KR100600902B1 - Flux-containing wire for multielectrode gas-shielded arc welding - Google Patents

Abstract

The flux-containing wire for multi-electrode gas shielded arc welding of the present invention has a ratio Sf (%) ((cross-sectional area of mild steel shell) / (total cross-sectional area of wire) x 100%) of the overall cross-sectional area to the total cross-sectional area of the wire cross section. 30 to 70%. Vickers hardness H (Hv) of the outer skin satisfies H≤425-3 x Sf. The composition is based on the total weight of the wire, oxides excluding alkali metal oxides: 3.5 to 7.5 mass%, alkali metal compounds: 0.01 to 0.40 mass%, Si: 0.4 to 1.2 mass%, Mn: 1.5 to 4.0 mass%, Al: 0.2 To 0.6 mass%. The alkali metal compound is one or two or more selected from the group consisting of K ₂ O, Na ₂ O and Li ₂ O. This wire has excellent welding workability, bead shape and appearance, and primer resistance even at high welding speeds of 150 cm / min or more, such as excessive gaps in welding joints, voltage fluctuations, excessive fluctuations in primer film thickness, and the like. There is very little repair welding even if disturbance occurs

Description

Flux-containing wire for multi-electrode gas shield arc welding {FLUX-CONTAINING WIRE FOR MULTIELECTRODE GAS-SHIELDED ARC WELDING}

BRIEF DESCRIPTION OF THE DRAWINGS It is a side view which shows the outline of a torch horizontal angle and a wire target position in the Example of this invention.

Fig. 2 is a plan view showing an outline of the torch forward and backward angles and the poles in the embodiment of the present invention.

3 is a schematic diagram showing a shift interval in an embodiment of the present invention.

Fig. 4 is a schematic view showing the flow of water in the present invention, the top view is a side view, and the bottom view is a plan view.

5A and 5B are views showing a step of producing the flux-containing wire of the present invention.

The present invention is suitable for horizontal and downward fillet welding of steel sheets coated with primary rust-preventive paints such as shop primers, and in particular, two-electrodes for forming one molten paper with two electrodes. The present invention relates to a flux-containing wire for multi-electrode gas shield arc welding, which enables welding construction excellent in welding workability, bead shape and appearance, and primer resistance even in high-speed welding with a welding speed of 150 cm / min or more.

In the field of shipbuilding or bridges, welding is often performed with a primary antirust coating such as shop primer due to the high ratio of fillet welding length to the total welding length and the rationalization of the work process. For this reason, the welding wire and the construction method which are excellent in the high efficiency and high speed, and excellent in the primer resistance in horizontal fillet welding for the purpose of improving the productivity of a structure are desired.

Flux-containing wires for metal-based and titania-based gas shielded arc welding have been widely applied in terms of high efficiency and good welding workability. However, in the case of single electrode welding, if the welding speed is increased, problems such as (a) deterioration of the primer resistance, (b) easily undercut, and (c) convex beads and bead unevenness are likely to occur. As a result, the welding speed is limited to about 70 cm / minute.

Accordingly, a construction method having excellent high-speed weldability, such as a multi-electrode gas shield arc welding method and a flux-containing wire for multi-electrode gas shield welding, and a welding wire suitable for welding in a multi-electrode have been proposed (for example, Japanese Patent Laid-Open No. 1994-234075). , Japanese Patent Laid-Open No. 2000-71096, Japanese Patent Laid-Open No. 1983-84696, Japanese Patent Laid-Open No. 1987-84892, and Japanese Patent Laid-Open No. 1997-38791).

Japanese Patent Application Laid-Open No. 1994-234075 discloses a flux-containing wire containing one or two or more kinds of an oxide and an alkali metal compound and a predetermined amount of Mg, Si, and Mn in the preceding electrode and the following electrode, Disclosed is a two-electrode tandem gas shielded arc horizontal fillet welding method for welding a gap between a trailing pole of 15 to 50 mm. By this prior art, it is believed that good welding workability and primer resistance can be obtained in high-speed horizontal fillet welding with a welding speed of 100 cm / min or more.

Further, Japanese Patent Laid-Open No. 2000-71096 discloses two electrodes containing a predetermined amount of C, Si, Mn, Mg, Al, TiO ₂ , ZrO ₂ , and MgO, and in particular, forming one molten paper with two electrodes. Flux-containing wires for horizontal fillet gas shield welding suitable for use in a one-pull method are disclosed. By this prior art, it is believed that good welding workability and excellent continuous weldability can be obtained in high-speed horizontal fillet welding with a welding speed of 150 cm / min or more.

However, in the prior art, when the welding speed exceeds 150 cm / min, (a) the primer resistance is deteriorated, (b) undercut is likely to occur, and (c) convex beads and bead unevenness are easily generated. There is a problem. In the actual welding site, various disturbances (excessive gaps in welding joints, voltage fluctuations, excessive variation and fluctuations in primer film thickness, etc.) occur, and when affected by these disturbances, (a) a molten paper formed between two electrodes Problems such as (water flow) become unstable, bead nonuniformity and undercut generation number increase, and (b) pit generation number increase. The problem caused by the disturbance becomes prominent in high speed welding of 150 cm / min or more, leading to a decrease in productivity due to an increase in repair welding.

Japanese Patent Application Laid-Open No. 1983-84696 discloses a welding flux-containing wire having a skin section having a ratio of 0.55 to 0.85 with respect to the entire cross-sectional area of the wire, and having no opening in the skin part.

Japanese Unexamined Patent Publication No. 1987-84892 includes a predetermined amount of iron and carbon in the wire, and sets the ratio (the sheath metal cross-sectional area / total wire cross-sectional area) to 0.06 to 0.80, and the deviation in the wire length direction of this ratio. Iron-based flux-containing wires are limited to 0.05 or less.

Japanese Patent Laid-Open Publication No. 1987-38791 discloses a welding flux in which the ratio of the skin part area to the wire cross-sectional area is 50 to 95%, the Vickers hardness of the skin is 300 Hv or less, and the area ratio and the skin hardness satisfy a predetermined relational expression. A containing wire is disclosed.

However, the above-mentioned prior art improves the wire feeding property or reduces the amount of sputter generation, and in the single electrode or multi-electrode high-speed horizontal fillet welding with a welding speed of 150 cm / min or more, pits and gas grooves, bead unevenness, convex beads, And there is a problem that a lot of defects such as undercut occurs.

The present invention has been made in view of this problem, and even in high-speed welding with a welding speed of 150 cm / min or more, it has excellent welding workability, bead shape and appearance, and primer resistance. It is an object to provide a flux-containing wire for low multi-electrode gas shield arc welding.

The flux-containing wire for multi-electrode gas shield arc welding according to the present invention is a flux-containing wire formed by filling a flux in a mild steel shell, wherein the ratio Sf (%) of the shell cross-sectional area to the total cross-sectional area in the cross section of the wire ((mild steel) The cross-sectional area of the outer skin) / (wire total cross-sectional area) × 100%) is 30 to 70%, and the Vickers hardness (H) (Hv) of the outer skin is within a range that satisfies H ≦ 425-3 × Sf. do.

In the flux-containing wire for multi-electrode gas shield arc welding, the composition is based on the total mass of the wire,

Oxides other than alkali metal oxides: 3.5 to 7.5 mass%

Alkali metal compound: 0.01 to 0.40 mass%

Si: 0.4-1.2 mass%

Mn: 1.5 to 4.0 mass%

Al: 0.2-0.6 mass%

Containing,

To the alkali metal compound is K ₂ O, more than one or two selected from the group consisting of Na ₂ O and Li ₂ O are preferred.

More preferably the composition is based on the total mass of the wire

Oxides other than alkali metal oxides: 4.6 to 6.7% by mass

Alkali metal compound: 0.05-0.30 mass%

Si: 0.6 to 1.2 mass%

Mn: 2.0 to 3.5 mass%

Al: 0.3-0.5 mass%

Containing,

To the alkali metal compound is K ₂ O, more than one or two selected from the group consisting of Na ₂ O and Li ₂ O are preferred.

As described above, according to the present invention, by setting the outer shell occupancy ratio (Sf) and the wire composition of the flux-containing wire to an appropriate value, the melt flow stability is good, and excellent bead appearance, shape, and porosity resistance can be obtained.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to an accompanying drawing. BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram seen from the welding direction which shows the multi-electrode gas shield arc welding method in which the wire of this invention is used, and FIG. 2 is the schematic diagram seen from the direction perpendicular | vertical to a welding direction. 3 and 4 are diagrams illustrating the operation. On the horizontal lower plate 1, a vertical upper plate 2 is arranged perpendicularly to the lower plate 1, and the lower plate 1 is formed by two electrodes of the L pole 3 and the T pole 4; And the corner portions of the upper plate 2 are horizontally fillet welded. This horizontal fillet welding is performed on both surfaces of the top plate 2. The L pole 3 disposed in the front of the welding direction is inclined with a retreat angle such that the tip of the wire supplied from the torch is rearward in the welding direction, and the T pole 4 disposed behind the welding direction is supplied from the torch. The tip of the wire is inclined with a forward angle so as to be forward in the welding direction. The target position of the L pole 3 is located closer to the upper plate 2 than the target position of the T pole 4, and the L pole 3 and the T pole 4 each have a cross section perpendicular to the welding direction. Inclined at torch angle. In addition, the space | interval of the welding direction of the target position of the L pole 3 and the T pole 4 is an interval between poles.

In this two-electrode gas shielded arc welding method, while shielding the gas at the ends of the L-pole 3 and the T-pole 4, the welding wire is sent out from the torch, and the welding wire is fed to the welding wire through the torch for welding. Arcs 7a and 7b are generated between the wire and the welded material. Then, the corner portions of the upper plate 2 and the lower plate 1 are fillet welded while maintaining the retreat angle and the advancing angle, the torch angle, and the inter-pole distance of the L pole 3 and the T pole 4 constant. Thereby, the to-be-welded material melts by arc heat, and the molten paper 5 is formed. In this case, the molten pool 5 swells between the arc 7a of the preceding L-pole 3 and the arc 7b of the trailing T-pole 4 to form a melt 6. In addition, although the rust-proof paint is apply | coated to the upper board 2, this rust-proof paint is decomposed | disassembled and burned by arc heat. The area | region 8 is an area | region in which this rust preventive paint was decomposed and burned. In addition, the number of electrodes is not limited to two, three or more plurality may be provided.

The present invention is a flux containing wire used in such a multi-electrode gas shielded arc welding method. This flux-containing wire is made by filling flux into a mild steel shell. Then, the ratio of the skin cross-sectional area to the total cross-sectional area in the wire cross section (hereinafter referred to as skin share) Sf (%) is 30 to 70%. However, Sf is defined as ((cross-sectional area of the mild steel outer shell portion) / (wire overall cross-sectional area)) × 100%. In addition, the outer shell of the Vickers hardness H (Hv) satisfies H≤425-3 x Sf.

The composition of the flux-containing wire for multi-electrode gas shielded arc welding is, for example, 3.5 to 7.5 mass% of oxides other than alkali metal oxides, alkali metal compound: 0.01 to 0.40 mass%, and Si: 0.4-1.2 mass%, Mn: 1.5-4.0 mass%, Al: 0.2-0.6 mass%. However, the alkali metal compound is one or two or more selected from the group consisting of K ₂ O, Na ₂ O and Li ₂ O. Also preferably, the composition is based on the total weight of the wire, except for alkali metal oxides: 4.6 to 6.7 mass%, alkali metal compounds: 0.05 to 0.30 mass%, Si: 0.6 to 1.2 mass%, Mn: 2.0 to 3.5 Mass%, Al: 0.3-0.5 mass%.

Next, the reason for numerical limitation in the structural requirements of this invention is demonstrated.

Skin share (ratio of skin cross section to total cross section in wire cross section) (Sf) (%): 30 to 70%

In the two-electrode one-pull method, it is most important to stabilize the melts in order to ensure good welding workability, appearance and shape of beads, and porosity resistance. Conventionally, the stabilization of the hot water has been made by adjusting the forward and backward angle of the electrode, the distance between the poles, the target position of the electrode, the position of the base material, the length of the wire protrusion, and the like.

In the present invention, a study has been made by investigating and reviewing a factor that has not been studied in the past, such as the coat share. In other words, in order to stably form the melt, the viscosity of the pool and the welding speed are also important factors, but the balance between the arc generation direction and the arc force (pressure caused by plasma airflow) of the two electrodes is also appropriate for the stable formation of the melt. It is indispensable. When the arc loses the balance between its directionality and the arc force due to self-tension, the melt flow becomes unstable and no healthy weld beads can be formed. In this construction method, welding is performed by flowing an ultra-high current of about 500 amps through a wire having a diameter of 1.2 to 1.6 mm. Thus, the arc force is very large as compared with the general single electrode wire construction method, and the arc force fluctuates even slightly due to disturbance. If this occurs, the balance of the melts will be broken, and stable beads cannot be obtained.

In general, if the skin occupancy is small, the welding current density per skin unit area becomes large at the same current, and the arc force increases in proportion to the current density. On the other hand, when the skin occupancy increases, the skin cross-sectional area increases, and at the same welding current, the welding current density per skin unit area decreases, and the arc force decreases.

However, according to various studies by the present inventors, on the contrary, the smaller the coat share, the better the stable formation of the melts. Although the skin occupancy ratio (Sf) of the conventional mild steel shell is generally over 70%, in the two-electrode one-pull construction method, as in the present invention, by setting this Sf to less than 70%, the most important characteristics Stability was obtained, and the undercut and the bead width nonuniformity were easily eliminated. On the other hand, when the skin occupancy ratio (Sf) of the mild steel shell is less than 30%, the cross-sectional area occupancy ratio (100-Sf) of the flux portion becomes excessive, so that the fluctuation of the flux filling amount is likely to occur, resulting in arc fluctuations or slag coatability. Deteriorate. Therefore, the skin occupancy ratio Sf is 30 to 70%.

Vickers hardness (H) of the shell: H≤425-3 × Sf

When the Vickers hardness (H) of the outer skin exceeds 425-3 x Sf, the wire strength becomes excessive, so that the supply resistance increases, supply instability occurs, or the pull-out resistance during the drawing is large, and disconnection and die roughness It is easy to generate a wire surface scratch. Therefore, the Vickers hardness H of the outer skin is in the range of H ≦ 425-3 × Sf.

The value of H is largely determined by the value of the skin composition, the original wire diameter of the wire, the final wire diameter, and the value of Sf. Therefore, it is preferable to adjust these values appropriately so that the value of H satisfies the above condition.

As mentioned above, favorable melt flow stability can be obtained by making the skin occupancy ratio Sf of a mild steel outer shell into a predetermined ratio. Such a welding wire has a thinner outer skin and a lower hardness H than conventional welding wires. When the welding wire of the present invention is produced by a conventional process, sufficient productivity and production quality cannot be obtained. For this reason, the production method should be optimized in producing the welding wire of the present invention.

Generally, the flux-containing wire for welding is formed by forming a rough steel in a U shape, then supplying the flux into the U shape, and forming a rough steel from a U shape to a tubular shape, and then drawing it to a predetermined wire diameter by a drawing process. Fresh processing. And it is mainstream to perform a substantial drawing process part with high work rate with a hole die. When the wire is produced by such a conventional production method, (a) the shearing force at the time of drawing is higher than the wire strength, the single wire is bundled, and (b) the surface of the wire is scratched due to the roughness of the hole die, (c) ) There is a problem such as a change in the amount of flux charge.

For this reason, the present inventors (1) apply roller dice with a small pull-out force at the time of drawing compared with a hole die, (2) optimization of reduction reduction ratio in a hole die, (3) optimization of a shape roll shape, (4) As a result of various optimizations of flux charging conditions, the above problems have been solved.

Hereinafter, the manufacturing method of the flux containing wire of this invention is demonstrated concretely with reference to FIG. It is a figure which shows the manufacturing process of a flux containing wire, and FIG. 5B is a cross-sectional view which shows the cross-sectional shape of the hoop in each shaping process. First, the rough oil 100 supplied to the coil is degreased and cleaned from the rough oil surface by the rough degreasing step 102, and roughly processed, such as vegetable oil, mineral oil and synthetic oil, in the lubricant applying step 103a. Lubricant necessary for is applied. Thereafter, in the forming step, the roughly 100 is sequentially molded from the belt to the U-shape 100a and the tubular 100b by the forming rollers 104a and 104b. In the state where the rough steel 100 is formed into the U-shaped steel 100a, the flux 106 is supplied onto the U-shaped steel 100a by the flux supply device 105. Reference numeral 112 is a guide roller. In the present invention, in order to suppress the variation in the flux ratio in the longitudinal direction of the wire (that is, the share of the outer cross-sectional area), the shape of the forming roller 104a and the pass schedule are optimized, and the variation in the flux supply speed is suppressed as much as possible. To devise.

The wire 100c formed into a tubular shape and supplied with flux is drawn and processed by roller dice 201, 206, 401, and 405 in the molding drawing and finishing drawing process via a lubricant coating step 103b. 501 is finished to a predetermined wire diameter. Reference numeral 111 is a capstan. Further, the wire 100d wired by the roller dice 201 and 206 is once coiled 116, and then wired again by the roller dice 401 and 405. In addition, the shim 114 has a pad type shim 114a and a wrap type shim 114b.

In general, in order to secure the roundness of the wire cross-sectional shape, hole dies have been conventionally used in forming drawing and finishing drawing processes. However, the hole die has a good roundness in the cross-sectional shape of the wire. However, since the pullout resistance at the time of wire drawing is large, there is a problem in that the wire cross-section is small and wire breakage tends to occur with low strength. For this reason, it is assumed that roller dies 201, 206, 401, and 405 having a smaller pull resistance than hole dies are used, and only the last die is used as hole dies 501, so that the outer cross-sectional area is larger than that of the conventional wire. The present invention is designed to enable the processing of a wire having a low occupancy rate and a low hardness (H), and to secure the roundness of the wire cross-sectional shape. After the fresh wire is removed by the lubricant removing device 115, the fresh wire 107 is provided with a wire feeding lubricant 113 by the lubricant applying devices 108 and 109. Thereafter, the wire 107 is wound around the wire winding bobbin 110.

In addition, sufficient high porosity resistance and bead appearance and shape cannot be secured in high-speed horizontal fillet welding exceeding 150 cm / min only by setting the sheath occupancy ratio (Sf) of the mild steel shell to a predetermined ratio. Content of the component in relation to mass).

Oxides other than alkali metal oxides: 3.5 to 7.5 mass%

The oxide becomes a slag and uniformly covers the surface of the bead to adjust the appearance and shape of the bead, and also affects porosity resistance. If the oxide is less than 3.5% by mass, the slag coating on the surface of the bead becomes uneven, resulting in convex beads as the bead appearance deteriorates. On the other hand, when the oxide exceeds 7.5% by mass, the release of gas generated by the combustion of the shop primer or the like is suppressed in the slag layer, whereby the porosity resistance deteriorates. Bead appearance, shape and porosity were good when the amount of oxide was 3.5 to 7.5% by mass, and the best was obtained when 4.6 to 6.7% by mass. Therefore, the range of oxide is 3.5 to 7.5 mass%, and more preferable range is 4.6 to 6.7 mass%. In addition, rutile, illuminite, zircon sand, alumina, magnesia, silica sand, etc. are mentioned as a raw material of an oxide, These are added to an inclusion flux as a powder.

Alkali metal compound: 0.01 to 0.40 mass%

Alkali metal has a function of stabilizing the arc. If the alkali metal compound is less than 0.01% by mass, the arc becomes unstable. On the other hand, when the alkali metal compound exceeds 0.40% by mass, the injection of the arc becomes so strong that the melt stability deteriorates. Arc stability and melt stability were good when the alkali metal compound was 0.01 to 0.40 mass%, and became the best at 0.05 to 0.30 mass%. Therefore, the range of the alkali metal compound amount is 0.01 to 0.40 mass%, and more preferably, the range is 0.05 to 0.30 mass%. In addition, the alkali metal compound is one or two or more selected from the group consisting of K ₂ O, Na ₂ O, and Li ₂ O, and examples of the raw material include kali feldspar, soda feldspar, and kali glass. These are added to the inclusion flux as a powder. In addition, the alkali metal compound content in the present invention is a value in terms of value of component analysis of these raw material powders of the alkali metal oxides such as K ₂ O, Na ₂ O and Li ₂ O.

Si: 0.4-1.2 mass%

Si is used as a deoxidizer and has the function of adjusting the bead shape and appearance, and the mechanical performance of the weld metal. When Si is less than 0.4 mass%, the beads become convex, the bead shape deteriorates, and pore generation occurs due to lack of deoxidation. On the other hand, when Si exceeds 1.2 mass%, the intensity | strength of a weld metal will become excessive and toughness will fall. In addition, when the amount of Si was in the range of 0.6 to 1.2% by mass, better porosity resistance and bead shape could be obtained. Therefore, the range of Si amount is 0.4 to 1.2 mass%, more preferably 0.6 to 1.2 mass%. In addition, as a raw material of Si, Si in a mild steel outer shell is included in addition to metal powders, such as Fe-Si and Fe-Si-Mn, which were added to the inclusion flux.

Mn: 1.5 to 4.0 mass%

Mn has the same effect as Si. When Mn is less than 1.5 mass%, pores due to lack of deoxidation are generated and the bead shape deteriorates. On the other hand, when Mn content exceeds 4.0 mass%, the intensity | strength of a weld metal will become excessive. In addition, in the range of 2.0 to 3.5 mass% of Mn, better porosity resistance and bead shape can be obtained. Therefore, the range of Mn amount is 1.5 to 4.0 mass%, More preferably, it is 2.0 to 3.5 mass%. In addition, as a raw material of Mn, in addition to metal powders, such as Fe-Si and Fe-Si-Mn, added to the inclusion flux, Mn in the soft steel outer shell is also included.

Al: 0.2-0.6 mass%

Al acts as a deoxidizer, reduces the amount of oxygen in the deposited metal and secures strength, and affects the fluidity and slag foreskin of the molten metal. When Al was less than 0.2 mass%, the molten metal was disturbed, and the amount of sputter generation and the irregularity of beads occurred.

Moreover, when Al exceeds 0.6 mass%, the slag fluidity is bad, the foreskin becomes uneven, slag peelability, bead appearance and bead shape deteriorate. In addition, when the Al content was 0.3 to 0.5% by mass, the peelability of the slag, the appearance of beads, and the shape of the beads were better. Therefore, the range of Al amount is 0.2-0.6 mass%, and a more preferable range is 0.3-0.5 mass%.

(Example)

Hereinafter, the Example of this invention is shown next. A flux-containing wire having a wire diameter of 1.6 mm was produced using a mild steel shell having a composition shown in Table 1 below, and using a mild steel shell share, skin hardness, and a flux component shown in Table 2 below. In addition, the composition of the soft steel outer sheath shown in following Table 1 is an example to the last, and if a component of the whole flux containing wire is in the range of this invention, a general soft steel outer sheath can be used. In addition, the wire diameter shown in following Table 2 is also an example to the last, and if the arc injection force which can obtain appropriate melt flow stability is obtained, it is also possible to change a wire diameter to 2.0 mm, 1.4 mm, etc. In addition, in following Table 2, oxide is a total amount of the oxide flux raw material except an alkali metal oxide. In addition, alkali metal compounds is the total amount of flux material in terms of K ₂ O, Na ₂ O and Li ₂ O. In addition, Si, Mn, and Al have shown the value which converted each component in the mild steel shell in conversion value of each component of the metal powder in a flux.

Next, the welding test was done on the welding conditions shown in following Table 3 using the wire produced on the conditions shown in the said Table 1 and Table 2. The welding test results are shown in Table 4 below. However, in Table 4, (circle) is very good, (circle) is good, (triangle | delta) is slightly bad, and x is bad.

As is apparent from Table 4, Examples 1 to 10 of the present invention had good melt stability, and were able to obtain excellent bead shape, appearance, and porosity resistance. On the other hand, Comparative Examples 11 to 20 were out of the range of the present invention, and thus had problems shown below. In Comparative Example 11, since the skin occupancy ratio Sf was smaller than the range of the present invention, arc variation occurred. In Comparative Example 12, since the shell occupancy ratio Sf was larger than the range of the present invention, the melted water was not stabilized, and non-uniformity and undercut occurred. In Comparative Example 13, since Vickers hardness (H) of the outer skin was outside the range of the present invention, the supplyability was poor and arc breaking occurred. In Comparative Example 14, since Vickers hardness (H) of the outer skin was outside the range of the present invention, the supplyability was poor and arc breaking occurred. Comparative Example 15 became a convex bead because the amount of the oxide was less than the range of the present invention, and the bead shape deteriorated. In Comparative Example 16, since the amount of the oxide was larger than the range of the present invention, the pits and the gas grooves were bundled, and the porosity resistance was deteriorated. In Comparative Example 17, since the amount of the alkali metal compound was smaller than the range of the present invention, the arc became unstable and the melts were not stabilized. Further, in Comparative Example 18, since the amount of the alkali metal compound was greater than the range of the present invention, the injection of the arc became stronger, the melted water was not stabilized, and the appearance and shape of the beads deteriorated. In Comparative Example 19, since the amount of Si and the amount of Mn were smaller than the range of the present invention, not only a lot of pits occurred due to lack of deoxidation, but also the bead shape became convex. In Comparative Example 20, since the amount of Si and the amount of Mn were larger than those of the range of the present invention, the injection of the arc was so strong that the melt flow became unstable, resulting in uneven bead and undercut. In Comparative Example 21, since the amount of Al was smaller than the range of the present invention, the molten metal was disturbed largely, and defects such as bead nonuniformity and undercut occurred frequently. In Comparative Example 22, since the amount of Al was larger than the range of the present invention, the coating of slag was uneven, and the slag peelability and the bead tube were deteriorated. In Comparative Examples 23 and 24, since the hardness H was out of the relationship of H? (425-3 x Sf), the feeding was unstable and the arc was disturbed.

The flux-containing wire for multi-electrode gas shielded arc welding produced in accordance with the present invention has excellent welding workability, bead shape and appearance, and primer resistance even at high speed welding with a welding speed of 150 cm / min or more, such as an excessive weld seam. Repair welding is very small even when disturbances such as gaps, voltage fluctuations, and excessive and fluctuations in primer film thickness occur.

Claims (3)

Flux-containing wire formed by filling a flux in a mild steel shell, wherein the ratio (Sf) (%) of the shell cross-sectional area to the total cross-sectional area in the cross section of the wire ((cross-sectional area of the mild steel shell) / (wire cross-sectional area) x 100 %) Is 30 to 70%, and the Vickers hardness (H) (Hv) of the outer skin is in a range that satisfies H≤425-3 x Sf. The method of claim 1, Relative to the total mass of the wire, Oxides other than alkali metal oxides: 3.5 to 7.5 mass% Alkali metal compound: 0.01 to 0.40 mass% Si: 0.4-1.2 mass% Mn: 1.5 to 4.0 mass% Al: 0.2-0.6 mass%, Flux-containing wire for multi-electrode gas shield arc welding, characterized in that the alkali metal compound is one or two or more selected from the group consisting of K ₂ O, Na ₂ O and Li ₂ O. The method of claim 2, Relative to the total mass of the wire, Oxides other than alkali metal oxides: 4.6 to 6.7% by mass Alkali metal compound: 0.05-0.30 mass% Si: 0.6 to 1.2 mass% Mn: 2.0 to 3.5 mass% Al: 0.3 to 0.5% by mass, Flux-containing wire for multi-electrode gas shield arc welding, characterized in that the alkali metal compound is one or two or more selected from the group consisting of K ₂ O, Na ₂ O and Li ₂ O.

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