KR101859373B1 - Titania Based Flux Cored Wire of Gas Shielded Arc Welding for Low Temperature Service - Google Patents

Abstract

A titania-based flux-charging wire for gas shielded arc welding is provided which is excellent in low temperature impact toughness.
A flux-filling wire in which a flux is filled in a metal sheath is characterized by comprising 0.02 to 0.07% of C, 0.1 to 0.5% of Si, 0.3 to 1.5% of Mn, , B: 0.002 ~ 0.007%, Ni: 2.5 ~ 4.5%, Mg: 0.4 ~ 1.0%, TiO 2: and _{4.0 ~ 9.5%, SiO 2:} 0.1 ~ 0.4%, Al 2 O 3: 0.1 ~ 0.4%, Ti : 0.1 to 0.4%, the balance iron, iron powder and unavoidable impurities, and the F value defined by the relationship 1 satisfies 0.3 to 0.5.

Description

Title: Titania Based Flux Cored Wire for Gas Shielded Arc Welding for Low Temperature Shock Arc Toughness -

TECHNICAL FIELD The present invention relates to a flux filling wire for titania-based welding, and more particularly, to a flux-charging wire for gas shielded arc welding which is excellent in weldability, crack resistance and low temperature impact toughness at 25 kJ / cm or more.

Recently, as the development of energy source has been extended from the offshore area to deep sea and polar regions, drying of gas carriers and the like has been increasing. Accordingly, it is desired to develop a welding material capable of welding in accordance with the manufacturing of such ships. Generally, the flux-filling wire which occupies the largest portion among the welding materials used in the shipyard is excellent in workability and work efficiency, but has a disadvantage in that it is poor in low-temperature impact toughness and cracking resistance to be applied to the above-mentioned extreme places.

When the heat input is increased, the structure coarsening leads to deterioration of low temperature impact toughness. While the heat input corresponding to approximately 7 to 22 kJ / cm is widely used in the welding with the flux-charging wire, a columnar structure is formed on the welded portion when 22 to 30 kJ / cm is used, The formation of coarse columnar phase and intergranular ferrite deteriorates the microstructure of the weld metal and low temperature impact toughness and crack resistance of the weld metal are weakened.

Korean Patent Laid-Open Publication No. 2002-0008681 proposes to secure a good low-temperature impact toughness and an improvement in welding workability by controlling the ratios of titanium oxide and non-titanium oxide, but it is somewhat insufficient in terms of crack resistance, No mention is made.

Korean Patent Laid-Open Publication No. 1999-0015625 discloses improvement in welding workability and impact resistance at low temperatures by limiting the content of TiO ₂ , Mg, Mn, B, Si, Nb, V, Korean Patent Laid-Open Publication No. 2002-8681 discloses a flux-charging wire for improving the cryogenic impact value by limiting the sum of C, Mn, Si, B, Al, Ni, F, titanium oxide and bicarbonate. However, the above-mentioned prior arts are insufficient in securing stable impact toughness and crack resistance due to high heat welding at a very low temperature.

Therefore, there is a demand for the development of a flux-charging wire having excellent weldability and low-temperature impact resistance and crack resistance at welded metal even at a heat input of 25 kJ / cm or more in a high heat input range.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a flux-charging wire for gas-shielded arc welding which is excellent in weldability, resistance to cracking and low-temperature impact toughness at high temperature welding in flux- It has its purpose.

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-charging wire according to any one of claims 1 to 3, wherein the flux-filled wire is filled with a flux in a metal sheath. , Ni: 2.5 ~ 4.5%, Mg: 0.4 ~ 1.0%, TiO 2: and _{4.0 ~ 9.5%, SiO 2:} 0.1 ~ 0.4%, Al 2 O 3: 0.1 ~ 0.4%, Ti: 0.1 ~ 0.4%, the balance Iron, iron powder and inevitable impurities, and satisfies an F value of 0.3 to 0.5 as defined by the following relational expression (1).

 [Relation 1]

The present invention having the above-described constitution can control the compositional components of the flux-filling wire and control the compositional relationship between them to provide a titania-based flux charging wire for gas shielded arc welding having excellent crack resistance and low- Can be effectively provided.

Namely, it is possible to provide a titania-based flux charging wire having excellent crack resistance and low-temperature impact toughness by restricting the content ratio of Ni, Mn, C, Ti, B, SiO ₂ and Al ₂ O ₃ to appropriate values.

1 is a view showing a shape of a welding base material for a crack test according to the present invention.
2 is a graph showing the correlation between the F value in the above-mentioned relational expression 1 and the low temperature impact value of -60 캜.

Hereinafter, the present invention will be described in detail.

In the present invention, by adding Ni and Mn among the components in the flux-packed wire, the impact resistance at low temperatures and crack resistance are improved. The inventors of the present invention focused on the content of Ni and Mn by converting the range into a logarithmic value in view of the fact that low temperature impact toughness and crack resistance can be ensured in high temperature heat welding.

In addition, even when welding with high heat, Ti forms Ti complex oxide to increase impact toughness by increasing needle-shaped ferrite structure in the microstructure of the weld metal. B segregates in the austenite grain boundary to suppress the formation of intergranular ferrite, Thereby improving the toughness of the welded portion.

In addition, the present invention minimizes the crack sensitivity by increasing the fraction of δ-ferrite through an appropriate level of C content. As δ-ferrite increases, the degree of solubility to employ low-melting inclusions such as FeS and Fe ₃ P is increased and cracks can be prevented.

In an appropriate range of SiO ₂ and Al ₂ O ₃ classified as other oxides, the weldability can be improved within a range that does not cause impact toughness and crack resistance.

From the above viewpoints, the present inventors have derived the following relational expression 1, and confirmed that when the value defined by the relational expression 1 satisfies a predetermined range, low temperature impact toughness and crack resistance can be ensured at high heat welding The invention is presented.

The titania flux-charging wire for gas shielded arc welding according to the present invention comprises 0.02 to 0.07% of C, 0.1 to 0.5% of Si, 0.3 to 1.5% of Mn, 0.001 to 0.007 of B, %, Ni: 2.5 ~ 4.5% , Mg: 0.4 ~ 1.0%, TiO 2: and _{4.0 ~ 9.5%, SiO 2:} 0.1 ~ 0.4%, Al 2 O 3: 0.1 ~ 0.4%, Ti: 0.1 ~ 0.4%, Residual iron, iron powder and unavoidable impurities, and an F value defined by the following relational expression 1 satisfies 0.3 to 0.5.

 [Relation 1]

Hereinafter, the compositional components of the flux-filling wire of the present invention and the reasons for limitation thereof will be described in detail. The following composition components are% by weight based on the total weight of the wire.

Carbon (C): 0.02 to 0.07%

The carbon (C) is contained in the steel shell and the flux of the wire of the present invention, and serves to maintain the strength of the weld metal and to suppress generation of intergranular ferrite, thereby improving the impact resistance at low temperatures. Further, by forming an appropriate range of delta -ferrite, the solubility of the low melting point inclusions can be increased and the crack resistance can be improved.

In consideration of this, in the present invention, the content of carbon (C) is preferably limited to 0.02 to 0.07%. If the content of C is less than 0.02%, the toughness and tensile properties of the deposited metal deteriorate due to the lack of ingot. If the content of C exceeds 0.07%, the strength increases and the S- You can.

TiO ₂ : 4.0 to 9.5%

TiO ₂ is the main slag forming agent in welding and serves to protect the molten metal from the atmosphere. When the content is less than 4.0%, the effect is insignificant and the slag-like property is lowered. When the content is more than 9.5%, solidification is accelerated and slag detachment and fluidity are deteriorated. Therefore, in the present invention, the content of TiO ₂ is preferably limited to 4.0 to 9.5%.

Mn: 0.3 to 1.5%

Mn reacts with S as a relatively weak deoxidizing agent to form MnS first than FeS, so that formation of a low melting point compound due to S segregation can be prevented.

In the present invention, it is preferable that the Mn content is limited to 0.3 to 1.5%. If the content is less than 0.3%, the strength of the weld metal is lowered and the coarsening of the weld metal is accelerated due to insufficient penetration. If it exceeds 1.5%, the meltability is lowered, the sludge solidification becomes slower, the bead appearance becomes worse, and the strength and impact toughness of the welded portion may be lowered.

Si: 0.1 to 0.5%

Si reduces the amount of oxygen in the weld metal, maintains the strength of the weld metal, and improves slag fluidity and bead appearance when added in an appropriate amount. If the content of Si is less than 0.1%, the tensile strength and impact toughness of the weld metal deteriorate and the bead appearance improving effect is insufficient. If the content of Si is less than 0.1%, the slag fluidity decreases, impact toughness decreases, Therefore, the content thereof is preferably 0.1 to 0.5%.

Ni: 2.5 to 4.5%

Ni is an element capable of stabilizing the transition temperature of the impact toughness and stabilizing the low temperature impact toughness with the deposited metal austenite stabilizing element, and the content range thereof is preferably set to 2.5 to 4.5%. If the Ni content is less than 2.5%, the effect of stabilizing low-temperature impact toughness can not be exhibited at the time of welding with high heat. If it exceeds 4.5%, the saturation solubility of Ni is decreased to increase the possibility of cracking, I can do it.

Mg: 0.4 to 1.0%

Mg reacts with oxygen in the molten metal as a strong deoxidizing agent to suppress the generation of non-metallic inclusions, thereby improving the cleanliness of the weld metal. However, if the content is less than 0.4%, the effect of the addition can not be expected. If the content is more than 1.0%, the amount of welding fume and spatter is increased and the flapability of the slag is deteriorated. Limitations are desirable.

Ti (metal Ti): 0.1 to 0.4%

Ti (metal Ti) combines oxygen and C, Mn, B to form a fine Ti composite oxide, which serves as a nucleation site in the weld metal. The titanium composite oxides are grown to refine the weld metal structure to improve the impact resistance at low temperature and lower the cracking sensitivity. In order to obtain the effect of the fine Ti complex oxide, the content of Ti (metal Ti) is preferably set to 0.1 to 0.4%. If the content of Ti (metal Ti) is less than 0.1%, the effect of refining the solidification structure of the weld metal through the Ti composite oxides under the high heat input condition is small because the content of Ti (metal Ti) The impact strength and crack resistance at low temperatures are deteriorated. If the Ti content exceeds 0.4%, the strength of the weld metal is increased due to an increase in the content of Ti (metal Ti) in the weld metal.

B: 0.002 to 0.007%

The purpose of the addition of B is to segregate in the austenite grain boundaries to inhibit the formation of intergranular ferrite and increase the strength and toughness of the welded portion by making the structure finer. In the present invention, the content of B is preferably limited to 0.002 to 0.007%. If the content is less than 0.002%, the impact toughness effect is not exhibited under high heat input conditions. When the content exceeds 0.007%, boride is formed into a continuous network, And the toughness is deteriorated as well as the melting property and cracking may occur.

Al ₂ O ₃ : 0.1 to 0.4%

Al ₂ O ₃ is added to improve the bead spreadability in the bidirectional upright posture 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, so that the overall welding workability may be deteriorated. On the other hand, if it exceeds 0.4%, the slag releasing property and the impact toughness due to the high melting point oxide are lowered, so that the content thereof is preferably limited to the range of 0.1 to 0.4%.

SiO ₂ : 0.1 to 0.4%

SiO ₂ improves slag fluidity and bead shape. In the present invention, it is preferable to limit the content of SiO ₂ to 0.1 to 0.4%. If the content of SiO ₂ is less than 0.1%, the slag viscosity lowers and the slag flow, bead appearance and peelability deteriorate. On the other hand, if it exceeds 0.4%, the MA constituent and secondary phase transformation in the weld metal are promoted, and the impact resistance at low temperatures can be lowered.

The filler wire of the present invention includes Fe in the steel shell, iron in the flux, and inevitably added impurities in addition to the above composition, and does not exclude the addition of other components.

In the present invention, in view of the impact on impact toughness and cracking, the following relation 1 is derived in consideration of the degree of contribution of each element to the formation of acicular ferrite.

[Relation 1]

Specifically, in the present invention, the content of Ni, Mn, C, Ti, B, SiO _2, and Al ₂ O ₃ is set so that the value defined by F in relation 1 is in the range of 0.3 to 0.5 in terms of ensuring improvement in low temperature impact toughness and crack resistance. And a control unit.

If the value F defined by the above-mentioned relational expression 1 is less than 0.3, fine needle-like ferrite can not sufficiently be generated in the heat-welded weld metal. The needle-like ferrite can exert its effect by the presence of intrinsic elements such as Ni and Mn in the proper range and C and B contents. In addition, it is possible to improve the low-temperature impact toughness through nucleation of the Ti composite oxide.

However, the increase of SiO ₂ and Al ₂ O 3 promotes the MA constituent and secondary phase transformation in the weld metal due to the formation of a high melting point oxide, thereby lowering the impact resistance at low temperatures. If the range exceeds 0.5, the strength and hardness are increased during welding at high heat, transformation to bainite and martensite structure can be induced to promote cracking, and the impact toughness is lowered. Therefore, SiO ₂ and Al ₂ O ₃ oxides can improve the weldability, but they may cause impact toughness and cracking, so an appropriate range is needed.

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

(Example)

And a 1.4 m diameter titania flux-charging wire filled with a flux having a composition component as shown in Table 1 below at a filling rate of 10% to 20%, respectively. At this time, as the steel shell, a soft steel material containing 0.03% of C, 0.002% of Si, 0.20% of Mn, 0.010% of P, 0.008% of S, and the balance iron and unavoidable impurities Respectively. Each of the wires thus prepared was subjected to one-side welding (downward welding) on the EH36 steel having the shape as shown in Fig. 1 under the welding conditions shown in Table 2 below, and the presence or absence of cracks on the surface of the beads was confirmed. The heat input was carried out within the range of 25 to 30 kJ / cm.

division
The flux composition component (% by weight) F
C Si Mn B Ni Mg TiO ₂ SiO ₂ Al ₂ O ₃ Ti Inventory 1 0.024 0.16 0.8 0.0053 3.5 0.55 5.4 0.35 0.32 0.35 0.35 Inventory 2 0.065 0.33 0.8 0.0024 3.8 0.44 4.2 0.38 0.29 0.26 0.37 Inventory 3 0.041 0.25 0.4 0.0036 3.5 0.82 8.4 0.26 0.34 0.37 0.47 Honorable 4 0.051 0.43 1.5 0.0035 3.8 0.59 9.5 0.14 0.18 0.12 0.30 Inventory 5 0.058 0.11 1.5 0.0024 4.1 0.78 5.2 0.32 0.35 0.28 0.32 Inventory 6 0.048 0.21 1.2 0.0068 3.5 0.93 6.8 0.19 0.38 0.24 0.42 Honorable 7 0.035 0.23 0.4 0.0059 2.6 0.41 8.1 0.29 0.18 0.35 0.42 Honors 8 0.062 0.42 0.5 0.0048 4.4 0.68 9.3 0.25 0.43 0.13 0.45 Proposition 9 0.039 0.48 1.2 0.0068 3.3 0.72 4.6 0.11 0.28 0.35 0.50 Inventory 10 0.042 0.25 0.9 0.0042 4.1 0.65 6.3 0.38 0.35 0.28 0.42 Exhibit 11 0.039 0.45 0.4 0.0048 3.1 0.44 8.2 0.38 0.12 0.15 0.32 Inventory 12 0.034 0.15 1.5 0.0036 4.3 0.71 6.8 0.32 0.42 0.39 0.36 Inventory 13 0.068 0.38 0.4 0.0042 2.6 0.83 4.0 0.28 0.21 0.15 0.32 Inventory 14 0.045 0.42 0.9 0.0048 3.4 0.65 7.2 0.33 0.36 0.38 0.43 Comparative Example 1 0.015 0.38 0.5 0.0062 3.6 0.75 5.5 0.15 0.28 0.39 0.45 Comparative Example 2 0.085 0.15 0.4 0.0052 3.2 0.83 6.2 0.32 0.39 0.36 0.67 Comparative Example 3 0.054 0.26 0.1 0.0042 2.9 0.92 8.4 0.28 0.15 0.4 0.65 Comparative Example 4 0.041 0.23 1.8 0.0063 3.6 0.68 7.9 0.32 0.35 0.15 0.19 Comparative Example 5 0.052 0.32 1.4 0.0072 2.7 0.48 9.2 0.34 0.21 0.38 0.18 Comparative Example 6 0.068 0.48 0.3 0.0018 3.4 0.52 4.8 0.39 0.39 0.21 0.28 Comparative Example 7 0.056 0.34 1.0 0.0061 2.3 0.65 6.4 0.21 0.11 0.19 0.16 Comparative Example 8 0.028 0.46 1.2 0.0041 4.8 0.54 5.3 0.19 0.24 0.24 0.45 Comparative Example 9 0.052 0.13 1.1 0.0023 3.9 0.54 5.2 0.07 0.19 0.12 0.33 Comparative Example 10 0.069 0.29 0.6 0.0041 4.1 0.63 6.3 0.54 0.26 0.28 0.54 Comparative Example 11 0.027 0.4 0.9 0.0035 3.8 0.72 5.4 0.36 0.06 0.14 0.26 Comparative Example 12 0.038 0.35 0.5 0.0068 4.2 0.88 6.2 0.18 0.45 0.26 0.59 Comparative Example 13 0.021 0.23 1.3 0.0036 4.4 0.49 4.1 0.23 0.33 0.07 0.15 Comparative Example 14 0.048 0.32 0.8 0.0048 2.8 0.53 4.9 0.15 0.32 0.52 0.48 Comparative Example 15 0.038 0.25 1.4 0.0068 3.1 0.93 6.4 0.34 0.23 0.28 0.26 Comparative Example 16 0.029 0.38 0.4 0.0059 3.7 0.41 8.1 0.29 0.31 0.35 0.52 Comparative Example 17 0.041 0.31 0.8 0.0048 3.6 0.65 7.3 0.27 0.16 0.38 0.59 Comparative Example 18 0.023 0.39 0.5 0.0028 2.8 0.84 6.8 0.12 0.21 0.19 0.22

* The remainder is iron powder and unavoidable impurities.

And F is the relational expression 1.

Protective gas and flow rate polarity Welding posture Welding current / voltage Heat input Other 100% CO ₂
(20 ~ 25L) / min DC reverse polarity
(DC +) Downward (1G) 270A / 32V 25 to 30 kJ / cm Improved angle: 34 °
Root Gap: 5mm
Stick Out: 20 ~ 25mm
Welding method: retraction method

On the other hand, impact toughness and weldability of weld metal due to high heat welding are evaluated and shown in Table 4 below. As shown in Table 3, the impact toughness of the weld metal was FH36, a low temperature steel used in shipbuilding and marine applications. The thickness was 15T, the angle of improvement was 34 °, and the root gap was 5 ~ 6mm. The range of welding heat input was 25 ~ 30kJ / cm and the number of welding pass was 3pass. The impact strength of the weld metal obtained after the test was evaluated to be acceptable when the impact strength value was more than 47 J (Joule) at 60 ° C.

The weldability was evaluated through bead spreadability, meltability, slag peelability and arcability. The results are also shown in Table 4 below. In this experiment, weldability was evaluated visually in consideration of the shape of beads and evaluated in four stages of excellent (⊚), excellent (◯), normal (△), and poor (Ⅹ).

Base material Root gap Improvement angle electric current Voltage Number of layers Heat input Welding posture FH36 5 ~ 6mm 34 ° 220A 26V 3Pass 25 to 35 kJ / cm Orientation Sangjin
(3G-UP)

division @ @ -60 [deg.] C (J) Whether cracks have occurred Weldability Overall assessment





Honor





One 83 No crack occurred ○ ○ 2 64 No crack occurred ◎ ◎ 3 71 No crack occurred ○ ○ 4 59 No crack occurred ○ ○ 5 93 No crack occurred △ ○ 6 89 No crack occurred △ ○ 7 65 No crack occurred △ ○ 8 95 No crack occurred ◎ ◎ 9 88 No crack occurred ○ ○ 10 64 No crack occurred ○ ○ 11 82 No crack occurred ◎ ◎ 12 73 No crack occurred ○ ○ 13 60 No crack occurred ○ ○ 14 72 No crack occurred ◎ ◎







Comparative Example







One 12 Cracking △ × 2 58 Cracking ○ △ 3 39 Cracking △ × 4 31 No crack occurred ◎ △ 5 70 Cracking ○ △ 6 13 No crack occurred ◎ × 7 22 No crack occurred △ × 8 52 Cracking △ △ 9 58 No crack occurred × △ 10 20 Cracking ○ × 11 24 No crack occurred × × 12 19 Cracking ◎ × 13 14 No crack occurred △ × 14 39 Cracking ◎ × 15 38 Cracking △ × 16 34 Cracking ◎ × 17 41 Cracking △ × 18 12 Cracking △ ×

As can be seen from Table 4, the flux-cored wire for gas shield arc welding according to Inventive Examples 1 to 14 satisfying the range of the present invention exhibits excellent low-temperature impact toughness, crack resistance and weldability characteristics .

 On the other hand, in Comparative Example 1-2, the C content exceeded the appropriate range and the impact toughness and crack resistance were lowered. The Mn content in Comparative Example 3-4 and the Ni content in Comparative Example 7-8 were out of the appropriate ranges, and the impact toughness and crack resistance were lowered.

In addition, in Comparative Example 5-6, when the penetration type element B content exceeded the appropriate range, the impact toughness was good but the crack resistance was insufficient. In the case of under-toughness, the crack resistance was good but the impact toughness was inadequate have.

In the case of Comparative Example 11-12, the Al ₂ O ₃ content was out of the appropriate range, and the weldability and impact toughness were lowered. In Comparative Example 9, the F value of the relational expression 1 satisfied the range of the present invention, but the content of SiO ₂ was too small to significantly decrease the weldability. In Comparative Example 10, the SiO ₂ content was high, have.

In Comparative Example 13, the low-temperature impact toughness was lowered due to the low Ti content because the composite oxide was not formed. In Comparative Example 14, the Ti content was high and the low temperature impact toughness and crack resistance were decreased have.

On the other hand, in the case of Comparative Examples 15, 16, 17, and 18, the content of each component satisfies the range of the present invention, but the F value of the relational expression 1 is out of the scope of the present invention and the low temperature impact toughness and crack resistance characteristics are deteriorated It can be confirmed that it is not preferable.

2 is a graph showing the correlation between the F value of the above-mentioned relational expression 1 and the -60 캜 low temperature impact value. As shown in FIG. 2, when the flux composition component and the F value satisfy the range of the present invention, it is found that the low temperature impact toughness is mostly good.

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 (1)

The flux-charging wire according to any one of claims 1 to 3, wherein the flux-filled wire is filled with a flux in a metal sheath. , Ni: 2.5 ~ 4.5%, Mg: 0.4 ~ 1.0%, TiO 2: and _{4.0 ~ 9.5%, SiO 2:} 0.1 ~ 0.4%, Al 2 O 3: 0.1 ~ 0.4%, Ti: 0.1 ~ 0.4%, the balance Iron, iron powder, and unavoidable impurities, and satisfies an F value of 0.3 to 0.5 as defined by the following relational expression (1).
[Relation 1]

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