KR101134841B1 - Flux cored wire - Google Patents

Abstract

An object of the present invention is to provide a flux cored wire having excellent high temperature crack resistance.

Flux cored wire has a flux filling rate of 10 to 20% by mass relative to the total mass of the wire, C: 0.03 to 0.08% by mass relative to the total mass of the wire, and Si (sum of Si amount calculated from all Si sources contained in the wire). ): 0.10 to 1.00 mass%, Mn (total amount of Mn calculated from all Mn sources contained in the wire): 2.30 to 3.75 mass%, Ti: 0.15 to 1.00 mass%, TiO ₂ : 5.0 to 8.0 mass%, Al : 0.05 to 0.50 mass%, Al ₂ O ₃ : 0.05 to 0.50 mass%, the remainder being made of Fe and unavoidable impurities, and the amount of Ti calculated only from the Ti is contained in the Ti output and the wire. When the sum total of Si amount computed from all the Si sources is made into Si output amount, the relationship of (Ti output amount / Si output amount)> 0.20 is satisfied.

Flux cored wire, steel sheath, aluminum tape, flux, welded base material

Description

Flux cored wire {FLUX CORED WIRE}

The present invention relates to flux cored wire used in gas shielded arc welding.

Conventionally, what has the structure as shown below is proposed as a flux cored wire used for gas shielded arc welding. For example, Patent Document 1 describes a flux cored wire for welding, which contains a predetermined amount of C, Si, Mn, TiO ₂ and N, based on the total mass of the wire. In addition to the above components, it is described that a predetermined amount of one or two or more components selected from the group of Ti, B, Ni, Cr, Mo, Al, Mg, Nb, and Ta may be contained. Further, Patent Document 2 discloses that the flux contains a predetermined amount of TiO ₂ , rare earth fluorides, Mg, Al, Si, Mn, B, and Ni, and substantially does not contain Ti in the metal state, based on the total mass of the wire. A gas shielded arc welding wire is described.

[Patent Document 1] Japanese Patent Application Laid-Open No. 62-33094

[Patent Document 2] Japanese Patent Application Laid-open No. 63-273594

However, although the flux cored wire of patent document 1 can improve impact characteristics and improve welding workability by improving the toughness of a weld part, there existed a problem that it was not satisfactory in high temperature crack resistance. Moreover, although the flux cored wire of patent document 2 has a small amount of diffusible hydrogen and excellent low-temperature toughness, there existed a problem that it was not able to be satisfied in high temperature crack resistance.

Accordingly, the present invention was devised to solve such a problem, and an object thereof is to provide a flux cored wire having excellent high temperature crack resistance.

In order to solve the said subject, the flux cored wire which concerns on this invention is a flux cored wire in which the flux was filled in the steel outer shell, the flux filling rate with respect to the wire total mass is 10-20 mass%, and with respect to the wire whole mass, C: 0.03 to 0.08 mass%, Si (total amount of Si calculated from all Si sources contained in the wire): 0.10 to 1.00 mass%, Mn (total amount of Mn amount calculated from all Mn sources contained in the wire): 2.30 to 3.75 mass%, Ti: 0.15 to 1.00 mass%, TiO ₂ : 5.0 to 8.0 mass%, Al: 0.05 to 0.50 mass%, Al ₂ O ₃ : 0.05 to 0.50 mass%, and the balance is Fe and inevitable When the amount of Ti made of red impurities and calculated only from the Ti and the total amount of Si calculated from the Ti output and all the Si sources contained in the wire is taken as the Si output, the (Ti output / Si output)> 0.20 Of It is characterized by satisfying the relationship.

According to the above configuration, the flux filling rate with respect to the total wire mass is a predetermined amount, and when welding, by containing a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al and Al ₂ O ₃ with respect to the total wire mass, Spatter generation and fume generation are suppressed, slug peelability is improved, the strength of the weld joint is improved, and high temperature cracking is suppressed. Further, the Ti output amount and the Si output amount satisfy a predetermined relationship, that is, the (Ti output amount / Si output amount)> 0.20, whereby Ti contributes to the deoxidation reaction during welding, thereby improving the composition of the Ti-based oxide produced in the weld metal. The composition can be controlled to be effective in promoting nucleation. As a result, the solidification structure of a weld joint can be refined | miniaturized and the suppression effect of a high temperature crack improves.

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 is contained in the flux cored wire. By satisfy | filling a predetermined relationship with Ti amount and Si amount, it has the outstanding welding workability (including bead appearance), joint strength, and high temperature crack resistance.

The flux cored wire which concerns on this invention is demonstrated in detail. (A)-(d) is sectional drawing which shows the structure of a flux cored wire.

As shown in Figs. 1A to 1D, the flux cored wire (hereinafter referred to as wire) 1 is a steel outer shell 2 formed in a tubular shape, and a flux 3 filled in the barrel. ) Further, the wire 1 is a seamless type in which the flux 3 is filled in a tub of a seamless outer sheath 2 as shown in Fig. 1A, Figs. 1B to 1D. Any form of the shim type in which the flux 3 is filled in the barrel of the steel outer sheath 2 with the seam 4 as shown in FIG.

The wire 1 has a predetermined flux filling rate, contains a predetermined amount of C, Si, Mn, Ti, TiO ₂ , Al, and Al ₂ O ₃ , and the remainder is made of Fe and unavoidable impurities. Ti output and Si output satisfy a predetermined relationship (specifically, (Ti output / Si output) 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 sheath 2 as a ratio with respect to the total mass of the wire 1 (steel sheath 2 + flux 3). In addition, the component amount is represented by the sum total 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 sheath 2 + flux 3) is determined by the wire ( It is specified as a ratio with respect to the total mass of 1). In addition, among the components constituting the wire 1, C, Si, Mn, Ti, TiO ₂ , Al, and Al ₂ O ₃ may be added from the steel sheath 2 or from the flux 3, and in particular, What is necessary is just to add to at least one of the steel outer shell 2 and the flux 3.

(Flux filling rate: 10-20 mass%)

If the flux filling rate is less than 10%, the stability of the arc deteriorates, the amount of spatter generated increases, and the welding workability deteriorates. In addition, when the flux filling rate exceeds 20%, disconnection of the wire 1 occurs, and the productivity is significantly degraded.

(C: 0.03-0.08 mass%)

C is added to ensure the hardenability of the welded portion. When the amount of C is less than 0.03% by mass, the strength and toughness of the weld portion are insufficient due to the lack of hardenability. In addition, high-temperature cracking occurs in the welded portion by a low C amount. When the amount of C exceeds 0.08 mass%, the amount of spatter generated or the amount of fume generated at the time of welding increases and welding workability falls. Moreover, when there is much C amount of the steel material which is a to-be-welded material, C amount of a weld part (welding metal) increases. When C is a region causing a peritectic reaction, high temperature cracks tend to occur in the weld zone. As the C source, for example, an alloy powder such as hoop or Fe-Mn, iron powder or the like is used.

(Si: 0.10 to 1.00 mass%)

Si is added to secure the ductility of the welded part and to maintain the bead shape. If the amount of Si is less than 0.10 mass%, the ductility of a weld part will become short. In addition, the shape of the beads deteriorates, in particular, the beads are struck in the vertical up welding, thereby deteriorating the welding workability. If the amount of Si exceeds 1.00 mass%, toughness will fall easily. In addition, high temperature cracks occur in the weld zone. As the Si source, for example, alloys such as hoop, Fe-Si, Fe-Si-Mn, fluorides such as K ₂ SiF ₆ , oxides such as zircon sand, silica sand, feldspar and the like are used.

(Mn: 2.30 to 3.75 mass%)

Mn is added to secure the hardenability of the welded portion. If Mn amount is less than 2.30 mass%, the hardenability of a weld part will run short and toughness will fall. Moreover, since the amount of MnS obtained by combining with S contained as an unavoidable impurity also becomes small, the suppression effect of the high temperature crack by MnS becomes small, and a high temperature crack arises in a weld part. When the amount of Mn exceeds 3.75 mass%, the strength of the welded portion becomes excessive and the toughness is insufficient. In addition, low temperature cracking occurs in the welded portion. As the Mn source, for example, alloys such as hoop, Mn metal powder, Fe-Mn, and Fe-Si-Mn are used.

(Ti: 0.15 to 1.00 mass%, preferably 0.20 to 1.00 mass%)

Ti (metal Ti) is added to improve the high temperature crack resistance of the welded part (welded metal). Ti (metal Ti) contributes to the deoxidation reaction during welding, and the inclusions in the weld metal can be controlled by the Ti-based oxide composition, and as a result, the solidification structure of the weld joint (weld portion) can be made fine, High temperature crack resistance is improved. If Ti amount (metal Ti) is less than 0.15 mass%, high temperature crack will generate | occur | produce in a welding part. When Ti amount (metal Ti) exceeds 1.00 mass%, a weld metal reheat part becomes hard and soft bainite and martensite easily, and toughness falls. Moreover, the spatter generation amount at the time of welding increases, and welding workability falls. As the Ti source, for example, an alloy powder such as Fe-Ti is used.

(TiO ₂ : 5.0 to 8.0 mass%)

TiO ₂ (Ti oxide) is added to ensure overall posture weldability. If the amount of TiO ₂ (Ti oxide) is less than 5.0% by mass, beads are struck in the upward-facing upstream welding, and welding workability is lowered. TiO ₂ amount (Ti oxide) and if it exceeds 8.0% by weight, is degraded slag removability at the time of welding, the welding operability deteriorates. In addition, the bulk specific gravity of the flux is reduced, resulting in deterioration in productivity. As the TiO ₂ source, for example, rutile or the like is used.

(Al: 0.05-0.50 mass%, Preferably 0.05-0.40 mass%)

Al is a strong deoxidizer, and if it is added in an appropriate amount, the oxygen content of the weld metal is lowered, the yield of Mn is stabilized, the high temperature crack resistance of the welded portion is improved, and the toughness is also stabilized. If Al amount is less than 0.05 mass%, deoxidation is not enough and a high temperature crack will generate | occur | produce in a weld part. When Al amount exceeds 0.50 mass%, the amount of spatters at the time of welding will increase, and welding workability will fall. In addition, as Al source, alloy powders, such as Al metal powder, Fe-Al, Al-Mg, are used, for example.

(Al ₂ O ₃ : 0.05 to 0.50 mass%, preferably 0.05 to 0.40 mass%)

Al ₂ O ₃ is added to prevent beads from sagging in the horizontal fillet posture and in the upright posture. If the amount of Al ₂ O ₃ is less than 0.05% by mass, the bead shape (affinity) in the horizontal fillet welding is bad, and bead sag occurs in the upstream welding, resulting in poor welding workability. Al ₂ O ₃ when the amount exceeds 0.50% by mass, the slag removability is deteriorated at the time of welding, the welding operability deteriorates. As the Al ₂ O ₃ source, for example, a composite oxide such as alumina or feldspar is used.

[(Ti output / Si output)> 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, thereby promoting nucleation of the composition of inclusions generated in the weld joint (welding metal). It can be controlled by inclusion of an effective Ti-based oxide composition. As a result, the solidification structure of a weld metal can be made fine and a high temperature crack resistance can be improved remarkably. In addition, it is preferable that Ti-type oxide which is effective for promoting nucleation does not contain SiO ₂ . Therefore, Ti amount (metal Ti) contained in the wire 1 is prescribed | regulated by the relationship with Si amount contained in the wire 1, Specifically, the ratio of Ti output amount and Si output amount, ie, (Ti output amount / Si Output amount), the Ti-based oxide composition can be controlled to an effective composition by miniaturization of the solidified structure, and the solidified structure of the weld metal can be controlled to be preferable in improving high temperature cracking resistance.

(Ti output amount / Si output amount) ≤ 0.20, the solidification structure of the weld joint is not reduced. Therefore, (Ti output / Si output)> 0.20, preferably (Ti output / Si output)> 0.25, more preferably (Ti output / Si output)> 0.37.

Here, the are, the Ti amount is calculated from only the Ti (metal Ti) contained in the wire (1), Ti is (converted) calculated from the TiO ₂ (Ti oxide) contained in the wire (1) as Ti output The amount does not include.

In addition, Si output amount means the sum total of Si amount computed from the whole said Si source contained in the wire 1. Further, the SiO ₂ is contained in the oxide, such as, for example, zircon sand, silica sand, feldspar is used as a Si source.

(Fe)

Fe in the remainder is equivalent to Fe constituting the steel sheath 2, and the Fe amount is the amount of Fe in the steel sheath 2.

(Inevitable impurities)

S, P, Ni, O, Zr etc. are mentioned as an unavoidable impurity of a remainder, It is acceptable to contain in the range which does not prevent the effect of this invention. The amount of S, the amount of P, the amount of Ni, the amount of O, and the amount of Zr are preferably 0.050 mass% or less, respectively, and are the sum of the amounts of each component in the steel sheath 2 and the flux 3.

In addition, the steel outer shell 2 and the flux 3 select each component (each amount of components) of the steel outer shell 2 and the flux 3 so that the said wire component (component amount) may be in the said range at the time of wire manufacture.

(Example)

About the flux cored wire which concerns on this invention, the Example which satisfy | fills the requirements of this invention, and the comparative example which does not satisfy the requirements of this invention are demonstrated concretely.

Steel outer sheath (steel contains C: 0.02 mass%, Si: 0.01 mass%, Mn: 0.20 mass%, P: 0.010 mass%, S: 0.007 mass%, and uses a remainder containing Fe and unavoidable impurities) Flux was filled in the inside, and the flux cored wire (Example: No. 1-23, Comparative example: No. 24-40) of the wire diameter of 1.2 mm which consists of the wire component shown in Table 1, Table 2 was produced.

In addition, the wire component was measured and calculated by the following measuring methods.

The amount of C was measured by the "infrared absorption method." The amount of Si and the amount of Mn melt | dissolved the wire whole quantity, and were measured by "ICP emission spectroscopy."

TiO ₂ amount (present as TiO ₂ or the like, and is not included, such as Fe-Ti) is measured by the "acid decomposition". The solvent used for the acid decomposition method used aqua regia, and melt | dissolved the whole wire. As a result, Ti source (Ti-Fe, etc.) contained in the wire (1), but is dissolved in aqua regia, TiO ₂ source (TiO _2, etc.) because it is insoluble for aqua regia, and is not dissolved. The solution was filtered using a filter (fine filter of 5C), the residue was transferred to a nickel crucible with a filter cloth, and heated with a gas burner to ash. Subsequently, an alkali flux (a mixture of sodium hydroxide and sodium peroxide) was added, and the residue was further melted by heating with a gas burner. Next, 18 mass% hydrochloric acid was added, the melt was liquefied, transferred to a measuring flask, and pure water was further added to mes-up to obtain an analyte. Ti concentration in the analysis solution was measured by "ICP emission spectrometry". In terms of the Ti concentration of the TiO ₂ amount was calculated the amount of TiO _2.

Ti amount (exists as Fe-Ti, etc., does not include TiO _2, etc.) dissolves the entire wire amount into aqua regia by the "acid decomposition method", filters insoluble TiO ₂ members (TiO _2, etc.) Was obtained as a Ti source (Fe-Ti etc.) contained in the wire 1, and presence was calculated | required as Ti amount (Fe-Ti etc.) using "ICP emission spectroscopy."

The amount of Al ₂ O ₃ (exists as a composite oxide such as alumina or feldspar and does not include alloy powder such as Al metal powder) is measured by the "acid decomposition method". The solvent used for the acid decomposition method melt | dissolved the whole wire using aqua regia. 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 (composite oxide such as alumina or feldspar) is insoluble in aqua regia, and therefore does not dissolve. . This solution was filtered using a filter (5 C fine scale of filtration paper), the residue was transferred to a nickel crucible with a filter cloth, and heated with a gas burner to incinerate. Subsequently, an alkali flux (a mixture of sodium hydroxide and sodium peroxide) was added, and the residue was further melted by heating with a gas burner. Next, after adding 18 mass% hydrochloric acid to liquefy the melt, it transferred to the measuring flask, and further pure water was added and the volume was made up, and the analysis liquid was obtained. Al concentration in the analysis solution was measured by "ICP emission spectrometry". In terms of the Al concentration of the Al ₂ O ₃ amount was calculated Al ₂ O ₃ amount.

Al amount (exists as alloy powder such as Al metal powder and does not include complex oxide such as alumina or feldspar) dissolves the whole wire in aqua regia by the "acid decomposition method" and insoluble Al ₂ O ₃ source (alumina or Complex oxide such as feldspar, and the solution was obtained as an Al source (alloy powder such as Al metal powder) contained in the wire 1, and the amount of Al (Al metal powder using the ICP emission spectrometry) was obtained. Presence of the alloy powder).

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

(High Temperature Cracking Resistance)

Welding base material which consists of JIS G3106 SM400B steel (C: 0.12 mass%, Si: 0.2 mass%, Mn: 1.1 mass%, P: 0.008 mass%, S: 0.013 mass%, and remainder Fe and an unavoidable impurity) Was welded on one side under the welding conditions shown in Table 3 (downward butt welding).

It is sectional drawing which shows the improved shape of the welding base material used for evaluation of high temperature crack resistance. As shown in FIG. 2, the welding base material 11 has a V shape improvement, and the backing material which consists of the refractory body 12, the aluminum tape 13, etc. is arrange | positioned at the back surface of this V shape improvement. And the improvement angle was 35 degrees, and the root spacing of the part in which the padding material is arrange | positioned was 4 mm.

After the completion of welding, the crack rate was calculated by checking the presence of internal cracks in the X-ray transmission test (JIS Z 3104) for the superlayer welded portion (excluding the crater portion). The high temperature crack resistance was evaluated by the crack ratio. The results are shown in Tables 4 and 5.

In addition, the evaluation criteria are " very good: ◎ " when the cracking rate is 0% at the welding current 240A, and the cracking rate is 0% at the welding current 260A. `` Excellent: ○ ~ ◎ '', crack ratio 0% at welding current 240A, cracking rate 5% at welding current 260A when below, "good: ○", crack at welding current 240A, and welding current 260A When there was a crack at, it was "falling off: x".

(Mechanical properties)

Tensile strength and absorbed energy were evaluated in accordance with JIS Z3313.

In addition, the evaluation criteria of tensile strength were made into "excellent: (circle)" when it is 490 Mpa or more and 640 Mpa or less, "falling: x" when it is less than 490 Mpa or more than 640 Mpa. In addition, the evaluation criteria of absorbed energy were made into "excellent: (circle)" when 60J or more, and "falling: x" when it was less than 60J. In the case of evaluating elongation according to JIS Z3313, the evaluation criteria were "excellent: ○" when 22% or more, and "falling: x" when less than 22%.

(Welding workability)

Using the same welding base material as the high temperature crack resistance, four kinds of welding such as a downward fillet welding, a horizontal fillet welding, an upwardly upward fillet welding, and a downwardly downward fillet welding were performed to perform sensory evaluation of workability. Here, welding conditions were similar to the said high temperature crack resistance (refer Table 3).

In addition, evaluation criteria were made "excellent: when the welding defect, such as spatter generation | occurrence | production, a fume generation | occurrence | production, bead drooping, did not generate | occur | produce, and" falling: x "when a welding defect generate | occur | produced.

(General evaluation)

The evaluation criterion of comprehensive evaluation is "very excellent: when the high temperature crack resistance is" (◎) "and the mechanical property and welding workability" (circle) "among the said evaluation items: ◎ ”, and when the mechanical property and the welding workability is“ ○ ”,“ excellent: ○ ~ ◎ ”, the high temperature crack resistance is“ ○ ”and when the mechanical property and the welding workability are“ ○ ” Good: When "(circle)" and at least 1 of the said evaluation items are "x", it was set as "falling: x."

As shown in Table 1 and Table 4, Examples (Nos. 1 to 23) are excellent (or high temperature crack resistance, mechanical properties and welding workability as a whole) because all the wire components satisfy the scope of the present invention. Good), and also excellent (or good) in comprehensive evaluation.

As shown in Table 2 and Table 5, since the amount of C was less than a lower limit in Comparative Example (No. 24), high temperature crack resistance and mechanical properties were inferior, and comprehensive evaluation was also inferior. Since the amount of C exceeded the upper limit in the comparative example (number 25), weldability was inferior and comprehensive evaluation was also inferior. Since the amount of Si was less than a lower limit in the comparative example (number 26), weldability was inferior and comprehensive evaluation was also inferior. Since the amount of Si exceeded the upper limit in Comparative Example (No. 27), high temperature crack resistance was inferior, and comprehensive evaluation was also inferior.

Since the amount of Mn was less than a lower limit in the comparative example (number 28), high temperature crack resistance and mechanical property fell, and comprehensive evaluation also fell. In Comparative Example (No. 29), the amount of Mn exceeded the upper limit, so that mechanical properties and welding workability were inferior, and overall evaluation was also poor. Since the amount of Ti was less than the lower limit in Comparative Example (No. 30), high temperature crack resistance was inferior, and comprehensive evaluation was also inferior. In the comparative example (number 31), since Ti amount exceeded the upper limit, mechanical property and weldability were inferior, and comprehensive evaluation was also inferior.

In Comparative Example (No. 32), since the TiO _{2 content} was less than the lower limit, welding workability was inferior, and overall evaluation was also poor. Comparative Example (No. 33) exceeds the upper limit, so the amount of TiO _2, dropping the welding workability, was also off assessment. Since the amount of Al was less than the lower limit in Comparative Example (No. 34), high temperature crack resistance and mechanical properties were inferior, and overall evaluation was also inferior. Since the amount of Al exceeded the upper limit in the comparative example (number 35), weldability was inferior and comprehensive evaluation was also inferior.

Comparative Example (No. 36) because it is less than the amount of Al ₂ O ₃ the lower limit value, the welding workability is poor, there is also off assessment. Comparative Example (No. 37), so the amount of Al ₂ O ₃ exceeds the upper limit, poor welding workability, was also off assessment. In Comparative Example (No. 38), since (Ti output / Si output) was below the lower limit, high temperature crack resistance was inferior, and comprehensive evaluation was also poor. Since the flux filling rate of the comparative example (number 39) was less than a lower limit, weldability was inferior and comprehensive evaluation was also inferior. In the comparative example (No. 40), since the flux filling rate exceeded the upper limit, disconnection occurred during wire production, and was poor as a comprehensive evaluation.

From the above results, it was confirmed that the Examples (Nos. 1 to 23) were superior as the flux cored wires 1 than the Comparative Examples (Nos. 24 to 40).

1 is a cross-sectional view showing a configuration of a flux cored wire according to the present invention.

2 is a cross-sectional view showing an improved shape of a weld base metal used for evaluation of high temperature crack resistance.

<Explanation of symbols for the main parts of the drawings>

1: Flux cored wire (wire)

2: forced shell

3: flux

4: seam

11: welding base material

12: adding material

13: aluminum tape

Claims (1)

Flux cored wire for gas shielded arc welding with flux filled in a steel sheath, The flux filling rate is 10-20 mass% with respect to the wire total mass, C: 0.03 to 0.08 mass%, Si (total amount of Si calculated from all Si sources contained in the wire): 0.10 to 1.00 mass%, Mn (calculated from all Mn sources contained in the wire) and containing 0.05 to 0.50% by mass: total of the Mn amount): 2.30 to 3.75 mass%, Ti: 0.20 to 1.00 wt%, TiO _2: 5.0 to 8.0 mass%, Al: 0.05 to 0.50 mass%, Al ₂ O ₃ , The remainder consisting of Fe and unavoidable impurities, When the amount of Ti calculated only from the Ti is the amount of Ti output and the sum of the amount of Si calculated from all the Si sources contained in the wire as the Si output, the relationship of (Ti output / Si output)> 0.20 is satisfied. Flux cored wire for gas shielded arc welding.

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