KR101783415B1 - Flux cored wire for gas shielded arc welding - Google Patents

Abstract

A flux-charging wire for gas shield arc welding is provided.
The positive filler wire of the present invention comprises 4.0 to 9.5% of TiO ₂ , 0.01 to 0.20% of C, 0.1 to 1.0% of Si, 1.0 to 2.5% of Mn, 0.3 to 0.5% of Ni, 0.1 to 0.4% of ZrO ₂ , 0.1 to 0.4% of SiO ₂ , 0.1 to 0.3% of Al ₂ O ₃ , 0.005 to 0.025% of B, the balance of Fe and unavoidable impurities , And the L value defined by the following relational expression 1 satisfies the range of 1.00 to 1.30.
[Relation 1]

Description

{FLUX CORED WIRE FOR GAS SHIELDED ARC WELDING FOR GAS SHIELD ARC WELD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux-charging wire for gas shield arc welding, and more particularly, to a flux-charging wire for gas-shielded arc welding which is excellent in low temperature impact toughness and low temperature CTOD characteristics of a weld metal during welding.

In recent years, due to the increasing demand for global energy, the demand for offshore structures that require stability in the polar regions is increasing as interest in polar development, in which various resources such as large-scale oil and natural gas exist, is increasing. In addition, there is an increasing demand for high strength and low temperature impact toughness of steel due to large size of ships. Accordingly, as the stability of the offshore structures in the polar regions and the shipbuilding vessels to be enlarged becomes important matters, the demand for the welding materials that can guarantee the toughness characteristics at low temperatures is also increasing.

In order to secure the low-temperature toughness characteristics of the weld metal of shipbuilding and offshore structures, it is important to secure low-temperature impact toughness and CTOD toughness. Generally, flux welding is applied to welding in marine structure and shipbuilding, and the amount of heat input corresponding to about 7 to 25 kJ / cm is used in flux filling. At this time, depending on the microstructure of the weld metal, the low-temperature impact toughness and the CTOD toughness of the weld metal are greatly influenced.

In general, a weld metal formed at the time of welding is solidified to form a columnar crystal structure, and coarse columnar crystals and grain boundary ferrites are formed along the austenite grain boundaries in crystal grains. The weld metal in which such a coarse texture is formed is the region where the low temperature impact toughness characteristic is the worst. On the other hand, acicular ferrite is produced from nonmetallic inclusions existing in the austenite grains. Acicular ferrite among the weld metal microstructures has properties to improve low temperature impact toughness and fracture toughness. Therefore, in order to secure impact toughness and CTOD characteristics at a cryogenic temperature of a welded structure, it is necessary to control the microstructure of the weld metal to secure low temperature impact toughness and low temperature CTOD characteristics of the weld metal.

A related art related to this is the invention disclosed in Korean Patent Publication No. 10-1210294. In the above patent, it is proposed to control the content of C, TiO2, Mn, Si, Ni, Ti and the oxide and Ti ratio to improve good low temperature impact toughness and welding workability. However, There are limitations in characteristics.

Therefore, there is an urgent need to develop a flux-charging wire having excellent low-temperature impact toughness and low-temperature CTOD characteristics.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in order to overcome the limitations of the prior art described above, and provides a flux charging wire for gas shield arc welding excellent in low-temperature impact toughness and low-temperature CTOD characteristics of a weld metal by appropriately controlling the components of the flux- .

Further, the technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems which are not mentioned can be understood from the following description in order to clearly understand those skilled in the art to which the present invention belongs .

According to an aspect of the present invention,

The flux-filled wire is filled with a flux in a metal shell. The wire is composed of 4.0 to 9.5% of TiO ₂ , 0.01 to 0.20% of C, 0.1 to 1.0% of Si, 0.1 to 1.0% of Si, 0.1 to 0.4% of ZrO ₂ , 0.1 to 0.4% of SiO ₂ , 0.1 to 0.3% of Al ₂ O ₃ , and 0.005 to 0.3% of B, 0.025%, the balance Fe, and unavoidable impurities, and has an L value defined by the following relational expression 1 satisfying the range of 1.00 to 1.30.

[Relation 1]

The filling rate of the flux is preferably in the range of 10 to 20%.

The use of the flux-filled wire of the present invention having the above-described structure has the advantage of securing a weld metal having excellent low-temperature impact toughness and CTOD characteristics.

FIG. 1 is a graph showing the change of low temperature impact toughness according to the L value of the relational expression 1. FIG.
Fig. 2 is a photograph of a tissue in which the low-temperature impact toughness and the CTOD characteristics are insufficient and in a good case.

Hereinafter, the present invention will be described.

The flux-filling wire of the present invention is characterized in that it contains 4.0 to 9.5% of TiO ₂ , 0.01 to 0.20% of C, 0.1 to 1.0% of Si, 1.0 to 2.5% of Mn, 0.3 to 0.5% of Ni, 0.1 to 0.4% of ZrO ₂ , 0.1 to 0.4% of SiO ₂ , 0.1 to 0.3% of Al ₂ O ₃ , 0.005 to 0.025% of B, the balance of Fe and unavoidable impurities .

The charging wire of the present invention is formed such that the L value defined by the following relational expression 1 satisfies the range of 1.00 to 1.30.

[Relation 1]

First, the constituent components of the flux-packed wire of the present invention and their reasons for limitation will be described in detail. Hereinafter, the content of the composition component is expressed as% by weight with respect to the total weight of the wire.

Carbon (C): 0.01 to 0.20%

C is contained in the steel shell and flux of the wire of the present invention, and maintains the strength of the weld metal and suppresses generation of intergranular ferrite, thereby improving low-temperature impact toughness. And it enhances the arc force so that the penetration is sufficient to prevent the shortage of penetration. However, if the content of C is less than 0.01%, the toughness and strength of the weld metal deteriorate. If the content of C exceeds 0.20%, the strength becomes excessively high and the crack resistance may deteriorate.

In view of this, in the present invention, the content of C is preferably limited to 0.01 to 0.20%.

TiO ₂ : 4.0 to 9.5%

TiO ₂ (Ti oxide) is a main slag forming agent when welding, and serves to protect molten metal from the atmosphere. If the content of TiO ₂ (Ti oxide) is less than 4.0%, the amount of slag is insufficient and the molten metal can not be sufficiently protected from the atmosphere and spatter generation is increased. When the content of TiO ₂ (Ti oxide) exceeds 9.5% There is a problem that the molten metal is excessively formed and the fluidity is lowered and a part of the slag is mixed into the inside of the weld metal to significantly deteriorate the mechanical performance of the welded portion, so that the content thereof is preferably 4.0 to 9.5%.

Manganese (Mn): 1.0 to 2.5%

Mn is a deoxidizer which reduces the amount of oxygen in the weld metal and maintains the strength of the weld metal. If the content of Mn is less than 1.0%, the tensile strength and impact toughness of the weld metal deteriorate. If the content of Mn exceeds 2.5%, the impact strength tends to be lowered due to an increase in strength and cracking may occur. .

Silicon (Si): 0.1 to 1.0%

Similar to Mn, Si reduces the amount of oxygen in the weld metal as a deoxidizer, maintains the strength of the weld metal, and improves slag fluidity and bead appearance when added in an appropriate amount. If the Si content is less than 0.1%, the tensile strength and impact toughness of the weld metal deteriorate and the bead appearance improving effect is insufficient. When the Si content is more than 1.0%, the slag fluidity decreases, impact toughness decreases, Therefore, the content thereof is preferably 0.1 to 1.0%.

Nickel (Ni): 0.3 to 3.0%

Ni is an austenite stabilizing element and has an effect of stabilizing impact toughness at a low temperature and improving the CTOD toughness by making the structure finer. If the Ni content is less than 0.3%, the effect of stabilizing the impact resistance at low temperatures can not be exhibited. If the Ni content exceeds 3.0%, the strength of the weld metal may be increased to lower the low temperature toughness and CTOD toughness.

Titanium (Ti): 0.1 to 0.4%

Ti (metal Ti) acts as a nucleation site in the weld metal by bonding with oxygen to form a fine Ti complex oxide. The Ti complex oxides grow to refine the weld metal structure, thereby improving the impact resistance at low temperature and lowering the crack sensitivity . In order to obtain such a fine Ti composite oxide effect, it is preferable to set the content of Ti (metal Ti) to 0.1 to 0.4%. If the content of Ti (metal Ti) is less than 0.1%, the effect of refinement of the weld metal solidification structure through Ti composite oxides is small since the content of Ti (metal Ti) to react with oxygen of the oxide is small, The cracking resistance is lowered. If it exceeds 0.4%, the strength of the weld metal is increased due to the increase of the content of Ti (metal Ti) in the weld metal, so that the low-temperature impact toughness is lowered and the crack generation is increased.

Boron (B): 0.005 to 0.025%

Boron (B) may be added as a trace element to refine the structure and inhibit grain boundary ferrite growth, thereby improving the low temperature impact toughness and the low temperature CTOD characteristics. If the boron (B) is less than 0.005%, the effect of making the structure finer is not realized. If the boron (B) is more than 0.025%, the hardness of the weld portion is excessively increased to cause cracking.

SiO ₂ : 0.1 to 0.4%

SiO ₂ is added as a slag forming agent to improve the slag peelability and weld bead appearance. If the content of SiO ₂ is less than 0.1%, the viscosity of the slag becomes insufficient and the flapability of the slag deteriorates. At the same time, the appearance of the beads deteriorates. When the SiO _{2 content} exceeds 0.4%, the viscosity of the molten slag becomes excessively high to degrade the slag fluidity, So that cracking resistance and low-temperature impact toughness can be lowered.

Al ₂ O ₃ : 0.1 to 0.3%

Al ₂ O ₃ is added to prevent bead sagging in the bead appearance and in the upward and upward posture welding in the downward position welding. When the content of Al ₂ O ₃ is less than 0.1%, the bead appearance is lowered in the downward welding, and the bead sagging occurs in the upward-facing upward welding, thereby lowering the overall welding workability. On the other hand, if in excess of 0.3%, so a problem in that the slag removability deteriorated, in the present invention, Al ₂ O ₃ · It is preferable to limit the content to a range of 0.1 to 0.3%.

ZrO ₂ : 0.1 to 0.4%

ZrO ₂ is a component that influences the shape of the weld bead. In the present invention, the content of ZrO ₂ is preferably 0.1 to 0.4%. If the content is less than 0.1%, a good weld bead can not be obtained at the time of downward and horizontal fillet welding. If the content exceeds 0.4%, the bead uniformity decreases in the horizontal fillet welding, and the weld bead becomes convex at the time of top- to be.

In addition to the above composition, the remainder includes Fe in the steel shell, iron in the flux, and inevitably added impurities, which does not exclude the addition of other components.

Further, the wire of the present invention is a flux-filled wire in which a flux is filled in a metal sheath, wherein the fill factor is preferably in the range of 10 to 20%.

On the other hand, the inventors of the present invention have recognized through research that the formation of fine needle-shaped ferrite in the weld metal should be promoted in order to obtain good low temperature impact toughness and excellent CTOD characteristics. The acicular ferrite is formed through the nucleation of the Ti complex oxide produced by the reaction of Ti and oxides. It is known that the weld metal microstructure improves the impact resistance at low temperature and improves resistance to cracking. In order to accelerate the formation of acicular ferrite microstructure in the weld metal, it is possible to control the content of C by increasing the content of C in the weld metal. The higher the C content in the weld, the better the low temperature toughness in the weld metal and increase the acicular ferrite fraction, Sensitive bainite and martensite fractions are reduced.

In this connection, the present inventors have found that the present invention has the best low-temperature impact toughness and low-temperature CTOD characteristics when the content ratio of oxides, Ti and C is within a specific range, and exhibits good welding workability, 1, respectively.

[Relation 1]

The wire of the present invention is preferably formed such that the L value defined by the above-mentioned relational expression 1 satisfies 1.00 to 1.30. If the L value is less than 1.0, the Ti content affecting the formation of the Ti composite oxide in the weld metal is excessively increased, so that the strength and hardness of the weld metal are increased and the crack generation sensitivity of the weld metal is increased, And low-temperature CTOD characteristics are deteriorated. And the content of the oxide is decreased, thereby deteriorating the welding workability. If the value of L is more than 1.30, the content of Ti for forming Ti oxides in the weld metal is decreased, so that the percentage of the needle-like ferrite in the weld metal decreases and low temperature impact toughness and low temperature CTOD characteristics are deteriorated. So that the welding workability may be deteriorated.

In order to confirm the change of the low-temperature impact toughness according to the change of the L value of the relational expression 1, the inventors of the present invention conducted experiments for evaluating the weld metal impact toughness at -60 캜 according to the change of the L value by varying the contents of oxides and Ti, And a 40 占 폚 CTOD evaluation was performed. When the L value satisfies 1.00 to 1.60, excellent low temperature impact toughness and low temperature CTOD characteristics can be confirmed.

Specifically, FIG. 1 is a graph showing the correlation between the L value of the relational expression 1 and the -60 캜 low temperature impact value. Referring to FIG. 1, it can be seen that the L value and the low temperature impact value are similar to each other, and it can be confirmed that the energy absorbing shock is high at the value of the relation L value of 1.00 or more and 1.30 or less. That is, the range of the L value can find the optimal L value range that can increase the low temperature toughness of the material.

Hereinafter, the present invention will be described in detail by way of examples.

(Example)

And a flux-charging wire for gas shielded arc welding having a diameter of 1.2 mm and having the composition shown in Table 1 below was provided. In the wire composition of Table 1, the non-base component is Fe in the steel shell, iron in the flux and inevitable impurities. Table 2 shows the composition of the steel sheath used at this time.

Each of the wires thus prepared was welded to an API 5L 2W60 steel having a thickness of 80 mm in an upward and upright posture. At this time, the base material was modified V-shaped butt welding, and the specific welding conditions are shown in Table 3 below.

After performing such welding, the welding workability, toughness and cracking of each weld, and CTOD results were measured for each wire, and the results are shown in Table 4 below. On the other hand, in the present embodiment, the welding workability was evaluated visually in consideration of bead shape and the like and classified into four stages of excellent (⊚), excellent (◯), normal (△), and poor (x). In addition, the impact test was carried out at -60 ° C and the results were shown. The CTOD test was carried out at -40 ° C in accordance with BS7448, and the CTOD value of 0.25 mm or more was indicated as acceptable. Are shown in Table 4 below .

division TiO2 C Ti Si Mn B Ni ZrO2 SiO2 Al2O3 L Inventory 1 6.53 0.10 0.16 0.28 1.70 0.014 2.32 0.24 0.12 0.10 1.17 Inventory 2 7.05 0.01 0.15 0.30 1.65 0.014 0.56 0.10 0.18 0.13 1.01 Inventory 3 9.03 0.20 0.35 0.23 1.75 0.012 1.32 0.35 0.30 0.30 1.22 Honorable 4 6.50 0.05 0.39 0.20 1.20 0.021 1.00 0.30 0.28 0.20 1.10 Inventory 5 8.06 0.11 0.23 0.12 1.00 0.016 0.78 0.25 0.26 0.10 1.20 Inventory 6 9.20 0.07 0.15 0.65 2.13 0.009 1.52 0.16 0.21 0.15 1.11 Honorable 7 4.26 0.12 0.20 0.26 1.62 0.015 2.23 0.20 0.13 0.12 1.15 Honors 8 7.33 0.16 0.24 0.41 1.59 0.019 2.43 0.32 0.23 0.22 1.28 Proposition 9 9.21 0.14 0.32 0.95 1.73 0.020 2.52 0.24 0.35 0.21 1.16 Inventory 10 5.88 0.13 0.26 0.32 1.21 0.018 1.39 0.23 0.25 0.10 1.19 Exhibit 11 6.75 0.06 0.36 0.26 2.42 0.013 2.62 0.31 0.40 0.10 1.23 Inventory 12 7.29 0.04 0.11 0.25 1.63 0.006 2.12 0.21 0.16 0.20 1.25 Inventory 13 8.23 0.15 0.30 0.30 1.60 0.015 0.35 0.25 0.20 0.30 1.09 Inventory 14 9.26 0.06 0.20 0.28 1.43 0.009 1.56 0.23 0.32 0.22 1.24 Honorable Mention 15 6.95 0.10 0.23 0.93 1.15 0.016 1.88 0.35 0.11 0.20 1.18 Comparative Example 1 5.36 0.16 0.23 0.28 1.35 0.013 1.62 0.38 0.35 0.20 1.54 Comparative Example 2 8.23 0.15 0.30 0.25 1.55 0.011 2.12 0.10 0.12 0.13 0.81 Comparative Example 3 9.03 0.19 0.35 0.23 2.21 0.012 1.32 0.15 0.15 0.11 0.88 Comparative Example 4 5.53 0.06 0.12 0.20 1.20 0.012 1.00 0.30 0.28 0.23 1.64 Comparative Example 5 6.25 0.16 0.25 0.12 1.00 0.016 0.20 0.25 0.26 0.10 1.24 Comparative Example 6 9.20 0.30 0.15 0.65 1.85 0.020 1.52 0.16 0.21 0.15 1.21 Comparative Example 7 5.36 0.21 0.32 0.32 1.62 0.011 1.56 0.06 0.08 0.03 0.74 Comparative Example 8 6.23 0.16 0.30 0.72 1.23 0.013 1.63 0.53 0.63 0.42 1.73 Comparative Example 9 10.36 0.10 0.35 0.95 1.05 0.020 1.62 0.18 0.35 0.21 1.04 Comparative Example 10 5.88 0.13 0.52 0.32 1.12 0.022 1.39 0.23 0.25 0.10 0.95 Comparative Example 11 6.75 0.06 0.35 0.26 2.16 0.035 2.83 0.31 0.40 0.10 1.24 Comparative Example 12 7.29 0.04 0.14 0.63 1.63 0.018 3.86 0.21 0.16 0.20 1.19 Comparative Example 13 8.23 0.15 0.30 0.16 2.95 0.023 1.65 0.25 0.20 0.30 1.09 Comparative Example 14 9.26 0.06 0.20 1.26 1.43 0.009 2.10 0.23 0.32 0.22 1.24 Comparative Example 15 7.76 0.02 0.05 0.93 1.36 0.016 2.20 0.26 0.15 0.15 1.45

division C Si Mn P S Fe content 0.030 0.04 0.22 0.007 0.004 Remainder

Base material Root gap Improvement angle Lamination electric current Voltage Welding speed Heat input Welding posture API 2W Gr.60, 80 mmt 6 mm 60 degrees 41pass 220A 26V 10 to 30 cm / min 11 to 33 kJ / cm Orientation Sangjin
(V-UP)

division CTOD (@ - 40 ° C) And @ -60 ℃
(Joules) Whether cracks have occurred Weldability Overall assessment Inventory 1 pass 120 Not occurring ◎ ◎ Inventory 2 pass 81 Not occurring ○ ○ Inventory 3 pass 92 Not occurring ○ ○ Honorable 4 pass 95 Not occurring ○ ○ Inventory 5 pass 100 Not occurring ○ ○ Inventory 6 pass 97 Not occurring ○ ○ Honorable 7 pass 120 Not occurring ◎ ◎ Honors 8 pass 82 Not occurring ○ ○ Proposition 9 pass 125 Not occurring ○ ○ Inventory 10 pass 105 Not occurring ○ ○ Exhibit 11 pass 90 Not occurring ○ ○ Inventory 12 pass 85 Not occurring ◎ ◎ Inventory 13 pass 91 Not occurring ○ ○ Inventory 14 pass 87 Not occurring ○ ○ Honorable Mention 15 pass 110 Not occurring ◎ ◎ Comparative Example 1 0.13 64 Not occurring ○ △ Comparative Example 2 0.10 54 Not occurring × × Comparative Example 3 0.12 60 Not occurring × × Comparative Example 4 0.08 48 Not occurring ○ △ Comparative Example 5 0.02 41 Cracking ○ × Comparative Example 6 0.12 56 Cracking × × Comparative Example 7 0.03 50 Not occurring × × Comparative Example 8 0.06 45 Not occurring × × Comparative Example 9 0.12 82 Not occurring × × Comparative Example 10 0.05 75 Not occurring ○ × Comparative Example 11 0.13 50 Cracking ○ △ Comparative Example 12 0.11 55 Cracking ○ × Comparative Example 13 0.13 39 Not occurring × × Comparative Example 14 0.16 42 Not occurring × × Comparative Example 15 0.18 66 Not occurring ○ △

As shown in Tables 1 and 4, each of the flux-cored wires for gas shield arc welding according to Inventive Examples 1-15, in which the compositional composition of the wire satisfies the range of the present invention, shows excellent low temperature impact toughness and CTOD characteristics .

On the other hand, in the case of Comparative Example 10-15 in which the L value of the formula 1 deviates from the range of the present invention and the content of Ti is out of the range of the present invention, the low temperature impact toughness and the CTOD characteristics were poor. Also, in the case of Comparative Examples 7-8 in which the content and L value of ZrO ₂ , SiO ₂ and Al ₂ O ₃ were out of the range of the present invention, the welding workability was lowered and the low temperature impact toughness and CTOD characteristics were also not preferable.

In the case of Comparative Examples 5 to 12, the L value of the relational expression 1 satisfied the range of the present invention, but the content of Ni was out of the scope of the present invention, and the low temperature impact toughness and CTOD characteristics were lowered and cracks occurred, The content of Si and Mn is out of the range of the present invention, and the low temperature impact toughness and the CTOD characteristics are lowered, and the welding workability is not preferable.

In Comparative Example 1-4, the content of each component satisfies the range of the present invention, but the L value of the relational expression 1 is out of the scope of the present invention, so that the low-temperature impact toughness and the CTOD characteristics are deteriorated, and the welding workability is also undesirable .

On the other hand, Fig. 2 (a-c) is a photograph of the weld metal in a case where the low temperature impact toughness and the CTOD characteristics are insufficient and in a good case.

Specifically, Fig. 2 (a) is a photograph of the structure of Comparative Example 7, which shows that when the L value of the relational expression 1 is out of the range of the present invention, the percentage of needle-like ferrite microstructure is low and the fraction of bainite and martensite microstructure is high And the low temperature impact toughness and CTOD characteristics are insufficient.

On the other hand, FIG. 2 (bc) is a photograph of the weld metal of the weld metal for Inventive Example 1 and Inventive Example 7, respectively, when the L value of the relational expression 1 falls within the range of the present invention, and the percentage of the needle-like ferrite microstructure is high, It is possible to know a structure having excellent impact toughness and excellent CTOD characteristics.

While the present invention has been particularly shown and described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of course, this is possible. Therefore, the scope of the present invention should not be limited to the above-described embodiments but should be defined by the following claims as well as equivalents thereof.

Claims (2)

The flux-filled wire is filled with a flux in a metal shell. The wire is composed of 4.0 to 9.5% of TiO ₂ , 0.01 to 0.20% of C, 0.1 to 1.0% of Si, 0.1 to 1.0% of Si, 0.1 to 0.4% of ZrO ₂ , 0.1 to 0.4% of SiO ₂ , 0.1 to 0.3% of Al ₂ O ₃ , and 0.005 to 0.3% of B, 0.025%, balance Fe and unavoidable impurities, and has an L value defined by the following relational expression 1 satisfying the range of 1.00 to 1.30.
[Relation 1]

The flux-charging wire for gas shield arc welding according to claim 1, wherein the filling rate of the flux is in the range of 10 to 20%.

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