KR102670740B1 - Self-shielded flux cored wire having excellent defect resistance at high voltage condition - Google Patents

Abstract

Self-shielded flux cored wire for electromagnetic field use with excellent fault tolerance under high voltage conditions is provided.
The present invention relates to a flux cored wire in which the metal shell is filled with flux, wherein the flux is expressed as a weight percent relative to itself, converted to Li in Li-Si-Fe oxide: 3.30 to 4.60%, converted to Li in LiF. Value: 0.08~0.70%, Al: 16.0~20.0%, Zr: 0.2~1.2%, BaCO ₃ : 0.5~2.5%, rare earth oxide: 1.0~9.0%, residual BaF and metal components (Fe, Mn, Si) and It relates to a self-shielded flux cored wire that consists of inevitable impurities (C, P, S, N) and satisfies the A value of 0.8300 to 1.5900, defined by the following relational equation 1.

Description

Self-shielded flux cored wire having excellent defect resistance at high voltage condition}

The present invention relates to a flux cored wire that can perform welding without additional gas shielding, and more specifically, to a flux core for self-shielded arc welding that can be applied to steel structure welds that require excellent defect resistance and slag exfoliation under high voltage conditions. It's about Dwyer.

Welding using flux cored wire for self-shielded arc welding is a method of welding without the shielding effect of shielding gas, unlike flux cored wire for arc welding that uses general shielding gas. In the case of self-shielded arc welding, since no protective gas is used, there is a high risk that oxygen and nitrogen in the atmosphere will penetrate the weld zone, and such oxygen and nitrogen cause a decrease in impact toughness through the formation of various inclusions. In addition, oxygen and nitrogen dissolve in the high-temperature welding molten pool and form gas, which can cause defects in the weld zone. Therefore, it is important for flux cored wire for self-shielded arc welding to protect the weld area through shielding gas or vapor generated by the flux inside the tubular shell.

Early self-shielded welding was performed by forming metal vapor around the arc to protect the weld area from the atmosphere. Among them, lithium (Li) vapor is known to effectively protect the weld zone from the atmosphere (oxygen and nitrogen), and a self-shielded flux cored wire using Li-Si-Fe oxide has recently been introduced (Patent Document 1).

Meanwhile, this self-shielded flux cored wire shows the best welding performance under optimal welding current/welding voltage conditions. If the welding voltage increases under optimal conditions, the size of the welding arc pool increases, and more oxygen and nitrogen in the atmosphere penetrate, raising the risk of causing porosity in the weld zone.

In the case of self-shielded flux cored wire for electronics, which is mainly used for steel structures and plants, welding technology that increases the amount of welding is used to improve work efficiency as needed. In general, when the welding voltage is increased, the amount of deposited metal increases, which can improve work efficiency. However, as explained earlier, an increase in the welding voltage can lead to a decrease in the defect resistance of the weld zone, so a self-shielded flux core with excellent defect resistance even under high voltage conditions is recommended. Dwyer calls for development.

Republic of Korea Public Patent No. KR2016-0077444

The purpose of the present invention is to provide a flux cored wire that can secure a weld zone with excellent defect resistance and slag detachment during self-shielded arc welding under high voltage conditions.

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

One aspect of the present invention is,

In a flux-cored wire in which the metal shell is filled with flux, the flux, in weight percent relative to itself, is converted to Li in Li-Si-Fe oxide: 3.30 to 4.60%, and converted to Li in LiF: 0.08 to 0.08. 0.70%, Al: 16.0~20.0%, Zr: 0.2~1.2%, BaCO ₃ : 0.5~2.5%, rare earth oxide: 1.0~9.0%, residual BaF, metal components and inevitable impurities (C, P, S, N) It relates to a self-shielded flux cored wire for electric power that has excellent fault resistance under high voltage conditions where the A value defined by the following relational equation 1 satisfies 0.8300 to 1.5900.

[Relationship 1]

Using the self-shielded flux cored wire of the present invention, it is possible to not only have excellent fault resistance under high voltage conditions, but also enable all-position welding and ensure excellent welding workability such as bead shape and slag peelability.

Hereinafter, the present invention will be described.

The present inventors conducted repeated experiments to manufacture a self-shielded flux cored wire that not only has excellent defect resistance under high voltage conditions when welding, but also has excellent bead shape and slag removal properties. As a result, a large amount of Li-Si-Fe is used as a slag former and a gas generator, LiF and BaCO ₃ are added as a gas generator and an arc stabilizer, Al and Zr are used as a reducing agent, and rare earth oxides are appropriately added. By doing so, it is confirmed that the above object can be achieved, and the present invention is presented.

In the present invention, in the flux cored wire in which the metal shell is filled with flux, the flux is expressed as a weight percent of itself, converted to Li in Li-Si-Fe oxide: 3.30 to 4.60%, Li in LiF Converted value: 0.08~0.70%, Al: 16.0~20.0%, Zr: 0.2~1.2%, BaCO ₃ : 0.5~2.5%, rare earth oxide: 1.0~9.0%, residual BaF and metal components and inevitable impurities (C, P ,S,N), and the A value defined by equation 1 satisfies 0.8300 to 1.5900.

Hereinafter, the self-shielded flux cored wire of the present invention will be described in detail. First, the flux components and composition range of the flux cored wire of the present invention will be described in detail. It should be noted in advance that the content range of each component described below refers to the weight percent content range relative to the flux weight of the wire, and that all are based on weight unless otherwise specified.

Li conversion value in Li-Si-Fe oxide: 3.30 to 4.60%

Li-Si-Fe oxide is a source of Li alkali metal and a slag former. It forms Li metal vapor and shields oxygen and nitrogen penetrating from the atmosphere from the weld zone, thereby reducing the partial pressure of oxygen and nitrogen. However, if the amount of Li is excessive, the Li vapor becomes turbulent due to explosive vapor generation, which reduces welding workability and does not effectively protect the weld zone, causing defects. On the other hand, if the content is insufficient, the amount of slag is small and the weldability is reduced during all-position welding, preventing stable bead formation and detachment performance is reduced.

Therefore, in the present invention, the Li conversion value of Li-Si-Fe oxide is preferably 3.30 to 4.60%.

Li converted to LiF: 0.08 to 0.70%

LiF alkali metal fluoride controls the melting point and viscosity of slag and plays a role in strengthening and stabilizing arc concentration. Through this, defects such as slag mixing and incomplete melting are prevented. If the amount of LiF is excessive, spatter generation increases due to explosive formation of Li and F gases, and fault tolerance deteriorates. On the other hand, if the content is insufficient, the weld area is not effectively protected due to the small amount of shielding gas and slag.

Therefore, in the present invention, it is desirable to control the Li conversion value of LiF to 0.08 to 0.70%.

·Al: 16.0~20.0%

Al reducing agent is a powerful deoxidizing agent, denitrifying agent, and nitrogen fixer, and prevents oxygen or nitrogen present in the atmosphere from entering the melting pool. Oxygen and nitrogen penetrating into the weld zone form gas and cause pores in the weld zone. To suppress porosity under high welding voltage conditions, a content of 16.0% or more is required. However, if the Al content is excessive, it causes grain coarsening and there is a risk that the low-temperature impact toughness of the welded metal may be reduced through the formation of AlN, which is vulnerable to impact, and the slag peelability will also be reduced.

Therefore, in the present invention, it is preferable to control the Al content in the range of 16.0 to 20.0%.

·Zr: 0.2~1.2%

Zr is a strong nitrogen fixer and plays a role in shielding oxygen and nitrogen when Al cannot be used anymore. It also contributes to improving low-temperature impact toughness through grain refinement. However, if Zr is excessive, the slag peelability is greatly reduced, so it is desirable to control the Zr content within the range of 0.2 to 1.2%.

·BaCO ₃ : 0.5~2.5%

BaCO ₃ alkali metal carbonate is an arc stabilizer and gas generator that strengthens arc concentration and improves the defect resistance of welded joints through gas generation. In order to exhibit this effect, a BaCO ₃ content of 0.5% or more is required. However, if the content is excessive, carbon dioxide gas generated as carbonate decomposes during welding is explosively generated, which reduces arc stability and increases spatter generation.

Therefore, in the present invention, it is preferable to control the content of BaCO ₃ in the range of 0.5 to 2.5%.

·Rare earth oxide: 1.0~9.0%

Rare earth oxide RExOy acts as a deoxidizer and denitrifier, which is insufficient for Al and Zr alone, and improves the defect resistance of welded areas. In particular, when the welding voltage is high, the size of the arc pool increases and the influx of oxygen and nitrogen into the atmosphere increases, so Al and Zr alone are not enough to play the role of deoxidation and denitrification. Therefore, defect resistance increases as the amount of rare earth oxide increases, starting from a minimum content of 1% that can act as a deoxidizer and denitrifier. However, if the content is excessive, arc stability deteriorates and a large amount of spatter is generated, which affects welding workability. This is degraded.

Therefore, in the present invention, it is desirable to control the content of rare earth oxides in the range of 1.0 to 9.0%.

· Relationship 1

The present invention controls the sum of the Li conversion value among rare earth oxides, Al, Zr, and Li-Si-Fe oxides in the flux and the Li conversion value among LiF so that the A value defined by the following relational equation 1 satisfies 0.8300 to 1.5900. It is characterized by If the A value defined by the following relational equation 1 is less than 0.8300, and the amount of rare earth oxides and deoxidizing agents such as Al and Zr, and denitrifying agents is insufficient, the inflow of oxygen and nitrogen in the atmosphere cannot be prevented, and fault resistance is reduced. Additionally, if turbulence occurs due to excessive Li content, the shielding gas does not protect the weld zone and welding workability deteriorates. On the other hand, when the A value exceeds 1.5900, the amount of Al, which reduces peelability, is excessive, and the amount of Li oxide that forms slag is reduced, which may deteriorate slag peelability.

[Relationship 1]

In addition, the flux constituting the welding wire of the present invention may contain BaF ₂ , metal components (Mn, Cr, Mg, etc.), and metal oxides (FexOy, SiO, etc.) as residual components. The BaF ₂ component is contained as a slag forming agent in an amount of approximately 35 to 55%, and in addition, metal components such as Mn, Ni, Cr, and Mg are contained in approximately 5 to 17%, and metal oxides such as FexOy and SiO are contained in approximately 5 to 17%. (Li-Si-Fe oxide) may be included. Furthermore, the flux of the present invention may contain other impurities (C, P, S, N).

Hereinafter, embodiments of the present invention will be described in detail. The following examples are only for understanding of the present invention and do not limit the present invention.

(Example)

A flux having the composition (% by weight relative to the flux weight) shown in Table 1 below was filled into a steel shell to produce a self-shielded flux cored wire with a diameter of 1.6 to 2.0 mm. At this time, the steel outer shell is expressed in weight%: C: 0.015-0.025%, Si: 0.02% or less, Mn: 0.15-0.25%, P: 0.010% or less, S: 0.010% or less, and lead containing Fe and a small amount of impurities. Steel was used, and the flux filling rate was 15.0 to 25.0% of the total weight of the wire.

Afterwards, using each manufactured wire, 2-pass welding was performed on the base material (EH36) at 2F and 1G welding positions under the welding conditions shown in Table 2 below, and then welding workability and defect resistance were evaluated, and the results are shown in Table 3 below. shown in

More specifically, in the evaluation of welding workability, arc stability, slag detachment, and spattering properties were compared and judged through the sensory evaluation of the welder, and defect resistance was also evaluated through the degree of porosity in the appearance of the weld zone. The results were categorized into excellent (○), average (△), and poor (X).

division Flux composition (% by weight) Li-Si-Fe
oxide
(Li converted value) LiF
(Li converted value) Al Zr BaCO3 rare earth
oxide Relation A Comparative Example 1 3.20 0.21 18.1 0.6 1.7 6.5 1.4721 Comparative example 2 4.70 0.39 17.8 0.8 1.0 7.5 1.0037 Comparative example 3 4.25 0.07 19.5 1.0 2.1 5.7 1.1849 Comparative Example 4 3.75 0.71 19.2 1.0 1.7 6.8 1.1651 Comparative Example 5 3.44 0.50 15.9 0.4 1.0 3.4 1.1265 Comparative Example 6 3.85 0.42 20.1 0.6 0.8 4.2 1.1686 Comparative example 7 4.11 0.36 18.5 0.1 1.0 5.5 1.0982 Comparative example 8 3.70 0.45 18.1 1.3 1.7 7.5 1.2498 Comparative Example 9 4.00 0.28 18.8 0.4 0.4 7.0 1.1959 Comparative Example 10 4.32 0.31 19.2 0.8 2.6 4.8 1.0756 Comparative Example 11 4.15 0.55 18.8 1.0 1.7 0.9 0.9680 Comparative Example 12 3.94 0.42 17.8 0.6 2.1 9.1 1.2028 Comparative Example 13 3.32 0.09 19.8 1.1 2.2 8.8 1.5982 Comparative Example 14 4.55 0.64 16.5 0.4 2.0 1.4 0.8242 Invention Example 1 3.95 0.25 17.8 1.0 2.1 3.0 1.1117 Invention Example 2 3.75 0.28 17.4 0.8 2.0 6.0 1.2207 Invention Example 3 4.32 0.42 19.2 1.0 1.3 2.0 0.9940 Invention Example 4 3.55 0.43 17.4 0.4 2.0 6.5 1.2383 Invention Example 5 3.94 0.25 17.8 0.8 1.0 6.0 1.1837 Invention Example 6 4.32 0.45 16.9 0.6 2.0 5.5 1.0054 Invention Example 7 3.75 0.25 17.8 0.8 1.0 8.2 1.2942 Invention Example 8 4.00 0.48 19.0 1.0 0.8 6.0 1.1382 Invention Example 9 3.94 0.28 19.2 0.4 1.7 6.8 1.2176 Invention Example 10 4.11 0.50 18.1 0.8 1.0 5.0 1.0605

*In Table 1, the remaining components are BaF ₂ , metal components, and inevitable impurities.

Welding conditions Welding voltage (V) Welding current (A) protective gas polarity Stick-out optimal conditions 23 260 doesn't exist DCEN 20~30mm High voltage conditions 28 260 doesn't exist DCEN 15~25mm

note Welding workability Arc stability slag
peelability spattering Weld fault tolerance General conditions High voltage conditions Comparative Example 1 △ X △ O △ Comparative example 2 X O △ O △ Comparative example 3 △ X △ O △ Comparative Example 4 X O X O O Comparative Example 5 X O △ △ X Comparative Example 6 O X O O O Comparative example 7 △ O △ O △ Comparative example 8 O X O O △ Comparative Example 9 X O △ O △ Comparative Example 10 △ △ X O △ Comparative Example 11 △ △ △ △ X Comparative Example 12 △ △ X O O Comparative Example 13 O X O O O Comparative Example 14 △ O O △ X Invention Example 1 O O O O O Invention example 2 O O O O O Invention Example 3 O O O O O Invention Example 4 O O O O O Invention Example 5 O O O O O Invention Example 6 O O O O O Invention Example 7 O O O O O Invention Example 8 O O O O O Invention Example 9 O O O O O Invention Example 10 O O O O O

As shown in Tables 1 and 3 above, it can be confirmed that Inventive Examples 1 to 10, which satisfy all of the component ranges proposed by the present invention, are excellent in arc stability, slag removal, and spatter resistance, and are excellent in defect resistance even under high voltage conditions. there is.

On the other hand, in Comparative Example 1, the amount of slag was small due to a lack of Li-Si-Fe, and the slag peelability was greatly reduced, and in the case of Comparative Example 2, excessive Li vapor was formed and arc stability was reduced.

In Comparative Example 3, slag detachability was reduced due to a lack of LiF, and in Comparative Example 4, where F gas was generated together with excessive LiF, spattering properties were greatly reduced.

In Comparative Example 5, arc stability was reduced due to a lack of Al, and fault resistance was reduced due to insufficient oxygen and nitrogen fixation. On the other hand, in Comparative Example 6, where Al was excessive, arc stability and slag peelability were improved, but slag peelability was greatly reduced.

In Comparative Example 7, arc stability, spattering properties, and defect resistance were insufficient overall due to a lack of Zr, and in Comparative Example 8, where Zr was excessive, slag peelability was deteriorated.

In Comparative Example 9, arc stability was reduced due to a lack of BaCO ₃ , and in Comparative Example 10, spattering property was reduced due to CO ₂ gas generated by decomposition of carbonate, which was excessive.

In Comparative Example 11, it can be seen that defect resistance was reduced due to a lack of rare earth oxides, and in Comparative Example 12, where there was an excess of rare earth oxides, spatter resistance was reduced.

In Comparative Examples 13-14, the A value defined by Equation 1 did not satisfy the range, resulting in poor weldability. Specifically, in Comparative Example 14, where the A value is less than the range of the present invention, defect resistance was reduced due to excessive Li and insufficient deoxidizing/denitrifying agents, and in Comparative Example 13, where the A value was larger than the range of the present invention, the amount of slag was insufficient due to small Li and oxides. The slag peelability was poor due to excessive Al, Zr, etc.

As described above, the detailed description of the present invention has described preferred embodiments of the present invention, but those skilled in the art can make various modifications without departing from the scope of the present invention. Of course this is possible. Therefore, the scope of rights of the present invention should not be limited to the described embodiments, but should be determined not only by the claims described later, but also by their equivalents.

Claims (2)

In a flux cored wire in which the flux in the metal shell is charged at a charging rate of 15.0 to 25.0%,
The flux is expressed as a weight percentage relative to itself, converted to Li in Li-Si-Fe oxide: 3.30 to 4.60%, converted to Li in LiF: 0.08 to 0.70%, Al: 16.0 to 20.0%, Zr: 0.2 to 1.2. %, BaCO ₃ : 0.5~2.5%, rare earth oxide: 1.0~9.0%, remaining BaF ₂ 35~55%; 5 to 17% of one or more selected from Mn, Ni, Cr and Mg; and unavoidable impurities (C, P, S, N), and is a self-shielded flux cored wire for electronics with excellent fault resistance under high voltage conditions where the A value defined by the following relational equation 1 satisfies 0.8300 to 1.5900.
[Relational Expression 1]

The self-shielded flux cored wire for electronic position according to claim 1, wherein the amount of the charged flux satisfies 15 to 25% by weight of the entire wire.