KR20180098496A - Electro gas arc welding method and electro gas arc welding apparatus - Google Patents

Abstract

Provided are an electro gas arc welding method and an electro gas arc welding apparatus, which can make welding speeds fast without deterioration in welding work and improving mechanical properties of welded metal by securing toughness of welding heat-affected zone. For the electro gas arc welding, torch front ends of a single or a plurality of welding torches (21, 23) are inserted into grooves (11) of a pair of welded plates (15A, 15B), electric current for welding is applied through a power cable with length of 3m or more, and butt welding is carried out under a shield gas condition. A flux cored wire having a flux rate of 15 to 30% is used for the welding wires (25, 26), and gas with CO2 density of 50% or more is used for shield gas, and pulse current is used for the electric current for welding. For the pulse current, rising time till the pulse current reaches a peak current value is 0.1 to 5.0 ms, and frequency of pulse is 20 to 200 Hz.

Description

ELECTROGAS ARC WELDING METHOD AND ELECTROGAS ARC WELDING APPARATUS [0001]

The present invention relates to an electrogas arc welding method and an electrogas arc welding apparatus.

Generally, electrogas arc welding is known as a method of welding a steel sheet or the like (see Patent Documents 1 and 2). In such an electrogas arc welding, the end portions of the pair of welded plates are disposed so as to oppose each other in the upward and downward directions, and the sliding plate is brought into contact with the surface side of the welded plate on which the improvement is made. Further, a fixed disposable material is brought into contact with the back side. Then, a shielding gas is supplied between the sliding plate and the disassembly member, and the periphery of the welding wire fed to the tip of the welding torch is set as a shielding gas atmosphere. In this state, an arc is generated between the welding wire and the welded plate, and the sliding plate is slid upward while melting the welding wire. Thereby, a pair of welded plates are welded together in a standing posture.

The above-mentioned electrogas arc welding is employed in a wide range of fields such as ships, petroleum storage tanks, and bridges, since high efficiency welding is achieved compared to other welding methods. Particularly, in the ship sector, electrogas arc welding is also applied to the welding of a very thick plate having a plate thickness of 45 mm or more such as a sheer strake and a hatch coaming portion of a container ship.

Patent Document 1 discloses a one-electrode electro-arc arc welding method in which two steel plates having a thickness of 45 to 75 mm are opposed to each other and one of them is subjected to one-way welding with one welding wire, Is less than 2 mm, the projection length of the welding wire is 70 mm or more, and the heat input per improvement volume is 16 to 27 k / cm 3. Further, in a two-electrode electrogas arc welding method in which two steel plates having a plate thickness of 65 to 95 mm are opposed to each other and these are subjected to one-pass inward facing welding with two welding wires, A welding method in which the protruding length of at least one welding wire is 70 mm or more and the heat input per improvement volume is 15 to 24 kJ / cm3 is described.

In the welding method of Patent Document 2, a hot wire for increasing the amount of welding is directly supplied to the melting paper in order to reduce the heat input. In this case, the welding apparatus is constituted by a welding power source, a welding wire feeding device, an electrode torch, and a welding wire, in which the polarization of the welding power source is connected to the electrode torch and the other pole is connected to the welding target. As a hot-wire supplying mechanism for increasing the amount of welding, a configuration comprising an energizing heating power source, a hot-wire feeding device, a current-carrying torch, and a hot wire is disposed independently of the welding device. In such a configuration, a hot wire is fed between a welding wire which generates an arc and forms a fusing paper, and an improved surface of the welded plate, through a hot wire feeding device and a conductive torch.

Japanese Patent Application Laid-Open No. 2008-30044 Japanese Patent Application Laid-Open No. 2007-237263

However, recent tendency toward enlargement of the ship is remarkable, and the plate thickness of the steel sheet to be applied to the welded plate continues to increase with it. Therefore, when the welded plate is thickened, it is necessary to prevent occurrence of welding defects such as a case where the welding amount of the welding wire is insufficient, or a welding failure of the welding material or the welded plate occurs.

The heat input (welding heat input [kJ / mm]) per the welding unit length by the above-mentioned electrogas arc welding is obtained by dividing the amount of heat input from the welding wire (welding current x welding voltage) by the welding speed. Therefore, when the amount of heat input is constant, the thickness of the plate to be welded increases, the welding speed decreases, and the heat input to the welding increases.

If the heat input to the welding is increased, the time for exposing the welded plate to high temperature becomes longer, and the cooling rate of the welded plate and the welded joint exposed to a high temperature is lowered. For this reason, a welded heat affected zone (HAZ: Heat-Affected Zone), which is a zone where the structure is softened under the influence of welding heat, is generated on the welded plate after welding, and necessary joint characteristics are not obtained in this zone. In recent years, a high strength material having a YP (Yield Point) of 390 N / mm < 2 > or more has been used, but in general, the welded joint strength tends to be larger as the strength is higher. Therefore, in order to secure the toughness of the weld heat affected zone, it is necessary to reduce the heat input to the weld, and to reduce the amount of heat received by the welded plate.

In addition, in a high-tensile steel sheet having increased strength by a tempering technique such as a TMCP (Thermomechanical Control Process) steel, the performance of the weld heat affected zone tends to deteriorate, and the strength is likely to decrease. Such a decrease in the mechanical strength is caused by the influence of the enlargement of the metal structure. Therefore, it is also required to reduce the heat input to the weld.

In the welding method of Patent Document 1, in order to reduce heat input to the welding, the protruding length of the welding wire is lengthened to increase the heat generation amount of resistance and to accelerate the melting speed of the welding wire. However, excessive protrusion of the welding wire causes the arc to become unstable, which may cause a large amount of spatters to be generated. That is, there is a possibility that the workability of the welding is lowered. Further, if welding is performed by increasing the projecting length of the welding wire, it is possible to reduce the heat input to the welding, but welding defects such as defective penetration are likely to occur. For example, when the protruding length of the welding wire becomes 70 mm, deviation of the target position of the wire is liable to occur due to the distortion property of the welding wire.

In the welding method of Patent Document 2, by supplying hot wire to the improvement, the welding speed (the amount of thickness per unit time) is increased and the substantial heat input of welding is reduced. However, since the hot wire is a wire that does not generate an arc, if the supply position is not proper, there is a fear that a penetration failure occurs in the improvement portion. Further, when the arc length is changed, the heat input amount is increased or decreased, and therefore the amount of hot wire to be supplied to the improvement varies. As a result, variations in the quality of the welds tend to occur.

Further, depending on the welding conditions, the volume of the tip of the welding wire becomes difficult to deviate, and the volume transition becomes unstable. Particularly, in the case of using a flux cored wire, scattering of flux occurs and welding workability is deteriorated.

As described above, in the welding methods of the respective patent documents, there is a problem that the amount of spatter generated increases and the welding failure occurs, thereby deteriorating the welding quality and welding workability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to provide a welding method and a welding method capable of improving the welding speed without impairing the welding workability and securing the toughness of the welding heat affected zone, An arc welding method, and an electrogas arc welding apparatus.

The present invention provides the following electrogas arc welding method.

Wherein the end portions of the pair of welded plates are opposed to each other so that the improvement extends in the up and down direction and the width of the surface side is wider than the back side, Wherein a fixed disaggregation material is brought into contact with the back surface side of the welded plate so that the tip of the torch of one or more welding torches is inserted into the improvement and,

A power cable having a length of 3 m or more is connected between the welding torch and the welding power source, and between the welding target and the welding power source,

A welding current is applied by applying an arc voltage between the welding wire inserted in the improvement from the welding torch and a pair of the to-be-welded plates, and the welding is performed while the sliding plate is slid upward, An electrogas arc welding method comprising:

A flux cored wire having a flux rate of 15 to 30% on the welding wire, a gas having a CO ₂ concentration of 50% or more in the shield gas, and a pulse current as the welding current,

Wherein the rise time of the pulse current until reaching the peak current value is 0.1 to 5.0 ms and the frequency of the pulse is 20 to 200 Hz.

According to such an electrogas arc welding method, conditions of the shielding gas composition, the flux cored wire, and the welding current are optimized, and the volume transition of the tip of the flux cored wire can be stabilized. As a result, the amount of heat input can be reduced to improve the toughness of the welded portion, and further, the occurrence of spatter can be suppressed, and workability can be improved. Note that the range of "A to B" in the present specification means a range including the values of A and B.

It is preferable that the pulse current is set to a condition that the pulse peak current I _P is 400 to 800 A, the pulse peak period t _p is 1.0 to 4.0 ms, and the base current I _B is 100 to 200 A .

According to such an electrogas arc welding method, a volume capable of stably releasing in the pulse base period can be formed in the pulse peak period, and stabilization of the volume transition can further improve workability.

Further, it is preferable that the plate thickness of a pair of the welded plates is 45 to 100 mm, and the heat input to the welding is 20 to 75 kJ / mm.

According to such an electrogas arc welding method, the heat input of welding is suppressed to a predetermined range, so that the deterioration of the HAZ softening strength of the welded plate can be reduced.

It is preferable that the welding wire having a diameter of 1.2 to 2.0 mm is used.

According to such an electrogas arc welding method, the balance between the effect of reducing the heat input of the welding and the effect of supplying the welding metal by melting the welding wire is improved.

Further, as the welding wire, the wire full, by mass Mn: 1.50 ~ 2.50 mass%, SiO _2: 1.0 ~ 0,1 mass%, Ni: 0.5 ~ 3.0 mass%, Ti: 0.1 ~ 0.5 mass%, B: 0.004 To 0.020% by mass of a flux cored wire.

According to such an electrogas arc welding method, the toughness of the welded portion is increased, and the mechanical performance of the welded portion can be improved.

It is preferable that the ratio of the iron powder in the flux contained in the welding wire is 40 to 90% with respect to the total weight of the flux.

According to such an electrogas arc welding method, the welding wire is easily melted, and scattering of the flux can be suppressed.

In addition, it is preferable that a plurality of the welding torches are inserted in the improvement, at least one of the welding torches is disposed on the front surface side, a current applied to the welding torch disposed on the front surface side, It is desirable to reverse the polarity of the current applied to the torch.

According to this electrogas arc welding method, in addition to pulling out the arc from each welding torch and collecting the arc at the center side between the welding torches, the spatter is pulled in the same direction as the arc. As a result, it is possible to perform stable welding as a whole.

Further, among the plurality of welding torches, the tip of the welding wire projecting from the tip of the welding torch closest to the back surface of the to-be-welded plate is disposed at a position of 15 to 25 mm in horizontal distance from the back surface of the to- .

According to such an electrogas arc welding method, it is possible to melt a desired amount of a welded plate, thereby preventing defective penetration.

Further, the present invention is characterized in that the end portions of the pair of welded plates are opposed to each other so that the improvement extends in the vertical direction and the width of the front side is wider than the back side, And a fixed discrete material is brought into contact with the back surface side of the to-be-welded plate and the tip of the torch of the one or more welding torches is brought into contact with the back surface of the to- Inserted in the improvement,

A power cable having a length of 3 m or more is connected between the welding torch and the welding power source, and between the welding target and the welding power source,

A welding current is applied by applying an arc voltage between the welding wire inserted in the improvement from the welding torch and a pair of the to-be-welded plates, and the welding is performed while the sliding plate is slid upward, An electrogas arc welding apparatus,

The welding wire is a flux cored wire having a flux rate of 15 to 30%

The shield gas is a gas having a CO ₂ concentration of 50% or more,

Wherein the welding power source unit is a welding current source for supplying the welding current flowing between the welding wire and the pair of welded plates with a rise time of 0.1 to 5.0 ms until the peak current value is reached and a pulse frequency of 20 to 200 Hz Wherein the power source is a power source capable of supplying a pulse current.

According to such an electrogas arc welding apparatus, conditions of the shielding gas composition, the flux cored wire, and the welding current are optimized, and the volume transition of the flux cored wire ends can be stabilized. As a result, the amount of heat input can be reduced to improve the toughness of the welded portion, and further, the occurrence of spatter can be suppressed, and workability can be improved.

According to the present invention, it is possible to improve the welding speed without impairing the welding workability and to secure the toughness of the weld heat affected zone, thereby improving the mechanical properties of the weld metal.

1 is a schematic overall configuration diagram of an electrogas arc welding apparatus according to a first configuration example,
Fig. 2 is an explanatory view schematically showing a mode of an electrogas arc welding,
3 is a cross-sectional view in the direction of the plate thickness direction showing an improved shape of the welded plate,
Fig. 4 is an explanatory diagram showing the state of the volume of the shielding gas generated in the welding wire by the pulse current,
5 is a graph showing an example of the waveform of the welding current when the welding power source is driven in the pulse mode,
6 is an explanatory diagram of a target position within the improvement of the welding wire,
7 is a schematic overall configuration diagram of a welding apparatus according to a second configuration example;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Configuration Example>

Fig. 1 is a schematic overall configuration diagram of an electrogas arc welding apparatus according to a first configuration example, and Fig. 2 is an explanatory diagram schematically showing a configuration of an electrogas arc welding.

The electro-arc arc welding apparatus 100 shown in Figs. 1 and 2 is characterized in that an improvement 11 (see Fig. 2) in which end portions of a pair of welded plates are opposed to each other is formed in a vertically- 15A, and 15B). The welded plates 15A and 15B handled here are, for example, thick steel plates having a plate thickness of 45 to 100 mm. For example, high tensile steel plates of YP 390 N / mm &lt; 2 &gt; In the following description, the electrogas arc welding apparatus is simply referred to as a welding apparatus.

As shown in Fig. 2, the welding apparatus 100 is configured such that the end portions of the pair of welded plates 15A and 15B extend in the vertical direction from the bottom side to the bottom side, And a sliding plate 17 made of copper capable of sliding upward along the improvement 11 is provided on the surface of the portion where the improvement 11 of the pair of welded plates 15A and 15B is formed, Respectively.

Dispersing material 19 made of ceramics or copper is disposed in contact with the opposite side of the sliding plate 17 of the welded plates 15A and 15B. The disazo member 19 is fixed to the back side of the welded plates 15A and 15B. A plurality of welding torches 21 and 23 are inserted and arranged in the improvement 11 surrounded by the sliding plate 17, the welding plates 15A and 15B and the disassembly member 19 . The welding apparatus 100 of the illustrated example is a two-electrode welding apparatus having two torches, but a welding apparatus having three or more torches may be used, or a welding apparatus having only one torch described later in detail.

1, the welding apparatus 100 includes a wire feeding section 35 for feeding the welding wire 25 to the welding torch 21, a wire feeding section 35 for feeding the welding wire 26 to the welding torch 23, And a welding power supply unit 39 for supplying a welding current to the welding wires 25 and 26 loaded on the welding torches 21 and 23. [

The welding power supply unit 39 of the present configuration includes a first welding power source 41 for supplying a welding current between the welded plates 15A and 15B and the welding wire 25 and the welded plates 15A and 15B And a second welding power supply 43 for supplying a welding current between the welding wires 26. [ The first welding power source 41 and the second welding power source 43 each have a pulse control circuit capable of outputting a pulse-shaped welding current. In this embodiment, different welding power sources are used for each welding wire. Alternatively, only one welding power source capable of outputting welding currents under different conditions with a plurality of welding wires may be provided.

The wire supplying section 35 supplies the welding wire 25 through the welding torch 21 toward the tip of the welding torch 21. [ The wire feeder 37 feeds the welding wire 26 through the welding torch 23 toward the tip of the welding torch 23. The welding wires 25 and 26 used herein are welding wires of a flux cored wire having a diameter of 2.0 mm or less.

The welding wire 26 protruding from the tip of the welding torch 21 and between the welding plates 51A and 15B and the torch tip of the welding torch 23 and the welding wire 26 And 15B, an arc voltage is applied by the welding power source unit 39, and a welding current flows.

In this welding power source 39, a pulse mode for outputting a pulse current and a constant voltage (CV) mode for constant voltage control are selectively set. In the pulse mode, a pulse current changed to a pulse shape is output. In the CV mode, a current waveform having no special shape is output. The switching between the pulse mode and the CV mode may be performed manually or by an instruction from a control device not shown connected to the welding apparatus 100. [ The welding power source 39 may be a power source driven only in the pulse mode.

The welding torches 21 and 23, the sliding plate 17, and the wire feeding parts 35 and 37 are supported by a lift frame (not shown) to be movable up and down. The elevating frame is configured such that the sliding plate 17, the welding torches 21 and 23, and the wire feeding parts 35 and 37 are integrally moved up and down at the same speed along the arrow P shown in FIG. . Thereby, the sliding plate 17 rises while sliding with the surfaces of the welded plates 15A and 15B.

The torch tip of the welding torch 23 is inserted into the improvement 11 of the welded plate 15A, 15B. The welding torch 23 is mounted on the lifting frame via an oscillating device (not shown).

The oscillator device rocks the welding torch 23 in the plate thickness direction S (see Fig. 6) of the welded plates 15A and 15B. Such an oscillator may be a mechanism capable of swinging the welding torch 23 in the plate thickness direction S or may be a structure using a cam mechanism for converting the rotational motion of the motor into a linear motion, (23) may be directly operated.

The welding wires 25 and 26 supplied to the torch tip of the welding torches 21 and 23 protrude from the torch tip at predetermined constant lengths, respectively. A welding current from the welding power source 39 is supplied between the protruded and exposed welding wires 25 and 26 and the welded plates 15A and 15B to generate an arc.

The protruding length of the welding wires 25, 26 from the torch tip, that is, the distance between the tip of the torch and the welded plates 15A, 15B as base materials, is set to a constant amount of 30 to 50 mm. If the protruding length exceeds 50 mm, deviation of the target position tends to occur due to the twisting property of the wire. Also, the resistance heat generation is increased, and the melting amount of the welding wires 25, 26 becomes a proper value or more. As a result, the melting volume becomes large and spatters of large grains are multiplied. If the protrusion is less than 30 mm, the welding efficiency is lowered and the welding speed is slowed down.

The sliding plate 17 is cooled by circulating the cooling water in the sliding plate so as to prevent itself from dissolving into the welding heat. In this constitution, a cooling water flow path 27 for circulating the cooling water W is provided in the lower part of the sliding plate 17. The cooling water supply port 29 and the discharge port 31 are connected to the cooling water flow path 27 and the cooling water W supplied from the supply port 29 flows into the cooling water flow path 27

At the upper portion of the sliding plate 17, a gas spouting portion 33 for spouting the shielding gas G is provided. The shield gas blocks the weld metal in the enhancement 11 from the atmosphere, shielding the enhancement 11.

3 is a cross-sectional view in the direction of the plate thickness direction showing an improved shape of the welded plates 15A and 15B. The improvement 11 of the welded plates 15A and 15B has a wider surface side than the backside of the welded plates 15A and 15B. The shape of the improvement 11 of the welded plates 15A and 15B is set such that the plate thickness t of the welded plates 15A and 15B is 80 mm and the improvement angle θ is 20 °, (GAP) is 10 mm. In this improvement 11, an arc is generated from each of the two welding wires 25 and 26 exposed by protruding from the welding torches 21 and 23 while the surroundings of the welding wires 25 and 26 are shielded gas atmosphere And an electro-gas arc welding is performed.

The arc generated from the welding wires 25 and 26 melts the welding wires 25 and 26 themselves and also melts a part of the welding plates 15A and 15B. Thereby, the molten metal 47 is formed in the improvement 11. This molten metal 47 solidifies to form a weld metal 49 that embeds the improvement 11.

<Condition of welding wire, shield gas, welding current>

Next, the welding wire, the shielding gas, and the welding current used in the welding apparatus 100 having the above-described structure will be described.

As means for reducing the heat input in general, for example, a flux cored wire is used, and a welding current is pulsed. If the welding current values are the same, the flux cored wire has higher welding efficiency than the solid wire. Therefore, the flux cored wire can reduce the heat input amount compared with the solid wire. Further, as the flux rate of the wire (the ratio of the amount of flux in the wire to the total weight of the wire) is larger, the effect of reducing the heat input amount can be obtained. However, in the flux cored wire, since the wire core is formed by the flux, the flux tends to scatter at the tip of the wire during welding, and the spatter tends to be formed, so that the welding workability is deteriorated. Such deterioration in workability is conspicuous when the flux rate is high or when pulse welding is applied.

With respect to the wire diameter, when the welding wire 25 becomes thick, the electrical resistance of the welding wire 25 decreases. Therefore, the welding wires 25 and 26 protruding from the torch tip of the welding torches 21 and 23 need to flow a higher welding current. Therefore, as the welding wire becomes thicker, the heat input to the welding becomes larger.

Thus, in the welding apparatus 100 of the present configuration, even when flux cored wires are used as the welding wire, the conditions of the welding wire, the shielding gas, and the welding current are optimized, So that the mechanical properties of the welded portion are improved. Hereinafter, the optimization conditions will be described in detail.

<Characteristics of welding wire>

(1) Flux ratio

In the case of the solid wire, when the waveform of the pulse current is weak due to the elongation of the power cable, such as the electrogas welding, the pinch force is insufficient, so that it is difficult for the solid wire to deviate from the tip of the welding wire periodically, Volume transfer becomes unstable. However, when the flux rate is set to 15 to 30% by using a flux cored wire as the welding wire, even when the waveform of the pulse current becomes dull, the volume tends to be easily added. If the flux rate is less than 15%, sufficient pinch force can not be obtained with respect to the displacement of the volume, so that the volume transfer becomes unstable and the welding workability is deteriorated. On the other hand, if the flux rate exceeds 30%, the flux begins scattering and the welding workability deteriorates. The "dullness " of the waveform referred to here indicates a state in which the rising and falling of the peak waveform becomes gentle.

(2) Composition

The toughness and welding workability of the weld heat affected zone are further improved by defining the content (mass%) of Mn, Ni, B, Ti, and SiO ₂ contained in the welding wire per the total mass of the wire in the following range.

Mn: 1.50 to 2.50 mass%

Mn in the welding wire exerts its effect as a deoxidizing agent or a sulfur capturing agent and is preferably added in order to secure strength and toughness of the weld metal. It is more preferable to contain not less than 1.50 mass% for ensuring toughness. On the other hand, if it is 2.50 mass% or less, deterioration of the toughness of the weld metal due to excess strength can be suppressed. Therefore, it is preferable that the content of Mn is specified in the range of 1.50 to 2.50 mass%.

Ni: 0.5 to 3.0 mass%

Ni is preferably added to secure the strength and toughness of the weld metal. It is more preferable to contain not less than 0.5% for ensuring toughness. On the other hand, when the content is 3.0% by mass or less, deterioration of the toughness of the weld metal due to excess strength can be suppressed. Therefore, it is preferable that the content of Ni is specified in the range of 0.5 to 3.0 mass%.

Ti: 0.1 to 0.5 mass%

Ti is an element which forms stable oxides, carbides, and nitrides as a steel element, contributing to grain refinement and the like, and therefore Ti is preferably added in order to secure the strength and toughness of the weld metal. It is more preferable to contain not less than 0.1% by mass for ensuring toughness. On the other hand, when the content is 0.5% by mass or less, deterioration of the toughness of the weld metal due to excess strength can be suppressed. Therefore, the content of Ti is preferably set in the range of 0.1 to 0.5% by mass.

B: 0.004 to 0.020 mass%

Since B forms a stable nitride and contributes to the refinement of crystal grains and the like, it is preferable to add B to secure the strength and toughness of the weld metal. It is more preferable to contain 0.004% by mass or more for ensuring toughness. On the other hand, when the content is 0.020 mass% or less, toughness and cracking of the weld metal due to the excess strength can be suppressed. Therefore, the content of B is preferably set in the range of 0.004 to 0.020 mass%.

SiO ₂ : 0.1 to 1.0 mass%

SiO ₂ is a negative electrode point formed on the surface of the melting paper and is preferably added for arc stability. It is preferably added in an amount of 0.1 to 1.0% by mass for stabilizing the arc. In addition, when Ti is added, Ti becomes a stable oxide and, like SiO ₂ , acts as a cathode point on the surface of the melting paper. SiO ₂ and Ti oxide have different thermoelectron emission performance, and therefore, it is more preferable that Ti / SiO ₂ is 0.5 to 3.0 as a ratio that effectively acts as arc stability.

(3) Iron content

The ratio of the iron content in the flux contained in the welding wire is preferably 40 to 90% based on the total weight of the flux. In such a range, since the iron powder is easily melted, scattering of the flux in the peak current period of the welding current can be suppressed. Further, the advantage of the CO ₂ gas described later can be improved.

<Shielding gas>

The shield gas used for the welding apparatus 100 is a mixed gas having a CO ₂ concentration of 50% or more, or a CO ₂ gas of 100%. In the following description, a gas having a CO ₂ concentration of 50% or more and a CO ₂ gas having a concentration of 100% may be simply referred to as a CO ₂ gas. The pulse shape appropriately set for the dullness of the pulse waveform by the elongated cable unique to the electrogas welding and the arc shrinkage effect of the shield gas containing the CO ₂ gas enable an optimum size Can be formed at the tip of the welding wire. As a result, the volume transition of the welding wire tip is stabilized.

The flow rate of the shielding gas is preferably 40 L / min or more. This is because a large amount of gas is required in comparison with ordinary gas shielding welding because the improvement cross section is large in welding in the shipbuilding field.

Fig. 4 is an explanatory diagram showing a volume state of each shielding gas produced on a welding wire by a pulse current. Fig.

In the figure, the waveform of the pulse current dropped from the normal pulse waveform indicated by the dotted line is indicated by the solid line. The pulse current at time t1 becomes the current value E1 during the gentle rise.

When the CO ₂ concentration of the shield gas is 50% or more, the volume 51 grows at the tips of the welding wires 25, 26 and 28 due to the shortening of the arc at the time t1. By the formation of such a volume, scattering of the flux can be prevented. At time t2, the pulse current reaches the peak current value of the normal pulse waveform. When the peak current E2 is reached, the gently-grown liquid droplet is separated from the welding wire 25, 26, 28. As a result, it is possible to realize regular deviation of the liquid droplets, and to stabilize the volume transition at the tip of the welding wire. Therefore, the deterioration of the welding workability, which has been the above-mentioned problem, can be solved.

On the other hand, when the shield gas is an Ar rich gas, the arc climbs up to the welding wire side, and the welding wire ends are not sufficiently formed at the tip of the welding wire, so that the flux column is exposed and the flux is scattered, .

<Welding current>

The welding power supply unit 39 can independently output the driving power to be output to the welding wire 25 and the driving power to be output to the welding wire 26 respectively. In the welding power source unit 39 of the present configuration, a pulse current in the pulse mode is outputted to at least one of the welding wires 25 and 26.

5 is a graph showing an example of the waveform of the welding current when the welding power source 39 is driven in the pulse mode. The waveform of the welding current shown in the drawing is a waveform of the welding current actually flowing at the welding portion between the tip of the welding wires 25 and 26 and the welded portions 15A and 15B. In the two-electrode electro- , And the wire feeding speed is 14.8 m / min. In this case, the current waveform of the welding current outputted from the welding power source section is a rectangular wave. The welding current has a pulse peak current I _P of 600 A, a pulse peak period of 4.5 ms, a base current I _B of 180 A, and a base period t _B of 5.0 ms. The frequency f of the pulse of the welding current is 111 Hz. Further, the pulse peak period t _p includes the rising and falling periods.

In the welding apparatus 100 of this configuration, a rectangular wave having a pulse peak current I _P of 400 to 800 A, a pulse peak period t _p of 1.0 to 4.0 ms, and a base current IB of 100 to 200 A desirable.

The pulse current flowing between the welding wires 25 and 26 at the tip of the torch and the welded plates 15A and 15B is determined by the rise time and the frequency of the pulse until the peak current value of the welding torch reaches the peak current value Ensure that the condition is satisfied.

(1) Rise time

The rising time until the pulse current reaches the peak current value is 0.1 to 5.0 ms. The rise time in the range of 0.1 to 5.0 ms is an optimal condition for stabilizing the volume when the shielding gas is CO ₂ gas and the flux cored wire is used. Then, welding is performed in a period in which the current value gradually increases. When the rise time is less than 0.1 ms, a sharp pinch force is applied to the flux cored wire, and the flux in the wire is scattered, thereby deteriorating the workability. When the rise time exceeds 5.0 ms, the volume deviation occurs during the peak period, and coarse spatter of 1 mm or more occurs.

(2) the frequency of the pulse

The frequency of the pulse of the pulse current is 20 to 200 Hz. Conventional MAG (Metal Active Gas) welding requires a frequency in excess of 200 Hz to stabilize volume transfer. On the other hand, in the case of the electrosurgical arc welding of this configuration, when the frequency is less than 20 Hz or exceeds 200 Hz, the regularity of the volume transition is disturbed, and the amount of spatter is increased. In other words, the volume transfer of the welding wire can be stabilized by using the flux cored wire, the gas having a CO ₂ concentration of 50% or more, and the pulse current having a frequency of 20 to 200 Hz as constituent elements of the present invention.

<Optimization Effect of Welding Wire, Shield Gas, and Welding Current>

Generally, in the case of using a pulse current, the pulse frequency is set to 200 to 300 Hz by a combination of a solid wire and Ar rich shielding gas of Ar 80% or more. Under such a condition, one pulse 1 drop in which one liquid droplet is generated at the wire tip by one pulse of the pulse current can be achieved. Thereby, excellent welding workability with suppressed spatter can be obtained, and the amount of heat input can also be reduced.

This effect was not obtained except when a combination of a solid wire and a shielding gas of Ar rich was used. For example, in the case where the solid wire is changed to a flux cored wire, even if Ar rich gas is used for the shield gas, the flux is scattered at the time of peak current even if CO ₂ gas is used or a pulse current is used, The workability of the welding is deteriorated. Further, when the shielding gas of Ar rich is changed to CO ₂ gas, the form of the droplet migration of the welding wire is changed unless the pulse current is a special waveform, and the welding workability is deteriorated.

Further, in the case of the electrogas arc welding, the power cable connecting between the welding power source and the welding torch is long, so that the waveform of the pulse current becomes dull. Due to the dullness of such a pulse waveform, pulse current is not generally used in the electrogas arc welding. If a pulse current is used, even when a combination of a solid wire and an Ar rich shield gas is used, the volumetric transfer of the welding wire is disturbed. This is because the power cable is long and the pulse waveform becomes dull, so that the pinch force effect due to the steep rise of the pulse peak current can not be obtained, and it deviates from the form of one pulse and one drop. As a result, a spatter is generated, and welding workability is deteriorated. Further, even when the pulse current is made to be a special waveform by using CO ₂ gas, a pulse current of a special waveform having a first peak current having a high current value and a second peak current having a second peak current lower than the first peak current, The waveform becomes dull due to the attenuation of the second peak current which is low, and any volumetric transition control can not be performed. Therefore, in either case, the original effect of reducing the heat input and improving the welding workability could not be attained.

The welding apparatus 100 of the present configuration makes it possible to use a pulse current that has not been used in the electrogas arc welding until now by welding under the conditions of the welding wire, the shielding gas and the welding current described above, Thereby realizing stable volume transfer. As a result, it is possible to reduce the heat input and improve the mechanical performance such as toughness of the weld heat affected zone. In addition, by stabilizing the volume transition, the occurrence of spatter can be reduced, and welding workability can be improved.

According to the welding apparatus 100 of this configuration, when the welded plates 15A and 15B are subjected to arc welding by electro-arc welding, the welding heat input to the improvement 11 can be 20 to 75 kJ / mm. When the heat input of the weld is 20 kJ / mm or more, the welding efficiency is improved. When the heat input of the weld is 75 kJ / mm or less, the strength reduction is suppressed.

When the welding current is applied to the welding wire 25 of the welding torch 21 and the welding wire 26 of the welding torch 23 in the welding apparatus 100 of this configuration, It is preferable to make the polarities different from each other. The welding wire 25 of the welding torch 21 is connected to the direct current polarity DC-EN and the welding wire 26 of the welding torch 23 is connected to the DC reverse polarity DC- do. By making the polarities of the respective currents different from each other, the spatter is reduced, and the welding workability becomes better.

In order to suppress the generation of spatter, it is also possible to use a technique such as shifting the pulse peak period to be applied to each welding torch.

Further, in the case of a welding method using a plurality of electrodes such as two-electrode electro-arc arc welding, when the respective welding torches are DC-EN and DC-EP, the arc generated from each welding torch is stabilized, The generated spatters are reduced. Further, it is preferable that the welding torch interval is 20 mm to 40 mm, and since the arc is more stable, welding with good workability can be performed.

In the conventional electrogas arc welding method, the welding wire 25 is disposed at a distance of 20 to 30 mm from the disazo member 19 by a horizontal distance. However, in the present electrosurgical arc welding method, if the same welding wire 26 is disposed, there is a fear that penetration failure may occur, such as a gap between the welding metal on the back side and the disazotizing material 19, have. In addition, the welding current value is lower in the pulse mode than in the CV mode. Therefore, if the target position of the welding wire is set to be the same in the pulse mode and the CV mode, even if good welding is performed in the CV mode, a back bead hardly appears when welding is performed in the pulse mode, May not be obtained. Thus, in the case of the pulse mode, the target position of the welding wire 25 closest to the back surface of the welded plates 15A and 15B is arranged at a position of 15 to 25 mm in horizontal distance from the disazo member 19 . Thereby, the welding wire 25 approaches the position of 15 to 25 mm from the disazo member 19, and the required amount of the welded plate can be melted, thereby preventing defective penetration.

Fig. 6 is an explanatory view of a target position within the improvement 11 of the welding wires 25 and 26. Fig. When the welding torch 23 (see Fig. 1) is rocked by the above-described oscillating device, the welding wire 26 oscillates along the plate thickness direction S. The weaving width of the welding wire 26 by the oscillator device is determined by the position P1 of the distance L4 from the surface side of the welded plates 15A and 15B and the distance L3 from the position P1. To the position P2 of the second lens group. The welding wire 25 of the welding torch 21 is disposed at a position P3 facing the back side of the welded plates 15A and 15B by a distance L2 from the position P2. The above distances L1 to L4 are set to the dimensions shown in Table 1 below. Any one of the electrode positions (PO1, PO2, PO3) in the table can prevent the occurrence of infusion failure.

[Table 1]

As described above, by adopting the rectangular wave pulse current as the welding current supplied to the welding torches 21 and 23, it is possible to surely perform the low insertion loss even under circumstances where the welding current waveform is liable to become dull by the long cable . Arc interference can be avoided by placing each welding torch at the opposite polarity in a condition that a flux cored wire is used and an arc called pulse welding by CO ₂ gas shield tends to become unstable, The arc is stabilized. For this reason, it is possible to form a weld metal free from welding defects such as defective fusion while aiming at low-rate deterioration.

In the welding apparatus 100 of the present configuration, the welding wire 25 disposed on the back side of the welded plates 15A and 15B is not pivoted, only the welding wire 26 disposed on the front side, It is preferable to oscillate by the apparatus. The swing of only the welding wire 26 improves the arc stability and reduces the amount of spatter generated. As a result, good welding workability can be ensured even in the case of a long-time thread welding operation in which the dimensional deviation of the improvement 11 is large. Instead of oscillating the welding wire 26, an oscillator device may be mounted on the welding wire 25 side to rock the welding wire 25, and both the welding wire 25 and the welding wire 26 It may be rocked at the same time. In this case, by swinging the welding wires 25 and 26 with one oscillator device, the device configuration of the welding device 100 can be simplified.

&Lt; Second Configuration Example &

Next, a second configuration example of the electro-arc arc welding apparatus will be described. 7 is a schematic overall configuration diagram of a welding apparatus according to the second configuration example. In the following description, the same members or portions are denoted by the same reference numerals, and the description thereof is omitted or simplified.

The welding apparatus 200 according to the present embodiment is different from the welding apparatus 200 according to the first embodiment in that a single wire feeder 38 having a single wire feeder 38 is provided in place of the two-electrode configuration having the pair of wire feeders 35, 37 of the welding apparatus 100 shown in Fig. . The welding power source unit 40 is provided with a single welding power source 44 in place of the first welding power source 41 and the second welding power source 43. [ Other configurations are the same as those of the welding apparatus 100 described above. It is also possible for the welding wire 28 to oscillate by an oscillator device not shown.

According to the welding apparatus 200 of the present configuration, the single-wire supply unit 38 can perform the electro-arc arc welding in the same manner as the above-described welding conditions. Thus, even when the plate thickness of the welded plates 15A and 15B is less than 45 mm, the same operation and effect as described above can be obtained. That is, even if the welding torch is a single stage or a plurality of stages, as described above, the flux cored wire is used for the welding wire, the CO ₂ gas is used for the shield gas and the pulse current is used for the welding current, The arc welding can be optimized.

[Example]

Evaluation results of Examples 1 to 56 in which the welding apparatus 100 shown in Fig. 1 and the welding apparatus 200 shown in Fig. 7 were used and welded using the welding wire shown in Table 2 are shown in Tables 3 and 4 Respectively.

<Welding conditions>

Welding speed: 20 mm / min

Plate thickness (one electrode): 45 mm

Plate thickness (two electrodes): 80 mm

Root gap: 10 mm

Improvement angle: 20 °

<Evaluation Criteria>

(1) With regard to the bead appearance, the presence or absence of undercut or sagging was visually evaluated. The evaluation criteria are that A is good and B is bad.

(2) The defective fusion was evaluated by the presence or absence of occurrence of defective penetration by an Ultrasonic Testing (UT) test (JIS Z 3060: 2002). The evaluation criterion is that A is not infused and B is infected.

(3) Spatter workability was measured by a high-speed video camera, and the number of spatters generated per 10 seconds was evaluated in three stages of A, B and C on the basis of the following.

A: Less than 100

B: 100 or more, less than 200

C: 200 or more

(4) The toughness is compared with the results of the Charpy impact test (JIS Z 2242: 2005) of the test sample by the electrostatic arc welding of the constant voltage by the solid wire, and the three levels of A, B and C I appreciated.

A: 100 or more, 120 or less

B: 60 or more, less than 100

C: less than 60

[Table 2]

[Table 3]

[Table 4]

As in Experimental Examples 45 to 47, when the Ar ratio in the shielding gas is increased, the flux is scattered at the time of displacement, and the workability is deteriorated.

If the cable length is less than 3 m as in Experimental Examples 48 and 49, the increase of the pulse current becomes less than 0.1 ms because the waveform does not become dull, and in the combination of the flux cored wire and the CO ₂ gas, The spatters were not formed and the workability deteriorated.

As in Experimental Examples 50 and 51, when the cable length was 100 m, the waveform became excessively dull, and the rise of the pulse current exceeded 5.0 ms, and the workability deteriorated.

As in Experimental Example 52, when the flux rate of the flux cored wire is less than 15%, sufficient pinch force is not obtained against the displacement of the volume, so that the volume transfer becomes unstable and the welding workability is deteriorated.

On the other hand, as in Experimental Example 53, when the flux rate exceeds 30%, the flux started scattering and the welding workability deteriorated.

Experimental Example 54 is a welding method in which a solid wire, a CO ₂ gas, and a pulse current are combined. In such a case, the volume transfer became unstable, and the bead appearance defect and welding workability deteriorated.

Experimental Example 55 is a case where the rise time exceeds 5.0 ms and the frequency becomes less than 20 Hz. In such a case, volume detachment occurred during the peak period, and coarse spatter of 1 mm or more was generated, and welding workability deteriorated.

Experimental Example 56 is a case where the frequency exceeds 200 Hz. In such a case, a sharp pinch force is applied to the flux cored wire, and the flux in the wire is scattered, thereby deteriorating the welding workability.

11: improvement 15A, 15B:
17: sliding plate 19:
25, 26, 28: welding wire 39, 40: welding power source
100, 200: Electro arc arc welding device

Claims (8)

Wherein the end portions of the pair of welded plates are opposed to each other so that the improvement extends in the up and down direction and the width of the surface side is wider than the back side, Wherein a fixed disaggregation material is brought into contact with the back surface side of the welded plate so that the tip of the torch of one or more welding torches is inserted into the improvement and,
A power cable is connected between the welding torch and the welding power source, and between the welding target and the welding power source,
A welding current is applied by applying an arc voltage between the welding wire inserted in the improvement from the welding torch and a pair of the to-be-welded plates, and the welding is performed while the sliding plate is slid upward, An electrogas arc welding method comprising:
A flux cored wire having a flux rate of 15 to 30% on the welding wire, a gas having a CO ₂ concentration of 50% or more in the shield gas, and a pulse current as the welding current,
The rise time of the pulse current until reaching the peak current value is 0.1 to 5.0 ms, the frequency of the pulse is 20 to 200 Hz,
The length of the power cable is 3 m or more and less than 100 m,
The pulse current is set to a condition that the pulse peak current IP is 400 to 800 A, the pulse peak period t _p is 1.0 to 4.0 ms, and the base current I _B is 100 to 200 _A.
Electro gas arc welding method. The method according to claim 1,
Wherein the plate thickness of a pair of the to-be-welded plates is 45 to 100 mm, and the heat input to the welding is 20 to 75 kJ / mm
Electro gas arc welding method. The method according to claim 1,
Wherein the welding wire having a diameter of 1.2 to 2.0 mm is used
Electro gas arc welding method. The method according to claim 1,
As the welding wire, the wire full, Mn by mass: 1.50 ~ 2.50% by mass, SiO _2: 0.1 ~ 1.0% by mass, Ni: 0.5 ~ 3.0 mass%, Ti: 0.1 ~ 0.5 mass%, B: 0.004 ~ 0.020% by weight And a flux cored wire containing a flux cored wire
Electro gas arc welding method. The method according to claim 1,
Characterized in that the ratio of the iron content in the flux contained in the welding wire is set to 40 to 90% with respect to the total weight of the flux
Electro gas arc welding method. 6. The method according to any one of claims 1 to 5,
At least one of the welding torches is disposed on the front surface side, at least one of the welding torches is disposed on the back surface side, and a current applied to the welding torch disposed on the front surface side And a polarity of a current to be applied to the welding torch disposed on the backside is reversed
Electro gas arc welding method. The method according to claim 6,
The tip of the welding wire protruding from the torch tip of the welding torch closest to the back surface of the welded plate is disposed at a position of 15 to 25 mm in horizontal distance from the back surface of the welded plate among the plurality of welding torches &Lt; / RTI &gt;
Electro gas arc welding method. Wherein the end portions of the pair of welded plates are opposed to each other so that the improvement extends in the up and down direction and the width of the surface side is wider than the back side, Wherein a fixed disaggregation material is brought into contact with the back surface side of the welded plate so that the tip of the torch of one or more welding torches is inserted into the improvement and,
A power cable is connected between the welding torch and the welding power source, and between the welding target and the welding power source,
A welding current is applied by applying an arc voltage between the welding wire inserted in the improvement from the welding torch and a pair of the to-be-welded plates, and the welding is performed while the sliding plate is slid upward, An electrogas arc welding apparatus,
The welding wire is a flux cored wire having a flux rate of 15 to 30%
The shield gas is a gas having a CO ₂ concentration of 50% or more,
Wherein the welding power source unit is a welding current source for supplying the welding current flowing between the welding wire and the pair of welded plates with a rise time of 0.1 to 5.0 ms until the peak current value is reached and a pulse frequency of 20 to 200 Hz A power supply capable of supplying a pulse current,
The length of the power cable is 3 m or more and less than 100 m,
The pulse current is set to a condition that the pulse peak current IP is 400 to 800 A, the pulse peak period t _p is 1.0 to 4.0 ms, and the base current I _B is 100 to 200 _A.
Electro - gas arc welding equipment.

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