JP3333305B2 - Gas shielded arc welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas shielded arc welding method used for welding a steel structure, and more particularly to a high speed gas having excellent workability and high pore resistance (pit and blow hole) at high speed welding. It relates to a shielded arc welding method.

[0002]

2. Description of the Related Art Conventionally, in gas shielded arc welding, a plurality of electrodes have been used in order to improve the efficiency of welding work.
A welding method for performing welding at a high current and at a high speed has been studied, and a part thereof has been put to practical use. Conventional high-speed gas shield welding methods include the following.

(1) A first electrode having a diameter of 0.6 to
A 1.6 mm welding wire is used, and a welding wire having a diameter of 3.0 to 6.4 mm is used for each of the subsequent second and subsequent electrodes, and the distance between the electrodes is set to 100 mm or more.
A welding current of 100 to 500 A is supplied to the electrode, and the second
A gas shielded arc welding method in which a current of 600 to 1500 A is supplied to each electrode after the electrode and an inert gas is used as a shielding gas (Japanese Patent Publication No. 58-13269).

(2) One or a plurality of electrodes using a flux-cored welding wire having a diameter of 1.6 to 6.4 mm
A high-speed gas shielded arc welding method for forming a single molten pool by supplying a welding current of 0 to 2000 A and performing welding at a welding speed of 6 m / min or more (Japanese Patent Laid-Open No. 63-154267)
issue).

(3) The first first electrode has a diameter of 1.4 m.
m or more, and a titania-based flux-cored wire having a diameter of 1.4 mm or more is used for at least the last electrode of the second and subsequent electrodes in the succeeding electrode, and the distance between each electrode is 50 mm or less. -Speed gas shielded arc welding method in which welding is performed as
No. 235077).

(4) Each electrode is arranged so that one pool is formed with the distance between the preceding first electrode and the succeeding second electrode being 10 to 40 mm, and the second electrode has a diameter of 1.2 to 40 mm. A high-speed horizontal gas shielded arc welding method using a 4.0 mm titania (rutile) flux-cored wire, wherein the wire diameter of the first electrode is equal to or less than the wire diameter of the second electrode (Japanese Patent Laid-Open No. 2-280968).

[0007]

However, the above-described gas shielded arc welding method has the following problems. That is, in general, when a large diameter wire having a diameter of 2.4 mm or more is used at a high wire feeding speed (high current), the rigidity is higher than that of a small diameter wire having a diameter of 2.0 mm or less. In addition, the feedability of the wire is reduced, and the arc length tends to fluctuate. For this reason, the frequency of occurrence of welding defects increases.

Further, the maximum capacity of a generally used gas shielded arc welding machine is 750 A, and a special large capacity welding machine is required for welding at a higher current than that. Costs are extremely high.

Furthermore, in high-speed welding with three or more electrodes, if each electrode forms an independent weld pool, the weld pool must be reduced in size. In view of the nature, the permissible range of the target position of each wire becomes extremely narrow.

When the number of electrodes is two or less, and when the welding current (wire feeding speed) is not more than the upper limit value, which is limited in terms of workability and defect resistance, it is higher than the multi-electrode method of three or more electrodes. Welding amount cannot be obtained. Therefore, the welding speed must be reduced.

The present invention has been made in view of the above problems, and does not require a special large-capacity welding machine, has a wide allowable range of wire target positions, and performs operations such as bead appearance / shape and arc stability. It is an object of the present invention to provide a gas shielded arc welding method which is excellent in weldability and does not generate welding defects such as pits, blowholes and poor fusion.

[0012]

SUMMARY OF THE INVENTION A gas shielded arc welding method according to the present invention precedes a gas shielded arc welding method using at least three flux-cored welding wires having a diameter of 1.4 to 1.6 mm. The distance between the first electrode and the subsequent second electrode is 15 to 40 mm, and the distance between the second electrode and the subsequent third electrode is 70 mm.
mm or more, and wires of the first electrode and the second electrode
The slag forming agent content is 1 to 6% by mass,
The slag forming agent content of the wire of the three electrodes is 3 to 8% by mass
With it, a welding current of each electrode as a following direct current <br/> 750A, the the first and second electrodes to form a first molten pool to form the second molten pool by the third electrode 2
The welding is performed at a welding speed of at least m / min.

[0013]

The present inventors have conducted various experimental studies to develop a gas shielded arc welding method that does not require a special large-capacity welding machine and can perform high-speed welding at 2 m / min or more without generating welding defects. Was done. As a result, in a gas shielded arc welding method using at least three welding wires, a welding wire having a predetermined diameter is used, and a first molten metal (first molten pool) is formed by a preceding first electrode and a succeeding second electrode. One molten pool is formed, and a third electrode is disposed at a distance from the second electrode by a predetermined distance, and a third molten pool is formed by the third electrode. It has been found that by setting the welding speed to a predetermined speed or more, a large-capacity welding machine is not required, and good welding without welding defects is possible.

The reasons for limiting the numerical values in the present invention will be described below.

When the diameter of the welding wire is less than 1.2 mm, the wire is not sufficiently rigid, so that the wire is bent at the outlet of the torch under the influence of the feed path. The habit is attached, and the target position is easily shifted. Usually, in high-speed welding, the arc length is shortened in order to stabilize the molten pool, so that the width of the arc and the molten pool is reduced. In this case, even if the wire aiming position is slightly shifted, deterioration of the bead appearance and shape becomes remarkable. Further, when the diameter of the wire is small, the rigidity is small, and buckling is likely to occur during feeding. Therefore, the diameter of the welding wire is 1.2 m
m or more.

On the other hand, in order to obtain a high welding amount, it is necessary to feed a large-diameter wire at a high speed and to weld with a high current. However, in gas shielded arc welding, the wire feeding path is longer than that of submerged arc welding or the like, so the upper limit of the diameter of the wire is limited in that the high-speed wire feeding is stabilized. That is, the wire diameter is 2.0 m
If it exceeds m, the wire feedability is reduced and the wire protrusion length (ie, arc length) fluctuates, so that the bead appearance and shape are deteriorated, the amount of spatter and fume generation is increased, and welding defects are generated. Inconvenience occurs. For this reason, the diameter of the welding wire needs to be 1.2 to 2.0 mm.

When a flux-cored wire is used, its diameter is preferably 1.4 to 1.6 mm. Since the flux-cored wire has excellent arc stability, it is not necessary to use a small-diameter wire having a diameter of less than 1.4 mm, especially in view of workability in high-speed welding. Considering that a large-diameter wire is more advantageous with respect to the allowable range of the wire aiming position and the buckling at the time of feeding, it is usually preferable to use a wire having a diameter of 1.4 mm or more.

On the other hand, since the flux cored wire has a large amount of deposition, a necessary amount of deposition can be secured by low current welding with a relatively small diameter wire. The diameter is 1.6mm
When welding is performed at a high current and a high wire feeding speed using a wire having a diameter larger than the above, the wire feeding property, the bead appearance, the bead shape, and the like are deteriorated. For this reason, the diameter is usually 1.6 mm.
It is preferred to use the following wires: Therefore, when a flux-cored wire is used, its diameter is 1.4.
It is preferably from 1.6 to 1.6 mm.

The flux-cored wire contains a slag-forming agent.
Amount (1) The sum of the contents of the slag forming agent in the wires of the first electrode and the second electrode: 1 to 6% by weight In the present invention, one molten pool (first molten pool) is formed by the first and second electrodes. Form. For this reason, the appearance, shape, and slag removability of the formed bead are greatly affected by the total amount of the slag forming agent contained in the wires of the first and second electrodes. The amount of slag generated in the first molten pool affects the progress of the molten pool (second molten pool) and bead formation by the third electrode. If the total content of the slag forming agent in the wires of the first and second electrodes is less than 1% by weight, the slag is not sufficiently covered, so that the bead appearance and the bead shape are easily deteriorated, and the slag removability is reduced. descend. On the other hand, when the total content of the slag forming agent in the wires of the first and second electrodes exceeds 6% by weight, the amount of slag generated becomes excessive, and the progress of the second molten pool formed by the third electrode is hindered. As a result, welding defects such as slag entrainment and poor fusion occur. In addition, since the amount of slag generated in the second molten pool is also excessive, the slag drips and the bead appearance and bead shape are deteriorated. Therefore, the total amount of the slag forming agent in the wires of the first and second electrodes is preferably 1 to 6% by weight.

(2) Content of the slag forming agent in the wire of the third electrode: 3 to 8% by weight If the content of the slag forming agent in the wire of the third electrode is less than 3% by weight, the slag is not sufficiently covered. As a result, the bead appearance and shape are easily deteriorated, and the slag removability is reduced. On the other hand, when the content of the slag forming agent in the wire of the third electrode exceeds 8% by weight, the slag of the preceding bead is added to the slag from the wire of the third electrode, so that the amount generated is excessive and the slag drips, The bead appearance and bead shape deteriorate. Therefore, the slag forming agent content of the wire of the third electrode is preferably set to 3 to 8% by weight.

Welding speed: 2 m / min or more In the present invention, the welding speed is set to 2 m / min or more from the viewpoint of the welding amount, welding workability, defect resistance and the like.

Welding current: 750 A or less If the welding current exceeds 750 A, a special large-capacity welding machine is required, which significantly increases the cost of the welding machine. Further, in the present invention, since a relatively thin welding wire having a diameter of 2.0 mm or less is used, the welding current is 750 A.
Even below, there is no possibility that a problem such as an insufficient amount of welding occurs. Therefore, the welding current is 750 A or less.

The distance between the electrodes (1) The distance between the first electrode and the second electrode: 15 to 40 mm In the present invention, the first and second electrodes have a large heat input and a wide molten pool (first molten pool). ) Is formed. As a result, it is possible to improve poor conformity between the bead and the base material during high-speed welding, and to obtain a good bead appearance and a good bead shape by eliminating the overlap between the first electrode bead and the second electrode bead. Also, since the penetration is wide and round,
Welding defects such as pores (bits and blowholes) or poor fusion can be suppressed. However, if the distance between the first electrode and the second electrode is less than 15 mm, each electrode needs to take an extreme receding or advancing angle. Then, the molten pool becomes extremely unstable due to the arc force received from the front and back in the direction of the welding line, so that a large amount of spatter is easily generated and the appearance and shape of the bead deteriorate. On the other hand, if the distance between the first electrode and the second electrode exceeds 40 mm, the number of molten pools becomes two,
The above effects cannot be obtained. Further, the interaction between the magnetic fields formed by the electrodes is strengthened, and the transfer of the arc and the droplet becomes unstable, so that a large amount of spatter is easily generated and the bead appearance and shape are deteriorated. Therefore, the distance between the first electrode and the second electrode is 15 mm to 40 m.
m. It is to be noted that an even more preferable distance between the first electrode and the second electrode is 25 to 30 mm.

(2) Interval between the second electrode and the third electrode: 70
If a single molten pool is formed by the first to third electrodes, the molten pool becomes too large, which tends to cause poor shielding, and the amount of heat input becomes excessive, so that welding such as undercut or overlap occurs. Defects occur. Therefore, the third
The electrode must form a second weld pool (second weld pool) by itself. The distance between the second electrode and the third electrode is 70 m
If it is less than m, the interaction between the magnetic fields formed by the electrodes is strengthened, and the arc and droplet transfer become unstable, so that a large amount of spatter is easily generated and the bead appearance and shape deteriorate. Therefore, the distance between the second electrode and the third electrode needs to be 70 mm or more. Note that the more preferable distance between the second electrode and the third electrode is 100 mm or more.

Torch angle and wire aim in fillet welding
In the present invention, the first electrode and the second electrode form a single molten pool having a large and large heat input. For this reason, the adaptation to the base material, which is a problem in high-speed fillet welding, is improved, and the bead formed by the first electrode and the bead formed by the second electrode are eliminated, so that a good bead appearance and bead shape can be obtained. Can be In addition, since the penetration is broad and round, poor fusion hardly occurs. Further, since the solidification of the molten pool is delayed, pores (bits, blow holes, etc.) are raised and released, especially in high-speed fillet welding of paint-coated steel sheets, and a sound joint is obtained. Hereinafter, the reasons for limiting the torch angle and the wire aiming position will be described.

(1) Torch angle First electrode: tilt angle with respect to lower plate 45 to 65 °, receding angle 0 to 15 ° Second electrode: tilt angle with respect to lower plate 45 to 65 °, advance angle 0 to 25 ° Third electrode: the inclination angle with respect to the lower plate is 20 to 60 °, the advance angle is 0 to 30 °. When the torch angle of the first and second electrodes is out of the above range,
In the molten pool (first molten pool) formed by the first and second electrodes, the molten metal is biased to an unstable position. For this reason,
Undercut or overlap easily occurs in the lower plate, the bead appearance / shape is deteriorated, and the slag removability is also reduced. Further, since the molten pool becomes unstable, transfer of droplets is disturbed, and a large amount of spatter is generated.

Further, when the torch angle of the third electrode is out of the above range, undercut or break-in failure of the standing plate is likely to occur. In addition, the overlap or conformity with the preceding bead becomes poor, so that the appearance and shape of the bead deteriorate, and the slag removability also deteriorates. Therefore, it is preferable that the torch angle of each electrode is in the above range.

(2) Wire aiming position First electrode: 0 to 2 mm horizontally from the root Second electrode: 0 mm horizontally from the wire aiming position of the first electrode
Third electrode: 1 to 3 mm vertically from the root Similarly to the torch angle, when the wire target positions of the first and second electrodes deviate from the above range, a molten pool formed by the first and second electrodes. The molten metal is biased to the unstable position in the inside. For this reason, undercut or overlap easily occurs in the lower plate, and bead appearance and shape are deteriorated, slag removability is reduced, and the amount of spatter generated is increased. Also,
If the leg length on the lower plate side is excessively large or short, the entire fillet bead becomes concave or convex.

Even when the target position of the wire of the third electrode is out of the above range, undercut or break-in failure is likely to occur on the standing plate, and overlap or break-in with the preceding bead is poor, and the appearance and shape of the bead are poor. Deteriorates. Also,
If the leg length on the upright side is too large or short, the entire fillet bead becomes concave or convex. Therefore, the wire aiming position of each electrode is set in the above range.

Welding current in fillet welding: 250-6
In the present invention, since welding is performed at a high speed of 2 m / min or more in the present invention, if the welding current is less than 250 A, the heat input or arc force is insufficient, so that the base material and the preceding bead are not sufficiently melted and welding defects such as poor fusion are generated. appear. In addition, since the spread of the molten pool and the amount of welding are insufficient, the appearance and shape of the bead deteriorate. Furthermore, because the molten pool becomes unstable due to the shortage of molten metal,
The amount of spatter generated also increases. On the other hand, the welding current is 650 A
If it exceeds, the amount of heat input or arc force becomes excessive, causing undercut, and the amount of welding becomes excessive, causing overlap. In addition, when the molten metal precedes the arc due to an excessive amount of molten metal, the arc force on the base material and the preceding bead is insufficient, and welding defects such as poor fusion are likely to occur. Occurs. Therefore, the welding current is preferably set to 250 to 650A.

Shielding gas: CO ₂ or CO ₂ -containing gas In the present invention, since welding is performed at a high current, the droplet formed at the tip of the wire is transferred to the molten pool stably without short-circuit due to a sufficient pinch force. . Further, since the first molten pool has a large heat input and a wide molten pool formed by the first and second electrodes, as described above, pores or poor fusion are unlikely to occur. Therefore, it is not necessary to particularly limit the composition of the shielding gas in terms of welding workability, defect resistance, and the like. However, when importance is placed on reducing the cost of the entire welding operation or reducing the number of pores generated in high-speed fillet welding of paint-coated steel plates, it is preferable to use a CO ₂ gas or a CO ₂ -containing gas as the shielding gas.

[0032]

Next, the results of actual high-speed fillet welding performed by the method of the present invention and examination of the welding state will be described in comparison with comparative examples.

As shown in FIG. 1, the thickness (T) is 12 m.
Fillet welding of a T-joint composed of two 490 MPa class high-strength steel plates (standing plate 1 and lower plate 2) having a length of 80 mm and a width (W) of 80 mm was performed. In this case, the root gap was set to 0 mm by machining the lower end surface of the lower plate 1 and applying pressure from above. When welding a steel plate coated with inorganic zinc primer, if the root gap is set to 0 mm, the gas generated by burning the primer by the arc is released through the molten pool, so that pores (pits, blow holes)
Defects are extremely likely to occur. As shown in FIG. 2, the first electrode 5, the second electrode 6, and the third electrode 7 are arranged at predetermined intervals on both sides of the standing plate 1 along the moving direction of the workpiece (indicated by an arrow in the drawing). did. In this case, the first electrode 5,
The amount of shift between the second electrode 6 and the third electrode 7 (the amount of displacement between the first electrodes 5, between the second electrodes 6, and between the third electrodes 7 in the moving direction of the material to be welded) is zero.

Further, based on the conditions shown in Table 1 below, some of the conditions were changed in each test as described later.

[0035]

[Table 1]

The wire diameter were first investigated the relationship between the welding state and the wire diameter of the first electrode. That is, as shown in Table 2 below, welding was performed using welding wires having different diameters. Table 2 also shows the slag forming agent content of the wire. In addition, the first electrode, the second electrode
Tables 3 to 6 below show the welding conditions, the torch angle, the target position, the distance between the electrodes, the welding speed, and the surface condition of the base material for the electrode and the third electrode.

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6]

The leg length, bead appearance / shape, spatter generation amount, slag peeling property and porosity resistance of these Examples and Comparative Examples were examined. The results are shown in Table 7 below. However, the bead appearance and shape were indicated by ◎ when the bead appearance and bead shape were extremely good, ○ when the bead appearance and bead shape were good, Δ when it was not good, and x when it was not very good. Also, the amount of spatter generation is indicated by ◎ when the amount of spatter generation is extremely small, by ○ when the amount of spatter generation is small, by Δ when the amount was large, and by x when extremely large.
Further, the slag peelability was evaluated as follows: 極 め て: extremely good, を: good, △: poor, ×: extremely poor.
Indicated by Furthermore, the porosity resistance is ◎ when the occurrence of pits or blow holes is extremely small, ○ when the occurrence is small,
A large number is indicated by Δ, and an extremely large number is indicated by X. Further, from these results, the quality as a high-speed gas shielded arc welding method was comprehensively evaluated. The results are also shown in Table 7 below.

[0043]

[Table 7]

As is clear from Table 7, the first to third
Example 1 in which the wire diameter of the electrode was 1.2 to 2.0 mm
Comparative Examples 1 to 6 in which the wire diameter of the electrode is 1.0 or 2.4 mm, while Comparative Examples 1 to 9 all have good bead appearance / shape, spatter generation amount, slag peeling property and pore resistance. In addition, at least one of the bead appearance / shape, the amount of spatter generated, the slag removability, and the porosity was not satisfactory.

The slag forming agent next examined the relationship between welding quality and quantity of slag-forming agent.
That is, as shown in Table 8 below, high-speed gas shielded arc welding was performed using welding wires having different contents of the slag forming agent, and the bead appearance / shape, the amount of spatter generated, the slag removability and the pore resistance were improved. The sex was examined. The result is
The results are shown in Table 9 below. However, other conditions are shown in Table 3 ~
It is the same as Table 6.

[0046]

[Table 8]

[0047]

[Table 9]

As apparent from Table 9, Example 10
No. 14 to No. 14 showed good weldability.
And the total content of the slag forming agent in the second electrode is 1% by weight.
Comparative Example 1 having a slag former content of less than 6% by weight
Comparative Example 8 in which the slag content of the third electrode exceeds 3% by weight
Comparative Examples 9 and 10 which were less than 8% by weight, respectively, were not satisfactory in welding quality.

The shielding gas was then carried out fast gas shielded arc welding using a shielding gas having the composition shown in Table 10 below. The wire diameter of each electrode and the content of the slag forming agent are shown in Table 2 in Example 2.
And the same. The welding conditions for Example 15 were the same as those in Tables 3 to 6, and for Examples 16 to 19, a primer-coated steel sheet was used as a base material. The results of examining the welding quality in these examples are shown in Table 11 below.
Are shown together.

[0050]

[Table 10]

[0051]

[Table 11]

As apparent from Table 11, Example 1
All of Nos. 5 to 19 showed good weldability.

[0053] Torch angle of the first electrode Next, the torch angle of the first electrode while varying, it will be described results of examining the weldability. As shown in Table 12 below, the weldability was examined by variously changing the torch angle of the first electrode. In this case, Table 12 also shows the welding conditions (welding current and arc voltage) of the first electrode and the target position. The other conditions are the same as those in Tables 4 to 6.

With respect to these examples and comparative examples, welding quality was examined. The results are summarized in Table 13 below.

[0055]

[Table 12]

[0056]

[Table 13]

As is apparent from Table 13, Example 2
Comparative Examples 11 and 12 in which the inclination angle of the first electrode with respect to the lower plate was less than 45 °, Comparative Examples 12 and 11 in which the inclination angle was greater than 65 °, while 0 to 22 all exhibited good weldability. In Comparative Example 13 in which the receding angle of the electrode was more than 15 °, the weldability was not satisfactory.

[0058] Torch angle of the second electrode Next, the torch angle of the second electrodes while varying, will be described results of examining the weldability. As shown in Table 14 below, the weldability was examined by variously changing the torch angle of the second electrode. In this case, Table 14 also shows the welding conditions (welding current and arc voltage) of the second electrode and the target position. The other conditions are the same as those in Tables 3, 5, and 6.

With respect to these Examples and Comparative Examples, welding quality was examined. The results are summarized in Table 15 below.

[0060]

[Table 14]

[0061]

[Table 15]

As is apparent from Table 15, Example 2
3 to 25 all showed good welding quality,
Comparative Example 14 in which the inclination angle of the second electrode with respect to the lower plate was less than 45 °, Comparative Example 15 in which the inclination angle was greater than 65 °, and Comparative Example 16 in which the advance angle of the second electrode was greater than 25 °, were all welded. The quality was not satisfactory.

[0063] Torch angle of the third electrode Next, the torch angle of the third electrode while varying, will be described results of examining the weldability. As shown in Table 16 below, the weldability was examined by variously changing the torch angle of the third electrode. In this case, Table 16 also shows the welding conditions (welding current and arc voltage) of the third electrode and the target position. The other conditions are the same as those in Tables 3, 4, and 6.

For these examples and comparative examples, welding quality was examined. The results are summarized in Table 17 below.

[0065]

[Table 16]

[0066]

[Table 17]

As is apparent from Table 17, Example 2
6 to 28 all showed good welding quality,
Comparative Example 17 in which the inclination angle of the third electrode with respect to the lower plate is less than 20 °, Comparative Example 18 in which the inclination angle exceeds 60 °, and Comparative Example 19 in which the advance angle of the third electrode exceeds 30 ° were all welded. The quality was not satisfactory.

Aiming Position of First Electrode Next, the result of examining the weldability by variously changing the aiming position of the first electrode will be described. As shown in Table 18 below, the target position of the first electrode was variously changed, and the weldability was examined. In this case, Table 18 also shows the welding conditions (welding current and arc voltage) of the first electrode and the torch angle. The other conditions are the same as those in Tables 4 to 6.

For these examples and comparative examples, welding quality was examined. The results are summarized in Table 19 below.

[0070]

[Table 18]

[0071]

[Table 19]

As is clear from Table 19, Example 2
Both 9 and 30 showed good welding quality,
In Comparative Example 20 in which the target position of the first electrode exceeded 2 mm with respect to the route, the welding quality was not satisfactory.

Aiming Position of Second Electrode Next, the result of examining the weldability by variously changing the aiming position of the second electrode will be described. As shown in Table 20, the target position of the second electrode was variously changed, and the weldability was examined. In this case, the welding conditions (welding current and arc voltage) of the second electrode and the torch angle are also shown in Table 20. The other conditions are the same as those in Tables 3, 5, and 6.

The welding quality of these examples and comparative examples was examined. The results are summarized in Table 21 below.

[0075]

[Table 20]

[0076]

[Table 21]

As is clear from Table 21, Example 3
While Nos. 1 and 32 showed good welding quality,
In Comparative Example 21 in which the target position of the second electrode was more than 2 mm from the target position of the first electrode, the welding quality was not satisfactory.

Aiming Position of Third Electrode Next, the result of examining the weldability by variously changing the aiming position of the third electrode will be described. As shown in Table 22 below, the target position of the third electrode was variously changed, and the weldability was examined. In this case, the welding conditions (welding current and arc voltage) of the third electrode and the torch angle are also shown in Table 22. The other conditions are the same as those in Tables 3, 4, and 6.

The welding quality of these examples and comparative examples was examined. The results are summarized in Table 23 below.

[0080]

[Table 22]

[0081]

[Table 23]

As is clear from Table 23, Example 3
3 and 34 showed good welding quality,
In Comparative Example 22 in which the target position of the third electrode was less than 1 mm with respect to the route, and in Comparative Example 23 in which the target position exceeded 3 mm, the welding quality was not satisfactory.

[0083] interelectrode distance Next, the inter-electrode distance between the distance between electrodes and the second electrode and the third electrode between the first electrode and the second electrode while varying, will be described results of examining the weldability. As shown in Table 24 below, the weldability was examined by variously changing the distance between the first electrode and the second electrode and the distance between the second electrode and the third electrode. Other conditions are the same as those in Tables 3 to 5.

The welding quality of these examples and comparative examples was examined. The results are summarized in Table 25 below.

[0085]

[Table 24]

[0086]

[Table 25]

As apparent from Table 25, Example 3
5 to 38 showed good welding quality,
Comparative Example 24 in which the distance between the first electrode and the second electrode is less than 15 mm, the distance between the first electrode and the second electrode being 40 m
In Comparative Example 25 exceeding m, and Comparative Example 26 in which the distance between the second electrode and the third electrode was less than 70 mm, the welding quality was not satisfactory.

[0088] Welding current of the first electrode Next, the welding current of the first electrode while varying, will be described results of examining the weldability. As shown in Table 26 below, the weldability was examined by variously changing the welding current of the first electrode. In this case, Table 26 also shows the torch angle and target position of the first electrode. Table 4 shows the other conditions.
To Table 6.

The welding quality of these Examples and Comparative Examples was examined. The results are summarized in Table 27 below.

[0090]

[Table 26]

[0091]

[Table 27]

As is clear from Table 27, Example 3
9 and 40 showed good welding quality,
In Comparative Example 27 in which the welding current was less than 250 A and Comparative Example 28 in which the welding current exceeded 650 A, none of the welding qualities was satisfactory.

[0093] Welding current of the second electrode Next, the welding current of the second electrode while varying, will be described results of examining the weldability. As shown in Table 28 below, the weldability was examined by variously changing the welding current of the second electrode. In this case, Table 28 also shows the torch angle and target position of the second electrode. The other conditions are the same as those in Tables 3, 5, and 6.

The welding quality of these examples and comparative examples was examined. The results are summarized in Table 29 below.

[0095]

[Table 28]

[0096]

[Table 29]

As is clear from Table 29, Example 4
1,42 showed good welding quality,
In Comparative Example 29 in which the welding current was less than 250 A and Comparative Example 30 in which the welding current exceeded 650 A, none of the welding qualities was satisfactory.

[0098] Welding current of the third electrode Next, the welding current of the third electrode while varying, will be described results of examining the weldability. As shown in Table 30 below, the weldability was examined by variously changing the welding current of the third electrode. In this case, Table 30 also shows the torch angle and target position of the third electrode. The other conditions are the same as those in Tables 3, 4, and 6.

The welding quality of these examples and comparative examples was examined. The results are summarized in Table 31 below.

[0100]

[Table 30]

[0101]

[Table 31]

As is clear from Table 31, Example 4
3 and 44 showed good welding quality,
In Comparative Example 31 in which the welding current was less than 250 A and Comparative Example 32 in which the welding current exceeded 650 A, none of the welding qualities was satisfactory.

Welding Speed and Surface State of Base Material Next, the results of examining the weldability by changing the welding speed and the surface state of the base material will be described. As shown in Table 32 below, the welding speed was 2.0 m / min or 2.5 m / min,
The weldability was examined with the surface of the base material as black scale or a primer-coated steel sheet (inorganic zinc primer about 30 μm).
Other conditions are the same as those in Tables 3 to 5.

The welding quality of these examples was examined. The results are shown in Table 33 below.

[0105]

[Table 32]

[0106]

[Table 33]

As is clear from Table 33, Example 4
5 to 48 showed good welding quality.

[0108]

As described above, according to the gas shielded arc welding method according to the present invention, a first molten pool is formed by first and second electrodes using a welding wire having a predetermined diameter. Since the second molten pool is formed by three electrodes and welding is performed, a special large-capacity welding machine is not required, and
Excellent welding workability such as bead appearance / shape and arc stability, and no welding defects such as pits, blowholes and poor fusion.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a T-joint in which weldability of an example of the present invention has been examined.

FIG. 2 is a schematic view showing an arrangement of electrodes in an embodiment of the present invention.

[Explanation of symbols]

 1; standing plate 2; lower plate 5; first electrode 6; second electrode 7; third electrode

Continued on the front page (72) Inventor Toshihiko Nakano 100-1 Urakawachi, Miyamae, Fujisawa-shi, Kanagawa Examiner, Koto Steel Co., Ltd., Fujisawa Works Masato Kato (56) References JP-A-60-15067 (JP, A JP-A-51-48739 (JP, A) JP-A-4-91866 (JP, A) JP-A-57-91879 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 9/16 B23K 9/173

Claims (4)

(57) [Claims] In a gas-shielded arc welding method using at least three flux-cored welding wires having a diameter of 1.4 to 1.6 mm , a distance between a preceding first electrode and a succeeding second electrode is set to 15 or more. To 40 mm, the distance between the second electrode and the subsequent third electrode is 70 mm or more, and the slug of the wires of the first electrode and the second electrode.
The total of the forming agent content is 1 to 6% by mass,
When the slag forming agent content of the wire is 3 to 8% by mass
In both cases, the welding current of each electrode is set to a direct current of 750 A or less,
A gas shield, wherein a first weld pool is formed by the first and second electrodes, and a second weld pool is formed by the third electrode, and welding is performed at a welding speed of 2 m / min or more. Arc welding method. 2. The distance between the first electrode and the second electrode is 25 to 30 mm, and the distance between the second electrode and the third electrode is 100 mm or more.
2. The gas shielded arc welding method according to 1. 3. In the fillet welding, the first electrode comprises:
The inclination angle with respect to the lower plate is 45 to 65 °, the receding angle is 0 to 15 °, and the second electrode has an inclination angle of 45 to 65 ° with respect to the lower plate, an advancing angle of 0 to 25 °, and the third electrode. The electrode has an inclination angle of 20 to 6 with respect to the advancing lower plate.
0 °, advance angle is 0 to 30 °, the wire aiming position of the first electrode is 0 to 2 mm horizontally from the root, and the wire aiming position of the second electrode is the wire aiming position of the first electrode. From 0 to 2 mm in the horizontal direction, the target wire position of the third electrode is 1 to 3 mm in the vertical direction from the root, and the welding current of each electrode is 250 to 650 A. Claim 1
Or the gas shielded arc welding method according to 2. 4. CO ₂ gas or CO ₂ as a shielding gas
Claims 1 to 3, characterized by the use of _2-containing gas
The gas shielded arc welding method according to any one of the above.