JP5400461B2 - Flux cored wire - Google Patents

Description

  The present invention relates to a flux-cored wire applied to gas shielded arc welding of a steel plate made of mild steel, high-tensile steel, or the like.

Conventionally, a flux-cored wire applied to gas shielded arc welding of a steel sheet has been proposed with the following configuration. For example, in Patent Document 1, a predetermined amount of TiO ₂ , SiO ₂ , ZrO ₂ , CaO, Na ₂ O, K ₂ O, F, C, Si, Mn, Al, Mg in mass% with respect to the total mass of the wire. , P, S, B, contains Bi, the balance being Fe and unavoidable impurities, _{and, Na 2 O + K 2 O} , Mn / Si, Al + Mg flux-cored wire for gas shielded arc welding is a predetermined amount proposed Has been.

JP 2006-289404 A

However, since the wire described in Patent Document 1 does not contain Ti and the content of Mn is also small, there is a problem that high-temperature cracking occurs in the first-layer welded portion in single-sided butt joint welding of steel plates. There is. In addition, since the wire does not contain Al ₂ O ₃ , there is a problem that welding workability in all-position welding is inferior, such as poor bead shape in horizontal fillet welding or bead sagging in standing improvement welding. There is. Furthermore, since the amount of Mn and B of the wire is small, there is a problem that the mechanical properties (toughness) of the weld metal are inferior.

  The present invention has been made in view of the above problems, and an object thereof is to provide a flux-cored wire excellent in hot crack resistance, welding workability and mechanical properties of a weld metal.

In order to solve the above-mentioned problem, the flux-cored wire according to the present invention is a flux-cored wire in which a flux is filled in a steel outer sheath, and the flux filling rate with respect to the total mass of the wire is 10 to 25% by mass, C: 0.03 to 0.08% by mass with respect to the total mass of the wire, Si (total amount of Si calculated from all Si sources contained in the wire): 0.10 to 1.00% by mass, Mn (total amount of Mn calculated from all Mn sources contained in the wire): 2.4 to 3.7% by mass, Ti: 0.15 to 1.00% by mass, TiO ₂ : 5.0 to 8.0% by mass, Al: 0.20 to 0.50% by mass, Al ₂ O ₃ : 0.05 to 0.50% by mass, B: 0.003 to 0.020% by mass, the balance being Fe and inevitable impurities, and (4 × Ti + 10 × Al -3 satisfied × Si) ≧ 1.0 relational expression, in the relational expression (Ti) is Ti amount calculated only from the Ti of the Ti and the TiO ₂ are contained prior Symbol wire , (Al) is an Al amount calculated only from the Al of the Al and the Al ₂ O ₃ contained in the wire .

According to the above configuration, the flux filling rate with respect to the total mass of the wire is a predetermined amount, and a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al, Al ₂ O ₃ and B with respect to the total mass of the wire. By containing, spatter generation and fume generation are suppressed during welding, slag peelability is improved, mechanical properties of the welded joint (welded metal) are improved, and high temperature cracking in the first layer weld zone Is suppressed. Further, when the Ti amount, the Al amount, and the Si amount satisfy a predetermined relationship, that is, (4 × Ti + 10 × Al−3 × Si) ≧ 1.0, Ti is deoxidized during welding. It is possible to control the composition of inclusions generated in the weld metal to a Ti-based oxide composition effective for promoting nucleation. As a result, the solidification structure of the weld metal can be refined, and the action of suppressing hot cracking is improved.

According to the flux-cored wire of the present invention, the flux filling rate is a predetermined amount, contains a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al, Al ₂ O ₃ , and B, and flux The amount of Ti, Al, and Si contained in the cored wire satisfies the predetermined relationship, so that the high-temperature crack resistance in the first layer welded part of single-sided butt joint welding is excellent, and the welding workability in all-position welding (Including bead appearance) and weld metal mechanical properties are excellent. As a result, it is possible to provide a welded product with excellent quality.

(A)-(d) is sectional drawing which shows the structure of the flux cored wire which concerns on this invention. It is sectional drawing which shows the groove shape of the welding preform | base_material used for evaluation of hot cracking resistance.

The flux cored wire according to the present invention will be described in detail. Fig.1 (a)-(d) is sectional drawing which shows the structure of a flux cored wire.
As shown in FIGS. 1A to 1D, a flux-cored wire (hereinafter referred to as a wire) 1 includes a steel outer shell 2 formed in a cylindrical shape and a flux 3 filled in the cylinder. Become. Moreover, the wire 1 is a seamless type in which a flux 3 is filled in a seamless steel outer shell 2 as shown in FIG. 1 (a), and a seam 4 as shown in FIGS. 1 (b) to 1 (d). Any form of a seam type in which a flux 3 is filled in a cylinder of a steel outer shell 2 having a certain shape.

The wire 1 has a predetermined amount of flux filling and contains a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al, Al ₂ O ₃ and B, with the balance being Fe and inevitable impurities. And the amount of Ti, the amount of Al, and the amount of Si satisfy a predetermined relationship (specifically, (4 × Ti + 10 × Al−3 × Si) is a predetermined value or more).

Below, the numerical range of a wire component (flux filling rate and component amount) is described with the reason for limitation. The flux filling rate defines the mass of the flux 3 filled in the steel outer shell 2 as a ratio to the total mass of the wire 1 (steel outer sheath 2 + flux 3). The component amount is expressed as the sum of the component amounts in the steel outer sheath 2 and the flux 3, and the mass of each component contained in the wire 1 (steel outer sheath 2 + flux 3) is defined as a ratio to the total mass of the wire 1. . Of the components constituting the wire 1, C, Si, Mn, Ti, TiO ₂ , Al, Al ₂ O ₃ and B are not particularly limited whether they are added from the steel outer shell 2 or the flux 3. It should just be added to at least one of steel outer skin 2 and flux 3.

(Flux filling ratio: 10 to 25% by mass)
When the flux filling rate is less than 10% by mass, the arc stability is deteriorated, the amount of spatter generated is increased, and the welding workability is lowered. On the other hand, when the flux filling rate exceeds 25% by mass, the wire 1 is disconnected and the productivity is remarkably deteriorated.

(C: 0.03-0.08 mass%)
C is added to ensure the hardenability of the weld. When the amount of C is less than 0.03% by mass, the strength (tensile strength) and toughness (absorbed energy) of the welded portion are insufficient due to insufficient hardenability. Moreover, a hot crack occurs in the welded portion (first layer welded portion) due to the low C content. If the amount of C exceeds 0.08% by mass, the amount of spatter generated during fusing or the amount of fume generated increases and welding workability decreases. Moreover, when there is much C amount of the steel materials which are to-be-welded materials, C amount of a welding part (welded metal) will increase. And when C becomes the area | region which raise | generates a peritectic reaction, it will become easy to generate | occur | produce a high temperature crack in a welding part (first layer welding part). As the C source, for example, steel outer skin, alloy powder such as Fe-Mn, iron powder, or the like is used.

(Si: 0.10 to 1.00% by mass)
Si is added to ensure the ductility of the weld and maintain the bead shape. When the amount of Si is less than 0.10% by mass, the ductility (elongation) of the weld is insufficient. In addition, the bead shape is deteriorated. In particular, the bead hangs down in the vertical improvement welding, and the welding workability is lowered. When the amount of Si exceeds 1.00% by mass, hot cracking occurs in the welded part (first layer welded part). Here, the Si amount is the sum of the Si amounts calculated from all the Si sources contained in the wire 1. As the Si source, for example, a steel outer shell, an alloy such as Fe—Si or Fe—Si—Mn, a fluoride such as K ₂ SiF ₆ , an oxide such as zircon sand, silica sand, or feldspar is used.

(Mn: 2.4 to 3.7% by mass)
Mn is added to ensure the hardenability of the weld. If the amount of Mn is less than 2.4% by mass, the hardenability of the welded portion is insufficient and the toughness is lowered. Moreover, since the amount of MnS obtained by combining with S contained as an unavoidable impurity is also reduced, the action of suppressing high-temperature cracking by MnS is reduced, and high-temperature cracking occurs in the welded portion (first layer welded portion). If the amount of Mn exceeds 3.7% by mass, the strength of the weld becomes excessive and the toughness becomes insufficient. In addition, cold cracks occur in the weld. Here, the amount of Mn is the total amount of Mn calculated from all the Mn sources contained in the wire 1. As the Mn source, for example, an alloy such as a steel outer shell, Mn metal powder, Fe—Mn, Fe—Si—Mn, or the like is used.

(Ti: 0.15-1.00 mass%, preferably 0.20-1.00 mass%)
Ti (metal Ti) is added in order to improve the hot crack resistance of the weld zone (first layer weld zone). Ti (metal Ti) contributes to the deoxidation reaction during welding, and inclusions in the weld metal can be controlled to a Ti-based oxide composition. As a result, the solidification structure of the weld (weld metal) can be made fine, and the weld The effect of suppressing the high temperature cracking of the (first layer weld) is improved. If the amount of Ti (metal Ti) is less than 0.15% by mass, hot cracking occurs in the welded portion (first layer welded portion). When the amount of Ti (metal Ti) exceeds 1.00% by mass, the weld metal reheated portion tends to be hard and brittle bainite and martensite, and the toughness decreases. In addition, the amount of spatter generated during welding increases and welding workability decreases. As the Ti source, for example, an alloy powder such as a steel outer shell or Fe—Ti is used.

_(TiO 2: 5.0 to 8.0 wt%)
TiO ₂ (Ti oxide) is added to ensure all-position weldability. When the amount of TiO ₂ (Ti oxide) is less than 5.0% by mass, the bead drips during the vertical improvement welding, and the workability of welding is lowered. When the amount of TiO ₂ (Ti oxide) exceeds 8.0% by mass, the slag removability at the time of welding deteriorates and the welding workability decreases. Further, the bulk specific gravity of the flux 3 is reduced, and the productivity is deteriorated. As the TiO ₂ source, for example, rutile or the like is used.

(Al: 0.20 to 0.50 mass%, preferably 0.20 to 0.40 mass%)
Al is a strong deoxidizer, and it reduces SiO ₂ made of Si, which has a weaker deoxidation power than Al, from inclusions formed in welded joints (welded metal), and the composition of inclusions is effective in promoting nucleation. It is possible to control the inclusion of a typical Ti-based oxide composition. As a result, the solidification structure of the weld metal can be made fine. Furthermore, the oxygen content of the weld metal is reduced, the yield of Mn is stabilized, the hot cracking suppressing action of the welded part (first layer welded part) is improved, and the toughness is also stabilized. When the amount of Al is less than 0.20% by mass, deoxidation is not sufficient, and hot cracking occurs in the welded portion (first layer welded portion). Also, toughness is reduced. If the Al amount exceeds 0.50% by mass, the amount of spatter generated during welding increases and welding workability decreases. As the Al source, for example, steel outer sheath, Al metal powder, Fe-Al, Al-Mg alloy powder or the like is used.

_(Al 2 _O 3: 0.05~0.50 wt%, preferably from 0.05 to 0.40 wt%)
Al ₂ O ₃ is added to prevent the bead from drooping in the horizontal fillet posture and in the standing improvement posture. If the amount of Al ₂ O ₃ is less than 0.05% by mass, the bead shape (familiarity) in horizontal fillet welding is poor, and bead sagging occurs in vertical improvement welding, resulting in poor welding workability. When the amount of Al ₂ O ₃ exceeds 0.50% by mass, the slag removability at the time of welding is deteriorated and the welding workability is lowered. As the Al ₂ O ₃ source, for example, a complex oxide such as alumina or feldspar is used.

(B: 0.003-0.020 mass%)
Among B, dissolved B segregates at the γ grain boundary and has the effect of suppressing the formation of proeutectoid ferrite, which is effective in improving the toughness of the weld metal. When the amount of B is less than 0.003 mass%, most of B is fixed to nitride as BN, there is no effect of suppressing the formation of proeutectoid ferrite, and the effect of improving toughness cannot be obtained. If the amount of B exceeds 0.020% by mass, hot cracking of the weld metal tends to occur. As the B source, for example, an alloy such as Fe-B or atomized B is used.

((4 × Ti + 10 × Al-3 × Si) ≧ 1.0)
By controlling the amount of Ti (metal Ti) contained in the wire 1 within a predetermined range, Ti (metal Ti) contributes to the deoxidation reaction during welding, and the composition of inclusions generated in the welded joint (welded metal) Can be controlled to be inclusions of a Ti-based oxide composition effective for promoting nucleation. As a result, the solidification structure of the weld metal can be made fine, and the hot cracking suppressing effect can be remarkably improved. Further, it is preferable that the Ti-based oxide effective for promoting nucleation does not contain SiO ₂ that lowers the melting point of inclusions. Furthermore, Al is a strong deoxidizer, which reduces SiO ₂ composed of Si, which has a weaker deoxidizing power than Al, and controls the inclusion composition to be an inclusion of a Ti-based oxide composition that is effective in promoting nucleation. There is an effect to. Therefore, by defining the relationship between the amount of Ti contained in the wire 1 (metal Ti), the amount of Al, and the amount of Si, the Ti-based oxide composition can be controlled to an effective composition by refining the solidified structure, and the weld metal It becomes possible to control the solidified structure to be preferable in improving the hot cracking suppression effect.

If (4 × Ti + 10 × Al−3 × Si) <1.0, the solidified structure of the welded joint is not refined. Therefore, (4 × Ti + 10 × Al−3 × Si) ≧ 1.0.
Here, (Ti) is a Ti amount calculated only from the Ti (metal Ti) of the Ti and the TiO ₂ contained in the wire 1, and the TiO ₂ (Ti oxidation) contained in the wire 1. The amount of Ti calculated (converted) from the product) is not included.
Further, (Si) is the total amount of Si calculated from all the Si sources contained in the wire 1. The SiO ₂ is used as an Si source, for example, oxides such as zircon sand, silica sand, and feldspar.

(Fe)
The remaining Fe corresponds to Fe constituting the steel outer shell 2 and / or Fe of alloy powder or alloy powder added to the flux 3.
(Inevitable impurities)
The remaining inevitable impurities include S, P, Ni, O, Zr and the like, and it is allowed to be contained within a range that does not hinder the effects of the present invention. The amount of S, amount of P, amount of Ni, amount of O, and amount of Zr are each preferably 0.050% by mass or less, and are the total amount of each component in the steel outer sheath 2 and the flux 3.

In addition, as for the steel outer sheath 2 and the flux 3, each component (each component amount) of the steel outer sheath 2 and the flux 3 is selected so that the wire component (component amount) is within the above range at the time of wire production.
Moreover, it is also possible to give Cu plating to the surface of the wire 1, and you may contain 0.35 mass% or less Cu with respect to the total mass of a wire.

The flux-cored wire according to the present invention will be specifically described by comparing an example that satisfies the requirements of the present invention with a comparative example that does not satisfy the requirements of the present invention.
Steel outer shell (steel contains C: 0.03 mass%, Si: 0.02 mass%, Mn: 0.25 mass%, P: 0.010 mass%, S: 0.007 mass%, Wire 1 shown in FIG. 1 (b) having a wire diameter of 1.2 mm made of wire components shown in Tables 1 and 2 is filled inside with a flux inside the balance Fe and unavoidable impurities). : No. 1 to 19, Comparative Example: No. 20 to 40).

The wire component was measured and calculated by the following measurement method.
The amount of C was measured by the “infrared absorption method”. The amount of Si, the amount of Mn, and the amount of B were measured by “ICP emission spectroscopic analysis” after dissolving the entire amount of wire.

The amount of TiO ₂ (present as TiO ₂ or the like but not including Fe—Ti or the like) is measured by the “acid decomposition method”. As a solvent used in the acid decomposition method, aqua regia was used, and the entire amount of the wire was dissolved. Thus, although Ti source contained in the wire 1 (Fe-Ti, etc.) is dissolved in aqua regia, TiO ₂ source (TiO _2, etc.) because it insoluble in aqua regia, melt remains. This solution was filtered using a filter (the filter paper has a fineness of 5C). The residue together with the filter was transferred to a nickel crucible and heated with a gas burner to be incinerated. Next, an alkali flux (mixture of sodium hydroxide and sodium peroxide) was added and heated again with a gas burner to melt the residue. Next, 18 mass% hydrochloric acid was added to make the melt into a solution, and then the solution was transferred to a volumetric flask and further diluted with pure water to obtain an analysis solution. The Ti concentration in the analysis solution was measured by “ICP emission spectroscopy”. And converting the Ti concentration in the TiO ₂ amount was calculated amount of TiO _2.

Ti amount (existing as Fe-Ti etc., not including TiO ₂ etc.) is obtained by dissolving the whole amount of wire in aqua regia by “acid decomposition method” and filtering the insoluble TiO ₂ source (TiO ₂ etc.). Then, by using the solution as a Ti source (Fe—Ti or the like) contained in the wire 1, the presence of the Ti amount (Fe—Ti or the like) was determined using “ICP emission spectroscopy”.

The amount of Al ₂ O ₃ (present as a composite oxide such as alumina and feldspar, and does not include alloy powder such as Al metal powder) is measured by the “acid decomposition method”. As a solvent used in the acid decomposition method, aqua regia was used, and the entire amount of the wire was dissolved. As a result, the Al source (alloy powder such as Al metal powder) contained in the wire 1 is dissolved in aqua regia, but the Al ₂ O ₃ source (a composite oxide such as alumina and feldspar) is insoluble in aqua regia. , It remains undissolved. This solution was filtered using a filter (the filter paper has a fineness of 5C). The residue together with the filter was transferred to a nickel crucible and heated with a gas burner to be incinerated. Next, an alkali flux (mixture of sodium hydroxide and sodium peroxide) was added and heated again with a gas burner to melt the residue. Next, 18 mass% hydrochloric acid was added to make the melt into a solution, and then the solution was transferred to a volumetric flask and further diluted with pure water to obtain an analysis solution. The Al concentration in the analysis solution was measured by “ICP emission spectroscopy”. And converting the Al concentration in _the amount of _Al 2 _{O 3,} it was calculated _the amount of _Al 2 _{O 3.}

(Present as an alloy powder such as Al metal powder, composite oxide of alumina and feldspar and the like are not included) Al amount, by dissolving the wire the total amount to aqua regia by "acid decomposition method", Al ₂ was insoluble By filtering the O ₃ source (composite oxide such as alumina and feldspar) and using the solution as the Al source (alloy powder such as Al metal powder) contained in the wire 1, the “ICP emission spectroscopy” is used. The presence of Al was determined as an Al amount (alloy powder such as Al metal powder).

  Using the produced wire 1, hot crack resistance, mechanical properties (tensile strength, absorbed energy), and welding workability were evaluated by the following methods. Based on the evaluation result, comprehensive evaluation of the wire 1 of an Example and a comparative example was performed.

(High temperature crack resistance)
JIS G3106 SM400B steel (C: 0.12% by mass, Si: 0.2% by mass, Mn: 1.1% by mass, P: 0.008% by mass, S: 0.003% by mass, balance Fe And a welding base material composed of unavoidable impurities) was subjected to single-sided welding (downward butt welding) under the welding conditions shown in Table 3.

  FIG. 2 is a cross-sectional view showing a groove shape of a weld base material used for evaluation of hot crack resistance. As shown in FIG. 2, the welding base material 11 has a V-shaped groove, and a backing material made of a ceramic refractory 12 and an aluminum tape 13 is disposed on the back surface of the V-shaped groove. Has been. The groove angle was set to 35 °, and the route interval of the portion where the backing material was arranged was set to 4 mm.

  After welding, the first layer welded part (excluding the crater part) is checked for the presence of internal cracks in the X-ray transmission test (JIS Z 3104), the total length of the cracked part is measured, and the crack rate is determined. Calculated. Here, the cracking rate is calculated by the cracking rate W = (total length of cracked portion) / (first layer welded portion length (excluding crater portion)) × 100. The hot crack resistance was evaluated based on the crack rate. The results are shown in Tables 4 and 5.

  The evaluation criteria are “Excellent: ◎” when the cracking rate is 0% at a welding current of 240A and the cracking rate is 0% at a welding current of 260A, and the cracking rate is 0% at a welding current of 240A and 10% at a welding current of 260A. In the following cases, “good: ○”, when there was a crack at the welding current 240A, and when there was a crack at the welding current 260A, it was judged as “inferior: x”.

(mechanical nature)
In accordance with JIS Z3313, tensile strength and 0 ° C. absorbed energy (toughness) were evaluated. The results are shown in Tables 4 and 5.
The evaluation standard of tensile strength was “excellent: ◯” when 490 MPa or more and 640 MPa or less, and “poor: x” when less than 490 MPa or more than 640 MPa. In addition, the evaluation standard of the 0 ° C. absorbed energy was “excellent: ○” when it was 60 J or more, and “inferior: ×” when it was less than 60 J. Furthermore, when evaluating elongation according to JIS Z3313, the evaluation criterion was “excellent: ◯” when 22% or more, and “inferior: ×” when less than 22%.

(Welding workability)
Using weld base material similar to hot cracking resistance, 4 types of welding, vertical fillet welding, horizontal fillet welding, vertical improvement fillet welding, vertical down fillet welding, are performed. Sensory evaluation. Here, the welding conditions of the downward fillet welding test, the horizontal fillet welding test, and the vertical downward fillet welding test were the same as those of the hot crack resistance (see Table 3). The welding conditions for the vertical improvement fillet welding test were a welding current of 200 to 220 A and an arc voltage of 24 to 27V. The results are shown in Tables 4 and 5.
The evaluation criteria were “excellent: ◯” when no welding failure such as spatter generation, fume generation, bead sagging, and bead appearance occurred, and “inferior: x” when welding failure occurred.

(Comprehensive evaluation)
The evaluation criteria for the comprehensive evaluation are “Excellent: ◎” when the hot crack resistance is “」 ”and the mechanical properties and welding workability are“ ◯ ”among the above evaluation items, and the hot crack resistance is“ ○ ”. In addition, when the mechanical property and the welding workability are “◯”, it is “good”, and when at least one of the evaluation items is “x”, it is “inferior: ×”. The results are shown in Tables 4 and 5.

  As shown in Tables 1 and 4, in Examples (Nos. 1 to 19), all the wire components satisfy the scope of the present invention. Therefore, in all of hot crack resistance, mechanical properties and welding workability. Excellent (or good), and excellent (or good) in the overall evaluation.

  As shown in Tables 2 and 5, the comparative example (No. 20) was inferior in hot cracking resistance and mechanical properties and inferior in overall evaluation because the C content was less than the lower limit. In Comparative Example (No. 21), the amount of C exceeded the upper limit value, so the hot crack resistance and welding workability were poor, and the overall evaluation was also poor. In Comparative Example (No. 22), since the Si amount was less than the lower limit, welding workability and mechanical properties (elongation) were inferior, and overall evaluation was also inferior. In Comparative Example (No. 23), since the Si amount exceeded the upper limit, the hot crack resistance was inferior, and the overall evaluation was also inferior.

  Since the amount of Mn was less than a lower limit, the comparative example (No. 24) was inferior in hot cracking resistance and mechanical properties, and was inferior in overall evaluation. In Comparative Example (No. 25), since the amount of Mn exceeded the upper limit value, the mechanical properties and welding workability were inferior, and the overall evaluation was also inferior. In Comparative Example (No. 26), since the Ti amount was less than the lower limit value, the hot crack resistance was inferior, and the overall evaluation was also inferior. In Comparative Example (No. 27), since the Ti amount exceeded the upper limit, the mechanical properties and welding workability were inferior, and the overall evaluation was also inferior.

In Comparative Example (No. 28), the amount of TiO ₂ was less than the lower limit value, so that the welding workability was poor and the overall evaluation was also poor. In Comparative Example (No. 29), the amount of TiO ₂ exceeded the upper limit value, so that the welding workability was poor and the overall evaluation was also poor. In Comparative Example (No. 30), since the Al amount was less than the lower limit value, the hot crack resistance and mechanical properties were inferior, and the overall evaluation was also inferior. In Comparative Example (No. 31), since the Al amount exceeded the upper limit, the welding workability was inferior and the overall evaluation was also inferior.

In Comparative Example (No. 32), the amount of Al ₂ O ₃ was less than the lower limit value, so that welding workability was poor and overall evaluation was poor. The comparative example (No. 33) was inferior in welding workability and inferior in overall evaluation because the amount of Al ₂ O ₃ exceeded the upper limit. Since the amount of B was less than a lower limit, the comparative example (No. 34) was inferior in mechanical properties and inferior in overall evaluation. The comparative example (No. 35) was inferior in hot cracking resistance and inferior in overall evaluation because the B amount exceeded the upper limit. In Comparative Examples (Nos. 36 to 38), (4 × Ti + 10 × Al-3 × Si) was less than the lower limit value, so the hot crack resistance was poor and the overall evaluation was also poor. The comparative example (No. 39) had poor flux workability and poor overall evaluation because the flux filling rate was less than the lower limit. In the comparative example (No. 40), since the flux filling rate exceeded the upper limit, disconnection occurred during wire production, and the overall evaluation was inferior.

  From the above results, it was confirmed that the examples (No. 1 to 19) are superior as the flux-cored wire 1 as compared with the comparative examples (No. 20 to 40).

1 Flux-cored wire (wire)
2 Steel outer shell 3 Flux 4 Seam 11 Welding base material 12 Refractory 13 Aluminum tape

Claims (1)

A flux-cored wire with a flux filled in a steel outer sheath,
The flux filling rate with respect to the total mass of the wire is 10 to 25% by mass,
For the total mass of the wire
C: 0.03-0.08 mass%,
Si (total amount of Si calculated from all Si sources contained in the wire): 0.10 to 1.00% by mass,
Mn (total amount of Mn calculated from all Mn sources contained in the wire): 2.4 to 3.7% by mass,
Ti: 0.15-1.00 mass%,
TiO _2: 5.0 to 8.0 wt%,
Al: 0.20 to 0.50 mass%,
Al ₂ O _3: 0.05~0.50 wt%,
B: 0.003-0.020 mass%
And the balance consists of Fe and inevitable impurities,
And satisfying the (4 × Ti + 10 × Al -3 × Si) ≧ 1.0 relational expression, in the relational expression (Ti) is the one of said Ti and said TiO ₂ is contained in the prior Symbol wire Ti amount calculated from Ti alone, (Al) is a flux cored wire which is a Al amount calculated from the Al only one of the Al and the Al ₂ O ₃ contained in the wire.

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