JP2000301382A - Flux-cored wire for self-shield welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flux-cored wire for self-shield welding having excellent welding workability that a welding metal has high resistance to forming pores and toughness. SOLUTION: The flux-cored wire for self-shield welding, is filled in the steel- made outer shell with the flux. The flux component based on the whole wt. of the wire, contains, by weight, essentially 1.5-4.0% Al, 0.5-2.0% Mg, 1.0-4.8% Ba, 0.05-4.00% Li, 0.1-3.0% Ni, 0.5-3.0% Mn, 0.01-0.30% C, 0.01-0.50% Si, 0.5-4.0% F and 0.1-21.0% O and further, if necessary, one or more kinds of 0.01-2.00% Sr, 0.01-4.00% Ca and FP value defined in the following formula is >=0.00. FP=C-0.145 Si+0.013 Mn-0.228 Al+0.199 Ni+0.393.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux cored for self-shielded welding, which has excellent welding workability, and in which a weld metal obtained by welding can obtain excellent porosity resistance and high toughness. It is about wires.

[0002]

2. Description of the Related Art Conventionally, a flux cored wire for self-shielding welding has been mainly used in civil engineering and construction because of its simplicity of welding without using a shielding gas. However, the conventional flux cored wire for self-shielded welding has poor welding workability and low toughness of the obtained weld metal as compared with a normal semi-automatic welding wire using a shielding gas. Therefore, for example, Japanese Patent Laid-Open No.
No. 3, JP-A-4-13497, JP-A-5-3
As described in JP-A-93, efforts have been made to improve welding workability and increase toughness, but welding wires having both welding workability and high toughness are still being developed. Has not been done. As a result, the use of a weld metal in a part where the required value of the mechanical performance is high is restricted, and the fact is that it is not widely used.

[0003]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention has excellent welding workability, and a weld metal obtained by welding can obtain excellent porosity resistance and high toughness. It is an object of the present invention to provide a flux cored wire for self-shield welding.

[0004]

As a result of repeated studies to solve the above-mentioned problems, the present inventor has found that a method for improving workability, that is, obtaining a stable arc and reducing the amount of spatter generated. A method of reducing the number of flux cored wires and a flux cored wire for self-shielded welding which can obtain a weld metal having a better bead appearance, excellent porosity resistance and high toughness have been completed.

That is, the present invention relates to a flux cored wire for self-shielding welding in which a flux is filled in a steel sheath, wherein the flux component is wt. 4.0%, Mg: 0.5
To 2.0%, Ba: 1.0 to 4.8%, Li: 0.05
-4.00%, Ni: 0.1-3.0%, Mn: 0.5
To 3.0%, C: 0.01 to 0.30%, Si: 0.
01 to 0.50%, F: 0.5 to 4.0%, O:
It has 0.1 to 21.0% as a main component, and has an FP value defined by the following formula of 0.00 or more. FP = C-0.145 Si + 0.013 Mn-0.228 Al + 0.19
9 Ni + 0.393 Here, the symbol of the element in the PF formula means the content wt% of the element with respect to the total weight of the wire.

In explaining the reasons for limiting the flux component of the flux cored wire for self-shielded welding of the present invention, first, a method for stabilizing an arc, a method for reducing spatter, a method for improving porosity resistance, and a method for improving a weld metal. Action of the flux component in the method of improving toughness,
The function will be described.

[0007] Regarding the stabilization of the arc, Al, Ba, M
The simultaneous addition of g is effective. Al readily evaporates at high temperatures in the arc and then ionizes and acts as a source of electrons in the arc. At this time, to effectively generate Al gas, it is effective to use Al in a metal state or an alloy state as a flux.
A strong oxide is formed on the surface, and this oxide
Hinders smooth evaporation. Here, Mg is added or M
By alloying with g, the strong oxide is removed in the heating process, and Al can be effectively evaporated and ionized.

[0008] Now, the transition state of the droplet in the state where Al and Mg are added is a transition state of the droplet whose droplet size is larger than the wire diameter, which is called globule transition. It flashes with the transfer of the drops, which is undesirable. When a Ba compound such as barium fluoride or barium carbonate is added here, the surface state of the droplet changes, and the droplet shifts to a small spray, and a stable arc state is realized. In order to obtain such a stable arc, A
It is necessary to simultaneously add 1, Mg, and Ba.

Next, a method for suppressing spatter will be described. As spatter generation in self-shielded welding,
Sputtering caused by the blinking of the arc, spattering caused by nitrogen, spattering from the molten pool, and the like are considered.

[0010] The spatter caused by the above-mentioned arc blinking can be reduced by stabilizing the arc by simultaneous addition of Al, Mg and Ba.

The mechanism by which the above-mentioned nitrogen-induced sputtering occurs is as follows. First, nitrogen invading the arc is easily dissociated into nitrogen atoms depending on the temperature of the arc. Nitrogen atoms easily penetrate the iron droplet. Since the amount of dissolved nitrogen in molten iron in nitrogen plasma is said to be about 20 times the amount of dissolved nitrogen in nitrogen gas (JIMS Vol. 22, No. 5, 1988, 412P). When the iron droplet that has sufficiently absorbed nitrogen in the plasma moves out of the plasma, the nitrogen is immediately vaporized and released outside the droplet.
At this time, since nitrogen is released while explosively blowing off a part of the droplet, spatter occurs.

In order to suppress the spatter generated by the above mechanism, two methods are conceivable. First, the first method is to reduce the nitrogen concentration in the arc. An effective method for this is to increase the amount of flux as a gas generating agent. Therefore, it is better that the amount of flux filled in the self-shielding welding wire is large. As a gas generating agent for reducing nitrogen contamination, Mg, a substance that easily evaporates, a fluoride such as barium fluoride, calcium fluoride, or strontium fluoride, or a carbonate compound such as barium carbonate is effective. Next, as a second method, the addition of Al is effective. That is, droplets that have sufficiently absorbed nitrogen atoms in the plasma region release nitrogen outside the plasma,
When l is added, the amount of nitrogen released by forming AlN can be reduced, and consequently sputtering can be reduced. As described above, spatter can be suppressed by increasing Al and Mg in the wire.

For suppressing the spatter from the molten pool, it is effective to control the fluctuation of the molten pool due to slag and to control the fluidity. Slag is mainly formed in the form of fluorides, carbonates and oxides of Ba, Sr and Ca, and addition of Si and Li is effective for controlling the properties of the molten pool by the slag. Si combines with the oxygen in the arc or the oxygen in the flux and becomes a Si oxide on the weld metal to form slag. The Si oxide has a high viscosity in a molten state, and suppresses violent vibration of the molten pool, and as a result, suppresses spatter generated from the molten pool. However, on the other hand, the flow of the Si oxide is poor due to its high viscosity, does not cover the entire molten metal, and causes a decrease in slag coverage. In order to give the slag an appropriate viscosity, it is appropriate to add Li. By adding Li, a molten slag having an appropriate viscosity is formed. As a result, both the stabilization of the molten pool and the improvement of the slag coverage are improved. Is achieved.

The above-mentioned Li, Si and Al, M
By the action of g, Ba, Sr, Ca, O, and F, the properties of the slag that covers the bead change. Depending on the addition amount of these elements, slag is not formed, or the viscosity of the slag is too high or too low, the width and height of the bead become uneven, and the slag becomes Problems such as the bead shape being distorted due to biting occur. Appropriate component adjustments improve the appearance of the resulting weld metal.

Next, a method for improving the porosity resistance of the weld metal will be described. Mg has the effect of reducing the nitrogen concentration in the arc by gas generation and suppressing the generation of pores. A
1 has a function of fixing dissolved nitrogen and suppressing generation of pores. That is, pores in the weld metal are generated when the weld metal is solidified, but immediately before solidification, Al fixes dissolved nitrogen in the form of AlN, so that the generation of pores can be suppressed.

Next, a method for improving the toughness of the weld metal will be described. When Al in the wire is increased, the amount of Al in the weld metal is also increased, and the toughness of the weld metal is degraded. Therefore, in the prior art, if the Al is increased to improve the welding workability, the toughness of the weld metal is reduced. Conversely, if the Al content in the wire is reduced to improve the toughness of the weld metal, the welding workability is reduced. Therefore, a self-shielding welding wire satisfying both characteristics of the welding workability and the weld metal toughness could not be obtained. Therefore, in the present invention, while increasing the amount of Al in the wire that is effective in reducing spatter, the toughness of the weld metal is improved, and in order to devise a method that satisfies both welding workability and weld metal toughness, Al and the function of Al in the weld metal were carefully separated to clarify the function. That is, spatter depends on the amount of Al in the droplet during transfer of the droplet, but is not affected by the amount of Al in the weld metal. On the other hand, the toughness of the weld metal is governed by the amount of Al in the weld metal. From this, after the droplet transfer, Al in the weld metal was removed by the iron slag reaction, and A in the weld metal was removed.
If the amount of l can be reduced, a high toughness weld metal can be obtained without impairing the welding workability. Furthermore, even if Al is contained in the weld metal, the addition of an element capable of improving the toughness in the weld metal can positively improve the weld metal toughness.

In order to remove Al in the weld metal by the iron slag reaction, the flux may be positively filled with an oxide, a carbonate compound, or a compound containing oxygen. If the oxide is filled in the flux, Al can be removed from the weld metal by the metal slag reaction at the interface between the slag covering the upper portion of the weld metal and the weld metal after the transfer of the droplet. Here, the most effective one is a Li-based oxide. This is because the Li-based oxide has a low melting point and the removal of Al by the metal slag reaction works effectively down to a low temperature just before Fe solidification. Thus, Al in the obtained weld metal is reduced by the oxide, and as a result, the toughness of the weld metal is improved.

On the other hand, in order to improve the toughness of the weld metal, the addition of Ni and Mn is effective. As a result of detailed examination of the toughness deterioration of the weld metal due to the addition of Al, the solid solution of Al in the weld metal stabilizes the ferrite, and the coarse δ ferrite generated during solidification remains even during cooling. I understood that. That is, in the weld metal of steel, coarse δ ferrite is usually generated during solidification, and is completely transformed into austenite once in the subsequent cooling process, and then transformed from austenite to fine ferrite. In this case, the structure of the weld metal becomes fine and the toughness becomes good. In contrast, it has been found that when Al is added, coarse δ ferrite is not sufficiently transformed into austenite in the cooling process. Therefore, in order to improve toughness, it is necessary to promote transformation to austenite.

Ni is an element for stabilizing austenite, promotes transformation of coarse δ ferrite into austenite, is effective for remaining fine δ ferrite,
Is effective for improving the toughness of the weld metal. Mn is also an austenite stabilizing element and has the effect of making the transformation composition from austenite fine and increasing the toughness. Ni and Mn have the above-mentioned effects even when added alone,
When added at the same time, it acts to stabilize the refinement of the transformation composition. That is, the addition of Ni or Mn alone causes a variation in the toughness value of the weld metal.
Due to the synergistic effect of i and Mn, variation in toughness value is reduced, and high toughness can be stably secured. Further, C is also one of the austenite stabilizing elements, and has an effect of suppressing the remaining δ ferrite. Further, it has the effect of improving the strength of the weld metal.

In the welding wire of the present invention, a part of the object of the present invention, that is, the toughness of the weld metal cannot be satisfied only by adjusting the chemical composition of the above-mentioned flux component. FP value must be 0 or more. The equation defining this FP (ferrite parameter) is obtained from thermodynamic calculations and experiments and is an index of whether or not the weld metal transforms to austenite during cooling. If the FP value is 0.00 or more, the toughness of the weld metal is good, but if the FP is less than 0.00, coarse δ ferrite that does not completely transform into austenite remains and the toughness of the weld metal deteriorates. .

As described above, arc stabilization by adding an appropriate amount of Al, Mg, Ba, Al, Mg, Ba, S
Improvement of welding workability by adding appropriate amounts of i, Li, O, removal of Al from weld metal by adding appropriate amounts of O, Ni, Mn, C
By improving the metal toughness by adding an appropriate amount of, and controlling the addition amount by FP, it is possible to obtain a flux cored wire for self-shielded welding that satisfies both characteristics of the welding workability and the weld metal toughness.

Here, the addition range (unit: wt%) of each flux component in the present invention and the reason for the limitation will be specifically described. Incidentally, the flux component in the present invention,
It does not mean only the components contained as flux, but the components that act and function as flux.The supply form is contained not only as flux but also as a component of the steel outer shell filled with flux. Things are included.

C: 0.01 to 0.30% C is one of the austenite stabilizing elements and has an effect of suppressing the remaining δ ferrite. Further, it has the effect of improving the strength of the weld metal. If the C content is less than 0.01%, the effect of suppressing the residual δ ferrite is too small.
If it exceeds 0.30%, the toughness deteriorates due to an increase in strength. For this reason, the lower limit of the C content is set to 0.01%, preferably 0.02%, and the upper limit is set to 0.30%, preferably 0.1%.
2%.

Si: 0.01 to 0.50% Si improves the viscosity of the weld metal and the shape of the weld bead. It also controls the viscosity of the slag. On the other hand, Si
Is a solid solution strengthening element and a ferrite stabilizing element. Therefore, if the content of Si is less than 0.01%, the shape of the weld bead becomes unstable, and the slag fogging becomes poor. As a result, the effect of removing slag by Al is reduced.
If it exceeds 0.50%, the strength becomes too high, which causes deterioration of toughness. Therefore, the lower limit of the amount of Si is set to 0.01%, preferably 0.05%, and the upper limit is set to 0.50%, preferably 0.30%.

Ni: 0.1 to 3.0% Ni is one of the austenite stabilizing elements like C, and has an effect of suppressing the remaining δ ferrite. If the Ni content is less than 0.1%, the effect of suppressing coarse ferrite cannot be sufficiently exhibited, and the toughness of the weld metal decreases. On the other hand, if the Ni content exceeds 3.0%, the strength of the weld metal significantly increases. The toughness of the steel deteriorates. Therefore, the lower limit of the Ni content is set to 0.1%, preferably 0.5%, and the upper limit is set to 3.0%.
%, Preferably 2.0%.

Mn: 0.5 to 3.0% Mn is one of the austenite stabilizing elements like C, and has an effect of suppressing the remaining δ ferrite. If the Mn content is less than 0.5%, the effect of suppressing coarse ferrite cannot be sufficiently exhibited, and the toughness of the weld metal is reduced. If the Mn content exceeds 3.0%, the strength of the weld metal is significantly increased. The toughness deteriorates. For this reason, the lower limit of the Mn content is set to 0.5%, preferably 0.8%, and the upper limit is set to 3.0%.
Preferably, it is 2.0%.

Al: 1.5 to 4.0% If Al is less than 1.5%, the deoxidizing and denitrifying effects of the weld metal will be insufficient, and pits or blow holes will be generated in the weld metal. Further, the welding workability is significantly deteriorated.
At 1.5% or more, pits and blow holes are eliminated, and welding workability is improved. On the other hand, if the Al content exceeds 4.0%, the Al content in the weld metal increases, and the toughness of the weld metal decreases, which is not preferable. For this reason, the lower limit of the amount of Al is set to 1.
5%, preferably 1.9%, with an upper limit of 4.0%, preferably 3.5%.

Mg: 0.5% to 2.0% Mg turns into a metal vapor by arc heat and shuts off the arc atmosphere from the atmosphere. In addition, it has a strong deoxidizing action, removes an oxide film on the surface of Al, and promotes evaporation of Al. Mg is 0.
If it is less than 5%, the shielding property is deteriorated, and blow holes and pits are generated. When it exceeds 2.0%, Mg reacts explosively, so that spatter increases and welding workability deteriorates. For this reason, the lower limit of the amount of Mg is set to 0.5%, preferably 0.7%, and the upper limit is set to 2.0%, preferably 1.5%.

Ba: 1.0 to 4.8% Ba is added in the form of fluoride to improve the stability of the arc and reduce the amount of spatter. Further, it contributes to the formation of slag, and stabilizes the bead shape by adding an appropriate amount. 1.0
%, The transition state of the droplet becomes a drop transition, and the spatter of large grains increases. In addition, the slag fogging becomes worse. On the other hand, if it exceeds 4.8%, the viscosity of the slag increases, and the bead shape deteriorates. For this reason, the lower limit of the amount of Ba is set to 1.0%, preferably 1.2%, and the upper limit is set to 4.8%.
Preferably, it is 4.0%.

F: 0.5 to 4.0% F is filled as a Ba, Sr and Ca compound and acts as a gas generating agent. In addition, slag is formed. 0.5%
If it is less than 4.0%, no slag is formed, and if it exceeds 4.0%, the arc is disturbed and welding workability deteriorates. For this reason, the lower limit of the amount of F is set to 0.5%, preferably 0.8%,
The upper limit is set to 4.0%, preferably 3.8%.

O: 0.1-21.0% O plays an important role for the wire of the present invention to maintain good welding workability and good toughness of the weld metal at the same time. The most important element for improving the welding workability in the self-shielding welding wire of the present invention is Al in the wire. However, Al in the wire migrates into the weld metal, and Al in the weld metal deteriorates the toughness of the weld metal. In order to improve this, it is necessary to reduce the amount of Al yielded in the weld metal. At this time, if the wire is filled with oxygen in the form of an oxide, a carbonate compound, or another compound, Al is oxidized by a slag metal reaction, and the amount of Al retained in the weld metal also decreases. For this purpose, the O content must be 0.1% or more. On the other hand, if it exceeds 21.0%, generation of spatter due to decomposition of an oxide, a carbonate compound or a compound containing oxygen filled as an oxygen source cannot be ignored, and welding workability deteriorates. For this reason, the lower limit of the amount of O is 0.1
%, Preferably 0.2%, more preferably 0.3%, and the upper limit is 21.0%, preferably 15.0%, more preferably 12.0%. The analysis of the oxygen content relative to the total weight of the flux cored wire for self-shielded welding is performed by an inert gas melting infrared absorption method.

Li: 0.05 to 4.00% Filled in the form of oxide, contributes to the formation of slag, and stabilizes the bead shape by adding an appropriate amount. The form of the oxide is preferably a form of a composite oxide of Si, Al, and Fe.
Li contributes to lowering the melting point of the slag, lowering the viscosity, stabilizing the slag, and lowering the yield of Al in the weld metal. If it is less than 0.05%, the effect is too small.
On the other hand, if it exceeds 4.00%, the arc is disturbed, and welding workability deteriorates. Therefore, the lower limit of the Li amount is set to 0.05%, preferably 0.20%, and the upper limit is set to 4.00%, preferably 3.50%.

FP value: 0.00 or more FP = C-0.145 Si + 0.013 Mn-0.228 Al + 0.19
9Ni + 0.393 With the self-shielding welding wire of the present invention, it is not possible to satisfy a part of the object of the present invention, that is, the toughness of the weld metal by simply adjusting the above chemical composition. FP must be 0.00 or more. This FP is an index of whether or not the weld metal transforms to austenite during cooling. FP is 0.00
If it is above, the toughness of the weld metal is good, but if the FP is less than 0.00, coarse δ ferrite which does not completely transform into austenite remains, and the toughness of the weld metal deteriorates.

FIG. 1 is a graph showing the results of an investigation of the relationship between the FP value and the toughness of the weld metal and the relationship between the FP value and the area ratio of δ ferrite in the weld metal. Since the amount of δ ferrite increases, the toughness of the weld metal is reduced to 30 J or less, while when the FP value is 0 or more, the δ ferrite decreases and the toughness of the weld metal is improved to 50 J or more. Although there is data showing that the toughness value is low even though the FP value is 0 or more, this is because C was added as much as 0.35% to adjust the components.
This is because the strength of the weld metal has become too high.
The wires used in this investigation were manufactured by adjusting the flux components to have wires having various FP values in the same manner as in Examples described later, and welding was performed in the same manner. The area ratio of δ ferrite was obtained by observing the weld metal with an optical microscope and measuring the proportion of δ ferrite.

The flux component of the flux cored wire for self-shielding welding of the present invention contains the above components as main components. Here, the main component means, in addition to the case of the above components and unavoidable impurities, an effect that does not impair the action of the main component, an element that does not impair the effect, and a content as an element that further improves the effect and effect of the flux. For example, one or more of the following Sr, Ca, and Cr can be contained, and as described in claims 2 to 4, the following components can be used. (1) Main component + Sr (2) Main component or component (1) + Ca (3) Main component, component (1) or component (2) + Cr

Sr: 0.01 to 2.00% Sr is filled in the form of fluoride to improve slag fogging and slag peelability. If the content of Sr is less than 0.01%, the effect is too small. For this reason, Sr
The lower limit of the amount is 0.01%, preferably 0.10%, and the upper limit is 2.00%, preferably 1.80%.

Ca: 0.01 to 4.00% Ca improves the slag fog and the bead appearance. If the content of Ca is 0.01% or less, the effect is too small. If the content exceeds 4.00%, the arc is disturbed, and the welding workability is deteriorated. For this reason, the lower limit of the Ca content is set to 0.01%, preferably 0.10%, and the upper limit is set to 4.00%, preferably 3.80%.

Cr: 0.5% or less Cr can be added to a self-shielded welding wire to improve corrosion resistance. If Cr exceeds 0.5%, the toughness of the weld metal deteriorates. Therefore, the upper limit is set to 0.
5%, preferably 0.3%.

The flux component may be added in any form as long as the amount of each element of the flux component satisfies the above range. That is, the individual elements of the flux component may be added in a single state, or may be added in the form of a compound. Furthermore, as described above, as long as the function and function as a flux are not lost, the steel may be added as a steel component forming an outer skin. Components that can be included in such an outer skin include Al, M
n, Ni, Si, C, Cr and O can be mentioned.

In the present invention, since the flux component is specified as a ratio to the total weight of the wire, the filling rate of the flux into the steel sheath is not particularly specified. For this purpose, the filling rate of the flux is set to 10 to 30% by weight based on the total weight of the wire. As shown in FIG. 2, the form of the steel outer shell 1 in which the flux 2 is included is as follows: (A) a cylindrical shape in which both ends are joined, and (B) a cylindrical shape in which both ends are overlapped (lap type). (C) Various shapes such as a cylindrical shape (apple type) in which both ends are overlapped and folded inward can be used.

[0041]

Next, the present invention will be described with reference to examples.
The present invention is not construed as being limited by the following examples.

Flux was charged into a steel pipe made of mild steel having the following components so that the flux components described in Tables 1 to 3 below were obtained, and the wire was drawn by a conventional method to obtain a flux cored wire sample having a wire diameter of 1.4 mm. Was manufactured. The flux filling rate was 20% based on the total weight of the wire. The outer skin was of a wrap type shown in FIG. 2 (B). Tables 1-3
The flux components shown in are based on the total weight of the wire, and when the flux components are added as flux,
As a rule added Al, Mg, Ni, Mn, Cr, Si in the state of a single or alloy, Ba and Sr are added as BaF _2, SrF ₂ respectively, Li is LiFe O
Added as ₂ . Some of C and Mn were also supplied from the outer skin.・ Skin component (wt%) C: 0.010%, Mn: 0.35%, P: 0.015
%, S: 0.007%, balance substantially Fe

A test plate (JIS G3106) in which a V-shaped groove was formed using the flux cored wire of each sample.
JIS for SM490B, 20mm thick x 500mm long)
Welded according to Z3111. At this time, the welding workability was evaluated by visually observing the spatter generation state during welding and the bead appearance.

Further, the porosity of the weld metal was examined using the test plate after welding in the following manner. An X-ray transmission test was performed in accordance with JIS Z3104, and those with a classification of 1 type and 1 class were regarded as good, and those with other classifications as poor. Further, the toughness of the weld metal was examined by an impact test, and the impact value at 0 ° C. was 50%.
J and above were considered good, and less than J were poor. The results of these investigations are also shown in Tables 1 to 3. In addition,
In Tables 1 to 3, in each column of spatter (generation state), bead appearance, porosity resistance and toughness, ○ indicates good and X indicates poor.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

From Tables 1 to 3, it can be seen that the inventive examples are excellent in welding workability, bead appearance, and porosity resistance, and that the weld metal has an impact value of 50 J or more at 0 ° C. and excellent toughness. Understand.

On the other hand, in Sample No. 5 in Table 1, the C content was large, so that the strength of the weld metal was too high and the toughness was deteriorated. In No. 6, since the amount of Si was small, the bead appearance deteriorated. No. 9 has a large amount of Si, and the FP value is less than 0, so that the toughness is deteriorated. No. 10 is Al
Because the volume is small, blowholes are generated in the beads,
Many spatters occurred. No. 20 has a large amount of Al and F
Since the P value is less than 0, the toughness is deteriorated.

Also, No. 24 in Table 2 has a large amount of Mg, so that spatter increases and the weldability is poor. No. 30 had a large amount of Ba, so the bead appearance deteriorated. In No. 43, since the amount of Li was large, the arc became unstable and the spatter increased.

Further, in Sample No. 63 in Table 3, the toughness was deteriorated due to the large amount of Cr. In No. 65, since the content of Ca and F was large, the bead appearance deteriorated and spatter increased.
In No. 66, since Li was added as AlLi, O
The bead appearance deteriorated due to the reduced amount and poor slag formation. In No. 67, Si is SiO ₂ , B
Since a was added as BaCO ₃ and Li as LiFe O ₂ , the O content became excessive and the spatter increased, resulting in poor weldability.

[0052]

As described above, according to the flux cored wire for self-shielded welding of the present invention, a weld metal having excellent welding workability and excellent in porosity resistance and toughness can be obtained. This greatly breaks the application limit of the self-shielding welding wire, and the utility value in the field of self-shielding welding is remarkable.

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of FP (ferrite parameter) on the amount of δ ferrite and the toughness value.

FIG. 2 is a cross-sectional view of a flux cored wire for self-shielding welding having various outer shapes.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroyuki Morimoto 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Research Institute, Kobe Steel, Ltd. (72) Inventor Akira Yamamoto Character of Miyamae, Fujisawa-shi, Kanagawa 100-1 Urakawachi Co., Ltd.Fujisawa Plant of Kobe Steel Ltd. (72) Inventor Takeshi Kurokawa 100-1 Urakawachi Miyama-shi, Fujisawa-shi, Kanagawa Prefecture Co., Ltd.Fujisawa Plant of Kobe Steel Co., Ltd. (72) Inventor Fusaki Koshiishi Kanagawa 100-1 Urakawachi, Miyamae, Fujisawa-shi, Japan F-term in the Kobe Steel Fujisawa Plant (reference) 4E084 AA44 BA03 BA04 BA05 BA06 BA08 BA10 BA16 BA17 BA18 DA14

Claims (4)

[Claims] 1. A flux cored wire for self-shielding welding in which a flux is filled in a steel sheath, wherein a flux component is wt.% With respect to the total weight of the wire, and Al:
1.5-4.0%, Mg: 0.5-2.0%, Ba:
1.0 to 4.8%, Li: 0.05 to 4.00%, N
i: 0.1 to 3.0%, Mn: 0.5 to 3.0%, C
: 0.01 to 0.30%, Si: 0.01 to 0.50
%, F: 0.5 to 4.0%, O: 0.1 to 21.0
% As a main component, and a flux cored wire for self-shielding welding having an FP value defined by the following formula of 0.00 or more. FP = C-0.145 Si + 0.013 Mn-0.228 Al + 0.19
9 Ni + 0.393 However, the symbol of the element in the PF formula means the content wt% of the element with respect to the total weight of the wire. 2. The flux component according to claim 1, further comprising 0.01 to 2.00% of Sr based on the total weight of the wire.
The flux cored wire for self-shielded welding described in the above. 3. The flux component further contains 0.01 to 4.00% of Ca based on the total weight of the wire.
Or the flux cored wire for self-shielded welding described in 2. 4. The flux cored wire for self-shielding welding according to claim 1, wherein the flux component further contains Cr: 0.5% or less based on the total weight of the wire.