JP2010017717A - Flux-filled wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flux-filled wire having excellent high temperature cracking resistance. <P>SOLUTION: In the flux-filled wire, the flux filling rate to the total mass of the wire is 10 to 20 mass%, and the wire includes, to the total mass of the wire, 0.03 to 0.08 mass% C, 0.10 to 1.00 mass% Si (the total of Si quantity calculated from all Si sources comprised in the wire), 2.30 to 3.75 mass% Mn (the total of Mn quantity calculated from all Mn sources contained in the wire), 0.15 to 1.00 mass% Ti, 5.0 to 8.0 mass% TiO<SB>2</SB>, 0.05 to 0.50 mass% Al, 0.05 to 0.50 mass% Al<SB>2</SB>O<SB>3</SB>, and the balance Fe with inevitable impurities, and also, provided that, the Ti quantity calculated only from the above Ti is defined as Ti calculated quantity and the total of Si quantity calculated from all Si sources contained in the wire is defined as Si calculated quantity, the relation of (Ti calculated quantity/Si calculated quantity)>0.20 is satisfied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flux-cored wire used for gas shielded arc welding.

Conventionally, as a flux-cored wire used for gas shielded arc welding, a wire having the following configuration has been proposed. For example, Patent Document 1 describes a flux-cored wire for welding characterized by containing a predetermined amount of C, Si, Mn, TiO ₂ and N with respect to the total mass of the wire. In addition to the above components, it is described that a predetermined amount of one or more components selected from the group consisting of Ti, B, Ni, Cr, Mo, Al, Mg, Nb and Ta may be contained. Yes. Further, in Patent Document 2, the flux contains a predetermined amount of TiO ₂ , rare earth fluoride, Mg, Al, Si, Mn, B and Ni with respect to the total mass of the wire, and substantially contains metallic Ti. There is described a gas shielded arc welding wire characterized in that it is not.
JP-A-62-33094 JP-A 63-273594

  However, the flux-cored wire of Patent Document 1 can improve the impact characteristics by improving the toughness of the welded portion, and can also improve the welding workability, but is not satisfactory in hot crack resistance. There was no problem. Further, the flux-cored wire of Patent Document 2 has a problem that it has a low amount of diffusible hydrogen and excellent low-temperature toughness, but is not satisfactory in hot crack resistance.

  Accordingly, the present invention has been made to solve such problems, and an object thereof is to provide a flux-cored wire having excellent hot crack resistance.

In order to solve the above problems, 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 a flux filling rate with respect to the total mass of the wire is 10 to 20% 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% by mass, Al: 0.05 to 0.50% by mass, Al ₂ O ₃ : 0.05 to 0.50% by mass, the balance being Fe and inevitable impurities, and the Ti Ti amount calculated from only Ti calculated amount, When the sum of the Si amount calculated from all of the Si source contained in the tire was set to Si calculated amount, and satisfies the relationship (Ti calculated content / Si calculated amount)> 0.20.

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, and Al ₂ O ₃ is contained with respect to the total mass of the wire. As a result, the occurrence of spatter and fumes is suppressed during welding, the slag peelability is improved, the strength of the welded joint is improved, and hot cracking is suppressed. 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 the Ti-based oxide generated in the weld metal can be controlled to a composition effective for promoting nucleation. As a result, the solidification structure of the welded joint can be refined, and the action of suppressing high temperature cracking is improved.

According to the flux-cored wire according to the present invention, the flux filling rate is a predetermined amount, contains a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al and Al ₂ O ₃ , and the flux-cored wire By satisfying a predetermined relationship between the Ti content and the Si content contained in the steel, it has excellent welding workability (including bead appearance), joint strength, and hot crack 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.

And the wire 1 has a predetermined amount of flux filling, contains a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al and Al ₂ O ₃ , and the balance consists of Fe and inevitable impurities, In addition, 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 filled in the steel outer sheath 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 and Al ₂ O ₃ are added regardless of whether they are added from the steel outer shell 2 or the flux 3, It may be added to at least one of the steel outer skin 2 and the flux 3.

(Flux filling ratio: 10 to 20% by mass)
When the flux filling rate is less than 10%, the stability of the arc is deteriorated, the amount of spatter is increased, and the welding workability is lowered. On the other hand, if the flux filling rate exceeds 20%, 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 weld 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 a region where a peritectic reaction occurs, high temperature cracks are likely to occur in the weld. As the C source, for example, hoop, 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. If the amount of Si is less than 0.10% by mass, the ductility 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, the toughness tends to decrease. Moreover, a hot crack occurs in the weld. As the Si source, for example, an alloy such as hoop, Fe—Si, Fe—Si—Mn, fluoride such as K ₂ SiF ₆ , oxide such as zircon sand, silica sand, and 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 reduced, the action of suppressing high-temperature cracking by MnS is reduced, and high-temperature cracking occurs in the 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. As the Mn source, for example, an alloy such as a hoop, 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 to improve the hot crack resistance of the welded portion (welded metal). 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 welded joint (welded part) can be made fine, and the welded part The hot cracking resistance of is improved. If the amount of Ti (metal Ti) is less than 0.15% by mass, hot cracking occurs in the weld. 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. In addition, as Ti source, alloy powder, such as Fe-Ti, is used, for example.

_(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 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 added in an appropriate amount, the oxygen content of the weld metal is reduced, the yield of Mn is stabilized, the hot cracking resistance of the weld is improved, and the toughness is also stabilized. If the amount of Al is less than 0.05% by mass, deoxidation is not sufficient, and hot cracks occur in the weld. If the Al amount exceeds 0.50% by mass, the amount of spatter generated during welding increases and welding workability decreases. In addition, as Al source, alloy powder, such as Al metal powder, Fe-Al, Al-Mg, is used, for example.

_(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.

((Ti calculation amount / Si calculation amount)> 0.20)
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 crack resistance can be remarkably improved. Furthermore, it is preferable that the Ti-based oxide effective for promoting nucleation does not contain SiO ₂ . 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 hot cracking resistance. It becomes.

  When (Ti calculation amount / Si calculation amount) ≦ 0.20, the solidification structure of the welded joint 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 calculation amount is a Ti amount calculated only from the Ti (metal Ti) contained in the wire 1 and is calculated (converted) from the TiO ₂ (Ti oxide) contained in the wire 1. This does not include Ti content.
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 the Fe amount is the Fe amount in the steel outer shell 2.
(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.

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: 0.02 mass%, Si: 0.01 mass%, Mn: 0.20 mass%, P: 0.010 mass%, S: 0.007 mass%, A flux cored wire having a wire diameter of 1.2 mm made of the wire components shown in Tables 1 and 2 (Examples: Nos. 1 to 23) is filled inside the balance Fe and inevitable impurities). Comparative Example: No. 24-40).

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 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, they do 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).

  Using the prepared flux-cored wire, hot cracking resistance, mechanical properties (tensile strength, absorbed energy), and welding workability were evaluated by the following methods. Based on the evaluation results, comprehensive evaluation of the flux-cored wires of Examples and Comparative Examples 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: 0.013% 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 refractory 12 and an aluminum tape 13 is disposed on the back surface of the V-shaped groove. . 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 the end of welding, the first layer welded portion (excluding the crater portion) was checked for the presence of internal cracks in an X-ray transmission test (JIS Z 3104), and the crack rate was calculated. The hot crack resistance was evaluated based on the crack rate. The results are shown in Tables 4 and 5.

  Note that the evaluation criteria are “much better when the cracking rate is 0% at the welding current 240A and the cracking rate is 0% at the welding current 260A:」 ”, the cracking rate is 0% at the welding current 240A and the cracking rate at the welding current 260A. When it is 5% or less, “excellent: ○ to ◎”, when cracking rate is 0% at welding current 240A and when cracking rate is more than 5% at welding current 260A, “good: ○”, cracking occurs at welding current 240A and When there was a crack at the welding current 260A, it was judged as “Inferior: x”.

(mechanical nature)
According to JIS Z3313, tensile strength and absorbed energy were evaluated.
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. The evaluation criteria for absorbed energy were “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 welding base material similar to high temperature cracking resistance, 4 types of welding, down fillet welding, horizontal fillet welding, upright rise fillet welding, upright down fillet weld, are performed to improve workability. Sensory evaluation was performed. Here, the welding conditions were the same as the hot crack resistance (see Table 3).
The evaluation criteria were “excellent: ◯” when no welding failure such as spattering, fume generation, bead sagging occurred, and “inferior: x” when welding failure occurred.

(Comprehensive evaluation)
The evaluation criteria of the comprehensive evaluation are that, among the above evaluation items, when the hot crack resistance is “◎” and the mechanical properties and the welding workability are “◯”, “much better: ◎”, the hot crack resistance is “Excellent: ○-◎” when the mechanical properties and welding workability are “○”, hot cracking resistance is “○”, and mechanical properties and welding workability are “○”. When it was “good: ◯”, when at least one of the evaluation items was “x”, it was “poor: x”.

  As shown in Tables 1 and 4, in Examples (Nos. 1 to 23), 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. 24) 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. 25), the C amount exceeded the upper limit value, so that the welding workability was poor and the overall evaluation was also poor. In Comparative Example (No. 26), since the Si amount was less than the lower limit value, the welding workability was inferior and the overall evaluation was also inferior. The comparative example (No. 27) was inferior in hot cracking resistance and inferior in overall evaluation because the Si amount exceeded the upper limit.

  In Comparative Example (No. 28), since the amount of Mn was less than the lower limit, the hot crack resistance and mechanical properties were inferior, and the overall evaluation was also inferior. In Comparative Example (No. 29), since the amount of Mn exceeded the upper limit, the mechanical properties and welding workability were inferior, and the overall evaluation was also inferior. Since the amount of Ti was less than a lower limit, the comparative example (No. 30) was inferior in hot-cracking resistance and inferior in overall evaluation. The comparative example (No. 31) was inferior in mechanical properties and welding workability because the Ti amount exceeded the upper limit, and the overall evaluation was also inferior.

Comparative Example (No.32), since the amount of TiO ₂ is less than the lower limit, poor weldability, was inferior overall rating. In Comparative Example (No. 33), 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. 34), 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. The comparative example (No. 35) was inferior in welding workability and inferior in overall evaluation because the Al amount exceeded the upper limit.

Since the amount of Al ₂ O ₃ was less than the lower limit, the comparative example (No. 36) was inferior in welding workability and inferior in overall evaluation. In Comparative Example (No. 37), the amount of Al ₂ O ₃ exceeded the upper limit value, so that the welding workability was poor and the overall evaluation was also poor. In Comparative Example (No. 38), 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. 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 example (No. 1 to 23) is superior as the flux-cored wire 1 as compared with the comparative example (No. 24 to 40).

It 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 Joint 11 Welding base material 12 Backing material 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 20% 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% by mass, Al: 0.05 to 0.50% by mass, Al ₂ O ₃ : 0.05 to 0.50% by mass, the balance consisting of Fe and inevitable impurities, and
When the Ti amount calculated from only Ti is the Ti calculated amount, and the total Si amount calculated from all the Si sources contained in the wire is the Si calculated amount, (Ti calculated amount / Si calculated amount)> A flux-cored wire characterized by satisfying a relationship of 0.20.

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