KR102156027B1 - Flux cored wire - Google Patents

Abstract

[Task] A flux cored for gas-shielded arc welding suitable for full-scale welding with excellent balance of all the performances of molten metal sag, spatter generation, slag sag and arc stability, and bead shape and slag peelability Provide wire.
[Solution] The flux-cored wire for gas-shielded arc welding in which the flux is filled in the steel shell is TiO ₂ , Al ₂ O ₃ , metal Al, metal Si and Si oxide converted to SiO ₂ , per total mass of the wire, metal Zr and Zr oxide of ZrO ₂ in terms of value, metal Mg and Mg MgO in terms of values, a fluoride, C and with also the Mn each contained in a predetermined range, Al and the Al ₂ O ₃ in terms of the value of the Al ₂ O ₃ in the oxide , ZrO ₂ conversion value, MgO conversion value, and SiO ₂ conversion value, (Al ₂ O ₃ Conversion value + ZrO ₂ conversion value + MgO conversion value)/SiO ₂ conversion value: 0.35 or more and 1.50 or less are satisfied.

Description

Flux cored wire {FLUX CORED WIRE}

The present invention relates to a flux-cored wire for gas shielded arc welding.

In shipyards, the development of automation and high efficiency of welding is in progress in order to promote life-saving and high-efficiency for welding operations that account for about 30% of the process. In particular, for downward butt welding and horizontal fillet welding, a welding robot, a line welder, and the like have been introduced, and since a large number of exclusive welding materials have been developed, high efficiency has been relatively advanced.

On the other hand, it is difficult to automate the vertical upward welding posture, which is mainly used in block joints in shipbuilding, for the reason that the applied welding point is narrow and that the reversal of the structure is impossible.

As a flux-cored wire suitable for full-scale welding using a welding robot, for example, in Patent Document 1, by appropriately controlling the Al content and the Mg content, it is excellent in upright orientation and welding work other than orientation uprightness. A flux-cored wire having good properties, slag releasability, and impact performance of weld metals has been proposed.

Japanese Patent No. 3824973

However, in full-fledged welding using a welding robot, not only the welding workability of molten metal sag, spatter generation amount, slag sag and arc stability, but also bead shape and slag releasability, it will be excellent in balance. I need it. For this reason, furthermore, development of a flux-cored wire suitable for full-scale welding excellent in these performances is required.

The present invention has been made in light of the above-described situation, and all the performances of welding workability of molten metal sag, spatter generation amount, slag sag and arc stability, and bead shape and slag peelability are excellent in balance, suitable for full-scale welding. It is an object to provide a flux-cored wire for shield arc welding.

The flux-cored wire of the present invention is a flux-cored wire for gas-shielded arc welding in which a steel sheath is filled with a flux, and TiO ₂ : 5.0% by mass or more and 10.0% by mass or less per total mass of the wire, Al ₂ O ₃ : 0.05 mass% or more and 0.50 mass% or less, Metal Al: less than 0.10 mass %, SiO ₂ conversion value of metal Si and Si oxide: 1.0 mass% or more and 3.5 mass% or less, ZrO ₂ of metal Zr and Zr oxide Conversion value: 0.05 mass% or more and 0.50 mass% or less, MgO conversion value of metal Mg and Mg oxide: 0.5 mass% or more and 2.2 mass% or less, fluoride: 0.05 mass% or more and 0.30 mass% or less, C: 0.01 mass% or more and 0.08 mass % Or less, Mn: 2.0% by mass or more and 4.0% by mass or less are contained, and Al ₂ O ₃ conversion values of Al and Al ₂ O ₃ , ZrO ₂ conversion values, MgO conversion values, and SiO ₂ conversion values, ( Al ₂ O ₃ conversion value + ZrO ₂ conversion value + MgO conversion value)/SiO ₂ conversion value: 0.35 or more and 1.50 or less.

The flux-cored wire further contains at least one selected from Na, Na oxide, K and K oxide, and the sum of the Na ₂ O conversion value and the K ₂ O conversion value per total mass of the wire: 0.01% by mass It is preferable to satisfy more than 0.30 mass %.

According to the present invention, the welding workability of molten metal sag, spatter generation amount, slag sag and arc stability, and all the performances of bead shape and slag releasability are excellent in a balance, a flux for gas shielded arc welding suitable for full-scale welding Cored wire can be provided.

Hereinafter, embodiments of the present invention will be described in detail. In addition, the present invention is not limited to the embodiments described below, and can be carried out with arbitrary changes within the scope not departing from the gist of the present invention.

The present inventors studied the contents of various components in the flux-cored wire in order to obtain a flux-cored wire for gas-shielded arc welding in which the welding workability is excellent and the bead shape and the releasability of slag are improved. did. As a result, TiO ₂ , Al ₂ O ₃ , metal Al, metal Si and Si oxide in terms of SiO ₂ , metal Zr and Zr oxide in terms of ZrO ₂ , metal Mg and Mg oxide in terms of MgO, fluoride, C, and found that with the tuned for each component amount of Mn, to appropriately adjust, the total of Al and Al ₂ O ₃ of the Al ₂ O ₃ in terms of values, ZrO ₂ in terms of value and MgO in terms of values for the SiO ₂ in terms of a value effective did.

The flux-cored wire according to the present embodiment (hereinafter, simply referred to as a wire) is TiO ₂ : 5.0 mass% or more and 10.0 mass% or less, Al ₂ O ₃ : 0.05 mass% or more and 0.50 mass% or less, Metal Al: less than 0.10% by mass, SiO ₂ conversion value of metal Si and Si oxide: 1.0 mass% or more and 3.5% by mass or less, ZrO ₂ conversion value of metal Zr and Zr oxide: 0.05 mass% or more and 0.50 mass% or less, metal Mg And Mg oxide in terms of MgO: 0.5% by mass or more and 2.2% by mass or less, fluoride: 0.05% by mass or more and 0.30% by mass or less, C: 0.01% by mass or more and 0.08% by mass or less, Mn: 2.0% by mass or more and 4.0% by mass or less With containing, Al and Al ₂ O ₃ of Al ₂ O ₃ Conversion value, ZrO ₂ conversion value, MgO conversion value, and SiO ₂ conversion value are (Al ₂ O ₃ Conversion value + ZrO ₂ conversion value + MgO conversion value)/SiO ₂ conversion value: 0.35 or more and 1.50 or less are satisfied.

The flux-cored wire of this embodiment is a material filled with a flux in a steel shell. Specifically, the flux-cored wire according to the present embodiment is made of a tubular steel shell and a flux filled inside (inside) the shell. On the other hand, the flux-cored wire may be of either a seamless type without a seam on the outer shell or a seam type with a seam on the outer shell. In addition, the flux-cored wire may or may not have been applied to the wire surface (outside of the outer shell) with plating such as Cu. In addition, the flux-cored wire according to the present embodiment is a so-called mild steel wire.

On the other hand, the wire diameter (diameter) of the flux-cored wire according to the present embodiment is not particularly limited, but from the viewpoint of wire feeding stability, it is preferably 1.2 to 4.0 mm, more preferably 1.2 to 2.4 mm. .

In the flux-cored wire according to the present embodiment, each component has a predetermined content with respect to the total mass of the wire, and the content of some components satisfies a predetermined relational expression. Hereinafter, with respect to the composition of the flux-cored wire according to the present embodiment, the reason for adding the component and the reason for limiting the composition will be described.

On the other hand, in the following description, the amount of each component in the flux-cored wire is defined as the content per total mass of the wire (the total amount of the flux in the sheath and the sheath) unless otherwise noted.

In this embodiment, as Ti oxide, TiO ₂ is contained as a typical Ti oxide. Other oxides may be included as the Ti oxide, but in the present embodiment, these other oxides are also included and described as TiO ₂ . As for the oxide component, the same applies to other oxide components such as SiO ₂ , ZrO ₂ , and Al ₂ O ₃ .

In addition, in the case of "metal Al", for example, it means one or more of "pure metal Al" and "alloy Al", that is, the sum of Al contained in a single metal or an alloy. The same applies to other elements such as "metal Si" and "metal Mg". That is, what is a metal means that it is not an oxide.

In addition, "oxide" means one or more of "single oxide" and "composite oxide". The term "single oxide" refers to an oxide of Si alone (SiO ₂ ), for example, if it is Si, and "composite oxide" refers to a combination of multiple types of these single oxides, such as Zr, Si, and Mg. It refers to both oxides containing a plurality of metal components.

<TiO ₂ : 5.0% by mass or more and 10.0% by mass or less>

TiO ₂ generally acts as a slag former and arc stabilizer. In this embodiment, TiO ₂ is defined as TiO ₂ that converts Ti in the metal Ti and all Ti oxides included in the entire constitution including the flux and the outer shell into TiO ₂ .

If TiO ₂ is less than 5.0% by mass, the amount of slag sufficient to support the molten metal cannot be secured, and the molten metal sags, so TiO ₂ is set at 5.0% by mass or more, preferably 6.0% by mass or more. .

On the other hand, when TiO ₂ exceeds 10.0% by mass, the arc becomes unstable and the generation of spatter increases. Therefore, TiO ₂ is 10.0% by mass or less, preferably 9.0% by mass or less.

<Al ₂ O ₃ : 0.05% by mass or more and 0.50% by mass or less>

Al ₂ O ₃ has an action of increasing the slag solidification point. Here, Al ₂ O ₃ of the Al oxide is Al ₂ O ₃ It is a converted value.

If the content of Al ₂ O ₃ is less than 0.05% by mass, the effect of increasing the slag solidification point cannot be obtained, and the slag sags, so the content of Al ₂ O ₃ is 0.05% by mass or more, preferably 0.07% by mass. Make it above.

On the other hand, when the content of Al ₂ O ₃ exceeds 0.50 mass%, the bead shape deteriorates, so the content of Al ₂ O ₃ is 0.50 mass% or less, and preferably 0.40 mass% or less.

<Metal Al: less than 0.10% by mass>

Metal Al is a component that affects the toughness of the metal of the welded portion and acts as a slag forming agent.

When the metal Al content is 0.10 mass% or more, the bead shape deteriorates, and the toughness of the welded portion is also lowered. For this reason, the Al content is less than 0.10 mass%, preferably less than 0.08 mass%.

<SiO ₂ conversion value: 1.0% by mass or more and 3.5% by mass or less>

Metallic Si and Si oxides act as slag formers and arc stabilizers. In this embodiment, a metallic Si and Si of all the Si oxide included in the overall composition containing the flux and the sheath, and is defined as a value in terms of SiO ₂ in terms of SiO _2.

When the SiO ₂ conversion value is less than 1.0 mass%, the arc becomes unstable and the generation of spatter increases, so the SiO ₂ conversion value is 1.0 mass% or more, preferably 1.2 mass% or more.

On the other hand, when the SiO ₂ conversion value exceeds 3.5% by mass, the slag becomes hard and the slag releasability decreases, so the SiO ₂ conversion value is 3.5% by mass or less, preferably 3.2% by mass or less.

On the other hand, the content of SiO ₂ (Si oxide in terms of SiO ₂ ) is preferably 0.10 mass% or more, more preferably 0.20 mass% or more, preferably 1.00 mass% or less, and more preferably 0.80 mass%. Below.

In addition, the content of the metal Si is preferably 0.4% by mass or more, more preferably 0.5% by mass or more, preferably 1.5% by mass or less, and more preferably 1.3% by mass or less.

<ZrO ₂ conversion value: 0.05% by mass or more and 0.50% by mass or less>

The metal Zr and Zr oxides increase the slag solidification point and act as an arc stabilizer. In the present embodiment, the metallic Zr and Zr in all Zr oxide included in the overall composition containing the flux and the sheath, and is defined as a value in terms of ZrO ₂ in terms of ZrO _2.

If the ZrO ₂ conversion value is less than 0.05% by mass, the effect of increasing the slag solidification point cannot be obtained, the slag sags, and the effect as an arc stabilizer cannot be obtained, so the ZrO ₂ conversion value is 0.05% by mass or more, Preferably it is 0.08 mass% or more.

On the other hand, when the ZrO ₂ conversion value exceeds 0.50 mass%, the arc tends to become unstable and the generation of spatter increases, so the ZrO ₂ conversion value is 0.50 mass% or less, preferably 0.40 mass% or less. do.

<MgO conversion value: 0.5% by mass or more and 2.2% by mass or less>

Metal Mg and Mg oxide, while raising the slag solidification point, have an action as an arc stabilizer. In this embodiment, the metal Mg contained in the entire constitution including the flux and the shell and Mg in all Mg oxides are defined as MgO conversion values converted to MgO.

If the MgO conversion value is less than 0.5% by mass, the effect of increasing the slag solidification point cannot be obtained, the slag sags, and the effect as an arc stabilizer cannot be obtained, so the MgO conversion value is 0.5% by mass or more, preferably Is 0.7% by mass or more.

On the other hand, when the MgO conversion value exceeds 2.2 mass%, the bead shape deteriorates, so the MgO conversion value is set to 2.2 mass% or less, preferably 2.0 mass% or less.

On the other hand, the content of MgO (in terms of MgO of MgO) is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, preferably 0.50% by mass or less, and more preferably 0.40% by mass or less. .

Further, the content of the metal Mg is preferably 0.2% by mass or more, more preferably 0.25% by mass or more, preferably 1.0% by mass or less, and more preferably 0.8% by mass or less.

<Fluoride: 0.05% by mass or more and 0.30% by mass or less>

Fluoride acts as an arc stabilizer.

If the total content of the fluoride contained in the entire composition including the flux and the shell is less than 0.05% by mass, the effect as an arc stabilizer cannot be obtained, so the content of the fluoride is 0.05% by mass or more, preferably 0.06% by mass. Make it above.

On the other hand, if the total content of the fluoride exceeds 0.30 mass%, the slag tends to sag, so the content of the fluoride is 0.30 mass% or less, and preferably 0.26 mass% or less.

As a specific fluoride, K ₂ SiF ₆ , NaF, CaF ₂ etc. are mentioned.

<C: 0.01% by mass or more and 0.08% by mass or less>

C has an effect of improving the hardenability and toughness of the weld metal.

If the C content is less than 0.01% by mass, hardening of the weld metal is insufficient, and toughness cannot be sufficiently obtained. Therefore, the C content is set at 0.01% by mass or more, preferably 0.02% by mass or more.

On the other hand, when the C content exceeds 0.08% by mass, the arc ejection becomes stronger and the amount of spatter generated increases. Therefore, the C content is set at 0.08% by mass or less, preferably 0.07% by mass or less.

<Mn: 2.0% by mass or more and 4.0% by mass or less>

While Mn acts as a deoxidizing agent, it has an effect of improving the strength and toughness in the weld metal.

If the content of Mn is less than 2.0% by mass, due to insufficient deoxidation, welding defects such as blowholes may occur in the welded portion, or the strength and toughness decrease, so the content of Mn is 2.0% by mass or more, preferably 2.2. It should be mass% or more.

On the other hand, when the content of Mn exceeds 4.0% by mass, the strength of the weld metal becomes too large to cause high-temperature cracking, so the content of Mn is set to 4.0% by mass or less, preferably 3.8% by mass or less.

Here, Mn means all Mn contained in metal Mn and Mn oxide.

<(Al ₂ O ₃ Conversion value + ZrO ₂ conversion value + MgO conversion value)/SiO ₂ conversion value: 0.35 or more and 1.50 or less>

In this embodiment, the sum of the Al ₂ O ₃ conversion value, the ZrO ₂ conversion value, and the MgO conversion value with respect to the SiO ₂ conversion value is limited, but the Al ₂ O ₃ conversion value used in the above formula is the flux and the shell. It is assumed that Al in the metal Al and all Al oxides contained in the entire constitution including Al is converted into Al ₂ O ₃ . In addition, the ZrO ₂ conversion value, the MgO conversion value, and the SiO ₂ conversion value are as described above.

If the sum of the SiO ₂ conversion value, the Al ₂ O ₃ conversion value, the ZrO ₂ conversion value, and the MgO conversion value is less than 0.35, the bead shape deteriorates and the slag releasability decreases, so the value of the above relational expression is 0.35. It is set as above, Preferably it is set as 0.45 or more.

On the other hand, when the sum of the SiO ₂ conversion value, the Al ₂ O ₃ conversion value, the ZrO ₂ conversion value, and the MgO conversion value exceeds 1.50, the arc becomes unstable and the bead shape deteriorates, so the value of the above relational expression is It is set to 1.50 or less, preferably 1.30 or less.

<Total of Na ₂ O conversion value and K ₂ O conversion value: 0.01% by mass or more and 0.30% by mass or less>

It is preferable that the flux-cored wire according to the present embodiment further contains at least one selected from Na, Na oxide, K and K oxide as an optional component. And by appropriately adjusting these oxide conversion values, it is possible to obtain a more suitable flux-cored wire in full-wave welding.

Na ₂ O and K ₂ O act as arc stabilizers, but when too much, they act in the direction of lowering the viscosity of the slag, and the slag is liable to sag.

If the sum of the Na ₂ O conversion value and the K ₂ O conversion value contained in the entire composition including the flux and the shell is less than 0.01% by mass, the effect as an arc stabilizer cannot be obtained, so the total value thereof is 0.01% by mass or more. And preferably 0.05% by mass or more.

On the other hand, if the sum of the Na ₂ O conversion value and the K ₂ O conversion value exceeds 0.30 mass%, the slag tends to sag, so the total value thereof is 0.30 mass% or less, preferably 0.25 mass%. It is as follows.

Meanwhile, the Na ₂ O conversion value is a value obtained by converting Na in metal Na and all Na oxides included in the entire composition including the flux and the shell into Na ₂ O. In addition, the K ₂ O in terms of value is a value in terms of a metal and K K K of all oxide contained in the entire composition including the flux and the sheath, and a K ₂ O.

<Fe: 80 to 93% by mass or more>

Fe is a major component of the flux cored wire. From the relationship between the amount of deposition and the composition of other components, the Fe content is preferably 80 to 93% by mass, more preferably 82 to 92% by mass per total mass of the wire.

Here, in the flux-cored wire according to the present embodiment, the above-described Fe, TiO ₂ , Al ₂ O ₃ , metal Al, SiO ₂ conversion value, ZrO ₂ conversion value, MgO conversion value, fluoride, C and Mn are summed. It contains 95% or more. It is preferable that this total is 98% or more.

<balance>

Inevitable impurities are contained in the remainder of the flux-cored wire according to the present embodiment. In addition, although the flux-cored wire according to the present embodiment is a metal-based flux-cored wire, in addition to the components of the above wire, in the flux, within a range that does not interfere with its effect, Cr, Mo, Cu, etc. You may contain a small amount as an additional hardening agent. For example, you may contain Cr, Mo, Cu, etc. in less than 0.1 mass %, respectively, and V ₂ O ₅ in less than 0.5 mass %, respectively. Moreover, you may contain 0.030 mass% or less of P, S, Sn, V, etc., respectively.

<Other: Flux filling rate>

The flux filling rate of the flux-cored wire according to the present embodiment (= flux mass / total wire mass × 100) is not particularly limited.

However, if the flux filling rate is less than 10% by mass, the arc stability deteriorates and the amount of spatter generated increases, and the welding workability decreases, so the flux filling rate is preferably 10% by mass or more, and more preferably It is 14 mass% or more.

On the other hand, if the flux filling rate exceeds 25% by mass, disconnection of the wire occurs, or the powder overflows during the filling of the flux, and the productivity decreases.Therefore, the flux filling rate is preferably 25% by mass or less, and more preferably It should be 20% by mass or less.

Subsequently, a method of manufacturing a flux-cored wire according to the present embodiment will be described.

[Wire manufacturing method]

Although it does not specifically limit as a manufacturing method of the flux-cored wire which concerns on this embodiment, For example, it can manufacture by the method shown below.

First, a steel strip constituting the steel shell is prepared, and the steel strip is formed by a forming roll while being sent in the longitudinal direction to obtain a U-shaped open tube. Next, a flux obtained by mixing various raw materials is filled into the steel shell so as to obtain a predetermined component composition, and then processed so that the cross section becomes circular. After that, it is drawn by cold working to obtain, for example, a flux-cored wire having a wire diameter of 1.2 to 2.4 mm.

On the other hand, you may perform annealing in the middle of cold working. In addition, any structure of a seamless wire obtained by welding a joint of a steel sheath formed in the process of manufacturing and a wire leaving the gap without welding the joint may be employed.

Hereinafter, the present invention will be described in more detail with reference to invention examples and comparative examples, but the present invention is not limited thereto.

Table 1 shows the component content of the flux-cored wires of the invention examples and comparative examples. The main component of the remainder other than the components in Table 1 is Fe, and contains P, S, N, Cu, etc. as unavoidable impurities. In addition, "-" in Table 1 indicates that the corresponding component is not actively added.

Test No. shown in Table 1 above. 1 to 9 (invention example) and test No. A flux-cored wire of 10 to 23 (Comparative Example) was used, a steel plate of JIS G 3106 and SM490A was used as the material to be welded, and 100 mass% CO ₂ was supplied as a shielding gas at a flow rate of 25 liters/min. Each welding test of (1) to (3) was performed, and the weldability was evaluated.

(1) Evaluation of deflection of weld metal and slag by vertical upward welding

By the method shown in Table 2 below, vertical upward welding was performed, and the sag properties of the weld metal and the slag were evaluated. The evaluation criteria are as follows.

(1-1) Evaluation of deflection of weld metal

No sagging of the weld metal occurs, good ones: ○

Weld metal deflection occurred: ×

(1-2) Evaluation of slag deflection

No slag sag, good: ○

Some slag sag occurred, but there was no problem in practical use: △

Slag sagging occurred: ×

(2) Evaluation of spatter generation amount, arc stability, slag peelability and bead shape

By performing vertically upward fillet welding, sensory evaluation of the amount of spatter generation, sensory evaluation of arc stability, and evaluation of slag peelability were performed. Moreover, sensory evaluation was also performed about the bead shape. The evaluation criteria are as follows.

(2-1) Evaluation of spatter generation amount

Low spatter generation (spatter generation: less than 1.5 g/min): ○

Slightly high spatter generation (spatter generation: 1.5 g/min or more): ×

(2-2) Evaluation of arc stability

Good arc concentration: ○

Poor arc concentration and arc spatter: ×

(2-3) Evaluation of slag peelability

Good slag peelability (slag natural peeling rate (=slag natural peeling length/welding length): 25% or more): ○

Poor slag peelability (slag natural peeling rate (=slag natural peeling length/welding length): less than 25%): ×

(2-4) Evaluation of bead shape

Good bead shape: ○

Poor bead shape: ×

(3) Evaluation of mechanical performance

About the metal piece obtained by welding, high temperature cracking, toughness, and strength were evaluated.

(3-1) Evaluation of high temperature cracking

No high temperature cracking: ○

Hot cracking occurred: ×

On the other hand, the high-temperature crack was detected by an X-ray transmission test.

(3-2) Evaluation of toughness

Using the test steel sheet corresponding to JIS G 3106 (SM490A), welding was performed according to the test method for all welded metals specified in JIS Z 3313. The evaluation criteria are as follows.

Absorption energy of 60J or more and less than 90J by Charpy impact test: ○

Absorption energy of less than 60J by Charpy impact test: ×

(3-3) Evaluation of strength

It was set as the same conditions as the conditions in the said toughness evaluation. The evaluation criteria are as follows.

Tensile strength of 500 to 640 MPa: ○

Tensile strength outside the above range: ×

The evaluation results of each of the above welding tests are shown in Table 3 below.

As shown in the results of Table 1 and Table 3, Test No. At 10, since the content of the metal Al exceeds the upper limit of the range of the present invention, the bead shape is poor. Moreover, the evaluation result of toughness is lowering compared with the invention example.

Test No. In 11, since the content of TiO ₂ is less than the lower limit of the range of the present invention, sagging of the weld metal occurs.

Test No. In 12, since the content of Al ₂ O ₃ is less than the lower limit of the range of the present invention, slag sagging occurs.

Test No. In 13, since the content of Al ₂ O ₃ exceeds the upper limit of the range of the present invention, the bead shape is poor.

Test No. At 14, since the value in terms of SiO ₂ is less than the lower limit of the range of the present invention, the arc becomes unstable and the amount of spatter generated is increasing.

Test No. At 15, since the value in terms of SiO ₂ exceeds the upper limit of the range of the present invention, the slag peelability is deteriorating.

Test No. At 16, since the value in terms of ZrO ₂ is less than the lower limit of the range of the present invention, the arc becomes unstable and sagging of the slag occurs.

Test No. At 17, since the value in terms of ZrO ₂ exceeds the upper limit of the range of the present invention, the amount of spatter generation is increasing.

Test No. At 18, since the value in terms of MgO is less than the lower limit of the range of the present invention, the arc becomes unstable and sagging of the slag occurs.

Test No. At 19, since the MgO conversion value exceeds the upper limit of the range of the present invention, the bead shape is poor.

Test No. At 20, since the fluoride content is less than the lower limit of the range of the present invention, the arc becomes unstable.

Test No. At 21, since the fluoride content exceeds the upper limit of the range of the present invention, slag sagging occurs.

Test No. 22 is a value obtained by the formula of (Al ₂ O ₃ conversion value + ZrO ₂ conversion value + MgO conversion value)/SiO ₂ conversion value is less than the lower limit of the range of the present invention, the bead shape is poor, and the slag peelability is also It is falling.

Test No. In 23, since the value obtained by the above equation exceeds the upper limit of the range of the present invention, the arc becomes unstable and the shape of the bead becomes poor.

In contrast, test No. Since all of 1 to 9 satisfy all the prescribed ranges of the present invention, good results are obtained in the welding workability of molten metal sag, spatter generation amount, slag sag and arc stability, and bead shape and slag releasability. have. In addition, good results are obtained in any of high temperature cracking, toughness and strength regarding mechanical performance.

In particular, test No. Since 1-8 satisfy|filled the preferable numerical range in the sum of the Na ₂ O conversion value and K ₂ O conversion value, excellent results were obtained for all evaluations including slag sag.

On the other hand, the welding workability of downward and horizontal fillet welding was also confirmed by the same test, but the invention examples were all favorable.

As described in detail above, according to the present invention, the welding workability of molten metal sag, spatter generation amount, slag sag and arc stability, and bead shape and slag releasability are excellent in balance, suitable for full-scale welding Dragon flux cored wire can be obtained.

Claims (2)

As a flux-cored wire for gas shielded arc welding with a flux filled in a steel sheath,
Per total mass of wire,
TiO ₂ : 5.0% by mass or more and 10.0% by mass or less,
Al ₂ O ₃ : 0.05% by mass or more and 0.50% by mass or less,
Metal Al: less than 0.10 mass%,
SiO ₂ conversion value of metal Si and Si oxide: 1.0 mass% or more and 3.5 mass% or less,
ZrO ₂ conversion value of metal Zr and Zr oxide: 0.05% by mass or more and 0.50% by mass or less,
MgO conversion value of metal Mg and Mg oxide: 0.5 mass% or more and 2.2 mass% or less,
Fluoride: 0.05% by mass or more and 0.30% by mass or less,
C: 0.01% by mass or more and 0.08% by mass or less,
Mn: 2.0% by mass or more and 4.0% by mass or less
With containing,
Al ₂ O ₃ conversion value of the Al and Al ₂ O ₃ , the ZrO ₂ conversion value, the MgO conversion value, and the SiO ₂ conversion value,
(Al ₂ O ₃ conversion value + ZrO ₂ conversion value + MgO conversion value)/SiO ₂ conversion value: A flux cored wire, characterized in that it satisfies 0.35 or more and 1.50 or less. The method of claim 1,
In addition, it contains at least one selected from Na, Na oxide, K and K oxide,
Per total mass of wire,
A flux-cored wire that satisfies the sum of the Na ₂ O conversion value and the K ₂ O conversion value: 0.01% by mass or more and 0.30% by mass or less.