JP5874068B2 - Flux for single-sided submerged arc welding - Google Patents

Description

  The present invention relates to a flux used for single-sided submerged arc welding performed using one or two or more electrodes. More specifically, the present invention relates to a bead appearance improving technique in a single-sided submerged arc welding flux containing iron powder.

  In single-sided submerged arc welding, a flux to which iron powder is added is usually used in order to ensure the amount of welding and realize stable bead formation even in high heat input welding (see, for example, Patent Document 1). ). However, the conventional single-sided submerged arc welding flux containing iron powder as described in Patent Document 1 has a problem that minute iron particle projections are likely to be generated on the surface of the front bead. Since such protrusions on the surface bead obstruct the painting process, for example, in the shipbuilding field, it corresponds to the new painting standard in the construction process, and the grinder is spread over the entire bead line to remove the iron particle protrusions. Has been forced to process.

  Therefore, conventionally, techniques for suppressing the generation of iron grain protrusions in a single-sided submerged arc welding flux have been proposed (see Patent Documents 2 and 3). For example, in the single-sided submerged arc welding flux described in Patent Document 2, bead soundness is achieved by setting the particle size and apparent density within a specific range. Moreover, in the bond flux for submerged arc welding described in Patent Document 3, the content of the Fe component is restricted to 5% by mass or less in order to suppress the generation of iron grain protrusions.

Japanese Patent Laid-Open No. 11-267883 JP-A-6-277878 JP 2006-272348 A

  However, as in the technique described in Patent Document 2, only by regulating the particle size and apparent density of the flux, the effect of suppressing the generation of iron grain protrusions is small. In addition, when the Fe content is regulated as in the bond flux for submerged arc welding described in Patent Document 3, it is difficult to secure a sufficient amount of welding in the plate joint welding of thick plates, and further in high heat input welding. The bead shape deteriorates. Thus, in conventional bead appearance improvement technology, in single-sided submerged arc welding, while maintaining the effect of adding iron powder to the flux, the occurrence of iron grain protrusions is suppressed and the bead appearance is soundened. Not in.

  Therefore, the main object of the present invention is to provide a single-sided submerged arc welding flux capable of obtaining a sound front bead shape and mechanical performance.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive experimental studies to ensure the soundness of the front bead in single-sided submerged arc welding using one or two or more electrodes. The inventors have found that the type of iron powder contained in the flux, the amount of oxygen, and the particle size have a great influence on the suppression of the generation of protrusions, leading to the present invention.

That is, the flux for single-sided submerged arc welding according to the present invention is SiO ₂ : 10 to 30% by mass, CaO: 3 to 9% by mass, MgO: 15 to 35% by mass, TiO ₂ : 4 to 20% by mass, CaF _2. : 2-9 _{wt%, Al} 2 O 3: 5 to 20 _wt%, CO 2: 2-9 _wt%, Na 2 O: 1 to 3 _{wt%, B} 2 O 3: 0.1 to 1 wt%, While containing Mo: 0.2-1 mass%, iron powder: 10-30 mass%, Si: 2 mass% or less, Mn: 1.5 mass% or less, Ti: 1 mass% or less, Al: 3 mass %, The atomized reduced iron powder having an oxygen content of 0.5% by mass or less is used for the iron powder, and the particle size is 40 μm or less with respect to the total amount of the iron powder. It is trying to become more than%.
In the single-sided submerged arc welding flux of the present invention, a specific amount of atomized reduced iron powder having an oxygen content of 0.5% by mass or less is added, and among the added iron powders, 40% by mass of which particle size is 75 μm or less. % Or more, it is difficult for iron particles to be generated on the surface beads, and a healthy surface bead without iron particle protrusions can be obtained.
This single-sided submerged arc welding flux may contain Si: 0.5-2% by mass and / or Ti: 0.3-1% by mass.
Moreover, you may contain 0.5-1.5 mass% of Mn.
Furthermore, you may contain 0.7-3 mass% of Al.

  According to the present invention, since the component of the flux and the content thereof are specified and the type of iron powder, the amount of oxygen, and the particle size of the iron powder are limited, single-sided submerged arc welding using one electrode or multiple electrodes However, a sound bead shape and mechanical performance can be obtained regardless of the backing structure.

It is an assumption figure of the iron particle generation behavior in the single-sided submerged arc welding process. It is sectional drawing which shows the groove shape of the steel plate used in the Example of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

  FIG. 1 is an assumption diagram of iron particle generation behavior in a single-sided submerged arc welding process. As shown in FIG. 1, in the single-sided submerged arc welding, when the flux 3 containing the conventional iron powder 5 is used, the iron powder 5 aggregates in the flux (slag) 4 during melting and solidification (of the iron powder). Aggregation 6), when this agglomerated iron powder (iron particles) 7 settles down and adheres to the surface of weld metal 2 (bead surface 2a) formed at the welded portion of base material 1 to generate minute protrusions. is assumed. Therefore, the present inventors have decided to solve the problem of iron grain protrusion generation by improving the characteristics of the flux.

Specifically, the flux according to the embodiment of the present invention is used for single-sided submerged arc welding, and includes at least SiO ₂ , CaO, MgO, TiO ₂ , CaF ₂ , Al ₂ O ₃ , CO ₂ , Na. _While containing a specific amount of ₂ O, B ₂ O ₃ , Mo and iron powder, it has a composition in which Si, Mn, Ti and Al are regulated to a specific amount or less. In this flux, atomized reduced iron powder having an oxygen content of 0.5% by mass or less is used for the iron powder, and the particle size of 75 μm or less with respect to the total amount of iron powder is 40% by mass or more. It is adjusted to. Hereinafter, the reasons for limiting the composition of the flux of this embodiment will be described.

[SiO ₂ : 10 to 30% by mass]
SiO ₂ is a glass-forming component, if the content exceeds 30 mass%, increase the viscosity of the whole molten slag, fluidity of the slag is lowered. In the case of high-speed single-sided submerged arc welding, the front bead width does not widen and becomes unstable, so that undercut is likely to occur. On the other hand, when the SiO ₂ content is less than 10% by mass, the solidification temperature of the molten slag becomes too high, so that a good surface bead shape cannot be obtained. Thus, SiO ₂ content is 10 to 30 mass%.

[CaO: 3 to 9% by mass]
CaO has the effect of reducing the viscosity of the molten slag, increasing the fluidity of the slag, and widening the surface bead width. However, if the CaO content exceeds 9% by mass, the solidification temperature of the molten slag becomes too high and the surface bead shape is impaired. On the other hand, when the CaO content is less than 3% by mass, the effect of increasing the fluidity of the molten slag cannot be obtained, and the surface bead width is insufficient, so that undercut is likely to occur. Therefore, the CaO content is 3 to 9% by mass.

[MgO: 15 to 35% by mass]
Similar to CaO described above, MgO has the effect of reducing the viscosity of the molten slag, increasing the fluidity of the slag, and widening the surface bead width. However, when the content of MgO is less than 15% by mass, the effect of increasing the fluidity of the molten slag cannot be obtained, the surface bead width is insufficient, and undercut is likely to occur. On the other hand, since MgO is a component having a high melting point, if it is added in excess of 35% by mass, the meltability of the entire flux is impaired, particularly when performing high-speed single-sided submerged arc welding of a thin plate that has a low heat input. A stable bead cannot be secured. Therefore, MgO content shall be 15-35 mass%.

[TiO ₂ : 4 to 20% by mass]
TiO ₂ is a particularly effective component for improving the slag peelability in single-sided welding. However, when the content exceeds 20% by mass, the waviness of the surface bead becomes rough, and when it is less than 4% by mass, the above-described effect of improving the slag peelability cannot be obtained. Therefore, the TiO ₂ content is 4 to 20% by mass.

[CaF ₂ : 2 to 9% by mass]
CaF ₂ is a component that improves the meltability of the entire flux, and is an indispensable component particularly in a welding method in which the flux must be melted in a short time and slag must be generated, such as single-sided submerged arc welding. . However, when the CaF ₂ content exceeds 9% by mass, the arc stability is degraded and arc breakage is likely to occur. On the other hand, when the CaF ₂ content is less than 2% by mass, the effect of improving the meltability of the flux cannot be obtained, and bead meandering occurs. Therefore, CaF ₂ content is 2-9 wt%.

[Al ₂ O ₃ : 5 to 20% by mass]
Al ₂ O ₃ is a neutral component and is an effective component for adjusting the viscosity of the slag and the solidification temperature. However, when the Al ₂ O ₃ content is less than 5% by mass, the viscosity of the slag and the solidification temperature are lowered, and the bead width becomes uneven. On the other hand, when Al ₂ O ₃ is added in excess of 20% by mass, the solidification temperature of the slag becomes too high and the beads are difficult to spread, and the bead shape becomes convex. Thus, _Al 2 _{O 3} content is 5 to 20 mass%.

_[CO 2: 2 to 9 wt%
CO ₂ is an effective component for suppressing the penetration of nitrogen into the weld metal and reducing the amount of diffusible hydrogen, and is added to the flux as a metal carbonate. However, when the CO ₂ content is less than 2% by mass, the amount of diffusible hydrogen in the weld metal becomes high, and the cold cracking resistance deteriorates. On the other hand, when the CO ₂ content exceeds 9% by mass, the amount of gas generated becomes excessive, and a pock mark is generated on the front bead. Accordingly, CO ₂ content is 2-9 wt%.

[Na ₂ O: 1 to 3% by mass]
Na ₂ O is a component necessary for ensuring arc stability. Specifically, when the Na ₂ O content is less than 1% by mass, the arc becomes extremely unstable, arc breakage occurs, and the bead shape and penetration become uneven. On the other hand, when the Na ₂ O content exceeds 3% by mass, the hygroscopic resistance is lowered and the low temperature cracking resistance is deteriorated.

[B ₂ O ₃ : 0.1 to 1% by mass]
B ₂ O ₃ is reduced during welding and exists as B in the weld metal, and effectively acts to ensure toughness. However, when the content of B ₂ O ₃ is less than 0.1% by mass, the effect is not sufficiently exhibited and the toughness is deteriorated. On the other hand, if the B ₂ O ₃ content exceeds 1% by mass, the strength becomes excessive and high temperature cracking occurs. _Accordingly, B 2 _{O 3} content is 0.1 to 1 mass%.

[Mo: 0.2 to 1% by mass]
Mo is an effective component for improving hardenability, and is added in the form of Fe—Mo or the like in addition to Mo alone. However, when the Mo content is less than 0.2% by mass, the structure of the weld metal becomes coarse and the toughness deteriorates. On the other hand, if Mo is added in excess of 1% by mass, the strength of the weld metal becomes excessive and high temperature cracking occurs.

[Iron powder: 10-30% by mass]
Iron powder is an essential additive component in a single-sided submerged arc that requires a large amount of deposited metal at a time. And when iron powder content is less than 10 mass%, while the effect which supplements the amount of welding metal cannot be acquired, since the apparent density of a flux becomes small, blowing-up resistance deteriorates. On the other hand, when iron powder is contained exceeding 30% by mass, the iron powder tends to aggregate in the flux during melting and solidification, and the amount of the aggregated iron powder settles, and iron particles adhere to the bead surface. It becomes easy to do. In addition, the apparent density of the flux increases and the bead width cannot be secured. Therefore, content of iron powder shall be 10-30 mass%.

  In the flux of the present embodiment, atomized reduced iron powder is used as the iron powder. Generally, as a kind of iron powder, it classifies into reduced iron powder and atomized iron powder from the manufacturing method. Among these, the atomized iron powder has a reduced type or an unreduced type. And among these, the reduction type of atomized iron powder is effective for the reduction of iron grain protrusions.

  Furthermore, the amount of oxygen in the iron powder also affects the generation of iron particles. Specifically, when the oxygen content of the iron powder exceeds 0.5% by mass, the iron powder becomes difficult to dissolve in the slag, and is likely to be generated as iron grain protrusions on the surface bead. Therefore, the iron powder blended in the flux of this embodiment has an oxygen content of 0.5% by mass or less. In addition, the oxygen amount of the iron powder is preferably 0.3% by mass or less, and thereby further iron grain reduction effect can be obtained. Here, the oxygen content of the iron powder can be measured, for example, by a heating and melting method in an inert gas.

  Furthermore, the particle size of the iron powder affects the aggregation / sedimentation in the molten slag and also affects the generation of iron particles. Specifically, when the amount of particles having a particle size of 75 μm or less is less than 40% by mass with respect to the total amount of iron powder, the individual iron powder is melted and easily settled. As a result, iron grain protrusions are likely to occur on the bead surface. Therefore, the iron powder blended in the flux of the present embodiment has a particle size of 75 μm or less so as to be 40% by mass or more. Here, the particle size of the iron powder can be measured by, for example, a particle size measuring device using a sieve and a low tap shaker.

[Si: 2% by mass or less]
If Si is contained in excess of 2% by mass, the slag is seized on the bead surface and the slag peelability deteriorates, so the Si content is restricted to 2% by mass or less. On the other hand, since Si is also an effective component for reducing the amount of oxygen in the weld metal, when Si is contained in an amount of 0.5% by mass or more, a further deoxidizing effect is exhibited and toughness is improved. Therefore, in the flux of the present embodiment, Si is added in a range of 0.5 to 2% by mass as necessary. Si can be added in the form of Fe—Si or the like in addition to Si alone.

[Ti: 1% by mass or less]
Ti is an effective component for reducing the amount of oxygen in the weld metal, similar to Si described above. However, since this effect can be sufficiently achieved by adding Si or the like, Ti is essential in the flux of this embodiment. Is not an ingredient. Moreover, when Ti content exceeds 1 mass%, slag will seize on the bead surface and slag peelability will deteriorate. Therefore, the Ti content is restricted to 1% by mass or less. On the other hand, when 0.3 mass% or more of Ti is contained, the further deoxidation effect of a weld metal is implement | achieved and toughness can be aimed at. Therefore, in the flux of the present embodiment, Ti is added in the range of 0.3 to 1% by mass as necessary. Ti can be added in the form of Fe-Ti or the like in addition to Ti alone.

[Mn: 1.5% by mass or less]
Mn, like Mo described above, has an effect of improving hardenability and is an effective component for improving strength and toughness. However, when the Mn content exceeds 1.5% by mass, slag is formed on the bead surface. Seizure and slag peelability deteriorate. Further, in the flux of the present embodiment, Mo is added, and thereby the effect of hardenability is obtained, so the Mn content is restricted to 1.5% by mass or less. On the other hand, when Mn is contained in an amount of 0.5% by mass or more, further improvement in hardenability is realized and toughness is improved. Therefore, in the flux of the present embodiment, Mn is added in the range of 0.5 to 1.5 mass% as necessary. Mn can be added in the form of Fe—Mn or the like in addition to Mn alone.

[Al: 3% by mass or less]
Al is an effective component for improving the toughness by refining the structure of the weld metal. However, since this effect can be sufficiently achieved by adding other components, Al is not an essential component in the flux of the present embodiment. On the other hand, if the Al content exceeds 3% by mass, quenching becomes excessive, the strength increases, and low temperature cracking occurs. Therefore, the Al content is restricted to 3% by mass or less. On the other hand, if Al is contained in an amount of 0.7% by mass or more, further refinement of the structure is realized and toughness is improved. Therefore, in the flux of the present embodiment, Al is added in a range of 0.7 to 3% by mass as necessary. In addition to Al alone, Al can be added in the form of Fe—Al, Al—Mg, or the like.

[Other ingredients]
Components other than the above in the flux of the present embodiment are, for example, FeO, ZrO ₂ , K ₂ O, and the like.

  As described above in detail, the flux of the present embodiment has a specific amount of atomized reduced iron powder having an oxygen content of 0.5% by mass or less and a particle size of 75 μm or less with respect to the total amount of iron powder. Since it is 40 mass% or more, it is possible to suppress the agglomeration of iron powder in the flux during melting and solidification and the adhesion of the generated iron particles to the surface bead. As a result, in single-sided submerged arc welding, it is possible to form a sound surface bead that is excellent in mechanical performance and free from iron grain protrusions.

  The flux of this embodiment is mainly used in the single-sided submerged arc welding method, but the backing method is not particularly limited, and the flux copper back using the flux and copper as the backing material. This method, a flux backing method using only a flux as a backing material, and a backing method using a solid flux can be applied to any method. Further, the backing flux is not particularly limited, and a conventional flux can be applied as it is.

  Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention. In this example, the steel plate shown in Table 1 and the wire shown in Table 2 are used, and the welding conditions shown in Table 3 below and the groove shape of the steel plate (base material 10) shown in FIG. The performance of each flux in the examples and comparative examples was evaluated. At that time, as the filler 11, a commercially available filler (iron powder of 95% by mass or more) was used. In addition, the balance of the steel plate composition shown in the following Table 1 and the wire composition shown in the following Table 2 is Fe and inevitable impurities.

  The evaluation of each flux in the examples and comparative examples is based on welding workability (bead appearance, undercut, etc.), ultrasonic flaw detection (UT) test based on JIS Z3060 (presence of cracks, slag entrainment, etc.) and JIS Z2242. The Charpy impact test was performed. Tables 4 and 5 below show the evaluation results and the respective flux compositions of Examples and Comparative Examples. In addition, "75 micrometers (mass%)" shown in the following Table 4 and Table 5 is content (mass%) of the iron powder whose particle size is 75 micrometers or less with respect to iron powder whole quantity. In the Charpy impact test, Charpy absorbed energy (vE-20 ° C) at a test temperature of -20 ° C passed 50J or more, and less than 50J was rejected.

  As shown in Table 4, the fluxes of Examples 1 to 32 produced within the scope of the present invention were good in all of welding workability, ultrasonic flaw detection (UT) test, and toughness (vE-20 ° C.). It was.

  On the other hand, as shown in Table 5, the flux of Comparative Example 1 had an undercut because the MgO content in the flux was less than the lower limit of the range of the present invention. On the other hand, the flux of Comparative Example 2 was overlapped because the MgO content exceeded the upper limit of the range of the present invention. Since the flux of Comparative Example 3 had an Fe content that was less than the lower limit of the range of the present invention, an underscore was generated. In the flux of Comparative Example 4, the Fe content exceeded the upper limit of the range of the present invention, so iron particles were generated on the bead surface.

The flux of Comparative Example 5 had an overlap because the SiO ₂ content was less than the lower limit of the range of the present invention. On the other hand, the flux of Comparative Example 6 was undercut because the SiO ₂ content exceeded the upper limit of the range of the present invention. Moreover, since the flux of Comparative Example 7 had an Al ₂ O ₃ content that was less than the lower limit of the range of the present invention, the bead width was not uniform. On the other hand, the flux of Comparative Example 8 had a convex bead because the Al ₂ O ₃ content exceeded the upper limit of the range of the present invention.

Since the flux of Comparative Example 9 had a TiO ₂ content less than the lower limit of the range of the present invention, the slag peelability was deteriorated. On the other hand, since the flux of Comparative Example 10 had a TiO ₂ content exceeding the upper limit of the range of the present invention, the bead wave became rough. Moreover, since the flux of Comparative Example 11 had a CaO content that was less than the lower limit of the present invention range, undercut occurred. On the other hand, since the CaO content of the flux of Comparative Example 12 exceeded the upper limit of the range of the present invention, the bead became convex.

Since the flux of Comparative Example 13 had a CO ₂ content that was less than the lower limit of the range of the present invention, the amount of diffusible hydrogen in the weld metal increased, and low temperature cracking occurred. On the other hand, since the flux of Comparative Example 14 had a CO ₂ content exceeding the upper limit of the range of the present invention, a pock mark was generated on the bead surface. Moreover, since the CaF ₂ content of the flux of Comparative Example 15 was less than the lower limit of the range of the present invention, bead meandering occurred. On the other hand, in the flux of Comparative Example 16, since the CaF ₂ content exceeded the upper limit of the range of the present invention, arc breakage occurred frequently.

In the flux of Comparative Example 17, the Na ₂ O content was less than the lower limit of the range of the present invention, and therefore bead meandering occurred. On the other hand, since the Na ₂ O content of the flux of Comparative Example 18 exceeded the upper limit of the range of the present invention, cold cracking occurred. Moreover, since the Si content exceeded the upper limit of the range of the present invention in the flux of Comparative Example 19, slag seizure occurred and toughness deteriorated. Furthermore, since the Mn content of the flux of Comparative Example 20 exceeded the upper limit of the range of the present invention, the slag peelability deteriorated. Furthermore, since the Ti content of the flux of Comparative Example 21 exceeded the upper limit of the range of the present invention, the slag peelability deteriorated.

The flux of Comparative Example 22 was deteriorated in toughness because the Mo content was less than the lower limit of the range of the present invention. On the other hand, in the flux of Comparative Example 23, since the Mo content exceeded the upper limit of the range of the present invention, hot cracking occurred in the weld metal. Also, the flux in Comparative Example 24, since the content of B ₂ O ₃ is less than the lower limit of the range of the present invention, the toughness is deteriorated. On the other hand, the flux in Comparative Example 25, since the content of B ₂ O ₃ exceeds the upper limit of the range of the present invention, hot cracking occurred in the weld metal. Further, in the flux of Comparative Example 26, since the Al content exceeded the upper limit of the range of the present invention, cold cracking occurred.

  In the flux of Comparative Example 27, the amount of iron powder oxygen exceeded the upper limit of the range of the present invention, so iron particles were generated on the bead surface. On the other hand, since the composition ratio of the particle size of the used iron powder was less than the lower limit of the range of the present invention in the flux of Comparative Example 28, iron particles were generated on the bead surface. Moreover, since the reduced iron powder produced by methods other than the atomizing method was used for the flux of the comparative example 29, the iron particle generate | occur | produced on the bead surface. Furthermore, since the unreduced iron powder was used for the flux of Comparative Example 30, iron particles were generated on the bead surface.

  In addition, in the evaluation of each flux of the examples and comparative examples described above, single-sided submerged arc welding was performed using a backing material generated with a solid flux, but a flux copper backing method using a copper plate and a backing flux, and Similar results were obtained in the flux backing method performed while solidifying the backing flux without using a copper plate. Tables 4 and 5 show the results of 1-electrode welding. In addition, in 2-electrode, 3-electrode and 4-electrode welding, there is no difference in the flux melting and solidification process after welding. 4 and the same result as the case of 1 electrode welding shown in Table 5 were obtained.

  From the above results, it was confirmed that by using the flux of the present invention, a sound surface bead shape and mechanical characteristics can be obtained in single-electrode or multi-electrode single-sided submerged arc welding.

DESCRIPTION OF SYMBOLS 1, 10 Base material 2 Weld metal 2a Bead surface 3 Unmelted flux 4 Flux in melting and solidification (slag)
5 Iron powder 6 Aggregation of iron powder 7 Aggregated iron powder (iron particles)
11 Filler

Claims (4)

SiO2: 10 to 30% by mass,
CaO: 3 to 9% by mass,
MgO: 15 to 35% by mass,
TiO2: 4 to 20% by mass,
CaF2: 2 to 9% by mass,
Al2O3: 5 to 20% by mass,
CO2: 2-9% by mass,
Na2O: 1-3% by mass,
B2O3: 0.1 to 1% by mass,
Mo: 0.2-1 mass%,
Iron powder: 10-30% by mass
And containing
Si: 2% by mass or less,
Mn: 1.5% by mass or less,
Ti: 1% by mass or less,
Al: having a composition regulated to 3% by mass or less,
The iron powder is a reduced type atomized iron powder having an oxygen content of 0.5% by mass or less, and a particle size of 75 μm or less with respect to the total amount of iron powder is 40% by mass or more for single-sided submerged arc welding. flux.   The flux for single-sided submerged arc welding according to claim 1, characterized by containing Si: 0.5-2 mass% and / or Ti: 0.3-1 mass%.   The flux for single-sided submerged arc welding according to claim 1 or 2, comprising 0.5 to 1.5 mass% of Mn.   The flux for single-sided submerged arc welding according to any one of claims 1 to 3, wherein Al is contained in an amount of 0.7 to 3% by mass.

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