JP2003320459A - Method for mig welding titanium and titanium alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for MIG welding which can stably and efficiently weld titanium and a titanium alloy. <P>SOLUTION: The method for MIG welding the titanium and the titanium alloy comprises a step of welding a titanium base material or a titanium alloy base material preferably containing Al of 10 mass% or less by a pulse welding current for satisfying the current conditions of 300 A≤(peak current)≤500 A, 0≤(peak current)/(base current)≤5.0 by using a pure titanium welding wire or a titanium alloy welding wire (preferably a sectional outer diameter of 1.6 to 2.0 mm). <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 an M excellent in arc stability used for MIG welding of titanium or titanium alloy structural materials in the field of structures such as ships and building structures.
IG welding method and M welded by the MIG welding method
IG welded titanium or titanium alloy structure.

[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 is to provide a G welding method.

[0016]

[Means for solving the problems] If the welding arc is stably maintained and continued, the wandering phenomenon can be suppressed.
The present inventor diligently researched and investigated a current condition under which a welding arc can be stably maintained and continued.

The present invention was made on the basis of the results of the above-mentioned research and investigation, and the gist thereof is as follows.

(1) MIG of titanium or titanium alloy characterized in that a pure titanium welding wire or a titanium alloy welding wire is used to weld a titanium base material or a titanium alloy base material with a pulse welding current satisfying the following current conditions. Welding method.

300A ≦ peak current ≦ 500A 2.0 ≦ peak current / base current ≦ 5.0 (2) When the cross-sectional outer diameter of the pure titanium welding wire or titanium alloy welding wire is 1.6 mm or more and 2.0 mm or less. The method of MIG welding titanium or titanium alloy according to the above (1), wherein the method is MIG welding.

(3) Of the welding wire and the base material,
At least the base material contains Al in an amount of 0.5% by mass or more and 4.0.
% Or less, the MIG welding method for titanium or titanium alloy according to the above (1) or (2).

[0021]

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 made to face 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, 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 the meandering width of the bead, and the 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 are 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 Wb of the bead is preferably about 0 mm, but if it is difficult to set it to about 0 mm, it can be allowed up to 0.6 mm.

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 portion of the welding bead when the wandering phenomenon occurs violently.

If these traces are hidden by the weld beads, there is no problem in appearance, but if they remain outside the weld beads, the appearance of the material to be welded will naturally be impaired 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 weld 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 in 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 occurs severely, and Ww is 2 to 3 m.
It may reach m.

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 external shape of the weld bead formed by conventional MIG welding is poor.

It is generally known that when a pulse welding current is used, droplet transfer during welding is performed regularly and smoothly.

Therefore, the present inventor investigated the relationship between the welding current condition and the wandering phenomenon width and / or the meandering width of the bead by using a DC pulse welding power source in MIG welding using a pure titanium welding wire. Wandering phenomenon Weld beads with a width of approximately 0 mm and a meandering width of 0.6 mm or less are weld beads with a good appearance, and other weld beads with a poor appearance. Weld beads with a good appearance are indicated by ○ and poor appearance. The results of arranging the weld beads by x are shown in FIG.

That is, the welding arc is stable under the current condition of 300 A ≦ peak current ≦ 500 A 2.0 ≦ peak current / base current ≦ 5.0, the wandering phenomenon width becomes approximately 0 mm, and the bead meandering width is allowable. It turns out that it can fit within 0.6mm.

Peak current is less than 300 A or 500
When it is more than A, the width of the wandering phenomenon and the meandering width of the bead become large even if the base current is in the range of 60 to 250 A, and the external shape of the weld bead becomes defective (see FIG. 3).

The base current is less than 60 A, or 2
If it exceeds 50 A, even if the peak current is in the range of 300 to 500 A, the width of the wandering phenomenon and the meandering width of the bead are similarly large, and the appearance shape of the weld bead becomes defective (see FIG. 3).

Further, even if the peak current and the base current are within the above-mentioned proper ranges, respectively, if the peak current / base current is less than 2.0 or more than 5.0 as shown in FIG. In addition, the width of the wandering phenomenon and the meandering width of the bead become large, and the external shape of the weld bead becomes defective (see FIG. 3).

In FIG. 4, pure titanium (material to be welded) was MIG in accordance with the current conditions of the present invention using a pure titanium welding wire.
The external shape of the weld bead obtained when welding is shown typically. As shown in the figure, the meandering width of the bead Wb≈0, the width of the wandering phenomenon Ww≈0, and no spatter adheres.

The pure titanium welding wire or titanium alloy welding wire used under the above current conditions of the present invention preferably has a wire cross-sectional outer diameter of 1.6 mm or more and 2.0 mm or less.

The inventor of the present invention has found that the MI of titanium and titanium alloys.
We investigated and investigated the droplet transfer form in G welding, and on the low current side, it became a globular and the droplets became large, and spatter easily occurred, while 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, it is preferable to increase the diameter of the welding wire in order to increase the maximum welding current and to widen the selection range of the optimum welding conditions as compared with the case where the welding wire is small. If constant, the welding current density in the arc becomes small, it is preferable in that the welding arc is stabilized, but increasing the diameter of the welding wire has a limit in terms of smooth feeding of the wire, The present inventor has further investigated the optimum range of the wire diameter that can secure the smooth feeding of the welding wire even at a 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, the welding current density in the arc becomes large and the welding arc becomes unstable, resulting in a poor bead appearance. On the other hand, if the cross-sectional outer diameter of the wire exceeds 2.0 mm, fluctuations in the feed rate of the welding wire have a large effect on the welding arc, which is not preferable.

According to the MIG welding method of the present invention (the method of the present invention), since the welding arc can be stabilized, the weld bead having a good appearance shown in FIG. 4 can be obtained. (Titanium or titanium alloy) contains 10 Al
When the content is less than or equal to mass%, the welding arc becomes more stable, and a welding bead having a better appearance can be obtained.

It is considered that this is because during welding, Al in the material to be welded is combined with oxygen in the arc to form an Al oxide that acts as a cathode spot. In order to obtain this effect, the Al content in the material to be welded is preferably 0.5 mass% or more. On the other hand, it is more preferable from the viewpoint of stabilizing the arc, but 4.0 mass%. If it exceeds 0.1%, Al excessively remains in the weld bead and deteriorates the mechanical properties of the welded portion, so 4.0% by mass or less is preferable.

[0050]

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) Using a pure titanium welding wire having a wire diameter of 1.6 mm, under the welding conditions shown in Table 1, within the peak current of pulse welding current of 250 to 550 A and the base current of 60 to 300 A. The current value was changed, MIG welding was performed, and the welded portion was observed and evaluated.

The results are shown in Table 2. In Table 2, Ww
Is the width of the wandering phenomenon, and Wb is the meandering width of the bead.

[0053]

[Table 1]

[0054]

[Table 2]

From Table 2, the peak welding current is 300 to 50.
0A and 2.0 ≦ peak current / base current ≦ 5.0
At the wandering phenomenon width Ww and the bead meandering width Wb
It can be seen that the welded bead has a good outer shape.

(Example 2) In Table 3, the wire diameter is 0.8 mm,
Using pure titanium welding wire of 1.2mm, φ1.6mm and 2.0mm, peak current 500A, base current 150
A shows the appearance evaluation of the welded portion when MIG welding was performed at a welding speed of 100 cm / min. Wire diameter 0.8mm
When using the welding wires with wire diameters of 1.6 mm and 2.0 mm, the wandering phenomenon is further suppressed, and the phenomenon width Ww and bead meandering width Wb are It is decreasing more.

From this result, the wire diameter is 1.6 to 2.0.
It is understood that, when a welding wire of mm is used, a stable arc can be maintained and continued at a high current, and a welding bead having an extremely good appearance shape can be obtained.

[0058]

[Table 3]

(Example 3) A material to be welded containing no Al,
A material to be welded containing Al in an amount of 0.5 to 10.0 mass% was welded at a peak current of 500 A, a base current of 150 A and a welding speed of 100 cm / min, and the appearance of the welded portion was observed and evaluated.

The results are shown in Table 4.

[0061]

[Table 4]

From this table, it is possible to obtain a weld bead having a good external appearance by containing 10 mass% or less of Al in the material to be welded. In particular, 0.5 to 4.0 mass% of Al is used. %, It is understood that a weld bead having an extremely good appearance can be obtained.

[0063]

According to the present invention, in MIG welding of titanium or titanium alloy, the welding arc is stabilized to suppress the wandering phenomenon, and the appearance of the welding bead is good.
In addition, it is possible to obtain a welded part without deterioration of mechanical properties.

Therefore, the present invention makes it possible to efficiently 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

   ─────────────────────────────────────────────────── ─── 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 BB08 CB04 DE04 EA01 EA04                       EA05

Claims (3)

[Claims] 1. A MIG welding of titanium or a titanium alloy, wherein a pure titanium welding wire or a titanium alloy welding wire is used to weld a titanium base material or a titanium alloy base material with a pulse welding current satisfying the following current conditions. Method. 300A ≦ peak current ≦ 500A 2.0 ≦ peak current / base current ≦ 5.0 2. The MIG welding method for titanium or titanium alloy according to claim 1, wherein the pure titanium welding wire or the titanium alloy welding wire has a cross-sectional outer diameter of 1.6 mm or more and 2.0 mm or less. . 3. The welding wire and the base material, wherein at least the base material contains Al in an amount of 0.5% or more and 4.0% or less by mass%. MIG welding method for titanium or titanium alloys.