JP2001334391A - Flux-filled wire for gas-shielded arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flux-filled wire for gas-shielded arc welding provided with various capacities of the high deposition capacity, productivity, low slag yield and low fume yield of solid wires and the stable welding operability or the like of flux-filled wires. SOLUTION: This flux-filled wire for gas-shielded arc welding is concretely the one obtained by filling flux into an outer surface made of steel, the filling flux contains, by the total wire mass%, 0.3 to 1.5% Si, 0.8 to 3.0% Mn and, as an arc stabilizer, Na2 by 0.05 to 0.6% as a value expressed in terms of Na2O, and the filling ratio of the flux is 3 to 8%. Alternatively, the filling flux is, as an arc stabilizer, further incorporated with a TiO2 source as a value expressed in terms of TiO2, and moreover, the filling flux contains iron. Further, as the flux-filled wire, a wire free from seams in the outer surface and having plating or free from plating or the one having seams is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux cored wire for gas shielded arc welding used for welding various steel structures in buildings, bridges, shipbuilding, etc., and relates to welding workability such as extremely good arc condition and little spatter. And a flux cored wire for gas shielded arc welding.

[0002]

2. Description of the Related Art Conventionally, gas shielded arc welding wires include solid wires and flux-cored wires.

Various types of solid wires for arc welding have been developed with their components adjusted according to the purpose of use.
IS Z3312, and other standardized and commonly used. In addition, flux-cored wires for arc welding are generally called slag-based wires, and many flux-cored wires mainly filled with slag components and metal-based wires that are mainly called metal components have been developed. ,
It is standardized in JIS Z3313 and others.

[0004] However, when a solid wire requires an arc stabilizer to further improve welding workability, the solid wire cannot contain the arc stabilizer. Further, with respect to the flux-cored wire, a large number of wires having good weldability and good weldability have been put into practical use by improving the filling flux. Most of these wires have a flux filling rate of 10% to 20%, and technical disclosures with a filling rate of 5% are scattered. However, in the flux component system, there are problems such as an excessive amount of welding slag and an excessive amount of fume generation. In fact, such a low filling rate wire is not supplied practically. For flux cored wires,
In reality, a wire mainly composed of metal powder having a welding workability close to that of a solid wire has problems in arc stability and productivity.

As described above, these wires have advantages and disadvantages, and there is a demand for a small-diameter wire for gas shielded arc welding that incorporates the advantages of both a solid wire and a flux-cored wire.

Japanese Patent Publication No. Sho 51-1695 discloses an example of a flux-filled wire having a low flux filling rate.
A wire cross-sectional area ratio of 5 to 25% is disclosed. Although an example in which the wire cross-sectional area ratio of the flux of the present invention is as low as 5% is disclosed, the filling flux is made of Ti, Al, Mg or the like containing graphite as an essential component as an arc stabilizer, and its compounding ratio is 2 to 2. 10%, and 20 ~ more deoxidizer
A wire that contains 90% and is filled with a flux substantially free of metal oxides. Such an arc stabilizer containing graphite includes a factor of arc instability due to a CO reaction between the graphite and oxygen in the wire or oxygen attached to the wire surface, and the arc becomes coarse, which deteriorates welding workability and causes spattering. Increase the amount generated.
Further, the yield of C in the weld metal becomes a problem, and it is not easy to adjust the weld metal performance.

In Japanese Patent Application Laid-Open No. 6-218577, an iron powder having a flux filling rate of 5 to 30%, a limited content of Mn and S and a content of Mn / S ratio of 40 to 60 is used.
%, A deoxidizer composed of iron alloy powder of Si, Mn, and Ti
A flux-cored wire filled with a flux containing 〜60% is disclosed. This is a wire belonging to a metal-based flux-cored wire. In a wire with a filling rate of 5% or 10%, a sufficiently stable arc cannot be obtained with a filling flux composed of this metal powder, and the wire is excellent as a flux-cored wire. Welding workability and good welding results cannot be obtained.

Further, Japanese Unexamined Patent Publication (Kokai) No. 3-180298 discloses that a structure coated with a primer, which is a primary rust preventive paint for a steel sheet, is made of TiO ₂ based Na ₂ This wire contains O and further requires metal fluoride and moisture. This is a flux-cored wire containing a low content of Na ₂ O and TiO ₂ in terms of wire mass%, but it requires metal fluoride and moisture, and it is not easy to adjust the moisture and gas release. The fluidity of the slag is high, and there are problems with bead forming properties and properties of the weld metal.

[0009]

SUMMARY OF THE INVENTION A flux for a gas-shielded arc welding flux cored wire having high welding properties of a solid wire, low slag generation, and various properties such as stable welding workability of the flux cored wire. It is to provide a cored wire.

[0010]

In view of the above-mentioned problems in the prior art, the present inventor has proposed that the filling flux of a low-filling-rate flux-cored wire be replaced with a deoxidizing material made of Si and Mn.
a ₂ O-containing arc stabilizer, and T
By adding iO ₂ , the separation of the droplets during welding is promoted, the droplets are refined and the number of transitions is increased, and arc stabilization is solved, thereby completing the present invention.

That is, the present invention relates to a flux-cored wire for gas shielded arc welding, and more particularly to a wire in which a steel sheath is filled with a flux, and Si:
0.3 to 1.8% (total wire mass%, the same applies hereinafter), M
n: 0.8 to 4.0% and Na ₂ O as an arc stabilizer
The source contains 0.05 to 0.6% in terms of Na ₂ O, and the flux filling rate is 3 to 8% by mass.

[0012] As an arc stabilizer, in the filling flux
Na_TwoTiO in addition to O_TwoTiO source _Two2.0% in converted value
Flux cored wire for gas shielded arc welding including:
It is unpleasant.

Further, the filling flux is a flux-cored wire for gas shielded arc welding containing iron powder.

Further, there is provided the above-mentioned flux-cored wire for gas shielded arc welding, which has no seam or has a seam in a steel sheath.

[0015] The above-mentioned steel sheath surface has the above-mentioned flux-cored wire for gas shielded arc welding, which has copper plating or is not plated.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has reported that S
An arc stabilizer containing Na ₂ O is contained in a deoxidizing material composed of i and Mn, and TiO ₂ is added as necessary to promote the detachment of the droplet at the time of welding, thereby making the droplet finer and smaller. Reducing arc stabilization by increasing the number of transitions, and reducing the flux filling rate to 3 to 8% for problems such as low welding effect, which is a disadvantage of flux cored wires, and large slag generation. The present invention has been made based on the finding that this is an extremely effective means as a flux-cored wire for arc welding, which is a completely new technique.

The reasons for limiting the components of the flux-cored wire of the present invention will be described below.

Regarding Si: 0.3 to 1.8%, Si is used as a deoxidizing agent and has an effect of reducing the amount of oxygen in the weld metal. However, if it is less than 0.3%, the deoxidizing power is insufficient and blowholes are generated in the weld metal, and if it exceeds 1.8%, the droplet becomes large, the effect of reducing spatter is lost, and furthermore, the amount of The yield of the Si component becomes excessive, the crystal grains become coarse, and the toughness deteriorates. Mn: 0.
For 8 to 4.0%, Mn promotes the deoxidation of the weld metal, enhances the flowability of the molten metal, and improves the weld bead shape. In addition, the yield on the weld metal has the effect of adjusting the performance of the weld metal and increasing its strength. To obtain these effects, it is necessary to add 0.8% or more, but if it exceeds 4.0%, the droplets become large, the spatter reduction effect is lost, and the yield to the weld metal becomes excessive, resulting in excessive welding. The strength of the metal is increased, and cracks are likely to occur.

The content of Si and Mn in the filling flux is metal Si, metal Mn or Fe-Si, Fe-Si-Mn,
It is a converted value of Si and Mn of an iron alloy such as Fe-Mn.

The addition amounts of Si and Mn in the total wire mass% are as described above. However, the addition of Si and Mn has the same effect regardless of either the outer shell or the filling flux or both. The deoxidizing power during welding and the yield to the weld metal are not much different. However, when both Si and Mn are added in large amounts from the outer shell, the electrical resistivity of the outer shell increases in proportion to the amount, and the wire feeding speed during welding is
It is larger than when added from the filling flux. The case where Si and Mn are contained in the steel sheath is as follows.

The content of Si is preferably 1.2% or less. The reason is that the amount of Si added to the outer shell is 1.2 to the outer shell weight.
%, The hardness is high, the work hardens easily, the workability is deteriorated, the molding becomes difficult, and the yield is reduced, for example, the wire is easily broken during the wire drawing. Therefore, it is to ensure productivity.

Mn is preferably 2.5% or less. The reason is that the amount of Mn added to the outer coat is 2.5 to the outer coat weight.
%, The hardness is high, the work hardens easily, the workability is deteriorated, the molding becomes difficult, and the yield is lowered such that the wire is easily broken at the time of drawing. Therefore, the upper limit of Mn is for securing productivity.

When both Si and Mn are contained, the content is preferably 3% or less. If the total amount of Si and Mn added to the outer skin exceeds 3.0% based on the weight of the outer skin, hardness is high and work hardening is easy, workability is deteriorated, molding is difficult, and wire drawing is performed. At times, the yield is remarkably reduced, for example, disconnection is likely to occur. Therefore, to secure the productivity,
The total amount of i and Mn is desirably 3.0% or less.

Na ₂ O-converted value as arc stabilizer:
For the addition of 0.05 to 0.6%, Na ₂ O is less arc length variations during welding, the increase in droplet transfer times, i.e. having an effect of promoting grain refining droplet. But 0.0
If it is less than 5%, no effect can be obtained, and if it exceeds 0.6%, the number of times of droplet transfer tends to decrease and the arc length tends to increase, and as a result, the amount of spatter generated increases. Examples of the Na ₂ O source include sodium carbonate and soda glass. However, Na
₂ O—TiO ₂ and Na ₂ O—SiO ₂ —TiO ₂ compounds are not included in the Na ₂ O source.

TiO_Two: About 2.0% or less
TiO_TwoIs the arc in the low-fill flux cored wire
Generates an arc at the tip of the droplet, acting as a stabilizer
By enlarging the area to promote droplet transfer
It has the effect of promoting the electromagnetic pinch effect of orientation. Na
_TwoO to TiO_TwoIncreases the viscosity of the slag
In addition, the covering of the weld metal becomes uniform, and the peelability is improved.
However, if it exceeds 2.0%, the downward electromagnetic pinch effect
It becomes excessive and makes droplet transfer unstable. Also, to weld metal
Yield of reduced Ti content becomes excessive and the performance of weld metal
Affect. TiO _TwoRutile, titanium slag,
Illuminite and the like. However, Na_TwoO-TiO_Twosystem,
Na_TwoO-SiO_Two-TiO_TwoThe compound of the system is TiO_TwoIncluded in the source
No.

The iron powder contained in the filling flux is added for the purpose of increasing the welding speed and / or adjusting the filling rate.
The preferable addition amount is 5% as the iron component in the flux.
The following can be included: This iron component is S
It is the total value of the iron component and iron powder of the iron alloy that is the raw material of i and Mn. When the additive material of Si and Mn is metal Si, metal Mn, and a Si-Mn alloy without the iron powder, the iron component may not be included.

FIGS. 3A and 3B show cross-sectional shapes of the flux-cored wire of the present invention. FIG. 1 (a) shows a steel pipe 1 made of a steel pipe, which is filled with a flux 2 by vibration, and then reduced in diameter to a strand, and further drawn to 0.8 to 2.0.
It is manufactured to a predetermined diameter of mm. Alternatively, the steel strip is sequentially formed into a U-shape, flux-filled, and O-shape in a forming process, then welded, reduced in diameter to a strand, and subsequently drawn into a wire to form a seam on the steel sheath. And a flux-cored wire for gas shielded arc welding can be manufactured. Such a wire having no seam in the steel sheath can obtain good weld metal performance without absorbing moisture in the outside air.

The flux-cored wire shown in FIG. 3 (b) is a wire in which a steel sheath 1 is filled with a flux 2 having a seam 3, and a steel strip is sequentially formed in a U-shape in a forming step.
Flux filling, forming into an O-shape, and subsequently reducing the diameter to obtain a strand, and further drawing. Since the filling rate of this wire is also low, the contact area of the outer seam is increased,
The effect of blocking the filling flux from the atmosphere is great, and the absorption of moisture in the atmosphere is extremely small. Further, the shape of the seam of the steel outer skin is not limited to the one shown in the figure, and may be a diagonal seam, which further improves the effect of blocking the atmosphere.

By having copper plating on the surface of the steel outer skin, the rust resistance of the outer skin surface is improved, or the wire feeding property is improved.
Electricity can be improved. On the other hand, in the case of a wire whose surface is not plated, a rust inhibitor and a lubricant are appropriately adhered to the surface of the wire to secure rust resistance and wire feedability.

The filling rate of the flux-cored wire of the present invention is 3 to 8%. If the filling rate is less than 3%, the flux filling and livelihood become difficult, resulting in poor productivity. If the filling rate exceeds 8%, the amount of slag and the amount of spatter increase, and the performance of the wire cannot be improved, and the wire drawing property at the time of manufacturing the wire is inferior and the productivity is reduced due to disconnection. However, in consideration of improved productivity, excess slag, and moisture absorption resistance, the filling rate is preferably 3.5 to 7.0%.

Although the above are the basic components constituting the present invention, the deoxidizing agent such as Ti, Al, Mg, Zr, etc. is blown by insufficient deoxidation of the weld metal as in the case of the flux cored wire for ordinary gas shielded arc welding. It is contained for preventing generation of holes and / or adjusting mechanical properties. However, when these are contained excessively, poor slag removability due to slag seizure, poor bead appearance, or excessively high strength of the weld metal deteriorates crack resistance. In addition, the deoxidizing agent forms a slag in addition to acting as a yield alloying agent in the weld metal, affects the composition and amount of the molten slag, and may impair the intended effect of the present invention. It is desirable to restrict.

The present invention is intended to adjust the mechanical properties of the weld metal, and to provide an alloy wire such as Ni, Mo, Cr, Ti, B, etc. in the filler flux as a welding wire adapted to the steel plate to be welded.
Slag stripping agents such as Bi and S can be appropriately added in consideration of the yield within a range that does not affect the basic technical idea of the present invention.

That is, when Ni: 0.4-3.0% is added, the strength and toughness of the weld metal can be improved, and when Mo: 0.5% or less, the strength and heat resistance of the weld metal can be improved.
Heat resistance, corrosion resistance, and weather resistance of the weld metal are improved by adding Cr: 0.5 to 3.0%, and mechanical properties of the weld metal by addition of Ti: 0.3% or less and B: 0.010% or less. Improve and adjust. These alloy components can be added alone or in combination depending on the purpose of improving the mechanical properties and physical properties of the weld metal. A similar effect can be obtained by incorporating these alloy components into the components of the steel shell in consideration of the yield at the time of welding or the like within a range in which workability is allowed.

The flux-cored wire of the present invention has a small diameter of 0.8 to 2.0 in order to increase the current density and obtain high welding properties.
0 mm is preferred.

Further, by improving the arc state by the arc stabilizer in a small diameter wire having a low filling rate of flux, the welding current range can be widened, for example, 120 to 550 A for a 1.2 mm diameter wire. Therefore, the working efficiency in a wide area can be greatly improved.

The arc gas using the flux-cored wire of the present invention uses a CO ₂ gas as a shielding gas to provide sufficient welding performance, but further reduces the amount of fume generated from the viewpoint of the welding operation environment. _Two mixed gas may be used.

Next, an example of manufacturing a flux-cored wire for gas shielded arc welding according to the present invention will be described.

The method of manufacturing a flux-cored wire according to the present invention is as follows. For a wire having no seam in a steel sheath, a steel pipe is installed in a vibrating device in a coil shape, and after filling flux with vibration, the diameter is reduced. A method for forming a product having a predetermined diameter of 0.8 to 2.0 mm by performing a wire drawing process and a wire having a predetermined diameter of 0.8 to 2.0 mm, or sequentially forming a strip in a U-shape, flux filling,
There is a manufacturing method in which an O-shaped wire is welded, reduced in diameter to obtain a strand, and subsequently drawn to form a wire.

In the case of a wire having a seam in a steel sheath, a U-shaped, flux-filled,
This is a manufacturing method in which a wire is formed by reducing the diameter of an O-shaped wire, then forming a wire, and subsequently drawing the wire. In this manufacturing method, a normal annealing step is appropriately performed in the middle of the wire drawing step.

[0040] As an example of the basic invention of the present invention, deoxidizing Si: 0.5%, Mn: 1.5% based, the Na ₂ CO ₃ as Na ₂ O source as arc stabilizers Na ₂ O 0.05%, 0.1%, 0.1% adjusted within the range of the present invention in terms of the converted value.
2%, 0.3%, 0.35%, 0.4%, 0.5%
Filling flux containing 58% of 8 kinds, Na ₂ O
When the converted value is set to less than the lower limit from the range of the present invention, 0%, 0.
01%, 0.02%, 0.65 set above the upper limit
%, 0.68% of the filling flux containing 5 types,
A flux-cored wire was filled with a pipe symbol P1 shown in Table 1 at a flux filling rate of 5% and drawn to an outer diameter of 1.2 mm. Using this wire, welding conditions were: welding current: 300 A, arc voltage: 33 V, welding speed: 30
Welding was performed at a flow rate of cm / min, a wire protrusion length of 20 mm, and a shielding gas of carbon dioxide gas at a flow rate of 25 L / min, and the number of droplet transfers during welding and the amount of spatter generated were investigated.

Investigation of the number of times of droplet transfer was performed by taking a picture of the welded portion with a high-speed video camera while performing automatic welding, performing slow playback of the result, and taking one cycle from the time when the droplet was generated at the wire tip and separated. The number of times was measured. The welding conditions were as follows: the number of frames to be photographed: 1000 frames / sec, shutter speed: 1/3000 sec, the result was played back slowly, and the number of times for one cycle until droplets were generated at the wire tip and separated was determined. I asked.

As shown in FIG. 1, within the range of the present invention (Na ₂ O
(Converted value: 0.05 to 0.6%), the number of droplet transfer times is large and good results are shown. However, in the case of the comparative example wire whose Na ₂ O conversion value was set to be less than the lower limit from the range of the present invention, N 2
The effect of a ₂ O becomes dilute, the number of droplet transfer times decreases, and the comparative example wire in which the Na ₂ O conversion value is set to exceed the upper limit from the range of the present invention promotes excessive ionization in an arc atmosphere, The droplet transfer was unstable and increased due to the longer arc length, and as a result, the number of droplet transfers decreased.

In order to investigate the amount of spatter generated, automatic welding was continuously performed for one minute, and spatter generated during welding was collected.
The measurement was performed three times for one type of wire, and the average value was evaluated.

FIG. 2 shows the result of investigation of the amount of spatter generated. The wire (equivalent to Na ₂ O: 0.05 to 0.6%) which is an example in the range of the present invention has a small amount of spatter and shows a good result. However, in the case of the comparative example wires terms of Na ₂ O values were set below the lower than the present invention range, Na ₂
The effect of O becomes weak, and the amount of spatters increases. Further, in the case of the comparative example wires terms of Na ₂ O value is set beyond the upper limit from the scope of the invention, the ionization in the arc atmosphere is excessively promoted, droplet transfer because the arc length is increased becomes unstable, its As a result, the amount of spatter generated increases.

From the above results, if the equivalent value of Na ₂ O contained in the filling flux as an arc stabilizer is 0.02 to 0.6% within the range of the present invention, the number of times of droplet transfer increases and finer It is grained, and the amount of spatter generated is reduced. However, when the value is set to exceed the lower limit or the upper limit of the range of the present invention, the number of droplet transfers is small, and the amount of spatters generated is large. The number of droplet transfers is 35 times / second or more, and the amount of spatter generated is 1.0 g.
/ Min or less was a good range.

[0046]

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

The components of the outer shell mild steel pipe used in the present invention and the comparative examples are as follows: Mild steel pipe symbol P1 shown in Table 1 and seamed wire H1 shown in Table 1 are filled with a flux having the composition shown in Table 2 in strip steel symbol H1. , Rolling and die wire drawing, softening and dehydrogenation, and subjected to intermediate annealing to obtain wire symbols W9, 1
Plating treatment was performed except for 0, 21, and 22, and wire drawing was performed to produce a flux-cored wire with or without a seam on a steel outer cover.

[0048]

[Table 1]

W1 to W14 shown in Table 1 are examples of the present invention, and W11 and thereafter are comparative examples.

The welding conditions of the present invention example and the comparative example shown in Table 1 were as follows: welding current: 300 A, arc voltage: 33 V, welding speed: 30 cm / min, wire protrusion length: 20 m
Welding was performed at a flow rate of 25 m / m 2 of carbon dioxide gas, and the amount of spatter generated, the number of droplet transfers, the standard deviation of the droplet transfer cycle, and the slag state were investigated. Regarding the amount of spatter generated, welding was performed for 1 minute, spatter generated during the welding was collected, performed three times for one wire, and the average value of the collected amount was evaluated.

Regarding the number of droplet transfer and the standard deviation of the droplet transfer cycle, the arc phenomenon during welding was photographed with a high-speed video camera, and the number of droplet transfer per second, droplet diameter, and arc width were measured. The measurement was performed three times for one wire, and the average value was evaluated. Regarding the slag state, the amount of slag generated on the weld bead after welding and the releasability were visually examined by hitting with a small hammer. The mechanical properties of the weld metal are based on JISZ3311 based on tensile test pieces (JISZ33).
2201 A1) and an impact test piece (JISZ2242)
No. 4) was prepared and tested.

Table 2 shows the results of the welding test.

[0053]

[Table 2]

[0054]

[Table 3]

The number of times of droplet transfer of the wire of the present invention shown by W1 to W14 is 40 times / second or more and the standard deviation of the droplet transfer cycle is 9
In the following, both good and stable welding can be performed, and as a result, the amount of generated spatter is as small as 1.0 g / min or less. In addition, the amount of slag generated was small, and good releasability was obtained.

On the other hand, W15 to W25 are comparative examples.

Since W15 had a low filling factor of 2.2% and Si was less than the range of the present invention, the deoxidizing effect in the weld metal was not obtained, and blow holes were generated in the weld metal.

W16 has a high filling ratio of 9%,
However, since the ratio exceeds the range of the present invention, the strength of the weld metal was excessive, and the toughness was deteriorated. In addition, N is used as an arc stabilizer.
Since a ₂ O exceeds the range of the present invention, the effect as an arc stabilizer becomes excessive, the arc length becomes longer than necessary, and the droplet transfer becomes unstable. Therefore, the standard deviation of the droplet transfer cycle shows a large value, and the amount of spatter generated is also 1.35.
g / min.

In the case of W17, since Na ₂ O is less than the range of the present invention as an arc stabilizer, the effect as an arc stabilizer is weak, the number of droplet transfer times is small, and the standard deviation of the droplet transfer period shows a large value. The arc state became unstable, and as a result, the amount of spatter generated increased.

In the case of W18, Na ₂ O and an arc stabilizer are beyond the range of the present invention, so that the effect as an arc stabilizer becomes excessive, the arc length becomes unnecessarily long, and the transfer of droplets becomes unstable. The standard deviation of the drop transfer cycle showed a large value, the arc state became unstable, and as a result, the amount of spatter generated increased.

Since Mn of W19 was less than the range of the present invention, the deoxidizing effect in the weld metal was not obtained, and blow holes were generated in the weld metal. In addition, Na as an arc stabilizer
_{Since 2} O is less than the range of the present invention, the effect as an arc stabilizer is dilute, the number of droplet transfer times is small, the standard deviation of the droplet transfer period shows a large value, and the arc state becomes unstable, resulting in spatter generation. The amount has also increased.

Since the Mn of W20 exceeds the range of the present invention, the strength of the weld metal becomes excessive and the toughness deteriorates. Furthermore, since Na ₂ O and the like are less than the range of the present invention as an arc stabilizer, the effect as an arc stabilizer is dilute, the number of droplet transfer times is small, the standard deviation of the droplet transfer period shows a large value, and the arc state Became unstable, resulting in an increase in the amount of spatter generated.

W21 is an example in which there is a seam in the outer skin and no plating is performed. However, since Na ₂ O is beyond the range of the present invention as an arc stabilizer, the effect as an arc stabilizer is excessive and the arc length is longer than necessary. And the droplet transfer became unstable, the standard deviation of the droplet transfer cycle showed a large value, the arc state became unstable, and as a result, the amount of spatter generated increased.

In the case of W22, TiO ₂ as an arc stabilizer is beyond the range of the present invention, so that the effect as an arc stabilizer becomes excessive, the arc length becomes longer than necessary, the droplet transfer becomes unstable, and the droplet transfer cycle becomes unstable. Shows a large standard deviation of 16.0, the arc state became unstable, and as a result, the amount of spatter generated increased to 2.30 g / min. Also,
The slag became slightly hard and the peelability deteriorated.

W23 and 24 are solid wires,
Since Na ₂ O cannot be contained as an arc stabilizer, the number of droplet transfers was small, a more stable arc was not obtained, and there was no effect of reducing the amount of spatter generated.

Although W25 is a metal-based flux-cored wire containing a large amount of rutile, it does not contain an arc stabilizer, so the number of times of droplet transfer is small, and there is a large amount of slag, so that the effect of reducing slag like a solid wire is obtained. Could not be obtained. Since the arc was always somewhat unstable, the amount of spatter generated was larger than that of the present invention.

Next, a description will be given of an embodiment of a pipe having a sheath and a wire in which the components of the steel strip are changed.

Using the pipes and strips shown in Table 1,
The flux was filled with a combination of a pipe and a strip shown in Table 2 and the same manufacturing method, welding method and measuring method as those of the wire shown in Table 2 were performed.

Table 5 shows the welding results.

[0070]

[Table 4]

[0071]

[Table 5]

The wires of the present invention shown in WPs 26 to 28 and WHs 29 and 30 were adjusted for Si and Mn by the outer shell component and the filling flux, but the number of droplet transfer times and the standard deviation of the cycle were both good and stable welding was performed. And the amount of spatter generated is small. Good results were also obtained with respect to the slag removability.

On the other hand, W31 to W33 are comparative examples.

The WP31 has a Si content of 2.18 in the wire.
%, The droplet became large, and therefore the standard deviation of the droplet transfer cycle was large, and the amount of spatter generated increased.

[0075] W32 is, Si content in the wire is in the same manner as WP31 many further Na ₂ O is less droplet transfer times because it exceeds the upper limit value, also unstable arc arc length runs out long sputtering The amount generated is large.

In the case of W33, since the Mn in the wire is as large as 4.65%, the droplet becomes large. Therefore, the standard deviation of the droplet transfer period is large, the arc becomes unstable, and the spatter generation amount is the largest. Met.

[0077]

As described above, the flux-cored wire for gas shielded arc welding of the present invention has a very stable arc, a small flow of droplets and little spatter, and has good welding workability and good weld bead shape. In addition, it can improve the quality of the welded portion and the welding efficiency, and contribute to the efficiency of welding work with different thicknesses and materials.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing the effect of a Na ₂ O conversion value in a filling flux on the number of droplet transfers.

FIG. 2 is a graph showing the effect of Na ₂ O-equivalent value in a filling flux on spatter generation.

FIG. 3 shows a cross section of a flux-cored wire for gas shielded arc welding of the present invention, wherein (a) shows a seamless wire,
(B) is a schematic sectional view of a seamed wire.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Miyake 3-5-4 Tsukiji, Chuo-ku, Tokyo Inside Nippon Steel Welding Industry Co., Ltd. (72) Inventor Yuji Suzuki 3-5-chome Tsukiji, Chuo-ku, Tokyo No. 4 Nippon Steel Welding Industry Co., Ltd. Research Laboratory (72) Inventor Rikiya Takayama 3-4, Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd. F-term (reference) 4E084 AA02 AA09 BA02 BA03 BA04 CA24 CA25 DA10 EA06 HA12

Claims (5)

[Claims] 1. A flux-cored wire for gas shielded arc welding, wherein a steel sheath is filled with a flux, and Si: 0.3 to 1.8% by total mass of the wire.
(Total wire mass%, the same applies hereinafter), Mn: 0.8 to 4.0
%, A Na ₂ O source as an arc stabilizer in an amount of 0.05 to 0.6% in terms of Na ₂ O, and a flux filling rate of 3 to 8%.
A flux-cored wire for gas shielded arc welding, characterized in that the content is mass%. _2. The TiO ₂ source in the filling flux is TiO ₂
2. A conversion value containing 2.0% or less.
The flux-cored wire for gas shielded arc welding according to the above. 3. The flux-cored wire for gas shielded arc welding according to claim 1, wherein the filling flux contains iron powder. 4. The flux cored wire for gas shielded arc welding according to claim 1, wherein the steel sheath is seamless. 5. The flux-cored wire for gas shielded arc welding according to claim 1, wherein a copper plating is provided on a surface of the steel sheath.