JP5314414B2 - Flux cored wire - Google Patents

Abstract

The invention provides a flux-cored wire with excellent high-temperature crackle forming property, welding operability, and property of machinery for welding metal. Rosin flux filling rate in mass percentages of the flux-cored wire relative to total mass of welding wire is 10-25%, relative to the total mass of the welding wire, the flux-cored wire contains: in weight percentage, C: 0.03-0.08%, Si: 0.10-1.00%, Mn: 2.30-3.75%, Ti: 0.15-1.00%, TiO2: 5.0-8.0%, Al: 0.05-0.50%, Al2O3: 0.05-0.50%, Mg: 0.30-1.00%, and the rest amount composed of Fe and unavoidable impurity. Further, the Ti amount calculated from the Ti is used as a calculation amount, and the sum of the Si amount calculated from total Si source contained in the welding wire is used as a Si calculation amount, which satisfies the relationship (Ti calculation amount/Si calculation amount)>0.20.

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. Further, the wire because it does not contain Al ₂ O _3, there is a problem that weldability is poor in all position welding. In addition, since the amount of Mn of a wire is small, there also exists a problem that the mechanical property of a weld metal is 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 (sum of Mn amount calculated from all Mn source contained in the wire): 2.30 to 3.75 mass%, Ti: .15-1.00 _wt%, TiO 2: 5.0 to 8.0 mass%, Al: 0.05 to 0.50 _{wt%, Al} 2 O 3: _0.05~0.50 wt%, Mg: 0.30 to 1.00 and containing mass%, the balance being Fe and inevitable impurities, and contained in the wire The Ti calculated amount of Ti amount calculated from the Ti only one of TiO ₂ and the Ti, when the total amount of Si calculated from all the Si source contained in the wire and the Si calculated amount that, The relationship of (Ti calculation amount / Si calculation amount)> 0.20 is satisfied.

According to the above configuration, the flux filling rate with respect to the total mass of the wire is a predetermined amount, and the predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al, Al ₂ O ₃ and Mg is contained with respect to the total mass of the wire As a result, the occurrence of spatter and fume is suppressed during welding, the slag peelability is improved, the strength of the welded joint (welded metal) is improved, and high-temperature cracking in the first layer weld is suppressed. The Further, when the Ti calculation amount and the Si calculation amount satisfy a predetermined relationship, that is, (Ti calculation amount / Si calculation amount)> 0.20, Ti contributes to the deoxidation reaction during welding. The composition of inclusions generated in the weld metal can be controlled 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.

  In addition, the flux-cored wire is characterized by further containing 0.500% by mass or less in terms of rare earth element of one or more rare earth compounds based on the total mass of the wire.

  According to the said structure, the yield of Ti to a weld metal improves by further containing the 1 type or 2 types or more of predetermined amount of rare earth compounds, and the composition of the inclusion | inclusion produced | generated in a weld metal is a Ti-type oxidation. It becomes easy to control the composition of the composition, and the effect of suppressing hot cracking is further improved.

According to the flux-cored wire according to the present invention, the flux filling rate is a predetermined amount, containing a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al, Al ₂ O ₃ , Mg, and flux By satisfying a predetermined relationship between the amount of Ti and the amount of Si contained in the cored wire, high temperature cracking resistance in the first layer welded portion is excellent, welding workability (including bead appearance) and weld metal in all-position welding The mechanical properties of are excellent. As a result, it is possible to provide a welded product with excellent quality.

  Moreover, when the wire further contains one or more rare earth compounds, the hot crack resistance in the first layer welded portion is further improved.

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, contains a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al, Al ₂ O ₃ and Mg, and the balance is Fe and inevitable impurities. And the Ti calculation amount and the Si calculation amount satisfy a predetermined relationship (specifically, (Ti calculation amount / Si calculation amount) exceeds a predetermined value).

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 Mg are not particularly limited as to 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, if 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 and toughness 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: 2.30-3.75% by mass)
Mn is added to ensure the hardenability of the weld. When the amount of Mn is less than 2.30% 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 3.75% 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: 0.05 to 0.50 mass%, preferably 0.05 to 0.40 mass%)
Al is a strong deoxidizer, and if it is added in an appropriate amount, the amount of oxygen in the weld metal is reduced, the yield of Mn is stabilized, and the action of suppressing high-temperature cracking in the weld (first layer weld) is improved. Toughness is also stabilized. If the amount of Al is less than 0.05% 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.

(Mg: 0.30 to 1.00% by mass)
Mg is a strong deoxidizer, and if added in an appropriate amount, the oxygen content of the weld metal is lowered, the yield of Mn is stabilized, the action of suppressing high-temperature cracking is improved, and the toughness is also stabilized. If the amount of Mg is less than 0.30% by mass, deoxidation is not sufficient, and hot cracking occurs in the welded portion (first layer welded portion). Also, toughness is reduced. When the amount of Mg exceeds 1.00% by mass, the amount of spatter generated increases. In addition, the addition of Mg improves the yield of Ti to the weld metal and enables a substantial reduction in the amount of Ti used. In addition, the yield of Ti to the weld metal is improved, and inclusions in the weld metal can be controlled to an effective Ti-based oxide composition for promoting nucleation. As the Mg source, for example, metal powder such as metal Mg, Al—Mg, Fe—Si—Mg, or alloy powder is used.

((Ti calculation amount / Si calculation amount)> 0.20)
(Ti calculation amount / Si calculation amount) is set in order to improve the hot cracking resistance by controlling the degree of refinement of the solidification structure of the weld metal. That is, 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 weld metal is the core. It can be controlled to a Ti-based oxide composition effective for promoting the generation. As a result, the solidification structure of the weld metal can be made fine, and the hot cracking suppressing effect can be remarkably improved. Furthermore, it is preferable that the Ti-based oxide effective for promoting nucleation does not contain SiO ₂ that suppresses the refinement of the solidified structure. Therefore, the Ti amount (metal Ti) contained in the wire 1 is defined by the relationship with the Si amount contained in the wire 1, and specifically, the ratio between the Ti calculated amount and the Si calculated amount, that is, (Ti calculation) By defining the amount / Si calculated amount), the Ti-based oxide composition can be controlled to an effective composition by refining the solidification structure, and the solidification structure of the weld metal can be controlled to be favorable in improving the hot cracking suppression effect. It becomes.

  When (Ti calculation amount / Si calculation amount) ≦ 0.20, the solidification structure of the weld metal is not refined. Therefore, (Ti calculation amount / Si calculation amount)> 0.20, preferably (Ti calculation amount / Si calculation amount)> 0.25, and more preferably (Ti calculation amount / Si calculation amount)> 0.37. .

Here, the Ti calculated amount, in the Ti Ti amount calculated only from (metal Ti) of the TiO ₂ and the Ti is contained in the wire 1, the _TiO 2 (Ti contained in the wire 1 The amount of Ti calculated (converted) from (oxide) is not included.
Further, the Si calculated amount 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.

  Moreover, the wire 1 according to the present invention may further contain one or more rare earth compounds in the wire component. And the amount of rare earth compounds shall be 0.500 mass% or less in terms of rare earth elements.

(Rare earth compound: 0.500 mass% or less in terms of rare earth element)
The rare earth element is a strong deoxidizer, and if it is added in an appropriate amount, the yield of Ti to the weld metal is improved, and the amount of Ti used can be substantially reduced. In addition, the yield of Ti to the weld metal is improved, and inclusions in the weld metal can be controlled to an effective Ti-based oxide composition for promoting nucleation, and the hot cracking resistance of the weld (first layer weld) is improved. The sex is further improved. However, if the content exceeds 0.500% by mass in terms of rare earth elements, the amount of spatter generated increases, the arc becomes unstable, and the bead appearance becomes poor. The rare earth element referred to in the present invention refers to Sc, Y, and atomic numbers 57 (La) to 71 (Lu). The rare earth compound is an oxide of a rare earth element (Nd ₂ O ₃ , La ₂ O ₃ , Y ₂ O ₃ , CeO ₃ , Ce ₂ O ₃ , Sc ₂ O _3, or a simple oxide or a composite thereof. oxides and monazite, bastnaesite, Aranaito, including celite, xenotime, ore rare earth oxide such as Gadorinaito), fluoride _{(CeF 3, LnF 3, PmF} 3, SmF 3, GdF 3, TbF 3 and the like) and An alloy (rare earth element-Fe, rare earth element-Fe-B, rare earth element-Fe-Co, rare earth element-Fe-Si, rare earth element-Ca-Si, etc.), Misch metal.

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%, The inside of the balance Fe and unavoidable impurities) is filled with flux at the filling rate (Flux filling rate) shown in Tables 1 and 2 and shown in FIG. 1B with a wire diameter of 1.2 mm. Wire 1 (Example: No. 1-32 and comparative example: No. 33-52) was produced.

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 and the amount of Mn were measured by “ICP emission spectroscopy” 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.

(Present as Fe-Ti and the like, it does not include TiO _2, etc.) Ti amount, the wire the total amount was dissolved into aqua regia, filtered TiO ₂ source was insoluble the (TiO2, etc.) by "acid decomposition method" 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).

  The amount of Mg and the amount of rare earth compound (rare earth element amount) were measured by “ICP emission spectroscopy” after dissolving the whole wire. Note that misch metal was used as the rare earth compound, and rare earth elements (Ce, La) were measured.

  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 internal cracks in the X-ray transmission test (JIS Z 3104), the total length of the cracked part is measured, and the cracking rate is calculated. did. 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 were “Excellent: ◎◎” when the cracking rate was 0% at a welding current of 240A, the cracking rate of 0% at a welding current of 260A, and the cracking rate of 0% at a welding current of 280A. When it is 0%, the cracking rate is 0% at a welding current 260A, and the welding current 280A is 5% or less, “Better”: ◎, the cracking rate is 0% at a welding current 240A, the cracking rate is 5% or less at a welding current 260A, and welding When the current cracking rate is more than 5% to 10% or less at a current of 280A, it is “excellent: ○ ˜ ◎”, the cracking rate is 0% at a welding current of 240A, the cracking rate is greater than 5% at a welding current of 260A, When it exceeded%, it was judged as “Inferior: X”, when cracked at welding current 240A, cracked at welding current 260A, and cracked at welding current 280A.

(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 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, among the evaluation items described above, when the hot crack resistance is “◎◎ or ◎” and the mechanical properties and welding workability are “◯”, “much better: ◎”, high temperature resistance When the cracking property is “◯ to ◎” and the mechanical properties and welding workability are “◯”, “Excellent: ○ to ◎”, the hot cracking resistance is “○”, and the mechanical properties and welding workability are “ When it was “good”, “good: good”, and when at least one of the evaluation items was “x”, it was “poor: good”. The results are shown in Tables 4 and 5.

  As shown in Tables 1 and 4, in Examples (Nos. 1 to 32), 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 Table 2 and Table 5, the comparative example (No. 33) 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. 34), the C amount exceeded the upper limit value, so that the welding workability was inferior and the overall evaluation was also inferior. In Comparative Example (No. 35), since the Si amount was less than the lower limit value, welding workability and mechanical properties (elongation) were inferior, and overall evaluation was also inferior. The comparative example (No. 36) was inferior in hot cracking resistance and inferior in overall evaluation because the Si amount exceeded the upper limit.

  Since the amount of Mn was less than a lower limit, the comparative example (No. 37) was inferior in hot crack resistance and mechanical properties, and was inferior in overall evaluation. In Comparative Example (No. 38), since the amount of Mn exceeded the upper limit, the mechanical properties and welding workability were inferior, and the overall evaluation was also inferior. In Comparative Example (No. 39), since the Ti amount was less than the lower limit, the hot crack resistance was inferior and the overall evaluation was also inferior. The comparative example (No. 40) was inferior in mechanical properties and welding workability because the Ti amount exceeded the upper limit, and the overall evaluation was also inferior.

In Comparative Example (No. 41), 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. Comparative Example (No.42), since the amount of TiO ₂ exceeds the upper limit, poor weldability, was inferior overall rating. In Comparative Example (No. 43), since the Al amount was less than the lower limit, the hot cracking resistance and mechanical properties were inferior, and the overall evaluation was also inferior. In Comparative Example (No. 44), since the Al amount exceeded the upper limit, the welding workability was inferior, and the overall evaluation was also inferior.

Since the amount of Al ₂ O ₃ was less than the lower limit value in the comparative example (No. 45), the welding workability was inferior and the overall evaluation was also inferior. The comparative example (No. 46) was inferior in welding workability and inferior in overall evaluation because the amount of Al ₂ O ₃ exceeded the upper limit. In Comparative Example (No. 47), the amount of Mg was less than the lower limit value, so the hot crack resistance and mechanical properties were inferior, and the overall evaluation was also inferior. In Comparative Example (No. 48), the amount of Mg exceeded the upper limit value, so that welding workability was inferior and overall evaluation was also inferior. In Comparative Example (No. 49), since (Ti calculation amount / Si calculation amount) was less than the lower limit value, the hot crack resistance was inferior and the overall evaluation was also inferior. Since the comparative example (No. 50) has a flux filling rate less than the lower limit value, the welding workability is poor and the overall evaluation is also poor. In the comparative example (No. 51), since the flux filling rate exceeded the upper limit value, disconnection occurred during wire production, and the overall evaluation was inferior. In the comparative example (No. 52), since the rare earth element amount exceeded the upper limit, the arc became unstable and the amount of spatter generated increased. Further, the bead appearance was poor.

  From the above results, it was confirmed that the examples (Nos. 1 to 32) were superior as the flux-cored wire 1 compared to the comparative examples (Nos. 33 to 52).

(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.

Explanation of symbols

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

Claims (2)

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, and with respect to 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): 2.30 to 3.75% by mass,
Ti: 0.15-1.00 mass%,
TiO _2: 5.0 to 8.0 wt%,
Al: 0.05 to 0.50 mass%,
Al ₂ O _3: 0.05~0.50 wt%,
Mg: 0.30 to 1.00% by mass
And the balance consists of Fe and inevitable impurities, and
Ti amount calculated from only Ti among the TiO ₂ and Ti contained in the wire is calculated as Ti, and the total amount of Si calculated from all Si sources contained in the wire is calculated as Si. A flux-cored wire characterized by satisfying a relationship of (Ti calculation amount / Si calculation amount)> 0.20.   2. The flux-cored wire according to claim 1, wherein the wire further contains one or more rare earth compounds in an amount of 0.500% by mass or less in terms of rare earth elements based on the total mass of the wire.

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