JP2005329462A - Fused flux for submerged arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide fused flux for submerged arc welding which is excellent in the performance of high-speed two-side single-layer welding and also lessens oxygen content in weld metal without causing high basification. <P>SOLUTION: The fused flux for submerged arc welding contains, based on total mass of flux, 23-33 mass% SiO<SB>2</SB>, 5-25 mass% Ca compound (in Ca terms), 5-35 mass% Ba compound (in Ba terms), 1-14 mass% F compound (in F terms), 7-18 mass% MgO, 1-13 mass% Al<SB>2</SB>O<SB>3</SB>, 1-9 mass% MnO, 0.5-5.0 mass% ZrO<SB>2</SB>, 0.5-5.0 mass% FeO and TiO<SB>2</SB>limited to 8 mass% or less, with a total of Ca compound and Ba compound limited to 40 mass% or less, and the values of [M], [N] and [P] obtained from the following expressions are made to be 300 or less, more than 0, and 0 or less respectively:[M]=1,050-[SiO<SB>2</SB>]-19×[Ca]-12×[Ba]-5×[F]-15×[MgO]-5×[Al<SB>2</SB>O<SB>3</SB>]-5×[MnO]-3×[ZrO<SB>2</SB>]-5×[FeO]-3×[TiO<SB>2</SB>]. [N]=32.5-(3/4)×([Ca]×[Ba])-[F]. [P]=[Ca]-(20/3)×[MgO]+31. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a molten flux for submerged arc welding used for high-speed submerged arc welding suitable for welding large diameter steel pipes such as line pipes and structural pipes.

  In seam welding of steel pipes used in pipelines that transport natural gas and oil, etc., the welding speed has been increased in order to improve pipe making efficiency, and accordingly, undercuts and slag entrainment, etc. Problems such as an increased incidence of welding defects have occurred. Conventionally, when seam welding such a large-diameter steel pipe, double-sided single-layer welding by a multi-electrode submerged arc welding method capable of high-speed welding has been applied. However, there is a problem that welding defects such as undercut and slag entrainment are likely to occur.

  Therefore, a method for reducing the occurrence of welding defects in high-speed welding of steel pipes has been proposed (see, for example, Patent Documents 1 to 7). In the welding methods described in Patent Documents 1 to 6, defects are reduced by using multiple electrodes and performing welding while applying magnetic stirring to the weld metal. Patent Document 7 proposes a high-speed submerged arc welding method using six or more electrodes.

  In recent years, steel pipes used in pipelines tend to be strengthened in order to increase operating pressure to improve transport efficiency and reduce costs. High toughness is also required so that it can be used in harsh environments. For this reason, the weld metal is also required to have high strength and high toughness, and the establishment of a technology that can achieve these simultaneously is desired. As a method of increasing the strength of the weld metal, a method of increasing the carbon equivalent or adding a suitable amount of Ti, B or the like in combination is known. On the other hand, the toughness of the weld metal can be improved to some extent by these methods, but it is insufficient for the recent demand for higher toughness. In particular, when the hardness is limited like a weld metal of a pipe used in a sour environment, these methods cannot be applied and the intended toughness cannot be obtained. Therefore, as a method of improving the toughness of the weld metal, a method of increasing the basicity of the flux and reducing the oxygen content in the weld metal is applied.

  Conventionally, in order to improve the low temperature toughness of the weld metal, examination of welding materials has been made (see, for example, Patent Document 8). Patent Document 8 proposes a fusion flux for submerged arc welding that provides a weld metal with good welding workability and excellent low-temperature toughness even when applied to high-speed submerged arc welding by defining the components of the flux. Has been.

JP-A-9-85440 Japanese Patent Laid-Open No. 9-277043 JP 9-239536 A JP 10-43859 A JP-A-10-258363 JP-A-10-258364 JP-A-4-147770 Japanese Patent Publication No. 5-38677

  However, the conventional techniques described above have the following problems. First, the welding methods described in Patent Documents 1 to 6 require a facility for forming a magnetic field for magnetic stirring of the weld metal, which increases the manufacturing cost. In the welding method described in Patent Document 7, the welding speed can be increased by increasing the number of electrodes. However, there are problems such as an increased risk of occurrence of welding defects, an increase in equipment costs, and a complicated operation. Will occur. Furthermore, in Patent Documents 1 to 7, no contrivance for improving the toughness of the weld metal is made.

  On the other hand, when the basicity of the flux is increased in order to improve the low temperature toughness, pock marks and bead meandering occur and the bead appearance tends to deteriorate, and this tendency is particularly noticeable in high-speed welding. Further, when the basicity of the flux is increased, contraction holes are likely to be generated intermittently at the center of the bead. Although this shrinkage hole is not a major problem with respect to the mechanical performance of the weld metal, when paint is applied to the welded structure in a later process, the paint tends to peel off, and the peeled portion may be selectively corroded. . As described above, the method of reducing the oxygen content in the weld metal by increasing the basicity of the flux has a problem of deterioration of the bead appearance and generation of shrinkage holes, and when low-temperature toughness is required in high-speed welding. It cannot be applied.

  The flux described in Patent Document 8 is a flux related to the two-electrode welding method. Recently, the welding speed has been further increased in order to improve the welding efficiency, and the performance sufficient for the toughness currently required. It is hard to say. For this reason, the further improvement in performance is calculated | required by the fusion type flux for submerged arc welding.

  The present invention has been made in view of such problems, and is excellent in welding workability in high-speed welding on both sides, and further, melting for submerged arc welding in which the amount of oxygen in the weld metal is reduced without being highly basic. The object is to provide mold flux.

The melt type flux for submerged arc welding according to the present invention has a SiO _{2 of} 23 to 33% by mass, a Ca compound: 5 to 25% by mass in terms of Ca, and a Ba compound: 5 to 35% by mass in terms of Ba, based on the total mass of the flux. , F compound: 1 to 14% by mass in terms of F, MgO: 7 to 18% by mass, Al ₂ O ₃ : 1 to 13% by mass, MnO: 1 to 9% by mass, ZrO ₂ : 0.5 to 5.0 Containing 0.5% by mass, FeO: 0.5 to 5.0% by mass, TiO ₂ : 8% by mass or less, Ca compound and Ba compound: 40% by mass or less in total, SiO ₂ content (% by mass) [SiO ₂ ], the Ca equivalent content (% by mass) of the Ca compound is [Ca], the Ba equivalent content (% by mass) of the Ba compound is [Ba], and the F equivalent content (% by mass) of the F compound. [F], MgO content (% by mass) [MgO], Al ₂ O ₃ content [Al ₂ O ₃ ], MnO content (mass%) [MnO], ZrO ₂ content (mass%) [ZrO ₂ ], FeO content (mass %) Is [FeO] and TiO ₂ content (% by mass) is [TiO ₂ ], [M] given by the following formula 1 is 300 or less, and [N] given by the following formula 2 is 0. And [P] given by Equation 3 below is 0 or less.

In the present invention, the contents of SiO ₂ , Ca compound, Ba compound, F compound, MgO, Al ₂ O ₃ , MnO, ZrO ₂ , FeO and TiO ₂ contained in the flux and affecting welding workability are determined. Since each is in the above range, welding workability is improved. Further, since [M] defined by the content of the component that affects the oxygen content in the weld metal and given by the above mathematical formula 1 is set to 300 or less, the oxygen content in the weld metal can be set to 300 ppm or less. it can. Thereby, the weld metal excellent in low-temperature toughness is obtained. Further, since the [N] defined by the contents of the Ca compound, Ba compound and F compound, which affects the generation of shrinkage pores and given by the above mathematical formula 2, is larger than 0, the occurrence of shrinkage pores is prevented. Can be suppressed. Furthermore, since [P] given by Equation 3 is 0 or less, the occurrence of bead meandering can be suppressed.

According to the present invention, welding workability is improved by optimizing the contents of SiO ₂ , Ca compound, Ba compound, F compound, MgO, Al ₂ O ₃ , MnO, ZrO ₂ , FeO and TiO _2. In addition, by regulating the [M] obtained from the contents of SiO ₂ , Ca compound, Ba compound, F compound, MgO, Al ₂ O ₃ , MnO, ZrO ₂ , FeO and TiO ₂ to 300 or less In addition, the amount of oxygen in the weld metal can be reduced, and further, the generation of shrinkage holes can be suppressed by making [N] larger than 0 determined by the contents of Ca compound, Ba compound and F compound. Furthermore, by making [P] determined by the contents of the Ca compound and MgO 0 or less, the occurrence of bead meandering can be suppressed.

  Hereinafter, the fusion flux for submerged arc welding according to the present invention will be specifically described with reference to the accompanying drawings. As a result of earnest experiment research to achieve the above-mentioned object, the present inventors have derived the relationship between the flux component and the amount of oxygen that affects the low temperature toughness of the weld metal, and further, the workability in high-speed welding is excellent. The present inventors have found a flux composition capable of obtaining a weld metal having excellent low-temperature toughness. Specifically, the present inventors have studied three- or four-electrode welding in consideration of further increasing the welding speed and the accompanying increase in equipment cost, and as a result, the fusion mold for submerged arc welding has been studied. It has been found that the amount of oxygen in the weld metal can be reduced and the weld metal can be made tougher and workability in high-speed welding can be improved by setting the flux composition within the following range.

  Hereinafter, the reason for limitation of the component composition of the melt-type flux for submerged arc welding according to the present invention will be described.

SiO ₂ : 23 to 33% by mass
SiO ₂ is a basic component of the melt type flux and is an effective component for adjusting the viscosity and melting point of the molten slag. However, if the SiO ₂ content is less than 23% by mass, the viscosity of the molten slag is insufficient and bead meandering is likely to occur. On the other hand, if the SiO ₂ content exceeds 33% by mass, the viscosity of the molten slag becomes too high, and the bead shape becomes convex. Therefore, the SiO ₂ content is 23 to 33% by mass.

Ca compound: 5 to 25% by mass in terms of Ca, Ba compound: 5 to 35% by mass in terms of Ba, Ca compound + Ba compound: 40% by mass or less in total amount Reduce the amount of oxygen in the Ca compound, Ba compound and weld metal It is highly effective and is a component useful for increasing the toughness of the weld metal, and also has the effect of preventing the occurrence of shrinkage holes. However, when the Ca compound content or the Ba compound content is less than 5% by mass, the effect is not sufficiently obtained and shrinkage holes are generated. On the other hand, the Ca compound and the Ba compound break the Si—O bond of the glassy silicic acid having an irregular network structure. Therefore, when the amount of these compounds added is large, the viscosity of the molten slag is lowered, and when added excessively, the compound melts. The bead meanders due to lack of metal hold. Further, when the Ca compound and the Ba compound are added in excess, they are easily crystallized. Specifically, when the content of the Ca compound exceeds 25% by mass or the content of the Ba compound exceeds 35% by mass, Hygroscopic resistance is lowered and a pock mark is likely to be generated. Furthermore, when the total content of Ca compound and Ba compound exceeds 40% by mass, the flux becomes crystallized, the moisture absorption resistance is lowered and a pock mark is generated, and the viscosity of the molten slag is lowered and the bead meandering occurs. Occur.

Therefore, the content of the Ca compound and the Ba compound is an amount that can maintain an appropriate viscosity and does not cause bead meandering. That is, the Ca compound content is 5 to 25% by mass in terms of Ca, the Ba compound content is 5 to 35% by mass, and the total content of the Ca compound and Ba compound is 40% by mass or less. In addition, content of Ca compound in this invention is the value which converted all Ca compounds contained in a flux with Ca, and content of Ba compound means all Ba compounds contained in a flux to Ca. The same applies to the following description. Examples of the Ca compound and Ba compound added to the melted flux for submerged arc welding of the present invention include CaO, CaF ₂ , BaO, BaF _{2 and the} like.

F compound: 1 to 14% by mass in terms of F
The F compound has a high effect of reducing the amount of oxygen in the weld metal, and is a component useful for increasing the toughness of the weld metal. However, if the content of the F compound is less than 1% by mass, the effect cannot be sufficiently obtained, the viscosity becomes high, and the bead shape becomes convex. On the other hand, since the F compound breaks the Si-O bond of the glassy silicic acid having an irregular network structure, the viscosity of the molten slag decreases when the amount of the F compound added is large, and when it is added excessively, the molten metal is suppressed. The bead meandering occurs due to lack of. Further, the present inventors have found that the tendency of shrinkage pores to change depends on the content of the F compound, and that the F compound is a component that promotes the generation of shrinkage pores. When the content of the F compound exceeds 14% by mass, the viscosity decreases, the beads meander, and shrinkage holes are generated. Therefore, the F content is 1 to 14% by mass. In addition, content of F compound in this invention is the value which converted all F compounds contained in a flux by F, and it is the same also in the following description. As the F compound added to the melt flux for the submerged arc welding of the present invention, for _{example, CaF 2, BaF 2, NaF} , AlF 3, MgF 2 and the like.

MgO: 7 to 18% by mass
MgO is an effective component for adjusting the viscosity of the molten slag, and is highly effective in reducing the amount of oxygen in the weld metal. However, if the MgO content is less than 7% by mass, the viscosity of the molten slag is insufficient and bead meandering is likely to occur. On the other hand, if the MgO content exceeds 18% by mass, the flux is crystallized, the moisture absorption resistance is deteriorated, and a pock mark is likely to be generated. Therefore, the MgO content is 7 to 18% by mass.

Al ₂ O ₃ : 1 to 13% by mass
In the component system of the melt type flux for submerged arc welding of the present invention, Al ₂ O ₃ constitutes a network structure similar to SiO ₂ and is an effective component for adjusting the viscosity and melting point of the molten slag. However, when the content of Al ₂ O ₃ is less than 1% by mass, the viscosity of the molten slag is insufficient and bead meandering is likely to occur. On the other hand, when the content of Al ₂ O ₃ exceeds 13% by mass, the viscosity of the molten slag becomes too high and the bead shape becomes convex. Therefore, the Al ₂ O ₃ content is 1 to 13% by mass.

MnO: 1 to 9% by mass
MnO is an effective component for adjusting the viscosity of the molten slag, and also has an effect of suppressing the generation of shrinkage holes. However, if the content of MnO is less than 1% by mass, sufficient effects cannot be obtained and shrinkage holes are generated. On the other hand, MnO is also a component that easily supplies oxygen to the molten steel, and in order to reduce the amount of oxygen in the weld metal, it is preferable to suppress the amount of addition, specifically, the content of MnO is 9 mass. % Or less. When the MnO content exceeds 9% by mass, the viscosity of the molten slag increases, the bead shape becomes convex and seizure occurs. Therefore, the MnO content is 1 to 9% by mass.

ZrO ₂ : 0.5 to 5.0% by mass
ZrO ₂ has an extremely high effect of stabilizing the bead width. However, if the ZrO ₂ content is less than 0.5% by mass, sufficient effects cannot be obtained, and bead meandering occurs. However, since ZrO ₂ is also a component that increases the amount of oxygen in the weld metal, the content is preferably low. On the other hand, when the ZrO ₂ content exceeds 5.0 mass%, slag seizure occurs. Therefore, the ZrO ₂ content is set to 0.5 to 5.0% by mass.

FeO: 0.5 to 5.0% by mass
FeO has an effect of suppressing the generation of shrinkage holes. However, if the FeO content is less than 0.5% by mass, sufficient effects cannot be obtained, and shrinkage holes are generated. In addition, FeO is a component that easily supplies oxygen to the molten steel, similar to MnO described above, so in order to reduce the amount of oxygen in the weld metal, it is preferable to suppress the amount added, specifically The FeO content is 5.0% by mass or less. When the FeO content exceeds 5.0% by mass, slag seizure occurs. Therefore, the FeO content is 0.5 to 5.0 mass%.

TiO ₂ : 8% by mass or less TiO ₂ is an effective component for suppressing the generation of shrinkage holes, but its effect is relatively small. TiO ₂ is a component that increases the amount of oxygen in the weld metal, and the content is preferably low. Furthermore, when the TiO ₂ content exceeds 8% by mass, the occurrence of seizure of slag is remarkable. Therefore, the TiO ₂ content is restricted to 8% by mass or less.

[M]: 300 or less In the present invention, [M] given by the following Equation 4 is set to 300 or less. In [Formula 4] below, [SiO ₂ ] is the SiO ₂ content (% by mass), [Ca] is a value obtained by converting the total content (% by mass) of the Ca compound contained in the flux with Ca, and [Ba] is The value obtained by converting the total content (mass%) of the Ba compound contained in the flux with Ba, [F] is the value obtained by converting the total content (mass%) of the F compound contained in the flux with F, [MgO ] Is MgO content (% by mass), [Al ₂ O ₃ ] is Al ₂ O ₃ content (% by mass), [MnO] is MnO content (% by mass), and [ZrO ₂ ] is ZrO ₂ content ( Mass%), [FeO] is the FeO content (mass%), and [TiO ₂ ] is the TiO ₂ content (mass%).

As a result of examining the relationship between the amount of oxygen in the weld metal and the flux component with respect to various fluxes, the present inventors have determined that [M] given by Equation 4 above is between the amount of oxygen in the weld metal. We found a strong correlation. FIG. 1 is a graph showing the relationship between [M] and the amount of oxygen in the weld metal, with [M] on the horizontal axis and the amount of oxygen in the weld metal on the vertical axis. The present inventors aim to reduce the oxygen content in the weld metal to 300 ppm or less in order to improve the low temperature toughness of the weld metal, but as shown in FIG. 1, [M] is set to 300 or less. As a result, the inventors have found that the amount of oxygen in the weld metal is 300 ppm or less. Further, as shown in the above mathematical formula 3, the degree of contribution to the reduction of the oxygen content in the weld metal is the largest in the Ca compound, Mg, Ba compound, “F compound, Al ₂ O ₃ , MnO and FeO”, “TiO”. ₂ and ZrO ₂ ”and SiO ₂ in order. In addition, the oxygen amount in the weld metal shown in FIG. 1 shows the same tendency regardless of the oxygen amount of the steel plate and the wire when the oxygen amount of the steel plate and the wire is both 100 ppm or less.

[N]: Greater than 0 Furthermore, in the present invention, [N] represented by the following Equation 5 is made larger than 0.

  As described above, the amount of oxygen in the weld metal can be reduced by adjusting [M], but the present inventors performed high-speed welding using a flux having [M] of 300 or less. However, shrinkage holes occurred in most fluxes. FIG. 2A is a plan view schematically showing the shape of the weld metal and the molten pool in high-speed welding, and FIG. 2B is a plan view schematically showing the shape of the weld metal and the molten pool in low-speed welding. is there. In general, the molten steel is contracted when solidified, but as shown in FIG. 2A, in the case of high-speed welding, the shape of the molten pool 3 is a teardrop type, and the molten steel is columnar crystal from the toe ends on both sides. Since 2 grows and contracts by solidification, a gap is easily formed in the center of the bead of the weld metal 1. Further, when the amount of oxygen in the weld metal 1 decreases, the surface tension of the molten metal increases, so that the molten metal is not sufficiently filled in the gap formed at the center of the bead, and the shrink hole 4 is generated. On the other hand, when the amount of oxygen in the weld metal is relatively large, the surface tension of the molten metal is low, and it is easy to fill the gaps that have solidified and contracted, so that the shrinkage holes 4 are unlikely to occur. Further, as shown in FIG. 2B, when the welding speed is low, the shape of the molten pool 3 becomes an ellipse, and the columnar crystals 2 are less likely to associate at the bead central portion, so that shrinkage holes are not easily formed. .

As a result of studying flux components that make it easy for the molten metal to enter the gap generated when solidified and contracted even when the surface tension of the molten metal is high, the present inventors have found that the Ca compound, Ba compound, MnO It has been found that FeO and TiO ₂ have an effect of suppressing the generation of shrinkage holes. However, as described above, MnO, FeO, and TiO ₂ are components that increase the amount of oxygen in the weld metal, and when added excessively, problems such as slag seizure occur. On the other hand, the Ca compound and the Ba compound not only have the effect of suppressing the generation of shrinkage holes, but also have the effect of reducing the amount of oxygen in the weld metal, but if added excessively, the surface tension of the molten metal becomes too high. Shrinkage holes may occur.

  As a result of further studies, the present inventors have found that the tendency of shrinkage pores to change depends not only on the content of the Ca compound and the Ba compound but also on the content of the F compound. And it discovered that Ca compound and Ba compound are components which can suppress generation | occurrence | production of a contraction hole, without increasing [M] significantly, and F compound is a component which promotes generation | occurrence | production of a contraction hole. . FIG. 3 shows the total content of Ca compound and Ba compound ([Ca] + [Ba]) on the horizontal axis and the content of F compound ([F]) on the vertical axis. It is a graph which shows the relationship between total content and F compound content, and shrinkage | contraction hole. As shown in FIG. 3, the occurrence of contraction holes can be suppressed by making [N] given by the above equation 4 larger than zero.

[P]: 0 or less Furthermore, in the present invention, [P] represented by the following formula 6 is set to 0 or less.

  When the content of MgO is 9% by mass or more, occurrence of bead meandering is not recognized if the composition of the flux satisfies the above range. However, when the MgO content is 7% by mass or more and less than 9% by mass, bead meandering may occur even if the flux composition satisfies the above range. Then, as a result of further studies, the present inventors have found that there is an appropriate balance between the Ca compound content and the MgO content. Specifically, when the MgO content decreases, the viscosity of the molten slag tends to decrease. In addition, as described above, since the Ca compound breaks the Si—O bond of the glassy silicic acid having an irregular network structure, the viscosity of the molten slag decreases when the Ca compound content is large. Although the Ba compound shows the same tendency, the Ba compound has a larger atomic weight than the Ca compound. Therefore, when the MgO content is 7% by mass or more and less than 9% by mass, the viscosity of molten slag is reduced by the Ba compound. Is less affected. Therefore, optimizing the balance between the Ca compound content and the MgO content is most effective in suppressing bead meandering.

  FIG. 4 is a graph showing the relationship between the MgO content and the Ca compound content, with the MgO content ([MgO]) on the horizontal axis and the Ca compound content ([Ca]) on the vertical axis. . As shown in FIG. 4, the occurrence of bead meandering can be suppressed by setting [P] given by Equation 6 to 0 or less. However, when the MgO content is less than 7% by mass, even when [P] is 0 or less, the viscosity is insufficient and bead meandering occurs.

In addition, components other than the above in the melted flux for submerged arc welding of the present invention are, for example, Na ₂ O, K ₂ O, B ₂ O ₃ , Cr ₂ O ₃ , V ₂ O ₅ , P, and S. .

Hereinafter, the effect of the Example of this invention is demonstrated compared with the comparative example which remove | deviates from the scope of the present invention. Fig.5 (a) is a schematic diagram which shows the electrode arrangement | positioning in 4 electrode welding, FIG.5 (b) is sectional drawing which shows the groove shape in that case. Moreover, Fig.6 (a) is a schematic diagram which shows the electrode arrangement | positioning in 3 electrode welding, FIG.6 (b) is sectional drawing which shows the groove shape in that case. First, as shown in FIG. 5 (b) and FIG. 6 (b), a pair of components having the composition shown in Table 1 below (JIS standard G3106 SM490A) with a plate thickness of 20 mm and an angle of the groove 12 of 70 °. The test steel plate 11 is made of a wire having a composition shown in Table 2 below (JIS standard Z3351 YS-S6, diameter 4.0 mm) and a flux having a composition shown in Tables 3 to 5 below. ) And the conditions shown in FIG. 6 (a), double-sided single-layer welding is performed by the multi-electrode submerged arc welding method, welding workability (bead meandering, pock mark, bead shape, slag seizure, shrinkage hole) and in the weld metal The amount of oxygen was evaluated. In this example, before welding by the above-described method, a wire of JIS standard Z3312 YGW11 (diameter: 1.2 mm) was used on the 2nd side of the test steel plate 11, the current was 260A, the voltage was 32V, The welding speed is 50 cm / min, and the shield gas is temporarily welded using CO ₂ . For this reason, the temporary welding part 13 is formed in the 2nd side of the obtained welded joint. Further, the remainder in Table 2 below is Fe and inevitable impurities, and “tr.” Indicates that it is below the detection limit. Furthermore, the balance in the following Tables 3 to 5 is oxygen contained in the Ca compound and Ba compound, components other than Ca and Ba contained in the F compound, Na ₂ O, K ₂ O, B ₂ O ₃ , Cr ₂ O _3. , V ₂ O ₅ , P, S and the like.

  The evaluation criteria for each item will be described below. In addition, the welding length of each test steel plate was 1.5 m, and when either one of the 1st side and the 2nd side did not satisfy the standard, it was set as x. For the bead meandering, the case where the runout width of the weld line was 3 mm or less was marked as ◯, and the case where the runout width of the weld line was greater than 3 mm was marked as x. Regarding the pock mark, the case where the number of pock marks per 1 m of weld length was 1 or less was marked with ○, and the case where there were more than 1 was marked with x. Regarding the bead shape, the case where the extra height was 3 mm or less was rated as “◯”, and the case where the extra height was over 3 mm was made “X”. For slag seizure, the seizure length at the toe end of the bead after slag peeling was 20% or less with respect to the weld length, and the case where the seizure length exceeded 20% was rated as x. In addition, the seizure of the bead toe portion was measured on both sides, and the longer one was regarded as the seizure length.

  As for the shrinkage hole, the case where no shrinkage hole was generated on the bead surface was marked with ◎, the case where the shrinkage hole on the bead surface was 10% or less with respect to the weld length, the shrinkage hole on the bead surface became the weld length. On the other hand, what exceeded 10% was set as x. FIG. 7 is a cross-sectional view showing the sampling position of the test piece for oxygen analysis in the weld metal. The amount of oxygen in the weld metal was evaluated by analyzing a specimen 15 from a weld metal 13 of a welded joint obtained by welding the test steel plate 11 using the fluxes of the present example and the comparative example. In addition, since the low-temperature toughness which was excellent if the oxygen content in a weld metal was 300 ppm or less was obtained, it was supposed that oxygen reduction was achieved. The above results are summarized in Table 7 and Table 8 below.

  No. shown in Table 3 above. 1 to No. 21 and no. 61 thru | or No. No. 64 flux is an example of the present invention. 22 thru | or No. 60 and no. 65 thru | or No. 67 is a comparative example. In addition, No. 20, no. 21, no. 42 and no. For the flux of 43, three-electrode welding shown in FIGS. 6A and 6B was performed, and for the other cases, four-electrode welding shown in FIGS. 5A and 5B was performed.

As shown in Table 7 above, Example No. which is within the scope of the present invention. 1 to No. 21 and no. 61 thru | or No. The flux of 64 had good welding workability, and the amount of oxygen in the weld metal was 300 ppm or less. On the other hand, as shown in Table 8 above, Comparative Example No. deviated from the scope of the present invention. Since the flux of No. 22 had a SiO ₂ content of less than 23% by mass, bead meandering occurred. Comparative Example No. The flux of No. 23 had a SiO ₂ content of more than 33% by mass and a Ca content of less than 5% by mass, so that the bead shape became convex and shrinkage holes were generated. Comparative Example No. Since the flux of 24 had [P] larger than 0, bead meandering occurred. Comparative Example No. Since the flux of No. 25 had an MgO content exceeding 18% by mass, a pock mark was generated.

Comparative Example No. Since the flux of No. 26 had an Al ₂ O ₃ content of less than 1% by mass, bead meandering occurred. Comparative Example No. Since the flux of No. 27 had an Al ₂ O ₃ content exceeding 13% by mass, the bead shape became convex. Comparative Example No. In the flux No. 28, since the MnO content was less than 1% by mass, shrinkage holes were generated. Comparative Example No. In the flux No. 29, since the MnO content exceeds 9 mass%, the bead shape became convex and slag seizure occurred. Comparative Example No. Since the flux of 30 had a TiO ₂ content exceeding 8% by mass, seizure of slag occurred. Comparative Example No. Since the flux of No. 31 had a ZrO ₂ content of less than 0.5% by mass, bead meandering occurred. Comparative Example No. Since the flux of No. 32 has a ZrO ₂ content exceeding 5.0 mass%, slag seizure occurred. Comparative Example No. In the flux No. 33, since the FeO content was less than 0.5% by mass, shrinkage holes were generated. Comparative Example No. In No. 34, since the FeO content exceeded 5.0 mass%, slag seizure occurred.

  Comparative Example No. In the flux No. 35, the amount of Ca compound was less than 5% by mass, so that shrinkage holes were generated. Comparative Example No. As for the flux of 36, since the Ca compound amount exceeded 25 mass%, a pock mark was generated. Comparative Example No. Since the F compound content of the flux of 37 was less than 1% by mass, the bead shape became convex. Comparative Example No. In the flux No. 38, the F compound content exceeded 14% by mass, and therefore bead meandering and shrinkage holes were generated. Comparative Example No. In the flux No. 39, the Ba compound content was less than 5% by mass, so that shrinkage holes were generated. Comparative Example No. In the flux No. 40, the Ba compound content exceeded 35% by mass, and the total content of Ca compound and Ba compound exceeded 40% by mass. Therefore, bead meandering occurred and a pock mark was generated. Comparative Example No. In the flux No. 41, since the total content of the Ca compound and the Ba compound exceeded 40% by mass, bead meandering occurred and a pock mark was generated.

Comparative Example No. 42, no. 44 thru | or No. Since the flux of 50 had [N] of 0 or less, shrinkage holes were generated. Comparative Example No. In the flux of 43, [P] was larger than 0 and [N] was 0 or less, so that bead meandering and shrinkage holes were generated. Comparative Example No. 51, no. 53 and no. In the flux of 60, since [M] exceeded 300, the amount of oxygen in the weld metal exceeded 300 ppm. Comparative Example No. 52 and no. In the flux No. 54, since [M] exceeds 300 and the Al ₂ O ₃ content exceeds 13% by mass, the oxygen content in the weld metal exceeds 300 ppm, and the bead shape becomes convex. It was. Comparative Example No. In the flux of 55, [M] exceeds 300, Al ₂ O ₃ content exceeds 13% by mass, MnO content exceeds 9% by mass, and ZrO ₂ content is less than 0.5% by mass. The oxygen content in the weld metal exceeded 300 ppm, the bead shape became convex, and bead meandering and slag seizure occurred. Comparative Example No. In the flux of 56, [M] exceeds 300, the SiO ₂ content exceeds 33% by mass, the Al ₂ O ₃ content exceeds 13% by mass, and the ZrO ₂ content is less than 0.5% by mass. For this reason, the amount of oxygen in the weld metal exceeded 300 ppm, and the bead shape became convex and bead meandering occurred.

Comparative Example No. 57 and no. In the flux No. 58, [M] exceeded 300 and the ZrO ₂ content was less than 0.5% by mass. Therefore, the oxygen content in the weld metal exceeded 300 ppm, and bead meandering occurred. Comparative Example No. 59 flux is greater than 300 [M], it exceeds the 33 wt% SiO2 content, since the content of ZrO ₂ is less than 0.5 wt%, greater than 300ppm oxygen content in the weld metal, and further The bead shape became convex and bead meandering occurred. Comparative Example No. 55 to No. In the flux No. 59, no shrinkage hole was generated even though the content of the Ba compound was less than 5% by mass. This is because [M] exceeds 300, the oxygen content in the weld metal exceeds 300 ppm, and the surface tension of the molten metal is lowered.

  Comparative Example No. Since the flux of 65 had an MgO content of less than 7% by mass, bead meandering occurred. Comparative Example No. The flux No. 66 had a MgO content of less than 7% by mass, and [P] was greater than 0, and therefore bead meandering occurred. Comparative Example No. In the flux No. 67, since [P] was larger than 0, bead meandering occurred.

FIG. 5 is a graph showing the relationship between [M] and the amount of oxygen in the weld metal, with [M] on the horizontal axis and the amount of oxygen in the weld metal on the vertical axis. (A) is a top view which shows typically the shape of the weld metal and molten pool in high-speed welding, (b) is a top view which shows typically the shape of the weld metal and molten pool in low-speed welding. It is a graph which shows the relationship between the total content of Ca compound and Ba compound, and F compound content, taking the total content of Ca compound and Ba compound on a horizontal axis, and taking F compound content on a vertical axis | shaft. It is a graph which shows the relationship between MgO content and Ca compound content, taking MgO content on a horizontal axis and taking Ca compound content on a vertical axis. (A) is a schematic diagram which shows the electrode arrangement | positioning in 4 electrode welding, (b) is sectional drawing which shows a groove shape. (A) is a schematic diagram which shows the electrode arrangement | positioning in 3 electrode welding, (b) is sectional drawing which shows a groove shape. It is sectional drawing which shows the extraction | collection position of the test piece for the oxygen analysis in a weld metal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Weld metal 2; Columnar crystal 3; Molten pool 4; Shrinkage hole 11; Test steel plate 12; Groove 13; Temporary weld 14; Weld metal 15;

Claims (1)

Based on the total mass of the flux, SiO ₂ : 23 to 33% by mass, Ca compound: 5 to 25% by mass in terms of Ca, Ba compound: 5 to 35% by mass in terms of Ba, F compound: 1 to 14% by mass in terms of F, MgO: 7 to 18% by mass, Al ₂ O ₃ : 1 to 13% by mass, MnO: 1 to 9% by mass, ZrO ₂ : 0.5 to 5.0% by mass, FeO: 0.5 to 5.0% by mass %, TiO ₂ : 8 mass% or less, Ca compound and Ba compound: 40 mass% or less in total, SiO ₂ content (mass%) is [SiO ₂ ], Ca equivalent content of Ca compound [Ca], the Ba equivalent content (mass%) of the Ba compound [Ba], the F equivalent content (mass%) of the F compound [F], and the MgO content (mass%) [ MgO], the content of _Al 2 _{O 3 [Al 2 O} 3], nO content (mass%) [MnO], ZrO ₂ content (wt%) _[ZrO 2], FeO content (mass%) [FeO], TiO ₂ content (mass%) of [TiO ₂ ], [M] given by the following formula is 300 or less, [N] given by the following formula is larger than 0, and [P] given by the following formula is 0 or less. Fused flux for submerged arc welding.

Images