KR20220133643A - Flux cored welding wire with anti-crack and superior impact toughness at ultra low temperature - Google Patents

Abstract

Provided is a position-changeable weldable flux cored wire with superior crack resistance and superior impact toughness at ultra-low temperatures. The flux cored wire comprises, by wt %, 0.20 % or less (excluding 0 %) of carbon (C), 0.2-1.5 % of silicon (Si), 0.1-10.0 % or less of manganese (Mn), less than 0.10 % of P+S, 6.0-15.0 % of nickel (Ni), 13.0-25 % of chromium(Cr), 5.0 % or less (excluding 0 %) of vanadium (V), 5.0% or less (including 0%) of tungsten (W), 0.20% or less of nitrogen (N), 0.05-1.0 % of at least one of Li_2O, Na_2O, and K_2O, at least one of SiO_2, 3.0-21.0 % of TiO_2, and ZrO_2, and the remainder of Fe and inevitable impurities, and satisfies relational expression 1 and relational expression 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 full-fine welding with excellent super-layer crack resistance and excellent impact toughness even at cryogenic temperatures. It relates to an iron-based alloy flux-cored wire used in cryogenic vessels and chemical equipment, etc.

With continuous industrialization and technological development, the use of storage refrigerants from -80°C to -196°C is increasing. are using

In general, a Ni-based welding material is used to weld such a structure. However, in the case of such a Ni-based welding material, compared to the iron-based welding material used in existing shipbuilding and offshore plants, the price per kg increases by 20 to 100 times, so there are many problems in cost and use.

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

Therefore, the present invention has been devised to overcome the above-described limitations of the prior art, and it is possible to obtain a weld metal having excellent welding workability in an electric field and excellent super-layer crack resistance, strength and low-temperature toughness at the same time. The purpose is to provide a wire.

In addition, the subject of this invention is not limited to the above-mentioned content. The subject of the present invention will be understood from the overall content of the present specification, and those of ordinary skill in the art to which the present invention pertains will have no difficulty in understanding the additional subject of the present invention.

One aspect of the present invention is

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

The wire, in its own 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: 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: 0.05-1.0%, SiO ₂ , at least one of TiO ₂ and ZrO ₂ : 3.0-21.0%, residual Fe and unavoidable impurities, and relates to a flux-cored wire satisfying the following Relations 1 and 2.

[Relational Expression 1]

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

[Relational Expression 2]

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

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

In addition, the metal shell, by 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 materials by optimizing the alloy composition of the flux and the outer shell surrounding the flux core, and has excellent cryogenic toughness at the weld zone It has the effect of obtaining weld metal and has the effect of minimizing the occurrence of cracks and excellent weldability.

Hereinafter, the present invention will be described.

The flux-cored wire in which the metal sheath of the present invention is filled with flux, 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 ₂ : 3.0-21.0%, including residual Fe and unavoidable impurities, and satisfies the following Relations 1 and 2.

Hereinafter, the composition of the wire of the present invention and the reasons for its limitation will be described.

・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 in that carbides are formed and the toughness of the weld joint is reduced. 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 the deoxidation action and workability (spreadability). If the content is less than 0.2%, the deoxidation power is insufficient and the spreadability of beads is reduced, whereas the content exceeds 1.5%. When this occurs, there is a problem in that the strength of the weld joint is excessively increased and 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 forming the shell, metal Si and Fe-Si alloys contained in the flux, or Si reduced from a slag component such as SiO.

·Mn: 0.1 to 10.0%

Manganese (Mn) is an austenite stabilizing element. It is a component that improves the bead shape by improving the slag fluidity and maintains the proper strength and toughness of the welded part. In order to obtain the above-described effect, it is necessary to contain Mn in an amount of 0.1% or more. However, when the content exceeds 10.0%, it is not preferable because it may cause a sharp decrease in toughness and a decrease in crack resistance of the welded part.

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

On the other hand, as the Mn source in the present invention, there are alloys forming the shell, metals Mn contained in the flux, Fe-Mn alloys, 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-point compounds such as Ni3S7, NiS, and Ni3P. Therefore, it is essential to control the P and S impurities, and it is possible to reduce the occurrence of high-temperature cracks by controlling the total content of P and S. Therefore, it is preferable that at least one of P and S is less than 0.10% in total.

·Cr: 13.0~25.0%

Although 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%, there is a problem in that chromium carbide is excessively formed and toughness is lowered. Therefore, in the present invention, it is preferable to limit the content of Cr to 13.0 to 25.0%.

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

·Ni: 6.0~15.0%

Ni is an austenite stabilizing element. Although there is an effect of improving the toughness of the weld metal, if it is less than 6.0%, the weld ferrite structure is excessively generated to reduce the toughness. causes Therefore, in the present invention, it is preferable to limit the Ni content to 6.0 to 15.0%.

Examples of the Ni source in the present invention include alloys forming the shell, metals Ni contained in the flux, Fe-Ni alloys, Ni-Mg, and the like.

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

Vanadium has the effect of improving the strength of the weld. However, when applied in excess of 5.0%, there is a problem in that the toughness of the weld joint is reduced by excessively forming carbides. 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, it is limited to 0.05 to 5.0%. .

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

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

·N: 0.20% or less

Nitrogen (N) has an effect of improving the strength of the deposited metal. When the content of such nitrogen is excessive, there is a problem in that a nitride is formed and toughness is lowered. 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, the alloy forming the shell, metal Fe-N, Cr-Fe-N, Cr-N, Mn-N alloy, etc. contained in the flux may be.

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 to facilitate arc generation, and can maintain a stable arc during welding. The alkali metal oxide may have this effect when added in an amount of 0.05% or more. However, if the content exceeds 1.0%, welding fume may be excessively 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 each content ratio.

SiO ₂ , TiO ₂ and at least one of ZrO ₂ : 3.0~21.0%

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

In addition, in the present invention, if necessary, 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 the effect of improving the strength of the deposited metal. When such Nb is added excessively, it reacts with carbon at the weld and can expect a strength improvement effect, but it can cause a decrease in impact toughness and a decrease in high-temperature cracking resistance.

・Cu: 1% or less

Copper (Cu) is an austenite stabilizing element and serves to maintain proper strength and toughness of the weld. In case of excessive addition, corrosion resistance and hot workability are deteriorated. Therefore, in this embodiment, it is preferable to limit the Cu content to 1% or less.

Ti: 1% or less

Titanium (Ti) may act as a nucleation site when solidifying at a high temperature by generating carbide or nitride in the weld. It also serves to increase the strength of the weld by making the austenite grains smaller. Therefore, in this embodiment, it is preferable to limit the content of Ti to 1% or less.

·[ Relation 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 Equation 1. If Relation 1 is not satisfied, weldability may be deteriorated due to deterioration of weldability and crack resistance.

・[Relational Expression 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 proportion of the alloy may be related to the strength and toughness of the weld. In the present invention, when the welding wire satisfies the above [Relational Expression 2], yield strength of 350 MPa or more, tensile strength of 600 MPa or more, elongation of 25% or more, and -196 degree Charpy impact toughness of 27J or more of the deposited metal can be secured.

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

In addition to the above-mentioned components, since unintended impurities from raw materials or the surrounding environment may be unavoidably mixed in a typical manufacturing process, this cannot be excluded. Since these impurities are known to anyone skilled in the art of manufacturing processes, all details thereof are not specifically mentioned in the present specification.

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

In addition, the metal shell, by 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 outer shell surrounding the flux core, all position welding is possible, and a weld joint with excellent tensile strength and impact toughness is obtained. can

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

(Example)

Wires for flux-cored welding having components as shown in Table 1 below were prepared. At this time, the metal sheath constituting the welding wire used in this embodiment is, by weight%, 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, remaining Fe and unavoidable impurities.

Flux Cored Arc Welding (FCAW) was performed using each of the above welding materials. At this time, on the improved surface of the SM490 steel sheet having a thickness of 20 mm, a slope was formed so that the angle of improvement was 45°, and this improved part was buttered with a wire to form a buttering layer. After that, the root gap between the buttered base metals was arranged so that the root gap became 12 mm, and on the side where the improvement was narrowed, a pad (steel material) whose surface was similarly buttered was placed. This improvement was welded according to JIS Z 3111:2005 to manufacture a weld metal.

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

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

In addition, in this example, full-fine weldability was visually compared and judged in consideration of arc stability and slag peelability, and evaluated by dividing into three stages: A (excellent), B (poor), and C (poor).

In addition, the presence of cracks and pores was also visually compared and shown in Table 2, and evaluation was made as non-cracking (A), multi-layer cracking (B), and super-layer cracking (C).

Wire composition (wt%) Relation 1 Relation 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 Invention example 6 0.03 0.9 2.5 0.02 14 18 2 2 0.02 13 0.9 2.3 0.8 Invention 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, Relation 1 is 2(TiO ₂ +SiO ₂ +ZrO ₂ )/10(Na ₂ O+K ₂ O+Li ₂ O), and Relation 2 is {(Ni+Mn+30(C+N))/ (Cr+V+W)}.

YS(MPa) TS(MPa) El. (%) -196℃ shock absorption energy (J) fissurability 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 Invention example 6 466 660 34 34 A A Invention 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 Tables 1 and 2, it can be seen that Inventive Examples 1-7 not only satisfying the alloy components of the present invention, but also satisfying Relations 1 and 2 are all excellent in crack resistance and full-strength weldability. have. In addition, it can be confirmed that the yield strength of the weld joint obtained by using Inventive Examples 1-7 is 350Mpa or more, the tensile strength is 600MPa or more, the elongation is 25% or more, and the -196°C impact toughness 27J or more is satisfied.

On the other hand, in the case of Comparative Example 1, when the C content exceeded 0.21%, spatter was excessively generated and weldability 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 weld was excessive.

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

In the case of Comparative Example 3, the Mn content was 10%, resulting in a sharp decrease in toughness and crack resistance, and excessive oxide formation. It was difficult to secure a good weld bead.

In the case of Comparative Example 4, the Ni content exceeded 16%, 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 Cr, V and W contents were excessive, so the tensile strength was high, and it was difficult to secure good impact toughness.

In the case of Comparative Examples 8-9, it was difficult to secure good weldability in the upward-modified posture because the content of oxides such as TiO ₂ +SiO ₂ +ZrO ₂ was too little or too much.

Comparative Examples 10-11 did not satisfy Relational Equation 1, so that fumes were generated during welding due to excessive arc steam.

In the case of Comparative Example 12, the relational expression 2 was not satisfied, so the tensile strength was high, 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 within the scope without departing from the technical spirit of the present invention described in the claims. It will be apparent to those of ordinary skill in the art.

Claims (3)

In the flux-cored wire in which the flux is filled in the metal sheath,
The wire, in its own 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: 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: 0.05-1.0%, SiO ₂ , at least one of TiO ₂ and ZrO ₂ : 3.0-21.0%, residual Fe and unavoidable impurities, the flux-cored wire satisfying the following Relations 1 and 2.
[Relational Expression 1]
2(TiO ₂ +SiO ₂ +ZrO ₂ )/10(Na ₂ O+K ₂ O+Li ₂ O) < 2.5
[Relational Expression 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 according to claim 1, wherein the metal shell is, by 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.