JP2003320477A - Titanium or titanium alloy mig welding wire having good arc stability, and mig welding method of titanium or titanium alloy by using the wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method with stability and high efficiency for MIG welding titanium and titanium alloy capable of semiautomatically welding at the scene. <P>SOLUTION: The titanium or titanium alloy MIG welding wire comprises a titanium alloy containing, by mass, 0.5 to 10% Al, ≤1.0% O, and the remainder Ti with inevitable impurities, and has good arc stability and 1.6 to 2.0 mm of the outer diameter of the cross section. It is preferable that titanium or titanium alloy is MIG welded by a pulse welding current satisfying the following conditions; 300 A≤ the peak current ≤500 A and 2.0≤ the peak current/the 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]

The present inventor has noticed that 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. We have come to the idea that a welding arc can be stably maintained and continued if an oxide is formed on the surface of the material to be welded that is closest to.

As a result of earnestly studying the means for realizing this idea, the present inventor found that when a predetermined amount of Al was added to the welding wire, the Al was oxidized and transferred to the molten pool. It has been found that the Al oxide acts as a cathode spot and can stably maintain and continue the welding arc during welding.

The present invention has been made on the basis of the above findings in order to solve the above problems, and the gist thereof is as follows.

(1) In a wire used for MIG welding of titanium or a titanium alloy, the wire is Al: 0.5
A titanium or titanium alloy MIG welding wire having excellent arc stability, characterized by comprising -10% by mass, the balance Ti, and a titanium alloy containing unavoidable impurities.

(2) The titanium or titanium alloy MIG welding wire excellent in arc stability as described in (1) above, wherein the titanium alloy further contains O in an amount of 1.0% by mass or less. Titanium or titanium alloy MIG welding wire with excellent arc stability.

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

(4) Titanium or titanium alloy MI excellent in arc stability according to the above (1), (2) or (3).
A method for MIG welding titanium or a titanium alloy, which comprises welding titanium or a titanium alloy using a G welding wire.

(5) In the method of MIG welding titanium or titanium alloy according to (4), the titanium or titanium alloy is welded with a pulse welding current satisfying the following current conditions. MIG welding method.

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

[0025]

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), while 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, a suitable number of gas outlets 9 are provided in the shield box 7 parallel to the welding direction and on the side opposite to the welding beads so that the shielding gas is uniformly supplied to the surface of the welding beads 6. 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, due to the wandering phenomenon of the welding arc 4, it is relatively 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 defined by the bead meandering width, which is a straight line passing through the position 14 where the starting end of the welding bead is most recessed and parallel to the welding direction (arrow in the figure), and the starting end of the welding bead is the most protruding. 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 trace of the wandering phenomenon is a trace that is left from the welding bead when the arc moves to the outside of the starting end of the welding bead when the wandering phenomenon occurs violently.

If the trace is hidden by the weld bead, there is no problem in appearance, but if it remains outside the weld bead, it naturally damages the external appearance of the material to be welded and should not be left in the weld. 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 due to 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 of the wandering phenomenon should be Ww 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 welding bead.
Many are attached. Thus, the external shape of the weld bead formed by 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 weld bead.

As a result, the present inventors have found that in MIG welding of titanium or a titanium alloy, Al is 0.5 to 10% by mass.
If a welding wire containing Ti and an inevitable impurity titanium alloy is used, the welding arc will be stable and
It has been found that the wandering phenomenon does not occur, and as a result, it is possible to obtain a weld bead in which the adhesion of spatter is extremely small and the appearance shape is extremely good.

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

The reason for defining Al in the above titanium alloy as 0.5 to 10% by mass is that when Al is less than 0.5% by mass, the formation of the cathode spot becomes insufficient and the welding arc becomes stable. On the other hand, on the other hand, if it exceeds 10 mass%, a large amount of Al remains as Al oxide in the welded portion and deteriorates the toughness of the welded portion.

FIG. 4 schematically shows the appearance of a weld bead obtained by MIG welding pure titanium (material to be welded) using a pure titanium welding wire (wire of the present invention) containing 6% by mass of Al. Show. As shown in the figure, the bead meandering width Wb≈
0, the wandering phenomenon width Ww≈0, and no spatter adhered.

When the titanium alloy of the wire of the present invention contains 1.0 mass% or less of oxygen in addition to Al, the welding arc is further stabilized, and the bead meandering width Wb≈0, the wandering phenomenon width Ww≈0, and the spatter adhesion. It is possible to reliably obtain a welded portion having no mechanical properties and excellent mechanical properties.

In MIG welding of steel, it is known that when a required amount of oxidizing gas is added to the shield gas, the welding arc is stabilized and the spatter phenomenon is suppressed. Further, also in MIG welding of titanium or titanium alloy, as disclosed in Japanese Patent Laid-Open No. 2000-280076, adding a trace amount of oxidizing gas to the shield gas is effective in stabilizing the arc and suppressing the spatter phenomenon. It is known that there is. However, it is hard to say that the relationship between the amount of oxidizing gas, especially oxygen, and the stability of the welding arc and the reduction of the spattering phenomenon has been clarified.

[0048] Normally, oxygen penetrates from the welding arc atmosphere and remains in the welded portion. However, if the amount of oxygen increases, the strength of the welded portion will be excessively improved and the elongation will be small. It will be out of balance.

In the present invention, stabilization of the welding arc,
Also, to optimize the mechanical properties of the weld, O was 1.0
Specified as mass% or less.

In the wire of the present invention, the main purpose is to stabilize the welding arc. However, in order to further 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. .

The inventor of the present invention has found that 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 becomes large, the maximum welding current becomes large as compared with the case where it is small, which is preferable in that the range of selection of the optimum welding conditions is widened. This is preferable in that the welding current density in the arc becomes smaller and the welding arc is stabilized, but increasing the diameter of the welding wire allows the wire to be fed smoothly and the appearance shape of the welding bead to be improved. There is a limit in maintaining and continuing.

Therefore, the present inventor further investigated the optimum range of the wire diameter which can ensure the smooth feeding of the wire even with a large diameter and high current, and can ensure the stable generation and continuation of the arc.

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 flowed and spatter is limited, while if it exceeds 2.0 mm, the fluctuation of the wire speed causes the stability of the welding arc. It is not possible to obtain a weld bead with a good external shape, which greatly affects the

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

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 a pulse welding current is used, droplet transfer during welding is performed regularly and smoothly, but also in the method of the present invention, when a DC pulse welding power source is used, the wandering phenomenon width and Experimental results have shown that the meander width of the beads is / or is further reduced.

Further, according to the above experimental results, it was found that the welding arc was further stabilized by using the DC pulse welding power source of 300A ≦ peak current ≦ 500A 2.0 ≦ peak current / base current ≦ 5.0. did. FIG. 5 shows the welding current range according to the above current conditions.

In FIG. 5, the width of the wandering phenomenon is about 0.
mm, the bead meandering width is more than 0.2 mm and 0.6 mm or less, the weld bead has a good appearance, the wandering phenomenon width is about 0 mm, and the bead meandering width is 0.2 mm or less. It is a figure which shows the result of having arrange | positioned the welding bead with a favorable external appearance with a good welding bead, and the welding bead with a very good external appearance with ◎.

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 having a good external shape can be obtained, or 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.

[0060]

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) Welding shown in Table 1 using a pure titanium welding wire and a welding wire (wire diameter: 1.6 mm) in which Al is added in the range of 2 to 14 mass% to the pure titanium welding wire. MIG welding was performed under the conditions, and the welding state and welded portion were observed and evaluated. The results are shown in Table 2.

[0062]

[Table 1]

[0063]

[Table 2]

From Table 2, when the welding wire containing 2 to 10 mass% of Al is used, the arc is stabilized and the wandering phenomenon is reduced (the width of the wandering phenomenon is 3.2 mm or less), and It can be seen that the meandering width of the weld bead was also reduced, and a weld bead with a good appearance was obtained.

However, pure titanium welding wire or Al
If a welding wire added in excess of 0 mass% is used, the arc becomes unstable and the wandering phenomenon becomes large (the width of the wandering phenomenon is 8 mm or more), and the wandering occurs outside the welding bead start end. Traces of the phenomenon remain,
The meandering width of the weld bead also increased (2 mm or more), and the appearance of the weld bead became poor.

It should be noted that although Table 2 does not show the state of adhesion of spatter, it is visually observed that 2-10 mass% of Al is contained.
It was confirmed that when the contained welding wire was used, the adhesion of spatter was extremely reduced.

(Example 2) In Table 3, wire diameters of 1.2 mm and 1.6 mm obtained by adding 6 wt% of Al to a pure titanium welding wire.
The appearance shape evaluation of the welding bead when MIG welding is performed using the welding wire of FIG. Wire diameter 1.2mm
When using a welding wire with a wire diameter of 1.6 mm, the wandering phenomenon of the arc is further suppressed, the wandering phenomenon width Ww is reduced, and the meandering width Wb of the bead is is decreasing.

From this result, the welding wire diameter is 1.6 mm.
It is understood that, by setting the above, it is possible to generate a stable arc at a high current and obtain a weld bead having an extremely good appearance.

[0069]

[Table 3]

Example 3 A pure titanium welding wire having a wire diameter of 1.6 mm in which 6 wt% of Al was added was used, and a DC pulse welding power source was used as a welding power source.
Under the welding conditions shown in, the peak current of the pulse welding current is 250
.About.550 A and base current 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 =
Those having 0.0 ≦ Wb ≦ 0.2 mm were evaluated as “extremely good”.

[0072]

[Table 4]

[0073]

[Table 5]

From Table 5, the peak welding current is 300 to 50.
0 A, and the peak current / base current is 2.0 to 5.
It can be seen that in the range of 0, the width of the wandering phenomenon and the meandering width of the bead are greatly reduced, and the appearance of the weld bead is extremely good.

[0075]

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 industrial development.

[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

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Taiji Hase             7-6-1 Higashi Narashino, Narashino City, Chiba Prefecture             Welding Industry Co., Ltd.             Within the corporation F-term (reference) 4E001 AA03 BB08 CB04 DE04 EA05

Claims (5)

[Claims] 1. A wire used for MIG welding of titanium or a titanium alloy, wherein the wire is Al: 0.5 to 10
A titanium or titanium alloy MIG welding wire excellent in arc stability, which is made of a titanium alloy having a mass%, balance Ti and unavoidable impurities. 2. The titanium or titanium alloy MIG welding wire excellent in arc stability according to claim 1, wherein the titanium alloy further contains O in an amount of 1.0% by mass or less. Titanium or titanium alloy MIG welding wire with excellent properties. 3. The titanium or titanium alloy MIG welding wire excellent in arc stability according to claim 1 or 2, wherein the wire has a cross-sectional outer diameter of 1.6 mm or more and 2.0 mm or more.
A titanium or titanium alloy MIG welding wire excellent in arc stability, characterized in that: 4. Titanium or a titanium alloy is welded using the titanium or titanium alloy MIG welding wire excellent in arc stability according to claim 1, 2 or 3. MIG welding method. 5. The MIG welding method of titanium or a titanium alloy according to claim 4, wherein the titanium or the titanium alloy is welded with a pulse welding current satisfying the following current conditions. Method. 300A ≦ peak current ≦ 500A 2.0 ≦ peak current / base current ≦ 5.0