JP2003320479A - Titanium or titanium alloy mig welding wire having good arc stability, and mig welding of method titanium or titanium alloy by using the wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MIG welding wire and a method for MIG welding titanium and titanium alloy with stability and high efficiency. <P>SOLUTION: The surface of a titanium or titanium alloy wire for MIG welding (preferably, 1.6 to 2.0 mm of the outer diameter of the cross section) is coated with 5×10<SP>-6</SP>to 1.0×10<SP>-3</SP>g/mm<SP>2</SP>of Al particles having the average diameter 0.1 to 100 μm and has good arc stability, and it is preferable that titanium or a titanium alloy is MIG welded by pulse welding current (for example, 300 A≤(peak current) ≤500 A and 2.0≤(peak current)/(base current)≤5.0). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium or titanium alloy MIG welding wire having excellent arc stability, which is used when MIG welding titanium or titanium alloy structural materials in the field of structures such as ships and building structures. And a MIG welding method using the wire.

[0002]

2. Description of the Related Art Conventionally, titanium or titanium alloy materials have been used for structural materials such as ships, building structures, automobiles, motorcycles, etc., which require high corrosion resistance. The TIG welding method (tungsten inert gas metal welding method), which is one of the non-consumable electrode welding methods, is mainly used.

In addition, as a typical welding method, there is a consumable electrode type welding method such as MIG welding method (inert gas metal arc welding method). This MIG welding method uses T
Compared with the IG welding method, it is a welding method that can obtain welding efficiency of several times or more, but when using pure Ti welding wire and welding titanium and titanium alloys with this method, the welding arc becomes unstable. , Weld beads with good appearance cannot be obtained.

This is because during welding, the arc moves violently between the oxide films present on the surface of the material to be welded (titanium or titanium alloy) in order to secure the cathode spot and maintain the arc, and the arc is rampant. It is thought to be due to the wandering phenomenon.

That is, this wandering phenomenon causes the welding bead to meander and a large amount of welding spatter to adhere to the surface of the material to be welded (titanium or titanium alloy).

As described above, in MIG welding of titanium and titanium alloys using a pure Ti welding wire, the weld bead meanders and spatter adheres due to the wandering phenomenon, resulting in a poor appearance of the welded portion. .

On the other hand, in the TIG welding method, an arc is generated using a non-consumable electrode having a high melting point, and a welding wire is supplied to a molten pool generated in a material to be welded for welding, so that spatter does not occur. Also, since the electrode side has a negative polarity (the welded side has a positive polarity), a cleaning action occurs in which the oxide film on the surface of the welded material is removed during welding, and as a result, the wandering phenomenon does not occur. The weld bead does not meander, and a weld having a good appearance is obtained.

For this reason, the TIG welding method is exclusively used when welding the structural material of titanium or titanium alloy.

For example, Japanese Patent Publication No. 59-226159 discloses a method in which two titanium strips having a worked structure are abutted with each other in the longitudinal direction and TIG-welded to soft-anneal the base metal portion in the vicinity of the welded portion. There is disclosed a method of connecting titanium strips for a connection that does not break.

However, in TIG welding, it is necessary to hold the welding torch and the welding wire in proper positions, and it is preferable that a device for holding the welding torch and the welding wire can be used in a factory or the like. In the case of a large structure, the welding operator has to move with the progress of welding while holding the welding torch and the welding wire, which increases the work load on the welding operator.

In order to reduce this work load, it is conceivable to incorporate a guide device for feeding the welding wire into the welding torch. A welding torch provided with such a device is
It is more expensive than a semi-automatic welding torch for MIG welding.

Further, in the TIG welding, the welding heat input is smaller than that in the MIG welding, so that the welding time is unavoidably long, and therefore the work efficiency is poor. Furthermore, TI
In G welding, since the welding time is long, the amount of gas used as the shield gas is inevitably large and the welding cost is high.

As an alternative welding method to the TIG welding method, Japanese Patent Laid-Open No. 2000-280076 uses a shield gas in which a trace amount of an oxidizing gas is added to an inert gas and a consumable electrode of titanium or a titanium alloy. The arc welding method for titanium and titanium alloys in which a pulse welding current is applied to perform welding is disclosed.

However, when oxygen or oxide is supplied from the shield gas as in the above welding method, the welding arc is stabilized, while a large amount of oxygen is mixed in the weld metal. It hardens and causes deterioration of mechanical properties such as reduction of elongation.

[0015]

SUMMARY OF THE INVENTION In view of the above problems in the prior art, the present invention provides titanium and titanium alloys,
MI that enables stable and high-efficiency MIG welding, as well as on-site welding by semi-automatic welding, and cost reduction by reducing the amount of shield gas used by shortening the welding time.
An object of the present invention is to provide a G welding wire and a MIG welding method.

[0016]

[Means for Solving the Problems] The root cause of the wandering phenomenon is an oxide existing on the surface of the material to be welded and acting as a cathode spot. If the oxide is constantly and intensively formed, the welding arc can be stably maintained and continued, and the wandering phenomenon can be suppressed.

However, according to the experimental results of the present inventor, even if an element that easily forms an oxide is present in the material to be welded, it is not always necessary that the surface of the material to be welded which is closest to the tip of the welding wire is Oxides are not always formed in a concentrated manner.

Therefore, the inventor of the present invention, if an element that easily forms an oxide is supplied into the welding arc together with the welding wire,
The idea is that the oxide that acts as a cathode spot can be constantly and intensively formed on the surface of the material to be welded that is closest to the tip of the welding wire, and the welding arc can be stably maintained and continued during welding. In order to realize this idea, the means for supplying an element that easily forms an oxide into the welding arc together with the welding wire was examined.

Then, the present inventor uses Al as an element that easily forms an oxide, and if Al or an Al-containing substance is adhered to the surface of the welding wire in the form of particles and supplied into the welding arc, the welding is performed. On the surface of the material to be welded that is closest to the tip of the wire, Al oxide that acts as a cathode spot can be constantly formed, and as a result, the welding arc can be stably maintained and continued during welding. , And found that the wandering phenomenon can be suppressed.

The inventor of the present invention can adjust the amount of Al or Al-containing substance adhered to the surface of the welding wire to adjust the amount of Al oxide that acts as a cathode spot to an appropriate range. It has been found that the welding arc can be maintained and continued more stably, and the wandering phenomenon can be further suppressed.

The present invention was made on the basis of the above findings, and the gist thereof is as follows.

(1) A titanium or titanium alloy wire used for MIG welding of titanium or a titanium alloy, wherein Al or Al-containing particles having an average particle size of 0.1 to 100 μm are fixed to the surface of the wire. Titanium or titanium alloy MIG welding wire with excellent arc stability.

(2) The above-mentioned (1), wherein the Al or Al-containing particles are fixed on the average of 5.0 × 10 ^{−6 to} 1.0 × 10 ⁻³ g / mm ² . Titanium or titanium alloy MIG welding wire with excellent arc stability.

(3) The above-mentioned (1), wherein the Al or Al-containing particles are fixed on the average of 9.0 × 10 ^{−6 to} 2.5 × 10 ⁻⁴ g / mm ² . Titanium or titanium alloy MIG welding wire with excellent arc stability.

(4) The cross-sectional outer diameter of the wire is 1.6
mm or more and 2.0 mm or less, The titanium or titanium alloy MIG welding wire excellent in arc stability as described in the above (1), (2) or (3).

(5) Titanium or titanium alloy MI excellent in arc stability according to any one of (1) to (4) above.
A method for MIG welding titanium or a titanium alloy, which comprises welding titanium or a titanium alloy using a G welding wire.

(6) In the MIG welding method for titanium or titanium alloy according to the above (5), the titanium or titanium alloy is welded with a pulse welding current satisfying the following current conditions. Welding method.

300A ≦ peak current ≦ 500A 2.0 ≦ peak current / base current ≦ 5.0

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail. FIG. 1 schematically shows the appearance of the MIG welding device.

A torch 2 for MIG welding is opposed to the material to be welded 1 and a welding wire 3 is fed by a wire feeding device (not shown), and a direct current pulse welding power source (not shown) is used.
An arc 4 is generated between the material 1 to be welded and the welding wire 3 to form a molten pool 5 in the material 1 to be welded.

Then, the welding torch 2 is moved in the direction of the arrow to form the welding bead 6. At this time, as shown in FIG. 1, the tip of the welding torch 3 and the rear of the welding arc 4 are also shielded by an inert gas such as Ar gas.

Titanium and titanium alloys are more likely to oxidize at a lower temperature than steel and the like. Therefore, if only the tip of the welding torch is gas shielded (steel is sufficient), the weld metal is oxidized and hardened. However, good elongation cannot be obtained.

Therefore, MIG of titanium and titanium alloys
In welding, a shield box 7 is attached to the rear of the welding torch 2 to shield the rear of the welding arc 4 with an inert gas such as Ar gas.

At this time, in order to uniformly supply the shield gas to the surface of the welding bead 6, a suitable number of gas outlets 9 are provided in the shield box 7 in parallel with the welding direction and on the side opposite to the welding bead. Arrange the pipe 8 and the gas outlet 9
A method is generally adopted in which the shield gas ejected from the above is first applied to the upper wall in the shield box and then applied to the lower welding bead 6.

FIG. 2 shows a welded material 1 having a groove 11 formed therein.
1 schematically shows a mode of forming the welding bead 6 in the case of welding with a MIG welding apparatus as shown in FIG.

The welding torch 2 is moved in the direction of the arrow (welding direction) to form the welding bead 6 behind the molten pool 5. At this time, normally, the welding arc 4 wanders, so that the welding bead 6 is relatively formed. Large spatter 12 adheres to the surface of the material to be welded and the surface of the weld bead.

FIG. 3 schematically shows the appearance of a welding bead formed by conventional MIG welding. The welding bead 6 meanders due to the wandering phenomenon, and a trace of the wandering phenomenon is left around the welding bead 6.

The degree of meandering of the weld bead is the meandering width of the bead. It is indicated by the shortest distance (mm) (Wb in the figure) from a straight line passing through the position 15 and parallel to the welding direction.

The meandering width of the bead is preferably about 0, but if it is difficult to set it to about 0 mm, it is tentatively 0.
Up to 6 mm is an acceptable range.

The traces of the wandering phenomenon are traces of the arc that has migrated to the outside of the weld bead start end portion when the wandering phenomenon occurs violently.

When the traces are hidden by the weld beads, there is no problem in appearance. However, when the traces are left outside the weld beads, the appearance of the material to be welded will naturally be impaired. Is.

The degree of the wandering phenomenon is defined by the width of this trace as the wandering phenomenon width, and the maximum distance (mm) from the beginning and end of the welding bead to the outermost position of the trace where the welding arc has moved by the wandering phenomenon. Indicated by value (W in the figure
w).

Since no trace of the wandering phenomenon should be left on the welded portion, the width Ww of the wandering phenomenon should be 0 mm. However, even if the welding conditions aiming at 0 mm are selected, the wandering phenomenon may occur severely and Ww may reach 2 to 3 mm.

Further, in FIG. 3, a relatively large spatter 12 is formed on the surface of the material to be welded and the surface of the weld bead.
Many are attached. Thus, the appearance of the welded portion formed by the conventional MIG welding is poor.

Therefore, the present inventor has diligently studied an improvement measure under the above-mentioned idea in order to improve the appearance shape of the welded portion.

As a result, in the MIG welding of titanium or a titanium alloy, the present inventors have found that a predetermined amount of Al or Al-containing particles having an average particle diameter of 0.1 to 100 μm adheres to the surface of the welding wire. When used, the Al oxide that acts as a cathode spot can be constantly and concentratedly formed on the surface of the material to be welded that is closest to the tip of the welding wire, and as a result, the welding arc is stable during welding. It has been found that a welding bead that can be maintained and continued for a long time, that the wandering phenomenon can be suppressed, the adhesion of spatter is extremely small, and that the appearance shape is extremely good can be obtained.

The MIG welding wire of the present invention (the wire of the present invention) is based on the above idea.

Here, the reason for defining the average particle size of Al or Al-containing particles as 0.1 to 100 μm is that if the average particle size is less than 0.1 μm, the amount of Al adhered to the surface of the welding wire will be small. As a result, the production amount of Al oxide is reduced and the stability of the welding arc is reduced.

When the stability of the welding arc is lowered, the width of the wandering phenomenon and the meandering width of the bead are increased, and it becomes impossible to obtain a welding bead having a good external shape.

On the other hand, when the average particle size exceeds 100 μm,
The unevenness on the surface of the welding wire becomes large, which increases the feeding resistance of the wire, and the feeding speed of the welding wire becomes unstable and the welding arc becomes unstable.

Further, buckling of the welding wire occurs in the conduit cable through which the wire is fed, cutting of the welding arc occurs, wear of the tip becomes large, and further, in the conduit cable, The surface of the conduit is rubbed against the inner wall of the conduit cable, and the surface thereof is scraped and accumulated in the tip to further increase the feeding resistance of the wire, which makes the welding arc more unstable.

Further, the present inventor, as described above,
Alternatively, if the amount of Al-containing substance adhered to the surface of the welding wire is adjusted, the amount of Al oxide that acts as a cathode spot can be adjusted to an appropriate range, and as a result, during welding, the welding arc
It has been found that the wandering phenomenon can be further suppressed by maintaining and continuing more stably.

According to the experimental results of the present inventor, the fixed amount of Al or Al-containing particles is 5.0 × 10 ^{−6 to} 1.0 × on average.
A range of 10 ⁻³ g / mm ² is preferred. If the amount of Al or Al-containing particles fixed is adjusted within this range, the welding arc will be further stabilized, the bead meandering width Wb ≈ 0, the wandering phenomenon width Ww ≈ 0, no spatter adhesion, and mechanical properties. It is possible to reliably obtain an excellent welded part.

The fixed amount of Al particles is 5.0 × 10 ⁻⁶ g on average.
If it is less than / mm ² , the production amount of Al oxide as a cathode spot may be insufficient and the welding arc may not be stable, and the above-mentioned adhesion amount may be 1.0 × 10 ⁻³ g / mm ^{2 or} less. If it exceeds, the welding arc will be extremely stable, but A
There is a case where a large amount of 1-l oxide remains and deteriorates the toughness of the welded portion.

The amount of adhered Al or Al-containing particles is in the range of 9.0 × 10 ^{−6 to} 2.5 × 10 ⁻⁴ g / mm ^{2 on} average, in that the welding arc is maintained and continued more stably. More preferable.

The Al or Al-containing particles may be fixed to the surface of the welding wire by any method as long as a predetermined amount of particles can be fixed. In the known method, a mechanical pressure bonding method or the like can be used, but the shot blast method is preferable because the amount of fixation can be easily adjusted.

The Al or Al-containing particles may be fixed to the surface of the welding wire during the feeding of the welding wire. For example, Al or Al-containing particles may be fixed to the surface of the welding wire by the shot blasting method immediately before charging the welding wire into the welding arc.

In FIG. 4, a pure titanium welding wire (wire of the present invention) having Al particles having an average particle size of 10 μm fixed on an average of 5.0 × 10 ⁻⁴ g / mm ² was used to form pure titanium (material to be welded). M
The appearance of the welding bead obtained by performing IG welding is shown typically.

As shown in the figure, the meandering width of the bead Wb≈0,
The width of the wandering phenomenon is Ww≈0, and there is no spatter adhesion.

Since the main purpose of the wire of the present invention is to stabilize the welding arc, the cross-sectional outer diameter of the wire is preferably 1.6 mm or more and 2.0 mm or less in order to further stabilize the welding arc. .

The inventors of the present invention have found that the MI of titanium and titanium alloys
We conducted extensive research into droplet transfer patterns in G welding, and on the low current side, the droplet became a globular and the droplets became large and spatter easily occurred. On the other hand, on the high current side,
It was clarified that the droplets are in a spray state and the droplets are small, which suppresses spatter.

Generally, in MIG welding, when the diameter of the welding wire is large, the maximum welding current is large and the selection range of the optimum welding conditions is widened as compared with the case where the diameter is small, and it is preferable that the welding current is constant. This is preferable in that the current density in the welding arc becomes smaller and the welding arc is stabilized, but increasing the diameter of the welding wire makes it possible to smoothly feed the wire and improve the appearance of the welding bead. There is a limit in maintaining and continuing.

Therefore, the present inventor further investigated the optimum range of the wire diameter capable of ensuring stable arc generation and continuation even at high current.

As a result, it was found that the cross-sectional outer diameter of the wire is preferably 1.6 mm or more and 2.0 mm or less. If the cross-sectional outer diameter of the wire is less than 1.6 mm, a high current cannot be passed, and there may be a limit to the suppression of spatter. On the other hand, if the cross-sectional outer diameter exceeds 2.0 mm, the wire feeding may be hindered and a weld bead having a good external appearance may not be obtained.

MIG welding method of the present invention (method of the present invention)
Welds titanium or a titanium alloy using the wire of the present invention. Therefore, according to the method of the present invention, the welding arc is extremely stabilized during welding, and a welded portion having an excellent external appearance shown in FIG. 4 can be obtained.

In the present invention, a DC welding power source or a DC pulse welding power source is used as the welding power source. In general,
It is known that when pulse welding current is used, droplet transfer at the time of welding is performed regularly and smoothly, but also in the method of the present invention, a peak current value and a base current value are calculated using a DC pulse welding power source. Experimental results have shown that the wandering width and / or the meandering width of the bead are further reduced when combined appropriately.

Regarding the relationship between the combination of the peak current value and the base current value and the appearance of the weld bead, the appearance of a weld bead having a wandering phenomenon width of approximately 0 mm and a bead meandering width of more than 0.2 mm and not more than 0.6 mm Weld bead (○) with good shape and wandering phenomenon width of about 0 m
FIG. 5 shows the results obtained by defining and arranging a weld bead having a m and a meandering width of 0.2 mm or less as a weld bead (⊚) having an “extremely good” external shape.

From FIG. 5, when the DC pulse welding power source of 300 A ≦ peak current ≦ 500 A 2.0 ≦ peak current / base current ≦ 5.0 is used, the welding arc is further stabilized and the appearance shape is extremely good. It turns out that a weld bead can be obtained.

Peak current is less than 300 A or 500
If A or more, or peak current / base current is 2.0
Even if it is less than or more than 5.0, the width of the wandering phenomenon and the meandering width of the bead become small, and a weld bead with a good appearance can be obtained, but under the above current conditions (see FIG. 5). When the method of the present invention is carried out, the welding arc is extremely stabilized during welding, and a weld bead having an extremely good external shape (see FIG. 4) can be obtained.

[0070]

EXAMPLES Examples of the present invention will be described below.
The conditions used in the examples are examples, and the present invention is not limited to the conditions.

Example 1 Pure titanium welding wire (wire diameter: 1.6 mm) and Al particles having an average particle size of 10 μm on the surface of the pure titanium welding wire were 5.0 × 10 ⁻⁴ g / mm ² on average.
Using a fixed pure titanium welding wire (wire diameter: 1.6 mm), MIG welding was performed under the welding conditions shown in Table 1, and the welding state and welded portion were observed and evaluated. The results are shown in Table 2.

[0072]

[Table 1]

[0073]

[Table 2]

From Table 2, when a pure titanium welding wire having Al particles fixed thereto is used, the arc is stabilized and the wandering phenomenon is reduced (the wandering phenomenon width Ww is approximately 0 m.
m), and the meandering width Wb of the weld bead was also reduced to less than 0.6 mm, and it can be seen that the weld bead having a good external shape was obtained.

On the other hand, when the pure titanium welding wire is used, the arc becomes unstable, the wandering phenomenon becomes large, the wandering phenomenon width reaches 10 mm, and the bead meandering width is also allowable. The appearance shape of the weld bead became poor beyond the possible 0.6 mm.

It should be noted that, although spatter adhesion is not shown in Table 2, it can be seen by visual observation that spatter adhesion is completely absent when the conditions relating to the Al particles are within the range of the present invention. confirmed.

Example 2 Shot blasting was performed using pure titanium welding wires having wire diameters of 1.2 mm and 1.6 mm, to which Al particles having an average particle diameter of 10 μm were fixed at 5.0 × 10 ⁻⁴ g / mm ^2. MIG welding was performed. Table 3 shows the appearance shape evaluation of the weld bead.

Compared with the case of using a pure titanium welding wire having a wire diameter of 1.2 mm, when the welding wire having a wire diameter of 1.6 mm is used, the wandering phenomenon of the arc is further suppressed and the width Ww of the wandering phenomenon is reduced. With the decrease, the meandering width Wb of the bead also decreases.

From this result, the welding wire diameter is φ1.6 m.
It is understood that when m is set, it is possible to generate a stable arc at a high current and obtain a weld bead having an extremely good appearance.

[0080]

[Table 3]

Example 3 The pure titanium welding wire having a wire diameter of 1.6 mm used in Example 2 was used, the DC pulse welding power source was used as the welding power source, and the welding conditions shown in Table 4 were used.
Within the range of the peak current of the pulse welding current of 250 to 550 A and the base current of 60 to 300 A, the respective current values were changed, MIG welding was performed, and the welded portion was observed and evaluated.

The results are shown in Table 5. In Table 5, Ww is the width of the wandering phenomenon, Wb is the meandering width of the bead, and Ww = 0.
Those with 02 mm <Wb ≤ 0.6 mm were evaluated as “good” and Ww
= 0.0≤Wb≤0.2 mm was evaluated as "extremely good".

[0083]

[Table 4]

[0084]

[Table 5]

From Table 5, the peak welding current is 300 to 50.
It can be seen that when the peak current / base current is 2.0 or more and 5.0 or less at 0 A, the width of the wandering phenomenon and the meandering width of the bead are significantly reduced, and a weld bead having an extremely good appearance is obtained. .

[0086]

According to the present invention, in the MIG welding of titanium or titanium alloy, the welding arc can be stabilized and the wandering phenomenon can be suppressed, so that the appearance of the welding bead is good and mechanically. It is possible to obtain a welded part without deterioration of characteristics.

Therefore, the present invention makes it possible to construct a large outdoor structure or an industrial machine structure with a titanium or titanium alloy structural material, and greatly contributes to the development of industry.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an appearance of a MIG welding device.

FIG. 2 is a diagram schematically showing a formation mode of a weld bead.

FIG. 3 is a diagram schematically showing the appearance of a weld bead obtained by conventional MIG welding.

FIG. 4 is a diagram schematically showing the appearance of a weld bead obtained by MIG welding according to the present invention.

FIG. 5 is a diagram showing a preferable range of pulse welding current in the present invention.

[Explanation of symbols]

1 ... Material to be welded 2 ... Welding torch 3 ... Welding wire 4 ... Welding arc 5 ... Welding pool 6 ... Weld beads 7 ... Shield box 8 ... Gas supply pipe 9 ... Gas outlet 10 ... Shield gas flow direction 11 ... groove 12 ... Spatter 13 ... Trace of wandering phenomenon Ww ... Wandering phenomenon width Wb ... Bead meander width

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B23K 103: 14 B23K 103: 14 (72) Inventor Taiji Hase 7-6-1 Higashi Narashino, Narashino City, Chiba Prefecture Nittetsu Welding Industry Co., Ltd. Uchi Nichiko Techno Service Co., Ltd. F term (reference) 4E001 BB08 CB04 DE04 EA01 EA05

Claims (6)

[Claims] 1. A titanium or titanium alloy wire used for MIG welding of titanium or a titanium alloy, wherein Al or Al-containing particles having an average particle diameter of 0.1 to 100 μm adhere to the surface of the wire. Titanium or titanium alloy MIG welding wire with excellent arc stability. 2. The average of the Al or Al-containing particles is 5.
The titanium or titanium alloy MIG welding wire excellent in arc stability according to claim 1, wherein the wire is fixed at 0 × 10 ^{−6 to} 1.0 × 10 ⁻³ g / mm ² . 3. The average of the Al or Al-containing particles is 9.
The titanium or titanium alloy MIG welding wire excellent in arc stability according to claim 1, wherein the wire is fixed at 0 × 10 ^{−6 to} 2.5 × 10 ⁻⁴ g / mm ² . 4. The cross-sectional outer diameter of the wire is 1.6 mm or more and 2.0 mm or less.
Or the wire for titanium or titanium alloy MIG welding excellent in arc stability according to item 3. 5. Titanium or a titanium alloy is welded using the titanium or titanium alloy MIG welding wire having excellent arc stability according to claim 1, or titanium. Titanium alloy MIG welding method. 6. The MIG welding method for titanium or a titanium alloy according to claim 5, wherein the titanium or titanium alloy is welded with a pulse welding current satisfying the following current conditions. . 300A ≦ peak current ≦ 500A 2.0 ≦ peak current / base current ≦ 5.0