JP2004066304A - Method of mig welding of titanium or titanium alloy, and deposited metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable site welding of titanium or titanium alloy by semi-automatic welding consistently at high efficiency by using a MIG welding method, and to provide a titanium or titanium alloy MIG welding method for reducing a cost through reduction of the shield gas consumption by shortening the welding time. <P>SOLUTION: In the titanium or titanium alloy MIG welding, a titanium alloy wire having a composition consisting of, by mass, 0.5 to 10% Al and ≤ 1.0% O as necessary, and the balance titanium with inevitable impurities and the outer diameter of the wire section of ≥ 1.6 mm and ≤ 2.0 mm is used as a welding wire. In the MIG welding, a titanium base metal or a titanium alloy base metal is welded by the AC pulse welding current satisfying conditions that 200A ≤ peak current of positive polarity ≤ 500A, -50A ≤ peak current of negative polarity, and 1.0 ≤ peak current of positive polarity/peak current of negative polarity as the current conditions. The MIG welding of titanium or titanium alloy with excellent bead shape is performed by suppressing a wandering phenomenon. <P>COPYRIGHT: (C)2004,JPO

Description

【００１７】
【表２】

【００１８】
なお、表２において、ワンダリング現象幅とは、ワンダリング現象によりアークが不安定となってワンダリング現象が大きくなり、溶接ビード始端部の外側にワンダリング現象の痕跡が残る幅をいい、溶接ビード蛇行幅とは、溶接ビード始端部が最も凹んでいる位置を通って溶接方向に平行な直線と、溶接ビード始端部が最も出っ張っている位置を通って溶接方向に平行な直線との最短距離をいう。（図１参照）
【００１９】
【発明の効果】
以上述べたように、本発明は、チタン又はチタン合金をＭＩＧ溶接方法を用いて、安定、かつ高能率に、かつ半自動溶接による現場溶接を可能とし、溶接時間短縮によるシールドガス使用量低減によるコスト削減を図ったＭＩＧ溶接用チタン合金溶接ワイヤ、溶接方法および溶接金属の提供を可能にする。
【図面の簡単な説明】
【図１】ＭＩＧ溶接装置の外観模式図。
【図２】ＭＩＧ溶接法の外観模式図。
【図３】従来のＭＩＧ溶接による溶接ビードの平面模式図。
【図４】本発明によるＭＩＧ溶接による溶接ビードの平面模式図。
【図５】パルス溶接時の適正溶接電流範囲を示す図。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a titanium alloy welding wire for MIG welding used when welding titanium or a titanium alloy member used for ships, building structures, and the like.
[0002]
[Prior art]
BACKGROUND ART Conventionally, titanium or a titanium alloy has been used for ships, building structures, automobiles, motorcycles, and the like that require high corrosion resistance, and the use of titanium or titanium alloy has been increasing recently. At the time of welding titanium or a titanium alloy, at present, a TIG welding method (tungsten inert gas metal welding method), which is one of the non-consumable electrode welding methods, is mainly employed. On the other hand, the MIG welding method (inert gas metal arc welding method), which is a consumable electrode welding method, has an advantage that a welding efficiency several times or more can be obtained as compared with the TIG welding method, but is made of pure titanium. When MIG welding is performed using a welding wire, a welding arc becomes extremely unstable. This is because when the titanium and the titanium alloy are welded by the MIG welding method, the arc is violently moved to a position where the surface oxide film of the material to be welded of the titanium and the titanium alloy remains so as to maintain the cathode spot. Since the wandering phenomenon occurs, a large amount of welding spatter is generated, and the spatter adheres to titanium and a titanium alloy as base materials. In addition, there is a problem that the weld bead meanders due to the wandering phenomenon, and poor appearance of the welded portion frequently occurs. For this reason, the danger of welding titanium and titanium alloy by the MIG welding method has been avoided as much as possible.
[0003]
On the other hand, when the TIG welding method is employed, an arc is generated using a non-consumable electrode having a high melting point, and a sputter is performed to perform welding while supplying a welding wire to a molten pool formed in the base material. No occurrence. In addition, since the electrode side has a negative polarity and the welded side has a positive polarity, the above-described wandering phenomenon does not occur because there is a cleaning action for removing an oxide film generated on the surface of the material to be welded. The bead does not meander, and a good weld appearance shape is obtained. For this reason, when welding titanium and a titanium alloy, the TIG welding method has been exclusively used.
[0004]
In TIG welding, it is necessary to hold a welding wire at an appropriate position while holding a welding torch at an appropriate position. For this reason, it is good to be able to prepare a device that can hold the welding torch and the welding wire in appropriate positions at a factory, etc. The burden on the welding operator cannot be imagined because it must be moved as the welding progresses while holding the wire and the like at an appropriate position. Further, a device incorporating a guide device for feeding a welding wire into a welding torch is extremely expensive as compared with a semi-automatic welding torch for MIG welding. In addition, TIG welding has a problem that welding time is long because welding heat input is smaller than MIG welding, and therefore welding efficiency is poor. Further, since the welding time is long, a large amount of gas is used as the shielding gas, which increases the cost.
[0005]
For example, Japanese Patent Publication No. 59-226159 discloses that two titanium strips forming a working structure are abutted with each other in a longitudinal direction, and the base material in the vicinity of the welded portion is softened and annealed by TIG welding to be broken. There is disclosed a method of connecting a titanium strip without any. As described above, conventionally, when welding a titanium strip, welding is performed exclusively by the TIG welding method. In Japanese Patent Publication No. 12-28076, there is disclosed a shield gas obtained by adding a trace amount of an oxidizing gas to an inert gas, and a titanium or titanium alloy to be welded by supplying a pulse welding current using a consumable electrode of titanium or a titanium alloy. An arc welding method for a titanium alloy is disclosed. However, supplying oxygen or oxide from the shielding gas not only stabilizes the welding arc, but also causes a large amount of oxygen to be mixed into the weld metal, causing the weld to harden and reduce mechanical properties such as reduced elongation. Will be degraded.
[0006]
On the other hand, for MIG welding using an alternating current, for example, a technique is known in which an alternating current of 200 to 400 A is applied to manually weld a workpiece such as a titanium material in a closed chamber filled with an inert gas. It is disclosed in JP-A-63-101779. Further, as an AC arc welding method, there is a method of alternately repeating positive polarity welding and reverse polarity welding. However, the ratio of the positive polarity period to the reverse polarity period is so difficult that it has not been put to practical use. Therefore, a means for applying a DC voltage between the consumable electrode and the base material and inverting the polarity of the consumable electrode to form an arc has been proposed. MIG welding has not been put to practical use.
[0007]
[Problems to be solved by the invention]
In view of the above-mentioned problems of the prior art, the present invention makes it possible to stably and efficiently perform on-site welding of titanium or a titanium alloy by AC current in MIG welding by semi-automatic welding, and to use a shielding gas by shortening welding time. It is an object of the present invention to provide a method for MIG welding titanium or a titanium alloy and a weld metal, in which cost is reduced by reducing the amount.
[0008]
[Means for Solving the Problems]
The present invention has been made in order to solve the above-mentioned problems, and the gist of the present invention is to provide a MIG welding method for titanium or a titanium alloy, the composition of a welding wire having a cross-sectional outer diameter of preferably 1.6 mm or more and 2.0 mm or less. However, in the case of MIG welding, an AC pulse that satisfies the following current conditions using a titanium alloy wire containing Al: 0.5 to 10% by mass, preferably O ≦ 1.0% by mass, the balance being titanium and unavoidable impurities. A titanium or titanium alloy MIG welding method, comprising welding a titanium base material or a titanium alloy base material with a welding current;
200A ≦ Positive peak current ≦ 500A
−50 A ≦ peak current of negative polarity 1.0 ≦ peak current of positive polarity / peak current of negative polarity Also, in the present invention, the composition of the deposited metal obtained by the above-described welding method is Al: 0.5 to 10 mass %, O ≦ 1.0% by mass, the balance being titanium and inevitable impurities.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
First, a welding device used for MIG welding will be described with reference to FIG. In FIG. 1, a welding wire 3 is provided at a center of a workpiece 1 to be welded, and a shielding gas 4 supplied from a shielding gas supply device 3 separately provided on the outer periphery of the welding wire 3 is injected toward a molten ground 5. A MIG welding torch 2 having an injection port is arranged, and a welding current is applied to perform a welding operation to form a welding bead 6. Generally, titanium or a titanium alloy is easily oxidized at a lower temperature than steel or the like, and in a gas shield having only a welding torch tip used for steel, the weld metal is oxidized and hardened, and good elongation of the weld metal cannot be obtained. Therefore, a shield box is provided behind the welding torch immediately after welding, and the rear of the welding arc point is also shielded with an inert gas such as Ar gas. The shield gas supply device 3 used in the present invention once takes in the shield gas supplied from the shield gas supply pipe 3-1 into the shield box 3-2, and in this shield box 3-2, the shield gas is supplied with a welding bead. The gas supply pipe 3-3 is arranged in parallel with the welding direction so as to be uniformly supplied to the surface of the welding bead 6, and a plurality of gas outlets 3-4 are provided at the outlet opposite to the welding bead 6, and the gas is injected from the gas outlet. A method is adopted in which the shielding gas 4 'is applied to the upper wall of the shield box 3-2 and then to the welding bead 6 on the lower surface.
[0010]
FIG. 2 shows the state of spatter scattering due to the wandering phenomenon when MIG welding is performed by the conventional method, and FIG. 3 is a schematic view of the appearance of a weld bead. As shown in FIG. 2, in the conventional MIG welding of titanium and a titanium alloy, the arc is extremely unstable because the arc maintains a cathode point, and the arc is located at a position where the surface oxide film of the material to be welded remains. A large amount of welding spatter is generated due to the wandering phenomenon, which violently moves and violates, and spatter 7 scatters and adheres to the surface of the base material. Further, as shown in FIG. 3, in addition to the scattering and adhesion of the above-mentioned spatter, the weld bead meanders due to the wandering phenomenon, resulting in poor appearance of the welded portion and reduced strength of the weld metal. In FIG. 3, when the wandering phenomenon occurs, a trace that the arc has moved in the direction of the undulation width due to the wandering phenomenon remains outside the weld bead starting end portion, resulting in an extremely poor weld bead shape.
[0011]
On the other hand, in gas shielded arc welding, the DC MIG welding method using a torch (rod) plus has a cleaning action of removing an oxide film on the surface of a base material, but the cleaning action is too large to increase wandering phenomenon. At the same heat input, there is a drawback that the penetration is deeper and the amount of deposited metal is smaller than that of the torch minus. In addition, AC MIG welding has both torch plus and torch minus. The former has a cleaning effect of the base material, and the latter suppresses the cleaning operation of the base material, and has the advantage of reducing the wandering phenomenon. There is an advantage that the penetration becomes shallower and the amount of deposited metal becomes larger than that of the plus. In particular, this AC MIG welding has the advantage that it is difficult to cause burn-through when welding a thin plate. There is a disadvantage of doing so.
[0012]
The above-described cleaning operation of the base material will be described in detail. The cleaning action of the base material occurs with the torch plus polarity, but not with the torch minus polarity. Generally, at the time of welding an aluminum material, an oxide film (Al ₂ O ₃ ) having a small electric conductivity existing on the surface is removed to stabilize an arc, and it becomes difficult for oxygen to enter a weld metal, so that joint characteristics are improved. . On the other hand, TIG welding of a titanium material has the same effect as the aluminum material described above. However, in MIG welding of a titanium material, a large welding current is used, so that the cleaning action also increases, and a wandering phenomenon occurs. Therefore, by performing MIG welding using alternating current, the wandering phenomenon can be suppressed, and an excellent bead shape can be obtained.
[0013]
Therefore, based on the above findings, the present invention provides a MIG welding method for titanium or a titanium alloy in which the composition of the welding wire contains Al: 0.5 to 10% by mass, and if necessary, O ≦ 1.0% by mass. , A titanium alloy wire having a cross-sectional outer diameter of 1.6 mm or more and 2.0 mm or less consisting of titanium and unavoidable impurities is used.
200A ≦ Positive peak current ≦ 500A
The wandering phenomenon is caused by welding a titanium base material or a titanium alloy base material with an AC pulse welding current satisfying a condition of −50 A ≦ peak current of negative polarity 1.0 ≦ peak current of positive polarity / peak current of negative polarity. And MIG welding of titanium or titanium alloy having an excellent bead shape has become possible.
[0014]
When titanium or a titanium alloy is subjected to MIG welding by using such a welding wire and employing the welding conditions specified above, the composition of the welded portion of titanium or titanium alloy is expressed as Al: 0.1% by mass%. It is possible to obtain a weld metal that is 5 to 10%, O: 0 to 1.0%, and the balance titanium.
[0015]
【Example】
As a material to be welded, a pure titanium material having a V groove (90 °) with a plate thickness of 12.7 mm is used. As an AC pulse welding current, a positive peak welding current value of 150 to 550 A and a negative peak welding current value of MIG welding with a welding wire having a cross-sectional outer diameter of 1.2 mmφ and 1.6 mmφ using Ar gas with a welding speed of 100 cm / min and a flow rate of 25 l / min as a shielding gas while varying the range from −30 to −550 A Was done. Table 1 shows the AC pulse welding current and bead appearance evaluation used in the present invention. As can be seen from Table 1, an excellent bead appearance can be obtained by appropriately selecting the values of the positive peak welding current and the negative peak welding current, or their ratio. Table 2 shows the results of the welding wire diameter, the welding state, and the appearance evaluation. As can be seen from Table 2, the use of a welding wire having a positive peak welding current, a negative peak welding current value, and a diameter of 1.6 mm or more and 2.0 mm or less as defined in the present invention was excellent. A bead appearance can be obtained.
[0016]
[Table 1]

[0017]
[Table 2]

[0018]
In Table 2, the wandering phenomenon width means a width in which an arc becomes unstable due to the wandering phenomenon, the wandering phenomenon becomes large, and a trace of the wandering phenomenon remains outside the weld bead starting end. The meandering width of the bead is the shortest distance between a straight line parallel to the welding direction through the position where the weld bead start end is most concave and a straight line parallel to the weld direction through the position where the weld bead start end protrudes most. Say. (See Fig. 1)
[0019]
【The invention's effect】
As described above, the present invention makes it possible to stably and efficiently perform on-site welding of titanium or a titanium alloy by using a MIG welding method by semi-automatic welding, and to reduce costs by reducing the amount of shielding gas used by shortening welding time. It is possible to provide a titanium alloy welding wire for MIG welding, a welding method, and a weld metal which are reduced.
[Brief description of the drawings]
FIG. 1 is a schematic external view of a MIG welding apparatus.
FIG. 2 is a schematic external view of the MIG welding method.
FIG. 3 is a schematic plan view of a conventional weld bead formed by MIG welding.
FIG. 4 is a schematic plan view of a weld bead by MIG welding according to the present invention.
FIG. 5 is a diagram showing an appropriate welding current range during pulse welding.

Claims (4)

In the MIG welding method of titanium or a titanium alloy, the composition of the welding wire uses a titanium alloy wire composed of 0.5 to 10% by mass of Al, the balance of titanium and unavoidable impurities, and satisfies the following current conditions in the MIG welding. A titanium or titanium alloy MIG welding method characterized by welding a titanium base material or a titanium alloy base material with an alternating pulse welding current.
200A ≦ Positive peak current ≦ 500A
−50 A ≦ peak current of negative polarity 1.0 ≦ peak current of positive polarity / peak current of negative polarity The MIG welding method for titanium or titanium alloy according to claim 1, wherein the titanium alloy wire further contains O ≦ 1.0% by mass. The MIG welding method for titanium or titanium alloy according to claim 1 or 2, wherein a cross-sectional outer diameter of the titanium alloy wire is 1.6 mm or more and 2.0 mm or less. A weld metal having a composition of the weld metal welded by the welding method according to any one of claims 1 to 3 comprising Al: 0.5 to 10% by mass, O ≦ 1.0% by mass, the balance being titanium and unavoidable impurities.

Images