JP7364448B2 - Flux Cored Wire for Gas Shielded Arc Welding for Beach Weathering Steel - Google Patents

Description

The present invention is a flux-cored weathering steel used for steel structures, etc., especially for gas-shielded arc welding for beach weathering steel used for horizontal fillet welding in an environment with a high concentration of airborne salt from the sea. The present invention relates to a flux-cored wire for gas-shielded arc welding for coastal weathering steel, which is suitable for producing a weld metal with a small amount of spatter, a good bead shape during multilayer welding, and excellent strength and toughness.

Corrosion prevention for steel structures used in areas where salt damage occurs, such as coastal areas, includes painting ordinary steel materials, using plated steel materials, forming surface coatings using thermal spraying techniques, and using highly resistant alloys such as stainless steel and titanium alloys. Examples include the use of ingredients and the application of weather-resistant steel materials with adjusted steel plate components without painting.

In the case of painting, there is a problem in that maintenance costs are high because it is necessary to periodically reapply the paint. Furthermore, in the case of plating, there is a problem in that the plating peels off due to deformation of the steel structure due to thermal stress. In the case of thermal spraying, peeling of the anticorrosion coating on the surface and deterioration over time are also problems. Furthermore, high alloy materials have the problem of high material cost and difficulty in being used as major structural members.

When weather-resistant steel is applied unpainted, a dense stable rust layer with excellent anti-corrosion properties forms on the surface of the steel within a few to ten years after the start of use, and this stable rust layer prevents the subsequent corrosion of the steel. To suppress this, it is applied to a wide range of steel structures such as bridges, steel structures, and ships. However, in coastal areas where there is a high concentration of airborne salt from the sea, or areas where snow-melting agents are sprayed in mountainous areas, the formation of a stable rust layer with excellent protection is inhibited by the salt adhering to the surface of the steel plate. There is a problem that it cannot be applied.

For this reason, efforts are being made to develop steel materials that do not require painting or plating for use in areas with high levels of airborne sea salt particles. A steel plate that prevents the destruction of a stable rust layer by having the chemical composition of the steel material contain 1.0 to 5.5% Ni, 0.30 to 1.0% Cu, and no addition of Cr. is being developed.

Flux-cored wires that are applicable to such weather-resistant steel and have good welding workability are disclosed in, for example, Patent Document 1 and Patent Document 2. However, the technology disclosed in Patent Document 1 is of a type that forms a stable rust layer on the steel surface by containing Cu, Cr, and Ni specified in JIS Z3320, and is not suitable for welding in a salt corrosion environment. do not have. In addition, the technology disclosed in Patent Document 2 contains a large amount of TiO ₂ , which is a slag forming agent, so when continuous welding is performed without removing slag in multilayer horizontal fillet welding, the next pass The slag covering the bead surface naturally peels off during welding, and the toe of the bead tends to become uneven.

Further, the technique disclosed in Patent Document 3 does not contain Al and Mg, which have a deoxidizing effect, and therefore has a problem in that the weld metal cannot obtain toughness at low temperatures.

Japanese Patent Application Publication No. 2011-125904 Japanese Patent Application Publication No. 2000-288781 Japanese Patent Application Publication No. 2000-102893

Therefore, the present invention has been devised in view of the above-mentioned problems, and is suitable for welding weathering steel by reducing the amount of spatter generated in horizontal fillet welding and improving the bead shape and bead appearance during multilayer welding. The object of the present invention is to provide a flux-cored wire for gas-shielded arc welding for coastal weathering steel, which has good welding workability such as excellent welding properties.

That is, the gist of the present invention is to provide a flux-cored wire for gas-shielded arc welding for coastal weathering steel in which the steel sheath is filled with flux, and the sum of the steel sheath and flux is C. : 0.01 to 0.09%, Si: 0.1 to 0.7%, Mn: 1.0 to 2.5%, Cu: 0.04 to 0.7%, Ni: 2.0 to 4 .0%, Al: 0.02 to 0.40%, and further, the total TiO ₂ equivalent value of Ti oxide in the flux, expressed as mass % based on the total mass of the wire: 2.0 to 4.0 %, total SiO ₂ equivalent value of Si oxide: 0.1 to 1.0%, total ZrO ₂ equivalent value of Zr oxide: 0.1 to 0.6%, FeO equivalent value of Fe oxide Total: 0.01 to 0.5%, total of Al ₂ O ₃ equivalent value of Al oxide: 0.04 to 0.5%, 1 of Na oxide, Na fluoride, K oxide, and K fluoride Total of Na equivalent value and K equivalent value of species or two or more types: 0.01 to 0.3%, Mg: 0.05 to 0.8%, Total of F equivalent value of metal fluoride: 0.01 to 0.2%, with the remainder consisting of Fe in the steel shell, Fe in the iron powder in the flux, Fe in the iron alloy powder, and unavoidable impurities.

According to the flux-cored wire for gas-shielded arc welding of beach weathering steel to which the present invention is applied, the amount of spatter generated is small in horizontal fillet welding of beach weathering steel, and the bead shape and bead appearance during multilayer welding are improved. It is possible to improve the quality of the welded joint by stably obtaining a weld metal with excellent toughness, especially at low temperatures.

The present inventors have developed a flux-cored wire for gas-shielded arc welding for coastal weathering steel that has low spatter generation in horizontal fillet welding and excellent welding workability in bead shape and bead appearance during multilayer welding. Various studies were conducted to obtain this.

As a result, by adding appropriate amounts of Cu and Ni to the flux and not adding Cr, a method was found to optimize the component balance between the weld metal and base metal components and improve corrosion resistance against flying sea salt particles. I found out.

In addition, by using appropriate amounts of C, Ti oxide, Si oxide, Na oxide, Na fluoride, K oxide, K fluoride, Mg, and metal fluoride, the arc is stabilized and the amount of spatter generated is reduced. , Si, Mn, Al, Ti oxide, Si oxide, Zr oxide, Fe oxide, Al oxide, Na oxide, Na fluoride, K oxide, K fluoride, and metal fluoride in appropriate amounts. It has been found that by doing so, the bead shape can be improved.

Furthermore, it has been found that by setting appropriate amounts of C, Si, Mn, Cu, Ni, and Mg in the flux-cored wire, a weld metal with excellent mechanical performance, particularly toughness at low temperatures, can be stably obtained.

Hereinafter, the composition and content of the flux-cored wire for gas-shielded arc welding for coastal weathering steel of the present invention, and the reasons for limiting the composition of each component will be explained. Note that the composition of each component is expressed in mass % with respect to the total mass of the wire, and when expressing the mass %, it is simply written as %.

[C: 0.01 to 0.09% in total of steel shell and flux]
C has the effect of stabilizing the arc and making the droplet size finer. If C is less than 0.01%, the arc becomes unstable and it becomes difficult to make the droplets fine, resulting in a large amount of spatter. On the other hand, when C exceeds 0.09%, C is excessively present in the weld metal, resulting in a decrease in toughness. Therefore, C is set at 0.01 to 0.09%. In addition to the components contained in the steel shell, C can be added from metal powder, alloy powder, etc. from flux.

[Si: 0.1 to 0.7% in total of steel shell and flux]
A portion of Si becomes welding slag during welding, improves the bead shape, and contributes to improving welding workability. If Si is less than 0.1%, the weld bead shape will be poor. On the other hand, if Si exceeds 0.7%, Si will be excessively present in the weld metal and the toughness will decrease. Therefore, Si is set at 0.1 to 0.7%. In addition to the components contained in the steel outer skin, Si can be added from metal Si from flux, alloy powder such as Fe-Si, Fe-Si-Mn, and the like.

[Mn: 1.0 to 2.5% in total of steel shell and flux]
Like Si, a portion of Mn becomes welding slag during welding, improves the bead shape, contributes to improving welding workability, and acts as a deoxidizing agent, which has the effect of improving the low-temperature toughness of the weld metal. When Mn is less than 1.0%, Mn is not sufficiently retained in the weld metal, resulting in a decrease in low-temperature toughness of the weld metal and poor bead shape. On the other hand, when Mn exceeds 2.5%, Mn remains excessively in the weld metal, resulting in excessive strength and decreased toughness. Therefore, Mn is set to 1.0 to 2.5%. In addition to the components contained in the steel outer skin, Mn is added from metal Mn from flux, alloy powder such as Fe--Mn, Fe--Si--Mn, and the like.

[Cu: 0.04 to 0.7% in total of steel shell and flux]
Cu is an essential element for suppressing crystallization and coarsening of rust particles during rust layer formation and maintaining the density of the rust layer. If Cu is less than 0.04 %, this effect cannot be sufficiently obtained, and the corrosion resistance of the weld metal decreases. On the other hand, when Cu exceeds 0.7%, hot cracking tends to occur and the toughness of the weld metal decreases. Therefore, Cu is set at 0.04 to 0.7%. In addition to the components contained in the steel outer shell, Cu can be added from Cu plating on the wire surface, metal Cu from flux, and alloy powder such as Fe-Cu.

[Ni: 2.0 to 4.0% in total of steel shell and flux]
Ni is the most important element for improving corrosion resistance in environments with high concentrations of airborne sea salt particles. It has the effect of suppressing concentration increase. Therefore, the crystallization and coarsening of the rust layer formed on the surface of the steel sheet can be suppressed, the crystallization of the rust layer can be maintained, and the corrosion resistance in an environment of flying sea salt particles can be improved. If Ni is less than 2.0%, this effect cannot be sufficiently obtained, and the corrosion resistance of the weld metal decreases. On the other hand, when Ni exceeds 4.0%, corrosion resistance becomes saturated and hot cracking is likely to occur in the weld metal part. Moreover, when Ni exceeds 4.0%, the strength of the weld metal becomes too high and the toughness decreases. Therefore, Ni is set at 2.0 to 4.0%. In addition to the components contained in the steel outer skin, Ni can be added from metal Ni from flux, alloy powder such as Fe-Ni, Ni-Mg, etc.

[Al: 0.02 to 0.40% in total of steel shell and flux]
Al acts as a deoxidizing agent and becomes Al oxide during melting, increasing the viscosity of the slag, which has the effect of suppressing the retreat of the molten pool during horizontal fillet welding and maintaining sufficient slag envelopment. . However, if the Al content is less than 0.02%, this effect cannot be sufficiently obtained, and the bead becomes convex, resulting in undercuts and slag burning in the upper leg. On the other hand, when Al exceeds 0.40%, the bead shape loses its smoothness and the toe becomes swollen. Moreover, if Al exceeds 0.40%, uneven solidification of the molten slag will occur, resulting in poor slag removability. Therefore, Al should be 0.02 to 0.40%. In addition to the components contained in the steel outer skin, Al can be added from metal Al from flux, alloy powder such as Fe-Al, Al-Mg, etc.

[Total TiO ₂ equivalent value of Ti oxide in flux: 2.0 to 4.0%]
Ti oxide contributes to arc stabilization during welding and has the effect of forming welding slag to uniformly cover the entire weld bead. Further, Ti oxide has the effect of contributing to improving welding workability by sustaining and stabilizing the arc and reducing the amount of spatter generated. If the total TiO ₂ equivalent value of the Ti oxide is less than 2.0%, these effects cannot be sufficiently obtained, the arc becomes unstable, a large amount of spatter is generated, and the bead shape deteriorates. On the other hand, if the total TiO ₂ equivalent value of Ti oxide exceeds 4.0%, the arc becomes stable and the amount of spatter generated decreases, but the amount of slag increases and the slag becomes easy to peel off naturally, so slag removal Bead shape deteriorates during multi-layer welding without this. Therefore, the total TiO ₂ equivalent value of Ti oxide is 2.0 to 4.0%. Note that Ti oxide is added from rutile sand from flux, titanium oxide, titanium slag, illuminite, and the like.

[Total SiO ₂ equivalent value of Si oxide in flux: 0.1 to 1.0%]
Si oxide has the effect of adjusting the viscosity and melting point of the molten slag and improving the slag encapsulation properties. If the total SiO ₂ equivalent value of the Si oxide is less than 0.1%, this effect will not be sufficiently obtained and the bead shape will be poor. On the other hand, if the total SiO ₂ equivalent value of Si oxide exceeds 1.0%, the amount of spatter will increase, and the bead toe (lower plate side) will swell, resulting in poor bead shape and bead appearance. . Therefore, the SiO ₂ equivalent value of Si oxide is set to 0.1 to 1.0%. Note that Si oxide can be added from silica sand from flux, potassium feldspar, sodium silicate, zircon sand, and the like.

[Total ZrO ₂ equivalent value of Zr oxides in flux: 0.1 to 0.6%]
Zr oxide has the effect of adjusting the viscosity and melting point of the molten slag, improving the slag encapsulation properties, and smoothing the bead shape. If the total ZrO ₂ equivalent value of Zr oxide is less than 0.1%, this effect will not be sufficiently obtained and the bead shape will be poor. On the other hand, if the total ZrO ₂ equivalent value of the Zr oxide exceeds 0.6%, the bead shape will not be smooth and will become convex, and the slag removability will be poor. Therefore, the total ZrO ₂ equivalent value of Zr oxide is 0.1 to 0.6%. Note that Zr oxide can be added from zirconium oxide from flux, zircon sand, etc., and is contained in a small amount in Ti oxide.

[FeO equivalent value of Fe oxide: 0.01 to 0.5%]
Fe oxides such as FeO and Fe ₂ O ₃ adjust the viscosity and solidification temperature of the molten slag, eliminate swelling at the bead toe, and improve compatibility with the lower plate. If the FeO equivalent value of the Fe oxide is less than 0.01%, the shape of the bead toe becomes poor. On the other hand, if the FeO equivalent value of the Fe oxide exceeds 0.5%, the slag encapsulation condition deteriorates, the slag removability is poor, the bead toe bulges, and the bead shape and bead appearance are also poor. Therefore, the FeO equivalent value of Fe oxide is set to 0.01 to 0.5%. Note that Fe oxide can be added from iron oxide from flux, mill scale, etc., and is also contained in a trace amount in Ti oxide.

[Total Al ₂ O ₃ equivalent value of Al oxides in flux: 0.04 to 0.5%]
As a slag forming agent, Al oxide has the effect of improving slag encapsulation properties and improving bead shape and slag removability. If the total Al ₂ O ₃ equivalent value of the Al oxide is less than 0.04 %, this effect will not be sufficiently obtained, the slag encapsulation will be poor, and the bead shape and slag releasability will also be poor. On the other hand, if the total Al ₂ O ₃ equivalent value of Al oxide exceeds 0.5%, slag envelopment becomes uneven, slag encapsulability deteriorates, and bead shape and slag removability become poor. Therefore, the total Al ₂ O ₃ equivalent value of Al oxide is 0.04 to 0.5%. Note that Al oxide is added from alumina from flux, potassium feldspar, and the like.

[Total Na equivalent value and K equivalent value of one or more types of Na oxide, Na fluoride, K oxide, and K fluoride in flux: 0.01 to 0.3%]
Na oxide, Na fluoride, K oxide, and K fluoride have the effect of stabilizing the arc, and as slag forming agents, they suppress the rapid increase in viscosity during the solidification process of molten slag and create a smooth bead shape. It has the effect of If the sum of the Na-equivalent value and the K-equivalent value of Na oxide, Na fluoride, K oxide, and K fluoride is less than 0.01%, the effect will not be sufficiently obtained and the arc will become unstable. On the other hand, if the sum of the Na and K equivalent values of Na oxide, Na fluoride, K oxide, and K fluoride exceeds 0.3%, slag removability, bead shape, and bead appearance will be poor, resulting in sputtering. The amount generated increases. Therefore, the total of the Na equivalent value and K equivalent value of one or more of Na oxide, Na fluoride, K oxide, and K fluoride is 0.01 to 0.3%. Note that Na oxide, Na fluoride, K oxide, and K fluoride are added from sodium silicate, solid content of water glass consisting of potassium silicate, potassium feldspar from flux, NaF, KF, K ₂ SiF ₆ , etc. The Na conversion value and K conversion value are the sum of the amounts of Na and K contained in these.

[Mg in flux: 0.02-0.4%]
Mg is a strong deoxidizing agent and has the effect of reducing oxygen in the weld metal and increasing the toughness of the weld metal. If Mg is less than 0.02%, this effect cannot be sufficiently obtained and the toughness of the weld metal decreases. On the other hand, if Mg exceeds 0.4%, it will react violently with oxygen in the arc during welding, resulting in a large amount of spatter, resulting in poor welding workability. Therefore, Mg is set at 0.02 to 0.4%. Note that Mg is added from metal Mg from flux and alloy powder such as Al-Mg.

[Total F equivalent value of metal fluorides in flux: 0.01 to 0.2%]
The metal fluoride has the effect of increasing the directivity of the arc to form a stable molten pool and adjusting the viscosity of the slag. If the total F equivalent value of the metal fluoride is less than 0.01%, this effect will not be sufficiently obtained and the arc will become unstable. On the other hand, if the total F-equivalent value of metal fluorides exceeds 0.2%, the arc becomes unstable and a large amount of spatter occurs. If the total F equivalent value of metal fluoride exceeds 0.2%, the viscosity of the slag decreases and a thin slag that is difficult to remove remains on the upper leg of the bead, resulting in poor slag removability and a convex bead shape. It becomes like this. Therefore, the total F equivalent value of metal fluorides is set to 0.01 to 0.2%. Note that the metal fluoride can be added from flux such as CaF ₂ , NaF, KF, LiF, MgF ₂ , K ₂ SiF ₆ , AlF ₃ , etc., and the F conversion value is the total amount of F contained in these.

The flux-cored wire for gas-shielded arc welding for coastal weather-resistant steel according to the present invention has a structure in which a steel outer sheath is formed into a pipe shape, and the inside thereof is filled with flux. There are two types of wire: wires with no seams on the steel sheath obtained by welding the joints of formed steel sheaths, and wires with no seams on the steel sheath where the joints of the steel sheaths are left unwelded. It can be broadly divided into wires with wires. In the present invention, wires having any cross-sectional structure may be employed. However, wires with a seamless steel sheath can be annealed to reduce the amount of moisture in the wire, and since the flux does not absorb moisture after manufacturing, it reduces the amount of diffusible hydrogen in the weld metal. However, since it is possible to improve cold cracking resistance, it is preferable to use a wire with no seams in the steel outer sheath.

The remainder of the flux-cored wire for gas-shielded arc welding for coastal weather-resistant steel of the present invention includes Fe in the steel sheath, Fe in the iron powder added from the flux for component adjustment, Fe-Mn, Fe-Si alloy, etc. These are the Fe content and unavoidable impurities in the iron alloy powder. In addition, although there is no particular restriction, the flux filling rate should be 8 to 20% with respect to the total mass of the wire from the viewpoint of productivity, and Mo: 0.1% for Mo, V, and Nb from the viewpoint of strength of mechanical performance. Hereinafter, it is preferable that V: 0.05% or less and Nb: 0.05% or less.

Hereinafter, the effects of the present invention will be specifically explained using examples.

First, JIS G3141 SPCC (C: 0.002 to 0.06% by mass) is used for the steel shell, the steel shell is formed into a U-shape, and flux is filled at a filling rate of 8 to 20% to form the C. After forming into a shape, the joints of the steel outer skin were welded, pipes were made, and wire drawing was carried out to fabricate prototype flux-cored wires with various components shown in Tables 1 and 2. Note that the diameter of the prototype wire was 1.2 mm.

Using these prototype wires, welding workability in horizontal fillet welding was investigated.

Welding workability was measured by performing multi-layer horizontal fillet welding on a test specimen made of 20 mm thick coastal weathering steel plates assembled in a T-shape under the welding conditions shown in Table 3, and examining the arc condition and spatter generation at that time. The condition, slag encapsulation, slag removability, bead appearance shape, and slag condition during multilayer welding were visually inspected.

For the weld metal test, a 20 mm thick seaside weathering steel plate was welded according to JIS Z 3111, and a tensile test piece (No. A0) and an impact test piece (2 mm V notch) were placed from the center of the weld metal in the thickness direction. A mechanical test was conducted by taking a test piece. In the tensile test evaluation, a tensile strength of 550 to 650 MPa was considered good. For the evaluation of the impact test, a Charpy impact test was performed at -20°C, and an average of 3 repeated absorption energies of 65 J or more was considered good. At that time, the presence or absence of hot cracking during first layer welding was visually confirmed. These results are summarized in Tables 4 and 5.

For the weather resistance (corrosion resistance) test, the surplus was ground from the test piece used for the weld metal test, and the test piece was made into a strip with a thickness of 20 mm, a width of 100 mm, and a length of 200 mm with the weld bead in the longitudinal direction. An exposure test was conducted for three years in the waterfront area of Futtsu City, Chiba Prefecture. The exposure point was set at a distance of 5 m from shore (the daily average amount of airborne sea salt particles was 1.3 mg/dm ² ). For evaluation, the average plate thickness reduction amount on one side (front side) of the welded metal part was measured, and 0.2 mm or less was considered good.

Wire symbols W1 to W12 in Tables 1 and 4 are examples of the present invention, and wire symbols W13 to W28 in Tables 2 and 5 are comparative examples. Wire symbols W1 to W12, which are examples of the present invention, are the sum of the steel outer shell and flux in the flux-cored wire, and the sum of C, Si, Mn, Cu, Ni, Al, and the TiO ₂ equivalent value of Ti oxide in the flux. , the sum of the SiO ₂ equivalent values of Si oxides, the sum of ZrO ₂ equivalent values of Zr oxides, the total FeO equivalent values of Fe oxides, the sum of Al ₂ O ₃ equivalent values of Al oxides, Na oxide, Since the sum of the Na and K equivalent values of Na fluoride, K oxide, and K fluoride, and the sum of the F equivalent values of Mg and metal fluoride are appropriate, the arc is stable and the amount of spatter generated is small. The slag envelopment, slag removability, bead shape and appearance were good, and no hot cracking occurred. Moreover, the tensile strength and absorbed energy of the weld metal were good, and the corrosion resistance was also good.

Wire symbol W13 in the comparative example had a small amount of C, so the arc became unstable and a large amount of spatter was generated. Furthermore, since the total amount of Al ₂ O ₃ equivalent values of Al oxides was large, uneven slag envelopment occurred, and the bead shape and slag releasability were poor.

Wire symbol W14 contained a large amount of C, so the energy absorbed by the weld metal was low. Furthermore, since the total F equivalent value of the metal fluoride was large, the arc became unstable, a large amount of spatter was generated, and the bead shape and slag removability were poor.

Wire symbol W15 had a poor bead shape because it contained less Si. Further, since the sum of Na-equivalent values and K-equivalent values of Na oxide, Na fluoride, K oxide, and K fluoride was small, the arc state was unstable.

Wire symbol W16 contained a large amount of Si, so the absorbed energy of the weld metal was low. Furthermore, since the total TiO ₂ equivalent value of Ti oxide was small, the arc condition was unstable, the amount of spatter generated was large, and the bead shape was poor.

Wire symbol W17 had a low Mn content, so the absorbed energy of the weld metal was low and the bead shape was poor. In addition, since the total amount of TiO ₂ equivalent of Ti oxide was large, slag peeled off during multilayer welding, resulting in poor bead shape.

Wire symbol W18 contained a large amount of Mn, so the tensile strength of the weld metal was high and the absorbed energy was low. Furthermore, since the total amount of SiO ₂ equivalents of Si oxide was large, the amount of spatter generated was large and the bead shape was poor.

Wire symbol W19 had a low Cu content, so the weld metal had poor corrosion resistance.

Wire code W20 contained a large amount of Cu, so hot cracking occurred in the initial layer of the weld zone, and the absorbed energy of the weld metal was also low. In addition, since the total Na oxide and K fluoride values of Na oxide, Na fluoride, K oxide, and K fluoride are large, the amount of spatter generated is large, and the slag removability, bead shape, and bead appearance are poor. Ta.

Wire symbol W21 had a low Ni content, so the corrosion resistance of the weld metal was poor. Furthermore, since the Al content was small, the slag encapsulation properties and bead shape were poor.

Wire code W22 contained a lot of Ni, so hot cracking occurred in the initial layer of the weld, the tensile strength of the weld metal was high, and the absorbed energy was low. Furthermore, since the total ZrO ₂ equivalent value of Zr oxide was small, the bead shape was poor.

Wire symbol W23 contained a large amount of Al, so the bead shape and slag removability were poor. In addition, since there was little Mg, the absorbed energy of the weld metal was low.

Wire symbol W24 had a large total FeO equivalent value of Fe oxide, and therefore had poor slag envelopment properties, slag removability, and bead shape.

Wire symbol W25 had a poor bead shape because the total SiO ₂ equivalent value of Si oxide was small.

Wire symbol W26 had a large total ZrO ₂ equivalent value of Zr oxide, so the bead shape and slag removability were poor. Furthermore, since the total F conversion value of metal fluorides was small, the arc state was unstable.

Wire symbol W27 had a poor bead shape because the total FeO equivalent value of Fe oxide was small. Furthermore, since there was a large amount of Mg, a large amount of spatter was generated.

Wire code W28 had poor slag encapsulation, slag removability, and bead shape because the total amount of Al ₂ O ₃ equivalent value of Al oxide was small.

Claims (1)

Flux-cored wire for gas-shielded arc welding for coastal weathering steel is made by filling a steel sheath with flux.
Mass % based on the total mass of the wire, the sum of the steel jacket and flux,
C: 0.01-0.09%,
Si: 0.1 to 0.7%,
Mn: 1.0 to 2.5%,
Cu: 0.04 to 0.7%,
Ni: 2.0 to 4.0%,
Contains Al: 0.02 to 0.40%,
Furthermore, in flux, in mass % relative to the total mass of the wire,
Total TiO ₂ equivalent value of Ti oxide: 2.0 to 4.0%,
Total SiO ₂ equivalent value of Si oxide: 0.1 to 1.0%,
Total ZrO ₂ equivalent value of Zr oxide: 0.1 to 0.6%,
Total FeO equivalent value of Fe oxide: 0.01 to 0.5%,
Total Al ₂ O ₃ equivalent value of Al oxide: 0.04 to 0.5%,
Total of Na equivalent value and K equivalent value of one or more types of Na oxide, Na fluoride, K oxide, and K fluoride: 0.01 to 0.3%,
Mg: 0.02-0.4%,
Contains a total F equivalent value of metal fluorides: 0.01 to 0.2%,
A flux-cored wire for gas-shielded arc welding for coastal weathering steel, characterized in that the remainder consists of Fe in the steel sheath, Fe in the iron powder in the flux, Fe in the iron alloy powder, and unavoidable impurities.