JP3663184B2 - Stainless steel MIG welding method and gas shielding jig - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a MIG welding method for stainless steel and a gas shielding jig used therefor.
[0002]
[Prior art]
In arc welding of stainless steel, it is required to prevent deterioration of the mechanical properties and corrosion resistance of the metal.
Conventionally, in the MIG welding method using solid wire in the arc welding method of stainless steel, for example, a shielding gas in which 2% by volume of oxygen gas is added to argon gas is used.
In this method, welding with a small amount of slag generation and a small amount of carbon pickup and spatter is possible.
However, this method is not suitable for welding of structures that place importance on the appearance because the bead is heavily oxidized.
[0003]
Therefore, for MIG welding of this type of stainless steel structure, a flux cored wire in which flux is mixed with slag welding wire is used, and carbon dioxide gas 100% by volume of shielding gas or argon gas is used. A shielding gas to which a volume% of carbon dioxide gas is added is used.
In MIG welding using a flux-cored wire, since the slag covers the bead after welding, the bead is not oxidized, and the appearance of the workpiece can be improved.
However, in MIG welding using a flux cored wire, it is necessary to remove the slag after welding, and there is a problem that the work is troublesome. Moreover, since the slag is scattered around with the work, there is a problem that it is not preferable for environmental conservation.
[0004]
[Problems to be solved by the invention]
In order to prevent oxidation during arc welding, there is a method of shielding with an inert gas. However, when shielding only with an inert gas in MIG welding, the generated arc is affected by this shielding gas and is good. There is a disadvantage that it is impossible to perform proper welding.
The present invention has been made in view of the above circumstances, and provides a MIG welding method and a gas shielding jig capable of preventing bead oxidation and performing good welding in stainless steel MIG welding. With the goal.
[0005]
[Means for Solving the Problems]
To solve this problem,
The invention according to claim 1 is a stainless steel MIG welding method in which stainless steel is shielded with a shielding gas and MIG welding is performed. When the welding current is less than 100 A, the shielding gas has a carbon dioxide gas concentration of 4 to 6% by volume. A stainless steel MIG welding method using a gas having a helium concentration of 30 to 50% by volume and the balance being argon gas.
The invention according to claim 2 is a stainless steel MIG welding method in which stainless steel is shielded with a shielding gas and MIG welding is performed. When the welding current is 100 A or more, the shielding gas has a carbon dioxide gas concentration of 4 to 6% by volume or less. A stainless steel MIG welding method characterized by using a gas having a helium concentration of 10 to 30% by volume and the balance being argon gas.
The invention according to claim 3 is the MIG welding method for stainless steel according to claim 1 or 2, characterized in that the shielding gas is supplied together with the arc and the molten pool so as to shield the welded bead.
[0006]
According to a fourth aspect of the present invention, there is provided a gas shield treatment comprising a bead shield part having a canopy plate and a side wall depending from the periphery thereof, and a torch having a shield gas supply part for supplying a shield gas into the bead shield part. Tools,
The gas shield jig is characterized in that the side walls of the bead shield portion have higher side walls than the front and rear side walls in the jig traveling direction.
The invention according to claim 5 includes a bead shield portion including a canopy plate and a side wall depending from the periphery thereof, and a torch having a first shield gas supply portion for supplying a first shield gas into the bead shield portion. A gas shield jig,
The bead shield part is provided with a second shield gas supply port for supplying a second shield gas for shielding the bead after welding,
Of the side walls of the bead shield part, a side shield side wall is made higher than the front side wall and the rear side wall in the jig traveling direction.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic sectional view showing a first embodiment of a gas shield jig according to the present invention.
The gas shielding jig 10 shown here has a structure in which a torch 2 is provided at one end 1c of a bead shield part 1 having a rectangular canopy plate 1a and a side wall 1b hanging from the periphery thereof.
The tip 2a of the torch 2 is provided with a shield gas supply part 2b for supplying the shield gas G1 into the bead shield part 1 and an arc-soluble solid electrode 3.
The torch 2 is detachably attached to the bead shield part 1 in a state where the torch 2 is inserted into the insertion hole 1e provided in the one end 1c of the bead shield part 1.
The torch 2 is arranged so that the tip 2 a is located in the bead shield part 1.
Moreover, in the side wall 1a, the side wall on the side is formed higher than the side wall on the front side and the rear side in the traveling direction of the jig 10, and the lower end of the side wall is in contact with the welding base material. It comes to become.
[0008]
Next, a method for performing MIG welding using the gas shielding jig 10 will be described.
The bead shield portion 1 is disposed on the weld base material M. At this time, the bead shield part 1 is separated so that the lower end of the front and rear side walls in the jig traveling direction of the side wall 1b and the welding base material M form a slight gap C, and the side side walls are separated. Is placed in contact with the weld base material M.
A shield gas G1 supplied from a supply source (not shown) is supplied from the shield gas supply unit 2b of the torch 2 so as to surround the arc-soluble solid electrode 3 and the arc 4 and cover the entire molten pool 5. As a result, the shield gas G1 is also supplied into the bead shield unit 1 at the same time.
In this state, MIG welding of the welding base material M is performed using the arc-soluble solid electrode 3 while the gas shield jig 10 is advanced in the direction of the arrow in the drawing.
[0009]
As the shielding gas G1, a gas having a carbon dioxide gas concentration of 4 to 6% by volume, a helium concentration of 30 to 50% by volume, and the balance being argon gas is used when the welding current is less than 100A.
As the shielding gas G1, a gas having a carbon dioxide concentration of 4 to 6% by volume or less, a helium concentration of 10 to 30% by volume, and the balance being argon gas is used when the welding current is 100A or more.
By using such a shielding gas G1, the arc is stabilized, the bead toe is stabilized, the wettability is good, the blowhole is not generated, and the bead is not oxidized, and MIG welding can be performed.
[0010]
The shield gas G1 supplied into the bead shield part 1 fills the bead shield part 1, flows so as to cover the bead 6 immediately after welding in the bead shield part 1, and is discharged from the gap C to the outside. Moreover, since the side wall of the side wall 1b is in contact with the weld base material, the shield gas in the bead shield part is prevented from flowing out to the side, and the bead can be shielded reliably. Further, the bead oxidation prevention effect can be enhanced.
In this method, the arc 4 can be stabilized by the shielding gas G1, the welding can be performed satisfactorily, and the bead 6 can be prevented from being oxidized.
[0011]
FIG. 2 is a schematic cross-sectional view showing a second embodiment of the gas shield jig of the present invention.
This gas shield jig 20 is provided with a torch 2 at one end part 11c of a bead shield part 11 having a jig body 11a comprising a canopy plate 13 and a side wall 16 hanging from the periphery thereof, and a partition plate 12. It is structured.
The torch 2 is detachably attached to the bead shield part 11 in a state where the torch 2 is inserted into an insertion hole 11e provided in one end part 11c of the bead shield part 11.
Moreover, in the side wall 16, the side wall of the side is formed higher than the front side wall and the rear side wall in the traveling direction of the jig 20, and the lower end of the side wall is in contact with the welding base material. It comes to become.
[0012]
The gas shield jig 20 is provided with a second shield gas supply port 15 for introducing the second shield gas G2 into the bead shield part 11 in the canopy plate 13.
The partition plate 12 is provided at a lower portion of the side wall 16 so as to be 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 define a gas reservoir chamber 17 in which the second shield gas G <b> 2 from the shield gas supply port 15 stays.
In the bead shield part 11, the gas reservoir chamber 17 and the insertion hole 1 e are partitioned by the shielding plate 14.
The shielding plate 14 is preferably formed so that the lower portion 14 a protrudes below the partition plate 12.
[0013]
When performing MIG welding using the gas shield jig 20, the first shield gas G1 is supplied from the shield gas supply unit 2b into the bead shield unit 11. At this time, the bead shield portion 11 is separated so that the lower end of the side wall 16 on the front side and the rear side in the jig traveling direction and the welding base material M form a slight gap C, and the side side wall is separated. Is placed in contact with the weld base material M.
The first 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, and flows so as to cover the bead 6 immediately after welding in the bead shield part 11, and from the gap C. It is discharged outside. Moreover, since the side wall of the side wall 1b is in contact with the weld base material, the shield gas in the bead shield part is prevented from flowing out to the side, and the bead can be shielded reliably. Further, the bead oxidation prevention effect can be enhanced.
[0014]
At the same time, the second shield gas G 2 is supplied from the second shield gas supply port 15 to the gas reservoir 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, flows as a mixed gas so as to cover the bead 6 immediately after welding in the bead shield part 11, and is discharged from the gap C to the outside.
[0015]
As the first shield gas G1, when the welding current is less than 100A, a gas having a carbon dioxide concentration of 4 to 6% by volume, a helium concentration of 30 to 50% by volume, and the balance being argon gas is used. As the shielding gas G1, a gas having a carbon dioxide concentration of 4 to 6% by volume or less, a helium concentration of 10 to 30% by volume, and the balance being argon gas is used when the welding current is 100A or more.
As the second shield gas G2, the same one as the first shield gas G1 can be used.
[0017]
In the gas shield jig 20, a second shield gas G2 different from the first shield gas G1 can be used.
For this reason, the first shield gas G1 is suitable for shielding the arc 4 and the molten pool 5, and the second shield gas G2 is suitable for preventing the bead 6 from being oxidized (for example, compared with the first shield gas G1). A carbon dioxide component having a low concentration can be used.
Therefore, problems during welding (such as insufficient melting of the weld base material M due to instability of the arc 4) can be reliably prevented, and oxidation of the beads 6 can be suppressed.
[0018]
Further, since the shielding plate 14 is provided, the second shield gas G2 is prevented from flowing forward (torch 2 side) in the traveling direction, and the efficiency of MIG welding in the torch 2 is reduced due to the influence of the second shield gas G2. Can be prevented.
[0019]
The characteristics of the MIG welding method for stainless steel according to the present invention and the gas shielding jig used therefor were examined .
( Example 1)
When MIG welding stainless steel using the gas shield jig 10 shown in FIG. 1, the component mixing ratio of the first shield gas G1 supplied to the torch 2 is changed to change the arc state and the welded bead state. Evaluated. The conditions for MIG welding are as follows.
[0020]
1) Specification material of weld base material (stainless steel) used for the test: SUS304
Thickness: 3mm
2) Welding conditions Welding current: 90A
Welding voltage: 20V
Welding speed: 40 cm / min
Welding wire: MGS308LS, diameter 1.2mm (JIS Y308Li)
Droplet transfer form: pulse spray arc 3) Component composition of shield gas G1 Argon gas was used as a main component, and a mixed gas in which 1 to 10% by volume of carbon dioxide gas was mixed with this was used. Argon gas (carbon dioxide concentration 0% by volume) not mixed with carbon dioxide was used.
[0021]
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 necessary for MIG welding becomes insufficient, the arc becomes unstable, the bead undulates, Along with the cleaning action.
(Ii) As shown in FIG. 8, when the carbon dioxide gas concentration was 10% by volume, there was a problem that the surface of the bead was oxidized and became black like a spot.
(Iii) When the carbon dioxide gas concentration was in the range of 1% by volume (see FIG. 4) or more and 9% by volume (see FIG. 7) or less, bead oxidation was hardly observed. It was also confirmed that good welding was performed without waving of beads.
In particular, when the shielding gas G1 having a carbon dioxide concentration in the range of 2% by volume (see FIG. 5) or more and 7% by volume (see FIG. 6) or less is used, bead oxidation is not observed and good welding can be achieved. It was confirmed that
[0022]
( Example 2)
Stainless steel was MIG welded using the gas shield jig 20 shown in FIG.
As the first shield gas G1, a gas containing 6% by volume of carbon dioxide gas containing argon gas as a main component is used (flow rate: about 20 L / min), and as the second shield gas G2, pure argon gas is used (flow rate: about 20 L / min). 20 L / min), the welded state, in particular the bead oxidation state, 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 oxidation of the bead 6 could be prevented.
[0023]
( Example 3)
Using the gas shielding jig 10 shown in FIG. 1, when the welding current is less than 100A and when the welding current is 100A or more, carbon dioxide gas 1 to 9% by volume and main component gas are used as the shielding gas. Welding tests were performed using those included.
As the main component gas, a mixed gas of helium gas and argon gas was used.
The welding base material and welding conditions were in accordance with Example 1.
[0024]
1) When the welding current is less than 100 A By using the shielding gas G1 having a carbon dioxide gas concentration of 1 to 9% by volume, a helium gas concentration of 30 to 80% by volume and the balance being argon gas, good welding is performed without bead oxidation I was able to.
In particular, by using the shielding 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 being argon gas, the arc is stabilized and the bead toe is stabilized, MIG welding with good wettability, no blowholes, and no bead oxidation is possible.
[0025]
2) When welding current is 100A or more, good welding without oxidation can be performed by using shield gas G1 having carbon dioxide concentration of 1 to 9% by volume, helium gas concentration of 10 to 30% by volume, and the balance being argon gas. did it.
In particular, by using the shielding gas G1 having a carbon dioxide gas concentration of 4 to 6% by volume, a helium gas concentration of 10 to 30% by volume, and the balance being argon gas, the arc is stabilized and the bead toe is stabilized, MIG welding with good wettability, no blowholes, and no bead oxidation is possible.
[0026]
Further, in the above-described embodiment of the gas shield jig, the bead shield portion including the rectangular canopy plate and the side wall hanging from the peripheral edge thereof is illustrated, but the shape of the bead shield portion is not limited to this, for example, a cross section It can also be formed in a semicircular half pipe shape. This bead shield part can be used with the inner surface facing the bead.
[0027]
【The invention's effect】
According to the present invention, bead oxidation can be prevented and good welding can be performed in MIG welding of stainless steel.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a first embodiment of a gas shielding jig of the present invention.
FIG. 2 is a schematic cross-sectional view showing a second embodiment of the gas shielding jig of the present invention.
FIG. 3 is a photograph of a welded state when MIG welding is performed using a shielding gas having a carbon dioxide gas concentration of 0% by volume.
FIG. 4 is a photograph of a welding state when MIG welding is performed using a shielding gas having a carbon dioxide gas concentration of 1% by volume.
FIG. 5 is a photograph of a welding state when MIG welding is performed using a shield gas having a carbon dioxide concentration of 2% by volume.
FIG. 6 is a photograph of a welding state when MIG welding is performed using a shield gas having a carbon dioxide gas concentration of 7% by volume.
FIG. 7 is a photograph of a welding state when MIG welding is 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 is performed using a shielding gas having a carbon dioxide concentration of 10% by volume.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10, 20 ... Jig for gas shields, 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

Claims (5)

In the MIG welding method of stainless steel in which stainless steel is shielded with a shielding gas and MIG welding is performed, when the welding current is less than 100 A, the shielding gas has a carbon dioxide concentration of 4 to 6% by volume and a helium concentration of 30 to 50 volume. A stainless steel MIG welding method characterized by using a gas whose percentage is argon gas and the balance being argon gas . In a stainless steel MIG welding method in which stainless steel is shielded with a shielding gas and MIG welding is performed, when the welding current is 100 A or more, the shielding gas has a carbon dioxide concentration of 4 to 6% by volume or less and a helium concentration of 10 to 30. A stainless steel MIG welding method characterized by using a gas having a volume% and the balance being argon gas .   3. The stainless steel MIG welding method according to claim 1, wherein the shielding gas is supplied together with the arc and the molten pool so as to shield the welded bead. A gas shield jig comprising a bead shield part having a canopy plate and a side wall depending from the periphery thereof, and a torch having a shield gas supply part for supplying shield gas into the bead shield part,
  A gas shielding jig characterized in that, of the side walls of the bead shield portion, the side walls on the side are made higher than the side walls on the front side and the rear side in the jig traveling direction. A gas shield jig comprising a bead shield part having a canopy plate and a side wall hanging 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 is provided with a second shield gas supply port for supplying a second shield gas for shielding the bead after welding,
  A gas shielding jig characterized in that, of the side walls of the bead shield portion, the side walls on the side are made higher than the side walls on the front side and the rear side in the jig traveling direction.

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