bead shield portion 1. First
The shield gas G1 is supplied so as to surround the arc-soluble solid electrode 3 and the arc 4 and cover the entire molten pool 5.
It flows so as to cover the bead 6 immediately after welding in the bead shield portion 11, and is discharged from the gap C to the outside.

At the same time, the second shield gas G2 is supplied from the second shield gas supply port 15 to the gas storage chamber 17.
The second shield gas G2 is ejected from the shield gas ejection hole 12a of the partition plate 12. The second shield gas G2 is mixed with the first shield gas G1 as a mixed gas,
It flows so as to cover the bead 6 immediately after welding in the bead shield portion 11, and is discharged from the gap C to the outside.

As the first shield gas G1, it is possible to use a gas having a carbon dioxide gas concentration of 1% by volume or more and 9% by volume or less and the balance being argon gas. As the first shield gas G1, it is also possible to use one having a carbon dioxide gas concentration of 1% by volume or more and 9% by volume or less and the balance being argon gas and helium gas. If the carbon dioxide concentration is less than the above range, the arc 4 becomes unstable, and if it exceeds the above range, the beads 6 are easily oxidized, which is not preferable. As the second shield gas G2, one having a carbon dioxide gas concentration of the same concentration as the carbon dioxide gas concentration of the first shield gas G1 can be used, but the carbon dioxide gas concentration is 6 vol. % Or less is preferably used. If this concentration exceeds this range, beads 6
Is easily oxidized, which is not preferable.

Regarding the component concentration of the second shield gas G2, the carbon dioxide concentration of the mixed gas (mixed gas of the first shield gas and the second shield gas) supplied to the bead portion 6 after welding is 1% by volume. It is also possible to set the content to 9% by volume or less and the balance to be argon gas. Regarding the component concentration of the second shield gas G2, the carbon dioxide concentration of the mixed gas is 1
It is possible to set the content to be not less than 9% by volume, and the balance is argon gas and helium gas.

In this gas shield jig 20, a gas different from the first shield gas G1 can be used as the second shield gas G2. Therefore, as the first shield gas G1, a gas suitable for shielding the arc 4 and the molten pool 5 is used, and as the second shield gas G2, a gas suitable for preventing the oxidation of the beads 6 (for example, compared with the first shield gas G1). It is possible to use those having a low concentration of carbon dioxide gas component). Therefore, it is possible to surely prevent a problem at the time of welding (such as insufficient melting of the welding base material M due to destabilization of the arc 4), and it is possible to suppress oxidation of the beads 6.

Since the shielding plate 14 is provided,
It is possible to prevent the second shield gas G2 from flowing forward (torch 2 side) in the traveling direction, and prevent the efficiency of MIG welding in the torch 2 from being reduced due to the influence of the second shield gas G2.

[0019]

EXAMPLES The characteristics of the MIG welding method for stainless steel of the present invention and the gas shield jig used for the method were confirmed. (Example 1) A torch 2 was used for MIG welding of stainless steel using the gas shield jig 10 shown in FIG.
The state of the arc and the state of the bead after welding were evaluated by changing the component mixture ratio of the first shield gas G1 supplied to the. The conditions for MIG welding are as follows.

1) Specifications of welding base material (stainless steel) used in the test Material: SUS304 Plate thickness: 3 mm 2) Welding conditions Welding current: 90 A Welding voltage: 20 V Welding speed: 40 cm / min Welding wire: MGS308LS, diameter 1 .2 mm (JI
SY308Li) Droplet transfer form: pulse spray arc 3) Component composition of shield gas G1 Argon gas is the main component, and carbon dioxide gas is 1 to 1
A mixed gas containing 0% by volume was used. Further, argon gas (carbon dioxide concentration of 0% by volume) which was not mixed with carbon dioxide was used.

As a result of performing MIG welding as the shielding gas G1, the following items were confirmed. (I) As shown in FIG. 3, when the concentration of carbon dioxide gas is 0% by volume, the carbon dioxide gas required for MIG welding becomes insufficient, the arc becomes unstable, and the bead is wavy or beaded. A cleaning action occurred along the line. (Ii) As shown in FIG. 8, when the carbon dioxide concentration was 10% by volume, there was a problem that the surface of the bead was oxidized and turned into black spots. (Iii) Carbon dioxide concentration of 1% by volume (see FIG. 4) or more, 9
In the range below the volume% (see FIG. 7), almost no bead oxidation was observed. It was also confirmed that good welding was performed without waviness of the beads. In particular, the concentration of carbon dioxide gas is 2% by volume or more (see FIG. 5) and 7% by volume.
(See FIG. 6) It was confirmed that when the shielding gas G1 in the following range was used, no bead oxidation was observed and good welding was possible.

Example 2 Stainless steel was MIG welded using the gas shield jig 20 shown in FIG. First
As the shielding gas G1, one containing argon gas as a main component and 6% by volume of carbon dioxide gas (flow rate: about 20 L) is used.
/ Min), pure argon gas is used as the second shield gas G2 (flow rate: about 20 L / min), in a welded state,
In particular, the oxidation state of the beads was observed. The welding base material and welding conditions were in accordance with Example 1. As a result of the test, it was confirmed that the arc 4 was stabilized, good welding was possible, and the bead 6 was prevented from being oxidized.

(Embodiment 3) Using the gas shield jig 10 shown in FIG. 1 and setting the welding current to less than 100 A,
When the welding current was set to 100 A or more, a welding test was performed using a shield gas containing carbon dioxide gas of 1 to 9% by volume and a main component gas. A mixed gas of helium gas and argon gas was used as the main component gas. The welding base material and welding conditions were in accordance with Example 1.

1) When welding current is 100 A or less, carbon dioxide gas concentration is 1 to 9% by volume, helium gas concentration is 30 to 8
Shielding gas G1 with 0% by volume and balance argon gas
By using, it was possible to perform good welding without oxidation of the beads. In particular, by using the shield gas G1 having a carbon dioxide gas concentration of 4 to 6% by volume, a helium gas concentration of 30 to 80% by volume, and the balance of argon gas, the arc is stabilized, the bead toe is stabilized, MIG welding with good wettability, no blowholes, and no bead oxidation was made possible.

2) When the welding current is 100 A or more, carbon dioxide gas concentration is 1 to 9% by volume, helium gas concentration is 10 to 3
Shielding gas G1 with 0% by volume and balance argon gas
By using, it was possible to perform good welding without oxidation. Particularly, the carbon dioxide concentration is set to 4 to 6% by volume,
By using the shield gas G1 having a helium gas concentration of 10 to 30% by volume and the balance of argon gas, the arc is stable, the bead toe is stable, and the wettability is good.
MIG that does not generate blowholes and does not oxidize beads
Welding has become possible.

In the present invention, as the gas shield jig, a jig having a bead shield part whose lateral side walls are formed higher than front and rear side walls in the jig advancing direction may be used. it can. When this gas shield jig is used, welding is performed while the gas shield jig is advanced with the lower end of the side wall in contact with the welding base material. According to this method, since the side wall on the side is in contact with the welding base metal, the shielding gas in the bead shield part is prevented from flowing out to the side, and the bead can be shielded surely. The antioxidant effect can be enhanced. Further, in the above embodiment, the bead shield portion including the rectangular canopy plate and the side wall hanging down from the peripheral edge thereof is illustrated, but the shape of the bead shield portion is not limited to this, and for example, a semi-pipe shape having a semicircular cross section. It can also be formed. This bead shield part can be used with the inner surface facing the bead.

[0027]

In the MIG welding method of the present invention, since the shielding gas having a carbon dioxide concentration of 1% by volume to 9% by volume and the balance being argon gas is used,
Oxidation of the beads can be prevented and good welding can be performed. Further, in the MIG welding method of the present invention, by using a shield gas having a carbon dioxide gas concentration of 1% by volume or more and 9% by volume or less and the balance of argon gas and helium gas, the bead oxidation is prevented. And good welding can be performed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a gas shield jig of the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of a gas shield jig of the present invention.

FIG. 3 is a photograph of a welding state when MIG welding was performed using a shield gas having a carbon dioxide concentration of 0% by volume.

FIG. 4 is a photograph of a welding state when MIG welding was performed using a shield gas having a carbon dioxide concentration of 1% by volume.

FIG. 5 is a photograph of a welding state when MIG welding was performed using a shielding gas having a carbon dioxide concentration of 2% by volume.

FIG. 6 is a photograph of a welding state when MIG welding was performed using a shield gas having a carbon dioxide concentration of 7% by volume.

FIG. 7 is a photograph of a welding state when MIG welding was performed using a shield gas having a carbon dioxide concentration of 9% by volume.

FIG. 8 is a photograph of a welding state when MIG welding was performed using a shielding gas having a carbon dioxide concentration of 10% by volume.

[Explanation of symbols]

10, 20 ... Gas shield jig, 1, 11 ... Bead shield part, 1a, 13 ... Canopy plate, 1b, 16 ... Side wall, 2 ... Torch, 2b ... Shield Gas supply unit, 3 ...
Arc-soluble solid electrode, 4 ... Arc, 5 ... Molten pool,
6 ... bead, 15 ... shield gas supply port, G1 ...
(First) shield gas, G2 ... second shield gas

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Claims (7)

[Claims] 1. A method of MIG welding of stainless steel, comprising shielding stainless steel with a shielding gas and performing MIG welding, wherein the shielding gas has a carbon dioxide concentration of 1% by volume or more and 9% by volume or less, and the balance is argon gas. A method of MIG welding stainless steel, characterized in that 2. A method for MIG welding of stainless steel, comprising shielding stainless steel with a shielding gas and performing MIG welding, wherein the shielding gas has a carbon dioxide gas concentration of 1% by volume or more and 9% by volume or less, and the balance is argon gas. A method for MIG welding of stainless steel, which is helium gas. 3. The method of MIG welding of stainless steel according to claim 1, wherein the shielding gas is supplied together with the arc and the molten pool so as to shield the bead after welding. 4. The arc and the molten pool are shielded with a first shield gas, and the bead portion after welding is shielded with a mixed gas of a first shield gas and a second shield gas, The mixed gas supplied to the bead portion has a carbon dioxide gas concentration of 1% by volume or more and 9% by volume or less, and the balance is argon gas, the MIG welding method for stainless steel. 5. An arc and a molten pool are shielded with a first shield gas, and a bead portion after welding is shielded with a mixed gas of a first shield gas and a second shield gas, The mixed gas supplied to the bead portion has a carbon dioxide gas concentration of 1% by volume or more and 9% by volume or less, and the balance is argon gas and helium gas.
G welding method. 6. A gas comprising: a bead shield part having a canopy plate and a side wall hanging down from a peripheral edge thereof; and a torch having a shield gas supply part for supplying a shield gas into the bead shield part. Jig for shield. 7. A bead shield part having a canopy plate and a side wall hanging down from a peripheral edge of the canopy plate, and a first part in the bead shield part.
And a torch having a first shield gas supply section for supplying a shield gas, wherein the bead shield section is provided with a second shield gas supply port for supplying a second shield gas for shielding the bead after welding. A unique gas shield jig.