KR102022448B1 - Ni base flux cored wire for cryogenic Ni alloy steel - Google Patents

Abstract

Ni-based flux cored wire for cryogenic Ni alloy steel is provided.
The wire of the present invention is, in terms of its own weight%, C: 0.01 to 0.1%, Si: 0.1 to 1.0%, Mn: 1.5 to 5.0%, P + S: less than 0.04%, Cr: 18.0 to 23.0%, Mo: 8.0 ~ 14.0%, Ti: 0.01-1.0%, Nb: 1.0-3.0%, SiO ₂ : 0.1-3.0%, MnO: 0.5-5%, at least one of Li ₂ O, Na ₂ O and K ₂ O: 0.1 ~ 3.0%, at least one of Al ₂ O ₃ , TiO _2, and ZrO ₂ : 5-12%, residual Ni and inevitable impurities, satisfying [Relationship 1], and having a value defined by [Relationship 2] 0.5 or less is satisfied.

Description

Ni base flux cored wire for cryogenic Ni alloy steel}

The present invention relates to a fully post-weld Ni base flux cored wire welding material for cryogenic Ni alloy steel.

With continuous industrialization and technology development, the use of storage refrigerants from -80 ℃ to -196 ℃ is increasing, so 2.25 ~ 9% Ni alloy steel, Invar, austenitic stainless steel, Al, etc. are used as base materials. have.

Of these, 9% Ni alloy steel is inadequate in the development and application of dedicated flux cored wire welding materials. Therefore, research and development is essential to increase productivity. Usually, Ni-based welding materials are used to weld such Ni alloy steel. However, the flux cored wire for 9% Ni steel developed by some advanced companies so far has a problem in that it is expensive because expensive raw materials such as Mo and W are 15-20% by mass. In addition, in the case of such Ni-based welding material, since most of them are constructed with SMAW, production efficiency is extremely low. Therefore, as the need for high efficiency of welding construction emerges, the need to develop plus cored wire for this is increasing throughout the industry.

In other words, there is a need to develop a product having excellent tensile strength, impact toughness and crack resistance by using a Ni-based welding material whose alloy content is controlled to a minimum by controlling the skin and alloy composition compared to the existing use agent.

(Patent Document 1) Republic of Korea Patent Publication 2015-0066191 (2015.06.16 published)

Therefore, the present invention has been devised to overcome the above-mentioned limitations of the prior art, and by optimizing the alloy composition of the wire welding material, it is easy to process in the form of flux cored wire, and has excellent physical properties as well as Ni-based flux capable of welding at all positions. The purpose is to provide a cored wire welding material.

In addition, the subject of this invention is not limited to the content mentioned above. The problem of the present invention will be understood from the general contents of the present specification, those skilled in the art will have no difficulty understanding the additional problem of the present invention.

The present invention for achieving the above object,

In a flux cored wire in which a metal shell is filled with flux, the wire has a weight of itself, C: 0.01 to 0.1%, Si: 0.1 to 1.0%, Mn: 1.5 to 5.0%, and P + S: 0.04% Below, Cr: 18.0-23.0%, Mo: 8.0-14.0%, Ti: 0.01-1.0%, Nb: 1.0-3.0%, Fe: 0.01-5.0%, SiO ₂ : 0.1-3.0%, MnO: 0.5-5 %, At least one of Li ₂ O, Na ₂ O and K ₂ O: 0.1-3.0%, at least one of Al ₂ O ₃ , TiO ₂ and ZrO ₂ : 5-12%, including residual Ni and unavoidable impurities The present invention relates to a Ni-based flux cored wire for cryogenic Ni alloy steel, which satisfies the following [Relational Expression 1], and the value defined by the following [Relational Expression 2] satisfies 0.5 or less.

[Relationship 1]

18-0.54 × Cr≤Mo≤24-0.53 × Cr

[Relationship 2]

{([Na ₂ O] + [K ₂ O] + [Li ₂ O] + 0.2 × [MnO]) / ([SiO ₂ ] + 0.5 × ([Al ₂ O ₃ ] + [TiO ₂ ] + [ZrO ₂ ]))}

The present invention having the above-described configuration can effectively provide a Ni-based flux cored wire welding material which is excellent in physical properties and capable of full post welding and excellent workability by optimizing the alloy composition of the welding material and the metal shell.

In addition, there is an effect that can minimize the occurrence of cracks while showing good weldability.

Hereinafter, preferred embodiments of the present invention will be described. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Hereinafter, a Ni-based flux cored wire welding material according to an aspect of the present invention will be described in detail. Flux cored wire of the present invention, in its own weight%, C: 0.01 ~ 0.1%, Si: 0.1 ~ 1.0%, Mn: 1.5 ~ 5.0%, P + S: less than 0.04%, Cr: 18.0 ~ 23.0%, Mo: 8.0-14.0%, Ti: 0.01-1.0%, Nb: 1.0-3.0%, Fe: 0.01-5.0%, SiO ₂ : 0.1-3.0%, MnO: 0.5-5%, Li ₂ O, Na ₂ O And at least one of K ₂ O: 0.1-3.0%, at least one of Al ₂ O ₃ , TiO _2, and ZrO ₂ : 5-12%, the balance Ni and inevitable impurities, and satisfying the following [Relation Formula 1] And the value defined by the following [Relationship 2] satisfies 0.5 or less.

[Relationship 1]

18-0.54 × Cr≤Mo≤24-0.53 × Cr

 [Relationship 2]

{([Na ₂ O] + [K ₂ O] + [Li ₂ O] + 0.2 × [MnO]) / ([SiO ₂ ] + 0.5 × ([Al ₂ O ₃ ] + [TiO ₂ ] + [ZrO ₂ ]))}

Hereinafter, the compositional components of the wire of the present invention and the reason for limitation thereof will be described, where "%" represents weight%.

C: 0.01 ~ 0.1%

Carbon (C) is a component which plays a role of improving strength and hardness. If the content of C is less than 0.01%, the effect of improving the strength cannot be obtained sufficiently. On the other hand, when it exceeds 0.1%, high temperature crack resistance and toughness are lowered, and there is a problem in that generation of spatter is increased.

Therefore, in the present invention, it is preferable to limit the content of C to 0.01 ~ 0.1%.

In the present invention, examples of the C source include Ni-based alloys forming the shell, metal carbides such as Mn-C, Cr-C, and W-C contained in the flux.

Si: 0.1 ~ 1.0%

Silicon (Si) is a component that improves deoxidation and weldability, and when the content is less than 0.1%, there is a problem in that the bead spreadability is deteriorated due to lack of deoxidizing power, whereas when the content exceeds 1.0%, the Laves phase (Laves Phase) There is a problem that the crack susceptibility is increased by increasing the fraction of the low melting point compound by increasing the generation.

Therefore, in the present invention, it is preferable to limit the content of Si to 0.1 ~ 1.0%. More preferably, it is 0.1 to 0.5%.

Examples of the Si source in the present invention include a Ni-based alloy forming the shell, a metal Si contained in the flux, a Fe-Si alloy, and the like.

Mn: 1.5-5.0%

Manganese (Mn) is a component that serves to improve the slag fluidity to improve the bead shape, and to maintain the appropriate strength and toughness of the weld. In order to obtain the above-mentioned effect, it is necessary to contain Mn in an amount of 1.5% or more, but if the content exceeds 5.0%, it may cause a sudden drop in toughness, which is not preferable.

Therefore, in the present invention, it is preferable to limit the content of Mn to 1.5 ~ 5.0%.

In the present invention, the Mn source includes a Ni-based alloy forming a shell, a metal Mn contained in the flux, a Fe-Mn alloy, MnO ₂ and MnCO ₃ , and the amount of Mn can be adjusted by adding any of them. .

P + S: less than 0.040%

P and S are one of the main elements affecting high temperature cracks, and Ni alloys such as Ni ₃ S ₇ , NiS, Ni ₃ P and low melting compounds may generate high temperature cracks. Therefore, it is necessary to control P and S impurities, and control the total content of P and S can reduce the occurrence of high temperature cracks. Therefore, the total amount of P and S is preferably less than 0.040%.

Cr: 18.0 ~ 23.0

Chromium (Cr) has the effect of improving the strength of the weld metal. If it is less than 18%, there is no effect, and if it exceeds 23%, chromium carbides are excessively formed, so that the toughness is lowered.

Therefore, in the present invention, it is preferable to limit the content of Cr to 18.0 ~ 23.0%.

In the present invention, examples of the Cr source include a Ni-based alloy forming a shell, a metal Cr contained in the flux, a Fe-Cr alloy, Cr ₂ O ₃ , and the like.

Mo: 8.0-14.0%

Molybdenum (Mo) has the effect of improving the strength of the weld metal. If the content of Mo is less than 8.0%, it is difficult to expect the above-described effects, while if the content of Mo exceeds 14.0%, the toughness of the weld metal is lowered.

Therefore, in the present invention, it is preferable to limit the content of Mo to 8.0 ~ 14.0%. More preferably, Mo content is limited to 8.0-10.0% range.

On the other hand, examples of the Mo source in the present invention include Ni-based alloys forming the outer shell, metal Mo and Fe-Mo alloys contained in the flux.

Ti: 0.01 ~ 1.0%

Ti can increase the precipitation hardening effect in Ni-based alloys.

If the content is less than 0.01%, the above effect is not sufficient. On the other hand, if the content exceeds 1.0%, it is difficult to secure a healthy weld due to strain-age-cracks by forming a compound such as Ni ₃ Ti, Ni ₃ (Ti, Al).

Therefore, in the present invention, it is preferable to limit the content of Ti to 0.01 ~ 1.0%. More preferably, the Ti content is limited to the range of 0.01 to 0.4%.

Nb: 1.0-3.0%

Niobium (Nb) has the effect of improving the strength of the weld metal. If the content of Nb is less than 1.0%, it is difficult to expect the above-described effects, while if the content of Nb exceeds 3.0%, the toughness of the weld metal is lowered.

Therefore, in the present invention, it is preferable to limit the content of Nb to 1.0 ~ 3.0%. More preferably, the Nb content is limited to 1.5 to 2.5%.

On the other hand, examples of the Nb source in the present invention include Ni-based alloys forming the shell, metal Nb and Fe-Nb alloys contained in the flux.

Fe: 0.01 ~ 5.0%

Iron (Fe) is an element that is indispensably contained in a welding material or a base metal in Ni-based alloys. If the content exceeds 5.0%, it may be vulnerable to cracks due to increased Laves Phase formation and may reduce corrosion resistance. However, to control the amount less than 0.01% is excessively consumed, Fe content is preferably limited to 0.01 ~ 5.0%.

SiO ₂ (silicon dioxide): 0.1 ~ 3.0%

SiO ₂ serves as a slag forming agent to increase the fluidity and weld bead spreadability of the weld slag. In order to exhibit such an effect, it is preferable to add 0.1% or more in this invention. However, if the content exceeds 3.0%, the Si content in the weld metal is rapidly increased, causing precipitation in the Laves phase, leading to a decrease in crack resistance.

Therefore, in the present invention, the content of SiO ₂ is preferably limited to 0.1 ~ 3.0%.

MnO (manganese oxide): 0.5 to 5%

MnO lowers the slag solidification temperature and serves to increase the fluidity and weld bead spreadability of the weld slag. In order to exhibit such an effect, it is preferable to add in 0.5% or more of this invention. However, if the content is more than 5.0%, there is a problem that causes the arc concentration of the weld metal and decreases the occurrence of cracks.

Therefore, in the present invention, the content of MnO is preferably limited to 0.5 ~ 5.0%.

At least one of Li ₂ O, Na ₂ O and K ₂ O: 0.1-3.0%

In the present invention, the alkali metal oxide lowers the ionization potential of the arc during welding, thereby facilitating generation of the arc, and can maintain a stable arc during welding. The alkali metal oxide must be added at least 0.1% to exhibit this effect. However, if the content exceeds 3.0%, excessive welding fume may occur due to the 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 addition effect of alkali metal oxidation in the present invention is independent of each content ratio.

At least one of Al ₂ O ₃ , TiO ₂ and ZrO ₂ : 5-12%

Al, Ti, and Zr oxides are added to increase the melting point of the slag and to improve the workability of the posture welding. If the sum of the addition amounts of the oxides is less than 5%, the amount of slag is not sufficient, resulting in deterioration of slag foreskin. On the other hand, when the sum of the added amounts of the oxides exceeds 12.0%, slag winding defects are likely to occur. Therefore, in the present invention, it is preferable to manage the sum of at least one of Al ₂ O ₃ , TiO ₂ and ZrO ₂ in the range of 5 to 12%.

Meanwhile, in the present invention, it is preferable to have Mo and Cr content so as to satisfy the following [Relationship 1]. In the case of the chemical composition that does not satisfy the following [Relationship 1], the occurrence of harmful phases according to the Mo and Cr content is increased, which does not satisfy the good physical properties of the weld.

[Relationship 1]

18-0.54 × Cr≤Mo≤24-0.53 × Cr

Moreover, in this invention, it is preferable to control the addition amount of each oxide so that following [Reaction Formula 2] may be satisfied. Specifically, in the present invention, it is preferable to manage so that the value defined by the following [Relationship 2] is 0.5 or less. If the value defined by [Equation 1] exceeds 0.5, it is difficult to ensure excellent welded part quality due to deterioration of weldability and crackability.

[Relationship 2]

{([Na ₂ O] + [K ₂ O] + [Li ₂ O] + 0.2 × [MnO]) / ([SiO ₂ ] + 0.5 × ([Al ₂ O ₃ ] + [TiO ₂ ] + [ZrO ₂ ]))}

The remaining component of the present invention is nickel (Ni).

Nickel (Ni) is an austenite stabilizing element and has an effect of increasing tensile strength by combining with Nb to form Ni ₃ Nb precipitates. More preferably, the Ni content may be limited to 58 to 70%. It is necessary to contain Ni at 58% or more in order to obtain the above-mentioned effect sufficiently, but if the content exceeds 70%, there is a possibility of causing a decrease in tensile strength.

In the present invention, in addition to the components described above, impurities that are not intended from the raw materials or the surrounding environment may inevitably be mixed in the normal manufacturing process, and thus, this cannot be excluded. Since these impurities are known to those skilled in the art, all of them are not specifically mentioned in the present specification. For example, in the present invention, V may be contained in an amount of 0.10% or less and Al in an amount of 0.10% or less.

On the other hand, the outer shell is a Ni-based alloy that serves to increase the content of Ni in the welded joint when welding, and the reason for limiting the content of Ni and other impurities as described above is high strength at high temperatures and excellent oxidation resistance, Creep This is to secure the resistance and toughness at cryogenic temperature and to reduce defects such as cracks during welding.

The diameter of the welding material is suitable about 0.9 ~ 1.6mm, the weight fraction of the outer shell is preferably 50 to 90% by weight fraction compared to the total welding material in consideration of the density difference between the density of the outer shell and the core.

This type of sheath, as is well known, can be represented by a single sheath structure surrounding the core of the alloying component.

By using the Ni-based flux cored wire that satisfies the alloy composition described above, all position welding is possible, and a weld metal having excellent tensile strength and impact toughness can be obtained.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are merely examples for describing the present invention in detail, and do not limit the scope of the present invention.

To prepare a welding wire having a component as shown in Table 1, the wire shell configuration and the components of the shell of the invention and comparative examples are the same, and only the flux component filled in the shell was different.

The metal sheath of the welding wire is in weight% C: 0.01 ~ 0.1%, Si: 0.1 ~ 1.0%, Mn: 1.5 ~ 5.0%, Cr: 18.0 ~ 23.0%, Ti: 0.01 ~ 1.0%, Nb: 1.0 ~ 3.0 %, Including the rest Ni.

Flux Cored Arc Welding (FCAW) was performed on each of the welding materials prepared as described above. In the case of FCAW, welding was performed with a heat input of 1.7 kJ / mm in Ar + 15-25% CO ₂ protective gas and 100% CO ₂ protective gas. The diameter of the wire for FCAW was 1.2 mm. Then, a slope was formed on the improved surface of the SM490 steel plate having a sheet thickness of 20 mm so that the improvement angle was 45 °, and the improved portion was buttered with a test wire to form a buttering layer. Thereafter, the root gaps of the buttered base materials were arranged to be 12 mm, and a paddle (steel material) in which the surface was buttered was similarly arranged on the side where the improvement was narrowed. This improvement was welded according to JIS Z 3111: 2005 to produce welded joints.

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

In addition, in this embodiment, the electron fine weldability was visually determined in consideration of arc stability and slag peelability, and evaluated by dividing into three levels of A (excellent), B (poor) and C (poor). In addition, the cracks and pores were also visually judged and shown in Table 2, and were evaluated as cracks (A) and cracks (B).

C Si Mn P + S Cr Mo Nb Ti Fe A * SiO ₂ MnO B * D * Inventive Example 1 0.03 0.15 1.6 0.01 18.5 9.0 1.2 0.2 1.0 0.7 2.0 2.064 7.8 0.19 Inventive Example 2 0.07 0.74 2.7 0.01 19.5 8.3 1.5 0.3 1.8 2.2 1.5 3.483 8.9 0.49 Inventive Example 3 0.02 0.85 3.5 0.01 20.1 8.85 2.0 0.01 2.9 0.2 1.2 4.515 11.5 0.16 Inventive Example 4 0.09 0.9 3.8 0.01 21.5 10.2 2.9 0.05 1.4 0.4 1.3 4.902 6.0 0.32 Inventive Example 5 0.02 0.35 3.5 0.01 20.5 11.3 1.7 0.07 0.7 0.5 1.8 4.515 7.0 0.26 Inventive Example 6 0.03 0.48 3.5 0.012 18.9 13.8 2.5 0.7 0.4 1.5 2.5 4.515 7.8 0.38 Inventive Example 7 0.04 0.6 4.8 0.032 19.2 12.7 2.4 0.25 0.8 2.5 2.2 4.9 10.4 0.47 Inventive Example 8 0.07 0.7 2.2 0.027 19.5 11.3 1.8 0.8 2.3 2.2 2.3 2.838 11.2 0.35 Comparative Example 1 0.03 0.36 2.0 0.01 18.0 7.5 1.2 0.2 1.0 0.5 0.36 2.58 12.5 0.15 Comparative Example 2 0.07 0.4 2.2 0.027 18.0 14.5 1.5 0.3 1.8 0.07 0.4 2.838 4.8 0.23 Comparative Example 3 0.02 0.7 2.5 0.035 17.5 8.5 2.0 0.01 2.9 0.02 3.1 3.225 6.3 0.11 Comparative Example 4 0.09 0.25 3.4 0.021 23.1 9.2 2.9 0.05 2.4 0.05 0.25 4.386 6.4 0.27 Comparative Example 5 0.02 1.2 4.0 0.01 18.9 9.0 1.7 0.07 0.7 3.1 2.0 2.5 5.4 0.77 Comparative Example 6 0.11 0.35 4.2 0.018 19.5 11.0 2.5 0.7 0.4 0.3 0.35 5.418 6.0 0.41 Comparative Example 7 0.04 0.65 1.2 0.017 20.2 10.5 2.4 0.25 0.8 0.07 0.12 0.4128 6.2 0.05 Comparative Example 8 0.04 0.8 2.2 0.027 19.5 11.3 1.8 0.8 0.8 1.3 1.2 3.5 5.1 0.53 Comparative Example 9 0.05 0.8 2.5 0.015 22.9 12.0 2.2 0.2 1.2 0.3 0.4 4.9 7.0 0.33

* In Table 1, each component is in weight percent and the remainder is Ni and impurities,

A * is Li ₂ O + Na ₂ O + K ₂ O, B * is Al ₂ O ₃ + TiO ₂ + ZrO ₂ , and

D * is {([Na ₂ O] + [K ₂ O] + [Li ₂ O] + 0.2 × [MnO]) / ([SiO ₂ ] + 0.5 × ([Al ₂ O ₃ ] + [TiO ₂ ] + [ZrO ₂ ]))}

to be.

division YS (MPa) TS (MPa) EL (%) Charpy Shock Absorption Energy (-196 ℃) Cracking Weldability
(Ar + 20% CO ₂ ) Weldability
(100% CO ₂ ) Inventive Example 1 475 760 40.5 70 A A A Inventive Example 2 455 755 42.5 68 A A A Inventive Example 3 435 730 48.5 65 A A A Inventive Example 4 444 720 49.5 63 A A A Inventive Example 5 460 735 48.5 65 A A A Inventive Example 6 472 711 50.4 80 A A A Inventive Example 7 449 690 52.4 90 A A A Inventive Example 8 480 776 39.5 70 A A A Comparative Example 1 430 630 50.5 105 A C B Comparative Example 2 460 810 22.2 25 A C C Comparative Example 3 450 680 42.5 60 C C B Comparative Example 4 490 820 27.4 25 B C C Comparative Example 5 467 765 45.4 66 C C B Comparative Example 6 438 800 33.2 26 B C B Comparative Example 7 429 722 40.4 80 B C B Comparative Example 8 433 750 41.4 50 A C B Comparative Example 9 450 712 48.4 70 C B B

As can be seen from Table 1 and Table 2, not only the alloy component of the present invention is satisfied, but also the relation 1 (18-0.54 × Cr ≤ Mo ≤ 24-0.53 × Cr) and the relation 2 ({([Na ₂ O] + [K ₂ O] + [Li ₂ O] + 0.2 × [MnO]) / ([SiO ₂ ] + 0.5 × ([Al ₂ O ₃ ] + [TiO ₂ ] + [ZrO ₂ ])) In the case of Inventive Examples 1 to 8, wherein the value defined by}) is 0.5 or less, it can be seen that the crack resistance and the electric field weldability are excellent. In addition, the tensile strength of the welded joint using the invention example 1-8 satisfied both 690MPa or more and -196 ℃ impact toughness 27J or more.

In contrast, in Comparative Example 1, the deposited metal did not reach the target tensile strength with an Mo content of less than 8.0%. In addition, since the content of TiO ₂ + ZrO ₂ exceeded 12%, the slag content was excessive, so that the welding part and the slag were not separated smoothly during the electric field welding. As a result, the slag mixing occurred and the electric field weldability was insufficient.

In Comparative Example 2, the Mo content was more than 14.0% and the impact toughness was lowered. In addition, since the slag content was too low as the content of TiO ₂ + ZrO ₂ was less than 5.0%, the slag foreskin property was low and it was difficult to secure good weld beads.

In Comparative Example 3, the Cr content was less than 18.0%, and thus the target tensile strength was not secured, and the relationship 1 was not satisfied.

In Comparative Example 4, the Cr content was more than 22.0%, which did not satisfy the relation 1, and cracks occurred in the weld bead. In addition, since the Na ₂ O content was less than 0.1%, the arc generation was not easy due to the lack of the ionization potential reduction effect of the arc, it was difficult to secure a stable arc during welding.

In Comparative Example 5, the Si content exceeded 1.0% and the crack resistance decreased. In addition, due to the high vapor pressure of Na ₂ O content of more than 3.0% excessive weld fume (Fume) was generated, the value calculated from the above equation 2 exceeds 0.5 slag fluidity is also excessive, so that the slag shape of the vertical posture worsens Beads flowed down.

In Comparative Example 6, the C content was more than 0.1%, so that the crack resistance was decreased and the target impact toughness was not satisfied. In addition, bead spreadability was inferior to the MnO content of less than 0.5%, making it difficult to secure good welding workability.

In Comparative Example 7, the Mn content was less than 1.5% and the crack resistance was poor. In addition, bead spreadability was inferior to MnO content of less than 0.5%, and good weldability could not be secured.

In Comparative Example 8, the composition component satisfies the scope of the present invention, but does not satisfy the relational expression 2, and thus did not secure yield.

In Comparative Example 9, the composition component satisfies the scope of the present invention, but does not satisfy the relational formula 1, and thus it did not secure good crackability.

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 can be made without departing from the technical spirit of the present invention described in the claims. It will be obvious to those of ordinary skill in the field.

Claims (2)

In a flux cored wire in which a metal shell is filled with flux, the wire has a weight of itself, C: 0.01 to 0.1%, Si: 0.1 to 1.0%, Mn: 1.5 to 5.0%, and P + S: 0.04% Below, Cr: 18.0-23.0%, Mo: 8.0-14.0%, Ti: 0.01-1.0%, Nb: 1.0-3.0%, Fe: 0.01-5.0%, SiO ₂ : 0.1-3.0%, MnO: 0.5-5 %, At least one of Li ₂ O, Na ₂ O and K ₂ O: 0.1-3.0%, at least one of Al ₂ O ₃ , TiO ₂ and ZrO ₂ : 5-12%, including residual Ni and unavoidable impurities And Ni-based flux cored wire for cryogenic Ni alloy steels, which satisfies the following [Relational Expression 1], and the value defined by the following [Relational Expression 2] satisfies 0.5 or less.
[Relationship 1]
18-0.54 × Cr≤Mo≤24-0.53 × Cr
[Relationship 2]
{([Na ₂ O] + [K ₂ O] + [Li ₂ O] + 0.2 × [MnO]) / ([SiO ₂ ] + 0.5 × ([Al ₂ O ₃ ] + [TiO ₂ ] + [ZrO ₂ ]))}
The method according to claim 1, wherein the outer skin is in its own weight%, C: 0.01 ~ 0.1%, Si: 0.1 ~ 1.0%, Mn: 1.5 ~ 5.0%, Cr: 18.0 ~ 23.0%, Ti: 0.01 ~ 1.0% , Nb: 1.0% to 3.0%, Ni-based flux cored wire for cryogenic Ni alloy steel, including the remaining Ni and inevitable impurities.