JP2021142547A - Flux-cored wire for gas shield arc-welding of sea water resistant steel - Google Patents

Abstract

To provide a flux-cored wire for gas shield arc-welding of sea water resistant steel having welding workability excellent in whole attitude welding of a pipe.SOLUTION: A flux-cored wire for gas shield arc-welding of sea water resistant steel contains, in mass% to wire total mass of the sum of steel sheath and flux, C of (0.03 to 0.12)%, Si of (0.1 to 1.0)%, Mn of (1.3 to 2.8)%, Cu of (0.01 to 0.7)%, Cr of (0.5 to 1.5)% and Al of (0.02 to 0.30)% and further contains, in mass% to wire total mass, in flux, the sum of TiO2 reduced value of (3.5 to 7.0)%, the sum of SiO2 reduced value of (0.1 to 0.6)%, the sum of ZrO2 reduced value of (0.1 to 1.0)%, the sum of Al2O3 reduced value of (0.01 to 0.50)%, the sum of Na reduced value and K reduced value of (0.01 to 0.30)%, Mg of (0.1 to 0.7)%, B of (0.001 to 0.010)% and the sum of F reduced value of (0.01 to 0.15)%.SELECTED DRAWING: None

Description

The present invention relates to a flux-welded wire for gas shielded arc welding of corrosion-resistant steel, which was developed to enhance corrosion resistance in the ocean, and has a small amount of spatter and excellent welding workability in all-position weldability of steel pipes. Related to flux-welded wire for gas shielded arc welding of steel.

Fixed pipes such as crude oil tankers, FPSO (floating production storage and shipping equipment) oil filling pipes, and ballast pipes are used for a long period of time because the coating film on the inner surface of the pipes is damaged and local corrosion occurs within the life of the ship. It requires several repairs or replacement of the pipe part. Therefore, instead of coating carbon steel, corrosion-resistant steel has been conventionally applied for the purpose of suppressing pitting corrosion and corrosion thinning due to aging.

Generally, flux-cored wire for all-position welding _{contains a large amount of slag-forming agent mainly composed of TiO 2,} so metal does not easily drip in vertical or upward-position welding, and a good bead shape can be obtained. In welding, the toe on the lower plate side tends to have a bulging bead shape. Therefore, there is a strong demand for providing a flux-cored wire that can obtain a good fillet bead shape not only in horizontal fillet welding but also in vertical or upward posture welding by semi-automatic welding.

Patent Document 1 is a technique relating to a shielded metal arc welding rod for seawater resistant steel, but the shielded metal arc welding rod has a problem that the welding efficiency is inferior to that of a wire containing flux. Further, since a small amount of Mo is added to the shielded metal arc welding rod in order to improve the corrosion resistance, there is a problem that the toughness of the weld metal is not stable.

Flux-filled wires having good welding workability applied to weathering steel are disclosed in, for example, Patent Document 2 and Patent Document 3. However, Patent Document 1 is a type in which a stable rust layer is formed on the steel surface by containing Cu, Cr, and Ni specified in JIS Z3320, and Patent Document 2 is a Cu—Ni—Ti-based high weathering steel. Since it is a target, there is a problem that corrosion resistance cannot be obtained when it is applied in a seawater environment.

Japanese Unexamined Patent Publication No. 50-80244 Japanese Unexamined Patent Publication No. 2011-125904 Japanese Unexamined Patent Publication No. 2000-288781

Therefore, the present invention has been devised in view of the above-mentioned problems. When welding seawater-resistant steel, the amount of spatter generated is small, and the welding workability is excellent in all-position weldability of steel pipes. It is an object of the present invention to provide a flux-containing wire for gas shielded arc welding of seawater steel.

The gist of the present invention is a wire containing a flux for gas shield arc welding of seawater-resistant steel obtained by filling a steel outer skin with flux, in which the mass% of the total weight of the wire is the total of the steel outer skin and the flux. 0.03 to 0.12%, Si: 0.1 to 1.0%, Mn: 1.3 to 2.8%, Cu: 0.01 to 0.7%, Cr: 0.5 to 1. Contains 5%, Al: 0.02 to 0.30%, and further, in mass% with respect to the total weight of the wire, the total TiO ₂ conversion value of Ti oxide in the flux: 3.5 to 7.0%. , Si oxide _{total SiO 2} conversion value: 0.1-0.6%, Zr oxide ZrO ₂ conversion value total: 0.1-1.0%, Al oxide Al ₂ O ₃ conversion Total value: 0.01 to 0.50%, Na oxide, Na fluoride, K oxide and K fluoride, one or more Na conversion values and K conversion value total: 0.01 to Contains 0.30%, Mg: 0.1 to 0.7%, B: 0.001 to 0.010%, total F conversion value of metal fluoride: 0.01 to 0.15%, and the balance Is characterized by being composed of Fe of a steel outer skin, iron powder in a flux, Fe content of an iron alloy powder, and unavoidable impurities.

Further, it is characterized by containing 0.02 to 0.50% of Ni: 0.02 to 0.50% in total of the steel outer skin and the flux in mass% with respect to the total mass of the wire.

Further, a flux-cored wire for gas shielded arc welding of seawater-resistant steel, which contains Ti: 0.01 to 0.10% in total of the steel outer skin and the flux in mass% with respect to the total mass of the wire. It is in.

According to the flux-welded wire for gas shielded arc welding of seawater-resistant steel of the present invention, when welding seawater-resistant steel, the amount of spatter generated is small, the all-position weldability of the steel pipe is good, and the weld metal is stable. It is possible to provide a flux-filled wire for gas-shielded arc welding of seawater-resistant steel, which can secure toughness and obtain high-quality weld metal.

The present inventors have conducted various studies on a wire containing a flux for gas shielded arc welding of seawater-resistant steel in order to obtain a welding workability that is excellent in all-posture weldability of a steel pipe with a small amount of spatter.

As a result, the present inventors have optimized the component balance between the weld metal and the base metal component by adjusting the amount of Cu and Cr added to the flux to an appropriate amount and not adding Mo, and in a seawater environment. We have found a way to balance corrosion resistance and mechanical performance. It was also found that the corrosion resistance is further improved by adding an appropriate amount of Ni.

Further, the present inventors stabilize the arc and reduce the amount of spatter generated by adjusting the appropriate amounts of C, Ti oxide, fluorine compound, Na compound and K compound, and Si, Mn, Ti oxide and Si oxidation. It was found that the bead shape is improved by adjusting the amount of the compound.

Further, the present inventors can obtain that the metal sagging of the weld metal can be suppressed and the flux can be suppressed particularly at the time of vertical improvement welding by setting the amounts of Al, Ti oxide, Zr oxide and Al oxide to appropriate amounts. It has been found that a weld metal having excellent mechanical performance, particularly toughness, can be stably obtained by adjusting the amounts of C, Si, Mn, Mg and B in the incoming wire to an appropriate amount. It was also found that the toughness of the weld metal is further improved by adding an appropriate amount of Ti.

Hereinafter, the component composition of the flux-cored wire for gas shielded arc welding of the seawater-resistant steel of the present invention, its content, and the reason for limiting each component composition will be described. The composition of each component is expressed in% by mass with respect to the total mass of the wire, and when the mass% is expressed, it is simply expressed as%.

[Total of steel outer skin and flux C: 0.03 to 0.12%]
C has the effect of stabilizing the arc and making the droplet size finer. If C is less than 0.03%, the arc is unstable, it becomes difficult to atomize the droplets, and the amount of spatter generated increases. On the other hand, when C exceeds 0.12%, C is excessively retained in the weld metal and the toughness is lowered. Therefore, C is set to 0.03 to 0.12%. In addition to the components contained in the steel outer skin, C can be added from metal powder from flux, alloy powder, and the like.

[Total of steel outer skin and flux Si: 0.1 to 1.0%]
Part of Si becomes welding slag during welding to improve the bead shape and contribute to the improvement of welding workability. If Si is less than 0.1%, the weld bead shape becomes defective. On the other hand, when Si exceeds 1.0%, Si is excessively retained in the weld metal and the toughness is lowered. Therefore, Si is 0.1 to 1.0%. In addition to the components contained in the steel outer skin, Si can be added from alloy powders such as metal Si, Fe-Si, and Fe-Si-Mn from flux.

[Mn: 1.3 to 2.8% in total of steel outer skin and flux]
Similar to Si, Mn becomes a welding slag during welding to improve the bead shape, contributes to the improvement of welding workability, and acts as a deoxidizer to improve the toughness of the weld metal. If Mn is less than 1.3%, Mn does not sufficiently yield in the weld metal, the toughness of the weld metal decreases, and the bead shape becomes poor. On the other hand, when Mn exceeds 2.8%, Mn is excessively yielded in the weld metal, the strength becomes too high, and the toughness decreases. Therefore, Mn is set to 1.3 to 2.8%. In addition to the components contained in the steel outer skin, Mn is added from alloy powders such as metal Mn, Fe-Mn, and Fe-Si-Mn from flux.

[Cu: 0.01-0.7% in total of steel outer skin and flux]
Cu is an essential element for suppressing the crystallization and coarsening of rust particles during the formation of the rust layer and maintaining the denseness of the rust layer. If Cu is less than 0.01%, this effect cannot be sufficiently obtained, and the corrosion resistance of the weld metal is lowered. On the other hand, when Cu exceeds 0.7%, high-temperature cracking is likely to occur and the toughness of the weld metal is lowered. Therefore, Cu is set to 0.01 to 0.7%. In addition to the components contained in the steel outer skin, Cu can be added from Cu plating on the wire surface, metal Cu from flux, and alloy powder such as Fe-Cu.

[Total Cr: 0.5-1.5% of steel outer skin and flux]
Cr is an essential element for imparting corrosion resistance to the weld metal. If Cr is less than 0.5%, this effect cannot be sufficiently obtained, and the corrosion resistance of the weld metal is lowered. On the other hand, when Cr exceeds 1.5%, the strength of the weld metal becomes too high and the toughness decreases. Therefore, Cr is set to 0.5 to 1.5%. In addition to the components contained in the steel outer skin, Cr can be added from alloy powders such as metal Cr and Fe—Cr from flux.

[Total of steel outer skin and flux Al: 0.02 to 0.30%]
Al becomes molten slag as Al oxide during welding, adjusts the viscosity and melting point of the welding slag, and has an effect of preventing molten metal from dripping, especially in vertical improvement welding. However, if Al is less than 0.02%, this effect cannot be sufficiently obtained, and the molten metal tends to drip during vertical improvement welding. On the other hand, when Al exceeds 0.30%, it remains excessively in the weld metal as an Al oxide and the toughness of the weld metal decreases. Therefore, Al is 0.02 to 0.30%. In addition to the components contained in the steel outer skin, Al can be added from alloy powders such as metal Al, Fe-Al, and Al-Mg from flux.

_{[Total of TiO 2} conversion values of Ti oxide in flux: 3.5 to 7.0%]
The Ti oxide contributes to the stabilization of the arc during welding, and also has the effect of forming a welding slag to improve the shape of the welding bead and contributing to the improvement of welding workability. In particular, in vertical improvement welding, it has the effect of adjusting the viscosity and melting point of the molten slag and preventing the molten metal from dripping. In addition, a part of the Ti oxide remains in the weld metal as fine Ti oxide to refine the microstructure of the weld metal and improve the toughness of the weld metal. _{If the total of the TIO 2} conversion values of the Ti oxide is less than 3.5%, these effects cannot be sufficiently obtained, the arc becomes unstable, the amount of spatter generated is large, and the bead shape becomes poor. _{Further, if the total of the TiO 2} conversion values of the Ti oxide is less than 3.5%, the molten metal drips in the vertical improvement welding, it becomes difficult to continue the welding, and the toughness of the weld metal is lowered. On the other hand, when _{the total of the TIO 2} conversion values of the Ti oxide exceeds 7.0%, the arc becomes stable and the amount of spatter generated decreases, but the Ti oxide remains excessively in the weld metal and the toughness decreases. do. Therefore, _{the total TiO 2} conversion value of Ti oxide is 3.5 to 7.0%. The Ti oxide can be added from rutile sand from flux, titanium oxide, titanium slag, illuminate and the like.

_{[Total SiO 2} conversion value of Si oxide in flux: 0.1-0.6%]
The Si oxide has the effect of adjusting the viscosity and melting point of the molten slag to improve the slag encapsulation property. _{If the total SiO 2} conversion value of the Si oxide is less than 0.1%, this effect cannot be sufficiently obtained and the bead shape becomes poor. On the other hand, when _{the total SiO 2} conversion value of the Si oxide exceeds 0.6%, the basicity of the molten slag decreases, the amount of oxygen in the weld metal increases, and the toughness decreases. _{Therefore, the SiO 2} conversion value of the Si oxide is set to 0.1 to 0.6%. The Si oxide can be added from silica sand from flux, potassium feldspar, sodium silicate, zircon sand and the like.

Total of ZrO ₂ conversion value of Zr oxides in the flux: 0.1% to 1.0%]
The Zr oxide has the effect of adjusting the viscosity and melting point of the molten slag and preventing the molten metal from dripping, especially in the vertical welding. _{If the total of the ZrO 2} conversion values of the Zr oxide is less than 0.1%, this effect cannot be sufficiently obtained, and the molten metal tends to drip during the vertical welding. On the other hand, _{if the total of the ZrO 2} conversion values of the Zr oxide exceeds 1.0%, the peelability of the slag becomes poor. Therefore, the sum of ZrO ₂ conversion value of Zr oxide is 0.1 to 1.0%. Zr oxide can be added from zirconium oxide from flux, zircon sand, etc., and is contained in a small amount in Ti oxide.

_{[Total Al 2} O ₃ conversion value of Al oxide in flux: 0.01 to 0.50%]
The Al oxide has the effect of adjusting the viscosity and melting point of the molten slag and preventing the molten metal from dripping, especially in the vertical welding. If the total of the Al ₂ O ₃ conversion values of the Al oxide is less than 0.01%, this effect cannot be sufficiently obtained, and the molten metal tends to drip during the vertical welding. On the other hand, _{if the total of the Al 2} O ₃ conversion values of the Al oxide exceeds 0.50%, the Al oxide cannot float and separate from the molten pool during welding and is left behind, resulting in slag entrainment. Therefore, _{the total of Al 2} O ₃ conversion values of Al oxide is 0.01 to 0.50%. Al oxide can be added from alumina from flux, potassium feldspar, and the like.

[Total of Na-equivalent value and K-equivalent value of one or more kinds of Na oxide, Na fluoride, K oxide and K fluoride in flux: 0.01 to 0.30%]
Na oxide, Na fluoride, K oxide and K fluoride have the effect of stabilizing the arc. If the sum of the Na conversion value and the K conversion value of Na oxide, Na fluoride, K oxide and K fluoride is less than 0.01%, the effect cannot be sufficiently obtained and the arc becomes unstable. On the other hand, if the sum of the Na-equivalent value and the K-equivalent value of Na oxide, Na fluoride, K oxide and K fluoride exceeds 0.30%, the slag peelability and the bead shape become poor, and the amount of spatter generated becomes poor. More. Therefore, the sum of the Na-equivalent value and the K-equivalent value of one or more kinds of Na oxide, Na fluoride, K oxide and K fluoride is 0.01 to 0.3%. Incidentally, Na oxide, Na fluoride, K oxides and K fluorides, added from sodium silicate, potassium feldspar from the solid matter content and flux of water glass consisting of potassium silicate, NaF, _KF, K 2 SiF _6, etc. The Na conversion value and the K conversion value are the total amount of Na and K contained therein.

[Mg in flux: 0.1 to 0.7%]
Mg is a strong deoxidizer and has the effect of reducing oxygen in the weld metal and increasing the toughness of the weld metal. If Mg is less than 0.1%, this effect cannot be sufficiently obtained and the toughness of the weld metal is lowered. On the other hand, if Mg exceeds 0.7%, it reacts violently with oxygen in the arc during welding, and the amount of spatter generated increases, resulting in poor welding workability. Therefore, Mg is set to 0.1 to 0.7%. In addition, Mg can be added from alloy powders such as metal Mg and Al-Mg from flux.

[Total of steel outer skin and flux B: 0.001 to 0.010%]
B has the effect of improving the toughness of the weld metal by making the microstructure of the weld metal finer by adding a small amount. If B is less than 0.001%, this effect cannot be sufficiently obtained and the toughness of the weld metal is lowered. On the other hand, when B exceeds 0.010%, the strength of the weld metal becomes too high, the toughness decreases, and high-temperature cracking easily occurs in the weld metal. Therefore, B is 0.001 to 0.010%. In addition to the components contained in the steel outer skin, B can be added from alloy powders such as Fe-B and Fe-Mn-B from flux.

[Total F conversion value of metal fluoride in flux: 0.01 to 0.15%]
Metal fluoride has the effect of stabilizing the arc. If the total F conversion value of the metal fluoride is less than 0.01%, this effect cannot be sufficiently obtained and the arc becomes unstable. On the other hand, when the total F conversion value of the metal fluoride exceeds 0.15%, the arc becomes unstable and a large amount of spatter is generated. In addition, molten metal dripping is likely to occur in the vertical welding. Further, when the total F conversion value of the metal fluoride exceeds 0.15%, the weld metal solidifies while the slag component is left behind at the bottom of the bead, so that slag entrainment occurs. Therefore, the total F conversion value of the metal fluoride is 0.01 to 0.15%. The metal fluoride _{can be added from CaF 2} , NaF, KF, LiF, MgF ₂ , K ₂ SiF ₆ , AlF _3, etc. from the flux, and the F conversion value is the total amount of F contained therein.

[Total of steel outer skin and flux Ni: 0.02 to 0.50%]
Ni has the effect of further improving the corrosion resistance of the weld metal. If Ni is less than 0.02%, this effect cannot be sufficiently obtained. On the other hand, if Ni exceeds 0.50%, the strength of the weld metal becomes too high and the toughness decreases. Therefore, Ni is set to 0.02 to 0.50%. In addition to the components contained in the steel outer skin, Ni can be added from alloy powders such as metal Ni, Fe-Ni, and Ni-Mg from flux.

[Total of steel outer skin and flux Ti: 0.01-0.10%]
Ti has the effect of refining the structure of the weld metal to further improve toughness. If Ti is less than 0.01%, the effect of improving the toughness of the weld metal cannot be obtained. On the other hand, when Ti exceeds 0.10%, an upper bainite structure that inhibits the toughness of the weld metal is formed and the toughness becomes low. Therefore, Ti is set to 0.01 to 0.10%. In addition to the components contained in the steel outer skin, Ti can be added from alloy powders such as metal Ti and Fe-Ti from flux.

The flux-cored wire for gas shielded arc welding of seawater-resistant steel according to the present invention has a structure in which a steel outer skin is formed into a pipe shape and the inside thereof is filled with flux. As for the types of wires, seamless wires are used for the steel outer skin obtained by welding the seams of the molded steel outer skin, and seams are used for the steel outer skin without welding the seams of the steel outer skin. It can be roughly divided into the wires it has. In the present invention, a wire having any structure may be adopted. However, a wire with a seamless steel outer skin can be annealed for the purpose of reducing the amount of water in the wire, and since there is no moisture absorption of the flux after manufacturing, the amount of diffusible hydrogen in the weld metal is reduced. However, since it is possible to improve the low temperature cracking resistance, it is preferable to use a seamless wire on the steel outer skin.

The rest of the flux-containing wire for gas shield arc welding of the seawater-resistant steel of the present invention is Fe of the steel outer skin, Fe, Fe-Mn, Fe-Si alloy, etc. in iron powder added from the flux for component adjustment. Fe content and unavoidable impurities of the iron alloy powder. Further, although not particularly limited, the flux filling rate is set to 8 to 20% with respect to the total mass of the wire from the viewpoint of productivity, and V and Nb are V: 0.05% or less from the viewpoint of the strength of mechanical performance. Nb: preferably 0.05% or less.

Hereinafter, the effects of the present invention will be specifically described with reference to Examples.

First, JIS G3141 SPCC (C: 0.002 to 0.06% by mass) is used for the steel outer skin, the steel outer skin is formed into a U shape, and the flux is filled with a filling rate of 8 to 20% to C. After forming into a shape, the seams of the steel outer skin were welded to form a pipe and wire, and flux-cored wires having various components shown in Tables 1 and 2 were prototyped. The prototype wire diameter was 1.2 mm.

Using these prototype wires, the welding workability by horizontal fillet welding and vertical improvement welding was investigated.

Welding workability is as follows: Horizontal fillet welding and vertical lead welding are performed on a T-shaped test piece of JIS G 3106 SM490A with a plate thickness of 16 mm under the welding conditions shown in Table 3, and the arc state and spatter at that time. The state of occurrence, slag peelability, quality of bead shape, and presence or absence of metal dripping were visually confirmed.

In the weld metal test, two-layer buttering welding is performed on JIS G 3106 SM490A with a plate thickness of 20 mm, and then welding is performed according to JIS Z 3111 using a buttering steel plate with groove processing, and a tensile test piece is performed from the center of the weld metal in the plate thickness direction. (A0) and an impact test piece (2 mm V notch test piece) were collected and subjected to a mechanical test. In the evaluation of the tensile test, the tensile strength was good at 550 to 650 MPa. The impact test was evaluated by performing a Charpy impact test at 0 ° C., and the average absorbed energy of the three repetitive lines was 70 J or more. At that time, the presence or absence of high temperature cracks was visually confirmed during the initial layer welding, and the corrosion resistance was investigated. These results are summarized in Tables 4 and 5.

In the X-ray transmission test, when slag entrainment, blow hole, and poor penetration were found, the type of the defect was indicated, and when the above-mentioned defect was not found at the joint welding length of 500 mm, it was regarded as no defect.

For the corrosion resistance test, the surplus is ground from the test piece investigated for the weld metal test, and a strip of 20 mm thick, 100 mm wide, and 200 mm long with the weld bead in the longitudinal direction is used as the test piece. An exposure test was conducted for 3 years in the coastal area of Futtsu City. The exposure point was set to a berthing distance of 5 m (daily average amount of flying sea salt particles of 1.3 mg / dm ² ). For the evaluation, the average plate thickness reduction amount on one side (front side) of the weld metal part was measured, and 0.2 mm or less was regarded as good.

The wire symbols W1 to W16 in Tables 1 and 4 are examples of the present invention, and the wire symbols W17 to W31 in Tables 2 and 5 are comparative examples. The wire symbols W1 to W16, which are examples of the present invention, are the sum of the steel outer skin and the flux in the flux-cored wire, and the sum of the TIO ₂ conversion values of C, Si, Mn, Cu, Cr, Al, and the Ti oxide in the flux. , Si oxide _{total SiO 2} conversion value, Zr oxide ZrO ₂ conversion value total, Al oxide Al ₂ O ₃ conversion value total, Na oxide, Na fluoride, K oxide and K flux Since the total of Na conversion value and K conversion value of one or more kinds of compounds and the F conversion value of Mg, B, and metal flux are appropriate, the arc is stable and the amount of spatter generated is small, and it stands up. There was no dripping of molten metal in the improved welding, the slag peelability and bead shape were good in each posture welding, and no high-temperature cracking or defects in the X-ray transmission test occurred. In addition, the tensile strength and absorption energy of the weld metal were also good, and the corrosion resistance was also good.

Since an appropriate amount of Ni was added to the wire symbols W2, W4, W10, and W12 to W14, the average plate thickness reduction amount was less than 0.1 mm, which was extremely good in the corrosion resistance test of the weld metal.

Further, since the wire symbols W4, W5, W7, W8, W12, and W13 have an appropriate amount of Ti added, an average absorbed energy of 80 J or more was obtained.

In the comparative example, the wire symbol W17 has a small amount of C, so that the arc becomes unstable and the amount of spatter generated increases. Moreover, since the total of the TIO ₂ conversion values of the Ti oxide was large, the absorbed energy of the weld metal was low.

Since the wire symbol W18 has a large amount of C, the absorbed energy of the weld metal was low. Further, _{since the total value of Si oxides converted to SiO 2} is small, the bead shape is defective. Although Ti was added, the effect of improving the absorbed energy of the weld metal to 70 J or more, which is the target value, could not be obtained.

Since the wire symbol W19 has a small amount of Si, the bead shape is poor. Further, since the total value of the Si oxide in _{terms of SiO 2} is large, the absorbed energy of the weld metal is low.

Since the wire symbol W20 contains a large amount of Si, the absorbed energy of the weld metal was low. Further, since the total of the ZrO ₂ conversion values of the Zr oxide is small, metal sagging occurred in the vertical welding.

Since the wire symbol W21 has a small amount of Mn, the bead shape is poor and the absorbed energy of the weld metal is low. Further, since the amount of Cu is small, the corrosion resistance of the weld metal is poor. Since the amount of Ni is small, the effect of improving the corrosion resistance of the weld metal could not be obtained.

Since the wire symbol W22 has a large amount of Mn, the tensile strength of the weld metal is high and the absorbed energy is low. Further, since the Zr oxide _{has a large ZrO 2} conversion value, the slag peelability was poor.

The wire symbol W23 had a large amount of Cu, so high-temperature cracking occurred in the initial layer of the welded portion, and the absorbed energy of the weld metal was low. In addition, since the Al ₂ O ₃ conversion value of Al oxide is small, molten metal sagging occurred in the vertical welding. Although Ti was added, the effect of improving the absorbed energy of the weld metal to 70 J or more, which is the target value, could not be obtained.

Since the wire symbol W24 has a small amount of Cr, the corrosion resistance of the weld metal is poor. Further, since the total of the TIO ₂ conversion values of the Ti oxide was small, the arc was unstable, the amount of spatter generated was large, the bead shape was poor, and the absorbed energy of the weld metal was low. Further, molten metal sagging occurred in the vertical welding. Although Ni was added, the effect of improving the corrosion resistance of the weld metal could not be obtained.

Since the wire symbol W25 has a large amount of Cr, the tensile strength of the weld metal is high and the absorbed energy is low. Further, since the Al ₂ O ₃ conversion value of the Al oxide is large, slag entrainment occurred. Furthermore, since the sum of the Na-equivalent value and the K-equivalent value of one or more kinds of Na oxide, Na fluoride, K oxide and K fluoride is small, the arc becomes unstable.

Since the wire symbol W26 has a small amount of Al, molten metal sagging occurred in the vertical welding. Moreover, since the amount of Mg was small, the absorbed energy of the weld metal was low. Since the amount of Ti is small, the effect of improving the absorbed energy of the weld metal could not be obtained.

Since the wire symbol W27 contains a large amount of Al, the absorbed energy of the weld metal was low. Further, since the total of one or more Na-equivalent values and K-equivalent values of one or more kinds of Na oxide, Na fluoride, K oxide and K fluoride is large, the amount of spatter generated is large, and the slag peelability and bead shape Became defective.

Since the wire symbol W28 contains a large amount of Mg, the amount of spatter generated is large. Moreover, since the amount of B was small, the absorbed energy of the weld metal was low. Although Ti was added, the effect of improving the absorbed energy of the weld metal to 70 J or more, which is the target value, could not be obtained.

Since the wire symbol W29 has a large amount of B, high-temperature cracking occurred in the initial layer of the welded portion, the tensile strength of the weld metal was high, and the absorbed energy was low. Moreover, since the total F-converted value of the metal fluoride was small, the arc became unstable.

Since the wire symbol W30 has a large total F-converted value of the metal fluoride, the arc becomes unstable and the amount of spatter generated is large, and molten metal sagging occurs in the vertical welding. In addition, slag entrainment occurred. Further, since the amount of Ni was large, the tensile strength of the weld metal was high and the absorbed energy was low.

Since the wire symbol W31 contains a large amount of Mg, the amount of spatter generated is large. Moreover, since the amount of Ti was large, the absorbed energy of the weld metal was low.

Claims (3)

In a flux-cored wire for gas shielded arc welding of seawater-resistant steel, which is made by filling a steel outer skin with flux.
Mass% of total wire mass, total of steel skin and flux,
C: 0.03 to 0.12%,
Si: 0.1 to 1.0%,
Mn: 1.3 to 2.8%,
Cu: 0.01-0.7%,
Cr: 0.5-1.5%,
Al: Containing 0.02 to 0.30%,
In addition, in the flux, in mass% of the total mass of the wire,
Total of TiO ₂ conversion values of Ti oxide: 3.5 to 7.0%,
_{Total SiO 2} conversion value of Si oxide: 0.1-0.6%,
_{Total ZrO 2} conversion value of Zr oxide: 0.1 to 1.0%,
_{Total Al 2} O ₃ conversion value of Al oxide: 0.01 to 0.50%,
Total of one or more Na-equivalent values and K-equivalent values of Na oxide, Na fluoride, K oxide and K fluoride: 0.01 to 0.30%,
Mg: 0.1 to 0.7%,
B: 0.001 to 0.010%,
Total F conversion value of metal fluoride: Contains 0.01-0.15%,
A flux-containing wire for gas shielded arc welding of seawater-resistant steel, wherein the balance is composed of Fe of a steel outer skin, iron powder in a flux, Fe content of iron alloy powder, and unavoidable impurities. The gas shielded arc welding of the seawater resistant steel according to claim 1, which contains 0.02 to 0.50% of Ni: 0.02 to 0.50% in total of the steel outer skin and the flux in mass% with respect to the total mass of the wire. For flux-cored wire. The seawater-resistant steel according to claim 1 or 2, characterized in that it contains Ti: 0.01 to 0.10% in total of the steel outer skin and the flux in% by mass with respect to the total mass of the wire. Flux-filled wire for gas shielded arc welding.