JP6453178B2 - Flux-cored wire for gas shielded arc welding - Google Patents

Description

  The present invention relates to a flux-cored wire for gas shielded arc welding. More specifically, the present invention relates to a flux-cored wire for gas shield arc welding that can be suitably used for all-position welding including a vertical posture.

  In the marine structure field and the line pipe field, the deepening of the water area that promotes energy resource development, the exploration of resources to the extreme waters such as the Arctic Ocean, and the expansion of facilities are progressing. Against the background of such technological trends, in the design of offshore structures and line pipes, higher strength and higher toughness have progressed, and the required performance for welded joints has become more severe.

On the other hand, for welding materials, flux-cored wires for all-position welding are required from the viewpoint of high efficiency. There is also a demand for high fracture toughness for the resulting weld metal.
However, the conventional flux-cored wire for all-position welding has a high amount of oxygen in the obtained weld metal, so when gas shielded arc welding is performed using this, it is difficult to ensure the low temperature toughness of the welded joint. .

  Thus, for example, Patent Document 1 discloses a flux-cored wire that can be welded with high efficiency in all postures and is excellent in toughness.

JP-A-62-166098

However, the technique disclosed in Patent Document 1 does not have a high level of weld metal strength (Table 2 of Patent Document 1), and is currently required for structural materials in the marine structure field and the line pipe field. It is hard to say that Moreover, in patent document 1, the temperature of impact performance (toughness) evaluation is high (Table 2 of patent document 1), and the weld metal obtained by the technique disclosed in patent document 1 is excellent in low-temperature toughness. I can't judge.
In addition, the flux-cored wire is required not only to have welding workability, but also to obtain a weld metal having excellent 0.2% proof stress and hot cracking resistance and a small amount of diffusible hydrogen.

  Therefore, the present invention is excellent in welding workability in all posture welding including the vertical posture, and further has low temperature toughness, 0.2% proof stress, tensile strength, hot crack resistance and diffusible hydrogen content. It is an object of the present invention to provide a flux-cored wire for gas shielded arc welding from which a weld metal with a small amount can be obtained.

In order to solve the above problems, the present invention takes the following technical means.
The flux-cored wire for gas shielded arc welding according to the present invention is a flux-cored wire for gas shielded arc welding in which a steel sheath is filled with flux, and BaF ₂ : 2.0 mass% or more per total mass of the wire. 11.1 mass% or less, C: 0.01 mass% or more and 0.10 mass% or less, Si: 0.10 mass% or more and 1.50 mass% or less, Mn: 0.70 mass% or more and 3.50 mass% or less Hereinafter, Al: 0.45 mass% or more and less than 2.00 mass%, Mg: 0.10 mass% or more and 2.00 mass% or less, Ni: 0.50 mass% or more and 12.00 mass% or less, Zr: 0 .01 wt% to 1.00 wt% or less, Fe: 70.0 mass% or more 90.0% or less, Li: 0.01 mass% to 1.00 mass% or less, contains, of the BaF ₂ Content / (Content of Al + Previous Der value 2.1 to 20.0 following content) of Zr is, the total mass of the wire _per, CaF 2: 2.0 wt% or less, the metal oxide: 0.29 wt% or less, metal carbonates : 10.0 mass% or less, Cr: 1.00 mass% or less, Mo: 1.00 mass% or less, NaF: 1.00 mass% or less, Ca: 1.00 mass% or less, Ce and La: Total 0 300 mass% or less .

According to this flux-cored wire, the content of the predetermined component is within the predetermined range, and the value of BaF ₂ content / (Al content + Zr content) is within the predetermined range. Excellent weldability in all positions including welding, and weld metal with excellent low temperature toughness, 0.2% proof stress, tensile strength, and hot crack resistance of weld metal and low diffusible hydrogen content. Can be obtained.

According to this flux-cored wire, since the CaF ₂ content is not more than a predetermined value, the effect of improving welding workability can be ensured.

  According to this flux cored wire, since the content of the metal oxide is not more than a predetermined value, the excellent low temperature toughness of the weld metal can be ensured.

  According to this flux cored wire, since the content of the metal carbonate is not more than a predetermined value, the excellent low temperature toughness of the weld metal can be ensured.

  According to this flux cored wire, since the Cr and Mo contents are not more than the predetermined values, the excellent strength of the weld metal can be ensured.

  According to this flux-cored wire, since the content of NaF is not more than a predetermined value, the effect of improving welding workability can be ensured.

  According to this flux cored wire, since the Ca content is not more than a predetermined value, the effect of improving the welding workability can be ensured.

  According to this flux cored wire, since the total content of Ce and La is not more than a predetermined value, the excellent low temperature toughness of the weld metal can be ensured.

  The flux-cored wire for gas shielded arc welding according to the present invention is excellent in welding workability in all-position welding including a vertical posture, and further has low temperature toughness, 0.2% proof stress, tensile strength, and hot crack resistance. In addition, it is possible to obtain a weld metal having a low diffusible hydrogen content.

Hereinafter, embodiments for carrying out the present invention will be described in detail.
The flux-cored wire for gas shielded arc welding according to the present embodiment (hereinafter referred to as “wire” or “flux-cored wire” as appropriate) is a wire used for gas shielded arc welding, and the steel sheath is filled with flux. It has been done.

In detail, the wire which concerns on this embodiment consists of the steel outer shell which exhibits a cylindrical shape, and the flux with which the inner side of the steel outer shell is filled. Note that the wire may be either a seamless type without a seam in the steel outer shell or a seam type with a seam in the steel outer shell. Further, the wire may or may not be plated on the surface (outside of the steel skin).
In addition, although the wire diameter (diameter) of the wire which concerns on this embodiment is not specifically limited, What is necessary is just 1.2-2.4 mm. Further, the flux filling rate of the wire is not particularly limited, but may be 12 to 25% by mass of the total mass of the wire from the viewpoint of wire drawability and welding workability (feedability, etc.).

And the wire which concerns on this embodiment has specified the ratio of content of each component with respect to wire total mass (= steel outer shell mass + flux mass), and content of a predetermined component.
Hereinafter, the reason which specified content of each component of the wire which concerns on this embodiment is demonstrated.

[BaF ₂ : 2.0 mass% or more and 11.1 mass% or less]
BaF ₂ exhibits an effect as a strong deoxidizer and an effect as a slag-forming agent that improves welding workability in all-position welding. However, if the content of BaF ₂ is less than 2.0% by mass, the bead shape cannot be maintained in welding in a vertical posture, and the toughness deteriorates due to an increase in the amount of oxygen in the weld metal. On the other hand, when the content of BaF ₂ exceeds 11.1% by mass, the amount of diffusible hydrogen in the weld metal increases due to moisture absorption.
Therefore, the content of BaF ₂ is 2.0% by mass or more and 11.1% by mass or less per total mass of the wire.
In addition, the content of BaF ₂ is preferably 5.1% by mass or more, more preferably 6.0% by mass or more, from the viewpoint of further improving the above effects. Further, the content of BaF ₂ is preferably 10.0% by mass or less, more preferably 9.0% by mass or less, from the viewpoint of suppressing an increase in the amount of diffusible hydrogen.

[C: 0.01% by mass or more and 0.10% by mass or less]
C exhibits the effect of improving the strength of the weld metal. However, if the C content is less than 0.01% by mass, the yield strength and tensile strength of the weld metal will be insufficient. On the other hand, when the content of C exceeds 0.10% by mass, martensite is generated in an island shape in the weld metal and the toughness deteriorates. In addition, the strength of the weld metal becomes excessive and cracks are likely to occur.
Therefore, the C content is 0.01% by mass or more and 0.10% by mass or less per total mass of the wire.
In addition, the content of C is preferably 0.08% by mass or less from the viewpoint of suppressing toughness deterioration and cracking.

[Si: 0.10% by mass or more and 1.50% by mass or less]
Si exhibits an effect of promoting deoxidation of the weld metal. However, if the content of Si is less than 0.10% by mass, the deoxidizing effect is lost and blowholes are generated in the weld metal. On the other hand, when the Si content exceeds 1.50% by mass, the viscosity of the weld metal increases, and the familiarity with the base material deteriorates. In addition, oxide inclusions are formed in the weld metal and the toughness deteriorates.
Therefore, the Si content is 0.10% by mass or more and 1.50% by mass or less per total mass of the wire.
Note that the Si content is preferably 1.20% by mass or less from the viewpoint of suppressing deterioration in welding workability (suppressing deterioration of familiarity with the base material).

[Mn: 0.70% by mass or more and 3.50% by mass or less]
Mn promotes deoxidation of the weld metal and exhibits the effect of increasing the toughness of the weld metal. However, if the Mn content is less than 0.70 mass%, the deoxidation effect is insufficient, blowholes are generated in the weld metal, and the toughness is deteriorated. On the other hand, if the Mn content exceeds 3.50% by mass, the strength of the weld metal becomes excessive, cracks are likely to occur, and toughness deteriorates.
Therefore, the Mn content is 0.70% by mass or more and 3.50% by mass or less per the total mass of the wire.
In addition, the content of Mn is preferably 2.50% by mass or less from the viewpoint of suppressing generation of cracks and suppressing deterioration of toughness.

[Al: 0.45 mass% or more and less than 2.00 mass%]
Al exhibits the effect as a deoxidizer, adjusts the viscosity of molten BaF ₂ which is the main component of slag, and exhibits the effect of adjusting the bead shape in welding in a vertical posture. However, when the Al content is less than 0.45% by mass, the viscosity of the molten slag decreases, and the weld metal sags during welding in a vertical posture. In addition, when the Al ₂ O ₃ phase in the solidified slag is reduced, the slag is easily broken and the slag peelability is deteriorated. On the other hand, when the Al content is 2.00% by mass or more, coarse oxide inclusions are formed in the weld metal, and the toughness deteriorates.
Therefore, the Al content is 0.45% by mass or more and less than 2.00% by mass with respect to the total mass of the wire.
The Al content is preferably 0.70% by mass or more from the viewpoint of suppressing a decrease in welding workability. The content of Al is preferably 1.80% by mass or less from the viewpoint of suppressing toughness deterioration.

[Mg: 0.10% by mass to 2.00% by mass]
Mg exhibits an effect of promoting deoxidation of the weld metal. However, if the Mg content is less than 0.10% by mass, the deoxidation effect is insufficient, blowholes are generated in the weld metal, and the toughness is deteriorated. On the other hand, if the Mg content exceeds 2.00% by mass, the solidification temperature of the molten slag is lowered, and welding workability is deteriorated in welding in a vertical posture.
Therefore, the Mg content is 0.10% by mass or more and 2.00% by mass or less per the total mass of the wire.
In addition, the content of Mg is preferably 0.50% by mass or more from the viewpoint of suppressing deterioration of toughness. Further, the content of Mg is preferably 1.70% by mass or less from the viewpoint of suppressing a decrease in welding workability.

[Ni: 0.50% by mass or more and 12.00% by mass or less]
Ni exhibits the effect of improving the toughness of the weld metal. However, if the Ni content is less than 0.50 mass%, the toughness of the weld metal becomes insufficient. On the other hand, if the Ni content exceeds 12.00% by mass, the possibility of hot cracking of the weld metal increases.
Therefore, the Ni content is 0.50 mass% or more and 12.00 mass% or less per the total mass of the wire.
The Ni content is preferably 1.00% by mass or more, more preferably 2.00% by mass or more, from the viewpoint of suppressing deterioration of toughness. Further, the content of Ni is preferably 9.00 mass% or less, more preferably 5.00 mass% or less, from the viewpoint of suppressing the occurrence of hot cracking.

[Zr: 0.01% by mass or more and 1.00% by mass or less]
Zr exhibits the effect as a deoxidizer, adjusts the viscosity of molten BaF ₂ which is the main component of slag, and exhibits the effect of adjusting the bead shape in welding in a vertical position. However, if the content of Zr is less than 0.01% by mass, the viscosity of the molten slag is lowered, and welding metal sag occurs during welding in a vertical posture. On the other hand, when the content of Zr exceeds 1.00% by mass, it melts into the weld metal and remarkably increases the yield strength and tensile strength of the molten metal by solid solution strengthening. As a result, the toughness of the weld metal is degraded.
Therefore, the Zr content is 0.01% by mass or more and 1.00% by mass or less per total mass of the wire.
The Zr content is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, from the viewpoint of suppressing a decrease in welding workability. Further, the content of Zr is preferably 0.90% by mass or less, more preferably 0.80% by mass or less, from the viewpoint of suppressing toughness deterioration.

[Fe: 70.0 mass% or more and 90.0 mass% or less]
Fe is a main component of the wire. And when the Fe content is less than 70.0% by mass, the welding amount is insufficient. On the other hand, if the Fe content exceeds 90.0% by mass, the relative amount of slag becomes insufficient, and the bead shape becomes convex during welding in a standing posture and deterioration of toughness due to insufficient deoxidation.
Therefore, the Fe content is 70.0% by mass or more and 90.0% by mass or less per the total mass of the wire.

[Li: 0.01% by mass or more and 1.00% by mass or less]
Li exhibits the effect of improving the toughness of the weld metal. However, if the Li content is less than 0.01% by mass, excessive residual of Al and Zr in the weld metal is caused, and the proof stress and tensile strength of the weld metal are remarkably increased. As a result, the toughness of the weld metal is degraded. On the other hand, if the Li content exceeds 1.00% by mass, the arc becomes unstable and poor fusion occurs.
Therefore, the Li content is 0.01% by mass or more and 1.00% by mass or less per total mass of the wire.
The Li content is preferably 0.80% by mass or less, more preferably 0.50% by mass or less, from the viewpoint of suppressing the occurrence of poor fusion.

[BaF ₂ content / (Al content + Zr content): 2.1 to 20.0]
In the wire according to the present embodiment, the ratio of the content of BaF ₂ to the total content of Al and Zr (= the content of BaF ₂ / (the content of Al + the content of Zr)) is within a predetermined range. It is characterized by doing.
As described above, BaF ₂ exhibits an effect as a powerful deoxidizer, and also exhibits an effect as a slagging agent that makes welding workability excellent in all-position welding. While exhibiting the effect as a deoxidizer, the viscosity of molten BaF ₂ which is the main component of the slag is adjusted, and the effect of adjusting the bead shape in welding in a standing posture is exhibited.
And by making the ratio of these content into a predetermined range, the effect which adjusts a bead shape to a desirable state is exhibited in welding in a standing posture. However, when this ratio is less than 2.1, the volume of the molten slag is small, and a bead shape cannot be ensured in welding in a vertical posture. In addition, the oxygen content of the weld metal increases and the toughness deteriorates. On the other hand, when this ratio exceeds 20.0, the viscosity of the molten BaF ₂ which is the main component of the slag decreases, and the bead shape becomes convex in welding in the vertical posture. In addition, the volume of slag becomes excessive and slag entrainment occurs.
Therefore, the value of BaF ₂ content / (Al content + Zr content) is 2.1 or more and 20.0 or less.
This ratio is preferably 6.0 or more, more preferably 7.0 or more, from the viewpoint of preventing toughness deterioration. Further, this ratio is preferably 15.0 or less, more preferably 10.0 or less, from the viewpoint of suppressing a decrease in welding workability.

  So far, the essential components of the wire according to the present embodiment have been described, but in the following, the component that should be suppressed from being contained in the wire, the optional component that may be contained in the wire when further effects are desired, and Inevitable impurities will be described.

[CaF ₂ : 2.0% by mass or less]
CaF ₂ is a component that should be suppressed from being contained in the wire, and the content of CaF ₂ is preferably lower (may be 0% by mass). When the content of CaF ₂ is more than 2.0 wt%, to reduce the viscosity of the molten slag, it is difficult to weld at vertical position.
Therefore, if the CaF ₂ contains a wire, the content of CaF ₂ is more than 2.0 wt% based on the total mass of the wire.

[Metal oxide: 0.29 mass% or less]
The metal oxide is a component that should be suppressed from being contained in the wire, and the metal oxide content is preferably low (may be 0% by mass). And when content of a metal oxide exceeds 0.29 mass%, this metal oxide will remain and disperse | distribute in a molten metal, and the low temperature toughness of a weld metal will deteriorate.
Accordingly, when the metal oxide is contained in the wire, the content of the metal oxide is 0.29% by mass or less per the total mass of the wire.
The metal oxide is specifically one or more of Al ₂ O ₃ , Fe ₂ O ₃ , SiO ₂ , and TiO ₂ , and the content of the metal oxide refers to each of the listed components. Total content.

[Metal carbonate: 10.0% by mass or less]
The metal carbonate is a component that should be suppressed from being contained in the wire, and the metal carbonate is preferably as low as possible (may be 0% by mass). And when content of metal carbonate exceeds 10.0 mass%, the raise of the oxygen content in a weld metal will be caused, and toughness will deteriorate. In addition, the generation of excess gas reduces arc stability and causes poor fusion.
Therefore, when the metal carbonate is contained in the wire, the content of the metal carbonate is 10.0% by mass or less per the total mass of the wire.
The metal carbonate is specifically one or more of CaCO ₃ and BaCO ₃ , and the content of the metal carbonate is the total content of the listed components.

[Cr: 1.00 mass% or less, Mo: 1.00 mass% or less]
Neither Cr nor Mo is an essential component, but when at least one of them is contained in the wire, the effect of improving the tensile strength of the weld metal is exhibited. However, when the Cr content exceeds 1.00% by mass or the Mo content exceeds 1.00% by mass, the strength of the weld metal becomes excessive and the possibility of cracking increases. In addition, the toughness of the weld metal deteriorates.
Therefore, when Cr and Mo are contained in the wire, at least one of Cr: 1.00% by mass or less and Mo: 1.00% by mass or less may be contained.
In addition, the content of Cr and Mo is preferably 0.30% by mass or less from the viewpoint of suppressing the tensile strength from being excessive and from the viewpoint of suppressing the deterioration of toughness. Further, the contents of Cr and Mo are each preferably 0.01% by mass or more, and more preferably 0.05% by mass or more, from the viewpoint of further improving the above effects.

[NaF: 1.00% by mass or less]
NaF is not an essential component, but exhibits an effect of improving welding workability by being contained in the wire. However, when the content of NaF exceeds 1.00% by mass, the amount of diffusible hydrogen in the weld metal increases due to moisture absorption.
Therefore, when NaF is contained in the wire, the content of NaF is 1.00% by mass or less.
In addition, the content of NaF is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, from the viewpoint of further improving the effect.

[Ca: 1.00% by mass or less]
Ca is not an essential component, but exhibits an effect of improving welding workability by being contained in the wire. However, if the Ca content exceeds 1.00% by mass, it is added to the molten slag as Ca oxide, the viscosity of the slag is lowered, and dripping of the molten metal occurs during welding in a vertical posture.
Therefore, when Ca contains in a wire, content of Ca is 1.00 mass% or less.
The Ca content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, from the viewpoint of further improving the above effect.

[Ce and La: total 0.300 mass% or less]
Ce and La are not essential components, but exhibit the effect of improving toughness by being contained in the wire. However, if the total content of Ce and La exceeds 0.300% by mass, these components are oxidized to cause moisture adsorption and increase the amount of diffusible hydrogen in the weld metal.
Therefore, when Ce and La are contained in the wire, the total content of Ce and La is 0.300% by mass or less.
The total content of Ce and La is preferably 0.100% by mass or less from the viewpoint of suppressing an increase in the amount of diffusible hydrogen. Further, the total content of Ce and La is preferably 0.010% by mass or more from the viewpoint of further improving the effect.

[Balance: inevitable impurities]
The balance in the component composition of the wire according to the present embodiment is inevitable impurities. And as an unavoidable impurity, P, S, Nb, V, Sb, Bi, B, etc. may contain in the range which does not prevent the effect of this invention. Specifically, P: 0.030 mass% or less, S: 0.030 mass% or less, Nb: 0.30 mass% or less, V: 0.30 mass% or less, Sb: 0.030 mass% or less, Bi : 0.0050 mass% or less, B: 0.0050 mass% or less.
Further, the balance may contain an alloying agent such as Ti, Cu, Nb, V, Bi, B and the compound thereof, and an arc stabilizer and a slag forming agent as long as the effects of the present invention are not hindered. Good. In addition, when each component other than the above-described metal oxide and metal carbonate is added as an oxide or nitride, the balance of the wire according to the present embodiment includes N as well as O.
In addition, about P, S, Nb, V, Sb, Bi, B etc. which were illustrated as an unavoidable impurity, if not exceeding the above-mentioned predetermined content, not only when it is contained as an unavoidable impurity, it is positive Even if it is a case where it adds to, the effect of this invention is not prevented.
In addition, CaF ₂ , metal oxides, metal carbonates, Cr, Mo, NaF, Ca, Ce, and La that define only the upper limit described above may be positively added, but as inevitable impurities It may be included.

Although described components of the wire according to the present embodiment, the content of Al, Al derived from _Al 2 _{O 3} is not included, the content of Fe, Fe derived from _Fe 2 _{O 3} is Not included, Si contained in SiO ₂ is not contained, Si contained in C ₂ is not contained, C derived from metal carbonate is not contained, and Ca contents are CaCO ₃ and CaF _2. Ca derived from is not included.

Next, the manufacturing method of the wire which concerns on this embodiment is demonstrated.
[Wire production method]
Although it does not specifically limit as a manufacturing method of the wire which concerns on this embodiment, For example, it can manufacture with the method shown below.
First, a steel strip constituting a steel outer shell is prepared, and this steel strip is formed by a forming roll while being sent in the longitudinal direction to form a U-shaped open tube. Next, the steel outer shell is filled with a flux containing each component so as to have a predetermined chemical composition, and then processed so as to have a circular cross section. Thereafter, the wire is drawn by cold working to obtain a flux-cored wire having a wire diameter of 1.2 to 2.4 mm, for example. In addition, you may anneal in the middle of cold processing. Further, any structure of a seamless wire in which a seam of a steel outer shell formed in the manufacturing process is welded and a wire that does not weld the seam and remains in a gap can be adopted.

Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention.
In the present example, in accordance with the manufacturing method described above, the tubular outer shell formed of carbon steel having a component composition in the range shown in Table 1 below is filled with flux, and the flux-cored wire (diameter of the example and the comparative example) 1.6 mm). In addition, the remainder of the outer skin component shown in the following Table 1 is Fe and inevitable impurities. At that time, the filling rate of the flux was set in the range of 17.0 to 22.0% by mass with respect to the total mass of the wire.

Tables 2 to 4 below show the component compositions of the whole wires of the examples and comparative examples. In addition, the remainder of the wire component shown to the following Tables 2-4 is an unavoidable impurity.
In Tables 2 to 4, “BaF ₂ / (Al + Zr)” means “BaF ₂ content / (Al content + Zr content)”. In Tables 2 to 4, “Ce or La” means “total content of Ce and La”.
Moreover, in Tables 2-4, about what does not satisfy | fill the scope of the present invention, the numerical value is underlined.

  Next, gas shielded arc welding was performed on the base materials shown in Table 5 below using the flux-cored wires of Examples and Comparative Examples. The balance of the matrix composition shown in Table 5 below is Fe and inevitable impurities.

The welding conditions are as follows.
・ Shielding gas: 100 volume% CO ₂ , 25 liters / minute ・ Wire diameter: φ1.6 mm
-Groove shape: 20 °
・ Route interval: 16mm
・ Welding current: 260A
・ Arc voltage: 26V
-Welding posture: downward-Welding speed: 250 mm / min-Weld heat input: 1.8 kJ / mm
・ Welding length: 400mm
-Preheating temperature: 100-110 ° C
-Interpass temperature: 140-160 ° C
・ Polarity: DC negative (DCEN)

  And about the weld metal obtained by gas shielded arc welding using each flux cored wire of an example and a comparative example, it is a mechanical property (low-temperature toughness, 0.2% yield strength, tensile strength) by the method shown below. The amount of diffusible hydrogen, hot cracking resistance, poor fusion, and the occurrence of blowholes were evaluated.

<Mechanical properties>
The mechanical properties of the weld metal were evaluated by a tensile test and an impact test in accordance with “Method of tensile and impact test for weld metal” defined in JIS Z 3111: 2005. As a result, for low temperature toughness, an impact value (CVN-80) at −80 ° C. of 100 J or more was accepted. Moreover, the 0.2% proof stress (0.2% PS) was 690 MPa or more as a pass. Furthermore, what was in the range of 770 MPa or more and 930 MPa or less of the tensile strength (TS) was set as the pass.

<Diffusion hydrogen content>
The amount of diffusible hydrogen in the weld metal was evaluated by a method based on JIS Z 3118: 2007.
As a result, a diffusible hydrogen amount ([H] _d ) of 8.0 mL / 100 g or less was accepted.

<Hot-cracking resistance, poor fusion, blowhole>
The evaluation of hot cracking resistance and poor fusion was performed based on the “radiation transmission test method for steel welded rope” defined in JIS Z 3104: 1995.
After welding, X-ray transmission test confirms poor fusion, hot cracks, and blowholes in the weld (welding length: 400 mm, excluding crater), and measures the total length of these parts did. And, the value calculated by (total fusion portion, hot cracking, blowhole occurrence length) / welded portion length × 100 is 0% when over 0% and over 5% when Δ, The case of exceeding 5% was evaluated as x, and the case of x was evaluated as being impossible to perform welding. And the thing of (circle) and (triangle | delta) was set as the pass.

Moreover, about each flux-cored wire of an Example and a comparative example, welding workability | operativity was evaluated by the method shown below.
<Welding workability>
Welding workability was evaluated based on the familiarity between the base material and the bead and the cross-sectional shape of the bead, by performing vertical welding for the base material shown in Table 5 using an automatic welding apparatus. As a result, the case where vertical welding is possible and the bead surface after welding is smooth, ◯, the case where vertical welding is possible but unevenness occurs on the bead surface after welding, slag or melting The case where the metal dripped down and welding could not be performed, or the case where the bead surface was greatly concave due to insufficient welding amount was marked as x. And the thing of (circle) and (triangle | delta) was set as the pass.
In addition, slag peelability was also evaluated.
For slag peelability, the boundary between the slag and the base metal (welding length: 400 mm) was struck once with an air chipper (FCH-20, air pressure: 0.5 MPa) and the length of the struck part When the slag having a length of 70% or more with respect to the thickness is peeled, ◯ when the slag having a length of 50% or more and less than 70% is peeled Δ, when the slag having a length of less than 50% is peeled It was set as x, and when x, it was evaluated that welding could not be performed. And the thing of (circle) and (triangle | delta) was set as the pass.

In addition, the detailed welding conditions at the time of evaluating welding workability are as follows.
-Base material: Base material shown in Table 5-Welding current: 220A
・ Arc voltage: 24V
-Welding speed: 110 mm / min-Overhang length: 20 mm
・ Weaving width: 5mm
-Automatic welding equipment: Kobe Steel, PICOMAX-2Z

  The above results are shown in Tables 6 to 8 below. In Tables 6 to 8, those that do not satisfy the evaluation criteria are indicated by underlining the numerical values.

  As shown in Tables 6 and 7, No. 1 satisfying the invention-specific matters of the present invention. 1-51 was favorable in all the evaluation items.

  On the other hand, as shown in Table 8, no. Since 52-81 did not satisfy the invention specific matter of this invention, it resulted in it being a defect in any evaluation item. The details are as follows.

No. 52, the content of BaF ₂ is less than the lower limit value, and the ratio (= the content of BaF ₂ / (the content of Al + the content of Zr)) is less than the lower limit value, so the toughness deteriorates. At the same time, it was not possible to perform fillet welding to improve the standing.
No. 53 had a large amount of diffusible hydrogen because the content of BaF ₂ exceeded the upper limit.
No. In No. 54, the C content was less than the lower limit value, so the values of proof stress and tensile strength were low.
No. In No. 55, since the C content exceeded the upper limit, the strength became excessive and the toughness deteriorated.
No. No. 56 had blowholes because the Si content was less than the lower limit.
No. In No. 57, since the Si content exceeded the upper limit, the bead shape was poor, the welding workability was inferior, and the toughness deteriorated.

No. In No. 58, since the Mn content was less than the lower limit, blowholes were generated and toughness deteriorated.
No. In No. 59, since the Mn content exceeded the upper limit, the strength became excessive and the toughness deteriorated.
No. In No. 60, since the Al content was less than the lower limit, the bead shape was poor, the welding workability was inferior, and the slag peelability was also deteriorated.
No. In No. 61, since the Al content exceeded the upper limit, the bead shape became slightly convex, and the toughness deteriorated.
No. In No. 62, the Mg content was less than the lower limit, so the toughness deteriorated and blowholes were generated.
No. In No. 63, since the Mg content exceeded the upper limit value, welding could not be performed due to dripping of the weld metal in the fillet welding of the vertical improvement.

No. In No. 64, the toughness deteriorated because the Ni content was less than the lower limit.
No. In No. 65, since the Ni content exceeded the upper limit, hot cracking occurred.
No. In No. 66, since the Zr content was less than the lower limit value, welding metal could not be welded due to drooping of the weld metal in the case of fillet welding with an improved vertical.
No. In No. 67, since the Zr content exceeded the upper limit, the bead shape was slightly convex, the strength was excessive, and the toughness deteriorated.
No. In No. 68, since the Fe content was less than the lower limit, the welding amount was insufficient, and the bead shape became concave.
No. In No. 69, since the Fe content exceeded the upper limit, the toughness deteriorated, and it was not possible to perform the fillet welding to improve the standing.

No. In No. 70, since the Li content was less than the lower limit, the strength became excessive and the toughness deteriorated.
No. No. 71 was poorly fused because the Li content exceeded the upper limit.
No. No. 72 had a ratio (= BaF ₂ content / (Al content + Zr content) value) less than the lower limit, so that the bead shape was poor and the welding workability was poor, and the toughness deteriorated.
No. 73, since the ratio (= BaF ₂ content / (Al content + Zr content) value) exceeded the upper limit, slag entrainment occurred, resulting in poor fusion and a bead shape. It became convex.

No. In No. 74, the content of CaF ₂ exceeded the upper limit value, so that it was not possible to perform the fillet welding with an improved vertical rise.
No. In No. 75, the toughness deteriorated because the metal oxide content exceeded the upper limit.
No. In No. 76, the content of metal carbonate exceeded the upper limit value, so that the toughness deteriorated and the fusion was poor.

No. In No. 77, since the Cr content exceeded the upper limit, the strength became excessive and the toughness deteriorated.
No. In No. 78, since the Mo content exceeded the upper limit, the strength became excessive and the toughness deteriorated.
No. In No. 79, the amount of diffusible hydrogen increased because the NaF content exceeded the upper limit.

No. In No. 80, since the Ca content exceeded the upper limit value, it was difficult to perform fillet welding with a rapid improvement.
No. No. 81 had a large amount of diffusible hydrogen because the total content of Ce and La exceeded the upper limit.

  The present invention has been described in detail with reference to the embodiments and examples. However, the gist of the present invention is not limited to the above-described contents, and the scope of right is widely interpreted based on the description of the claims. Must. Needless to say, the contents of the present invention can be widely modified and changed based on the above description.

Claims (1)

A flux-cored wire for gas shielded arc welding in which a flux is filled in a steel outer sheath,
Per total wire mass,
BaF ₂ : 2.0 mass% or more and 11.1 mass% or less C: 0.01 mass% or more and 0.10 mass% or less Si: 0.10 mass% or more and 1.50 mass% or less Mn: 0.70 mass% More than 3.50 mass% Al: 0.45 mass% or more and less than 2.00 mass% Mg: 0.10 mass% or more and 2.00 mass% or less Ni: 0.50 mass% or more and 12.00 mass% or less Zr : 0.01 mass% or more and 1.00 mass% or less Fe: 70.0 mass% or more and 90.0 mass% or less Li: 0.01 mass% or more and 1.00 mass% or less
Value 2.1 to 20.0 der following the BaF ₂ content / (the content of the content + the Zr of said Al) is,
Based on the total mass of the wire, CaF ₂ : 2.0 mass% or less, metal oxide: 0.29 mass% or less, metal carbonate: 10.0 mass% or less, Cr: 1.00 mass% or less, Mo: 1 0.0000 mass% or less, NaF: 1.00 mass% or less, Ca: 1.00 mass% or less, and Ce and La: 0.300 mass% or less in total, containing flux for gas shielded arc welding Wire.