KR20230068153A - Gas shield flux cored wire having good weldability - Google Patents

Abstract

A gas shielded flux-filled wire with excellent thin-plate weldability is provided.
The flux-filled wire of the present invention, by weight percent, TiO ₂ : 4.0 to 8.0%, C: 0.02 to 0.05%, Si: 0.40 to 0.80%, Mn: 1.50 to 3.00%, Mg: 0.10 to 0.50%, B : 0.001 ~ 0.020%, Nb: 0.010% or less, V: 0.010% or less, Na + K: 0.35 ~ 0.90%, F conversion amount among alkali and alkaline earth metal-based fluorine compounds: 0.01 ~ 0.10%, residual Fe and unavoidable impurities Including, the A value defined by relational expression 1 satisfies 0.5 to 0.8.

Description

Gas shield flux cored wire having good weldability

The present invention relates to a gas shield flux filling wire, and more particularly, a gas shield flux filling wire that is used for welding steel materials having a tensile strength of 490 MPa to 670 MPa as a welding base material and has excellent thin plate (≤10 mm) Auto Carriage automatic welding workability. It is about.

Korea is a shipbuilding powerhouse that has led the world's shipbuilding market since 2000. However, most of the shipbuilding industry is dominated by commercial vessels such as container ships, bulk carriers, and LNG carriers, while most of the largest coastal passenger ships, car ferries and high-speed ships, depend on imports. Most of the car ferries and high-speed boats brought into Korea were not newly built, but used boats that were more than 15 years old. Taking this accident as an opportunity, it was discussed carefully about bringing in and operating second-hand car ferries and high-speed boats that are over 15 years old and seeking new ones in Korea. In addition, looking at the outlook for future world passenger ship construction demand, the number of vessels increased from 22 in 2014 to 71 in 2020, with an average annual increase of 21.6%. The average annual growth rate is expected to be very high at 38.0%. In the case of such car ferries and high-speed ships, a relatively thin base material is used for drying for high-speed sailing, so a suitable welding leg length (≤5mm) is required, and in order to improve work efficiency, low current (≤180A) The trend is to weld with a single pass in the area. However, various studies have already been conducted for the purpose of securing a stable welding operation for commercial ships built using thick plates for gas shielded flux-filled wires with tensile strengths of 490 to 670 MPa that are sold on the market. can't go In other words, it is possible to secure the workability of the welding part of the thin plate (≤10mm) using the conventional gas shielded flux filling wire for Auto Carriage, but the stable workability of the vertical welding part cannot be secured, so a finishing process is required after welding.

On the other hand, Patent Literature 1 suggests that excellent weld metal can be obtained especially in thin plates (≤ 10 mm), although welding workability in all postures is excellent. However, in the gas shielded flux filling wire presented in Patent Document 1 described above, welding for low current welding to satisfy the leg length (≤5mm) required for car ferry and high-speed ship construction has not proceeded, and low current (≤ 180A) Welding workability (bead spreadability) to minimize the finishing process during upright welding was also lacking.

Republic of Korea Patent Publication No. KR2019-0086123

Accordingly, an object of the present invention is to provide a gas shielded flux-filled wire having excellent workability in a thin plate (≤10mm) and, in particular, excellent auto carriage single pass weldability in a low current (≤180A) region.

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 are clearly understood by those skilled in the art from the description below. It could be.

Therefore, one aspect of the present invention,

In the flux-filled wire in which the flux is filled in the metal sheath, by weight percent, TiO ₂ : 4.0 ~ 8.0%, C: 0.02 ~ 0.05%, Si: 0.40 ~ 0.80%, Mn: 1.50 ~ 3.00%, Mg: 0.10 to 0.50%, B: 0.001 to 0.020%, Nb: 0.010% or less, V: 0.010% or less, Na + K: 0.35 to 0.90%, F conversion amount among alkali and alkaline earth metal-based fluorine compounds: 0.01 to 0.10%, A flux-filled wire for gas shielded arc welding having excellent thin-plate weldability, including residual Fe and unavoidable impurities, and having an A value defined by the following relational expression 1 of 0.5 to 0.8.

[Relationship 1]

The present invention configured as described above can effectively provide a gas shielded flux filling wire having excellent auto carriage single pass welding workability while providing an excellent welding part in a thin plate (≤10 mm).

Therefore, by using this, it is possible to effectively secure the weldability of the thin plate welded part used in the construction of the car ferry and the high-speed ship.

1 shows the cross-sectional shape of a bead in an upright posture in an Auto Carriage in a base material having a thickness of 6 mm using gas shielded flux-filled wires of Inventive Examples 2 and 5 and Comparative Examples 2 and 5 in an embodiment of the present invention.

Hereinafter, the present invention will be described.

An object of the present invention is to provide an excellent welding part in a thin plate (≤10 mm) and at the same time to provide a gas shielded flux-filled wire with excellent auto carriage single pass welding workability. Furnace, TiO ₂ : 4.0 ~ 8.0%, C: 0.02 ~ 0.05%, Si: 0.40 ~ 0.80%, Mn: 1.50 ~ 3.00%, Mg: 0.10 ~ 0.50%, B: 0.001 ~ 0.020%, Nb: 0.010% or less , V: 0.010% or less, Na + K: 0.35 to 0.90%, F equivalent in alkali and alkaline earth metal-based fluorine compounds: 0.01 to 0.10%, A value including residual Fe and unavoidable impurities, and defined by relational expression 1 It is formulated to satisfy this 0.5 to 0.8.

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 % by weight unless otherwise specified.

·TiO ₂ : 4.0~8.0%

TiO ₂ serves as an arc stabilizer and is a major component of the slag forming agent.

In addition, in the present invention, it is important to control the TiO ₂ content to secure excellent welding workability. If the TiO ₂ content is less than 4.0%, the slag solidification is lowered, making all-position welding, especially vertical-up welding difficult. On the other hand, if the content of TiO ₂ exceeds 8.0%, the melting point of the flux is increased, the amount of spatter generation is increased due to the decrease in meltability, and excellent bead spreadability cannot be secured.

Therefore, in the present invention, it is preferable to limit the TiO ₂ content to 4.0 to 8.0%.

·C: 0.02~0.05%

In the present invention, carbon is an austenite stabilizing element capable of securing the strength of the weld metal and the impact toughness of the weld metal. However, when the carbon content is low, since austenite is not stabilized, it is necessary to maintain an appropriate amount of carbon, so the lower limit is set to 0.02%. On the other hand, if the carbon content exceeds 0.05%, it is difficult to secure good workability such as occurrence of undercut in the base material due to increased arc concentration.

Considering this, in the present invention, it is preferable to limit the carbon (C) content to the range of 0.02 to 0.05%.

Si: 0.40~0.80%

In the present invention, when the content of silicon is less than 0.40%, the deoxidation effect in the weld metal part is insufficient and the flowability of the weld metal part is reduced, thereby reducing workability. On the other hand, if it exceeds 0.80%, the strength of the weld metal portion increases and the toughness decreases, which is not preferable.

Therefore, in the present invention, it is preferable to limit the content of silicon (Si) to 0.40 to 0.80%.

·Mn: 1.50~3.00%

In the present invention, Mn is an element that serves as a relatively weak deoxidizer and improves strength. Since MnS reacts with S to form MnS before FeS, it is effective in preventing high-temperature cracking by preventing the formation of low-melting compounds due to segregation of S.

In the present invention, it is preferable to limit the Mn content to 1.50 to 3.00%, which means that if the content is less than 1.50%, the deoxidation effect in the weld metal part is insufficient and the toughness is lowered. On the other hand, if it exceeds 3.00%, a low-temperature transformation structure is created, which is not preferable because crack resistance and toughness are rapidly lowered, strength is increased, and workability is also lowered due to a decrease in arc melting property.

·Mg : 0.10~0.50%

In the present invention, Mg, as a strong deoxidizing agent, reacts with oxygen in molten metal to suppress generation of non-metallic inclusions and improve the cleanliness of weld metal. However, if the content is less than 0.10%, the effect of the above content cannot be expected, and if it exceeds 0.50%, the cleaning effect is excessively increased, increasing the deposited metal transfer rate of other components together, increasing the amount of spatter, increasing the fluidity and Since the arc property is lowered, in the present invention, it is preferable to limit the content to 0.10 to 0.50%.

B (boron): 0.001 to 0.020%

B has an effect of improving notch toughness. If the B content is less than 0.001%, it is difficult to expect the addition effect, and if the B content exceeds 0.020%, the toughness improvement effect rapidly decreases, and at the same time, B aggregates between crystal grains to rapidly reduce hot crackability.

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

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

A trace amount of Nb or V is present in the raw material of TiO ₂ and may affect the crystal composition and mechanical properties of the weld metal. Nb and V, as elements added as impurities, precipitate at grain boundaries to increase weld strength by solid solution strengthening and affect toughness. Therefore, in the present invention, it is preferable to limit the contents of Nb and V to 0.010% or less and 0.010% or less, respectively.

Na + K: 0.35 to 0.90%

Alkali metals Na and K, which are classified as arc stabilizers, stabilize the arc during welding and bring about good workability. Therefore, in order to secure thin plate weldability in the present invention, alkali metal Na + K is important. If the content is less than 0.35%, the arc resistance decreases and workability decreases, and if it exceeds 0.90%, the amount of fume generated increases and welding It increases the oxygen content in the pubic area and lowers the toughness.

In the present invention, compounds containing TiO ₂ , SiO ₂ and the like in the oxide form of K ₂ O and Na ₂ O are used as the Na and K compounds.

F equivalent in alkali and alkaline earth metal fluorine compounds: 0.01 to 0.10%

Since the fluorine compound generates fluorine into the arc at a high temperature and reacts with hydrogen during welding to cause a dehydrogenation reaction, the diffusible hydrogen of the weld joint can be effectively lowered. However, if the amount of F in the fluorine compound is less than 0.01%, it is difficult to expect the above-mentioned effect, and if it exceeds 0.10%, the amount of fume generation is excessively increased, so the content range is limited to 0.01 to 0.10%.

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.

·Relational expression 1

The flux filling wire of the present invention satisfies all of the above-mentioned composition and at the same time, in order to provide excellent welding workability during Auto Carriage Single Pass welding in thin plates (≤10mm), the A value defined by the following relational expression 1 is 0.5 to 0.5 ~ It is characterized in that the Na + K, Mn, and Mg contents are controlled to satisfy the 0.8 range.

If the A value is less than 0.5, it is difficult to secure stable workability, especially in thin plate welding, due to deterioration in arc stability. On the other hand, if it exceeds 0.8, it is difficult to expect the impact toughness required in the present invention due to an increase in the amount of oxygen in the deposited metal due to the excessive addition of oxide.

[Relationship 1]

And, the flux-filled wire of the present invention contains Fe and unavoidable impurities as residual components, where Fe includes Fe in the metal sheath and Fe powder in the flux.

A flux-filled wire welding material according to an embodiment of the present invention is composed of a hoop made of mild steel as an outer shell and a flux charged inside the wire, and the weight ratio of the flux to the total weight of the flux-filled arc welding wire is 13.0 to 18.0%. can

By providing a welding material that satisfies the above alloy composition, etc., it is possible to secure excellent workability in thin plate (≤10mm) Auto Carriage Single Pass.

In addition, it can be seen that excellent workability can be secured from a welding bead obtained after welding using a flux-filled wire satisfying the above-described alloy composition, particularly in an upright posture.

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

(Example)

division No. TiO2 C Si Mn Mg B Nb V F Na+K A foot
number of people
yes One 4.9 0.032 0.45 2.56 0.34 0.009 0.0016 0.004 0.08 0.45 0.52 2 4.8 0.033 0.46 2.68 0.32 0.010 0.0018 0.005 0.06 0.55 0.56 3 5.6 0.036 0.52 2.78 0.48 0.011 0.0016 0.005 0.07 0.62 0.58 4 5.4 0.042 0.56 2.28 0.43 0.009 0.0017 0.006 0.05 0.66 0.65 5 6.8 0.045 0.59 2.46 0.25 0.009 0.0016 0.005 0.06 0.72 0.68 6 6.7 0.028 0.62 2.16 0.26 0.012 0.0018 0.004 0.06 0.85 0.78 7 7.2 0.026 0.64 2.92 0.34 0.011 0.0018 0.005 0.08 0.90 0.69 8 7.5 0.028 0.74 2.82 0.48 0.010 0.0015 0.004 0.07 0.84 0.67 rain
school
yes One 3.2 0.042 0.42 2.52 0.42 0.010 0.0016 0.005 0.09 0.66 0.63 2 9.5 0.040 0.40 2.42 0.44 0.010 0.0015 0.005 0.08 0.62 0.63 3 5.6 0.010 0.38 2.33 0.38 0.011 0.0016 0.006 0.10 0.43 0.53 4 5.8 0.070 0.37 2.28 0.42 0.010 0.0017 0.007 0.11 0.56 0.61 5 6.8 0.045 0.25 2.62 0.36 0.011 0.0014 0.004 0.09 0.52 0.56 6 6.7 0.048 0.94 2.59 0.32 0.012 0.0018 0.005 0.09 0.69 0.65 7 7.2 0.042 0.40 1.08 0.35 0.011 0.0016 0.006 0.10 0.71 0.97 8 7.3 0.046 0.38 3.58 0.41 0.011 0.0018 0.007 0.12 0.86 0.62 9 8.2 0.043 0.45 2.84 0.05 0.010 0.0018 0.005 0.09 0.82 0.69 10 8.6 0.042 0.46 2.82 0.65 0.010 0.0017 0.006 0.10 0.55 0.54 11 6.2 0.042 0.56 2.66 0.43 0.009 0.0017 0.006 0.05 0.30 0.42 12 6.8 0.045 0.59 2.52 0.35 0.009 0.0016 0.005 0.06 1.10 0.82 13 6.2 0.042 0.56 1.61 0.15 0.009 0.0017 0.006 0.05 0.86 0.92 14 6.8 0.045 0.59 2.83 0.48 0.009 0.0016 0.005 0.06 0.22 0.35

*In Table 1, the component unit is % by weight, and the remaining components are Fe in the metal shell, iron in the flux, and unavoidable impurities. And A represents the A value defined by relational expression 1, and F represents the amount of fluorine equivalent.

Each of the flux-filled welding wires having the composition shown in Table 1 was prepared. Then, using each of these welding wires, flux-charged arc welding was performed on 20 mm of AH36 steel with a yield strength of 360 MPa or higher, which is a high-strength steel sheet for shipbuilding. Welding was performed under 32V, welding speed of 30 to 35 cm/min, average heat input of welding of 14.9 to 19.2 kJ/cm, and 100% CO ₂ protective gas.

Subsequently, in order to evaluate the mechanical properties of the welded metal part obtained by the welding, impact toughness test specimens and tensile test specimens were taken from the center of the welded metal part. Specifically, a KS standard (KS B 0801) No. 4 test piece was used as the tensile test piece. In addition, the tensile strength test is pulled at a cross head speed of 10 ± 1 mm / mim, and the maximum load at rupture is divided by the cross-sectional area of the material. The impact test piece was manufactured according to the KS (KS B 0809) No. 3 test piece, and when impact was applied to the specimen maintained at -30 ℃ with a hammer using a Charpy impact tester, the impact toughness value was calculated using the energy absorbed during fracture. showed up

On the other hand, in order to evaluate the vertical welding workability, SS400 steel with a thickness of 6mm was assembled with T-Fillet, and the welding condition was 160~180A current, 25~26V voltage, and welding speed 25cm/min Straight using Auto Carriage under the vertical posture condition. The flux-charged arc welding was performed using the -up technique, and the criterion for judging welding workability is whether the value of [actual neck thickness/((leg length A+B)/2)] of the bead after welding is 0.95 or less as a standard. judged.

And comprehensively considering the above mechanical properties and welding workability, the overall evaluation was given in Table 2 below. Specifically, ◎ indicates good, Δ indicates normal, and X indicates insufficient.

division No. average
heat input
(kJ/cm) impact toughness
vE-30℃
(J) tensile test good mouth Comprehensive evaluation tensile strength
(MPa) Elongation (%) welding workability Actual neck thickness/
(Legs A+B) example of invention One 25 58 585 29.6 Good 0.85 ◎ 2 24 56 590 29.4 Good 0.83 ◎ 3 25 50 605 29.2 Good 0.86 ◎ 4 26 59 570 30.0 Good 0.88 ◎ 5 25 56 580 29.8 Good 0.86 ◎ 6 26 49 605 29.4 Good 0.84 ◎ 7 26 48 615 28.4 Good 0.92 ◎ 8 25 44 620 28.2 Good 0.90 ◎ comparative example One 27 66 585 29.6 Lowering 1.11 X (Deterioration of welding workability) 2 27 52 575 29.8 Lowering 1.08 X (Deterioration of welding workability) 3 25 38 550 30.4 Good 0.94 X (decreased impact toughness) 4 25 73 595 29.2 Lowering 1.08 X (Deterioration of welding workability) 5 26 33 530 31.6 Lowering 1.06 X (Deterioration of welding workability) 6 25 38 650 28.2 Good 0.94 △ (Increase in tensile strength & decrease in impact toughness) 7 25 28 540 30.8 Good 0.92 X (decreased impact toughness) 8 26 41 655 27.8 Lowering 1.16 X (Deterioration of welding workability) 9 25 21 530 31.4 Good 0.89 X (decreased impact toughness) 10 26 82 635 27.4 Lowering 1.11 X (Deterioration of welding workability) 11 26 59 605 29.4 Lowering 1.08 X (Deterioration of welding workability) 12 26 33 590 29.2 Good 0.92 X (decreased impact toughness) 13 26 31 540 31.0 Good 0.89 X (decreased impact toughness) 14 25 57 610 28.2 Lowering 1.12 X (Deterioration of welding workability)

As shown in Tables 1 and 2, in the case of examples of the present invention (1 to 8) in which flux-charged arc welding was performed using the welding wire according to the present invention, the A value defined by relational expression 1 is 0.5 to 0.8 At the same time, it can be confirmed that the bead property of the thin plate vertical elevation satisfies the value of [actual neck thickness / ((leg length A + B) / 2)] of 0.95 or less, and at the same time, it is possible to secure the impact toughness of 40J or more at -30 ° C. .

In contrast, the comparative examples (1 to 14) in which welding was performed using a welding wire in which the wire composition was out of the scope of the present invention or the A value defined by relational expression 1 did not satisfy 0.5 to 0.8 were [actual items It can be seen that the thickness / ((leg length A + B) / 2)] did not satisfy 0.95 or less, so the bead property was poor, and at the same time, it was difficult to secure impact toughness of 40J or more at -30 ° C.

Specifically, in Comparative Examples 1 and 2, the TiO ₂ content was lower or higher than the level required by the present invention, and thus vertical upward welding workability was deteriorated.

In addition, in the case of Comparative Examples 3 and 4, the C content was lower or excessive than the level required by the present invention. When the C content was low, the -30 ° C impact toughness required by the present invention was poor, and the C content was high. In this case, it can be confirmed that the bead spread is reduced due to the decrease in vertical upward welding workability due to the excessive increase in arc concentration.

In Comparative Examples 5 and 6, the Si content was lower or excessive than the level required by the present invention, and when the Si content was low, the weld metal deoxidation was insufficient and the impact toughness at -30 ° C was poor, and when the Si content was high, welding The impact toughness due to the increased strength of the welded joint was somewhat insufficient due to the excessive metal deoxidation effect.

Comparative Examples 7 and 8 are cases in which the Mn content is lower or excessive than the level required by the present invention. When Mn is low, the weld metal deoxidation is insufficient as in Si, and the impact toughness at -30 ° C is worse than that of Si. When the content of this strong Mn is high, it can be seen that the welding workability deteriorates due to the increase in strength and the decrease in arc stability.

In Comparative Examples 9 and 10, the Mg content range is lower than or excessively contained than the level required by the present invention. When Mg is low, it is confirmed that impact toughness is reduced due to insufficient deoxidation of the weld metal when Mg is low. In this case, the impact toughness was good due to the cleaning effect of the weld metal, but the strength increased due to the increase in the migration of other components (Si, Mn) to the deposited metal, and the decrease in arc properties led to a decrease in welding workability.

In Comparative Examples 11 and 12, the Na + K component range is lower than or excessively contained than the level required by the present invention. When Na + K is low, the welding workability in the thin plate required by the present invention is reduced, When +K is high, it can be confirmed that the amount of oxygen in the deposited metal increases due to the increase in oxide, resulting in a decrease in impact toughness.

In the case of Comparative Examples 13 and 14, the component range required by the present invention was satisfied, but the A value defined by the relational expression 1 did not satisfy 0.5 to 0.8, indicating that welding workability and -30 ° C impact toughness decreased. You can check.

On the other hand, Figure 1 shows the cross-sectional shape of a bead in an upright posture of Auto Carriage in a base material having a thickness of 6 mm using gas shielded flux filling wires of Inventive Examples 2 and 5 and Comparative Examples 2 and 5 in an embodiment of the present invention.

As described above, the detailed description of the present invention has been described with respect to the preferred embodiments of the present invention, but those skilled in the art to which the present invention belongs can make 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 and should not be defined, and should be defined by not only the claims described later, but also those equivalent thereto.

Claims (1)

In the flux-filled wire in which the flux is charged in the metal sheath,
By weight percent, TiO ₂ : 4.0-8.0%, C: 0.02-0.05%, Si: 0.40-0.80%, Mn: 1.50-3.00%, Mg: 0.10-0.50%, B: 0.001-0.020%, Nb: 0.010% or less, V: 0.010% or less, Na + K: 0.35 to 0.90%, F equivalent in alkali and alkaline earth metal-based fluorine compounds: 0.01 to 0.10%, including residual Fe and unavoidable impurities, by the following relational expression 1 A flux-filled wire for gas shielded arc welding with excellent thin-plate weldability formulated to satisfy the defined A value of 0.5 to 0.8.
[Relationship 1]

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