KR20080012211A - Multielectrode gas-shield arc welding method - Google Patents

Abstract

A multi-electrode gas shield arc welding method is provided to prevent the poor shape of a bead when welding is performed at a high speed. Flux-containing wires for gas shield arc welding are used as leading and trailing electrodes, respectively. A distance between the leading and trailing electrodes is set to a range of 15mm to 50mm. A filler wire is inserted into a molten metal between the leading and trailing electrodes. Direct current electrode positive is made to flow to the leading and trailing electrodes. Direct current electrode negative (wire: minus) is made to flow to the filler wire. A sum (L+T) of a deposition rate (L) of the leading electrode and a deposition rate (T) of the trailing electrode ranges from 100 to 500 g/min. A deposition rate (F) of the filler wire ranges 0.03(L+T) to 0.3(L+T).

Description

MULTIELECTRODE GAS-SHIELD ARC WELDING METHOD}

The present invention relates to a multi-electrode gas shielded arc welding method using a flux-containing wire, and more particularly, to a multi-electrode single pool welding construction (a gas shielded arc welding method of forming one welding paper with two electrodes). The present invention relates to a multi-electrode gas shield arc welding method for supplying a filler wire between two electrodes.

Conventionally, in order to achieve high efficiency of horizontal fillet welding of shipbuilding or bridges, the one-pull welding construction method in the multi-electrode gas shield arc welding method has been adopted. However, in the case of the actual structure, due to various obstacle factors ((a) the excessive gap of the fillet weld, (b) the excessive coating film thickness of the shop primer, (c) the current voltage fluctuations in the factory, etc.) The uniformity and stability of the melts, which are their construction points, were lost, and as a result, arc instability occurred, resulting in increased repair welding due to spatter bundles, bead shape, deterioration of appearance and alignment, and bundles of undercuts. In particular, since this tendency becomes remarkable at around 150 to 200 cm / min of welding speed, even if the welding speed is increased, the repair ratio increases, resulting in a significant increase in the number of welds.

Therefore, the applicant of the present application uses the flux-containing wire for gas shielded arc welding as the leading electrode and the trailing electrode, sets the distance between the leading electrode and the trailing electrode to 15 to 50 mm, and sets the filler wire to the preceding electrode and the trailing electrode. A multi-electrode gas shielded arc welding method is proposed, which is inserted into a hot water between and welded while flowing a positive current (wire minus) through the filler wire (Japanese Patent No. 3759114).

In the past, the filler wire is inserted into the melt for adjusting the forward retreat angle of the electrode, the distance between the electrodes, the target position of the electrode, the position taken by the base metal, the length of the wire protrusion, and the like. And welding while flowing a positive current through the filler wire. As a result, in high-speed welding with a welding speed of 200 cm / min or more, welding workability is very stable even when obstacles such as an excessive gap of the fillet weld, an excessive coating film thickness of the shop primer, and a fluctuation of the current voltage in the factory occur. Thus, a multi-electrode gas shielded arc welding method that does not need to be repaired can be obtained.

However, in the prior art, the present inventors have an appropriate range in the welding speed of the preceding electrode, the following electrode, and the filler wire, and particularly in the case where the welding speed of the filler wire is not in the proper range, preventing the appearance of beads and poor bead shape. In view of stabilization of the melts, it has been found that sufficient characteristics cannot be obtained necessarily, and deterioration of porosity may occur due to these factors.

The present invention has been made in view of the above problems, and even in high-speed welding with a welding speed of 150 cm / min or more, the appearance of the beads is surely good and the bead shape prevention and the stabilization of the melt can be obtained. An object of the present invention is to provide a multi-electrode gas shielded arc welding method that can reliably prevent deterioration.

In the multi-electrode gas shielded arc welding method according to the present invention, the flux-containing wire for gas shielded arc welding is used as a leading electrode and a trailing electrode, the inter-pole distance between the leading electrode and the trailing electrode is set to 15 to 50 mm, and the filler wire Is inserted into a melt between the preceding electrode and the trailing electrode, a reverse electrode current flows through the preceding electrode and the following electrode, and a positive electrode current (wire minus) flows through the filler wire while welding. In the shield arc welding method, the sum L + T of the welding speed L (g / min) of the preceding electrode and the welding speed T (g / min) of the trailing electrode is 100 to 500 g / min, and the welding speed F of the filler wire F (g Per minute) is 0.03 (L + T) to 0.3 (L + T).

In the multi-electrode gas shield arc welding method, when the current density of the filler wire is j (A / mm 2), the chip-base metal distance is E (mm) and the wire diameter is β (mm), F / (j ² Eβ ² ) is preferably 3.0 × 10 ⁻⁵ to 30.0 × 10 ⁻⁵ (g · mm / A ² · min). Moreover, it is preferable that the current density j of the electric current which flows through the said filler wire is 88 (A / mm <2>) or less. Alternatively, the current density of the current flowing through the filler wire is 88 (A / mm 2) or more, and the current value and the supply amount of the filler wire are individually controlled to prevent arcing from the filler wire. Do.

In addition, it is preferable to control the current value and the wire feeding amount of the filler wire by using a power source capable of independently controlling the current value and the wire feeding amount of the filler wire, respectively. Further, it is preferable to use a filler wire power supply having a function of detecting a voltage between the filler wire and the base material and reducing the current value to 10 A or less regardless of the set current when this voltage exceeds a predetermined value. .

In the present invention, the filler wire is inserted into the melt and welded while flowing a positive current through the filler wire to stabilize the melt and stabilize the arc. At this time, the feed rate and the current of the preceding electrode and the following electrode are such that the sum L + T of the welding speed of the preceding electrode and the following electrode is 100 to 500 g / min, and the welding speed F of the filler wire is 0.03 to 0.3 times the (L + T). Value, feed rate and current value of the filler wire are set. Thereby, the welding speed F of a filler wire becomes 3 g / min at the minimum value, and 150 g / min at the maximum value, and the welding amount of a suitable filler wire is obtained in the bead appearance, bead shape, and stabilization of melted water.

As described above in detail, even in high-speed welding with a welding speed of 150 cm / min or more, excellent bead appearance, bead shape, and stabilization of melts can be reliably obtained.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to attached drawing. 1 is a perspective view showing a multi-electrode gas shield arc welding method according to an embodiment of the present invention, and FIG. 2 is an enlarged longitudinal sectional view showing the molten metal part. Although the welding aspect shown in FIG. 1 and FIG. 2 relates to horizontal fillet welding, it should be understood that the present invention is not limited to this aspect. The lower plate 1 as the welded material is provided horizontally, and the standing plate 2 is vertically disposed on the lower plate 1. The corner part between this standing board 2 and the lower board 1 is fillet-welded by the preceding electrode 3 and the trailing electrode 4. In this case, the filler wire 5 is inserted into the melt 10 between the preceding electrode 3 and the following electrode 4. In this embodiment, the space | interval distance between the preceding electrode 3 and the following electrode 4 is 15-50 mm. In addition, the filler wire 5 is fed so that the filler wire 5 may be positive (wire minus), and this feed current density is 88 (A / mm <2>) or less, for example. A set of the leading electrode 3, the trailing electrode 4 and the filler wire 5 are respectively disposed on both sides of the standing plate 2 and welded simultaneously on both sides of the standing plate 2.

In this horizontal fillet welding, the molten metal 8 is formed by the preceding electrode 3 and the trailing electrode 4, and the molten metal 8 is solidified to form the molten metal 7. The molten slag 9 floats on the molten metal 7. In addition, the radial portion extending from the preceding electrode 3 and the trailing electrode 4 toward the molten metal 8 represents an arc from each electrode.

Next, the reason for numerical limitation mentioned above is demonstrated.

"Interpolar distance between a leading electrode and a trailing electrode: 15-50 mm"

In the present invention, it is essential that the gap between the leading electrode and the trailing electrode is 15 to 50 mm. Here, the distance between the poles is the distance between the wire tips at each electrode. When welding is performed using a DC power source, the distance between the leading electrode and the trailing electrode becomes a problem in terms of magnetic arc blow and formation of one molten pool. If the distance between the poles is smaller than 15 mm, the arc is not stabilized in both the preceding electrode and the trailing electrode, the appearance and shape of the bead become poor, and the amount of spatter generated increases. On the other hand, if the distance between the poles is larger than 50 mm, it is impossible to form one melted paper with two electrodes, resulting in poor fit resistance. Therefore, the distance between the poles of the preceding electrode and the trailing electrode is in the range of 15 to 50 mm. Moreover, the more preferable range is 25 to 35 mm.

"Filler Wire and Its Polarity: Reverse Electrode (Wire Plus) for Leading Electrode and Trailing Electrode, Positive Electrode (Wire Minus) for Filler Wire"

In the present invention, the leading electrode and the trailing electrode are DCEP (Direct Current Electrode Positive), and the filler wire is positive polarity (wire minus). In the present invention, the filler wire 5 is inserted into the molten metal 10 in the molten metal 8 (pool) formed between the preceding electrode 3 and the trailing electrode 4. As this filler wire 5, a solid wire or a flux containing wire can be applied. In the case of a solid wire, it may be a conventional plated solid wire, or may be a non-plated solid wire which is recently expanding its application range. In particular, the component may be appropriately selected from YGW11 to YGW24 specified in JISZ3312 without any provision. In the case of a flux containing wire, adjustment of a component is easy and you may change the component of the wire used for the preceding electrode 3, and the component of the wire used for the trailing electrode 4. As shown in FIG. Moreover, the wire which filled the flux which mainly uses what is called metal type among the flux containing wires is preferable. Since the filler wire is mainly melted by resistance heating, powder having a high melting point such as a slag forming agent may be left to melt, and if it is a metal type, it is easily melted because it is almost a metal powder. In addition, when a filler wire is a flux containing wire, filler wire supply amount and filler wire welding speed may not correspond. That is, although it is a case of the flux containing wire in which the component which becomes a slag is contained among the filler wire components, the welding speed which becomes a welding metal may be controlled either.

The filler wire is also inserted between the leading and trailing poles to mitigate the arc interference of the leading and trailing poles. Since both the leading electrode and the trailing electrode are reverse polarities, the direction of the magnetic field generated around each electrode becomes the same. When the filler wire is not inserted, the magnetic field weakens each other between the leading pole and the trailing pole. As a result, there is a reduction (arc interference) in which the arcs of the leading and trailing poles attract each other, resulting in unstable melt. However, when the filler wire is inserted at the wire minus, the magnetic field in the opposite direction to the preceding and trailing poles is generated, and as a result, the effect of canceling the magnetic fields of the preceding and the following poles can be reduced. For this reason, the filler wire is inserted into the molten metal in the molten metal (pool) formed between the preceding electrode and the trailing electrode.

In the normal gas shielded arc welding, the preceding electrode and the trailing electrode are reverse polarity of the wire plus.

In any case, it is essential to insert the filler wire 5 into the molten steel 10 and to supply a current having a positive polarity (wire minus) to the filler wire for stabilization of the molten oil 10. When the polarity is reversed, the influence of various obstacle factors ((a) the excessive gap of the fillet weld, (b) the excessive coating film thickness of the shop primer, (c) the current voltage fluctuation in the factory, etc.) cannot be solved. Similarly to the problem when the inter-pole distance is less than 15 mm, both the leading electrode and the trailing electrode are not stabilized in arc, and the appearance and shape of the bead become poor. In addition, problems such as an increase in the amount of spatter generated occur. The bundle of spatters may cause poor shielding due to the attachment of the spatters to the shield nozzles, which may cause pore generation. On the other hand, when a positive current flows through a filler wire, stable melt flow which is not affected by various obstacles is formed. This mechanism is not necessarily clear, but can be considered as follows.

In order to stably form the melts, there are important factors such as the viscosity of the pool and the welding speed, but stable formation of the melts is also achieved by properly balancing the arc generation direction and arc force (pressure caused by plasma airflow) of the two electrodes. Is indispensable. When magnetic arc blow causes the balance of the directionality and the force of the arc to be broken, the melt flow becomes unstable and a healthy welding cannot be performed.

Generally, the phenomenon called magnetic arc blow is considered to be classified into two types, largely for the cause. That is, since the current flowing through the arc through the arc to be welded is an end when the shape is uneven and the shape of the weld itself is asymmetric or complex, or when the end of the weld is welded, the current flows in one direction of the weld. When it is easy to flow, it is a case where the magnetic field produced | generated by the whole electric current which flows to a to-be-welded object becomes uneven for reasons, such as the earth position of a to-be-welded object. According to the shape of the structure and the method of taking the earth line, the first magnetic arc blow phenomenon is that the arc is deflected by the influence of the inclination of the magnetic field near the earth generating point. In this case, the entirety of the plurality of arcs of the multi-electrode construction method is affected, causing problems such as deflection in one direction. As a countermeasure against this, a conventional method of providing a plurality of earth positions has been proposed. The present inventors considered that lowering the total current flowing through the welded object can reduce the inclination of the magnetic field near the molten pool. As a concrete measure, it was considered that it is appropriate to insert the filler wire into the molten paper and to flow the current in the opposite direction to lower the total current value flowing through the welded object. By inserting the positive filler wire between the two electrodes of reverse polarity, since the direct current flowing through the structure near the pool becomes the value obtained by subtracting the current of the filler wire from the sum of the currents of the two electrodes, the slope of the magnetic field becomes small. For this reason, it is thought that magnetic arc blow was difficult to occur.

3, the above description is supplemented. i ₁ represents a welding current flowing in the preceding electrode, i ₂ represents a welding current flowing in the trailing electrode, and i ₃ represents a current flowing in the filler wire. When the filler wire is not inserted, the total current flowing through the workpiece is i ₁ + i ₂ . However, by inserting a filler wire so that i ₃ flows in the opposite direction, the total current flowing through the welded object becomes i ₁ + i _2- i ₃ , and the current content of i ₃ decreases. Therefore, the magnetic field generated by the total current is also reduced, and the magnetic arc blow is reduced by the entire current flowing through the object to be welded.

Another cause of the magnetic arc blow is interference between two arcs by the preceding electrode and the trailing electrode constituting the two-electrode one pool. Conventionally, the melt flow is considered to be stable because the molten metal sandwiched by the leading electrode and the trailing electrode is suppressed by the arc force of the preceding electrode and the trailing electrode, and the two arcs are adjusted in the direction of pulling each other (the direction in which the melt flows push each other). In the present invention, it has been found that the flow of water flows in the opposite direction to the filler wire, and that the melt flow becomes very stable when an electromagnetic force is applied to each arc in the repulsive direction from the filler wire. The reason is not necessarily clear, but it can be estimated as follows. When the current flows in the same direction through the two electrodes, the force acts in the direction of attraction to each other under the influence of the magnetic field of each current, and in this state, the balance is good while making the melt, but, for example, magnetic arc blow, etc. In this situation, the arcs are attracted to each other beyond the melt flow, or when the gap is large and the pool is lowered to eliminate the melt flow, the arc is directly pulled together. Once this is done, it can be inferred that it is difficult to reform the stable melts. It is considered that the proper melt water existing between the two electrodes serves to mitigate the interference of the arc. If there is a filler wire that causes current to flow in the opposite direction between the two electrodes, the magnetic field caused by the current of the two electrodes is canceled to some extent, so that the two electrodes are less attracted to each other and the interference of the arc is reduced. . Therefore, in this invention, it is a big point to make electric current flow to a filler wire in the direction opposite to a welding current.

In addition, the insertion of the filler wire also brings about another effect of stabilizing the melts in the present construction method, which is a two-electrode one pool. That is, the increase in the weld metal by the filler wire is thought to be very effective for supplying molten metal at a lower temperature than the arc, and supplying the molten metal to the molten metal part. By inserting the filler wire, the weld metal increases, the melts become large, and the temperature of the melts decreases (because no arc is generated). Increasing melt flow is a direction to reduce magnetic arc blow, and it is presumed that lowering the temperature of the melt is also effective in suppressing fluctuation of the melt due to a decrease in fluidity of the molten metal.

"The sum L + T of the welding speed L (g / min) of a lead electrode and the welding speed T (g / min) of a trailing electrode is 100-500 g / min."

When L + T is less than 100 (g / min), since the amount of weld metal is too small, a bead shape becomes convex and a good undercut cannot be formed, such as a bunch of undercuts. In addition, when L + T exceeds 500 (g / min), since the amount of weld metal is excessive, the melted water is not stabilized, and as a result, the bead shape does not become uniform and the appearance of the beads (alignment) is disturbed. Moreover, in order to obtain a good bead shape, More preferably, L + T is 140-460 (g / min).

"Deposition rate F (g / min) of filler wire is 0.03 (L + T) to 0.3 (L + T)"

Since the filler wire 5 does not have an arc, the amount of the weld metal of the filler wire 5 does not take much part in the magnitude of the length of the weld bead. For the size of the weld bead length, the weld metal amount of the preceding electrode and the following electrode is dominant. Therefore, when the welding speed F of the filler wire 5 exceeds 0.3 (L + T), the welding metal amount of the filler wire with respect to the weld bead length corresponding to the welding metal amount of the preceding electrode 3 and the following electrode 4 is excessive. The bead shape becomes convex. On the other hand, when F is less than 0.03 (L + T), the effect of improving the stability of the molten metal 10 by the filler wire decreases, and as a result, the appearance of the beads and the shape of the beads deteriorate. Therefore, the welding speed F (g / min) of a filler wire shall be 0.03 (L + T)-0.3 (L + T). Further, in order to obtain a good bead shape, the welding speed F is more preferably 0.035 (L + T) to 0.100 (L + T).

`` F / (j ² Eβ ² ): 3.0 × 10 ⁻⁵ to 30.0 × 10 ⁻⁵ (g · mm / A ² · min) ''

In the filler wire used in normal TIG (tungsten inert gas welding), the melt energy is imparted by the TIG arc, and it is considered that the energy imparted from the molten metal after contact with the molten metal is not dominant. However, since the filler wire in the present invention is not in a position directly exposed to the arc between the leading electrode and the trailing electrode, the melt energy of the filler wire is affected by Joule's heat and the melt flow of the molten paper by the current flowing through the filler wire. It depends on the energy by heating from the molten pool after being inserted. Therefore, an appropriate relationship exists between the welding speed (feeding amount) of a welding filler wire, and the energy amount given to a filler wire. That is, in order to supply a predetermined filler wire to the hot water and to perform smooth melting and good control of the hot water, there is an appropriate condition range. As mentioned above, the ratio of indirectly obtaining and melting the arc heat of the leading electrode and the trailing electrode in the melting of the filler wire is thought to contribute little to the observation result of the welding phenomenon. Melting due to heat generation and Joule heat generation due to current flowing through the filler wire. In other words, the state in which the filler wire is smoothly supplied to the melt flow indicates that since the fed filler wire is not completely melted, the Joule heat generation alone is insufficient as the energy required to melt the melted wire. The branches indicate that there is absorption from the energy. In other words, the energy absorption from the molten metal of the melt to the filler wire is reflected in the cooling effect of the melt from the filler wire to the molten metal.

Therefore, the present inventors conducted several confirmation tests, and found out that it is useful to make the appropriate range controlled by the said relational expression between the appropriate filler wire supply amount (welding speed) F and Joule heat generation of a filler wire.

That is, in this invention, it is thought that the characteristic (viscosity, temperature, etc.) of hot water dominates as a factor which forms a bead shape. In addition, the characteristics of the melt flow dominate the Joule calorific value of the filler wire. If the resistance of the filler wire is R (Ω), the conduction current is I (A), the current density is j (A / mm2), and the diameter of the filler wire is β (mm), the Joule calorific value is I ² R = (j × π (β / 2) ² } ² is proportional to R. Further, when the protruding length (chip-to-base metal distance) of the filler wire is set to E (mm), R is proportional to E / {π (β / 2) ² }. For this reason, the Joule calorific value is proportional to {j × π (β / 2) ² } ² × E / {π (β / 2) ² } = (π / 4) j ² Eβ ² , and therefore, j ² Eβ ² Proportional.

On the other hand, since the appropriate welding wire F (g / min) has a proportional relationship with Joule calorific value, it is considered that the ratio of F and j ² Eβ ² has an appropriate range. Therefore, in the present invention, in order to obtain a good bead shape, the range of F / (j ² Eβ ² ) is defined because the wire welding speed F is defined on the basis of the amount of heat to be decreased.

That is, when F / (j ² Eβ ² ) is less than 3.0 × 10 ⁻⁵ (g · mm / A ² · minute), since the Joule heat generation amount of the filler wire is too large for the welding speed of the filler wire, As a result, the cooling effect of the melts is small and the melts become unstable, resulting in non-uniform bead shape and deterioration of the appearance of beads, in particular, deterioration of alignment. In addition, when F / (j ² Eβ ² ) exceeds 30.0 × 10 ⁻⁵ (g · mm / A ² minutes), since the Joule heat generation amount of the filler wire is too small for the welding speed of the filler wire, the filler wire The cooling effect of the hot water by addition becomes excessive, and as a result, a bead shape becomes convex. In addition, the occurrence of undercuts also occurs.

"Current density j of filler wire: 88 (A / mm 2) or less"

When the current density of the filler wire exceeds 88 (A / mm 2), since the current value is large, it is effective from the viewpoint of alleviating the arc interference of the leading electrode and the trailing pole, but since the Joule heat generation amount becomes excessive, the cooling effect of the hot water is increased. There exists a tendency for lack, and as a result, there exists a tendency for the bead-shaped nonuniformity, overlap, etc. to occur easily. For this reason, in one aspect of this invention, the current density of a filler wire shall be 88 (A / mm <2>) or less.

"Current density j of the filler wire: 88 (A / mm 2) or more"

If the current density of the filler wire is less than 88 (A / mm 2), since the current value is small as described above, it is advantageous from the viewpoint of stabilization due to the cooling effect of the hot water, but the cooling rate of the molten pool increases, resulting in a good bet. Sieges tend not to be secured. For this reason, in another aspect of the present invention, the current density of the filler wire is set to 88 (A / mm 2) or more in the case where emphasis is placed on porosity resistance. Under this condition, the resistance heating of the filler wire reduces the cooling effect of the molten pool, increases the time for which the combustion gas of the primer in the molten pool can be released, and consequently, the porosity resistance is improved. However, when the current density is 105 (A / mm 2) or more, the filler wire deviates from the molten pool and the generation of arc occurs frequently, making it difficult to maintain stable formation of the melts. In this case, it is effective to use a filler wire power supply having a function of preventing arc generation.

"The arc value does not generate | occur | produce from the said filler wire by individually controlling the electric current value and the supply amount of the said filler wire."

In this invention, it is preferable that the viscosity and temperature of a molten pool can be changed by changing the Joule calorific value supplied from a filler wire to a molten pool. In the method of this invention, welding itself by the commercially available constant current characteristic power supply is possible as a power supply for filler wires. However, in the commercially available constant voltage power supply, since the wire supply amount and the current density cannot be controlled independently, it is difficult to control the Joule heat generation amount supplied from the filler wire to the molten pool. In addition, an arc does not occur in a commercially available constant voltage characteristic power supply, and the range of conditions for forming a stable molten pool is small, and the advantages of the present construction method are impaired. Therefore, in order to obtain a good welding bead without generating an arc from the filler wire by carrying out the present construction method, it is preferable to use a power source capable of independently controlling the current value (current density) and the wire supply amount as the power source for the filler wire. desirable.

In addition, when the current density is 88 A / mm 2 or more (more preferably 105 A / mm 2 or more), the porosity resistance is improved by the decrease in the viscosity of the molten pool or the cooling effect of the molten pool due to the insertion of the filler wire. However, under this condition, since the Joule heat generation amount of the filler wire is large, it is a condition where an arc tends to be generated from the filler wire, and when an arc is generated, the molten pool becomes unstable, so that formation of good weld beads becomes difficult. Therefore, in order to maintain the stability of the molten pool under the condition of a current density of 88 A / mm 2 or more, the voltage between the filler wire and the base metal is not used as the filler wire power supply, but rather the function of individually controlling the wire feed amount and the current value. When detecting and exceeding a certain voltage (corresponding to the detection of arc generation), it has a function of suppressing melting of the filler wire by instantly reducing the current value to 10 A or less regardless of the set current, and preventing the generation of arc. It is more preferable to use the power supply for filler wires.

As an example of realizing this function, when the voltage between the filler wire and the base material exceeds a predetermined voltage and the occurrence of an arc is detected, the melting of the filler wire is suppressed by instantly reducing the current value to 10 A or less regardless of the set current. As a result, the power supply requires a function of performing current control so that the filler wire contacts the molten pool again.

In view of the above, in the case of focusing on porosity resistance, the current density of the filler wire is set to 88 (A / mm 2) or more, and more preferably, the voltage between the filler wire and the base metal is controlled so as to prevent arcing from the filler wire. When the occurrence of the arc is detected in excess of the predetermined voltage, it is necessary to immediately reduce the current to a very small current regardless of the set current to suppress the melting of the filler wire.

Other welding conditions are no different from conventional two-electrode tandem welding. The conditions which it is desirable to regulate as needed are as follows.

`` Wire diameter ''

The diameter of the wire of the preceding electrode (referred to as wire diameter) is 1.2 to 4.0 mm, the diameter of the wire of the trailing electrode is 1.2 to 4.0 mm, and the relation of (wire diameter of the leading electrode) ≥ (wire diameter of the trailing electrode) Preferably, the wire diameter greatly affects the stability of the arc, the stability of the molten pool, and the appearance of the beads, especially in the case of a multi-electrode, the balance of the wire diameters of the preceding electrode and the following electrode is also important.

In other words, if the wire diameter of the preceding electrode is smaller than 1.2 mm, the arc is not stabilized and the bead shape is poor. If it is larger than 4.0 mm, the amount of spatter generated from the preceding electrode increases. In addition, when the wire diameter of the trailing electrode is smaller than 1.2 mm, the arc is not expanded and the appearance and shape of the bead become poor. Further, when larger than the preceding electrode, the arc and the molten paper in the trailing electrode become unstable, and the amount of spatter generated from the trailing electrode increases. Therefore, the relationship between the wire diameters of the preceding electrode and the following electrode is as described above.

"Composition of Leading and Trailing Electrodes"

As the preceding electrode and the trailing electrode, any of the flux-containing wires is applied. Any of a titania-based flux-containing wire mainly composed of rutile or a so-called metal-based flux-containing wire may be applied.

In addition, for flux-containing wires used for the preceding electrode and the following electrode, a composition suitable for the multi-electrode construction method is more preferable than the one specifically designed for a normal single electrode. That is, since one melted paper is formed by the flux-containing wires of both the preceding electrode and the trailing electrode, there is no particular limitation on the composition, but a particularly preferred wire composition is oxide per mass of wire in the case of titania-based flux-containing wires. TiO ₂ , SiO ₂ , MgO, Al ₂ O ₃ , FeO, Fe ₂ O ₃ , ZrO _2, and the like) are 1.5 to 5.5 mass%. If the oxide is less than 1.5% by mass, the slag covering the surface of the bead is smeared and the appearance and shape of the bead deteriorates. On the other hand, when the oxide exceeds 5.5% by mass, the amount of slag becomes excessive and the flowability of the slag increases, so that the alignment of the bead end portions deteriorates. Therefore, an oxide is taken as the range of 1.5-5.5 mass%. In addition, rutile, aluminate, zircon sand, alumina, magnesia, silica sand, etc. are mentioned as a raw material of an oxide.

Alkali metal oxides (K ₂ O, Na ₂ O and Li ₂ O equivalents) can be variously applied, and must contain 0.01 to 0.15 mass% per mass of wire in total. If these alkali metal oxides are less than 0.01 mass%, stability of the arc cannot be obtained. On the other hand, when the alkali metal oxide exceeds 0.15% by mass, the ejection of the arc becomes so strong that the molten pool is not stabilized. Moreover, since the raw material of an alkali metal oxide is easy to absorb moisture, the moisture resistance of the whole wire tends to deteriorate. Thus, the alkali metal oxide is a K ₂ O, Na ₂ O and one or more kinds of Li ₂ O in the range of 0.01 to 0.15 mass%. Further, as the raw material of _{K 2 O, Na 2 O,} Li 2 O it may be a feldspar, soda glass, potassium glass, and the like.

In addition, Mg, Si, Mn is added for the purpose of deoxidizer etc. Examples of the Mg raw material include metal Mg, Al-Mg, Si-Mg, and Ni-Mg. Fe-Si, Fe-Si-Mn, etc. are mentioned as Si raw material. Examples of the Mn raw material include metal Mn, Fe-Mn, Fe-Si-Mn, and the like.

In addition, the composition to be contained is iron, fluoride, bismuth oxide and the like. Particularly preferred wire composition in the case of a metal flux-containing wire is 1.5 mass% or less of oxides (TiO ₂ , SiO ₂ , MgO, Al ₂ O ₃ , FeO, Fe ₂ O ₃ , ZrO _2, etc.) per wire total mass. Instead, the metal raw material contains 98 mass% or more per wire total mass. In other words, it is preferable to contain 94 mass% or more of metal raw materials per flux in a flux. The metal raw material is iron or iron alloys such as Fe-Mn and Fe-Si. As the arc stabilizer, alkali metal oxides (K ₂ O, Na ₂ O and Li ₂ O equivalents) can be applied to various kinds similar to titania, and must be contained in total in the range of 0.01 to 0.15% by mass per wire total mass. If these alkali metal oxides are less than 0.01 mass%, stability of the arc cannot be obtained. On the other hand, when the alkali metal oxide exceeds 0.15% by mass, the ejection of the arc becomes so strong that the molten pool is not stabilized. In addition, since the raw material of the alkali metal oxide is easily absorbed, the hygroscopic resistance of the entire wire is likely to deteriorate. Thus, the alkali metal oxide is a K ₂ O, Na ₂ O and one or more kinds of Li ₂ O in the range of 0.01 to 0.15 mass%. Further, as the raw material of _{K 2 O, Na 2 O,} Li 2 O it may be a feldspar, soda glass, potassium glass, and the like. In addition, Mg, Si, and Mn are similarly added.

Regarding the composition of the filler wire, considering that the three wires of the preceding electrode, the trailing electrode, and the filler wire are melted to form a molten pool, the composition of the filler wire is adjusted according to the composition of the preceding electrode and the trailing electrode so as to form a desired molten pool. Just do it.

`` Forward, backward angle ''

As shown in Figs. 1 and 2, each electrode is positioned at an angle from a vertical line in the direction of progress of welding. The angle tilted in the advancing direction is called the retreat angle, and the angle tilted in the direction opposite to the advancing direction is called the forward angle. It is preferable that the angle of the wire of the preceding electrode is 0 to the retreat angle 15 °, and the angle of the wire of the trailing electrode is 0 to the 25 degree advancing angle. Advance and retreat angles greatly affect the amount of spatter and bead shape. When the leading electrode reaches the forward angle, the amount of spatter generated from the preceding electrode increases, and when the retracting angle becomes larger than 15 °, undercut tends to occur. When the trailing electrode reaches the retreat angle, the arc is not stabilized and the amount of spatter generated increases. When the advancing angle is larger than 25 °, the appearance and shape of the bead become poor. Therefore, the wire angles of the preceding electrode and the following electrode are as described above.

`` Torch angle ''

As shown in FIG. 1, FIG. 2, although each electrode is inserted from the middle direction of the lower board 1 and the standing board 2, the angle from the lower board 1 is called a torch angle as a perpendicular line of a welding progress direction. It is preferable that the torch angle is 40 to 60 ° for both the leading electrode and the trailing electrode. Torch angle greatly affects bead shape and bead appearance. If it is smaller than 40 °, undercut is likely to occur in the lower plate, and if it is larger than 60 °, undercut is likely to occur in the upper plate. Therefore, the torch angle is as described above for both the preceding electrode and the trailing electrode.

`` Welding current ''

Direct Current Electrode Positive (DCEP) of 250 A or more, Direct Current Electrode Positive (DCEP), Post Current Electrode Current of Leading Electrode (DCEP) of 200 A or More It is preferable to set the relation to. This is generally a current required to ensure 4.0 mm of the square length required for the fillet welds of the welded structure, and if it is less than the current, the arc will not be stabilized. In addition, when the current of the preceding electrode is smaller than the current of the following electrode, the arc of the preceding electrode is disturbed by the interference of the arc at the preceding electrode and the following electrode, so that the appearance and shape of the bead become poor. Therefore, the relationship between the current and both of the preceding electrode and the following electrode is as described above.

Moreover, especially when the said construction method is performed by twin welding, it turned out that the said objective can be achieved on the conditions shown below.

`` Shift interval ''

It is preferable to make the shift interval of both the preceding electrode and the following electrode which sandwiches a standing board into 0-30 mm or 70 mm or more. Since a spatter generate | occur | produces more often and a workability | operativity worsens between 30-70 mm of shift intervals, it is set as the shift interval except this time.

Moreover, in order to implement this invention more effectively, adjustment of the target position (namely, distance from a wire tip to a standing board) becomes an important point. The target position greatly influences the securing of the melting power, the formation of beads having good appearance and shape, the stability of the melted paper and the porosity resistance. For this purpose, the target position of the preceding electrode is 0 to 2 mm lower than the root side, and the target position of the trailing electrode is 0 to 3 mm lower than the root side. It is preferred to be close or identical.

It is necessary to adjust the target position of the preceding electrode in order to secure the dissolving power. If the target is on the plate plate side, undercut is liable to occur in the plate plate, and the shape of the bead becomes poor. It is impossible to secure the strength of the fillet portion in that the beads are not conformal. In addition, it is necessary to adjust the target position of the trailing electrode in order to improve the appearance and shape of the beads, and if the purpose is smaller than the lower plate side 0 mm (plate plate side) or larger than 3 mm, the molten paper is not stabilized and the appearance and shape of the bead This becomes poor and the generation amount of spatter increases. Further, when the target position of the trailing electrode is closer to the root than the target position of the preceding electrode, the porosity resistance is poor, the melted paper is not stabilized, and the appearance and shape of the bead become poor. Therefore, the relationship between the target position of a preceding electrode and a following electrode, and both is as mentioned above.

EXAMPLE

Hereinafter, the Example (Test Example A and Test Example B) of this invention is demonstrated in contrast with the comparative example deviating from the range of this invention. Table 1 below shows the welding test conditions.

In addition, Table 2 below shows evaluation criteria.

In Test Example A and Test Example B, the bead shape was evaluated by H / L in FIG. In this case, evaluations 5 to 2 maintain uniformity in the bead longitudinal direction even when the bead shape is poor. Evaluation 1 is a case where the uniformity in the longitudinal direction of the bead shape is also hindered.

In Test Example A and Test Example B, the appearance of the beads was evaluated by the sum of the number of misaligned points and the number of undercut points (pieces / 1000 mm). Spatter was evaluated by the amount of spatter generated. In addition, porosity resistance was evaluated by the number of pit occurrences (pieces / 1000 mm) on one side in the porosity resistance test. However, it evaluated by the number of pit occurrences in the bead with many pits among the two beads formed in the both sides of the standing board. In addition, the porosity evaluation criteria in Test Example A are as shown in Table 1. About the test example B, the case where a pit generate | occur | produced was made into x and the case where it did not generate was (circle). In Test Example A, the evaluation focused on the appearance and shape of the beads, and in Test Example B, the evaluation focused on the porosity resistance.

`` Test Example A ''

Table 3 below shows the welding conditions of Test Example A, and Table 4 shows the welding results of Test Example A. However, test no. 3 and 10 are welding speeds of 100 cm / min. 5 and 7 were welded at the welding speed of 150 cm / min and other than the welding speed of 200 cm / min.

As shown in Tables 3 and 4, in Comparative Examples 1 and 2, L + T is out of the range of the present invention, while in Comparative Examples 3 and 4, F / (L + T) is out of the range of the present invention, the bead shape, bead appearance, The evaluation was low in both spatter generation and porosity resistance. On the other hand, since Examples 1-8 were in the scope of the present invention, evaluation of these characteristics was all excellent in "3" or more. In addition, Examples 7 and 8 were inferior to Examples 1 to 6 in that the conditions of F / (j ² Eβ ² ) defined in the present invention were not satisfied.

`` Test Example B ''

Table 5 below shows the welding conditions of Test Example B, and Table 6 shows the welding results of Test Example B. In Comparative Example 17 of Table 5, however, the welding speed was 150 cm / min, and the welding speed was 200 cm / min.

In addition, in Table 5, when the voltage between the filler wire and the base material exceeds the predetermined voltage and the occurrence of the arc is detected in the power supply function column for the filler wire, a very small current is instantaneously regardless of the set current. By reducing the melting of the filler wire, a power source having a function of controlling current so that the filler wire contacts the melt pool is used again, and "A" refers to a case of using a power source having no such function.

As shown in Tables 5 and 6, in Comparative Example 16, the current density j was less than 88 (A / mm ² ), resulting in poor porosity resistance. In Comparative Example 17, although the current density j was 88 (A / mm ² ) or more, since the power supply provided with the function of controlling the arc not to be used was not used, the appearance and shape of the beads were disturbed. In contrast, Examples 13 to 15 have a function of controlling the arc from the filler wire when the current density j is 88 (A / mm ² ) or more and the current density j is 105 (A / mm ² ) or more. Since the power source is used, evaluation of "beads", bead appearance, spatter, and the like are all "4" and excellent in porosity resistance.

1 is a perspective view showing a multi-electrode gas shield arc welding method according to an embodiment of the present invention.

FIG. 2 is an enlarged longitudinal sectional view showing the weld metal part of FIG. 1. FIG.

3 is a planar circuit diagram showing a multi-electrode gas shield arc welding method according to an embodiment of the present invention.

4 is a bead cross-sectional view showing a bead shape.

Claims (6)

Flux-containing wire for gas shield arc welding is used as a leading electrode and a trailing electrode, the gap distance between the leading electrode and the trailing electrode is set to 15 to 50 mm, and the filler wire is melted between the preceding electrode and the trailing electrode. In the multi-electrode gas shielded arc welding method, which is inserted into the welding electrode, a reverse polarity current flows through the preceding electrode and a trailing electrode, and a positive current (wire minus) flows through the filler wire, and the welding is performed. The sum L + T of the speed L (g / min) and the welding speed T (g / min) of the trailing electrode is 100 to 500 g / min, and the welding speed F (g / min) of the filler wire is 0.03 (L + T) to 0.3 (L + T). A multi-electrode gas shielded arc welding method, characterized in that). The method of claim 1, When the current density of the filler wire is j (A / mm 2), the chip-base metal distance is E (mm) and the wire diameter is β (mm), F / (j ² Eβ ² ) is 3.0 × 10 ^−5. To 30.0 × 10 ⁻⁵ (g · mm / A ² · min). The method according to claim 1 or 2, And the current density j of the current flowing in the filler wire is 88 (A / mm 2) or less. The method according to claim 1 or 2, The current density of the current flowing through the filler wire is 88 (A / mm 2) or more, and the current value and the supply amount of the filler wire are individually controlled to prevent arcing from the filler wire. Multi-electrode gas shield arc welding method. The method according to claim 1 or 2, And controlling the current value and the wire feeding amount of the filler wire by using a power source capable of independently controlling the current value and the wire feeding amount of the filler wire, respectively. The method according to claim 1 or 2, When the voltage between the filler wire and the base metal is detected and the voltage exceeds a predetermined value, a filler wire power supply having a function of reducing the current value to 10 A or less regardless of the set current is used. Electrode Gas Shield Arc Welding Method.

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