JP2002205170A - Shield gas for mig welding of stailess steel and method for mig welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shield gas and a method for an MIG welding, by which an arc is stabilized, the end part of bead is stabilized, the wettability is excellent, and blowholes are not generated in the MIG welding of a stainless steel. SOLUTION: As a shield gas used for the MIG welding of a thin plate of stainless steel in which a solid wire is used and a welding current is not larger than 100A, a mixture gas of three components is used which consists of 4 to 6 vol.% CO2, 30 to 80 vol.% He, and the balance Ar. As a shield gas used for the MIG welding of a plate of medium or large thickness of stainless steel in which a solid wire is used and a welding current is 100A or larger, a mixture gas of three components is used which consists of 4 to 6 vol.% CO2, 10 to 30 vol.% He, and the balance Ar. These gases are used in the method for the MIG welding of stainless steel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixed gas used for gas shielded arc welding of austenitic stainless steel, and more particularly to a shielding gas suitable for MIG welding using a general-purpose solid wire and a shielding gas. The present invention relates to a method for MIG welding stainless steel using JIS.

[0002]

2. Description of the Related Art Shielding gas required for arc welding of stainless steel is not only easy to use, such as arc stability and low spatter generation, but also retains mechanical properties and corrosion resistance of metal. It is in. However, in the conventional MIG welding, a mixed gas obtained by adding about 2% by volume of an oxygen gas based on an argon gas is used as a shielding gas for welding stainless steel. It has been said that small amounts of welding can be performed. Also, a mixed gas containing about 20% by volume of carbon dioxide based on argon gas has been used as a shield gas for welding stainless steel, and as a result, it has been said that welding with a small amount of slag can be performed.

[0003] Further, Japanese Patent Application Laid-Open No. Hei 10-137940 discloses an invention relating to a "gas shielded arc welding method for stainless steel". The publication discloses a technique relating to gas shielded arc welding of stainless steel in which the feeding speed of the welding wire is stable and the amount of spatter is extremely small, and the surface of the welding wire is copper-plated. It is disclosed that a stainless solid wire is used and a mixed gas containing 20 to 40% by volume of helium gas, 0.5 to 3% by volume of carbon dioxide gas and the balance of argon gas is used as a shielding gas.

The above-mentioned Japanese Patent Application Laid-Open No. 10-137940 has been disclosed.
According to the publication, when helium gas is more than 40% by volume, blow holes are easily generated at the time of welding, and when carbon dioxide gas is more than 3% by volume, the bead appearance at the time of welding deteriorates. It has been disclosed.

[0005]

However, in MIG welding of stainless steel, if a mixed gas obtained by adding about 2% by volume of oxygen gas to argon gas as a shielding gas is used as a shielding gas, the bead is oxidized and the bead shape is reduced. It becomes a convex state, the penetration is shallow, and it becomes a finger state. In particular, when a thin plate is welded, the arc becomes unstable. In addition, there is a problem that a blow hole is generated when welding to a medium thick plate.

As a shielding gas disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 10-137940, a mixed gas containing 0.5 to 3% by volume of carbon dioxide and 20 to 40% by volume of helium based on argon gas. Using a general solid wire without copper plating
In the case of IG welding, when MIG welding is performed on a thin plate, the arc becomes unstable. On the other hand, when welding is performed on a thick plate, a problem such as occurrence of a blowhole occurs.

In view of the above circumstances, the present invention focuses on the welding current and the components and composition ratios of the shielding gas when performing MIG welding on stainless steel, and is a shielding gas for MIG welding that generates a small amount of slag. To provide a shielding gas and a MIG welding method, in which the arc is stable when the MIG is welded, the bead toe is stable, the wettability is good, and blow holes are not generated when a thick plate is welded. Was an issue.

[0008]

In order to solve the above-mentioned problems, a first aspect of the present invention relates to a method for reducing a welding current by 100%.
Less than A, a shielding gas for MIG welding stainless steel using a solid wire, a carbon dioxide gas having a composition of 4 to 6% by volume, a helium gas having a composition of 30 to 80% by volume, and an argon gas as a balance Of stainless steel, characterized by being composed of a mixed gas of three types consisting of
This is a shield gas for IG welding. The present invention according to claim 2 is a shield gas for MIG welding stainless steel using a solid wire with a welding current of 100 A or more, and a carbon dioxide gas having a composition of 4 to 6% by volume, 10 to 30%. A shielding gas for MIG welding of stainless steel, characterized in that the gas is a mixed gas of three kinds consisting of helium gas which is volume% and the balance is argon gas.

According to a third aspect of the present invention, the welding current is set to less than 100 A, and the shielding gas composition is composed of carbon dioxide gas having a composition of 4 to 6% by volume, helium gas having a composition of 30 to 80% by volume, and the balance being argon gas. Using three kinds of mixed gas, stainless steel was converted to MI using solid wire.
An MIG welding method for stainless steel characterized by G welding. As the invention according to claim 4,
A solid wire made of stainless steel using a welding gas having a welding current of 100 A or more, a carbon dioxide gas having a shielding gas composition of 4 to 6% by volume, a helium gas having a volume ratio of 10 to 30% by volume, and a balance gas of argon gas. Welding of stainless steel characterized by MIG welding using
This is a G welding method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the MIG welding of stainless steel, the present invention develops an appropriate shielding gas to be applied by a welding current in order to improve a welding condition, and uses the shielding gas to perform an adaptive welding current. Stainless steel with M
This is a method of performing IG welding. When the welding current is less than 100 A, a three-component gas mixture of 4 to 6% by volume of carbon dioxide gas, 30 to 80% by volume of helium gas, and the balance of argon gas is used as a shielding gas. In welding, the amount of slag generated is small, the arc is stable when MIG welding thin sheets, the bead toe is stable, the wettability is good, and the occurrence of blow holes when welding thick plates does not occur, This makes it possible to obtain a welded product in a good state.

When the welding current is 100 A or more, carbon dioxide gas of 4 to 6% by volume is used as a shielding gas.
The use of a mixed gas consisting of helium gas (volume%) and the balance of argon gas provides good arc stability in MIG welding of medium-thickness stainless steel, less occurrence of blowholes, and good condition. This makes it possible to obtain a welded product.

[0012]

EXAMPLES A shielding gas suitable for MIG welding of stainless steel according to the present invention will be described by way of examples. In order to confirm the characteristics and effects of the shielding gas of the present invention, confirmation tests of various characteristics were performed by the following examples.

[Example 1] As Example 1, when MIG welding was performed using a stainless steel thin plate with a welding current of less than 100 A, arc stability, degree of oxidation, amount of slag generated, wettability , Bead toe stability, amount of spatter generation ・ Confirmation of carbon pick-up The test was performed using three types of mixed gas of helium gas, carbon dioxide gas and argon gas as the shielding gas, and the composition (volume%) Was changed and MIG welding was performed.

(1) Confirmation test of arc stability, degree of oxidation, slag generation amount, wettability, stability of bead toe portion, and spatter generation amount The welding conditions in this test are as follows, As a sample, three types of mixed gas of helium gas, carbon dioxide gas and argon gas were used, and the composition (volume%) was changed to confirm the change of state. <Welding conditions>-Welding method: consumable electrode welding, pulse arc-Welding base material: SUS304 plate thickness 2.0 mm-Welding method: fillet welding-Welding wire: JIS Y308LSi, φ1.0 mm-Distance between tip base materials: 15mm ・ Torch tilt angle: 45 ° ・ Welding speed: 30cm / min ・ Arc voltage: 17-23V ・ Welding current: 50A

(2) Confirmation test of carbon pickup The welding conditions in this test are as follows. As the shielding gas, three kinds of mixed gas of helium gas, carbon dioxide gas and argon gas were used, and their composition (capacity) %) Was changed to confirm the change in state. <Welding conditions> ・ Welding method: consumable electrode welding / pulse arc ・ Welding material: SUS304 plate thickness 2.0 mm ・ Welding method: bead-on welding ・ Welding wire: JIS Y308LSi, φ1.0 mm ・ Distance between chip base materials: 15 mm -Torch tilt angle: 45 degrees-Welding speed: 30 cm / min-Arc voltage: 17 to 23 V-Welding current: 50 A

The above-mentioned evaluation judgment of each test item was performed based on Table 1. Table 2 shows the results of the tests (1) and (2). The test item “Penetration depth” in Table 1 was confirmed by checking the “throat thickness Y” of the bead 4 formed between the welding base materials 2 and 3 according to the schematic cross-sectional view of the fillet weld 1 shown in FIG. Was measured. In FIG.
Symbols A and B represent beads 4 in each of welding base materials 2 and 3.
, And reference numeral 4a is the bottom of the bead.

[Comparative Example] M using the shielding gas of the present invention
In order to clarify the characteristics obtained by IG welding, as Comparative Example 1, a mixed gas obtained by adding 2% by volume of oxygen gas to an argon gas base conventionally used as a shielding gas for MIG welding, and a flux-containing gas were used. Using a wire, so-called FCW (Flux Core Wire) welding using 100% by volume carbon dioxide as a shielding gas was performed. Table 2 shows the test results of the properties obtained in these examples, together with the results of Example 1.

[0018]

[Table 1]

[0019]

[Table 2]

[Evaluation of Welding Condition] A stainless steel thin plate having a thickness of 2 mm and a welding current of 50 A, which was performed in Example 1 above,
In the case where MIG welding was performed, the welding state was evaluated. In the laser welding in Example 1 described above, the degree of oxidation of the bead was examined. As a result, although slight oxidation was observed, there was no particular problem with the other items checked, and good welding could be performed. In particular, the arc was stable even at a low current, and the bead was able to be welded with a good fit and a flat bead without waving at the toe.

As a result, concentrated stress was hardly applied to the welded portion, and a weld having good strength could be obtained. In addition,
According to the present invention, a mixed gas of helium gas (40% by volume) and carbon dioxide gas (5% by volume) was used for comparison with the weld state of the toe end of the bead according to the present invention. FIG. 2 shows a photograph of a state of a welded portion by a laser welding method when is used as a shielding gas,
For comparison, FIG. 3 shows a photograph of a state of a welded portion by the MIG welding method using a mixed gas containing an argon gas (98% by volume) as a base gas and an oxygen gas (2% by volume) as a shielding gas. . As apparent from a comparison between FIG. 2 and FIG. 3, a shielding gas composed of a mixed gas of three kinds of [helium gas] + [carbon dioxide gas] + [remainder argon gas] according to the present invention shown in FIG. It is confirmed that the welding state of the laser-welded photograph is clearly better than the welding state of the photograph of FIG.

When the concentration of carbon dioxide gas is gradually reduced to make it thinner, and when the concentration becomes less than 4% by volume, the arc becomes unstable. As a result, the toe end of the bead becomes wavy. The problem of instability occurred. On the other hand, when the concentration of carbon dioxide is increased and increased, 6% by volume
At this point, the inconvenience of starting to oxidize occurs. Further, the value of the carbon pickup becomes large, which causes a problem that may cause a sensitization phenomenon.

Further, when the helium gas exceeds 80% by volume, the arc becomes unstable and a problem arises that spatter is generated. Conversely, if the helium gas content is 30% by volume or less, the arc becomes unstable, the beat becomes a convex bead, and the penetration becomes shallow. These phenomena were almost the same as those in Table 2 even when the welding current was changed from 40 A to 100 A.

Example 2 Next, as Example 2, MIG welding was performed using a medium-thick stainless steel plate at a welding current of 100 A or more. Arc stability, degree of oxidation, amount of slag generated, spatter Confirmation test was conducted for test items such as generation amount and penetration depth, confirmation of carbon pick-up, and amount of porosity, as described above, divided into three series. The confirmation test will be described below.

(1) Confirmation test of arc stability, degree of oxidation, slag generation amount, spatter generation amount, and penetration depth The welding conditions in this test are as follows, and the shielding gas used in Example 1 was as follows. In the same manner as in the thin plate welding test, three types of mixed gas of helium gas, carbon dioxide gas and argon gas were used, and the composition (volume%) was changed to confirm the change of the state. <Welding conditions> ・ Welding method: consumable electrode welding, pulse arc ・ Welding base material: SUS304 5 mm thick ・ Welding method: fillet welding ・ Welding wire: JIS Y308LSi, φ1.2 mm ・ Distance between tip base materials: 15 mm ・Torch tilt angle: 45 degrees ・ Welding speed: 30 cm / min ・ Arc voltage: 22 to 27 V ・ Welding current: 150 A

(2) Confirmation test of carbon pickup The welding conditions in this test are as follows, and three kinds of mixed gas of helium gas, carbon dioxide gas and argon gas were used as the shielding gas as described above. By changing the composition (% by volume), a change in the state was confirmed. <Welding conditions> ・ Welding method: consumable electrode welding, pulse arc ・ Welding base material: SUS304 10 mm thick ・ Welding method: bead-on welding ・ Welding wire: JIS Y308LSi, φ1.2 mm ・ Distance between tip base materials: 15 mm ・ Torch Tilt angle: 45 degrees-Welding speed: 30 cm / min-Arc voltage: 24-28 V-Welding current: 200 A

(3) Test for confirming the amount of generated pores The welding conditions in this test are as follows. As the shielding gas, a mixed gas of helium gas, carbon dioxide gas and argon gas was used in the same manner as described above. The composition (volume%) was changed to confirm the change in the state. <Welding conditions> ・ Welding method: consumable electrode welding, pulse arc (no pulse for FCW) ・ Welding base material: SUS304 150 mm long, 100 m wide
m, plate thickness 10 mm ・ Welding method: V groove butt welding ・ Sample: Tested and confirmed with three samples ・ Welding wire: JIS Y308LSi, φ1.2 mm ・ Torch inclination angle: 45 degrees ・ Distance between chip base materials: 20 mm ・Welding speed: 30 cm / min-Arc voltage: 24-28 V-Welding current: 200 A

The evaluation of the test items in the above-mentioned confirmation tests (1), (2) and (3) was performed by the method shown in Table 1. The results are shown in Table 3. In order to confirm the performance of the present invention, a comparative test was separately performed. This will be described below as Comparative Example 2.

[Comparative Example 2] As Comparative Example 2, a sample was made of a medium-thickness stainless steel as in Example 2, and used as a shielding gas as an argon gas base conventionally used in MIG welding. 2% by volume of oxygen gas
Test items were confirmed in each of the case where a mixed gas to which was added was used, and the case where so-called FCW welding was performed using 100% by volume carbon dioxide gas as a shielding gas using a flux-cored wire. The results are shown in Table 3 together with the results of Example 2.

[0030]

[Table 3]

[Evaluation of Welding Condition] The welding condition was evaluated in the case where MIG welding was performed on a stainless steel medium thickness plate having a thickness of 5 mm and 10 mm and a welding current of 100 A or more, which was performed in Example 2 above. Was. In the second embodiment, a medium-thick plate was prepared by using a mixed gas of [helium gas] + [carbon dioxide gas] + [argon gas] of the present invention as a shielding gas.
A comparison between a welded portion MIG-welded with a welding current of 00 A or more and a welded portion MIG-welded with 2% by volume of oxygen gas to an argon gas base, which is a shielding gas for conventional MIG welding in Comparative Example 2, shows that Example 2 It was found that the shielding gas of the present invention had an excellent feature that oxidation was less.

Also, when compared with the conventional FCW welding method of Comparative Example 2 using a flux-cored wire and 100% by volume of carbon dioxide gas as a shielding gas, the above-mentioned three-type mixed gas of the present invention of Example 2 was used as a shielding gas. It was confirmed that the MIG welding used had excellent characteristics that the stability was better and the amount of slag generated was very small. Also, in the other test items described above, the MIG welding using the mixed gas of He gas, CO ₂ gas and the remaining Ar gas of Example 2 of the present invention as a shielding gas has no particular problem and is excellent. Welding could be performed, and it was confirmed that the mixed gas of three types was a very excellent shielding gas for MIG welding overall.

It should be noted that the concentration of carbon dioxide gas was reduced with the shielding gas of the mixed gas of three types of He gas, CO ₂ gas, and the remaining Ar gas in Example 2, and when the concentration became 4% by volume or less,
There is a problem that the amount of generated pores increases. Conversely, if the concentration of carbon dioxide gas is increased to 6% by volume or more, oxidation of the bead surface becomes remarkable, and the amount of carbon in the weld metal increases, resulting in a problem of concern about corrosion resistance. Was confirmed.

Further, the He gas, CO ₂ gas,
It has been confirmed that when the helium gas exceeds 30% by volume in the shielding gas of the mixed gas of the remaining Ar gas and the helium gas, the phenomenon that the amount of generated pores increases occurs, which causes an undesirable problem in the welding state. There was found. Conversely, when the helium gas is set to 10% by volume or less, the penetration depth becomes MIG by a shielding gas obtained by adding 2% by volume of oxygen gas to an argon gas base used in conventional MIG welding.
It was confirmed that there was no significant difference from the welded portion and no improvement was made.

[0035]

The shielding gas for MIG welding of stainless steel and the method for MIG welding of the present invention are carried out in the above-described embodiment, and have the following effects. Stainless steel M
At the time of IG welding, the present invention employs an adaptive welding current according to the thickness of the material to be welded, that is, the thickness of a thin plate and a medium-thick plate such as stainless steel, and a shield gas of helium gas, carbon dioxide gas, and argon gas. By changing the composition of the mixed gas of the species, extremely good MIG welding can be performed.

Particularly, in the case of a thin stainless steel having a welding current of less than 100 A, the shielding gas composition is composed of carbon dioxide gas having a composition of 4 to 6% by volume, helium gas having a composition of 40 to 80% by volume, and the balance being argon gas. The use of the mixed gas of three types provided an excellent effect that the arc was stable even at a low current, the bead toe was not wavy, the wettability was good, and the welding with good adaptability could be performed.

In the case of a medium-thick plate stainless steel to which an applicable welding current is 100 A or more, the shielding gas composition is 4
The use of a gas mixture of 3 to 6% by volume of carbon dioxide gas, 10 to 30% by volume of helium gas and the balance of argon gas provides good arc stability, a small amount of slag, and no blowholes. In addition, an excellent effect that welding with less oxidation can be performed was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a fillet weld showing the penetration depth.

FIG. 2 Arium-based helium gas 40% by volume,
The photograph of the MIG weld using the mixed gas of carbon dioxide 5% by volume as the shielding gas.

FIG. 3 is a photograph of a MIG weld using a mixed gas obtained by adding 2% by volume of oxygen gas based on argon gas as a shielding gas.

[Explanation of symbols]

1 ... fillet weld, 2, 3 ... base metal, 4 ... bead, 4a ... bottom of bead, A, B ... toe, Y ... throat thickness

Claims (4)

[Claims] 1. A shielding gas for MIG welding stainless steel with a welding current of less than 100 A using a solid wire, the composition being carbon dioxide gas having a composition of 4 to 6% by volume, 30 to 80% by volume. A shield gas for MIG welding stainless steel, comprising a helium gas and a balance of three kinds of gases consisting of argon gas. 2. A shielding gas for MIG welding stainless steel using a solid wire with a welding current of 100 A or more, which is carbon dioxide gas having a composition of 4 to 6% by volume and 10 to 30% by volume. A shield gas for MIG welding stainless steel, comprising a helium gas and a balance of three kinds of gases consisting of argon gas. 3. A carbon dioxide gas having a welding current of less than 100 A and a shielding gas composition of 4 to 6% by volume, 30 to 8% by volume.
A MIG welding method for stainless steel, wherein the stainless steel is MIG-welded using a solid wire, using a helium gas of 0% by volume and a balance gas of argon gas as a balance. 4. A carbon dioxide gas having a welding current of 100 A or more and a shielding gas composition of 4 to 6% by volume, 10 to 3% by volume.
A MIG welding method for stainless steel, wherein the stainless steel is MIG-welded using a solid wire, using a helium gas of 0% by volume and a balance gas of argon gas as a balance.