KR20180117135A - Flux cored wire for gas shield arc welding - Google Patents

Abstract

The total amount of Si converted amounts of TiO ₂ , Ni, Mo, C, Si and Si oxides per total mass of wire, the total of B converted amounts of ZrO ₂ , Mn, Al, NaF, B and B oxides, Mg, Of the Na compound and the K-converted amount of the K compound, the F-converted amount of the F compound other than NaF is within the predetermined range, the content of TiO ₂ is set to [TiO ₂ ], the content of Al is set to [Al ], It satisfies 5.00? [TiO ₂ ] / [Al]? 70.00.

Description

Flux cored wire for gas shield arc welding

The present invention relates to flux cored wires for gas shielded arc welding.

Conventionally, gas shielded arc welding using flux cored wires has been performed in various fields in order to perform welding work with high efficiency.

For example, Patent Document 1 discloses a welding method in which good welding workability is maintained in large-volume heat welding such as an amount of heat input of 30 to 50 kJ / cm in welding, good bead is formed in top-down welding and excellent mechanical properties There is disclosed a flux cored wire for gas shield arc welding which can obtain a weld metal.

However, in the technique according to Patent Document 1, it is necessary to add Mg, and the moisture absorption property of the flux cored wire is not studied, and moisture is increased during storage of the flux cored wire.

Various techniques have been created to improve the hygroscopicity of the flux cored wire so far, for example, in Patent Document 2.

Japanese Patent Application Laid-Open No. 2015-205304 Japanese Patent Application Laid-Open No. 2009-255168

Generally, hydrogen is present in the weld metal, but if the amount is large, low-temperature cracking tends to occur. However, the conventional flux cored wire absorbs moisture during storage, which increases the amount of hydrogen in the weld metal. This is because the flux contained in the flux cored wire absorbs moisture in the air.

In the technique according to Patent Document 1, it is essential to add Mg to the raw material in the flux cored wire, and the moisture absorption resistance is inferior.

On the other hand, in order to suppress the moisture content in the flux cored wire, the technique according to Patent Document 2 not only eliminates the joint in the steel shell, but also reduces the diameter of the flux cored wire until the diameter becomes 10.0 mm or less, Lt; RTI ID = 0.0 > 1000 C < / RTI >

However, in the technologies according to Patent Documents 1 and 2, it is difficult to simultaneously achieve a good level of welding workability in the large heat welding, mechanical properties of the obtained weld metal, and resistance to moisture absorption of the flux cored wire .

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a flux cored wire having excellent welding workability in large heat welding, excellent mechanical properties of a welding metal to be obtained, and excellent resistance to moisture absorption of the flux cored wire .

That is, the flux cored wire for gas shielded arc welding according to the present invention is characterized in that it contains TiO ₂ : 4.0 to 10.0% by mass, Ni: 0.2 to 2.0%, Mo: 0.01% By mass or more, ZrO ₂ : 0.1% by mass or more and 1.0% by mass or less, Mn: 0.10% by mass or more, C: 0.01 to 0.10% : 1.3 mass% to 3.5 mass%, Al: 0.10 mass% to 1.00 mass%, NaF: 0.05 mass% to 0.60 mass% By mass or less of MgO: less than 0.10% by mass; MgO: less than 0.10% by mass; a total of Na-converted amounts of Na compounds other than NaF and K-converted amount of K compound: 0.20% TiO ₂ ] / [Al]? 70.00 when the content of TiO ₂ is set to [TiO ₂ ] and the content of Al is set to [Al].

According to this gas-shielded arc welding flux-cored wire, by specifying the content of NaF within a predetermined range, the volume transition of the arc during welding is stabilized, the arc stability is improved, and excellent welding workability is realized in large heat welding . By specifying Ni and Mo within a predetermined range, the mechanical properties of the weld metal obtained by the large heat welding are improved. In addition, by specifying Mg and MgO, which deteriorate moisture absorption resistance, to be less than a predetermined value, good moisture absorption resistance can be obtained.

Further, according to the flux cored wire for gas shielded arc welding, by specifying the value calculated by [TiO ₂ ] / [Al] within a predetermined range, welding workability is improved not only at high current but also at low current, The mechanical properties of the metal can be further improved.

The flux cored wire for gas shielded arc welding according to the present invention may be composed of Al ₂ O ₃ : 0.5 mass% or less, Ca: 0.10 mass% or less, and Ti: 0.25 mass% or less, based on the total mass of the wire.

According to the flux cored wire for gas shielded arc welding, by specifying the content of Al ₂ O ₃ , Ca, and Ti to a predetermined value or less, the welding workability is further improved and the mechanical properties of the weld metal are further improved .

The flux cored wire for gas shielded arc welding of the present invention has excellent welding workability in large heat welding, excellent mechanical properties of the obtained weld metal, and excellent moisture absorption resistance.

In addition, the flux cored wire for gas shielded arc welding of the present invention can exert excellent welding workability regardless of whether the welding current is a high current or a low current, and the welding posture can exhibit excellent welding workability particularly in the bidirectional upper side welding .

Hereinafter, embodiments for carrying out the present invention will be described in detail.

A flux cored wire for gas shielded arc welding (hereinafter referred to as " wire " as appropriate) according to the present embodiment is a wire used for gas shielded arc welding, in which flux is filled in a forced shell.

Specifically, the wire according to the present embodiment is made up of a forced shell showing a cylindrical shape and a flux filled inside the forced shell. On the other hand, the wire may be of any type, such as a seamless type having no joint on the forced shell, and a seam type having a joint on the forced shell. Further, the wire may or may not be plated on the surface (the outside of the steel shell).

On the other hand, the wire diameter (diameter) of the wire according to the present embodiment is not particularly limited, but may be 1.2 to 2.4 mm.

In the wire according to the present embodiment, each component is a predetermined content with respect to the total mass of the wire, and the content of a part of the wire satisfies a predetermined relationship.

Hereinafter, the reason for the content of each component of the wire according to the present embodiment will be described.

In the following description, for example, when simply referred to as "Si", it means at least one of "pure metal Si" and "alloy Si".

The term "oxide" means at least one of "single oxide" and "composite oxide". The term "single oxide" refers to, for example, an oxide (TiO ₂ ) of Ti alone if it is a Ti, and a "composite oxide" means that a plurality of such single oxides are aggregated and, for example, Refers to both oxides containing a plurality of metal components.

[TiO ₂ : 4.0 mass% or more and 10.0 mass% or less]

TiO ₂ plays an important role in supporting the weld metal. However, if the content of TiO ₂ is less than 4.0% by mass, the welding workability is deteriorated at the time of heat welding at a high temperature, and good bead shape and bead appearance can not be secured. On the other hand, if the content of TiO ₂ is more than 10.0 mass%, the slag melting point becomes high, and when the weaving is performed in the upward and upward direction welding, the slag is hardened early. As a result, a weld metal is formed along the rod, so that it becomes a bead in a scaly shape (wave shape), and a good bead shape can not be secured.

Therefore, the content of TiO ₂ is 4.0 mass% or more and 10.0 mass% or less per mass of the wire.

On the other hand, the content of TiO ₂ is preferably 6.0% by mass or more from the viewpoint of making the shape of the bead at the time of heat welding to be higher. The content of TiO ₂ is preferably not more than 8.0% by mass from the viewpoint of a bead shape and a bead appearance in a better bead shape at the time of heat welding at a high temperature.

[Ni: 0.2 mass% or more and 2.0 mass% or less]

Ni has the effect of improving the mechanical properties of the weld metal. However, if the Ni content is less than 0.2 mass%, the toughness of the weld metal deteriorates. On the other hand, if the content of Ni exceeds 2.0 mass%, the strength of the weld metal becomes excessive.

Therefore, the Ni content is 0.2 mass% or more and 2.0 mass% or less per mass of the wire.

On the other hand, in order to improve both the toughness and the strength of the weld metal in the high-temperature heat welding, the content is preferably 0.5% by mass or more, more preferably 1.0% by mass or less.

[Mo: 0.01 mass% or more and 0.50 mass% or less]

Mo has the effect of improving the mechanical properties of the weld metal. However, when the content of Mo is less than 0.01% by mass, the tensile strength of the weld metal at the time of substitution heat application is not sufficiently obtained. On the other hand, if the content of Mo exceeds 0.50 mass%, the weld metal becomes excessively strong.

Therefore, the content of Mo is 0.01 mass% or more and 0.50 mass% or less per mass of the wire. Further, it is preferably not less than 0.10 mass% and not more than 0.30 mass%.

[C: 0.01 mass% or more and 0.10 mass% or less]

C is a component exhibiting an effect of improving the quenching and toughness of the weld metal. However, if the content of C is less than 0.01% by mass, the hardenability of the weld metal is insufficient and the tensile strength of the weld metal is not sufficiently obtained. On the other hand, when the content of C is more than 0.10 mass%, arc injection is strong and the base material is corroded by arc force at the time of welding, so that good bead shape and bead appearance can not be secured.

Therefore, the C content is 0.01 mass% or more and 0.10 mass% or less per mass of the wire. Further, it is preferably 0.03 mass% or more and 0.07 mass% or less.

[Sum of Si-converted amount of Si and Si oxide: 0.20 mass% or more and 1.70 mass% or less]

Si improves the welding workability. However, if the sum of the Si-converted amounts of Si and Si oxides is less than 0.20 mass%, the welding workability is deteriorated and a good bead shape and bead appearance can not be secured. On the other hand, when the total amount of Si and Si oxides converted into Si exceeds 1.70 mass%, grain boundary ferrite precipitation is promoted and toughness of the weld metal deteriorates.

Therefore, the total amount of Si and Si oxides converted into Si is 0.20 mass% or more and 1.70 mass% or less per mass of the wire.

On the other hand, the sum of the Si-converted amounts of Si and Si oxides is preferably 0.30% by mass or more from the viewpoint of forming a bead shape and a bead appearance. The sum of the Si-converted amounts of Si and Si oxides is preferably 1.40 mass% or less from the viewpoint of suppressing deterioration of the toughness of the weld metal.

As described above, both the Si and the Si oxides exhibit the effect of improving the welding workability, but they are strictly different from each other. In other words, Si improves the viscosity of the weld metal during welding, making the weld metal difficult to sag. On the other hand, the Si oxide covers the weld metal with slag, preventing the weld metal from sagging.

On the other hand, the content of each of the Si and Si oxides is not particularly limited, but if the respective contents are specified, they are as follows.

[Si: 0.10 mass% or more and 1.00 mass% or less]

Si improves the weldability by improving the viscosity of the weld metal and making the weld metal difficult to sag. However, if the content of Si is less than 0.10% by mass, the viscosity of the weld metal is lowered and the bead shape may be deteriorated. On the other hand, if the Si content exceeds 1.00 mass%, there is a possibility that the austenite grains become coarse and deteriorate toughness of the weld metal.

Therefore, when the content of Si is specified, it is preferable that the content is 0.10 mass% or more and 1.00 mass% or less per mass of the wire.

On the other hand, the content of Si is more preferably 0.20% by mass or more from the viewpoint of a better bead shape and a bead appearance. The content of Si is more preferably 0.80 mass% or less from the viewpoint of suppressing the deterioration of the toughness of the weld metal.

[SiO ₂ : 0.20 mass% or more and 1.50 mass% or less]

SiO ₂ plays a role of supporting the weld metal as a slag forming agent. However, if the SiO ₂ content is less than 0.20 mass%, the amount of slag becomes insufficient, and the bead may become a shape which is sagging. On the other hand, if the content of SiO ₂ exceeds 1.50% by mass, there is a possibility that the deoxidizing power of the flux is lowered and the toughness of the weld metal is deteriorated.

Therefore, when the content of SiO ₂ is specified, it is preferably 0.20 mass% or more and 1.50 mass% or less per mass of the wire.

On the other hand, the content of SiO ₂ is more preferably 0.40% by mass or more from the viewpoint of forming a bead shape and a bead appearance. Further, the content of SiO ₂ is more preferably 1.30 mass% or less from the viewpoint of suppressing the deterioration of the mechanical properties of the weld metal.

[ZrO ₂ : 0.1 mass% or more and 1.0 mass% or less]

ZrO ₂ plays a role of supporting a weld metal as a slag forming agent in the same manner as SiO ₂ .

However, if the content of ZrO ₂ is less than 0.1% by mass, the melting point of the slag becomes low, and the bead becomes a sagging shape and a good bead appearance can not be secured. On the other hand, if the content of ZrO ₂ exceeds 1.0% by mass, the melting point of the slag becomes excessively high, resulting in a bead shape like a convex shape, and a good bead appearance can not be secured.

Therefore, the content of ZrO ₂ is 0.1 mass% or more and 1.0 mass% or less per mass of the wire.

On the other hand, the content of ZrO ₂ is preferably 0.2% by mass or more from the viewpoint of a better bead shape and a bead appearance. Further, the content of ZrO ₂ is preferably less than 0.6% from the viewpoint of making the bead shape more preferable.

[Mn: 1.3% by mass or more and 3.5% by mass or less]

Mn is a component exhibiting an effect of improving the hardenability and toughness of the weld metal. However, if the content of Mn is less than 1.3% by mass, quenching of the weld metal becomes insufficient, and toughness is not sufficiently obtained. On the other hand, when the content of Mn exceeds 3.5 mass%, the tensile strength of the weld metal becomes excessive and toughness becomes insufficient.

Therefore, the content of Mn is 1.3% by mass or more and 3.5% by mass or less based on the total mass of the wire.

On the other hand, the content of Mn is preferably 2.0% by mass or more from the viewpoint of improving the mechanical properties of the weld metal. The content of Mn is preferably 3.1 mass% or less from the viewpoint of suppressing deterioration of the toughness of the weld metal.

As the Mn source, Mn metal powder, metal powder such as Fe-Mn, Fe-Se-Si-Mn, or alloy powder may be added. In addition, Mn oxide may be added.

[Al: 0.10 mass% or more and 1.00 mass% or less]

Al is a strong deoxidizing element and has the role of improving the mechanical properties by improving the yield of weld metal components having affinity for oxygen. Further, Al is also effective as a denitration element and has an effect of improving the mechanical properties by lowering the yield of N in the weld metal. However, if the Al content is less than 0.10 mass%, the yield of the weld metal component having affinity for oxygen is low, and the denitrification effect is also insufficient, so that sufficient toughness can not be obtained. On the other hand, if the Al content exceeds 1.00 mass%, the yield of the weld metal component becomes excessive and the toughness deteriorates.

Therefore, the content of Al is 0.10 mass% or more and 1.00 mass% or less per mass of the wire.

On the other hand, the content of Al is preferably less than 0.40 mass% from the viewpoint of suppressing deterioration of the toughness of the weld metal.

[NaF: 0.05 mass% or more and 0.60 mass% or less]

Na plays a role in stabilizing the volume transition of the arc during welding, but excessive addition of Na deteriorates the moisture absorption resistance of the wire. On the other hand, F is present as a fluorine compound in the flux, which reduces the hydrogen partial pressure in the welding atmosphere and reduces the amount of diffusible hydrogen in the weld metal. However, the excessive F increases the amount of fume generated during welding, Which deteriorates the capacity transition of the arc in the current region.

However, when NaF is used, the effect of stabilizing the volume transition of the arc during welding (in particular, stabilization in a low current region) can be exhibited and the effect of reducing the amount of diffusion of hydrogen by fluoride can be achieved. However, if the content of NaF is less than 0.05% by mass, the volume transition of the arc during welding in the low current region becomes unstable, the amount of spatter generated increases, and the amount of diffusible hydrogen in the weld metal further increases. On the other hand, if the content of NaF exceeds 0.60 mass%, the moisture absorption resistance of the wire deteriorates, and further, the amount of generated fumes increases.

Therefore, the content of NaF is 0.05 mass% or more and 0.60 mass% or less per mass of the wire.

On the other hand, the content of NaF is preferably 0.15% by mass or more from the viewpoints of improving arc stability, suppressing the amount of spatter generated, and suppressing the amount of diffusible hydrogen. The content of NaF is preferably 0.40 mass% or less from the viewpoints of suppressing deterioration of moisture absorption resistance and suppressing the amount of fume generated.

[Sum of B converted amounts of B and B oxides: 0.0003 mass% or more and 0.0300 mass% or less]

B and B oxides (B ₂ O ₃ ) are added to the flux to add B to the weld metal. In addition, B segregates at the austenite grain boundaries to inhibit the formation of pro-eutectoid ferrite and is effective for improving the toughness of the weld metal. However, if the total amount of the B and B oxides converted into B is less than 0.0003 mass%, most of B is immobilized to the nitride as BN, and the effect of suppressing the generation of pro-eutectoid ferrite is not effective, none. On the other hand, when the total amount of the B and B oxides converted into B exceeds 0.0300 mass%, the strength of the weld metal remarkably increases and the toughness decreases.

Therefore, the total of B converted amounts of B and B oxides is 0.0003 mass% or more and 0.0300 mass% or less per mass of the wire. On the other hand, it is possible to contain only B oxide.

[Mg: less than 0.10 mass%, MgO: less than 0.10 mass%]

Mg and MgO are components likely to be contained as impurities from natural raw materials such as titanium oxide. If the content of Mg is 0.10 mass% or more, the amount of spatter generated increases and the resistance to moisture absorption of the wire is deteriorated by forming a compound with Na. If the content of MgO is 0.10 mass% or more, the bead becomes convex due to the increase in the slag viscosity, and the bead appearance becomes defective, and the moisture absorption resistance of the wire deteriorates for the same reason as Mg.

Therefore, the content of Mg is less than 0.10% by mass and may be 0% by mass per total mass of the wire. Also, the content of MgO is less than 0.10 mass% and may be 0 mass% per total mass of the wire.

[Sum of Na-converted amount of Na compound other than NaF and K-converted amount of K compound: 0.20% by mass or less]

Na and K have the effect of stabilizing the volume transition of the arc during welding, but NaF takes charge of this effect. On the other hand, excessive addition of Na and K deteriorates the moisture absorption resistance of the wire. Specifically, when the total of the Na-converted amount of the Na compound other than NaF and the K-converted amount of the K compound exceeds 0.20% by mass, the moisture absorption resistance of the wire deteriorates and the amount of diffusible hydrogen in the weld metal increases.

Therefore, the sum of the Na-converted amount of the Na compound other than NaF and the K-converted amount of the K compound is 0.20 mass% or less per the total mass of the wire.

On the other hand, either the Na-converted amount in the Na compound other than NaF and the K-converted amount in the K compound may be 0 mass% or both may be 0 mass%.

[F-converted amount of F compound other than NaF: 0.10 mass% or less]

F exists as a fluorine compound in the flux, and has an effect of reducing the hydrogen partial pressure in the welding atmosphere and lowering the amount of diffusible hydrogen in the weld metal, but this effect is taken up by NaF. On the other hand, the addition of excess F increases the amount of fume generated during welding. Specifically, when the F-converted amount of the F compound other than NaF exceeds 0.10 mass%, not only the fume generation amount but also the spatter generation amount is increased and the arc stability is also deteriorated.

Therefore, the F-converted amount of the F compound other than NaF is 0.10% by mass or less and 0% by mass based on the total mass of the wire.

[5.00? [TiO ₂ ] / [Al]? 70.00]

[TiO ₂ ] / [Al] when the content of TiO ₂ is set to [TiO ₂ ] and the content of Al is set to [Al] are important indices that both the mechanical properties of the weld metal and good welding workability are compatible. By setting the value calculated by this formula within a predetermined range, it is possible to maintain good welding workability (particularly, bidirectional superior welding) not only at high current but also at short-time transition welding at low current. However, if the value calculated by [TiO ₂ ] / [Al] is less than 5.00, excessive tensile strength of the weld metal and deterioration of toughness due to excessive deoxidation of Al are caused, and furthermore, , The appearance of the bead may also be defective. On the other hand, when the value calculated by [TiO ₂ ] / [Al] exceeds 70.00, deterioration of the tensile strength and toughness of the weld metal due to lack of deoxidizing power of Al occurs.

Therefore, the value calculated by [TiO ₂ ] / [Al] is from 5.00 to 70.00.

On the other hand, the value calculated by [TiO ₂ ] / [Al] is preferably not less than 7.00, more preferably not less than 14.00 from the viewpoint of better welding workability and mechanical properties of the weld metal. Further, the value calculated by [TiO ₂ ] / [Al] is preferably 60.00 or less, more preferably 40.00 or less, from the viewpoint of improving the mechanical properties of the weld metal.

The wire according to the present embodiment may contain the following components (Al ₂ O ₃ , Ca, Ti) as optional components.

[Al ₂ O ₃ : 0.5 mass% or less]

Al ₂ O ₃ is a slag forming agent, which is a component necessary for forming beads, but the other slag forming agent is responsible for this effect. If the content of Al ₂ O ₃ exceeds 0.5% by mass, the arc becomes unstable and the amount of spatter generated increases.

Therefore, in the case of containing an Al ₂ O ₃ to the wire, the content of Al ₂ O ₃ is not more than 0.5% by mass per the total mass of the wire.

[Ca: 0.10 mass% or less]

Ca is a component likely to be included as an impurity from a natural raw material such as titanium oxide as well as Mg. If the content of Ca exceeds 0.10 mass%, the arc becomes unstable and the spatter generation amount increases.

Therefore, when Ca is contained in the wire, the content of Ca is 0.10 mass% or less per mass of the wire.

[Ti: 0.25 mass% or less]

Ti is a component that improves the mechanical properties of the weld metal. However, when the content of Ti exceeds 0.25 mass%, the weld metal is markedly hardened, and the deterioration of toughness is remarkable. Therefore, when Ti is contained in the wire, the Ti content is 0.25 mass% or less per mass of the wire.

On the other hand, the content of Ti is preferably 0.10 mass% or less from the viewpoint of suppressing the deterioration of the toughness of the weld metal.

[Fe: 75.0 mass% or more and 92.0 mass% or less]

Fe is the main component of the wire. The content of Fe is preferably 75.0% by mass or more and 92.0% by mass or less, and more preferably 80.0% by mass or more and 90.0% by mass or less, based on the total amount of wire,

[The remainder: Fe and inevitable impurities]

The remainder of the wire according to the present embodiment is the above-mentioned Fe and inevitable impurities. In addition to the above-mentioned components of the wire, Cu and Cr may be contained as a slag forming agent in a small amount as MnO, FeO and V ₂ O ₅ as an additional curing agent for the weld metal in the flux. These elements do not affect the object of the present invention.

As the inevitable impurities, Cu, Cr and the like may each contain less than 0.1% by mass, MnO, FeO and V ₂ O ₅ may each be contained by less than 0.5% by mass. Exceeding these upper limits may result in excessive strength or deterioration of welding workability. P, S, and the like may be contained in an amount of 0.030 mass% or less, respectively. Exceeding these upper limits may cause high-temperature cracking or toughness degradation.

In addition, the component or optional ingredient which defines only the upper limit value of the above content may be positively added, but may be included as an inevitable impurity.

On the other hand, when each of the above-described elements is added as an oxide or a nitride, the remaining part of the flux cored wire of the present embodiment includes O and N.

[Other: flux filling rate]

The flux filling rate (= flux mass / total wire mass x 100) of the wire according to the present embodiment is not particularly limited. However, if the flux filling rate is less than 10% by mass, the stability of the arc is deteriorated and the amount of spatter generated increases, and the welding workability is deteriorated. On the other hand, when the flux filling rate exceeds 25 mass%, the productivity is significantly deteriorated, such as disconnection of the wire or overflow of the powder during filling of the flux.

Therefore, the flux filling rate is preferably 10 mass% or more and 25 mass% or less.

Next, a method of manufacturing the wire according to the present embodiment will be described.

[Manufacturing method of wire]

The method for producing the wire according to the present embodiment is not particularly limited, and for example, it can be produced by the following method.

First, a steel band constituting a forced sheath is prepared, and the steel band is formed by a forming roll while being fed in the longitudinal direction to form a U-shaped open pipe. Next, the flux containing various raw materials is charged into a forced shell so as to have a predetermined chemical composition, and thereafter, the flux is processed so as to have a circular section. Thereafter, a flux cored wire having a wire diameter of, for example, 1.2 to 2.4 mm is obtained by cold working. On the other hand, annealing may be performed during the cold working. In addition, any structure can be employed, such as a wire without a joint welded with a joint of a steel shell molded in the course of manufacture, and a wire leaving the joint as it is without being welded.

Example

Hereinafter, the effects of the present invention will be described in detail with reference to Examples and Comparative Examples of the present invention.

[Production method of wire used for various tests]

It was formed into an open tube by a forming roll while passing the steel strip in the longitudinal direction. Next, a predetermined amount of metal, alloy, Fe powder and various raw materials were appropriately added to the flux so as to have the chemical compositions shown in Tables 1 and 2. Next, after machining the wire so as to have a circular shape in cross section, the wire was subjected to cold drawing to obtain wire diameter of about 1.2 mm.

The flux cored wire was produced by the above manufacturing method.

On the other hand, the content of each component shown in Tables 1 and 2 is the content per mass of the wire. "T.Si" shown in Tables 1 and 2 represents the total of Si-converted amounts of Si and Si oxides, "TB" represents the total of B-converted amounts of B and B oxides, "Na + K" Represents the sum of the Na-converted amount of the Na compound other than NaF and the K-converted amount of the K compound, and "F" indicates the F-converted amount of the F compound other than NaF.

[Welding workability]

(Welding condition)

Welding was carried out under the conditions shown in Table 4 using the steel sheets of the compositions shown in Table 3 as the base materials by using the wires of Examples and Comparative Examples to confirm the workability of the welding.

On the other hand, the remainder in the composition of the steel sheet shown in Table 3 is Fe and inevitable impurities.

(Arc stability)

As for the arc stability, the welding of two kinds of postures of horizontal fillet and upward and downward directions was performed for the three welding conditions [1] to [3] shown in Table 4, did. For each of the welding conditions, it was confirmed that the arc was stable in the two types of postures, "? &Quot;, the arc in one kind of postures was stable and the arc in one kind of postures was somewhat unstable, , &Quot; DELTA " indicating that the arc in the posture was slightly unstable and " X " indicating that the arc was unstable in at least one posture.

On the other hand, regarding the arc stability, "O" or "Δ" was judged to be acceptable and "X" was judged to be rejected.

(Bead shape)

With respect to the bead shape, in the three kinds of welding conditions [1] to [3] shown in Table 4, welding was carried out in two postures of horizontal fillet and vertical orientation, Then, the respective welded portions formed were observed and visually evaluated. Specifically, it was confirmed that the bead shape of all the welds obtained in the six kinds of welding tests was smooth and good, and that even if one of the welds obtained in the six welding tests had a bead shape of a convex shape, Was evaluated as " x ".

(Bead appearance)

With respect to the bead appearance, welding was carried out in two kinds of postures of horizontal fillet and vertical orientation in each of the three welding conditions [1] to [3] shown in Table 4, Then, the respective welded portions formed were observed and visually evaluated. Specifically, the bead appearance of all the welds obtained in the six types of welding tests was not good, but "good", and even in one of the welds obtained in the six welding tests, the appearance of the bead was bad Quot; x ".

(Spatter generation amount)

With regard to the amount of spatter generated, two types of postures of horizontal fillet and upward and downward bending were performed in three kinds of welding conditions [1] to [3] shown in Table 4, And then quantitatively evaluated based on the amount of spatters generated at the time of each welding test. Specifically, welding was carried out in an environment provided with a collecting box for securing spatters, in accordance with WES2807: 2000. The arc time was 60 seconds. After completion of the welding, the spatter of the collecting box was sampled and the weight was measured. This was repeated two times, and the average value was defined as the amount of spatter generated. &Quot; " and " x " indicates that all of the spatters were less than 2 g /

(Amount of fume generated)

With respect to the amount of fume generated, welding was carried out in two kinds of postures of horizontal fillet and vertical bending in each of the three welding conditions [1] to [3] shown in Table 4, And then quantitatively evaluated based on the amount of fumes generated at each welding test. Concretely, according to JIS Z 3930: 2013, welding was performed in an environment which does not affect the amount of fume generation. The arc time was set to 60 seconds. At the same time as the welding was started, the suction with the filter material and the sampler mounted was started. After completion of the welding, the suction was performed for 30 seconds. Then, the amount of fume generation was calculated from the difference in mass before and after the fume collection of the filter medium, and this was repeated twice, and the average value was defined as the fume generation amount. &Quot; " in all the fumes generated under 1.5 g / min for the six types of welding tests, and " x " in the case where at least one of the six types of welding tests had generated fumes in excess of 1.5 g / min.

[Evaluation of Weld Metal]

(Welding condition)

In order to evaluate the weld metal, each of the wires of the examples and the comparative examples was used for welding under the conditions shown in Table 6, using the steel sheet having the composition shown in Table 5 as a base material.

On the other hand, the remainder in the composition of the steel sheet shown in Table 5 is Fe and inevitable impurities.

(Mechanical properties)

The mechanical properties of the weld metal were evaluated by a tensile test and an impact test in accordance with the "tensile and impact test method for weld metal" specified in JIS Z 3111: 2005.

Tensile test specimens were A0 test specimens taken from the center of the plate thickness at the center of the weld metal. The impact test specimen was a V-notch specimen obtained from the center of the plate thickness at the center of the weld metal.

? ", 590 to 790 MPa (excluding 610 to 710 MPa) was evaluated as"? ", And those having a tensile strength of 610 to 710 MPa or more and less than 590 MPa or 790 MPa were evaluated as" X ".

The toughness was evaluated as " Good " when the absorption energy at -5 DEG C was 80 J or more, " DELTA "

On the other hand, regarding the tensile strength and toughness, "O" or "Δ" was judged to be acceptable and "X" was judged to be rejected.

[Hygroscopicity]

To evaluate the hygroscopicity, three specimens prepared by cutting the prepared wire to 3 cm were prepared, and the specimens were dried at 110 ° C for one hour before the test, and subjected to moisture absorption for 24 hours in an atmosphere of 30 ° C × 80% . Thereafter, the moisture content of the wire was measured by heating at 750 DEG C in an argon atmosphere. The wire having a moisture content of less than 800 ppm after moisture absorption was evaluated as "? &Quot;

The results of various tests are shown in Tables 7 and 8 below.

As shown in Table 7, the wire No. satisfying the inventive specification of the present invention. No. using J1 to J31. In Examples 1 to 31, the welding workability in the large heat welding was excellent, the obtained weld metal had excellent mechanical properties, and the moisture absorption resistance was good.

On the other hand, the large heat welding according to the present invention is, for example, assuming that heat input welding of 4.1 kJ / mm or more (welding with heat input of 5.5 kJ / mm or more in stricter conditions).

On the other hand, as shown in Table 8, 32 to 57 indicate the wire No. used. Since H1 to H26 did not satisfy the inventive specification of the present invention, the results of acceptance were not obtained in any of the evaluation items. The details are as follows.

No. 32 (wire No. H1) had a bead shape and bead appearance deteriorated because the content of TiO _{2 in} the wire exceeded the upper limit value.

No. 33 (wire No. H2) had a bead shape and bead appearance deteriorated because the content of TiO _{2 in} the wire was less than the lower limit value.

No. 34 (wire No. H3), the Ni content of the wire exceeded the upper limit value, and thus the tensile strength was excessively increased.

No. 35 (wire No. H4), the Ni content of the wire was less than the lower limit value, the toughness was lowered.

No. 36 (wire No. H5), the content of Mo in the wire exceeded the upper limit value, so that the tensile strength was excessively increased.

No. 37 (wire No. H6), the tensile strength was lowered because the content of Mo in the wire was less than the lower limit.

No. 38 (wire No. H7), the C content of the wire exceeded the upper limit value, so that the bead shape and bead appearance deteriorated.

No. 39 (wire No. H8), the content of C of the wire was less than the lower limit value, and thus the tensile strength was lowered.

No. 40 (wire No. H9) had a toughness lowered because the content of T.Si in the wire exceeded the upper limit value.

No. 41 (wire No. H10) had a bead shape and bead appearance deteriorated because the content of T.Si in the wire was less than the lower limit value.

No. 42 (wire No. H11), since the content of ZrO _{2 in} the wire exceeded the upper limit value, the bead shape and bead appearance deteriorated.

No. 43 (wire No. H12), the content of ZrO _{2 in} the wire was less than the lower limit value, so that the bead shape and bead appearance deteriorated.

No. 44 (wire No. H13) had a Mn content exceeding the upper limit of the wire, the tensile strength was excessively increased and the toughness was lowered.

No. 45 (wire No. H14), the toughness was lowered because the Mn content of the wire was less than the lower limit value.

No. 46 (wire No. H15), the toughness was lowered because the content of Al in the wire exceeded the upper limit value.

No. 47 (wire No. H16) had a toughness lowered because the content of Al in the wire was less than the lower limit value and the value calculated by [TiO ₂ ] / [Al] of the wire exceeded the upper limit value.

No. 48 (wire No. H17), the content of NaF in the wire exceeded the upper limit value, so that the fume generation amount increased and the moisture absorption resistance deteriorated.

No. 49 (wire No. H18), since the content of NaF in the wire was less than the lower limit value, the arc stability was deteriorated and the spatter generation amount was increased.

No. 50 (wire No. H19), the content of T.B of the wire exceeded the upper limit value, so that the tensile strength was excessively increased and the toughness was lowered.

No. 51 (wire No. H20), the toughness was lowered because the T.B content of the wire was less than the lower limit.

No. 52 (wire No. H21), the value calculated by [TiO ₂ ] / [Al] of the wire exceeded the upper limit value, so that the tensile strength was lowered and the toughness was lowered.

No. 53 (wire No. H22), the value calculated by [TiO ₂ ] / [Al] of the wire was less than the lower limit value, the bead shape and bead appearance deteriorated and the tensile strength was increased and the toughness was lowered .

No. 54 (wire No. H23), since the content of Mg in the wire exceeded the upper limit value, the spatter generation amount increased and the moisture absorption resistance deteriorated.

No. 55 (wire No. H24), since the content of MgO in the wire exceeded the upper limit value, the bead appearance deteriorated and the moisture absorption resistance deteriorated.

No. 56 (wire No. H25), the moisture absorption resistance was deteriorated because the content of Na + K in the wire exceeded the upper limit value.

No. 57 (wire No. H26), the content of F in the wire exceeded the upper limit, so that the spatter generation amount and the fume generation amount increased.

Although the present invention has been described in detail with reference to the embodiments and the examples, the scope of the present invention is not limited to the above description, and the scope of the right should be broadly interpreted based on the description of the claims. It is needless to say that the content of the present invention can be widely modified or changed on the basis of the above description.

The present application is based on Japanese Patent Application (Japanese Patent Application No. 2016-062574) filed on March 25, 2016, the content of which is incorporated herein by reference.

The flux cored wire for gas shielded arc welding according to the present invention is excellent in welding workability in large heat welding, excellent in moisture absorption resistance and mechanical properties of the weld metal, do.

Claims (2)

Per total mass of wire,
TiO ₂ : 4.0% by mass or more and 10.0% by mass or less,
0.2% by mass or more and 2.0% by mass or less of Ni,
Mo: 0.01 mass% or more and 0.50 mass% or less,
C: 0.01 mass% or more and 0.10 mass% or less,
The total amount of Si and the converted amount of Si oxide in terms of Si: 0.20 mass% or more and 1.70 mass% or less,
ZrO ₂ : 0.1% by mass or more and 1.0% by mass or less,
Mn: 1.3% by mass or more and 3.5% by mass or less,
Al: 0.10 mass% or more and 1.00 mass% or less,
Not less than 0.05 mass% and not more than 0.60 mass% of NaF,
B and B oxide: 0.0003 mass% or more and 0.0300 mass% or less,
Mg: less than 0.10 mass%
MgO: less than 0.10 mass%
The sum of Na-converted amount of Na compound other than NaF and K-converted amount of K compound: 0.20% by mass or less,
F-converted amount of F compound other than NaF: 0.10 mass% or less
In addition,
The content of TiO ₂ [TiO _2], when the content of Al in _{[Al], 5.00≤ [TiO 2} ] / [Al] for gas shielding, comprising a step of satisfying the ≤70.00 arc welding flux cored wire. The method according to claim 1,
Per total mass of wire,
Al ₂ O ₃ : 0.5 mass% or less,
Ca: 0.10 mass% or less,
Ti: 0.25 mass% or less
Wherein the flux cored wire is a gas-shielded arc-welded flux cored wire.