KR102056637B1 - Flux cored wire for gas shield - Google Patents

Abstract

Gas shield flux filling wire is provided.
The filling wire of the present invention is, by weight% to the total weight of the wire, TiO ₂ : 5.0 to 10.0%, C: 0.01 to 0.04%, Si: 0.40 to 0.80%, Mn: 1.60 to 2.20%, Mg: 0.40 to 1.20%, Ni: 0.20-0.70%, B: 0.001-0.020%, Nb: 0.010% or less, V: 0.020% or less, Na + K: 0.3-1.0%, F equivalent in alkali and alkaline earth metal fluorine compounds: 0.05 to 0.15%, residual Fe and unavoidable impurities, and the A value defined by the relationship 1 is 0.20 to 0.40.

Description

Gas shield flux filling wire {Flux cored wire for gas shield}

The present invention relates to a gas shield flux-filled wire, and more particularly, is used for welding steels with tensile strengths of 490 MPa to 670 MPa, and is -40 ° C. low for both specifications of As-weld and post-weld heat treatment (PHWT). The present invention relates to a gas shield flux-filled wire having excellent toughness and total weldability.

The stability of energy supply is important all over the world, and due to factors such as the Climate Change Convention, environmentally-friendly and energy-efficient nuclear power is increasing in countries with high dependence on imports of energy resources.

As the structure of pressure vessels used in various plants, such as nuclear power plants, thermal power plants, and petroleum refining plants, is diversified, the requirements for welding materials are also varied, such as excellent welding workability and low temperature toughness.

Conventionally, the mechanical properties of the weld metal and the overall posture of gas-shielded flux-filled wires with guaranteed tensile strength of 490-670 MPa class (As-weld) and post-heat treatment (PWHT) toughness. Various studies have already been made for the purpose of welding workability.

For example, Korean Patent Laid-Open Publication No. 2017-0021891 discloses a weld metal having excellent weldability in all postures and excellent strength and low temperature toughness after welding (As-weld) and post-heat treatment (PWHT). A gas shielded flux filled wire is shown which gives the composition of the wire so that it can be obtained. Specifically, in order to obtain a weld metal having good low-temperature toughness both in the state of welding and after heat treatment, the flux-filled wires disclosed in the above-mentioned patents include C, Si, Mn, Ni, B, Mg, V, Ti oxides, and C. 1% by mass or less of Ni in the weld metal required by the National Association of Corrosion Engineers (NACE) standard (NACE MR0175) through relational control by specific content consisting of Mn, Si, Cr, and Mo. It is suggested that a weld metal with good low-temperature toughness can be obtained in both the welded and post-weld heat treatment (PHWT) specifications.

However, pressure vessels used in various plants, such as nuclear power generation, thermal power generation and petroleum refining plants, use high tensile steels (commonly referred to as high tensile steels for yield points or steels with a yield strength of more than 36 ㎏f / ㎠). High strength steel is used for high pressure, large pressure vessel, storage tank, etc.

However, the gas shield flux filling wire described in the above-mentioned patent is proposed mainly for low temperature toughness, so that sufficient welding workability is not secured for thin steel, that is, thin steel (≤10 mm) steel applied in nuclear power generation, thermal power generation, and various plants. I'm not.

Accordingly, an object of the present invention is to provide a gas shielded flux-filled wire that can be obtained from a welded sheet having excellent weldability and excellent in -40 ° C low temperature toughness both in the state of welding and in post-weld heat treatment.

In addition, the technical problems to be achieved in the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above are clearly understood by those skilled in the art from the following description. Could be.

The present invention for achieving the above object,

In the flux filling wire in which the flux in the metal shell is filled,

By weight of the total weight of the wire, TiO ₂ : 5.0 ~ 10.0%, C: 0.01 ~ 0.04%, Si: 0.40 ~ 0.80%, Mn: 1.60 ~ 2.20%, Mg: 0.40 ~ 1.20%, Ni: 0.20 ~ 0.70%, B: 0.001 ~ 0.020%, Nb: 0.01% or less, V: 0.02% or less, Na + K: 0.3 ~ 1.0%, F conversion amount in alkali and alkaline earth metal fluorine compounds: 0.05 ~ 0.15%, residual Fe And flux filling wire for gas shielded arc welding comprising an unavoidable impurity, wherein the A value defined by the following relational formula 1 satisfies 0.20 to 0.40.

[Relationship 1]

The present invention having the above-described configuration provides excellent low temperature toughness at -40 ° C for both the As-weld specification and the post-weld heat treatment (PHWT) specification, and at the same time, the gas shield flux having excellent all-over weldability. The charging wire can be provided effectively.

Therefore, by using this, welding can be effectively performed on thin steels, that is, thin steel (≤10 mm) steels that are applied in various plants such as nuclear power generation, thermal power generation and petroleum refining plants.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a cut surface of an elevational weld bead obtained when a thin plate is welded using wires of the invention examples and comparative examples in an embodiment of the invention.

Hereinafter, the present invention will be described.

The positively charged wire of the present invention is, by weight% to the total weight of the wire, TiO ₂ : 5.0 to 10.0%, C: 0.01 to 0.04%, Si: 0.40 to 0.80%, Mn: 1.60 to 2.20%, Mg: 0.40 to 1.20%, Ni: 0.20-0.70%, B: 0.001-0.020%, Nb: 0.01% or less, V: 0.02% or less, Na + K: 0.3-1.0%, F equivalent in alkali and alkaline earth metal fluorine compounds: 0.05 to 0.15%, residual Fe and unavoidable impurities, and the A value defined by the above relationship 1 is 0.20 to 0.40.

Hereinafter, the composition of the flux-filled wire of the present invention and the reason for limiting the content thereof will be described, and% described herein means weight% unless otherwise stated.

TiO ₂ : 5.0 ~ 10.0%

TiO ₂ is the main component of the slag former as well as the arc stabilizer.

In addition, in the present invention, it is important to control the TiO ₂ content in order to ensure excellent welding workability on the thin plate. If the TiO ₂ content is less than 5.0%, the slag solidification property is lowered, which makes it difficult to weld the electric field. Upper welding becomes difficult. On the other hand, when the TiO ₂ content exceeds 10.0%, the amount of oxygen in the weld metal increases, thereby reducing the low-temperature toughness of the As-weld specification and the post-weld heat treatment (PHWT) specification, and increasing the spatter generation amount due to the decrease in meltability.

Therefore, in the present invention, the TiO ₂ content is preferably limited to 5.0 to 10.0%.

C: 0.01 ~ 0.04%

In the present invention, carbon is an austenite stabilizing element capable of securing the strength of the weld metal and securing the low-temperature impact toughness of the weld metal. However, when the carbon content is low, austenite is not stabilized, so it is necessary to maintain an appropriate amount of carbon, so the lower limit thereof is set to 0.01%. On the other hand, when the carbon content exceeds 0.04%, carbides are rapidly increased at the austenite grain boundaries after the post-heat treatment, which is not preferable because it adversely affects the toughness.

In consideration of this, in the present invention, it is preferable to limit the carbon (C) content to 0.01 to 0.04% range.

Si: 0.40 to 0.80%

When the content of silicon in the present invention is less than 0.40%, the deoxidation effect in the weld metal portion is insufficient and the fluidity of the weld metal portion is reduced. On the other hand, if the content exceeds 0.80%, the strength of the weld metal portion is increased and thus the toughness is lowered.

Therefore, in the present invention, the content of silicon (Si) is preferably limited to 0.40 to 0.80%.

Mn: 1.60-2.20%

In the present invention, Mn is a relatively weak deoxidizer and an element that serves to improve strength. Since MnS is formed before FeS by reacting with S, it is effective in preventing high temperature cracking by preventing formation of low melting point compound due to segregation of S.

In the present invention, it is preferable to limit the Mn content to 1.60 to 2.20%, which is less than 1.60%, in which the deoxidation effect in the weld metal part is insufficient, thereby reducing the toughness. On the other hand, if the content exceeds 2.20%, it is not preferable because the formation of low-temperature transformation tissue rapidly decreases the crack resistance and toughness and increases the strength.

Mg: 0.40 to 1.20%

In the present invention, Mg reacts with oxygen in the molten metal as a strong deoxidizer to suppress the generation of nonmetallic inclusions, thereby improving the cleanliness of the weld metal. However, if the content is less than 0.40%, the effect according to the above content cannot be expected. If the content exceeds 1.20%, the amount of spatter is increased and the fluidity and arc property of the molten metal are reduced, so the content is 0.40 to 1.20%. Limited to.

Ni: 0.2 ~ 0.70%

In the present invention, Ni is an essential element for improving the strength and toughness of the matrix by solid solution strengthening. In order to obtain such an effect, it is preferable that Ni is contained in more than 0.20%, but in the case of exceeding 0.70%, the yield of Ni increases and increases compared to the designed weld metal content, thereby lowering the strength and toughness.

Therefore, in the present invention, it is preferable to limit the content of nickel (Ni) to 0.20 ~ 0.70% range.

B (boron): 0.001-0.020%

B has the effect of improving notch toughness. If the B content is less than 0.001%, it is difficult to expect the addition effect. If the B content is more than 0.020%, the toughness improvement effect is rapidly decreased, and at the same time, the B aggregates between the grains and rapidly degrades the high temperature cracking property. .

Therefore, in the present invention, the B content is preferably limited to 0.001 to 0.020% range.

Nb: 0.010% or less, V: 0.020% or less

Trace amounts of Nb or V are present in the TiO ₂ source and can affect the crystal composition and mechanical properties of the weld metal. Nb and V, as elements added as impurities, are precipitated at grain boundaries and not only increase weld strength by solid solution but also affect toughness. In addition, when performing post-weld heat treatment (PWHT), Nb and V are deposited on all the tissues of the weld metal, thereby reducing the toughness.

Therefore, in the present invention, it is preferable to limit the content of Nb and V to the range of 0.010% or less and 0.020% or less, respectively.

Na + K: 0.3-1.0%

Alkali metals Na and K, which are classified as arc stabilizers, achieve arc stabilization during welding, resulting in good workability. Therefore, in the present invention, it is preferable to limit the sum of one or more of the alkali metals Na and K (Na + K) in the range of 0.3 to 1.0%. If the content is less than 0.3%, the workability is lowered due to arc anxiety, This is because if it exceeds 1.0%, the amount of fume is increased and the toughness is lowered by increasing the oxygen content in the welded joint.

F conversion amount in alkali and alkaline earth metal fluorine compounds: 0.05 to 0.15%

Since the fluorine compound generates fluorine in the arc in the high temperature arc and reacts with hydrogen during welding, a dehydrogenation reaction can effectively lower the diffusible hydrogen in the welded joint. However, if the F conversion amount of the fluorine compound is less than 0.05%, it is difficult to expect the above-described effects, and if the amount of F exceeds 0.15%, the amount of fume is excessively increased, thereby limiting the content range to 0.05 to 0.15%.

In the present invention, it is preferable to use one or two or more of NaF ₂ , KSF, and MgF ₂ as the fluorine compound.

A value defined by relation 1 below: 0.20 to 0.40

[Relationship 1]

The flux-filled wire of the present invention satisfies all of the above-described composition and at the same time provides excellent low-temperature toughness of -40 ° C for both specifications of excellent welding workability in sheet metal and as-weld specification and post-weld heat treatment (PHWT) specification. In order to control the TiO ₂ , Mg, Si, and Mn content so that the A value defined by the above Equation 1 satisfies the range of 0.20 to 0.40.

If the A value is less than 0.20, the arc deterioration and spatter generation amount due to excessive slag formation are increased, and the amount of oxygen in the weld metal is increased to reduce toughness. On the other hand, when it exceeds 0.40, sufficient slag is not formed, and since arc property falls by excessive alloy component transition, it is difficult to expect the outstanding welding workability in the thin plate which this invention requires.

And the flux filling wire of the present invention contains Fe and unavoidable impurities as residual components, where Fe includes Fe in the metal shell, Fe powder in the flux, and the like.

Flux-filled wire welding material according to an embodiment of the present invention is composed of a hoop and a flux filled in the inside of the wire is a mild steel material, the weight ratio of the flux to the total weight of the flux-filled arc welding wire achieves 14.0 ~ 20.0%. Can be.

By providing a welding material that satisfies the above alloy composition, it is possible to secure excellent low-temperature toughness at -40 ° C for both the YS 400 grade As-weld specification and the post-weld heat treatment (PHWT) specification. Excellent electron beam welding efficiency can be secured at.

Meanwhile, the welded joint obtained after welding using the flux-filled wire satisfying the alloy composition described above forms a structure composed of 50 to 60% of acicular ferrite and 30 to 40% of grain boundary ferrite. The impact toughness value at -40 ° C is over 60J for both low strength of 400MPa and As-weld specification and post-weld heat treatment (PHWT) specification, showing excellent low temperature impact toughness.

Hereinafter, the present invention will be described in detail through examples.

(Example)

phrase
minute No
Wire composition component (wt%) A
TiO ₂ C Si Mn Mg Ni B Nb V Na + K F

foot
persons
Yes

One 7.1 0.026 0.65 1.87 0.65 0.43 0.009 0.0020 0.012 0.56 0.09 0.27 2 5.3 0.03 0.60 1.92 0.66 0.44 0.009 0.0020 0.013 0.52 0.10 0.38 3 9.6 0.031 0.62 2.01 0.62 0.44 0.010 0.0015 0.012 0.61 0.09 0.23 4 7.35 0.033 0.72 2.16 0.8 0.43 0.009 0.0018 0.011 0.55 0.11 0.24 5 9.6 0.032 0.55 1.85 0.6 0.42 0.009 0.0018 0.010 0.56 0.12 0.23 6 6.9 0.03 0.60 1.62 0.5 0.43 0.009 0.0017 0.009 0.49 0.10 0.30 7 5.8 0.029 0.63 1.83 0.55 0.23 0.010 0.0018 0.009 0.52 0.10 0.38 8 6.6 0.031 0.69 1.79 0.61 0.66 0.011 0.0019 0.010 0.55 0.09 0.27 9 8.5 0.030 0.70 1.75 0.40 0.46 0.010 0.0020 0.011 0.50 0.10 0.31



ratio
School
Yes








One 4.03 0.029 0.62 1.9 0.63 0.44 0.010 0.0019 0.0013 0.51 0.10 0.50 2 11.6 0.034 0.6 1.88 0.6 0.43 0.009 0.002 0.0010 0.49 0.11 0.18 3 8.5 0.031 1.1 1.86 0.62 0.45 0.009 0.0021 0.0011 0.53 0.09 0.14 4 8.5 0.031 0.1 1.86 0.62 0.45 0.009 0.0021 0.0011 0.53 0.09 0.33 5 8.5 0.031 0.59 2.8 0.62 0.45 0.009 0.0021 0.0011 0.55 0.09 0.42 6 8.5 0.031 0.59 1.3 0.62 0.45 0.009 0.0021 0.0011 0.56 0.09 0.13 7 8.5 0.031 0.59 1.78 1.5 0.45 0.009 0.0021 0.0011 0.51 0.09 0.09 8 8.5 0.031 0.59 1.78 0.2 0.45 0.009 0.0021 0.0011 0.53 0.09 0.70 9 7.8 0.029 0.62 1.82 0.62 0.10 0.010 0.0019 0.0012 0.56 0.10 0.25 10 7.2 0.030 0.65 1.89 0.59 0.92 0.011 0.0020 0.0011 0.50 0.10 0.29 11 8.1 0.031 0.72 1.96 0.52 0.46 0.036 0.0021 0.0011 0.52 0.11 0.29 12 7.9 0.032 0.66 2.00 0.55 0.44 0.000 0.0022 0.0010 0.49 0.09 0.31 13 7.6 0.033 0.69 1.82 0.6 0.43 0.009 0.0200 0.0220 0.56 0.11 0.25 14 8.5 0.032 0.78 1.62 0.65 0.42 0.010 0.0020 0.0011 0.52 0.10 0.15 15 9 0.032 0.68 1.72 0.65 0.42 0.011 0.0019 0.0011 0.53 0.11 0.18 16 6.1 0.029 0.59 2.11 0.55 0.44 0.010 0.0021 0.0011 0.55 0.09 0.45 17 7.2 0.030 0.44 1.99 0.43 0.45 0.011 0.0019 0.0010 0.49 0.09 0.50

The flux filling welding wires each having a composition as shown in Table 1 were prepared. Subsequently, flux-charged arc welding was performed using the respective welding wires under conditions of a welding current of 260 to 280 A, a voltage of 30 to 32 V, a welding speed of 26 to 30 cm / min, and a welding heat input amount of 15 to 20 kJ / cm. At this time, as the base material for welding, EH36 steel having a low carbon (C) yield strength of 360 MPa or more was used.

And the mechanical performance of the weld metal formed by the arc welding and the enhanced welding workability of the thin plate was evaluated, the results are shown in Table 2 below.

The test pieces for evaluating the mechanical properties of the welded metal parts were taken from the center of the welded metal part, and carried out after welding according to KEPIC-MDW 5.20 standard of nuclear engineering 620 ℃ × 8hr, and the tensile test piece was KS standard (KS B 0801). ) No. 4 test piece was used. In addition, the tensile test was tested at the cross head speed (cross head speed) 10mm / mim, the impact test specimen was prepared according to KS (KS B 0809) No. 3 test piece.

In addition, the uplift welding workability of thin plate is assembled with 6mm thick SS400 steel by fillet, hand welding under welding condition 160 ~ 180A / 22 ~ 24V, and then the bead cross-section shown after welding It was evaluated that the ratio of ((length ① + angle 2)) / 2) satisfies 0.9 to 1.1.

division No. Heat input
(kJ / cm) vE-40 ℃
(J) Yield strength
(MPa) The tensile strength
(MPa) Elongation
(%) 6mm improvement
Workability
(Neck thickness / length) Comprehensive Evaluation
foot
persons
Yes One 18 82 483 542 29.6 Good (0.95) ○ 2 17 90 492 556 29.4 Good (0.96) ○ 3 18 78 505 576 28.6 Good (0.99) ○ 4 19 69 529 592 27 Good (0.92) ○ 5 18 80 466 540 29.6 Good (0.99) ○ 6 18 89 454 529 31.4 Good (1.01) ○ 7 18 65 470 532 30.4 Good (0.96) ○ 8 17 72 473 539 29.6 Good (0.96) ○ 9 19 76 478 550 29.2 Good (0.93) ○
ratio
School
Yes One 18 96 492 558 29.2 Drop (1.22) X (Low Weldability) 2 19 55 477 549 29.8 Good (1.06) X (under impact toughness) 3 16 53 523 583 27.6 Degradation (1.16) X (impact toughness,
Under welding workability) 4 18 43 423 493 34.2 Medium (1.13) X (under impact toughness) 5 17 36 571 630 24.2 Drop (1.21) X (impact toughness,
Under welding workability) 6 18 59 449 513 32.6 Medium (1.14) △ (normal welding workability) 7 18 96 529 593 26.8 Drop (1.21) X (Low Weldability) 8 18 31 547 528 31.2 Good (0.99) X (under impact toughness) 9 19 33 466 532 29.2 Good (0.96) X (under impact toughness) 10 18 79 488 553 28.8 Medium (1.12) △ (normal welding workability) 11 19 83 496 569 28.8 Medium (1.14) △ (normal welding workability) 12 18 35 483 560 29.2 Medium (1.13) X (impact toughness,
Weldability) 13 18 43 486 553 29.0 Good (1.02) X (under impact toughness) 14 17 62 493 556 28.6 Degradation (1.29) X (Low Weldability) 15 19 72 499 562 29.0 Medium (1.14) △ (normal welding workability) 16 19 63 503 568 28.2 Medium (1.13) △ (normal welding workability) 17 19 70 525 596 27.4 Degradation (1.19) X (Low Weldability)

 In Table 2, ○ is good, △ is normal, and X is under.

As shown in Table 1-2, in the examples of the present invention (1-9) subjected to flux-filled arc welding using the welding wire according to the present invention, the weld metal part of the post-weld heat treatment (PHWT) specification- The impact toughness of 60J or more was secured at 40 degreeC, and also it can be confirmed that the upright welding workability of a thin plate is also favorable.

On the contrary, the comparative examples (1 to 17) in which the wire composition is welded using a welding wire that is out of the scope of the present invention or the A value defined by the above-mentioned relational expression 1 does not satisfy 0.20 to 0.40 are impacted. It can be seen that the toughness and upstream welding workability is poor.

Specifically, in Comparative Examples 1 and 2, the TiO ₂ content was lower or higher than the level required by the present invention, so that the vertically welded weldability of the thin plate was lowered or the post-heat treatment at -40 ° C. was not good.

In addition, in the case of Comparative Examples 3 to 6, the Si or Mn content is lower or excessively contained than the level required by the present invention. When the Si or Mn content is low, the oriented upward weldability of the thin plate required by the present invention is satisfied. The impact toughness was bad, and when the Si or Mn content was high, it could be confirmed that the upright welding workability and impact toughness of the thin plate decreased.

In addition, Comparative Examples 7 to 8 is a case where the Mg content is lower or excessively contained than the level required by the present invention, and when the Mg is low, the vertically welded weldability of the thin plate required by the present invention was good, but the weld metal deoxidation was insufficient. The impact toughness was bad, and when the Mg content was high, the weld metal deoxidation effect was sufficiently made, and thus the impact toughness was very good.

In Comparative Examples 9 to 10, the Ni component range was lower or excessively contained than the level required by the present invention. When Ni was low, it was difficult to expect the effect of sufficient solid solution strengthening. In the case of high, it was confirmed that the upturning welding workability of the thin plate decreased due to the deterioration of the arc property.

Comparative Examples 11 to 12 are the case where the B component range is lower or excessively contained than the level required by the present invention. When B is low, impact toughness is lowered, and when B is high, cracking occurs during welding, and thus welding workability is achieved. This deterioration can be confirmed.

Comparative Example 13 is a case where the Nb, V content is higher than the level required by the present invention, when performing the post-weld heat treatment (PWHT) it can be confirmed that the impact toughness is reduced because Nb, V is deposited on all tissues of the weld metal. have.

In case of Comparative Examples 14 to 17, the component range required by the present invention was satisfied, but the A value defined by Equation 1 did not satisfy 0.20 to 0.40. Can be confirmed.

1 is a view showing a cut surface of an elevational weld bead obtained when welding a thin plate using the wires of Inventive Example 1 and Comparative Example 1 of the present invention. As shown in Figure 1, it can be seen that the invention example 1 is superior in welding workability compared to the comparative example 1.

As described above, in the detailed description of the present invention has been described with respect to preferred embodiments of the present invention, those skilled in the art to which the present invention pertains various modifications without departing from the scope of the present invention Of course this is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents thereof.

Claims (1)

In the flux filling wire filled with the flux in the metal shell,
By weight of the total weight of the wire, TiO ₂ : 5.0 ~ 10.0%, C: 0.01 ~ 0.04%, Si: 0.40 ~ 0.80%, Mn: 1.60 ~ 2.20%, Mg: 0.40 ~ 1.20%, Ni: 0.20 ~ 0.70%, B: 0.009 ~ 0.020%, Nb: 0.010% or less, V: 0.020% or less, Na + K: 0.3 ~ 1.0%, F conversion amount in alkali and alkaline earth metal fluorine compounds: 0.05 ~ 0.15%, residual Fe And flux-filled wire for gas shielded arc welding comprising inevitable impurities, wherein the A value defined by the following relational formula 1 satisfies 0.20 to 0.40.
[Relationship 1]

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