JP7244337B2 - Flux-cored wire for electrogas arc welding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flux-cored wire for electrogas arc welding, and more particularly to a flux-cored wire for electrogas arc welding that produces a stable arc, generates less spatter, and provides a weld metal with excellent mechanical performance.

Electrogas arc welding is applied in a wide range of fields, such as ships, oil storage tanks, and bridges, because it can perform vertical welding with high efficiency.

An outline of electrogas arc welding is shown in FIGS. 1 and 2. FIG. FIG. 1 is a schematic diagram of a welding method, and FIG. 2 is a diagram showing a groove shape of a steel plate. A groove 10 is formed between two adjacent steel plates 1 erected vertically. A fixed backing material 8 is in contact with the back side of the groove 10, and a sliding copper contact 11 is applied on the front side. A welding torch 4 is inserted into the space. Then, the welding wire 3 is continuously supplied to the space through the welding torch 4 while supplying the shielding gas from the gas supply nozzle 5 of the sliding copper contact 11 . The sliding copper contact 11 and the welding torch 4 mounted on a welding carriage (not shown) are sequentially raised in accordance with the upper surface of the weld metal 6 which is raised as the welding progresses. As shown in the figure, the upper part of the weld metal 6 is the molten metal 12, and between the two steel plates 1, a root gap 2 is formed on the back surface of the groove 10, which cools the sliding copper contact 11. A cooling water supply nozzle 7 is provided.

Electro gas arc welding can perform vertical upward welding with high efficiency, but on the other hand, since the arc is maintained on the molten metal 12, when a large amount of molten slag is generated on the molten metal, the arc becomes unstable, and the molten slag Slag scatters (hereinafter referred to as slag splash), and slag may adhere to the groove surface, torch, and shield gas outlet, causing problems.

Against this background, electrogas arc welding is required to suppress slag splashing, and since it is a welding with a large heat input, it is required to improve the mechanical performance of the weld metal, especially toughness at low temperatures.

As a technique for obtaining low-temperature toughness of the weld metal by electrogas arc welding, Patent Document 1 discloses a technique of using a flux-cored wire for welding and using the groove of the steel plate as an X groove to reduce the welding heat input by welding two layers from both sides. There is a disclosure of However, when one-pass welding is performed with a large heat input using the flux-cored wire for welding described in Patent Document 1, the low-temperature toughness of the weld metal cannot be obtained, and the arc is unstable during welding, resulting in spatter generation. There was a problem that the amount and slag splash increased.

In addition, as a technique for obtaining low-temperature toughness of weld metal in one-pass welding with a large heat input in electrogas arc welding, Patent Documents 2 and 3 disclose welding fluxes containing Ni, Mo, Ti, B, Mg, etc. There is a disclosure of a technique for welding steel plates with a thickness of 60 to 70 mm using wires. However, in the techniques described in Patent Documents 2 and 3, although the toughness of the weld metal can be obtained, there is a problem that the arc is unstable during welding, resulting in increased spatter generation and slag splashing.

Furthermore, as a technique for obtaining good welding workability and toughness of the weld metal in one-pass welding with a large heat input in electrogas arc welding, Patent Document 4 discloses Ni, Mo (Cr), and Ti in a flux-cored wire for welding. , B, Mg, F, K, etc. are disclosed. However, even with the technique described in Patent Document 4, the arc is unstable during welding, resulting in a large amount of spatter and slag splashing, and the low temperature toughness of the weld metal is insufficient.

JP-A-4-279295 JP-A-9-285891 JP 2009-82947 A JP 2008-126262 A

Therefore, the present invention has been devised in view of the above-mentioned problems, and is a weld metal that has good welding workability such as stable arc and excellent low-temperature toughness in one-pass welding of thick steel plates with a large heat input. It is an object of the present invention to provide a flux-cored wire for electrogas arc welding that provides a

The gist of the present invention is a flux-cored wire for electrogas arc welding in which a steel sheath is filled with flux, wherein C is 0.005 to 0.005 as the total of the steel sheath and flux in mass % with respect to the total mass of the wire. 05%, Si: 0.3-1.1%, Mn: 1.8-3.3%, Mo: 0.2-0.8%, Ti: 0.05-0.22%, B: 0 .004 to 0.020%, Al: 0.01% or less, and one or more metal carbonates in the flux in terms of mass% relative to the total mass _of the wire. total of: 0.2 to 0.5%, total of one or more metal oxides: 0.1 to 0.4%, total F conversion value of metal fluorides: 0.05 to 0.5% 40%, total of Na and K conversion values of Na compounds and K compounds: 0.05 to 0.40%, Fe content in iron powder and Fe content in iron alloy: 15 to 25% A flux-cored wire for electrogas arc welding characterized in that the remainder is composed of the Fe content of the steel sheath and unavoidable impurities.

According to the flux-cored wire for electrogas arc welding of the present invention, in high heat input single-pass welding of thick steel plates, the arc is stable, the amount of spatter generation and slag splashing is small, and the bead appearance is good. Welding workability is improved. A good weld metal with excellent low-temperature toughness can be obtained, and a high-quality weld can be provided with high efficiency.

It is a schematic diagram of the welding method of electrogas arc welding. It is a figure which shows the groove shape of a steel plate.

The present inventors have developed a flux-cored wire for electrogas arc welding that has a stable arc, less spatter generation and less slag bounce, and excellent mechanical performance of the weld metal in electrogas arc welding in one-pass welding with a large heat input of thick steel plates. The component composition of was examined in detail.

As a result, the stability of the arc is C, the sum of _CO2 conversion values of metal carbonates, the sum of F conversion values of metal fluorides, the sum of Na conversion values and K conversion values of Na compounds and K compounds, and iron powder It becomes favorable by adjusting the total amount of Fe content in the inner layer and the Fe content in the iron alloy to an appropriate amount. In addition, the prevention of slag splashing can be achieved by adjusting the sum of the _CO2 equivalent values of metal carbonates, the sum of metal oxides, the Fe content in the iron powder, and the sum of the Fe content in the iron alloy. Found it. The bead appearance is improved by adjusting the total amount of the metal oxides and the total of the F-converted values of the metal fluorides to an appropriate amount.

As for the mechanical performance of the weld metal, it was found that a weld metal having excellent strength and low-temperature toughness can be obtained by setting appropriate amounts of C, Si, Mn, Mo, Ti and B and reducing Al.

Hereinafter, the component composition and content of the flux-cored wire for electrogas arc welding of the present invention, and the reasons for limiting each component composition will be described. In addition, the content of the component composition is represented by mass %, and when representing the mass %, it is simply described as %.

[Total C of steel skin and flux: 0.005 to 0.05%]
C secures the strength of the weld metal. If C is less than 0.005%, sufficient weld metal strength cannot be obtained. On the other hand, if C exceeds 0.05%, the arc becomes unstable and the amount of spatter generation increases. Therefore, the total content of C in the steel skin and flux should be 0.005 to 0.05%. C can be added from iron powder, metal powder, alloy powder, etc. from flux, in addition to components contained in the steel outer sheath.

[Si: 0.3 to 1.1% in total of steel skin and flux]
Si acts as a deoxidizing agent and has the effect of improving the low temperature toughness of the weld metal. If the Si content is less than 0.3%, the effect cannot be obtained, and the low temperature toughness of the weld metal deteriorates. On the other hand, when Si exceeds 1.1%, the yield of Si is excessive in the weld metal, the strength of the weld metal increases, and the low temperature toughness decreases. Therefore, the total Si content of the steel sheath and the flux should be 0.3 to 1.1%. Si can be added from metal Si, Fe--Si, Fe--Si--Mn, and other alloy powders from the flux, in addition to the components contained in the steel outer shell.

[Total Mn of steel skin and flux: 1.8 to 3.3%]
Mn acts as a deoxidizing agent and has the effect of improving the strength and low temperature toughness of the weld metal. If the Mn content is less than 1.8%, the low temperature toughness of the weld metal is lowered and sufficient strength cannot be obtained. On the other hand, when Mn exceeds 3.3%, the strength of the weld metal increases and the low temperature toughness decreases. Therefore, the total Mn of the steel sheath and flux should be 1.8 to 3.3%. Mn can be added from metal Mn, Fe--Mn, Fe--Si--Mn, or other alloy powder from flux, in addition to components contained in the steel outer sheath.

[Total Mo of steel skin and flux: 0.2 to 0.8%]
Mo improves the strength of the weld metal. If Mo is less than 0.2%, the effect of improving the strength of the weld metal cannot be obtained. On the other hand, when Mo exceeds 0.8%, the strength excessively increases and the toughness decreases. Therefore, Mo is set to 0.2 to 0.8% in total in the steel outer sheath and flux. Mo can be added from metal Mo, alloy powder such as Fe—Mo, etc. from flux, in addition to components contained in the steel outer shell.

[Ti: 0.05 to 0.22% in total of steel skin and flux]
Ti acts as a deoxidizing agent, and the produced Ti-containing oxide has the effect of refining the structure of the weld metal and improving the low-temperature toughness. If the Ti content is less than 0.05%, the effect of improving the low temperature toughness of the weld metal cannot be obtained. On the other hand, if Ti exceeds 0.22%, an upper bainite structure that impedes toughness is generated, and the low temperature toughness of the weld metal is lowered. Therefore, Ti is set to 0.05 to 0.22% in total of the steel outer covering and the flux. In addition, Ti can be added from metal Ti from flux, alloy powder such as Fe—Ti, etc., in addition to components contained in the steel outer sheath.

[Total B of steel skin and flux: 0.004 to 0.020%]
B has the effect of refining the structure of the weld metal and improving the low temperature toughness when added in a very small amount. If B is less than 0.004%, the effect is not sufficiently obtained, and the low temperature toughness of the weld metal deteriorates. On the other hand, if B exceeds 0.020%, the strength of the weld metal increases and the toughness decreases. Therefore, B is set to 0.004 to 0.020% in total of the steel skin and the flux. B can be added from metal B from flux, alloy powder such as Fe-B, Fe-Mn-B, etc., in addition to components contained in the steel outer sheath.

[Al: 0.01% or less in total of steel skin and flux]
A small amount of Al is contained in the steel sheath and the iron alloy. If the Al content exceeds 0.01%, it is oxidized during welding to form Al ₂ O ₃ , which is retained in the weld metal and reduces toughness. Therefore, Al should be 0.01% or less. Note that Al is not an essential element, and the content may be 0%.

[Total CO ₂ conversion value of one or more metal carbonates in flux: 0.2 to 0.5%]
Metal carbonate decomposes during welding to generate CO ₂ gas to stabilize the arc. In addition, the generated gas assists the shielding gas to prevent defects due to lack of shielding in places where the work environment is bad, such as outdoors, and to prevent deterioration of toughness due to nitrogen contamination. If the sum of the CO ₂ conversion values of one or more metal carbonates is less than 0.2%, the effect is not sufficiently obtained, the arc becomes unstable, and the amount of spatter generation increases. In addition, insufficient shielding tends to reduce the toughness of the weld metal. On the other hand, if the sum of the CO ₂ conversion values of one or more of the metal carbonates exceeds 0.5%, the metal oxides generated by the decomposition of the metal carbonates increase and the frequency of slag splashing increases. . Therefore, the sum of the CO ₂ conversion values of one or more metal carbonates should be 0.2 to 0.5%. In addition, _CaCO3 , _BaCO3 , _MgCO3 , _{Li2CO3 , K2CO3, Na2CO3 etc. can be} used _for metal carbonate.

[Total of one or more metal oxides in flux: 0.1 to 0.4%]
Metal oxides condition the molten slag for good bead appearance. If the total amount of one or more of the metal oxides is less than 0.1%, the amount of slag will be insufficient and the bead appearance will be poor. On the other hand, if the total amount of one or more metal oxides exceeds 0.4%, the amount of slag in the molten pool becomes excessive and the frequency of slag splashing increases. Therefore, the total content of one or more metal oxides should be 0.1 to 0.4%. In addition, _SiO2 , _Al2O3 , _ZrO2 , _Na2O , _K2O , _{TiO2 etc.} can be used for a metal oxide.

[Total F conversion value of metal fluoride in flux: 0.05 to 0.40%]
A metal fluoride stabilizes the arc and reduces the amount of spatter. If the total F-equivalent value of the metal fluorides is less than 0.05%, this effect cannot be obtained and the arc becomes unstable, resulting in a large amount of spatter. On the other hand, if the total F-equivalent value of the metal fluoride exceeds 0.40%, the fluidity of the slag becomes excessive and the slag tends to sag, making it impossible to obtain a good bead. Therefore, the F conversion value of the metal fluoride should be 0.05 to 0.40%. The metal fluoride can be added from CaF ₂ , NaF, LiF, MgF ₂ , K ₂ SiF ₆ , Na ₃ AlF ₆ , AlF ₃ and the like, and the F conversion value is the total amount of F contained in these.

[Total of Na conversion value and K conversion value of Na compound and K compound in flux: 0.05 to 0.40%]
The Na compound and K compound stabilize the arc and reduce the amount of spatter generation. If the sum of the Na-converted value and the K-converted value of the Na compound and K compound is less than 0.05%, this effect cannot be obtained, the arc becomes unstable, and the amount of spatter generation increases. On the other hand, when the sum of the Na-converted value and the K-converted value of the Na compound and the K compound exceeds 0.40%, the amount of slag generated increases and the frequency of slag splashing increases. Therefore, the sum of Na-converted values and K-converted values of Na compounds and K compounds should be 0.05 to 0.40%. The Na compound and K compound can be added from oxides such as Na ₂ O and K ₂ O, and metal fluorides such as NaF, K ₂ SiF ₆ and Na ₃ AlF ₆ , and the Na conversion value and K conversion value are based on these. It is the total of Na conversion value and K conversion value contained.

[Total Fe content in iron powder and Fe content in iron alloy in flux: 15 to 25%]
The Fe content in the iron powder and the Fe content in the iron alloy make the droplets finer and stabilize the arc. In addition, there is an effect of increasing the welding amount of the welding wire and improving the welding efficiency. If the sum of the Fe content in the iron powder and the Fe content in the iron alloy is less than 15%, the arc will be unstable and the amount of spatter will increase. On the other hand, if the sum of the Fe content in the iron powder and the Fe content in the iron alloy exceeds 25%, the filling rate of the flux increases, making wire drawing difficult during wire production. Therefore, the total Fe content in the iron powder and the Fe content in the iron alloy should be 15 to 25%.

The remainder of the flux-cored wire for electrogas arc welding of the present invention is Fe and unavoidable impurities in the steel sheath. Although the inevitable impurities are not particularly limited, P is preferably 0.020% or less and S is preferably 0.010% or less from the viewpoint of hot crack resistance.

The flux-cored wire for electrogas arc welding of the present invention has a structure in which the steel outer sheath is formed into a pipe shape and the interior is filled with flux. It can be broadly classified into a type having seams in which seams of the steel outer skin are crimped without welding, and both are applicable in the present invention.

Although the flux filling rate is not particularly limited, it is preferably 15 to 30% with respect to the total mass of the wire from the viewpoint of productivity.

EXAMPLES Hereinafter, the effects of the present invention will be described in more detail with reference to examples.

Using JIS G3141 SPCC as the steel skin, the steel skin is molded into a U shape, filled with flux at a filling rate of 15 to 30%, molded into a C shape, and then caulked at the seams of the steel skin. , and wire drawing, and trial production of flux-cored wires for welding with various components shown in Table 1 was made. The wire diameter of the prototype was 1.6 mm.

Using the 490 MPa class high-tensile steel (plate thickness 50 mm) shown in Table 2, electrogas arc welding shown in FIGS. was welded in one pass with a welding length of 500 mm under the welding conditions shown in Table 3.

The stability of the arc, the amount of spatter generated, the frequency of slag bouncing, and the bead appearance during each test were observed. In addition, a tensile test (JIS Z 2201 No. A2) and an impact test (JIS Z 2202 No. 4) were sampled from the central portion of the plate thickness of each test plate, and a mechanical test was performed. A tensile strength of 510 to 690 MPa in the mechanical test and an absorbed energy of 50 J or more (average of 5 pieces) at -20°C in the impact test were considered good. Those results are shown in Table 4.

In Tables 1 and 4, wire symbols W1 to W10 are examples of the present invention, and wire symbols W11 to W23 are comparative examples. Wire symbols W1 to W10, which are examples of the present invention, are one of C, Si, Mn, Mo, Ti, B, Al, the sum of CO ₂ conversion values of one or more of metal carbonates, and one of metal oxides. Or the sum of two or more, the sum of F conversion values of metal fluorides, the sum of Na conversion values and K conversion values of Na compounds and K compounds, the sum of Fe content in iron powder and Fe content in iron alloys. Therefore, the arc was stable, the amount of spatter generated was small, the frequency of slag splashing was low, the bead appearance was good, and both the tensile strength and the absorbed energy of the weld metal were good, and the results were extremely satisfactory.

Wire symbol W11 among the comparative examples had a low tensile strength of the weld metal because C was small. In addition, since the total CO ₂ conversion value of one or more of the metal carbonates was small, the arc was unstable and the absorbed energy of the weld metal was low.

Wire symbol W12 had a large amount of C, so the arc was unstable and a large amount of spatter was generated. In addition, the toughness of the weld metal was low due to the large amount of Al.

With wire symbol W13, the toughness of the weld metal was low due to the low Si content. In addition, since the sum of the CO ₂ conversion values of one or more metal carbonates was large, the amount of molten slag increased and the frequency of slag splashing was high.

Wire symbol W14 had a large amount of Si, so the tensile strength of the weld metal was high and the absorbed energy was low. Moreover, since the total amount of one or more metal oxides was small, the bead appearance was poor.

Wire symbol W15 had a low Mn content, so the tensile strength of the weld metal was low and the absorbed energy was also low. In addition, the frequency of slag splattering was high because the total amount of one or more metal oxides was high.

Wire symbol W16 had a large amount of Mn, so the tensile strength of the weld metal was high and the absorbed energy was low. In addition, since the total F conversion value of metal fluorides was small, the arc was unstable and the amount of spatter generated was large.

Wire symbol W17 had low Mo content, so the tensile strength of the weld metal was low. In addition, since the total F conversion value of the metal fluoride was large, the bead appearance was poor.

Wire symbol W18 had a large amount of Mo, so the tensile strength of the weld metal was high and the absorbed energy was low. In addition, since the total amount of Fe in the iron powder and in the iron alloy was small, the arc was unstable and a large amount of spatter was generated.

Wire symbol W19 had a low amount of Ti, so the absorbed energy of the weld metal was low. In addition, since the sum of Na-converted values and K-converted values of Na compounds and K compounds was small, the arc was unstable and a large amount of spatter was generated.

Wire symbol W20 has a large amount of Ti, so the absorbed energy of the weld metal is low. In addition, since the sum of Na-converted values and K-converted values of Na compounds and K compounds was large, the frequency of slag splashing was high.

Wire symbol W21 has a low amount of B, so the absorbed energy of the weld metal is low.

Wire symbol W22 has a large amount of B, so the tensile strength of the weld metal is high and the absorbed energy is low.

For the wire with the symbol W23, the total amount of Fe in the iron powder and the Fe content in the iron alloy was large, so wire breakage occurred frequently during wire drawing during wire production, and the welding test was stopped.

Reference Signs List 1 Steel plate 2 Root gap 3 Welding wire 4 Welding torch 5 Gas supply nozzle 6 Weld metal 7 Cooling water supply nozzle 8 Fixed backing material 9 Groove of sliding copper contact 10 Groove 11 Sliding copper contact 12 Molten metal

Claims (1)

A flux-cored wire for electrogas arc welding in which a steel sheath is filled with flux,
% by mass of the total mass of the wire, the sum of the steel sheath and flux,
C: 0.005 to 0.05%,
Si: 0.3 to 1.1%,
Mn: 1.8-3.3%,
Mo: 0.2-0.8%,
Ti: 0.05-0.22%,
B: contains 0.004 to 0.020%,
Al: 0.01% or less,
In addition, in mass % with respect to the total mass of the wire, in the flux,
Total CO ₂ conversion value of one or more metal carbonates: 0.2 to 0.5%,
Total of one or more metal oxides: 0.1 to 0.4%,
Total F conversion value of metal fluorides: 0.05 to 0.40%,
Sum of Na conversion value and K conversion value of Na compound and K compound: 0.05 to 0.40%,
Total Fe content in iron powder and Fe content in iron alloy: 15 to 25%,
1. A flux-cored wire for electrogas arc welding, wherein the balance consists of Fe content of a steel outer sheath and unavoidable impurities.

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