KR102509889B1 - Flux cored welding wire with anti-crack and superior impact toughness at ultra low temperature - Google Patents

Abstract

An all-position weldable flux-cored wire having excellent crack resistance and cryogenic impact toughness is provided.
In the flux-cored wire of the present invention, in terms of weight percent, carbon (C): 0.20% or less (excluding 0%), silicon (Si): 0.2 to 1.5%, manganese (Mn): 0.1 to 10.0% or less, P + S: Less than 0.10%, Nickel (Ni): 6.0 to 15.0%, Chromium (Cr): 13.0 to 25%, Vanadium (V): 5.0% or less (excluding 0%), Tungsten (W): 5.0% or less ( 0% included), nitrogen (N): 0.20% or less, at least one of Li ₂ O, Na ₂ O and K ₂ O: 0.05 to 1.0%, at least one of SiO ₂ , TiO ₂ and ZrO ₂ : 3.0 to 21.0%, including residual Fe and unavoidable impurities, and satisfying relational expressions 1 and 2.

Description

Flux cored welding wire with anti-crack and superior impact toughness at ultra low temperature}

The present invention relates to a flux-cored wire welding material capable of all-position welding with excellent first layer crack resistance and excellent impact toughness even at cryogenic temperatures, and more particularly, from -30 ℃ to -196 ℃ of ethane to liquefied natural gas, etc. It relates to iron-based alloy flux-cored wires used in cryogenic containers and chemical devices.

With continuous industrialization and technological development, the use of refrigerants stored from -80℃ to -196℃ is increasing, and accordingly, 2.25~9% Ni alloy steel, Invar, austenitic stainless steel, Al, high manganese steel, etc. are used as base materials. are using

Conventionally, Ni-based welding materials are used to weld such structures. However, in the case of such Ni-based welding materials, there are many problems in cost and use because the price per kg increases by 20 to 100 times compared to iron-based welding materials that have been used in existing shipbuilding and offshore plants.

In addition, in the case of the recently developed STS Base welding material, a problem of poor crack resistance due to the fully austenite structure has been found.

Therefore, the present invention has been made to overcome the above-mentioned limitations of the prior art, and is a flux cored that can obtain a weld metal having excellent welding workability in all positions and excellent crack resistance, strength and low-temperature toughness of the first layer. It aims to provide a wire.

On the other hand, the subject of the present invention is not limited to the above. The subject of the present invention will be understood from the entire contents of this specification, and those skilled in the art will have no difficulty in understanding the additional subject of the present invention.

One aspect of the present invention,

In the flux cored wire in which the metal sheath is filled with flux,

The wire, in terms of its weight percent, carbon (C): 0.20% or less (excluding 0%), silicon (Si): 0.2 to 1.5%, manganese (Mn): 0.1 to 10.0% or less, P + S: 0.10% less than, Nickel (Ni): 6.0 to 15.0%, Chromium (Cr): 13.0 to 25%, Vanadium (V): 5.0% or less (excluding 0%), Tungsten (W): 5.0% or less (including 0%), Nitrogen (N): 0.20% or less, at least one of Li ₂ O, Na ₂ O and K ₂ O: 0.05 to 1.0%, at least one of SiO ₂ , TiO ₂ and ZrO ₂ : 3.0 to 21.0%, residual Fe and unavoidable impurities, and relates to a flux-cored wire that satisfies the following relational expressions 1 and 2.

[Relationship 1]

2(TiO ₂ +SiO ₂ +ZrO ₂ )/10(Na ₂ O+K ₂ O+Li ₂ O) < 2.5

[Relationship 2]

{(Ni+Mn+30(C+N))/(Cr+V+W)} < 1.5

In addition, the wire may further include one or more of niobium (Nb): 1% or less, copper (Cu): 1% or less, and titanium (Ti): 1% or less.

In addition, the metal shell, in terms of its own weight, C: 0.2% or less, Si: 0.1 to 1.0%, Mn: 0.5 to 9.0%, Cr: 14.0 to 22.0%, Ni: 6 to 15%, V: 5.0% or less , W: 5.0% or less, Ti: 0.01 to 1.0%, N: 0.2% or less, the remaining Fe and unavoidable impurities may be included.

The cryogenic flux-cored wire of the present invention according to the above configuration is applicable to welding of 9% nickel steel, high manganese steel, and stainless steel by optimizing the alloy composition of the flux and the sheath surrounding the flux core, and has excellent cryogenic toughness of the welded part. It has the effect of obtaining weld metal and has the effect of minimizing excellent all-position weldability and crack generation.

Hereinafter, the present invention will be described.

The flux-cored wire in which the metal sheath of the present invention is filled with flux contains, by weight, carbon (C): 0.20% or less (excluding 0%), silicon (Si): 0.2 to 1.5%, manganese (Mn) : 0.1 to 10.0% or less, P + S: less than 0.10%, Nickel (Ni): 6.0 to 15.0%, Chromium (Cr): 13.0 to 25%, Vanadium (V): 5.0% or less (excluding 0%), Tungsten (W): 5.0% or less (including 0%), nitrogen (N): 0.20% or less, at least one of Li ₂ O, Na ₂ O and K ₂ O: 0.05 to 1.0%, SiO ₂ , TiO ₂ and ZrO At least one of _{the two} : 3.0 to 21.0%, including residual Fe and unavoidable impurities, and satisfying the following relational expressions 1 and 2.

Hereinafter, the composition of the wire of the present invention and the reason for its limitation will be described, and below, “%” represents weight% unless otherwise stated.

・C: 0.20% or less (excluding 0%)

Carbon (C) is a component that serves to improve strength and hardness. If the content is excessive, there is a problem of forming carbide and reducing the toughness of the welded part. Therefore, in the present invention, it is preferable to limit the carbon content to 0.2% or less.

Si: 0.2~1.5%

Silicon (Si) is a component that improves deoxidation and workability (spreadability), and when its content is less than 0.2%, there is a problem in that the deoxidation power is insufficient and the spreadability of the beads is lowered. On the other hand, when the content exceeds 1.5% In this case, there is a problem in that the strength of the weld is excessively increased and the crack susceptibility is increased. Therefore, in the present invention, it is preferable to limit the Si content to 0.2 to 1.5%.

In the present invention, the metal Si source is an alloy that forms the outer shell, metal Si and Fe-Si alloys contained in the flux, or Si reduced from slag components such as SiO.

·Mn: 0.1~10.0%

Manganese (Mn) is an austenite stabilizing element. It is a component that improves the slag fluidity to improve the bead shape and maintains the proper strength and toughness of the welded part. In order to obtain the above-mentioned effect, it is necessary to contain Mn in an amount of 0.1% or more. However, if the content exceeds 10.0%, it is undesirable because it may cause a rapid decrease in toughness and decrease in crack resistance of welded joints.

Therefore, in the present invention, it is preferable to limit the content of Mn to 0.1 to 10.0%.

On the other hand, as the Mn source in the present invention, there are alloys forming the outer shell, metal Mn included in the flux, Fe-Mn alloy, MnO ₂ and MnCO ₃ , etc., and the amount of Mn can be adjusted by adding any of them.

·P + S: less than 0.10%

P and S are one of the main elements that affect high-temperature cracking, and can cause high-temperature cracking by generating Ni alloys and low-melting compounds such as Ni3S7, NiS, and Ni3P. Therefore, control of P and S impurities is essential, and the occurrence of hot cracking can be reduced by controlling the total content of P and S. Therefore, it is preferable that the sum of at least one of P and S is less than 0.10%.

·Cr: 13.0~25.0%

Chromium (Cr) has the effect of improving the strength of the weld metal. If it is less than 13.0%, there is no effect, and if it exceeds 25.0%, chromium carbide is excessively formed, resulting in a decrease in toughness. Therefore, in the present invention, it is preferable to limit the Cr content to 13.0 to 25.0%.

Examples of the Cr source in the present invention include alloys forming the outer shell, metal Cr contained in the flux, Fe-Cr alloys, and Cr ₂ O ₃ .

·Ni: 6.0~15.0%

Ni is an austenite stabilizing element. It has the effect of improving the toughness of the weld metal, but if it is less than 6.0%, the ferrite structure of the welded part is excessively formed and the toughness is deteriorated. causes Therefore, in the present invention, it is preferable to limit the content of Ni to 6.0 to 15.0%.

Examples of the Ni source in the present invention include metal Ni, Fe-Ni alloy, Ni-Mg, and the like included in the alloy forming the outer shell and the flux.

V (vanadium): 5.0% or less (excluding 0%)

Vanadium has the effect of improving the strength of the welded part. However, when applied in excess of 5.0%, there is a problem in that carbide is excessively formed and the toughness of the welded part is deteriorated. Therefore, in the present invention, the content of vanadium is preferably limited to 5.0% or less (excluding 0%), more preferably 0.01 to 5.0%, and most preferably 0.05 to 5.0%. .

・W (tungsten): 5.0% or less (including 0%)

Tungsten has an effect of improving the strength of the weld zone. If the content is excessive, carbide is excessively formed, resulting in deterioration of the toughness of the weld zone. Therefore, in the present invention, it is preferable to limit the tungsten content to 5.0% or less. .

N: 0.20% or less

Nitrogen (N) has an effect of improving the strength of deposited metal. If the content of such nitrogen is excessive, there is a problem in that toughness is deteriorated by generating nitrides. Therefore, in the present invention, it is preferable to limit the N content to 0.20% or less. On the other hand, as the nitrogen source in the present invention, an alloy forming the outer shell and a metal included in the flux may be Fe-N, Cr-Fe-N, Cr-N, or Mn-N alloy.

At least one of Li ₂ O, Na ₂ O and K ₂ O: 0.05 to 1.0%

In the present invention, the alkali metal oxide lowers the ionization potential of the arc during welding, thereby facilitating the generation of an arc and maintaining a stable arc during welding. This effect can be exhibited only when the alkali metal oxide is added in an amount of 0.05% or more. However, if the content exceeds 1.0%, excessive welding fume may be generated due to high vapor pressure. Here, the alkali metal oxide includes at least one of Li ₂ O, Na ₂ O, and K ₂ O, and the effect of adding the alkali metal oxide in the present invention is independent of the respective content ratio.

At least one of SiO ₂ , TiO ₂ and ZrO ₂ : 3.0 to 21.0%

Oxides of Si, Ti, and Zr are added to increase the melting point of slag and improve the workability of all-position welding. If the sum of the added amounts of the above oxides is less than 3.0%, the amount of slag is not sufficient and the encapsulation of the slag is deteriorated. On the other hand, when the sum of the addition amounts of the oxides exceeds 21.0%, slag incorporation tends to occur. Therefore, in the present invention, at least one of SiO ₂ , TiO ₂ and ZrO ₂ is included, and the effect of adding the metal oxide is independent of the respective content ratio.

In addition, in the present invention, if necessary, one or more of niobium (Nb): 1% or less, copper (Cu): 1% or less, and titanium (Ti): 1% or less may be further included.

Nb: 1% or less

Niobium (Nb) has an effect of improving the strength of deposited metal. When such Nb is added excessively, an effect of improving strength can be expected by reacting with carbon in the weld zone, but it can cause a decrease in impact toughness and resistance to high-temperature cracking.

·Cu: 1% or less

Copper (Cu) is an austenite stabilizing element and serves to maintain appropriate strength and toughness of a welded part. When added excessively, corrosion resistance and hot workability are deteriorated. Therefore, in this embodiment, it is preferable to limit the content of Cu to 1% or less.

Ti: 1% or less

Titanium (Ti) can act as a nucleation site when it solidifies at high temperatures by generating carbides or nitrides in the weld. In addition, it serves to increase the strength of the weld by making the austenite crystal grains smaller. Therefore, in this embodiment, it is preferable to limit the content of Ti to 1% or less.

[Relational expression 1]

2(TiO ₂ +SiO ₂ +ZrO ₂ )/10(Na ₂ O+K ₂ O+Li ₂ O < 2.5

In the flux-cored wire of the present invention in which the metal sheath is filled with flux, the content and ratio of oxides must satisfy relational expression 1. If relational expression 1 is not satisfied, weldability and crack resistance may deteriorate due to deterioration in weld quality.

[Relationship 2]

{(Ni+Mn+30(C+N))/(Cr+V+W)} < 1.5

In the flux-cored wire of the present invention in which the metal sheath is filled with flux, the content and ratio of the alloy may be related to the strength and toughness of the welded part. In the present invention, when the welding wire satisfies the above [Relational Expression 2], the yield strength of the deposited metal is 350 MPa or more, the tensile strength is 600 MPa or more, the elongation is 25% or more, and the -196 degree Charpy impact toughness of 27 J or more can be secured.

The remaining component of the present invention is iron (Fe).

In addition to the above components, unintended impurities from raw materials or the surrounding environment may inevitably be mixed in during the normal manufacturing process, so they cannot be excluded. Since these impurities are known to anyone skilled in the ordinary manufacturing process, not all of them are specifically mentioned in this specification.

The welding wire of the present invention may generally be represented by a single outer shell structure in which a metal outer sheath surrounds the flux of an alloy component. At this time, in the present invention, the diameter of the wire is appropriately about 0.9 to 1.6 mm, and the weight fraction of the metal sheath is approximately 50 to 90 as a weight fraction of the total weight of the welding wire considering the difference between the density of the sheath and the density of the flux. % is preferred.

In addition, the metal shell, in terms of its own weight, C: 0.2% or less, Si: 0.1 to 1.0%, Mn: 0.5 to 9.0%, Cr: 14.0 to 22.0%, Ni: 6 to 15%, V: 5.0% or less , W: 5.0% or less, Ti: 0.01 to 1.0%, N: 0.2% or less, the remaining Fe and unavoidable impurities may be included

By using a flux-cored wire that satisfies the alloy composition of the flux of the welding material and the alloy composition of the sheath surrounding the flux core, All Position Welding is possible and a welded joint with excellent tensile strength and impact toughness can be obtained. can

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

(Example)

A flux-cored welding wire having the components shown in Table 1 below was prepared. At this time, the metal sheath constituting the welding wire used in this embodiment, in terms of its weight percent, C: 0.1% or less, Si: 0.1 to 1.0%, Mn: 0.5 to 9.0%, Cr: 14.0 to 22.0%, Ni : 6 to 15%, V: 5.0% or less, W: 5.0% or less, Ti: 0.01 to 1.0%, N: 0.2% or less, the remaining Fe and unavoidable impurities.

Flux Cored Arc Welding (FCAW) was performed using each of the welding materials. At this time, a slope was formed on the grooved surface of the SM490 steel sheet having a thickness of 20 mm so that the grooved angle was 45 °, and the grooved portion was buttered with a wire to form a buttering layer. After that, the buttered parent materials were arranged so that the root gap was 12 mm, and a padding (steel material) with the same buttered surface was placed on the narrower side of the improvement. This improvement was welded according to JIS Z 3111: 2005 to produce deposited metal.

In the case of FCAW, welding was performed under 100% CO ₂ conditions and Ar+15~25% CO ₂ conditions with a heat input of 12 kJ/cm. In general, when 100% CO ₂ protective gas is applied, the tensile strength is similar to that of Ar + 15 to 25%, but the impact toughness is lowered due to the increased oxygen content of the deposited metal. In this embodiment, 100% CO ₂ protection The results of physical properties during gas welding are shown. At this time, a wire having a diameter of 1.2 mm was used.

Thereafter, the yield strength (YS), tensile strength (TS), elongation (EL.), and Charpy impact absorption energy (Joules) of -196°C of the obtained welded joint were measured, and the results are shown in Table 2 below.

In addition, in this embodiment, all-position weldability was visually compared and judged in consideration of arc stability and slag exfoliation, and was evaluated by dividing into three stages: A (excellent), B (insufficient), and C (poor).

In addition, cracks and porosity were visually compared and shown in Table 2, and cracks were evaluated as no cracks (A), multi-layer cracks (B), and first layer cracks (C).

Wire Composition (% by weight) relational expression 1 relational expression 2 C Si Mn P+S Ni Cr V W N A* A** Invention example 1 0.01 0.9 2.5 0.02 8 18 2 2 0.02 13 0.22 0.6 0.5 Invention example 2 0.18 0.9 2.5 0.02 8 18 2 2 0.02 3 0.06 0.1 0.8 Invention Example 3 0.03 0.2 2.5 0.02 8 18 2 2 0.02 21 0.26 1.1 0.5 Invention example 4 0.03 1.4 2.5 0.02 8 18 2 2 0.02 13 0.22 0.6 0.5 Invention example 5 0.03 0.9 11 0.02 8 18 2 2 0.02 13 0.8 2.1 0.9 Example 6 0.03 0.9 2.5 0.02 14 18 2 2 0.02 13 0.9 2.3 0.8 Example 7 0.03 0.9 2.5 0.02 8 18 2 - 0.02 13 0.22 0.6 0.6 Comparative Example 1 0.21 0.9 2.5 0.02 8 18 2 - 0.02 13 0.23 0.6 0.9 Comparative Example 2 0.03 1.6 2.5 0.02 8 18 2 - 0.02 13 0.18 0.5 0.6 Comparative Example 3 0.03 0.9 11 0.02 8 18 2 - 0.02 13 0.55 1.4 1.0 Comparative Example 4 0.05 0.9 2.5 0.02 16 18 2 - 0.02 13 0.33 0.9 1.0 Comparative Example 5 0.07 0.9 2.5 0.02 8 26 2 - 0.02 13 0.25 0.7 0.5 Comparative Example 6 0.02 0.9 2.5 0.02 8 18 6 - 0.02 13 0.27 0.7 0.5 Comparative Example 7 0.08 0.9 2.5 0.02 8 18 - 6 0.02 13 0.8 2.1 0.6 Comparative Example 8 0.03 0.9 2.5 0.02 8 18 2 - 0.02 2 0.6 0.2 1.0 Comparative Example 9 0.15 0.9 2.5 0.02 8 18 2 - 0.02 22 0.02 0.1 0.8 Comparative Example 10 0.03 0.9 2.5 0.02 8 18 2 2 0.02 13 0.95 2.5 0.5 Comparative Example 11 0.04 0.9 2.5 0.02 8 18 2 - 0.02 13 1.0 2.6 0.6 Comparative Example 12 0.11 0.9 8 0.02 14 15 2 0.06 13 0.22 0.6 1.6

- In Table 1, A* represents at least one of SiO ₂ , TiO ₂ and ZrO ₂ , and A** represents at least one of Li ₂ O, Na ₂ O and K ₂ O. Also, relational expression 1 gives 2(TiO ₂ +SiO ₂ +ZrO ₂ )/10(Na ₂ O+K ₂ O+Li ₂ O), and relation 2 gives {(Ni+Mn+30(C+N))/ (Cr+V+W)}.

YS(MPa) TS(MPa) El.(%) -196℃ shock absorption energy (J) fissile weldability Invention example 1 420 620 31 38 A A Invention example 2 480 700 25.5 30 A A Invention example 3 425 670 34 33 A A Invention example 4 410 660 32 34 A A Invention Example 5 455 640 31 36 A A Example 6 466 660 34 34 A A Example 7 452 680 35 32 A A Comparative Example 1 500 720 24.8 26 B C Comparative Example 2 425 670 34 33 C B Comparative Example 3 425 670 34 33 C B Comparative Example 4 430 680 33 25 C B Comparative Example 5 490 710 24.5 25 B B Comparative Example 6 491 717 24.5 27 B B Comparative Example 7 505 722 23.8 26 B B Comparative Example 8 444 666 39.1 32 B C Comparative Example 9 445 667 38.1 32 B C Comparative Example 10 499 711 24.6 26 B C Comparative Example 11 450 680 35 32 B C Comparative Example 12 660 780 23.5 20 C B

As can be seen from Table 1 and Table 2, it can be seen that Inventive Examples 1-7, which not only satisfy the alloy components of the present invention but also satisfy the relational expressions 1 and 2, have excellent crack resistance and all-position weldability. there is. In addition, it can be confirmed that the yield strength of the welded joint obtained by using Inventive Example 1-7 satisfies all of 350Mpa or more, tensile strength of 600MPa or more, elongation of 25% or more, and -196°C impact toughness of 27J or more.

On the other hand, in the case of Comparative Example 1, when the C content exceeded 0.21%, spatter was excessively generated and weldability was deteriorated, making it difficult to secure a good weld bead. In addition, it was difficult to secure good impact toughness because the strength of the welded part was excessive.

In the case of Comparative Example 2, when the Si content exceeded 1.5%, it was difficult to secure a good weld bead due to excessive bead spreadability and poor weld penetration characteristics, and poor crack resistance. It was difficult to secure a good weld bead.

In the case of Comparative Example 3, when the Mn content was 10%, the toughness and crack resistance were rapidly deteriorated, and excessive oxide formation. It was difficult to secure a good welding bead.

In the case of Comparative Example 4, the Ni content exceeded 16%, so the tensile strength was low compared to the target, and it was difficult to secure good impact toughness.

In the case of Comparative Examples 5-7, the tensile strength was high due to excessive Cr, V and W contents, and it was difficult to secure good impact toughness.

In the case of Comparative Examples 8 and 9, the content of oxides such as TiO ₂ +SiO ₂ +ZrO ₂ was too low or too high, making it difficult to secure good weldability in the upward modification position.

Comparative Examples 10 and 11 did not satisfy the relational expression 1, and thus excessive fumes were generated during welding due to excessive arc vapor.

In the case of Comparative Example 12, the tensile strength was high because the relational expression 2 was not satisfied, and it was difficult to secure good impact toughness.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible without departing from the technical spirit of the present invention described in the claims. It will be obvious to those skilled in the art.

Claims (3)

In the flux cored wire in which the metal sheath is filled with flux,
The wire, in terms of its weight percent, carbon (C): 0.20% or less (excluding 0%), silicon (Si): 0.2 to 1.5%, manganese (Mn): 0.1 to 10.0% or less, P + S: 0.10% Less than, Nickel (Ni): 6.0 to 15.0%, Chromium (Cr): 13.0 to 25%, Vanadium (V): 2.0 to 5.0%, Tungsten (W): 5.0% or less (including 0%), Nitrogen (N) : 0.20% or less, at least one of Li ₂ O, Na ₂ O and K ₂ O: 0.05 to 1.0%, at least one of SiO ₂ , TiO ₂ and ZrO ₂ : 3.0 to 21.0%, residual Fe and unavoidable impurities Including, a flux-cored wire that satisfies the following relational expressions 1 and 2.
[Relationship 1]
2(TiO ₂ +SiO ₂ +ZrO ₂ )/10(Na ₂ O+K ₂ O+Li ₂ O) < 2.5
[Relationship 2]
{(Ni+Mn+30(C+N))/(Cr+V+W)} < 1.5
The flux according to claim 1, wherein the wire further comprises at least one of niobium (Nb): 1% or less, copper (Cu): 1% or less, and titanium (Ti): 1% or less. cored wire.
The method of claim 1, wherein the metal shell, by weight percent, C: 0.2% or less, Si: 0.1 ~ 1.0%, Mn: 0.5 ~ 9.0%, Cr: 14.0 ~ 22.0%, Ni: 6 ~ 15%, A flux cored wire characterized in that it contains V: 5.0% or less, W: 5.0% or less, Ti: 0.01 to 1.0%, N: 0.2% or less, the balance of Fe and unavoidable impurities.