JP2023086366A - Basic flux-cored wire, deposited metal obtained using basic flux-cored wire, welding method and manufacturing method for welded joint - Google Patents

Abstract

To provide a basic flux-cored wire with which whole posture welding can be performed, so that deposited metal and welded metal which are excellent in balance between strength and toughness can be obtained.SOLUTION: The basic flux-cored wire includes strong deoxidizing elements, where with respect to total mass of the wire, total amounts of the strong deoxidizing elements are 1.50 mass% or more and 4.00 mass% or less, REM is 0.030 mass% or more and 0.120 mass% or less, and B is 0.0200 mass% or less, and for instance, a value calculated by the following formula (1) for each content of REM, Fe, C, Si, Mn, P, S, Cr, Mo, Al, Zr, Ni and B in the flux-cored wire, satisfies 48.0 or less: the formula(1):32.1×[Si]-40.6×[Mn]-20.1×[Ni]-19.7×[Mo]-172.6×[C]-408.2×[REM]-5824.4×[B]-38.4×[Cr]-9960×[P]+43793×[S].SELECTED DRAWING: None

Description

The present invention provides a basic flux-cored wire that enables welding in all positions and has an excellent balance between strength and toughness, a weld metal obtained by using the basic flux-cored wire, and the basic flux-cored wire. The present invention relates to a welding method using a wire and a welded joint.

Flux-cored wires are classified into rutile, basic, and metal based on the type of flux used. Among them, the basic flux-cored wire has the advantage of being able to keep the amount of oxygen in the weld metal low, so that excellent toughness can be obtained. However, the basic flux-cored wire is inferior in welding workability, and has the disadvantage that it is difficult to apply it particularly to difficult-position welding such as vertical welding, horizontal welding, and upward welding.

Patent Literature 1 discloses a technique for overcoming the above-described drawbacks of basic flux-cored wires. Specifically, in Patent Document 1, the flux contains a strong deoxidizing metal element containing Mg and Al and a fluorine compound powder, and the strong deoxidizing metal powder and the fluorine compound powder related to the strong deoxidizing metal element are specified , the flux rate is 10 to 30% by mass, and Al: 1.0 to 3.5% by mass, Mg _(wire) : 0.3 to 0.9% by mass, fluorine conversion of fluorine compound Total of value F: 0.30 to 1.20% by mass, total of strong deoxidizing metal elements: 2.2% by mass or more, strong deoxidizing metal elements: 15 to 35% by mass, fluorine compound powder: 10 to 45% by mass It is described that all-position welding is possible by satisfying a specific composition such as.

Japanese Patent Application Laid-Open No. 2021-000646

By the way, the flux-cored wire described in Patent Document 1 is added with a strong deoxidizing element in order to enable all-position welding. The strong deoxidizing elements include those that exhibit excellent deoxidizing action during welding and slag out, and those that remain as inclusions in the weld metal.
However, inclusions remaining in the weld metal adversely affect mechanical performance, particularly toughness. In other words, Patent Document 1 overcomes the shortcomings of the basic flux-cored wire that enables all-position welding, but on the other hand, maximizes the advantage of the basic flux-cored wire, which has excellent toughness. It is no longer possible.

Further, although toughness depends on the value of strength, there is also the problem that the balance between strength and toughness varies depending on the target strength. For example, when the strength is designed to be high, the toughness is good, but when the target strength is lowered and the design is redesigned, the toughness may be extremely poor. This is because the elements to be added change depending on the target strength, which affects the deposited metal structure or the weld metal structure.

The present invention has been made in view of such problems, and provides a deposited metal and weld metal (hereinafter also referred to as "welded joint") that enables welding in all positions and has an excellent balance between strength and toughness. It is an object of the present invention to provide a basic flux-cored wire and a welding method capable of obtaining the following, and to provide a deposited metal and a welded joint having an excellent balance between strength and toughness.

The above object of the present invention is achieved by the following configuration [1] relating to a basic flux-cored wire.

[1] A basic flux-cored wire containing a strong deoxidizing element,
The total amount of the strong deoxidizing elements is 1.50% by mass or more and 4.00% by mass or less with respect to the total mass of the wire,
REM: 0.030% by mass or more and 0.120% by mass or less,
Fe: 85.0% by mass or more,
contains
C: 0.050% by mass or less,
Si: 0.60% by mass or less,
Mn: 2.00% by mass or less,
P: 0.0150% by mass or less,
S: 0.0150% by mass or less,
Cr: 1.00% by mass or less,
Mo: 1.00% by mass or less,
Al: 3.00% by mass or less,
Mg: 3.00% by mass or less,
Zr: 3.000% by mass or less,
Ti: 3.000% by mass or less,
Ca: 3.00% by mass or less,
Ni: 5.00% by mass or less,
B: 0.0200% by mass or less,
Ba: 4.00% by mass or less,
F: 2.00% by mass or less,
and
Value calculated by the following formula (1): 48.0 or less,
Value calculated by the following formula (2): 48.0 or less,
Value calculated by the following formula (3): 0.09 or more,
Value calculated by the following formula (4): 0.14 or more,
A basic flux-cored wire characterized by:
Formula (1):
32.1×[Si]−40.6×[Mn]−20.1×[Ni]−19.7×[Mo]−172.6×[C]−408.2×[REM]−5824. 4×[B]−38.4×[Cr]−9960×[P]+43793×[S]
Formula (2):
33.9×[Si]−47.0×[Mn]−22.2×[Ni]−11.9×[Mo]−203.9×[C]−443.5×[REM]−4482. 2×[B]−36.1×[Cr]−15281×[P]+47868×[S]
Formula (3):
0.001×[Fe]−0.71×[Si]+0.08×[Mn]−0.08×[Al]+0.69×[Zr]+0.03×[Ni]+0.01×[Mo ] + 0.32 x [C] + 2.27 x [REM] + 9.57 x [B] + 0.11 x [Cr]
Formula (4):
0.003×[Fe]−0.35×[Si]+0.09×[Mn]−0.13×[Al]+0.22×[Zr]+0.02×[Ni]−0.02×[ Mo]−0.11×[C]+1.17×[REM]+4.30×[B]+0.09×[Cr]
However, in the formulas (1) to (4), [REM], [Fe], [C], [Si], [Mn], [P], [S], [Cr], [Mo], [Al], [Zr], [Ni] and [B] are respectively the REM, the Fe, the C, the Si, the Mn, the P, the S, the Cr, the Mo, the Al, the It is a value in which the contents of Zr, Ni and B are represented by mass % with respect to the total mass of the wire.

Further, preferred embodiments of the present invention relating to a basic flux-cored wire relate to the following [2] to [11].

[2] For the total wire mass, further,
For the total wire mass, in addition,
Nb: 0.50% by mass or less,
Cu: 2.00% by mass or less,
W: 1.00% by mass or less,
Ta: 1.00% by mass or less,
V: 1.00% by mass or less,
Sr: 4.00% by mass or less, and
Total of alkali metal elements: 3.00% by mass or less,
containing at least one selected from
The basic flux-cored wire according to [1], wherein the balance is O, N and impurities.

[3] The basic content according to [1] or [2], wherein the content of B is 0.0020% by mass or more and 0.0150% by mass or less with respect to the total mass of the wire Flux-cored wire.

[4] The content of B includes the B conversion value of B oxide,
When the B conversion value of the B oxide with respect to the total mass of the wire is expressed as [B oxide] in mass%,
Formula (5): The basicity according to any one of [1] to [3], wherein the value calculated by [B oxide]/[B] is 0.5 or more Flux-cored wire.

[5] Ba: 4.00% by mass or less,
Ca: 3.00% by mass or less, and Sr: 4.00% by mass or less, containing at least one selected from
The flux contains at least one selected from BaF ₂ , CaF ₂ and SrF ₂ which are fluorides of Ba, Ca and Sr,
The Ba content includes the Ba conversion value of the _BaF2 ,
The Ca content includes the Ca conversion value of the _CaF2 ,
The Sr content includes the Sr conversion value of the _SrF2 ,
The basic flux-containing product according to any one of [1] to [4], wherein the F content includes the F conversion values of the BaF ₂ , the CaF ₂ and the SrF ₂ . wire.

[6] The basic flux-cored wire according to [5], wherein the content of F and the converted F value of all fluorides contained in the flux are equal.

[7] Any one of [1] to [6], wherein the content of oxides in the flux is 0.005% by mass or more and 0.100% by mass or less with respect to the total mass of the wire. or a basic flux-cored wire according to claim 1.

[8] The Cr content is 0.20% by mass or more and 0.90% by mass or less with respect to the total mass of the wire,
The Mo content is 0.50% by mass or less with respect to the total mass of the wire,
Formula (6): Any one of [1] to [7], wherein the value calculated by [Cr] / ([Cr] + [Mo]) is 0.20 or more A basic flux-cored wire as described.

[9] The Cr content is 0.90% by mass or less with respect to the total mass of the wire, and
The content of Mo is 0.10% by mass or more and 0.80% by mass or less with respect to the total mass of the wire,
Formula (7): Any one of [1] to [7], wherein the value calculated by [Mo] / ([Cr] + [Mo]) is 0.10 or more A basic flux-cored wire as described.

[10] As the strong deoxidizing element, 1.00% by mass or more and 2.50% by mass or less of Al is contained with respect to the total mass of the wire,
The Mg is 1.00% by mass or less,
When the content of Mg in the wire is expressed as [Mg] in mass% with respect to the total mass of the wire,
Formula (8): Any of [1] to [9], wherein the value calculated by [Al] / ([Al] + [Mg]) is 0.5 or more and 1.0 or less or a basic flux-cored wire according to claim 1.

[11] The basic flux-cored wire according to any one of [1] to [10], wherein the REM comprises La and Ce.

Further, the above object of the present invention relates to the following [12] relating to weld metal.
[12] With respect to the total mass of the weld metal,
C: 0.020% by mass or more and 0.100% by mass or less,
Si: 0.05% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.80% by mass or less,
Al: 0.30% by mass or more and 1.50% by mass or less,
Ce: 0.002% by mass or more and 0.010% by mass or less,
Fe: 85.0% by mass or more,
contains
La: 0.008% by mass or less,
P: 0.0200% by mass or less,
S: 0.0200% by mass or less,
Cr: 1.00% by mass or less,
Mo: 1.00% by mass or less,
Mg: 0.50% by mass or less,
Zr: 0.50% by mass or less,
Ti: 0.05% by mass or less,
Ca: 0.50% by mass or less,
Ni: 3.00% by mass or less,
B: 0.0090% by mass or less,
Ba: 1.00% by mass or less,
Nb: 0.001% by mass or less,
Cu: 0.1% by mass or less,
V: 0.001% by mass or less,
W: 0.1% by mass or less,
Ta: 0.1% by mass or less,
Sr: 1.00% by mass or less,
Total of alkali metal elements: 0.05% by mass or less,
O: 0.0250% by mass or less,
N: 0.0100% by mass or less, and
A weld metal characterized in that the balance is impurities.

The above object of the present invention also relates to the following [13] relating to a basic flux-cored wire.

[13] A basic flux-cored wire, characterized by obtaining the weld metal according to [12].

The above object of the present invention also relates to the following [14] relating to a welding method.

[14] A welding method comprising performing gas-shielded arc welding using the basic flux-cored wire according to any one of [1] to [11] and [13].

The above object of the present invention also relates to the following [15] relating to welded joints.

[15] A welded joint manufactured using the welding method according to [14].

INDUSTRIAL APPLICABILITY According to the present invention, a basic flux-cored wire, a welding method, and a balance between strength and toughness, which enable welding in all positions and can obtain a deposited metal and a weld metal having an excellent balance between strength and toughness. can provide excellent weld metal and welded joints.

In this embodiment, the basic flux-cored wire contains a strong deoxidizing element in an appropriate content, thereby improving welding workability and enabling welding in a difficult position. However, depending on the elements used for strength adjustment, there is a possibility that the strength and toughness of the deposited metal or weld metal cannot be balanced.

Therefore, the present inventors further derived a parameter formula from the relationship between the composition designed in the industrial strength range and the mechanical performance. Specifically, as the composition and mechanical performance of this embodiment, the relationship between strength, toughness, and brittle fracture surface ratio is summarized by a multiple regression equation, and by satisfying the four equations described below, excellent strength and toughness It was found that the composition of the wire with balance can be derived.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the embodiments described below, and can be arbitrarily modified without departing from the gist of the present invention.

[1. Basic flux-cored wire]
The basic flux-cored wire according to the present embodiment (hereinafter sometimes simply referred to as "wire") includes a flux as a core and a hoop as an outer skin. Preferred ranges and reasons for limiting the components contained in the basic flux-cored wire according to the present embodiment and their contents will be specifically described below.

In the specification, "-" is used to mean including the numerical values before and after it as lower and upper limits. Further, in this specification, an element with "(Wire)" immediately after it indicates that the element is contained in the wire.
Similarly, "(Metal)" immediately following an element indicates that the element is contained in the weld metal.

Here, an example of Mn is tentatively given as an element. The _metal Mn _(Wire) of the entire wire includes Mn contained in the hoop and Mn metal powder contained in the flux. Mn conversion value such as. In addition, the content of Mn _(Wire) is the total amount of the metal Mn _(Wire) of the entire wire and the Mn conversion value _(Wire) of the compound related to Mn, as the Mn content of the entire wire, with respect to the total mass of the wire It shall be expressed in % by mass. As for this total amount, either one of the metal Mn _(Wire) of the entire wire and the Mn conversion value _(Wire) of the Mn compound of the entire wire may be zero.

<Total amount of strong deoxidizing elements: 1.50% by mass or more and 4.00% by mass or less>
A basic flux-cored wire (hereinafter, sometimes simply referred to as "wire") according to the present embodiment includes a flux as a core and a hoop as an outer skin. In this embodiment, by adding an appropriate amount of a strong deoxidizing element, it is possible to improve the welding workability and to apply the difficult posture. Examples of strong deoxidizing elements include elements such as Al, Mg, Ti, Ca, and Zr, and the total amount is defined. Note that this total amount is mass % with respect to the total mass of the wire, for example, when the wire contains Al, Mg, Ti, Ca, and Zr, it is the total amount of these contents. If the total amount of the strong deoxidizing elements is less than 1.50% by mass, it will be difficult to apply to difficult postures. Therefore, the total amount of strong deoxidizing elements is 1.50% by mass or more, preferably 2.00% by mass or more.
On the other hand, if the total amount of strong deoxidizing elements exceeds 4.00% by mass, the number of inclusions in the weld metal excessively increases, resulting in a decrease in toughness. Therefore, the basic flux-cored wire according to the present embodiment has a composition range that satisfies the formulas (1) to (4) described later, and the total amount of the strong deoxidizing elements is 4.00% by mass or less. and preferably 3.20% by mass or less. As will be described later, it is preferable to contain Al and Mg as strong deoxidizing elements.

<REM _(Wire) : 0.030% by mass or more and 0.120% by mass or less>
REM (Rare Earth Metals) means a rare earth element, such as Ce and La. As described above, by including a strong deoxidizing element in the wire, it is possible to achieve welding with a difficult posture. Because the material remains, the toughness deteriorates. The present inventors found that toughness can be improved by reducing the number density of inclusions in the weld metal, based on the relationship between toughness and number density. Furthermore, the present inventors have found that the number density can be reduced by including REM _(Wire) in the wire within a predetermined content range.

Specifically, by including 0.030 or more of REM _(Wire) , REM acts as a binder that agglomerates the oxide of the added strong deoxidizing element. For example, when observing the structure in the weld metal created using a wire to which Al, Mg, and REM are added, a composite oxide of REM, Al, and Mg is generated, and the number density of inclusions in the weld metal decreases. It was confirmed that

If the content of REM _(Wire) is less than 0.030% by mass, the aggregating action of the oxide cannot be exhibited. Therefore, the REM _(Wire) content is 0.030% by mass or more, preferably 0.040% by mass or more, relative to the total mass of the wire.
On the other hand, when the content of REM _(Wire) exceeds 0.120% by mass, inclusions become coarse due to agglomeration, which may adversely affect mechanical performance or cause unacceptable welding defects. be. Therefore, the REM _(Wire) content is 0.120% by mass or less, preferably 0.110% by mass or less, relative to the total mass of the wire.

In addition, REM is preferably contained in the flux. The form of addition is not particularly limited, and may be in any form such as the form of metal REM, the form of an alloy containing REM, or the form of a compound of REM. Here, when REM is contained in the flux in the form of a compound of REM, the content of REM _(Wire) includes the REM conversion value of the compound related to REM. Preferably, the REM is contained in the flux in the form of an REM-containing alloy, and more preferably, all of the REM added to the wire is contained in the flux in the form of an REM-containing alloy. The REM contained in the basic flux-cored wire according to the present embodiment is preferably La and Ce.

In this embodiment, in order to achieve the object of the present invention, a plurality of parameters are generated using specific element contents and the values of these parameters are defined. In this specification, the content of a certain component with respect to the total mass of the wire is expressed as [(component name)]. Specifically, [REM], [Fe], [C], [Si], [Mn], [P], [S], [Cr], [Mo], [Al], [Zr], [ Ni], [B], and [Mg] are respectively REM _(Wire) , Fe _(Wire) , C _(Wire) , Si ( _Wire) , Mn _(Wire) , P _(Wire) , S _(Wire) , Cr _(Wire) , Mo _(Wire) , Al _(Wire) , Zr _(Wire) , Ni _(Wire) , B _(Wire) , and Mg _(Wire) content in % by mass with respect to the total mass of the wire is a value expressed in .

<Value calculated by the following formula (1): 48.0 or less>
Formula (1) is used to adjust mechanical performance such as strength and toughness, and the relationship between elements related to carbon equivalent and cold cracking susceptibility and the brittle fracture surface rate at -46 ° C is parameterized by multiple regression analysis. is the formula If the value calculated by the following formula (1) based on the content of each element is 48.0 or less, the wire composition is a combination of elements with a low brittle fracture surface rate at cryogenic temperatures. It can be said that the toughness of the On the other hand, if the value calculated by the following formula (1) exceeds 48.0, the brittle fracture surface rate is high, sufficient toughness cannot be secured, and an element that may cause variations in toughness depending on the weld site The wire composition is a combination of Therefore, the value calculated by the following formula (1) is preferably 48.0 or less, more preferably 47.0 or less.

Formula (1):
32.1×[Si]−40.6×[Mn]−20.1×[Ni]−19.7×[Mo]−172.6×[C]−408.2×[REM]−5824. 4×[B]−38.4×[Cr]−9960×[P]+43793×[S]

<Value calculated by the following formula (2): 48.0 or less>
Formula (2) is used to adjust mechanical performance such as strength and toughness, and the relationship between elements related to carbon equivalent and cold cracking susceptibility and the brittle fracture surface rate at -20 ° C is parameterized by multiple regression analysis. is the formula Based on the content of each element, if the value calculated by the following formula (2) is 48.0 or less, the wire composition will be a combination of elements with a high brittle fracture surface rate at low temperatures. can be said to be excellent. On the other hand, if the value calculated by the following formula (2) exceeds 48.0, the brittle fracture surface rate is high, sufficient toughness cannot be secured, and an element that may cause variations in toughness depending on the weld site The wire composition is a combination of Therefore, the value calculated by the following formula (2) is preferably 48.0 or less, more preferably 40.0 or less.

Formula (2):
33.9×[Si]−47.0×[Mn]−22.2×[Ni]−11.9×[Mo]−203.9×[C]−443.5×[REM]−4482. 2×[B]−36.1×[Cr]−15281×[P]+47868×[S]

<Value calculated by the following formula (3): 0.09 or more>
Formula (3) is used to adjust mechanical performance such as strength and toughness, and elements related to carbon equivalent and cold cracking susceptibility and "balance between strength and toughness at -46 ° C" (CVN (-46 ° C )/TS parameter) is parameterized by multiple regression analysis. Here, CVN refers to Charpy absorbed energy (J) and TS refers to tensile strength (MPa). If the value calculated by the following formula (3) based on the content of each element is 0.09 or more, the wire composition will have a combination of elements that provide a good balance between strength and toughness. On the other hand, when the value calculated by the following formula (3) is less than 0.09, the wire composition has a combination of elements having poor balance between strength and toughness. Therefore, the value calculated by the following formula (3) is preferably 0.09 or more, more preferably 0.10 or more.

Formula (3):
0.001×[Fe]−0.71×[Si]+0.08×[Mn]−0.08×[Al]+0.69×[Zr]+0.03×[Ni]+0.01×[Mo ] + 0.32 x [C] + 2.27 x [REM] + 9.57 x [B] + 0.11 x [Cr]

<Value calculated by the following formula (4): 0.14 or more>
Formula (4) is used to adjust mechanical performance such as strength and toughness, and elements related to carbon equivalent and cold cracking susceptibility and "balance between strength and toughness at -20 ° C." (CVN (-20 ° C. )/TS parameter) is parameterized by multiple regression analysis. Here, CVN refers to Charpy absorbed energy (J), and TS refers to tensile strength (MPa). If the value calculated by the following formula (4) based on the content of each element is 0.14 or more, the wire composition will have a combination of elements that provide a good balance between strength and toughness. On the other hand, if the value calculated by the following formula (4) is less than 0.14, the wire composition will be a combination of elements with poor balance between strength and toughness.

Formula (4):
0.003×[Fe]−0.35×[Si]+0.09×[Mn]−0.13×[Al]+0.22×[Zr]+0.02×[Ni]−0.02×[ Mo]−0.11×[C]+1.17×[REM]+4.30×[B]+0.09×[Cr]

Next, individual elements contained for the purpose of improving workability, adjusting mechanical performance, etc. will be described. If the elements described below satisfy the above formulas (1) to (4), it is possible to obtain a good balance between strength and toughness. If too much is added, there is a risk of weld cracking, etc., so the upper limit of each element is determined. It should be noted that the purpose is to improve workability, adjust mechanical performance, etc., and it may be contained as necessary.

<Fe _(Wire) : 85.0% by mass or more>
Fe is the main element among the elements contained in order to satisfy the required mechanical performance in commonly used steel types such as mild steel, high-tensile steel, low-temperature steel, and the like. If the Fe _(Wire) content is less than 85% by mass, the influence of the remaining elements increases, possibly deteriorating the mechanical performance. Therefore, the content of Fe _(Wire) is 85% by mass or more, preferably 87.0% by mass or more, relative to the total mass of the wire. The Fe source in the wire includes metal powder of Fe added to the flux, metal powder of an alloy related to Fe, a compound related to Fe, Fe contained in the hoop, and the like. When Fe is contained in the flux, it is preferable to contain Fe in the form of metal powder of Fe or metal powder of an alloy related to Fe from the viewpoint of improving the deposition amount.

<C _(Wire) : 0.050% by mass or less>
C is a component that affects the strength of the deposited metal and weld metal, and the strength increases as the C content in the deposited metal or weld metal increases. In order to satisfy the required strength range in generally used steel types such as mild steel, high-tensile steel, low-temperature steel, etc., it is preferable to include C in the wire. However, when the content of C _(Wire) increases, carbides tend to precipitate in the deposited metal or weld metal, resulting in a decrease in toughness relative to the target strength, resulting in a loss of balance between strength and toughness. There is a risk. Therefore, the content of C _(Wire) is 0.050% by mass or less, preferably 0.040% by mass or less, relative to the total mass of the wire.
On the other hand, in order to adjust the strength, the content of C _(Wire) is preferably 0.001% by mass or more with respect to the total mass of the wire. The C source in the wire includes graphite and carbide added to the flux, and C contained in the hoop. However, from the viewpoint of suppressing carbides, it is preferable that the content of C _(Wire) is as low as possible, and it is more preferable that the flux does not contain C.

<Si _(Wire) : 0.60% by mass or less>
Si is a component that affects the strength and toughness of the weld metal. It is preferable to include Si in the wire in order to satisfy the mechanical performance required for generally used steel grades such as mild steel, high-tensile steel, low-temperature steel, and the like. Si has a deoxidizing effect, and excessive Si content in the wire increases the number of inclusions, possibly resulting in an imbalance between strength and toughness. Therefore, the content of Si _(Wire) is 0.60% by mass or less, preferably 0.50% by mass or less, relative to the total mass of the wire.
On the other hand, in order to adjust the strength, the content of Si _(Wire) is preferably 0.01% by mass or more with respect to the total mass of the wire. Examples of the Si source in the wire include metal powder of Si added to the flux, metal powder of an alloy related to Si, a compound related to Si, and Si contained in the hoop. When Si is contained in the flux for the purpose of suppressing inclusions, it is preferably contained in the form of metal powder of Si or metal powder of an alloy related to Si.

<B _(Wire) : 0.0200% by mass or less>
B is an element that increases the crack resistance while preventing the toughness of the deposited metal and weld metal from deteriorating. Therefore, the content of B _(Wire) is 0.0200% by mass or less, preferably 0.0150% by mass or less, relative to the total mass of the wire. Moreover, it was confirmed that the brittle fracture rate was lowered by adding B to the wire according to the present embodiment. This is because the inclusion of B in the wire suppresses coarse ferrite phases or bainite phases that are generated at grain boundaries. Therefore, from the viewpoint of reducing the brittle fracture rate, the content of B _(Wire) is preferably 0.0020% by mass or more with respect to the total mass of the wire. In addition, since the balance between strength and toughness changes depending on the content of Zr _(Wire) and the content of B ( _{Wire )} , the preferred range of the content of B _(Wire) changes depending on the content of Zr (Wire). do. That is, if the content of Zr _(Wire) is 0.045% by mass or less, as described above, the content of B _(Wire) is preferably 0.0150% by mass or less, but Zr _(Wire) exceeds 0.045% by mass, the content of B _(Wire) is more preferably 0.0045% by mass or less.
Examples of the B source in the wire include B metal powder added to the flux, metal powder of an alloy of B, a compound of B, and B contained in the hoop.

In addition, when B is contained in the flux in the form of an oxide, the oxide of B is easily mixed uniformly in the flux, which is significant from the viewpoint of production. Therefore, it is preferable to contain B in the form of an oxide instead of the form of metal powder in the flux. In this case, the content of B _(Wire) includes the B conversion value of B oxide, and the value calculated by the following formula (5) is preferably 0.5 or more, and 0.7 or more. 1.0 is more preferable. When the value calculated by the following formula (5) is 1.0, it means that the content of B _(Wire) is all the B-converted value of the B oxide. In other words, when B is contained in the wire, it is preferable to contain B in the flux in the form of an oxide of B.

Formula (5): [B oxide]/[B]
In the above formula (5), [B oxide] represents the B-converted value _(Wire) of the B oxide relative to the total mass of the wire expressed in mass % relative to the total mass of the wire.

<Mn _(Wire) : 2.00% by mass or less>
Mn, like Si, is a component that affects the strength and toughness of the weld metal. It is preferable to incorporate Mn into the wire in order to satisfy the required mechanical performance in commonly used steel grades such as mild steel, high-tensile steel, low-temperature steel, and the like. Mn has a deoxidizing effect, and excessive Mn content in the wire increases the number of inclusions, possibly resulting in an imbalance between strength and toughness. Therefore, the content of Mn _(Wire) is 2.00% by mass or less, preferably 1.80% by mass or less, relative to the total mass of the wire.
On the other hand, in order to adjust the strength, the content of Mn _(Wire) is preferably 0.01% by mass or more with respect to the total mass of the wire. The Mn source in the wire includes metal powder of Mn added to the flux, metal powder of an alloy related to Mn, a compound related to Mn, Mn contained in the hoop, and the like. When Mn is contained in the flux for the purpose of suppressing inclusions, it is preferably contained in the flux in the form of metal powder of Mn or metal powder of an alloy related to Mn.

<P _(Wire) : 0.0150% by mass or less>
P is an element that lowers crack resistance and mechanical properties of the weld metal. Therefore, the content of P _(Wire) is suppressed to 0.0150% by mass or less, preferably 0.0100% by mass or less, with respect to the total mass of the wire. Incidentally, it is preferable not to forcibly add P into the wire.

<S _(Wire) : 0.0150% by mass or less>
S is an element that reduces crack resistance. Therefore, the content of S _(Wire) is 0.0150% by mass or less, preferably 0.010% by mass or less, relative to the total mass of the wire.
On the other hand, S _(Wire) has the effect of reducing the viscosity and surface tension of the droplets when the wire is melted, smoothing the transfer of the droplets, reducing the size of the spatter, and improving the welding workability. . Therefore, from the viewpoint of welding workability, the content of S _(Wire) is preferably 0.0005% by mass or more with respect to the total mass of the wire. The S source in the wire is not particularly limited, and it may be contained in the flux in the form of powder of S alone or a compound of S, or may be contained in the hoop. It is more preferable not to add it.

<Cr _(Wire) : 1.00% by mass or less>
Cr is a component that affects the strength and toughness of the deposited metal and weld metal. Cr is preferably contained in the wire in order to satisfy the required mechanical performance of generally used steel grades such as mild steel, high-tensile steel, low-temperature steel, and the like. If Cr is excessively contained in the wire, it tends to be precipitated as carbides at grain boundaries, possibly resulting in loss of balance between strength and toughness. Therefore, the content of Cr _(Wire) is 1.00% by mass or less, preferably 0.90% by mass or less, relative to the total mass of the wire.
On the other hand, in order to adjust the strength, the content of Cr _(Wire) is preferably 0.20% by mass or more with respect to the total mass of the wire. Examples of the Cr source in the wire include metal powder of Cr added to the flux, metal powder of an alloy containing Cr, a compound containing Cr, and Cr contained in the hoop. When Cr is contained in the flux, it is preferably contained in the flux in the form of metal powder of Cr or metal powder of an alloy related to Cr.

<Mo _(Wire) : 1.00% by mass or less>
Mo is a component that improves high-temperature strength. Mo is preferably contained in the wire in order to satisfy the required mechanical performance in commonly used steel grades such as mild steel, high-tensile steel, low-temperature steel, and the like. If Mo is excessively contained in the wire, the strength of the wire may be excessively increased, resulting in an imbalance between strength and toughness. Therefore, the content of Mo _(Wire) is 1.00% by mass or less, preferably 0.90% by mass or less, relative to the total mass of the wire.
On the other hand, in order to adjust the strength, the content of Mo _(Wire) is preferably 0.10% by mass or more with respect to the total mass of the wire. The Mo source in the wire includes Mo metal powder added to the flux, Mo alloy metal powder, Mo compounds, Mo contained in the hoop, and the like. When Mo is contained in the flux, it is preferably contained in the flux in the form of Mo metal powder or Mo alloy metal powder.

In addition, the combination of Cr, which contributes to strength and toughness, and Mo, which is generally used as an element that improves high-temperature strength, has a content of is preferably determined.

(design to improve toughness)
For example, when it is desired to further improve toughness, it is preferable to make the content of Cr, which contributes to strength and toughness, higher than the content of Mo. That is, the content of Cr _(Wire) is set to 0.20% by mass or more and 0.90% by mass or less with respect to the total mass of the wire, and the content of Mo _(Wire) is set to It is 0.50% by mass or less, and the value calculated by the following formula (6) is preferably 0.20 or more, more preferably 0.50 or more, and further preferably 0.75 or more. It is preferred and most preferred to be 1.00.

Formula (6): [Cr]/([Cr]+[Mo])

(Designed to improve high temperature strength)
On the other hand, when it is desired to be used for heat-resistant steel, it is preferable that the content of Mo, which is generally used as an element for improving high-temperature strength, is higher than the content of Cr, that is, the content of Cr _(Wire) is The content of Mo _(Wire) is 0.10% by mass or more and 0.80% by mass or less with respect to the total mass of the wire, and the following formula ( The value calculated by 7) is preferably 0.10 or more, more preferably 0.45 or more, further preferably 0.70 or more, and most preferably 1.00. .

Formula (7): [Mo] / ([Cr] + [Mo])

<Al _(Wire) : 3.00% by mass or less>
Al is a strong deoxidizing component, and by causing an oxidation reaction in the weld metal, it forms an oxide (hereinafter also referred to as "slag") on the molten pool, which is difficult to weld such as vertical welding or upward welding. It is possible to improve bead shape and burn-through resistance in welding in all positions including positions. Excessive Al content in the wire increases inclusions remaining in the weld metal, adversely affecting toughness. Therefore, the content of Al _(Wire) is 3.00% by mass or less, preferably 2.50% by mass or less, and more preferably 1.70% by mass or less with respect to the total mass of the wire. .
On the other hand, the content of Al _(Wire) is preferably 0.50% by mass or more, more preferably 1.00% by mass or more, relative to the total mass of the wire. The Al source in the wire includes Al metal powder added to the flux, Al alloy metal powder, Al compounds, Al contained in the hoop, and the like. When Al is contained in the flux for the purpose of further reducing the amount of oxygen in the weld metal, it is preferably contained in the flux in the form of Al metal powder or Al alloy metal powder.

<Mg _(Wire) : 3.00% by mass or less>
Like Al, Mg is a strong deoxidizing component, and by causing an oxidation reaction in the weld metal, slag is formed on the molten pool, and welding in all positions including difficult positions such as vertical welding and upward welding is possible. In, it becomes possible to improve burn-through resistance. Excessive Mg content in the wire increases inclusions remaining in the weld metal, adversely affecting toughness. Therefore, the content of Mg _(Wire) is 3.0% by mass or less, preferably 1.50% by mass or less, more preferably 1.00% by mass or less, relative to the total mass of the wire. .
On the other hand, the content of Mg _(Wire) is preferably 0.30% by mass or more, more preferably 0.50% by mass or more, relative to the total mass of the wire. Examples of the Mg source in the wire include metal powder of Mg added to the flux, metal powder of an alloy containing Mg, a compound containing Mg, and Mg contained in the hoop. When Mg is included in the flux for the purpose of further reducing the oxygen content in the weld metal, it is preferable to include it in the flux in the form of metal powder of Mg or metal powder of an alloy related to Mg.

<Zr _(Wire) : 3.000% by mass or less>
Like Al, Zr is a strong deoxidizing component, and by causing an oxidation reaction in the weld metal, slag is formed on the molten pool, and welding in all positions including difficult positions such as vertical welding and upward welding is possible. In, it becomes possible to improve burn-through resistance. Excessive Zr content in the wire increases inclusions remaining in the weld metal, adversely affecting toughness. Therefore, the content of Zr _{(Wire) is} 3.000% by mass or less, preferably 0.500% by mass or less, with respect to the total mass of the wire. It is more preferable to make it 0.045% by mass or less.
On the other hand, there is no particular meaning in defining the lower limit of Zr _(Wire) . Moreover, when the wire mainly contains Mg and Al as strong deoxidizing elements, the content of Zr _(Wire) is preferably zero. Zr sources in the wire include metal powder of Zr added to the flux, metal powder of alloys related to Zr, compounds related to Zr, and Ti contained in the hoop. When Zr is contained in the flux for the purpose of further reducing the amount of oxygen in the weld metal, it is preferably contained in the flux in the form of Zr metal powder or Zr alloy metal powder.

<Ti _(Wire) : 3.000% by mass or less>
Like Al, Ti is a strong deoxidizing component, and by causing an oxidation reaction in the weld metal, forms an oxide (slag) on the molten pool, including difficult positions such as vertical welding and upward welding. It is possible to improve burn-through resistance in welding in all positions. Excessive Ti content in the wire increases inclusions remaining in the weld metal, adversely affecting toughness. Therefore, the content of Ti _(Wire) is 3.000% by mass or less, preferably 0.500% by mass or less, more preferably 0.010% by mass or less, relative to the total mass of the wire. .
On the other hand, Ti is less effective as a deoxidizing component than Mg and Al, and may form precipitates such as TiC that deteriorate toughness. Therefore, there is no particular meaning in defining the lower limit of Ti _(Wire) , and it is preferable to set the content of Ti _(Wire) to zero when mainly containing Mg and Al in the wire. The Ti source in the wire includes metal powder of Ti added to the flux, metal powder of an alloy related to Ti, a compound related to Ti, Ti contained in the hoop, and the like. For the purpose of further reducing the amount of oxygen in the weld metal, when Ti is included in the flux, it is preferable to include it in the flux in the form of metal powder of Ti or metal powder of an alloy related to Ti.

<Ca _(Wire) : 3.00% by mass or less>
Like Al, Ca is a strong deoxidizing component, and by causing an oxidation reaction in the weld metal, it forms an oxide (slag) on the molten pool, including difficult positions such as vertical welding and upward welding. It is possible to improve burn-through resistance in welding in all positions. However, excessive Ca content in the wire increases inclusions remaining in the weld metal, adversely affecting toughness. Therefore, the content of Ca _(Wire) is 3.0% by mass or less, preferably 1.00% by mass or less, more preferably 0.30% by mass or less, relative to the total mass of the wire. .
On the other hand, Ca contributes to deoxidizing the weld metal and improving welding workability by being contained in the flux as CaF ₂ which is a fluoride. The content of Ca _(Wire) includes the Ca conversion value of CaF ₂ in the flux, but the fluoride in the flux is not limited to CaF ₂ , and fluorides such as BaF ₂ and SrF ₂ are used. Therefore, there is no need to set a lower limit for the Ca content. Moreover, when Mg and Al are mainly added to the wire as strong deoxidizing components, it is preferable to set the content of Ca _(Wire) to 0% by mass.

The Ca source in the wire includes Ca metal powder added to the flux, Ca alloy metal powder, Ca compounds, Ca contained in the hoop, and the like. In this embodiment, when Ca is contained in the wire, if this Ca is contained in the flux, the amount of oxygen in the weld metal can be further reduced. Therefore, all Ca contained in the wire is preferably contained in the flux in the form of fluoride powder, that is, in the form of _CaF2 .

There are various elements called strong deoxidizing elements other than Al, Mg, Zr, Ti, and Ca listed above. It is preferable to use the above five elements, which are generally contained in the wire in the form of metal powder, as strong deoxidizing elements.
Among the above five elements, Al and Mg in particular tend to agglomerate slag and form slag early and over the entire surface of the molten pool. It is a useful element for realizing welding of On the other hand, with Zr, Ti and Ca, slag tends to disperse, and slag formation tends to concentrate toward the edges due to the flow of the molten pool.

Therefore, it is preferable that the wire contains at least one strong deoxidizing element selected from Al, Mg, Ti, Ca and Zr. The content of each element is 1.00% by mass to 2.50% by mass for Al _(Wire) , 0.30% by mass to 0.50% by mass for Mg _(Wire) , and 0.50% by mass for Ti _(Wire). 0.10 mass% or less (including 0 mass%), Zr _(Wire) 0.20 mass% or less (including 0 mass%), Ca _(Wire) 0.10 mass% or less (including 0 mass% ), and the total amount of the strong deoxidizing elements contained in the wire is 1.50% by mass or more and 4.00% by mass or less.

Furthermore, in the present embodiment, it is more preferable to contain at least one of Al and Mg, and it is even more preferable to contain at least Al. In this case, Al _(Wire) is contained in an amount of 1.00% by mass or more and 2.50% by mass or less with respect to the total mass of the wire, and Mg _(Wire) is 1.00% by mass or less, and the following formula (8 ) is preferably 0.5 or more and 1.0 or less.

Formula (8): [Al] / ([Al] + [Mg])

<Ni _(Wire) : 5.00% by mass or less>
Ni is a component that stabilizes the austenite structure of the weld metal and improves the toughness at low temperatures, and is also a component that can adjust the amount of crystallization of the ferrite composition. Ni is preferably contained in the wire in order to satisfy the required mechanical performance in commonly used steel grades such as mild steel, high-tensile steel, low-temperature steel, and the like. If the Ni content in the wire is excessive, the strength of the wire may be excessively increased, resulting in an imbalance between strength and toughness. Therefore, the content of Ni _(Wire) is 5.0% by mass or less, preferably 3.0% by mass or less, relative to the total mass of the wire.
On the other hand, when it is used for welding low-temperature steel or the like, the content of Ni _(Wire) is preferably 0.20% by mass or more with respect to the total mass of the wire. Examples of the Ni source in the wire include Ni metal powder added to the flux, metal powder of an alloy related to Ni, a compound related to Ni, and Ni contained in the hoop. When Ni is contained in the flux for the purpose of further reducing the amount of oxygen in the weld metal, it is preferably contained in the flux in the form of Ni metal powder or Ni-related alloy metal powder.

<Ba _(Wire) : 4.00 mass% or less>
Ba is mainly contained in the flux in the form of _BaF2 , which is a fluoride, and contributes to deoxidizing the weld metal and improving welding workability. Fluorides are generally added as fluxes for basic flux-cored wires, and among various fluorides, BaF ₂ is frequently used. However, excessive Ba content in the wire may cause arc deflection and deteriorate welding workability. Therefore, the content of Ba _(Wire) is 4.00% by mass or less, preferably 3.00% by mass or less.

The content of Ba _(Wire) includes the Ba conversion value of BaF ₂ in the flux, but the fluoride in the flux is not limited to BaF ₂ , for example, fluorides such as CaF ₂ and SrF ₂ can be used, there is no need to set a lower limit for the Ba content. However, when the flux contains a Ba compound such as BaF ₂ or BaCO ₃ , the content of Ba _(Wire) with respect to the total mass of the wire is preferably 1.75% by mass or more. Examples of the Ba source in the wire include metal powder of Ba added to the flux, metal powder of an alloy containing Ba, a compound containing Ba, and Ba contained in the hoop. In this embodiment, when Ba is contained in the wire, it is preferable that all Ba is contained in the flux in the form of _BaF2 , which is a fluoride.

<F _(Wire) : 2.00% by mass or less>
F _(Wire) is mainly derived from fluoride. It is contained in the flux of the flux-cored wire in the form of fluorides such as Ca, Ba or Sr mentioned above. Fluorides are commonly added to basic flux-cored wires and contribute to improvement of welding workability. However, if the content of F _(Wire) exceeds 2.00% by mass with respect to the total mass of the wire, excessive vaporization of F occurs inside the wire, increasing the amount of spatter generation, etc., resulting in poor welding workability. may worsen. Therefore, the content of Ba _(Wire) is 2.00% by mass or less, preferably 1.00% by mass or less, more preferably 0.80% by mass or less, relative to the total mass of the wire. .

On the other hand, when F is contained in the wire for the purpose of improving welding workability, the content of F _(Wire) is preferably 0.40% by mass or more with respect to the total mass of the wire. The F source in the wire is preferably all fluoride-derived, and examples thereof include BaF ₂ , SrF ₂ , Na ₃ AlF ₆ , NaF, CaF ₂ , AlF ₃ , MgF ₂ and the like. 1 type, or 2 or more types may be included. Among these fluorides, at least one fluoride selected from the group consisting of BaF ₂ , SrF ₂ and CaF ₂ is contained in the wire so as to have the content described in the section of Ba, Sr and Ca above. from the viewpoint of welding workability. In addition, Ba has a _low work function, has the effect of further stabilizing the cathode spot, and contributes to the improvement of welding workability. It is more preferable to contain in In the present embodiment, all Ba _(Wire) sources are preferably BaF ₂ , and the content of F _(Wire) excluding the F conversion value of BaF ₂ among the above F _(Wire) contents The balance of the quantity is preferably sourced from _CaF2 .

In addition to or in place of the above elements, the following elements may be used in commonly used steel grades such as mild steel, high-strength steel, low-temperature steel, etc., within the scope of general technology. It may optionally be added for the purpose of adjusting mechanical performance, improving welding workability, and the like. The following Nb, Cu, W, Ta, V, Sr, and alkali elements are not added in the present embodiment, and their addition is not particularly necessary. is preferably added in the optimum range described below.

<Nb _(Wire) : 0.50% by mass or less>
Nb is a component that affects mechanical performance such as strength. Nb may be contained in the wire in order to satisfy the required mechanical performance in commonly used steel grades such as mild steel, high-tensile steel, low-temperature steel, and the like. In this case, the content of Nb _(Wire) is preferably 0.50% by mass or less, more preferably 0.30% by mass or less, relative to the total mass of the wire. The Nb source in the wire includes metal powder of Nb added to the flux, metal powder of an alloy related to Nb, a compound related to Nb, and Nb contained in the hoop.

<Cu _(Wire) : 2.0% by mass or less>
Cu is an element that contributes to improving the strength and weather resistance of the weld metal. Cu may be contained in the wire in order to satisfy the required strength and weather resistance in commonly used steel grades such as mild steel, high-tensile steel, low-temperature steel, and the like. In this case, the content of Cu _(Wire) is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, relative to the total mass of the wire.
On the other hand, when Cu is contained in the wire for the purpose of ensuring the strength and weather resistance of the weld metal, the content of Cu _(Wire) is 0.01% by mass or more with respect to the total mass of the wire. Preferably. The Cu source in the wire includes the Cu metal powder added to the flux, the metal powder of the alloy related to Cu, the compound related to Cu, the Cu contained in the hoop, and the Cu plating on the wire surface. Also includes

<W _(Wire) : 1.00% by mass or less>
W is a component that improves high-temperature strength and pitting corrosion resistance. W may be contained in the wire in order to satisfy the required mechanical performance in commonly used steel grades such as mild steel, high-strength steel, low-temperature steel, and the like. In this case, the content of W _(Wire) is preferably 1.00% by mass or less, more preferably 0.5% by mass or less, relative to the total mass of the wire. Examples of the W source in the wire include W metal powder added to the flux, metal powder of an alloy of W, a compound of W, and W contained in the hoop.

<Ta _(Wire) : 1.00% by mass or less>
Ta is an element that affects mechanical performance such as strength. In order to satisfy the required mechanical performance, Ta may be contained in the wires of commonly used steel types such as mild steel, high-tensile steel, low-temperature steel, and the like. In this case, the Ta _(Wire) content is preferably 1.00% by mass or less, more preferably 0.50% by mass or less, relative to the total mass of the wire. The Ta source in the wire includes Ta metal powder added to the flux, Ta alloy metal powder, Ta compounds, Ta contained in the hoop, and the like.

<V _(Wire) : 1.00% by mass or less>
V is an element that reduces the toughness and cracking resistance of the weld metal while exerting the effect of improving the strength of the weld metal. Therefore, the content of V _(Wire) in the wire is preferably 1.00% by mass or less, more preferably 0.50% by mass or less, relative to the total mass of the wire. Examples of the V source in the wire include metal powder of V added to the flux, metal powder of an alloy related to V, a compound related to V, and V contained in the hoop.

<Sr _(Wire) : 4.00 mass% or less>
Sr contributes to deoxidizing the weld metal and improving welding workability by being contained in the flux mainly as _SrF2 , which is a fluoride. However, if the Sr content in the wire is 4.00% by mass or less, arc deflection can be suppressed and good welding workability can be obtained. Therefore, the Sr _(Wire) content is preferably 4.00% by mass or less, more preferably 3.00% by mass or less, relative to the total mass of the wire.
The Sr _(Wire) content includes the Sr-equivalent value of SrF ₂ in the flux, but the fluoride in the flux is not limited to SrF ₂ , and includes fluorides such as CaF ₂ and BaF ₂ . can be used, there is no need to provide a lower limit for the Sr content. However, when an Sr compound such as SrF ₂ or SrCO ₃ is included in the flux, the content of Sr _(Wire) with respect to the total mass of the wire is preferably 0.05% by mass or more. Examples of the Sr source in the wire include Sr metal powder added to the flux, metal powder of an alloy related to Sr, a compound related to Sr, and Sr contained in the hoop. In the present embodiment, when Sr is contained in the wire, all Sr is preferably contained in the flux in the form of _SrF2 , which is a fluoride.

As described above, in the basic flux-cored wire according to the present embodiment, the flux contains at least one selected from BaF ₂ , CaF ₂ and SrF ₂ which are fluorides of Ba, Ca and Sr. preferably. In this case, the Ba content includes the Ba conversion value of _BaF2 , the Ca content includes the Ca conversion value of _CaF2 , the Sr content includes the Sr conversion value of _SrF2 , and the F shall include the F conversion values of BaF ₂ , CaF ₂ and SrF ₂ . In addition, it is preferable that all the F sources in the wire are derived from fluoride, that is, the content of F contained in the wire is equal to the F conversion value of the total fluoride contained in the flux.

<Total of alkali metals: 3.00% by mass or less>
Alkali metal elements act as arc stabilizers. Alkali metals in this embodiment are based on metal powders and compounds containing one or more alkali metal elements. In addition, K, Li, Na etc. are mentioned as an alkali-metal element. The total content of alkali metals in the wire represents the total content of alkali metals in the wire converted from the metal powder and compound composed of alkali metal elements. That is, it is the total amount of K _(Wire) , Li _(Wire) , Na _(Wire), and the like. The total amount of alkali metals in the wire is preferably 3.00% by mass or less, preferably 2.00% by mass, with respect to the total mass of the wire, from the viewpoint that it is easy to adjust the molten physical properties preferable for improving the bead shape. The following are more preferable.

(Oxide in wire: 0.005% by mass or more and 0.100% by mass or less)
Oxides form the basis of coarse inclusions and affect toughness, so it is preferable to avoid adding them to the flux in the form of oxides as much as possible. Therefore, the total amount of oxides of each element added to the flux is more preferably suppressed to 0.100% by mass or less with respect to the total mass of the wire. From the viewpoint of production, B and REM are preferably added in the form of oxides, and more preferably 0.005% by mass or more of the oxides.

(Remainder: O, N and inevitable impurities)
In the present embodiment, the remainder excluding the above elements is preferably O, N and unavoidable impurities, and the total amount of the remainder is preferably 0.50% by mass or less. Impurities mean those that are not intentionally added, and examples of elements other than the above include Sn, Co, Sb, As, and the like. The total content of impurities in the wire is preferably 0.45% by mass or less, more preferably 0.30% by mass or less.
The balance also includes O and N when the above elements are contained in the flux in the form of oxides or nitrides or dissolved in the hoop. In the flux-cored wire, O and N cannot be analyzed clearly, so the remainder was used, but in this embodiment, the total wire mass It can be estimated that the total amount of O and N is 0.05% by mass or less. It should be noted that, from the viewpoint of mechanical performance, it is technically unacceptable that O and N exceed 0.05% by mass in the basic flack-cored wire.

〔hoop〕
The flux-cored wire according to the present embodiment has a hoop filled with flux, and the hoop is preferably made of a cold-rolled steel strip from the viewpoint of availability and economy. As the cold-rolled steel strip, it is preferable to use, for example, steel strips with symbols SPCC, SPCD, SPCE, SPCF, SPCG, etc. described in JIS G 3141:2017.

A basic flux-cored wire according to another embodiment of the present invention is a wire for obtaining a deposited metal described below. Since the deposited metal represents the metal transferred from the filler material to the welded part, the composition of the deposited metal obtained under the generally used welding conditions is stipulated, so it is possible to limit the wire. can. Welding conditions generally used can be, for example, welding conditions conforming to the method for producing deposited metal described in JIS Z3184. For example, a welding current of 200 to 220 A, a welding voltage of 0 to 23 V, a shielding gas of 100% CO ₂ gas, and a welding heat input of 0.8 to 1.1 kJ/mm can be used.

[2. Weld metal]
As described above, the basic flux-cored wire according to the present embodiment contains a strong deoxidizing element and REM, thereby enabling welding in a difficult position and achieving a good balance between strength and toughness. be able to. Similarly, in the weld metal according to the present embodiment, the content of B _(Metal) and the content of La _(Metal) and Ce _(Metal) as REM are appropriately defined, thereby achieving the above effect. can be further enhanced. The composition of the weld metal according to this embodiment and the reason for limitation will be specifically described below.

<C _(Metal) : 0.020% by mass or more and 0.100% by mass or less>
C is a component that affects the strength of the weld metal. As the C content in the weld metal increases, the strength increases. Therefore, the content of C _(Metal) is 0.020% by mass or more, preferably 0.040% by mass or more, relative to the total mass of the weld metal.
On the other hand, when the C _(Metal) content increases, carbides tend to precipitate in the weld metal, resulting in a decrease in toughness relative to the target strength, and the balance between strength and toughness may be lost. . Therefore, the content of C _(Metal) is 0.100% by mass or less, preferably 0.095% by mass or less, relative to the total mass of the weld metal.

<Si _(Metal) : 0.05% by mass or more and 0.50% by mass or less>
Si is a component that affects the strength and toughness of the weld metal, and by containing a predetermined amount of Si in the weld metal, it is possible to satisfy the required mechanical performance. Therefore, the content of Si _(Metal) is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, relative to the total mass of the weld metal.
On the other hand, Si has a deoxidizing effect, and if Si is contained excessively, there is a high possibility that Si will remain in the weld metal as inclusions, and there is a risk that the balance between strength and toughness will not be achieved. be. Therefore, the content of Si _(Metal) is 0.50% by mass or less, preferably 0.45% by mass or less, relative to the total mass of the weld metal.

<Mn _(Metal) : 0.20% by mass or more and 1.80% by mass or less>
Mn, like Si, is a component that affects the strength and toughness of the weld metal. By containing a predetermined amount of Mn in the weld metal, the required mechanical performance can be satisfied. . Therefore, the content of Mn _(Metal) is preferably 0.20% by mass or more, more preferably 0.50% by mass or more, relative to the total mass of the weld metal.
On the other hand, Mn has a deoxidizing effect, and if Mn is contained excessively, there is a high possibility that Mn will remain in the weld metal as inclusions, and there is a risk that the balance between strength and toughness will not be achieved. be. Therefore, the content of Mn _(Metal) is 1.80% by mass or less, preferably 1.65% by mass or less, relative to the total mass of the weld metal.

<Al _(Metal) : 0.30% by mass or more and 1.50% by mass or less>
Al is a strong deoxidizing component, and by causing an oxidation reaction in the weld metal, it forms an oxide (slag) on the molten pool, and is suitable for welding in all positions, including difficult positions such as vertical welding and upward welding. In , it is an element that is preferably contained in the wire because it improves burn-through resistance. Therefore, the content of Al _(Metal) is preferably 0.30% by mass or more, more preferably 0.40% by mass or more, relative to the total mass of the weld metal.
On the other hand, if Al is contained excessively, there is a high possibility that Al remains in the weld metal as inclusions, which adversely affects the toughness. Therefore, the content of Al _(Metal) is 1.50% by mass or less, preferably 1.10% by mass or less, more preferably 1.00% by mass, based on the total mass of the weld metal. .

<La _(Metal) : 0.008% by mass or less>
La is one type of REM contained in the wire, and acts as a binder that agglomerates oxides of strong deoxidizing elements in the weld metal. In the present embodiment, the lower limit of the La content in the weld metal is not set, but in order to obtain the above effect, the content of La _(Metal) should be 0.001% by mass with respect to the total mass of the weld metal. It is preferable to set it as above.
On the other hand, when the content of La _(Metal) exceeds 0.008% by mass, inclusions are coarsened due to agglomeration, which may adversely affect mechanical performance or cause unacceptable welding defects. be. Therefore, the content of La _(Metal) is 0.008% by mass or less, preferably 0.006% by mass or less, relative to the total mass of the weld metal.

<Ce _(Metal) : 0.002% by mass or more and 0.010% by mass or less>
Ce, like La, is one type of REM contained in the wire, and acts as a binder that agglomerates oxides of strong deoxidizing elements in the weld metal. Therefore, the content of Ce _(Metal) is 0.002% by mass or more, preferably 0.003% by mass or more, based on the total mass of the weld metal.
On the other hand, when the content of Ce _(Metal) exceeds 0.010% by mass, inclusions become coarse due to agglomeration, which may adversely affect mechanical performance or cause unacceptable welding defects. be. Therefore, the content of Ce _(Metal) is 0.010% by mass or less, preferably 0.009% by mass or less, relative to the total mass of the weld metal.

<Fe _(Metal) : 85.0 mass% or more>
Fe is the main element among the elements that are contained in order to satisfy the required mechanical performance in commonly used steel types such as mild steel, high-tensile steel, low-temperature steel, and the like. If the Fe _(Metal) content is less than 85% by mass, the influence of the remaining elements increases, possibly deteriorating the mechanical performance. Therefore, the content of Fe _(Metal) is 85% by mass or more, preferably 87.0% by mass or more, based on the total mass of the weld metal.

<P _(Metal) : 0.0200% by mass or less>
P is an element that lowers the crack resistance and mechanical properties of the weld metal. Therefore, the content of P _(Metal) is 0.020% by mass or less, preferably 0.0100% by mass or less, relative to the total mass of the weld metal.

<S _(Metal) : 0.0200% by mass or less>
S is an element that reduces crack resistance. Therefore, the content of S _(Metal) is 0.0200% by mass or less, preferably 0.0100% by mass or less, relative to the total mass of the weld metal.

<Cr _(Metal) : 1.00% by mass or less>
Cr is a component that affects the strength and toughness of the weld metal. If Cr is contained excessively in the weld metal, it tends to precipitate as carbides at the grain boundaries, resulting in a loss of balance between strength and toughness. There is a risk. Therefore, the content of Cr _(Metal) should be 1.00% by mass or less with respect to the total mass of the weld metal.

<Mo _(Metal) : 1.00% by mass or less>
Mo is a component that improves high-temperature strength, but excessive Mo content in the weld metal may cause an excessive increase in strength, resulting in an imbalance between strength and toughness. Therefore, the content of Mo _(Metal) should be 1.00% by mass or less with respect to the total mass of the weld metal.

<Mg _(Metal) : 0.50% by mass or less>
Like Al, Mg is a strong deoxidizing component, and if Mg is contained excessively, there is a high possibility that Mg remains in the weld metal as inclusions, which adversely affects toughness. Therefore, the content of Mg _(Metal) is 0.50% by mass or less, preferably 0.30% by mass or less, more preferably 0.20% by mass or less, relative to the total mass of the weld metal. preferable.

<Zr _(Metal) : 0.50 mass% or less>
Like Al, Zr is a strong deoxidizing component, and if Zr is contained excessively, there is a high possibility that Zr remains in the weld metal as inclusions, which adversely affects toughness. Therefore, the content of Zr _(Metal) is 0.50% by mass or less, preferably 0.45% by mass or less, relative to the total mass of the weld metal.

<Ti _(Metal) : 0.05 mass% or less>
Like Al, Ti is a strong deoxidizing component, and if Ti is contained excessively, there is a high possibility that Ti remains in the weld metal as inclusions, which adversely affects toughness. Therefore, the content of Ti _(Metal) is 0.05% by mass or less, preferably 0.03% by mass or less, more preferably 0.01% by mass or less, relative to the total mass of the weld metal. preferable.

<Ca _(Metal) : 0.50 mass% or less>
Like Al, Ca is a strong deoxidizing component, and if Ca is contained excessively, there is a high possibility that Ca remains in the weld metal as inclusions, which adversely affects toughness. Therefore, the content of Ca _(Metal) is 0.50% by mass or less, preferably 0.45% by mass or less, relative to the total mass of the weld metal.

<Ni _(Metal) : 3.00% by mass or less>
Ni is a component that stabilizes the austenite structure of the weld metal and improves toughness at low temperatures, and is a component that can adjust the amount of crystallization of the ferrite structure. However, if the weld metal contains an excessive amount of Ni, the strength of the weld metal may be excessively increased and the balance between strength and toughness may be lost. Therefore, the content of Ni _(Metal) is 3.0% by mass or less, preferably 2.5% by mass or less, relative to the total mass of the weld metal.

<B _(Metal) : 0.0090% by mass or less>
B is an element that reduces the crack resistance while preventing the toughness of the weld metal from deteriorating. Therefore, the content of B _(Metal) is 0.0090% by mass or less, preferably 0.0050% by mass or less, relative to the total mass of the weld metal. Further, B has the effect of reducing the rate of brittle fracture, and is preferably 0.0010% by mass or more, more preferably 0.0020% by mass or more.

<Ba _(Metal) : 1.00 mass% or less>
Ba is an element that contributes to deoxidizing the deposited metal and improving welding workability. However, excessive Ba content in the deposited metal may cause arc deflection and deteriorate welding workability. . Therefore, the content of Ba _(Metal) is 1.00% by mass or less, preferably 0.90% by mass or less.

<Nb _(Metal) : 0.001% by mass or less>
Nb is a component that affects mechanical performance such as strength. Nb may be contained in the weld metal in order to satisfy the required mechanical performance in commonly used steel types such as mild steel, high-tensile steel, low-temperature steel, and the like. In this case, the content of Nb _(Metal) is 0.001% by mass or less, preferably 0.0008% by mass or less, relative to the total mass of the weld metal.

<Cu _(Metal) : 0.1% by mass or less>
Cu is an element that contributes to improving the strength and weather resistance of the weld metal. Cu may be contained in the weld metal in order to satisfy the required strength and weather resistance of commonly used steel types such as mild steel, high-tensile steel, low-temperature steel, and the like. In this case, the content of Cu _(Metal) is 0.1% by mass or less, preferably 0.08% by mass or less, relative to the total mass of the weld metal.

<V _(Metal) : 0.001% by mass or less>
V is an element that reduces the toughness and cracking resistance of the weld metal while exerting the effect of improving the strength of the weld metal. Therefore, the content of V 2 _(Metal) in the weld metal is 0.001% by mass or less, preferably 0.0006% by mass or less, relative to the total mass of the weld metal.

<W _(Metal) : 0.1% by mass or less>
W is a component that improves high-temperature strength and pitting corrosion resistance. W may be contained in the weld metal in order to satisfy the required mechanical performance in commonly used steel types such as mild steel, high-tensile steel, low-temperature steel, and the like. In this case, the content of W _(Metal) is 0.1% by mass or less, preferably 0.08% by mass or less, relative to the total mass of the weld metal.

<Ta _(Metal) : 0.1% by mass or less>
Ta is an element that affects mechanical performance such as strength. Ta may be contained in the deposited metal in order to satisfy the required mechanical performance in commonly used steel types such as mild steel, high-tensile steel, low-temperature steel, and the like. In this case, the content of Ta _(Metal) is 0.1% by mass or less, preferably 0.08% by mass or less, relative to the total mass of the weld metal.

<Sr _(Metal) : 1.00 mass% or less>
Sr is an element that is preferably contained in the flux because it contributes to deoxidizing the weld metal and improving welding workability. Therefore, the weld metal may contain Sr. In this case, the content of Sr _(Metal) is 1.00% by mass or less, preferably 0.90% by mass or less, relative to the total mass of the weld metal.

<O _(Metal) : 0.0250% by mass or less>
O exists in the form of a solid solution or an oxide in the weld metal. Excessive O content is highly likely to leave a large amount of oxide-based inclusions in the weld metal, which adversely affects toughness. Therefore, the content of O 2 _(Metal) is 0.0250% by mass or less, preferably 0.0200% by mass or less, relative to the total mass of the weld metal.

<N _(Metal) : 0.0100% by mass or less>
N exists in the form of a solid solution or a nitride in the weld metal. If N is contained excessively, the solid-solution strengthening of the N will excessively increase the strength, and the balance between the strength and the toughness may be lost. Therefore, the content of N _(Metal) is 0.0100% by mass or less, preferably 0.0050% by mass or less, relative to the total mass of the weld metal.

(remainder: impurities)
In the present embodiment, the remainder excluding the above elements is preferably impurities. Impurities mean those that are not intentionally added, and examples of elements other than the above include Sn, Co, Sb, As, and the like. The total content of impurities in the weld metal is preferably 0.010% by mass or less, more preferably 0.005% by mass or less.

In addition, the weld metal according to the present embodiment is, for example, the above [1. It can be produced by gas-shielded arc welding using a basic flux-cored wire].

[3. Welding method]
The welding method according to the present embodiment is the same as described in [1. Basic flux-cored wire] is a method of performing gas-shielded arc welding using the basic flux-cored wire.
Specifically, among various gas-shielded arc welding methods, it is preferable to adopt gas-shielded arc welding using a positive polarity in which the electrode side is - (minus) and the base material side is + (plus). The type of gas used for welding is not particularly limited, but examples thereof include 100% by volume Ar gas, 100% by volume CO ₂ gas, 100% by volume O ₂ gas, and mixed gases thereof. When using Ar gas, it is preferable to use a shielding gas containing 70% by volume or more of Ar. When using _CO2 gas, it is preferable to use a shielding gas containing 70% by volume or more of _CO2 . % CO ₂ gas (hereinafter also referred to as "carbon dioxide gas") is more preferably used. Moreover, when a mixed gas of Ar gas and CO ₂ gas is used, it is preferably a mixed gas of 80% by volume of Ar gas and 20% by volume of CO ₂ gas. The gas flow rate is also not particularly limited, but can be, for example, about 15 to 30 L/min.

The shape of the welding current waveform to be set may be a straight line or a pulse shape. The term "straight line" as used herein means that a special waveform shape is not used. The welding current range is not particularly limited, for example, 200 to 300 A in the case of downward posture, 150 to 250 A in the case of vertical and horizontal welding, and a range combining these conditions in the case of circumferential welding such as fixed pipes. is also used. can be Also, the arc voltage is not particularly limited, and can be set to 15 to 35V, for example. The welding speed is also not particularly limited, but can be, for example, 10 to 50 cm/min. In addition, the wire protrusion length is not particularly limited, and can be set to 10 to 30 mm, for example. However, all the welding conditions are not limited to the above range, and can be appropriately determined according to the application.

[4. Weld joint]
The welded joint according to the present embodiment is the same as described in [3. Welding method]. In the welded joint according to the present embodiment, the portion related to the weld metal is the above [2. It is preferable to have the composition described in Weld Metal].

Hereinafter, the present invention will be described more specifically with reference to invention examples and comparative examples, but the present invention is not limited to these examples, and can be modified within the scope of the gist of the present invention. and all of them are included in the technical scope of the present invention. Also, the welding conditions described here are only examples, and the present embodiment is not limited to the following welding conditions.

Using wires having various compositions shown in Tables 1 to 4 below, weld metals were prepared under the welding conditions shown below, strength (TS) was measured by tensile tests, and impact tests were conducted at -20°C and Charpy absorption energy (CVN) at -46°C was measured.

<Welding conditions>
Welding current: 210A
Arc voltage: 21V
Polarity: DCEN
Shield gas: 100 vol% _CO2
Lamination method: 7 layers, 14 passes Heat input: 0.8 to 1.0 kJ/mm

<Measurement method>
(Tensile test)
A JIS Z 3111: 2005 No. A1 tensile test piece is taken from the obtained weld metal and welded by a tensile test in accordance with JIS Z 3111: 2005 "Tension and impact test method for weld metal". The tensile strength (TS) and 0.2% proof stress (yield stress: PS) of the metal were measured.

(Impact test)
A 2 mm V-notch impact test piece according to JIS Z 3111:2005 was taken from the obtained weld metal and subjected to an impact test in accordance with JIS Z 3111:2005 "Tension and impact test method for weld metal". The absorbed energy (CVN) of the weld metal at -20°C and -46°C was measured at three points, and the average values were used as the values of CVN (-46°C) and CVN (-20°C).

<Evaluation method>
Next, the balance between strength and toughness and the brittle fracture surface ratio were evaluated. Specifically, the values obtained by the following formulas (a) and (b) were calculated, and the balance between strength and toughness was evaluated.
Formula (a): CVN (-46°C)/TS
Formula (b): CVN (-20°C)/TS

It can be judged that the closer the values obtained by the formulas (a) and (b) to 1, the better the balance between strength and toughness. Specifically, with respect to formula (a), if it is 0.100 or more, the balance between strength and toughness is good, if it is 0.150 or more, it is better, and if it is 0.180 or more, As excellent, those rated as good or better were judged as acceptable. Regarding formula (b), if it is 0.150 or more, the balance between strength and toughness is good, if it is 0.200 or more, it is better, and if it is 0.220 or more, it is excellent. If there is, it was judged as acceptable if it was good or better.

In addition, the brittle fracture rate at -20°C and -46°C was also evaluated. The brittle fracture surface ratio is calculated by observing the fracture surface of the test piece after the Charpy impact test and calculating the area ratio of the region exhibiting the brittle fracture surface to the specified cross-sectional area before the test. At −20° C. and −46° C., a brittle fracture rate of 40% or less was considered good, and a rate of 30% or less was considered excellent. The compositions of the obtained weld metals are shown in Tables 5 and 6 below, and the evaluation results are shown in Tables 7 and 8 below. In Tables 1, 3, 5 and 6 below, "-" indicates that the amount was below the detection limit. In addition, "-" in Table 4 indicates that calculation is not possible. The balance of the composition of the wire shown in Tables 1 and 3 below is O, N and impurities, and the balance of the composition of the weld metal shown in Tables 5 and 6 below is Fe and impurities.

Furthermore, in Tables 2 and 4, formulas (1) to (8) represent the following formulas.
Formula (1):
32.1×[Si]−40.6×[Mn]−20.1×[Ni]−19.7×[Mo]−172.6×[C]−408.2×[REM]−5824. 4×[B]−38.4×[Cr]−9960×[P]+43793×[S]

Formula (2):
33.9×[Si]−47.0×[Mn]−22.2×[Ni]−11.9×[Mo]−203.9×[C]−443.5×[REM]−4482. 2×[B]−36.1×[Cr]−15281×[P]+47868×[S]

Formula (3):
0.001×[Fe]−0.71×[Si]+0.08×[Mn]−0.08×[Al]+0.69×[Zr]+0.03×[Ni]+0.01×[Mo ] + 0.32 x [C] + 2.27 x [REM] + 9.57 x [B] + 0.11 x [Cr]

Formula (4):
0.003×[Fe]−0.35×[Si]+0.09×[Mn]−0.13×[Al]+0.22×[Zr]+0.02×[Ni]−0.02×[ Mo]−0.11×[C]+1.17×[REM]+4.30×[B]+0.09×[Cr]

Formula (5): [B oxide]/[B]

Formula (6): [Cr]/([Cr]+[Mo])

Formula (7): [Mo] / ([Cr] + [Mo])

Formula (8): [Al] / ([Al] + [Mg])

However, [REM], [Fe], [C], [Si], [Mn], [P], [S], [Cr], [Mo], [Al], [Zr], [Ni], [B] and [Mg] are respectively REM _(Wire) , Fe _(Wire) , C _(Wire) , Si _(Wire) , Mn (Wire) , P _{(Wire) ,} S _(Wire) , Cr _(Wire) , Mo _(Wire) , Al _(Wire) , Zr _(Wire) , Ni _(Wire) , B _(Wire) , and Mg _(Wire) are expressed in mass % with respect to the total mass of the wire. Further, [B oxide] is a value in which the B conversion value of the B oxide in the wire is represented by mass % with respect to the total mass of the wire. In this example, only B was added in the form of an oxide. In other words, the amount of oxides in the wire of this embodiment is the B ₂ O ₃ conversion value of the value of B _(Wire) .

As shown in Tables 1 to 4 and Tables 7 and 8, Invention Example No. 1 to 16, each component contained in the basic flux-cored wire and the values obtained by the formulas (1) to (8) were within the range specified in the present invention, so the burn-through property was improved. Welding in all positions became possible, and a deposited metal with an excellent balance between strength and toughness was obtained. In addition, invention example No. Comparing 5 to 7, when the Zr content in the wire was 0.045% by mass or less, the balance between strength and toughness was excellent as the B content increased. In addition, invention example No. 5, 11, and 14, when the Zr content in the wire is increased beyond 0.045% by mass while the B content is 0.0046 to 0.0055% by mass, the Zr content At least one of the formulas (a) and (b), which indicate the balance between strength and toughness, tended to decrease with an increase in . That is, it was found that when both the B content and the Zr content approached the upper limits of the ranges specified in the present invention, the balance between strength and toughness deteriorated.

In particular, invention example No. In 9, 10, 12, 13, 15 and 16, the Zr content and B content in the wire were within the preferable ranges specified in the present invention, so the brittle fracture rate and the balance between strength and toughness were all Excellent results.

On the other hand, Comparative Example No. 1 to 19, at least one of the REM content in the wire, the C content, and the values obtained by formulas (1) to (4) were outside the range specified in the present invention, so the brittle fracture rate and At least one of the balance between strength and toughness was unsatisfactory.

In addition, as shown in Tables 5 to 8, invention example No. In Nos. 1 to 16, the content of each component contained in the weld metal was within the range specified in the present invention, so the balance between strength and toughness was excellent. A weld metal was obtained.

As described above, according to the basic flux-cored wire, the welding method, and the method for manufacturing a welded joint according to the present invention, a deposited metal and a welded joint that enable welding in all positions and have an excellent balance between strength and toughness are provided. can be obtained.

Claims (15)

A basic flux-cored wire containing a strong deoxidizing element,
The total amount of the strong deoxidizing elements is 1.50% by mass or more and 4.00% by mass or less with respect to the total mass of the wire,
REM: 0.030% by mass or more and 0.120% by mass or less,
Fe: 85.0% by mass or more,
contains
C: 0.050% by mass or less,
Si: 0.60% by mass or less,
Mn: 2.00% by mass or less,
P: 0.0150% by mass or less,
S: 0.0150% by mass or less,
Cr: 1.00% by mass or less,
Mo: 1.00% by mass or less,
Al: 3.00% by mass or less,
Mg: 3.00% by mass or less,
Zr: 3.000% by mass or less,
Ti: 3.000% by mass or less,
Ca: 3.00% by mass or less,
Ni: 5.00% by mass or less,
B: 0.0200% by mass or less,
Ba: 4.00% by mass or less,
F: 2.00% by mass or less,
and
Value calculated by the following formula (1): 48.0 or less,
Value calculated by the following formula (2): 48.0 or less,
Value calculated by the following formula (3): 0.09 or more,
Value calculated by the following formula (4): 0.14 or more,
A basic flux-cored wire characterized by:
Formula (1):
32.1×[Si]−40.6×[Mn]−20.1×[Ni]−19.7×[Mo]−172.6×[C]−408.2×[REM]−5824. 4×[B]−38.4×[Cr]−9960×[P]+43793×[S]
Formula (2):
33.9×[Si]−47.0×[Mn]−22.2×[Ni]−11.9×[Mo]−203.9×[C]−443.5×[REM]−4482. 2×[B]−36.1×[Cr]−15281×[P]+47868×[S]
Formula (3):
0.001×[Fe]−0.71×[Si]+0.08×[Mn]−0.08×[Al]+0.69×[Zr]+0.03×[Ni]+0.01×[Mo ] + 0.32 x [C] + 2.27 x [REM] + 9.57 x [B] + 0.11 x [Cr]
Formula (4):
0.003×[Fe]−0.35×[Si]+0.09×[Mn]−0.13×[Al]+0.22×[Zr]+0.02×[Ni]−0.02×[ Mo]−0.11×[C]+1.17×[REM]+4.30×[B]+0.09×[Cr]
However, in the formulas (1) to (4), [REM], [Fe], [C], [Si], [Mn], [P], [S], [Cr], [Mo], [Al], [Zr], [Ni] and [B] are respectively the REM, the Fe, the C, the Si, the Mn, the P, the S, the Cr, the Mo, the Al, the It is a value in which the contents of Zr, Ni and B are represented by mass % with respect to the total mass of the wire. For the total wire mass, in addition,
Nb: 0.50% by mass or less,
Cu: 2.00% by mass or less,
W: 1.00% by mass or less,
Ta: 1.00% by mass or less,
V: 1.00% by mass or less,
Sr: 4.00% by mass or less, and
Total of alkali metal elements: 3.00% by mass or less,
containing at least one selected from
2. The basic flux-cored wire of claim 1, wherein the balance is O, N and impurities. The basic flux-cored wire according to claim 1 or 2, wherein the B content is 0.0020% by mass or more and 0.0150% by mass or less with respect to the total mass of the wire. The content of B includes the B conversion value of B oxide,
When the B conversion value of the B oxide with respect to the total mass of the wire is expressed as [B oxide] in mass%,
The basic flux according to any one of claims 1 to 3, wherein the value calculated by formula (5): [B oxide]/[B] is 0.5 or more. input wire. Ba: 4.00% by mass or less,
Ca: 3.00% by mass or less, and Sr: 4.00% by mass or less, containing at least one selected from
The flux contains at least one selected from BaF ₂ , CaF ₂ and SrF ₂ which are fluorides of Ba, Ca and Sr,
The Ba content includes the Ba conversion value of the _BaF2 ,
The Ca content includes the Ca conversion value of the _CaF2 ,
The Sr content includes the Sr conversion value of the _SrF2 ,
The basic flux-cored wire according to any one of claims 1 to 4, wherein the F content includes the F conversion values of the BaF ₂ , the CaF ₂ and the SrF ₂ . 6. The basic flux-cored wire according to claim 5, wherein the F content and the F-equivalent value of all fluorides contained in the flux are equal. 7. The wire according to any one of claims 1 to 6, wherein the oxide content in the wire is 0.005% by mass or more and 0.100% by mass or less with respect to the total mass of the wire. basic flux-cored wire. The Cr content is 0.20% by mass or more and 0.90% by mass or less with respect to the total mass of the wire,
The Mo content is 0.50% by mass or less with respect to the total mass of the wire,
Formula (6): The value calculated by [Cr] / ([Cr] + [Mo]) is 0.20 or more, according to any one of claims 1 to 7. Basic flux cored wire. The Cr content is 0.90% by mass or less with respect to the total mass of the wire,
The content of Mo is 0.10% by mass or more and 0.80% by mass or less with respect to the total mass of the wire,
Formula (7): [Mo] / ([Cr] + [Mo]) The value calculated by is 0.10 or more, according to any one of claims 1 to 7 Basic flux cored wire. As the strong deoxidizing element, 1.00% by mass or more and 2.50% by mass or less of Al is contained with respect to the total mass of the wire,
The Mg is 1.00% by mass or less,
When the content of Mg in the wire is expressed as [Mg] in mass% with respect to the total mass of the wire,
Any one of claims 1 to 9, wherein the value calculated by the formula (8): [Al] / ([Al] + [Mg]) is 0.5 or more and 1.0 or less. A basic flux-cored wire according to any one of the preceding paragraphs. The basic flux cored wire according to any one of claims 1 to 10, characterized in that said REM consists of La and Ce. For the total mass of weld metal,
C: 0.020% by mass or more and 0.100% by mass or less,
Si: 0.05% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.80% by mass or less,
Al: 0.30% by mass or more and 1.50% by mass or less,
Ce: 0.002% by mass or more and 0.010% by mass or less,
Fe: 85.0% by mass or more,
contains
La: 0.008% by mass or less,
P: 0.0200% by mass or less,
S: 0.0200% by mass or less,
Cr: 1.00% by mass or less,
Mo: 1.00% by mass or less,
Mg: 0.50% by mass or less,
Zr: 0.50% by mass or less,
Ti: 0.05% by mass or less,
Ca: 0.50% by mass or less,
Ni: 3.00% by mass or less,
B: 0.0090% by mass or less,
Ba: 1.00% by mass or less,
Nb: 0.001% by mass or less,
Cu: 0.1% by mass or less,
V: 0.001% by mass or less,
W: 0.1% by mass or less,
Ta: 0.1% by mass or less,
Sr: 1.00% by mass or less,
Total of alkali metal elements: 0.05% by mass or less,
O: 0.0250% by mass or less,
N: 0.0100% by mass or less, and
A weld metal characterized in that the balance is impurities. A basic flux-cored wire, characterized in that the weld metal according to claim 12 is obtained. A welding method comprising performing gas-shielded arc welding using the basic flux-cored wire according to any one of claims 1 to 11 and 13. A welded joint, characterized in that it is produced using the welding method of claim 14.