KR101647148B1 - Flux cored arc weld wire for high tensile steel and weld metal joint using the same - Google Patents

Abstract

The present invention relates to a flux cored arc welding wire capable of improving low temperature impact toughness of a weld metal portion during flux cored arc welding, and a weld metal portion using the same, wherein the wire comprises 0.03 to 0.15% of C, : 0.3 to 1.4%, Mn: 1.2 to 3.5%, Ni: 0.1 to 3.0%, Ti: 0.001 to 0.3%, TiO ₂ : 3.5 to 9.0%, Mg: 0.001 ~ 0.02%, Nb: 0.5 % or less, V: 0.5% or _{less, SiO 2: 0.2 ~ 2.0%} , Al 2 O 3: 0.3 ~ 1.0%, the alkali oxide: 0.10 to 1.5% alkali or alkaline earth metal-based fluorine compounds : 0.025 to 1.0% of Ti and TiO ₂ are added alone or in combination, and the balance satisfies the relationship of 4% ≤Ti + TiO ₂ ≤9% and the remainder is Fe and inevitable impurities. And a welded metal part using the wire.

Flux cored arc welds, weld metal joints, acicular ferrites, high tensile steels,

Description

TECHNICAL FIELD [0001] The present invention relates to a flux cored arc welding wire for use in a high strength steel, and a flux cored arc welding metal using the same. BACKGROUND ART < RTI ID = 0.0 >

Field of the Invention [0001] The present invention relates to a flux cored arc weld (FCAW) wire, and more particularly, to a flux cored arc welding wire for high strength steels capable of improving low temperature impact toughness of an FCAW weld metal portion and a weld metal portion using the same .

In recent years, the demand for low-temperature toughness of welding steels has become stricter due to the expansion and enlargement of applications of deep-sea areas in ships and offshore structures. Welding is inevitable in order to produce such high-strength steel steels efficiently and efficiently. The most widely used welding technique is the Flux Cored Arc Weld (FCAW) technology.

In order to secure the stability of such a large welded structure, high strength and low temperature impact toughness are required. Welding materials of a wide range of strengths, such as Yield strength (YP) of 320 to 420 MPa and High strength of 460 to 500 MPa, are applied to offshore structures.

In order to satisfy the design requirements specific to offshore structures, the requirement for additional quality specifications, especially low temperature toughness, is strict in the use of high-strength steels, etc., And most of the welding materials for offshore structures require the reduction of the weld metal and the miniaturization of the welded metal structure in order to ensure the Charpy low temperature impact toughness up to about -40 ° C and -60 ° C.

Generally, a weld metal joint formed during welding is formed by melting a welding material and diluting a part of the steel to form a molten pool, and coagulate to form a coarse columnar structure, and austenite grain boundaries Therefore, coarse grain boundary ferrite, Widmanstatten ferrite, martensite and martensite Austenite constituent are formed, and the weld metal part is the area where impact toughness is most deteriorated in the high strength welded part.

Therefore, in order to ensure the stability of the welded structure, it is necessary to control the microstructure of the welded metal portion to secure impact toughness of the welded metal portion. In order to solve this problem, Japanese Patent Application Laid-Open No. 8-10982, for example, discloses a technique for defining the components of a welding material. However, the above patent does not control the microstructure, There is a problem that it is difficult to secure sufficient stable welding metal toughness in the welding material.

An aspect of the present invention is to provide a flux cored arc welding wire capable of solving the above problems and ensuring low temperature impact toughness of a weld metal portion during flux arc welding for high tensile steels and a weld metal portion having excellent low- will be.

The present invention is a wire the total weight%, C: 0.03 ~ 0.15% , Si: 0.3 ~ 1.4%, Mn: 1.2 ~ 3.5%, Ni: 0.1 ~ 3.0%, Ti: 0.001 ~ 0.3%, TiO 2: 3.5 ~ 9.0 %, Mg: 0.05 ~ 1.5% , Al: 0.5% or less, B: 0.001 ~ 0.02%, Nb: 0.5% or less, V: 0.5% or _{less, SiO 2: 0.2 ~ 2.0%} , Al 2 O 3: 0.3 ~ 1.0 % alkali oxide: 0.10 to 1.5% alkali or alkaline earth metal-based fluorine compounds is added alone or in combination 0.025 to 1.0%, wherein Ti and TiO ₂ are satisfy a relationship of 4% TiO ₂ + ≤Ti% ≤9 , And the balance of Fe and unavoidable impurities.

Further, the present invention provides a weld metal part made of the above wire,

Wherein the weld metal portion contains 0.01-0.1% of C, 0.1-0.7% of Si, 0.5-2.0% of Mn, 0.01-3.0% of Ni, 0.01-0.5% of Mo, 0.01-0.08% of Ti, P: 0.03% or less, S: 0.03% or less, O: 0.02-0.08%, Al: 0.001% -0.010%, and Mg: 0.01% or less, and the Ti and O satisfy the relation of 0.3? Ti / O? 2.0, and the remainder include Fe and other impurities.

The present invention relates to a weld metal part having high tensile strength of 500 MPa or more in tensile strength in FCAW welding with a weld heat input range of 20 kJ / cm and at the same time ensuring excellent low-temperature impact toughness, TiO- (Ti, B) A flux cored arc welding wire for high tensile strength steel which can accelerate needle-like ferrite transformation in the weld metal portion and secure the low-temperature impact toughness of an excellent FCAW weld metal portion by controlling the nitrides and the effective B and (Nb, V, And a welded metal portion there through.

Hereinafter, the present invention will be described in detail.

As a result of investigating the kinds and sizes of oxides on the needle-shaped ferrite which are known to be effective for impact toughness of the weld metal part, the present inventors have found that the addition of TiO- (Ti, V) N and the effective B and the control of addition of Al, Nb and V It is found that the amount of intergranular ferrite and needle-like ferrite changes in the weld metal part and thus the impact toughness value of the weld metal part changes.

Based on these studies, in the present invention,

[1] Cold rolled steel strip and flux design for TiO- (Ti, B) N complex oxide formation

When the TiO- (Ti, B) N complex acid or nitride is formed on the weld metal portion, the weld metal portion has an irregular ferrite structure of 70% or more. Further, it has been recognized that the composite acid or nitride such as fine TiO- (Ti, V) N can be distributed in the weld metal portion to improve the impact resistance at low temperature, and the present invention has been accomplished.

In the present invention, in order to improve the toughness by transforming more than 70% of the needle-shaped ferrite in the weld metal portion through the complex acid and the nitride, the content of Ti in the composition of the weld metal is preferably 0.01 to 0.08%, B is in the range of 0.0005 to 0.005% The steel shell and the flux constituting the cold-rolled steel of the wire must contain 0.001 to 0.3% of Ti, 0.001 to 0.020% of B, 3.5 to 9.0% of TiO ₂ , and the welding wire is produced to contain _{4% ≤Ti + TiO 2 ≤9 %%} .

[2] Cold rolled steel strip and flux design for effective B generation and (Al, Nb, V) N suppression in weld metal

In the present invention, it is preferable that the composition of the weld metal portion is Nb: 0.05% or less so as to minimize grain growth and generation of intergranular ferrite through effective B generation and (Al, Nb, V) N suppression to secure 70% or more acicular ferrite transformation in austenite, V is 0.05% or less, B is 0.0005-0.005%, N is 0.002-0.010%, Al is 0.010% or less, 0.01? (Nb + V) / Ti? 2.0 and 0.1? Al / N? The steel shell and the flux constituting the cold-rolled steel wire of the welding wire are composed of 0.001-0.020% of B, 0.5% or less of Nb, 0.5% or less of V, 0.5% or less of Al, 3.5-9.0% of TiO ₂ and 4% + TiO _{2 < =} 9%.

[Flux cored welding wire]

Hereinafter, the flux cored arc welding wire of the present invention will be described in detail. The wire is formed by filling a flux into a steel shell made of cold-rolled steel and a U-shaped steel shell.

First, the composition range of the wire will be described in detail. Hereinafter, it is expressed as% by weight based on the total weight of the wire.

The content of carbon (C) is preferably 0.03 to 0.15%.

C is preferably added in an amount of 0.03% or more as an indispensable element for securing the strength of the weld metal and securing the welding hardenability. However, if the content exceeds 0.15%, the weldability is greatly reduced and the weld metal low temperature crack is likely to occur Impact toughness is greatly reduced.

The content of silicon (Si) is preferably 0.3 to 1.4%.

If the content of Si is less than 0.3%, the deoxidizing effect in the weld metal is insufficient and the flowability of the weld metal is lowered. When the Si content is more than 1.4%, the transformation of the MA constituent in the weld metal is promoted, And adversely affects the weld crack susceptibility, which is not preferable.

The content of manganese (Mn) is preferably 1.2 to 3.5%.

Mn is effective for improving the deoxidation action and strength in the steel, and solidifies the substitution type solid solution in the matrix to solidify the matrix to secure strength and toughness. For this purpose, Mn is preferably contained in an amount of 1.2% or more. However, if it exceeds 3.5%, it is undesirable because it forms a low-temperature transformed structure.

The content of titanium (Ti) is preferably 0.001 to 0.3%. The TiO ₂ content is preferably 3.5 to 9.0%, and it is preferable that 4% ≤Ti + TiO ₂ ≤9% is satisfied simultaneously.

Ti is an indispensable element in the present invention because it combines with O to form 0.3? Ti / O? 2.0 and a fine TiO- (Ti, B) N complex oxide in the weld metal, that is, the weld metal. In order to obtain such fine TiO 2 oxides and effective TiN composite precipitates, it is necessary to add not less than 0.001% of Ti and not less than 4.0% of Ti + TiO ₂ to the welding wire. However, when Ti exceeds 0.3% or Ti + TiO ₂ is 9.0% The coarse Ti oxide and the coarse TiN precipitate are formed, which is undesirable.

In addition, TiO _{2, which} is a main component of titania flux cored arc welding materials, is added in an amount of 3.5% or more for slag formation and arc stability. In reaction between slag and molten metal during melting, And a considerable amount remains even after solidification. These will act as needle-like ferrite nucleation sites in the form of TiO 2 in the weld metal, but above 9.0% will reduce impact and fracture toughness in the weld metal.

The content of nickel (Ni) is preferably 0.1 to 3.0%.

Ni is an effective element that improves the strength and toughness of the matrix by solid solution strengthening. It is preferable that the Ni content is 0.1% or more. If it exceeds 3.0%, the incombustibility is greatly increased and the possibility of occurrence of hot crack Which is undesirable.

The content of boron (B) is preferably 0.001 to 0.02%.

B is required to be 0.001% or more in order to suppress intergranular ferrite transformation by segregation at grain boundaries as an element for improving the incombustibility, but when it exceeds 0.02%, the effect is saturated and weld hardening property is greatly increased to promote martensite transformation, It is undesirable because crack generation and toughness are lowered. Therefore, the B content is limited to 0.001 to 0.02%.

The content of magnesium (Mg) is preferably 0.05 to 1.5%.

Mg is required to be 0.05% or more as an essential element for deoxidation during welding, but if it exceeds 1.5%, the effect is saturated and the internal oxide is coarsened, which adversely affects the weld metal toughness. Therefore, the Mg content is limited to 0.05 to 1.5%.

The content of vanadium (V) and niobium (Nb) is preferably limited to 0.5% or less.

V and Nb are elements necessary for forming fine precipitates of V (C, N) and Nb (C, N) in the weld metal portion. However, when the content in the wire exceeds 0.05%, the formation of intergranular ferrite in the weld metal part is promoted and a light image such as carbide is formed in the weld metal part, which adversely affects the toughness of the weld metal part, In the design of the wire, the component addition limit amount of each of V and Nb is limited to 0.5% or less.

The content of aluminum (Al) is preferably 0.5% or less. In particular, in order to minimize the content of the welding wire, it is preferable to use a steel sheath made of Al having a steel content of 0.005% or less.

In titania-based flux cored arc welding, Al is added to the steel shell of the flux and cold-rolled steel as a deoxidizing and denitrating agent and floated in most of the slag during welding, but a very small amount of Al remains as Al oxide and nitride in the weld metal after final coagulation . These very small amounts of Al do not have a great influence on the low temperature toughness. However, when a cold rolled steel sheet killed with a large amount of aluminum is used, or when the total amount of Al added to the cold rolled steel strip and flux is 0.5% or more, the bead viscosity increases, The electric conductivity of the slag is lowered and the arc stability is deteriorated during the welding operation and coarse Al ₂ O ₃ is formed to hinder the formation of TiO 2 oxide required for improving toughness, so that the content of Al in the welding wire is preferably 0.5% or less Do.

The content of the alkaline oxide is preferably 0.1 to 1.5%. The alkali oxides are preferably K, Na, Li-based oxides.

The above alkaline oxides should be added in an amount of 0.1% or more in order to facilitate the generation of arc due to low arc ionization potential during welding and to maintain a stable arc during welding. However, when the content exceeds 1.5%, welding fumes And the slag viscosity of the molten pool is excessively reduced in the rutile system, in which TiO ₂ is the main slag component, to form an unstable bead, so that it is limited to within 1.5%.

The SiO ₂ content is preferably 0.2 to 2.0%.

When SiO _{2 content} is less than 0.2%, slag application is poor, and elaborate workability and bead shape are poor. When the SiO _{2 content} is more than 2.0%, coagulation of molten slag is delayed and electron weldability is poor. And the impact toughness is lowered.

The content of Al ₂ O ₃ is preferably 0.3 to 1.0%. Al ₂ O ₃ , when added in an amount of 0.3% or more in the titania-based slag component, keeps the melting point of the molten slag appropriately to maintain the electron weldability and bead shape. When the content exceeds 1.0%, the bead viscosity increases and the electrical conductivity of the melted slag decreases Since the arc stability is deteriorated during welding work, it is limited to 0.3 ~ 1.0%.

The amount of the alkali or alkaline earth metal fluorine compound alone or in combination is preferably limited to 0.025 to 1.0%.

These fluorides are added to the inside of the welding wire by adding 0.025% or more. As a result, fluorine is generated in the arc in a high-temperature arc and reacts with hydrogen during welding to cause a dehydrogenation reaction, thereby effectively reducing the diffusible hydrogen. Since fume is excessively generated due to the characteristics of vapor pressure and TiO ₂ forms an unstable bead by excessively reducing the slag viscosity of the molten pool in the rutile system, which is a main slag component, it is limited to 1.0% or less.

The remainder consists of Fe and unavoidable impurities.

[Flux cored arc weld metal part]

Hereinafter, the weld metal portion manufactured using the wire of the present invention will be described in detail.

The weld metal portion produced by using the flux cored arc welding wire of the present invention is composed of 0.01 to 0.1% of C, 0.1 to 0.7% of Si, 0.5 to 2.0% of Mn, 0.01 to 3.0% of Ni, 0.01 to 3.0% of Ni, 0.001 to 0.08% of N, 0.0001 to 0.05% of V, 0.0001 to 0.05% of B, 0.0005 to 0.005% of B, 0.002 to 0.010% of N, 0.03% or less of P, (Nb + V) / Ti? 2.0, 0.1? Al / N? 0.5, 0.3? Ti / O? 2.0, and the remainder is Fe And other impurities.

The content of carbon (C) in the weld metal portion is preferably 0.01 to 0.1%.

C is preferably added in an amount of 0.01% or more as an indispensable element in order to ensure the strength of the weld metal and ensure welding hardenability. However, when the content exceeds 0.1%, the weldability is greatly decreased and the weld metal low temperature crack is likely to occur The impact toughness is largely lowered, so it is limited to 0.01 to 0.1%.

The content of silicon (Si) in the weld metal portion is preferably 0.1 to 0.7%.

When the content of Si is less than 0.1%, the hardenability is lowered and the strength is difficult to secure. When the Si content is more than 0.7%, the transformation of the MA constituent in the weld metal is promoted, And increases susceptibility to weld cracking.

The content of manganese (Mn) is preferably 0.5 to 2.0%.

Mn is an austenite-forming element in the steel, and is effective in improving the toughness of the welded joint, and is incorporated in the matrix to improve strength and toughness. For this purpose, Mn is preferably contained in an amount of 0.5% or more. However, if it exceeds 2.0%, it is undesirable because it forms a low-temperature transformed structure.

The content of nickel (Ni) is preferably 0.01 to 3.0%.

Ni is an effective element which improves the strength and toughness of the matrix by solid solution strengthening. It is preferable that Ni content is 0.01% or more, but when it exceeds 3.0%, the incombustibility is greatly increased and the possibility of occurrence of high temperature crack Which is undesirable.

The content of titanium (Ti) in the weld metal portion is preferably limited to 0.01 to 0.08%. At the same time, it is preferable that 0.3? Ti / O? 2.0 is satisfied. More than 0.01% of Ti is an indispensable element in the present invention because it combines with O or N during welding to form a fine TiO- (Ti, B) N composite oxide in the weld metal portion, that is, the weld metal. Particularly, in order to obtain a fine TiO 2 oxide which is a nucleation site effective for formation of fine needle-like ferrite during the solidification, a constant Ti / O ratio satisfying 0.3? Ti / O? 2.0 is required. However, when Ti is more than 0.08%, coarse Ti oxides and coarse TiN precipitates are formed and low temperature toughness and fracture toughness are lowered.

The content of vanadium (V) and niobium (Nb) is preferably limited to 0.0001 to 0.05% or less. V and Nb are elements necessary for forming fine precipitates of V (C, N) and Nb (C, N) in the weld metal portion. The addition of vanadium and niobium content of 0.0001% or more to the weld metal promotes the formation of intergranular ferrite in the weld metal, but when vanadium and niobium are added to the weld metal in excess of 0.05%, excess carbide, nitride And the secondary hardening due to reheating such as heat treatment after welding is caused, and the toughness of the weld metal portion is adversely affected, so that the content of vanadium and niobium is limited to 0.0001 to 0.05%, respectively.

(Nb + V) / Ti of the weld metal portion is preferably 0.01? (Nb + V) / Ti? 2.0.

Considering the reduction of rutile as a basic flux component in the titania-based flux cored wire, the effective composition ratio of ferrite with respect to precipitation of niobium and vanadium to titanium should be (Nb + V) / Ti of at least 0.01, (Nb + V) / Ti < / = 2.0, because the precipitates of niobium and vanadium are excessively larger than those of titanium, which is an effective site for microcrystalline ferrite nucleation, and secondary hardening occurs around these grain boundaries. do.

The content of boron (B) is preferably 0.0005 to 0.005%.

B is required to be 0.0005% or more in order to suppress intergranular ferrite transformation by being segregated at grain boundaries as an element for improving the incombustibility, but when it exceeds 0.005%, the effect is saturated and welding hardenability is greatly increased, thereby promoting martensite transformation, It is undesirable because crack generation and toughness are lowered. Therefore, the B content is limited to 0.0005 to 0.005%.

The content of nitrogen (N) is preferably 0.002 to 0.010%.

Nitrogen remains in the weld over 0.002% and binds to Ti and Al to form TiN and AlN. However, when the nitrogen content exceeds 0.010%, the amount of dissolved nitrogen is increased and the toughness is decreased 0.002 to 0.010%.

The ratio of nitrogen (N) to aluminum (Al) is preferably 0.1? Al / N? 0.5.

If the Al / N of the weld is less than 0.1, the amount of dissolved nitrogen in the weld is too high or the denitrification of Al is insufficient, and the low temperature toughness is decreased. When Al / N is 0.5 or more, Al becomes excessive, , It is limited to 0.1? Al / N? 0.5.

Phosphorus (P) is an element affecting low-temperature toughness. It is limited to 0.03% or less because it gives rise to a post-heatpipe during multi-layer welding,

Sulfur (S) is an element affecting high-temperature cracking. It is segregated in the vicinity of the weld line in the case of super-layer welding to form a low-melting sulphide, causing high temperature cracking during the solidification process.

The oxygen (O) content of the weld metal portion is preferably 0.02 to 0.08%.

Oxygen in the weld is determined by the reaction between the deoxidizing element of the molten metal and the slag and the protective gas during the welding, and the dissolved oxygen of the weld metal in the acidic flux cored wire is mostly present in the form of oxidizing agent, Or more in the solidification reaction with Ti, Mg, Zr, Nb, V, Si, Mn or the like to form a complex oxide and effectively functions as a site for forming an acicular ferrite in the austenite. When the content is more than 0.06% As a result of the formation of large amounts of oxides in the welded part and the enlargement of the formed openings, the low temperature impact and fracture toughness are lowered, so that the range is limited to 0.02 to 0.08%.

The content of aluminum (Al) is preferably 0.001 to 0.01%.

In the titania-based flux cored arc welding, when Al is added in an amount of 0.001% or more, it acts as a deoxidizing and denitrating agent in the molten metal and is present in a small amount as Al oxide and nitride to promote ferrite nucleation and reduce the amount of oxygen in the weld metal. If it exceeds 0.01%, coarse Al ₂ O ₃ is formed to inhibit the formation of Ti oxide necessary for toughness improvement. Therefore, the content of Al contained is limited to 0.01% or less.

The content of magnesium (Mg) is preferably 0.01% or less.

Mg is an indispensable element for deoxidation during welding and forms a complex oxide by oxidation and reduction reaction between the molten metal and slag to act as a nucleation site of the fine needle-like ferrite. When it exceeds 0.01%, the effect is saturated, Which is undesirable because it affects the weld metal toughness badly. Therefore, the Mg content is limited to 0.01% or less.

In addition, the weld metal microstructure produced using the flux cored arc welding wire of the present invention has an area fraction of 70% or more of fine acicular ferrite, which is known as a structure favorable to low-temperature impact toughness, Is composed of at least one of intergranular ferrite, Widmasttaten ferrite and bainite.

Preferably, the weld metal portion finely distributes TiO- (Ti, V) N composite acid and nitride having an average size of 0.80 占 퐉 or less to the weld metal portion in an area fraction of 0.25 to 0.35%. If the area fraction of these complex acids and nitrides is less than 0.25%, the role of fine needle-shaped ferrite as a nucleation site in the austenite is insufficient during cooling, and coarse grain boundary ferrite is produced and grown first, resulting in low temperature toughness .

On the other hand, if a large number of coarse metal particles exceeding 0.80 탆 exist in the weld metal portion, or if the area fraction exceeds 0.35%, if the precipitates are excessively left, they deteriorate the low temperature toughness. V) N Composite Acid and nitride are uniformly distributed in the weld metal at an area fraction of 0.25 to 0.35%.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following examples.

(Example)

Table 1 shows that the flux cored wires of the inventive material and the comparative material combined with the flux composition and the cold-rolled steel shell prepared according to Table 2 were welded at a rate of 20 J / cm with a 100% CO ₂ protective gas. In order to demonstrate the effect of the present invention, the composition ratios between the weld metal sub-alloy components and the elements formed after welding are shown in Table 3.

Test specimens for the evaluation of the mechanical properties of the welded metal parts as described above were taken from the center of the welded metal part. The tensile test specimens were made with KS Specification No. 4 (KS B 0801) No. 4, 10 mm / min. Impact test specimens were prepared in accordance with KS (KS B 0809) No. 3 test specimens.

The size, number and spacing of the oxides, which have a significant impact on the impact toughness of the weld metal, were measured by point counting using an image analyzer and an electron microscope. The impact toughness of the FCAW weld metal was evaluated using an impact test specimen after FCAW welding and evaluated at Charge impact test at -40 ° C.

division C Fe and others Mn Si Ni Mg B Al Ti + TiO ₂ K ₂ O Na ₂ O SiO ₂ F Nb V Steel sheath Inventory 1 0.02 92.07 1.68 0.59 0 0.3 0.014 0 4.12 0.07 0.31 0.49 0.32 0.02 0.02 A Inventory 2 0.02 91.33 1.68 0.59 0 0.3 0.014 0 4.2 0.07 0.31 0.49 0.4 0.11 0.45 A invent
Re 3 0.02 89.57 1.68 0.59 0.42 0.7 0.014 0.002 77.6 0.07 0.31 0.49 0.5 0.02 0.03 A invent
4 0.02 88.22 1.68 0.59 0.42 0.8 0.014 0.002 7.6 0.07 0.31 0.49 0.5 0.1 0.44 A invent
Re 5 0.03 87.05 1.68 0.59 0.97 0.9 0.014 0.002 7.4 0.07 0.31 0.49 0.5 0.017 0.02 A invent
6 0.03 87.04 1.68 0.59 0.97 0.9 0.014 0.002 7.4 0.07 0.31 0.49 0.5 0.11 0.41 A invent
Re 7 0.03 84.92 1.68 0.59 1.45 0.8 0.014 0 6.8 0.07 0.31 0.49 0.5 0.015 0.03 A invent
Re 8 0.03 84.57 1.68 0.59 1.45 0.8 0.014 0 6.8 0.07 0.31 0.49 0.5 0.13 0.44 A invent
Re 9 0.04 81.03 1.68 0.59 2.2 0.3 0.0014 0 6.8 0.07 0.31 0.49 0.5 0.02 0.02 A invent
Re 10 0.04 81.92 1.68 0.59 2.2 0.3 0.014 0.003 6.8 0.07 0.31 0.49 0.5 0.12 0.43 A Comparison 1 0.02 92.07 1.68 0.59 0 0.3 0.014 0 4.12 0.07 0.31 0.49 0.32 0.02 0.02 B Comparative material 2 0.02 91.33 1.68 0.59 0 0.3 0.014 0 4.2 0.07 0.31 0.49 0.4 0.11 0.45 B Comparative material 3 0.02 89.57 1.68 0.59 0.42 0.7 0.014 0.002 7.6 0.07 0.31 0.49 0.5 0.02 0.03 B Comparison 4 0.02 88.22 1.68 0.59 0.42 0.8 0.014 0.002 7.6 0.07 0.31 0.49 0.5 0.1 0.44 B compare
Re 5 0.03 87.05 1.68 0.59 0.97 0.9 0.014 0.002 7.4 0.07 0.31 0.49 0.5 0.017 0.02 B compare
6 0.03 87.04 1.68 0.59 0.97 0.9 0.014 0.002 7.4 0.07 0.31 0.49 0.5 0.11 0.41 B compare
Re 7 0.03 84.92 1.68 0.59 1.45 0.8 0.014 0 6.8 0.07 0.31 0.49 0.5 0.015 0.03 B compare
Re 8 0.03 84.57 1.68 0.59 1.45 0.8 0.014 0 6.8 0.07 0.31 0.49 0.5 0.13 0.44 B Comparative material 9 0.04 81.03 1.68 0.59 2.2 0.3 0.014 0 6.8 0.07 0.31 0.49 0.5 0.02 0.02 B Comparative material 10 0.04 81.92 1.68 0.59 2.2 0.3 0.014 0.003 6.8 0.07 0.31 0.49 0.5 0.12 0.43 B

division C Si Mn P S Ti B (ppm) Al A 0.02 0.005 0.4 0.008 0.008 0.005 8 0.001 B 0.02 0.003 0.2 0.011 0.008 - - 0.030

division C Si Mn P S Ni Ti B (ppm) N (ppm) Nb (ppm) V (ppm) O (ppm) Al Al / N (Nb + V) / Ti Ti / O invent
1 0.04 0.45 1.3 0.009 0.01 0.04 0.021 31 42 7 5 280 0.001 0.24 0.06 0.75 invent
Re 2 0.05 0.42 1.3 0.01 0.012 0.04 0.023 28 62 64 154 310 0.001 0.16 0.95 0.74 invent
Re 3 0.06 0.4 1.4 0.012 0.011 0.45 0.058 32 40 7 6 380 0.002 0.50 0.02 1.53 invent
4 0.06 0.39 1.3 0.011 0.012 0.44 0.051 31 82 56 135 575 0.002 0.24 0.37 0.89 invent
Re 5 0.04 0.44 1.4 0.01 0.008 1.1 0.058 37 45 5 5 610 0.002 0.44 0.02 0.95 invent
6 0.05 0.39 1.2 0.009 0.011 One 0.041 40 60 60 121 520 0.002 0.33 0.44 0.79 invent
Re 7 0.05 0.35 1.3 0.018 0.008 1.4 0.043 29 41 6 180 490 0.001 0.24 0.43 0.88 invent
Re 8 0.04 0.42 1.2 0.011 0.01 1.5 0.051 28 68 65 144 480 0.001 0.15 0.41 1.06 invent
Re 9 0.05 0.48 1.4 0.01 0.007 2.2 0.043 34 51 6 7 420 0.001 0.20 0.03 1.02 invent
Re 10 0.06 0.39 1.4 0.015 0.009 2.3 0.06 33 84 68 151 440 0.004 0.48 0.37 1.36 compare
1 0.05 0.36 1.4 0.009 0.011 0.03 0.013 21 40 7 7 550 0.006 1.50 0.12 0.24 compare
Re 2 0.05 0.43 1.2 0.015 0.012 0.04 0.014 21 63 84 170 530 0.007 1.11 1.81 0.26 compare
Re 3 0.06 0.46 1.4 0.011 0.008 0.43 0.062 24 44 6 6 570 0.006 1.36 0.02 1.09 compare
4 0.05 0.4 1.3 0.015 0.011 0.46 0.02 27 64 77 169 450 0.008 1.25 1.23 0.44 compare
Re 5 0.05 0.48 1.4 0.012 0.014 1.1 0.044 32 51 7 4 570 0.008 1.57 0.03 0.77 compare
6 0.05 0.38 1.2 0.013 0.01 1.1 0.036 32 61 85 182 480 0.006 0.98 0.74 0.75 compare
Re 7 0.06 0.42 1.1 0.018 0.008 1.5 0.039 29 41 7 8 650 0.009 2.20 0.04 0.60 compare
Re 8 0.05 0.42 1.4 0.018 0.008 1.5 0.043 26 73 70 180 590 0.007 0.96 0.58 0.73 compare
Re 9 0.05 0.39 1.3 0.013 0.011 2.3 0.04 21 40 8 8 590 0.006 1.50 0.04 0.68 compare
Re 10 0.05 0.46 1.3 0.014 0.008 2.1 0.053 27 70 86 177 550 0.008 1.14 0.50 0.96

division
Welding process Complex oxide Welded metal part Mechanical property Welding Process Welding heat input
(kJ / cm) Area fraction
(%) Average size
(탆) acicular
ferrite (%) The tensile strength
(MPa) vE- ₄₀
(J) Inventory 1 FCAW 20 0.265 0.61 81 547 84 Inventory 2 FCAW 20 0.267 0.78 72 533 58 Inventory 3 FCAW 20 0.314 0.58 87 563 119 Invention 4 FCAW 20 0.357 0.74 83 549 91 Invention Article 5 FCAW 20 0.319 0.69 90 574 136 Inventions 6 FCAW 20 0.333 0.66 83 577 84 Invention 7 FCAW 20 0.343 0.71 92 594 146 Invention 8 FCAW 20 0.354 0.73 84 610 89 Invention 9 FCAW 20 0.328 0.69 89 627 141 Inventions 10 FCAW 20 0.33 0.77 81 613 93 Comparison 1 FCAW 20 0.233 0.92 50 862 78 Comparative material 2 FCAW 20 0.241 0.93 39 858 48 Comparative material 3 FCAW 20 0.374 0.88 72 750 56 Comparison 4 FCAW 20 0.389 0.85 39 820 41 Comparative material 5 FCAW 20 0.394 0.74 57 650 69 Comparative material 6 FCAW 20 0.413 0.86 43 840 35 Comparison 7 FCAW 20 0.402 0.8 75 841 74 COMPARISON 8 FCAW 20 0.407 0.93 69 810 56 Comparative material 9 FCAW 20 0.365 0.74 68 790 64 Comparative material 10 FCAW 20 0.394 0.73 63 815 29

As shown in Table 4, the weld metal portion made using the inventive flux cored arc welding wire was made of the composite material of TiO- (Ti, B) N and V, Nb (C, N) The area ratio was in the range of 0.25 to 0.35% and the size of the precipitate was 0.8 μm or less. The comparative material remains in the weld metal portion in the form of a composite precipitate having a surface area of 0.25% or 0.37 to 0.40% or a precipitate size of 0.8 μm or more, which is comparatively homogeneous compared to the comparative material, and a fine composite precipitate And the area ratio of the inventive material is reduced by about 15% as compared with the comparative material.

On the other hand, the microstructure of the welded metal portion produced by using the inventive flux cored arc welding wire of the present invention has a high fraction of 70% or more in all of the needle-shaped ferrite phase fractions. Therefore, the welded metal portion FCAW-welded using the welding wire of the present invention is composed of about 70% or more of needle-like ferrite and the remaining grain boundary ferrite, Widmasttaten ferrite and some bainite, and has high tensile strength of 500 MPa or more Excellent weld metal part impact characteristics are shown.

Claims (7)

A steel shell, and a flux filled in the steel shell, wherein the content of Al in the steel shell is 0.005% or less, Wherein the total weight percentage of the wire is 0.03 to 0.15% of C, 0.3 to 1.4% of Si, 1.2 to 3.5% of Mn, 0.1 to 3.0% of Ni, 0.001 to 0.3% of Ti, 3.5 to 9.0% of TiO ₂ , Mg: 0.05 ~ 1.5%, Al : 0.5% or less, B: 0.001 ~ 0.02%, Nb: 0.5% or less, V: 0.5% or _{less, SiO 2: 0.2 ~ 2.0%} , Al 2 O 3: 0.3 ~ 1.0%, 0.1 to 1.5% of an alkali metal oxide, 0.025 to 1.0% of an alkali or alkaline earth metal fluorine compound, and Ti and TiO ₂ satisfy the relation of 4%? Ti + TiO _2? 9% Flux cored arc welding wire for high strength steels comprising Fe and unavoidable impurities. delete A weld metal part made of the wire of claim 1, Wherein the weld metal portion contains 0.01-0.1% of C, 0.1-0.7% of Si, 0.5-2.0% of Mn, 0.01-3.0% of Ni, 0.01-0.5% of Mo, 0.01-0.08% of Ti, P: 0.03% or less, S: 0.03% or less, O: 0.02-0.08%, Al: 0.001% -0.010%, and Mg: not more than 0.01%, wherein the Ti and O satisfy the relation of 0.3? Ti / O? 2.0 and the balance of Fe and other impurities. The method of claim 3, Wherein the composition of the weld metal portion satisfies the relationship of 0.01? (Nb + V) /Ti? 2.0. The method of claim 3, Wherein the composition of the weld metal portion satisfies the relationship of 0.1? Al / N? 0.5. The method of claim 3, Wherein the weld metal microstructure comprises at least 70% acicular ferrite and the remainder is at least one of intergranular ferrite, Widmasttaten ferrite and bainite. The method of claim 3, Wherein the weld metal portion contains TiO- (Ti, V) N complex acid and nitride having an average size of 0.80 占 퐉 or less and 0.25 to 0.35% of an area fraction of the flux cored arc weld metal portion.