JP2016140889A - Flux for submerged arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flux for submerged arc welding exerting favorable welding workability even in any case of AC or DC arc welding and capable of reducing the moisture absorption amount of a flux and a diffusible hydrogen amount in a weld metal.SOLUTION: A flux for submerged arc welding contains by mass, 25-35% of MgO, 15-35% of F in terms of CaF, 10-25% of AlO, 10-20% of SiO, 0.5-6.5% of total of at least one of Na in terms of NaO, K in terms of KO and Li in terms of LiO, 0.5-5% of Fe in terms of FeO, 1-5% of TiO, 6% or less of CaO, less than 2.0% of Mn in terms of MnO, 1.0% or less of water-soluble SiO, 1.0% or less of water-soluble NaO and 0.8% or less of water-soluble KO, and has a composition satisfying the following expression (I).SELECTED DRAWING: None

Description

  The present invention relates to a flux used for submerged arc welding, and more particularly to a flux for submerged arc welding which is a high-temperature firing type flux.

  The flux used for submerged arc welding is roughly classified into a melt-type flux and a fired-type flux according to its form. The melt-type flux is produced by melting and pulverizing various raw materials in an electric furnace or the like. On the other hand, the calcining flux is produced by combining various raw materials with a binder such as alkali silicate, granulating, and then calcining.

The calcining type flux is classified according to the calcining temperature, and generally, the calcined one at 400 ° C. or more and less than 600 ° C. is called the low temperature calcining flux, and the one calcined at 600 to 1200 ° C. is called the high temperature calcining flux. In the low-temperature fired flux, various studies have been made in order to reduce the diffusion of hydrogen into the weld metal (see Patent Documents 1 to 3). For example, Patent Documents 1 to 3 disclose a technique for reducing the H ₂ partial pressure by generating CO ₂ gas during welding by setting the ratio of carbonate in the flux to a specific range.

  In addition, in order to improve moisture absorption characteristics without using carbonates, the A value that is a characteristic value mainly derived from the flux component and the maximum value of the specific surface area of the flux are specified, and the amount of hydrogen in the weld metal is reduced. A technique for reducing this has also been proposed (see Patent Document 4). On the other hand, for high-temperature fired fluxes, for example, a technique for reducing the amount of diffused hydrogen by specifying the types and contents of basic oxides, alkali metal fluorides, acidic oxides, and the like has been proposed ( (See Patent Document 5).

JP-A-49-70839 JP-A-53-95144 Japanese Patent Laid-Open No. 51-87444 JP-A-9-99392 JP-A-62-68695

However, the technology for improving the moisture absorption characteristics and the technology for reducing the amount of diffused hydrogen in the calcined flux described above have the following problems. First, the low-temperature firing type flux added with the carbonate described in Patent Documents 1 to 3 increases the amount of flux consumed when a DC welding power source is used, compared with the case where an AC welding power source is used. Further decomposition of carbonate is promoted, and a large amount of CO gas and CO ₂ gas is generated during welding. Therefore, there is room for improvement in terms of bead surface roughness, generation of pock marks, bead appearance, and bead shape due to generation of CO gas and CO ₂ gas.

  In the technique described in Patent Document 4, MnO is regarded as a hydratable component in the A value that is an index indicating hydration, but MnO is non-hydratable in combination with other flux components. Can also be an ingredient. In the technique described in Patent Document 4, the specific surface area is reduced, but the specific surface area of the flux greatly affects the shielding performance of the slag during welding. Specifically, when the specific surface area of the flux is reduced, the shielding property of the slag is impaired, the amount of nitrogen in the weld metal is increased, and the toughness of the weld metal is deteriorated.

  On the other hand, the technology described in Patent Document 5 relating to the high-temperature firing type flux is designed with a flux component mainly intended for use with an AC welding power source, and welding workability that is most concerned when a DC welding power source is used. Deterioration of is not considered. That is, the flux described in Patent Document 5 cannot obtain the same effect as when the AC type is used when the DC type is used for the welding power source.

  Therefore, the present invention has good welding workability regardless of whether the welding power source is an AC type or a DC type, and can reduce the moisture absorption amount of flux and the amount of diffusible hydrogen in the weld metal. It is an object to provide a flux for submerged arc welding.

The flux for submerged arc welding according to the present invention is MgO: 25 to 35% by mass, F CaF ₂ conversion value: 15 to 35% by mass, Al ₂ O ₃ : 10 to 25% by mass, SiO ₂ : 10 to 20% by mass. %, Na ₂ O conversion value of Na, at least one total of Li ₂ O conversion value of _{K 2} O conversion value and Li of K: 0.5 to 6.5 wt%, FeO converted value of Fe: 0.5-5 _wt%, TiO 2: 1 to 5 wt%, CaO: 6 wt% or less, MnO conversion value of Mn: less than 2.0 wt%, water-soluble _SiO 2: 1.0 wt% or less, water sex _Na 2 O: 1.0 wt% or less, soluble _K 2 O: containing 0.8 wt% or less, wherein the MgO content [MgO], the _Al 2 _{O 3} content _[Al 2 _{O 3} ], the content by CaF ₂ converted value of the F _[CaF 2], wherein the TiO ₂ When chromatic amount and [TiO _2], and satisfies the following formula (I).

According to such a configuration, the flux contains a predetermined amount of a predetermined component and satisfies the mathematical formula (I), so that welding workability is good regardless of whether the welding power source is an AC type or a DC type. Become. Further, the moisture absorption amount of the flux and the amount of diffusible hydrogen in the weld metal are reduced.
In addition, the welding workability | operativity in this application means the quality of a bead appearance and a bead shape, slag peelability, arc stability, the defect resistance of a weld metal, and the impact resistance (toughness) of a weld metal.

This flux for submerged arc welding preferably further contains water-soluble Li ₂ O: 0.3% by mass or less.
According to such a configuration, the moisture absorption characteristics of the flux are improved.

In the flux for submerged arc welding of the present invention, the C content may be regulated to 0.2% by mass or less.
According to such a configuration, welding workability is improved.

  Moreover, the flux for submerged arc welding of this invention is baked at 800 degreeC or more, for example.

According to the present invention, the content of each component is specified, and the ratio of the MgO content and the total content of Al ₂ O ₃ , F, and TiO ₂ is in a specific range, so the welding power source is AC Regardless of the type and the direct current type, the welding workability is good, and the moisture absorption amount of the flux and the amount of diffusible hydrogen in the weld metal can be reduced.

It is a side view which shows the groove shape of the test piece used by the welding test of the Example.

  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.

In order to solve the above-described problems, the present inventor has conducted extensive experiments and has obtained the following knowledge. When a direct current welding power source is used, the amount of SiO _{2 in} the flux should be reduced as much as possible in order to maintain good slag removability. Moreover, about MgO, unless the addition amount is increased compared with the flux described in Patent Document 5, the slag peelability cannot be improved.

Therefore, in the flux for submerged arc welding according to the embodiment of the present invention (hereinafter also simply referred to as flux), the SiO ₂ content is 10 to 20% by mass, the MgO content is 25 to 35% by mass, and water-soluble. SiO ₂ is 1.0% by mass or less. In the flux of the present embodiment, the MgO content is [MgO], the Al ₂ O ₃ content is [Al ₂ O ₃ ], the F content in terms of CaF ₂ is [CaF ₂ ], and TiO ₂ content is included. When the amount is [TiO ₂ ], each component is adjusted so as to satisfy the following formula (I).

In the flux of the present embodiment, the content of F in terms of CaF ₂ , the content of Al ₂ O ₃ , the value of Na in terms of Na ₂ O, the value of K in terms of K ₂ O, and the value of Li in terms of Li ₂ O The total content of Fe, the content of Fe in terms of FeO, the content of TiO _{2, the} content of CaO, the content of Mn in terms of the value of MnO, the content of water-soluble Na ₂ O, the content of water-soluble K ₂ O Is stipulated.

  Hereinafter, the reasons for limiting the composition of the flux of this embodiment will be described. In addition, content of each component in the flux of this embodiment is the conversion value which converted the value quantified by the method prescribed | regulated to JISZ3352: 2010 into oxide or fluoride unless there is particular notice. Moreover, content of each component is content about the whole flux.

[MgO: 25 to 35% by mass]
MgO is a component that greatly contributes to the improvement of slag peelability, and is an essential component for ensuring good slag peelability regardless of the method of the welding power source. However, when the MgO content is less than 25% by mass, the effect of improving the slag releasability cannot be sufficiently obtained. When the MgO content exceeds 35% by mass, the bead shape deteriorates, and the slag depends on the type of the welding power source. Defects such as entanglement, poor fusion, and undercut are likely to occur. In particular, in the AC welding power source, the occurrence of welding defects such as slag entrainment and poor melting described above becomes significant. Therefore, MgO content shall be 25-35 mass%.

The MgO content is preferably 27% by mass or more, more preferably 29% by mass or more, from the viewpoint of improving slag peelability. Moreover, from a viewpoint of suppression of defect generation, the content is preferably 33% by mass or less, and more preferably 31% by mass or less. In addition, MgO content here is the value which converted the total Mg amount of the flux obtained by analyzing by the method (for example, JISM8222: 1997 etc.) prescribed | regulated to JISZ3352: 2010 converted into MgO. The total Mg amount measured by this method may include components other than MgO, such as MgF ₂ , but since these components are in minute amounts, the MgO content (the MgO equivalent value of the total Mg amount) is as described above. If it is within the range, the effect of MgO described above is not affected.

[F converted to CaF ₂ : 15 to 35% by mass]
Fluorides such as CaF ₂ have an effect of increasing the electrical conductivity and fluidity of molten slag, and are one of the components that affect the high temperature viscosity of molten slag. This effect is proportional to the content, as is the case with CaO described later. Specifically, when the F content (CaF ₂ equivalent value) is less than 15% by mass, the above-described effects cannot be obtained sufficiently, and the discharge of CO gas from the molten slag is promoted, and the pock mark resistance is improved. The improvement effect cannot be expected.

On the other hand, when the F content (CaF ₂ conversion value) exceeds 35 wt%, too high fluidity of the molten slag, bead shape is deteriorated. Therefore, F content (CaF ₂ conversion value) is 15 to 35 mass%. The F content (CaF ₂ equivalent value) is preferably 20% by mass or more, more preferably 23% by mass or more, from the viewpoint of improving the pock mark resistance. From the viewpoint of improving the bead shape, the F content (CaF ₂ equivalent value) is preferably 33% by mass or less, and more preferably 30% by mass or less.

Incidentally, F content referred to here, JIS Z 3352: the method specified in 2010 (e.g., JIS K 1468-2: 1999, etc.) the total F content of the flux obtained was analyzed by and translated at CaF ₂ value It is. Further, the fluoride component in the flux of the present embodiment is mainly a CaF _2, but may be included, such as AlF ₃ and MgF ₂ and other, F content (CaF ₂ converted value of the total F content) is If it is in the above-mentioned range, it does not affect the effect of the above-mentioned fluoride.

[Al ₂ O ₃ : 10 to 25% by mass]
Al ₂ O ₃ is a component that adjusts the viscosity and melting point of the molten slag, and has the effect of improving the bead shape during welding. However, when the Al ₂ O ₃ content is less than 10% by mass, the above-described effects cannot be obtained sufficiently, and when the Al ₂ O ₃ content exceeds 25% by mass, the melting point of the molten slag increases. It is too much and causes bead shape deterioration at the time of welding. Therefore, the Al ₂ O ₃ content is 10 to 25% by mass.

The content of Al ₂ O ₃ is preferably 15% by mass or more, more preferably 17% by mass or more, from the viewpoint of adjusting the viscosity and melting point of the molten slag. Moreover, from the viewpoint of the melting point of the molten slag, the Al ₂ O ₃ content is preferably 22% by mass or less, more preferably 20% by mass or less. Thereby, the bead shape can be further improved.

Incidentally, _Al 2 _{O 3} content as referred to herein, JIS Z 3352: the method specified in 2010 (e.g., JIS M 8220: 1995, etc.) The total Al content of the flux obtained by analyzing, in _Al 2 _{O 3} It is a converted value. The total Al amount is measured by this method, but may be included other than _Al 2 _{O 3} component, such as AlF _3, since these components is very small, _Al 2 _{O 3} content (total amount of Al If the Al ₂ O ₃ conversion value) is within the above-described range, the above-described effect of Al ₂ O ₃ is not affected.

[SiO ₂ : 10 to 20% by mass]
SiO ₂ has an effect of mainly improving the bead appearance and bead shape by imparting an appropriate viscosity to the molten slag. However, when the SiO ₂ content is less than 10% by mass, the above-described effects cannot be obtained sufficiently, and the bead appearance and the bead shape deteriorate. Further, when the content of SiO ₂ exceeds 20 wt%, the slag viscosity becomes excessive, with the slag removability is deteriorated, with the slag burn becomes severe. Thus, SiO ₂ content is 10 to 20 mass%.

From the viewpoint of improving the appearance of the bead and the bead shape, the SiO ₂ content is preferably 13% by mass or more, and more preferably 15% by mass or more. Moreover, from the viewpoint of optimizing the viscosity of the molten slag, the SiO ₂ content is preferably 18% by mass or less.

Incidentally, SiO ₂ content herein is, JIS Z 3352: the method specified in 2010 (e.g., JIS M 8214: 1995, etc.) the total amount of Si of the flux obtained by analyzing, in value converted by SiO ₂ is there. The total amount of Si measured by this method includes components other than SiO ₂ such as Si added as an alloy such as Fe—Si, but the SiO ₂ content (total Si amount converted to SiO ₂ ) is If it is within the above-mentioned range, the above-mentioned effect of SiO ₂ is not affected.

[Total of at least one of Na converted to Na ₂ O, K converted to K ₂ O, and Li converted to Li ₂ O: 0.5 to 6.5% by mass]
Na, K and Li are components that mainly affect the arc stability during welding and the moisture absorption characteristics of the flux, and are mainly added in the form of oxides such as Na ₂ O, K ₂ O and Li ₂ O. Is done. However, when the Na content (Na ₂ O conversion value), K content (K ₂ O conversion value), and Li (Li ₂ O conversion value) are less than 0.5 mass% in total, the arc voltage during welding is It becomes unstable and the bead appearance and bead shape deteriorate.

On the other hand, if the Na content (Na ₂ O conversion value), K content (K ₂ O conversion value) and Li (Li ₂ O conversion value) exceed 6.5 mass% in total, the moisture absorption characteristics of the flux deteriorate. In addition, the arc becomes too strong and unstable, and the bead appearance and bead shape deteriorate. Thus, Na content (Na ₂ O conversion value), K content _{(K 2} O conversion value) and Li (Li ₂ O conversion value) shall be 0.5 to 6.5 mass% in total. In addition, the flux of this embodiment should just add at least 1 type among Na, K, and Li.

Na content (Na ₂ O conversion value), K content (K ₂ O conversion value) and Li (Li ₂ O conversion value) are 1.5% by mass or more in total from the viewpoint of stabilization of the arc voltage. It is preferable that there is more preferably 2.0% by mass or more. Further, from the viewpoint of the moisture absorption characteristics of the flux and the arc stability, the Na content (Na ₂ O equivalent), the K content (K ₂ O equivalent) and Li (Li ₂ O equivalent) are 5. It is preferable that it is 5 mass% or less, More preferably, it is 4.5 mass% or less.

The Na content, the K content, and the Li content mentioned here are the total Na content of the flux obtained by analysis by the method defined in JIS Z 3352: 2010 (for example, JIS M 8852: 1998). the K amount and the total amount of Li, respectively NaO, value converted by the _{K 2} O and Li ₂ O. Further, the Na component, K component, and Li component in the flux of the present embodiment are mainly Na ₂ O, K ₂ O, and Li ₂ O, but in addition, NaAlSi ₃ O ₈ , KAlSi ₃ O _8, and LiAlSi ₃ O are used. ₈ may be included.
Moreover, Na, K, and Li here are derived from an ore raw material and water glass.

[Fe converted to FeO: 0.5 to 5% by mass]
Fe has the effect of promoting the deoxidation phenomenon and improving the pock mark resistance, and is added mainly in the form of metal powder such as Fe-Si. The above-described effect is proportional to the abundance thereof, and when the Fe content (FeO equivalent value) is less than 0.5 mass%, particularly when the welding power source is a direct current type, a sufficient effect cannot be obtained. On the other hand, if the Fe content (FeO equivalent) exceeds 5% by mass, the solidification temperature of the slag is affected, and the bead appearance, bead shape and slag peeling are deteriorated. Therefore, Fe content (FeO conversion value) shall be 0.5-5 mass%.

  The Fe content (FeO equivalent value) is preferably 1% by mass or more, more preferably 1.5% by mass or more, from the viewpoint of the pock mark resistance. In consideration of the influence of the slag on the solidification temperature, the Fe content (FeO equivalent value) is preferably 4% by mass or less, more preferably 3% by mass or less.

In addition, Fe content here is the value which converted the total Fe amount of the flux obtained by analyzing by the method (for example, JIS M8202: 2000 etc.) prescribed | regulated to JISZ3352: 2010, and converted with FeO, In addition to Fe added as a metal powder, FeO, Fe ₂ O ₃ and Fe ₃ O ₄ added as inevitable impurities may be included.

[TiO ₂ : 1 to 5% by mass]
TiO ₂ is an effective component for improving slag removability, and has an effect of adjusting the bead shape well. Part of the TiO _2, Ti next by a reduction reaction at the time of welding, the Ti is added in the weld metal, which contributes to improving toughness. The above-described action is proportional to its abundance (TiO ₂ content). However, if the upper limit of the TiO ₂ content exceeds 5% by mass, the bead shape deteriorates. Further, if the content of TiO ₂ is less than 1 wt%, slag removability and bead shape is deteriorated. Further, the effect of improving toughness is small. Therefore, the TiO ₂ content is 1 to 5% by mass.

The TiO ₂ content is preferably 1.5% by mass or more, more preferably 2.0% by mass or more, from the viewpoints of slag peelability, bead shape, and toughness. The TiO ₂ content is preferably 4.0% by mass or less, more preferably 3.0% by mass or less from the viewpoint of the bead shape.

Incidentally, TiO ₂ content herein is, JIS Z 3352: the method specified in 2010 (e.g., JIS M 8219: 2012, etc.) the total amount of Ti flux obtained by analyzing, in value converted by TiO ₂ is there.

[CaO conversion value: 6 mass% or less]
CaO is a component that increases the cleanliness of the weld metal by increasing the basicity of the slag, and also affects the fluidity of the molten slag, and the effects described above are exhibited in proportion to the amount of the CaO. However, when the CaO content exceeds 6% by mass, the fluidity of the molten slag becomes excessive, and the appearance and shape of the bead deteriorate. Therefore, the CaO content is regulated to 6% by mass or less. The CaO content is preferably 4% by mass or less, more preferably 2% by mass or less, from the viewpoint of molten slag fluidity. Moreover, from a viewpoint of the cleanliness improvement of a weld metal, Preferably it is 0.5 mass% or more.

Note that the flux of the present embodiment, in addition to CaO as Ca components include CaF ₂ described above. For this reason, CaO content here is a conversion value calculated | required from the total Ca amount and the total F amount which were obtained by analyzing by the method prescribed | regulated to JISZ3352: 2010. Therefore, when the amount of CaF ₂ is large, there is a case where CaO becomes 0 according to JIS Z 3352: 2010.

[Mn converted to MnO: less than 2.0% by mass]
Mn affects the viscosity of the molten slag and the solidification temperature, and is an effective component for improving the pock mark resistance. However, as a result of various experimental studies by the inventor within the scope of the present invention, it has been confirmed that the oxygen content in the weld metal tends to increase as the amount of Mn added increases. Since the increase in the amount of oxygen in the weld metal is one of the causes for the deterioration of toughness, the toughness of the weld metal deteriorates when the Mn content (MnO conversion value) is 2.0 mass% or more. Therefore, in the flux of the present embodiment, Mn is used as a regulating component, and the content thereof is regulated to 2.0% by mass or less in terms of MnO. The Mn content (MnO equivalent) is preferably 1.8% by mass or less, more preferably 1.5% by mass or less, from the viewpoint of improving the toughness of the weld metal.

  In addition, Mn contained in the flux of this embodiment is mixed from a raw material as an unavoidable impurity. And Mn content here is the value which converted the total Mn amount of the flux obtained by analyzing by the method (for example, JISM8232: 2005 etc.) prescribed | regulated to JISZ3352: 2010 converted into MnO.

[Water-soluble SiO ₂ : 1.0% by mass or less]
Water-soluble SiO ₂ is regulated so as to be 1.0% by mass or less after performing the sintering operation in order to prevent deterioration of moisture absorption resistance of the flux and suppress an increase in the amount of diffusible hydrogen in the weld metal. When the content of the water-soluble SiO ₂ exceeds 1.0% by mass, the moisture absorption resistance of the flux deteriorates and the diffusion hydrogen amount of the weld metal increases. Therefore, the water-soluble SiO ₂ content is 1.0% by mass or less.

The water-soluble SiO ₂ content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, from the viewpoint of welding workability. Further, from the viewpoint of improving moisture absorption resistance and reducing the amount of diffused hydrogen, the content is preferably 0.8% by mass or less, and more preferably 0.6% by mass or less.

This water-soluble SiO ₂ is mainly derived from a binder such as water glass, and in order to reduce the amount, it is effective to sinter the flux at a temperature higher than the temperature at which the binder hardly absorbs moisture. Specifically, the firing temperature is particularly preferably 800 ° C. or higher. The content of the water-soluble SiO ₂ can be controlled mainly by adjusting the components and content of the water glass and the firing temperature.

The amount of water-soluble SiO ₂ in the flux can be measured by the following method. First, the flux is pulverized to a particle size of 300 μm or less by a vibration mill, and about 0.2 g of a measurement sample is collected therefrom (step 1). Next, the sample mentioned above and 100 ml of distilled water were put into a quartz Erlenmeyer flask, and a soluble component was extracted for 4 hours under boiling (step 2). Thereafter, the extract was allowed to stand for 12 hours or more, and then precipitates and suspended matters in the extract were removed, and Si was quantified by absorptiometry (step 3).

Incidentally, the water-soluble SiO ₂ referred to herein is the total amount of Si of the flux obtained was analyzed by the method described above, a value obtained by converting at SiO _2, separately from the total SiO ₂ described above, the content thereof I have identified.

[Water-soluble Na ₂ O: 1.0% by mass or less]
Water-soluble Na ₂ O is regulated to be 1.0% by mass or less after the sintering operation in order to prevent deterioration of moisture absorption resistance of the flux and suppress an increase in the amount of diffusible hydrogen in the weld metal. . When the content of the water-soluble Na ₂ O exceeds 1.0% by mass, the moisture absorption resistance of the flux deteriorates and the diffusion hydrogen amount of the weld metal increases. Therefore, the water-soluble Na ₂ O content is 1.0% by mass or less.

The water-soluble Na ₂ O content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more from the viewpoint of welding workability. Further, from the viewpoint of improving moisture absorption resistance and reducing the amount of diffused hydrogen, the content is preferably 0.8% by mass or less, and more preferably 0.5% by mass or less.

This water-soluble Na ₂ O is mainly derived from a binder such as water glass, and in order to reduce the amount, it is effective to sinter the flux at a temperature higher than the temperature at which the binder hardly absorbs moisture. Specifically, the firing temperature is particularly preferably 800 ° C. or higher. The content of water-soluble Na ₂ O can be controlled mainly by adjusting the components and content of water glass and the firing temperature.

In addition, the amount of water-soluble Na ₂ O in the flux can be quantified by absorptiometry as in the measurement of the amount of water-soluble SiO ₂ described above.
Herein, the term water-soluble Na 2 _O is the total amount of Na of the flux obtained was analyzed by the method described above, a value obtained by converting at Na 2 _O, and distinguished from the total Na 2 _O as described above, the The content is specified.

[Water-soluble K ₂ O: 0.8% by mass or less]
The present inventor has found that addition of an appropriate amount of water-soluble K ₂ O to water glass has an effect of lowering the moisture absorption temperature of water glass. That is, in a flux that was sintered at 800 ° C. or higher using water glass to which an appropriate amount of water-soluble K ₂ O was added, the amount of water-soluble K ₂ O satisfied the control range of 0.8% by mass or less. In this case, the moisture absorption resistance of the flux is greatly improved as compared with the conventional case.
Water-soluble K ₂ O is regulated to be 0.8% by mass or less after performing the sintering operation in order to prevent the moisture absorption resistance of the flux from being deteriorated and to suppress an increase in the amount of diffusible hydrogen in the weld metal. . When the content of water-soluble K ₂ O exceeds 0.8% by mass, the moisture absorption resistance of the flux deteriorates and the diffusion hydrogen amount of the weld metal increases. Therefore, the water-soluble K ₂ O content is 0.8% by mass or less.

The water-soluble K ₂ O content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, from the viewpoint of welding workability. Moreover, it is preferable that it is 0.6 mass% or less from a viewpoint of a moisture absorption improvement and the amount of diffusion hydrogen reduction, More preferably, it is 0.4 mass% or less.

This water-soluble K ₂ O is mainly derived from a binder such as water glass, and in order to reduce the amount, it is effective to sinter the flux at a temperature higher than the temperature at which the binder hardly absorbs moisture. Specifically, the firing temperature is particularly preferably 800 ° C. or higher. The content of water-soluble K ₂ O can be controlled mainly by adjusting the components and content of water glass and the firing temperature.

In addition, the amount of water-soluble K ₂ O in the flux can be quantified by absorptiometry as in the measurement of the amount of water-soluble SiO ₂ described above.
Herein, the term water-soluble K _{2 O} is, the total amount of K of the flux obtained was analyzed by the method described above, a value obtained by converting at K 2 _O, and distinguished from all K _{2 O} as described above, the The content is specified.

The flux of this embodiment may contain water-soluble Li ₂ O in addition to the components described above.
[Water-soluble Li ₂ O: 0.3% by mass or less]
Water-soluble Li ₂ O has the effect of further improving the hygroscopic properties depending on the amount added. However, when the water-soluble Li ₂ O content exceeds 0.3% by mass after the sintering operation is performed, the arc stability is deteriorated, and the bead appearance and the bead shape are deteriorated. Accordingly, when adding water-soluble Li ₂ O is, a 0.3 mass% or less. The water-soluble Li ₂ O content is preferably 0.2% by mass or less, more preferably 0.15% by mass or less, from the viewpoint of improving arc stability and improving the bead appearance and bead shape. . Moreover, from a viewpoint of a hygroscopic characteristic, More preferably, it is 0.05 mass% or more.

This water-soluble Li ₂ O is mainly derived from a binder such as water glass, and in order to reduce the amount, it is effective to sinter the flux at a temperature higher than the temperature at which the binder hardly absorbs moisture. Specifically, the firing temperature is particularly preferably 800 ° C. or higher. The content of water-soluble Li ₂ O can be controlled mainly by adjusting the components and content of water glass and the firing temperature.

In addition, the amount of water-soluble Li ₂ O in the flux can be quantified by absorptiometry as in the above-described measurement of the amount of water-soluble SiO ₂ .
Herein, the term water-soluble Li 2 _O is a total Li content of the flux obtained was analyzed by the method described above, a value obtained by converting at Li 2 _O, and distinguished from the total Li 2 _O as described above, the The content is specified.

[[MgO] / ([Al ₂ O ₃ ] + [CaF ₂ ] + [TiO ₂ ]): 0.50 to 1.10]
The contents of MgO, Al ₂ O ₃ , F and TiO ₂ are individually specified, but in the flux of this embodiment, the MgO content (% by mass) and the Al ₂ O ₃ content are further increased. (Mass%), F content (CaF ₂ equivalent value) (mass%) and ratio with the total amount of TiO ₂ content (mass%) (= [MgO] / ([Al ₂ O ₃ ] + [CaF ₂ ] + [TiO ₂ ])).

As a result of various experimental studies on the moisture absorption characteristics and welding workability of the flux added with MgO, the present inventor has found MgO content, Al ₂ O ₃ content, F content (CaF ₂ equivalent value), and TiO ₂ content. It was found that the ratio to the total amount (= [MgO] / ([Al ₂ O ₃ ] + [CaF ₂ ] + [TiO ₂ ])) has a great influence on the moisture absorption characteristics and welding workability. For example, when a DC welding power source is used, the flux consumption increases compared to when an AC welding power source is used. For this reason, Si in the weld metal increases and the deterioration of the slag peelability becomes remarkable, but the slag peelability can be improved by adding MgO.

However, since MgO is rich in hydration properties, when it is added to the flux, the hygroscopic property deteriorates and the amount of diffusible hydrogen in the weld metal increases. On the other hand, Al ₂ O ₃ , F and TiO ₂ are non-hydratable components, and the effect of improving the moisture absorption characteristics by addition is remarkable. Among these, F, when used in combination with Al ₂ O ₃ and TiO ₂ , has the effect of improving the moisture absorption characteristics of the flux and contributing to the reduction of the amount of diffusible hydrogen, unlike conventional knowledge. I understood it.

However, when [MgO] / ([Al ₂ O ₃ ] + [CaF ₂ ] + [TiO ₂ ]) is less than 0.50, the slag peelability is significantly deteriorated when welding with a DC welding power source. To do. On the other hand, when [MgO] / ([Al ₂ O ₃ ] + [CaF ₂ ] + [TiO ₂ ]) exceeds 1.10, the hygroscopic property deteriorates and the amount of diffusible hydrogen in the weld metal increases. Therefore, the addition amount of each component is adjusted so that [MgO] / ([Al ₂ O ₃ ] + [CaF ₂ ] + [TiO ₂ ]) is 0.50 to 1.10. Thereby, deterioration of a moisture absorption characteristic can be suppressed.

[MgO] / ([Al ₂ O ₃ ] + [CaF ₂ ] + [TiO ₂ ]) is preferably 0.55 or more, more preferably 0.60 or more, from the viewpoint of improving slag removability. is there. Moreover, it is preferable that it is 1.0 or less from a viewpoint of a moisture absorption improvement and the amount of diffusion hydrogen reduction, More preferably, it is 0.9 or less.

[C: 0.2% by mass or less]
C originates from carbonates contained as impurities in each raw material of the flux, and is unavoidably introduced. On the other hand, when a DC welding power source is used as described above, the flux consumption is increased, and the decomposition of carbonate is further promoted as compared with the case where an AC welding power source is used. For this reason, even if the C content is very small, a large amount of CO or CO ₂ gas is generated during welding, leading to deterioration of the pock mark resistance and the appearance and shape of the bead. Therefore, in order to prevent deterioration in welding workability, the C content in the flux is preferably reduced to 0.2% by mass or less.

  The C content is preferably regulated to 0.1% by mass or less, more preferably 0.05% by mass or less, particularly from the viewpoint of improving the pock mark resistance. In order to maintain the pock mark resistance satisfactorily, the C content is preferably as low as possible. However, since it is difficult to set the content to 0% by mass, 0.01% by mass may be set as the lower limit. Moreover, C content here is the value obtained by analyzing by the method prescribed | regulated to JISZ2615: 2009.

[Other ingredients]
Components other than the above in the flux of the present embodiment are inevitable impurities such as Zr, Ba, P, and S. Among these inevitable impurities, Zr and Ba are preferably regulated to 1.0% by mass or less, respectively, and in particular, P and S affecting the welding quality are preferably regulated to 0.05% by mass or less. Moreover, it is preferable that Zr, Ba, P, and S are 0.1 mass% or less in total.

[Production method]
When manufacturing the flux of this embodiment, for example, the raw material powder is blended so as to have the composition described above, kneaded with a binder, granulated, and fired. In that case, as a binder (binder), polyvinyl alcohol and water glass can be used, for example. The granulation method is not particularly limited, but a method using a rolling granulator or an extrusion granulator is preferable.

  Furthermore, it is preferable that the granulated flux is subjected to a sizing treatment such as dust removal and coarse particle crushing, so that the particle diameter is 2.5 mm or less. On the other hand, firing after granulation can be performed in a rotary kiln, a stationary batch furnace, a belt-type firing furnace, or the like. The firing temperature at that time can be set to, for example, 600 to 1200 ° C., but is preferably set to 800 ° C. or higher from the viewpoint of making the binder difficult to absorb moisture as described above. More preferably, it is 830 degreeC or more. Moreover, Preferably it is 850 degrees C or less. In addition, what was baked at 600-1200 degreeC is a high temperature baking type | mold flux.

As described above in detail, the flux of the present embodiment makes the content of each component in a specific range, and the ratio between the MgO content and the total content of Al ₂ O ₃ , F and TiO ₂ is specified. The amount of these components is adjusted so as to be in the range. Therefore, regardless of whether the welding power source is an AC type or a DC type, welding workability is good, and it is possible to reduce the amount of flux absorbed and the amount of diffusible hydrogen in the weld metal.

  Moreover, although the component composition of the flux of this embodiment is suitable as a high temperature baking type flux, even if it is applied as a melt type flux, the same effect as the high temperature baking type flux can be obtained.

  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 groove shape shown in FIG. 1 is used, and the welding conditions (A or B) shown in Table 3 below are used in submerged arc welding. A welding test was conducted. And the performance was evaluated about the flux of the Example shown in following Table 4, and the flux of the comparative example shown in following Table 5. FIG. In this example, the raw materials were blended so as to have the compositions shown in Table 4 and Table 5 below, kneaded with a binder (water glass), granulated, and further used in the following Table 4 and Table using a rotary kiln. By baking at the temperature shown in FIG. 5 and sizing, a flux having a particle size of 2.5 mm or less was obtained. In Tables 4 and 5, those not satisfying the scope of the present invention are indicated by underlining the numerical values.

In addition, the remainder of the steel plate composition shown in the said Table 1 and the wire composition shown in the said Table 2 is Fe and an unavoidable impurity. In addition, “M” shown in Table 4 and Table 5 is a value of [MgO] / ([Al ₂ O ₃ ] + [CaF ₂ ] + [TiO ₂ ]).

  Evaluation of each flux in Examples and Comparative Examples is based on the amount of diffused hydrogen in the weld metal, the moisture absorption amount of the flux, the impact test, the bead appearance, the bead shape, the slag peelability, the arc stability, and the weld defect (internal / external). Went about.

<Diffusion hydrogen amount>
In principle, the amount of diffused hydrogen in the weld metal was measured based on the method defined in JIS Z 3118: 2007. However, welding conditions A in Table 3 were adopted. In this example, the case where the diffusion hydrogen amount was 3.5 ml / 100 g or less was regarded as acceptable.

<Moisture absorption>
The amount of moisture absorption was evaluated based on the amount of moisture absorption after 2 hours of forced moisture absorption. Specifically, after re-drying a flux having a particle diameter of 500 to 850 μm at 250 ° C. × 1 hr, the flux is absorbed when forced absorption is performed for 2 hours at 30 ° C. and a relative humidity of 80%. The water content was measured using the KF (Karl Fischer) method. Hygroscopic resistance was good when the KF moisture content after moisture absorption for 2 hours was 500 ppm or less.

<Impact test>
The impact test was implemented based on the method prescribed | regulated to JISZ2242: 2005, and evaluated by the value of the Charpy absorbed energy in -40 degreeC. And in the present Example, what passed Charpy absorbed energy was 100J or more was set as the pass.

<Bead appearance>
The appearance of the bead is mainly an evaluation of the wave and gloss of the bead, and was performed by visually observing the weld. As a result, the bead wave is not disturbed and the bead has a metallic luster ◎, the bead wave perturbation per unit weld length (1m) is one place, and the bead has a metallic luster ○, unit welding The bead wave irregularity is 2 to 4 places per long (1m) and the bead has no metallic luster. The unit weld length (1m) has 5 or more bead wave irregularities and the bead has metallic luster. Those that do not have a cross. And in the present Example, what was evaluated as (double-circle) or (circle) was set as the pass.

<Bead shape>
The bead shape is mainly an evaluation related to the unevenness of the bead and the familiarity with the base material, and was performed by visually observing the welded portion. As a result, ◎ indicates that the bead shape was very good, ◯ indicates that the bead shape was good, Δ indicates that the bead shape was slightly poor, and × indicates that the bead shape was poor. And in the present Example, what was evaluated as (double-circle) or (circle) was set as the pass.

<Slag peelability>
Slag peelability was evaluated by the ease of slag removal and the presence or absence of seizure. Specifically, slag is naturally peeled off and there was no seizure, ◎, but naturally peeled off, but when seizure occurred at 3 or less points per unit weld length (1 m), ○, without natural peeling, unit The case where seizure occurred at 4 to 9 locations per weld length (1 m) was Δ, and the case where seizure occurred at 10 locations or more per unit weld length (1 m) without being spontaneously peeled. And in the present Example, what was evaluated as (double-circle) or (circle) was set as the pass.

<Arc stability>
Arc stability was evaluated by current and voltage fluctuations during welding. Specifically, the welding current is ± 50 A and the arc voltage is ± 2 V, the welding current is ± 100 A and the arc voltage is ± 2 V, the welding current is ± 100 A, and the arc voltage is What was +/- 4V was set as (triangle | delta), and what was difficult to weld was set as x. And in the present Example, what was evaluated as (double-circle) or (circle) was set as the pass.

<Welding defect>
Weld defects (internal) are mainly evaluations related to weld defects that occur inside the weld metal, such as pore defects, slag entrainment, and poor fusion, and ◎, unit weld length (1 m) where these weld defects did not occur ) When the generation ratio per unit weld length (1 m) was 0.5% or less, and when the generation ratio per unit weld length (1 m) was over 0.5% and 1.0% or less, Δ, unit weld length The case where the generation ratio per (1 m) exceeded 1.0% was evaluated as x. And in the present Example, what was evaluated as (double-circle) or (circle) was set as the pass.
In addition, the X-ray transmission photograph image | photographed based on JISZ3104: 1995 was used for the detection of a welding defect (internal). The generation ratio per unit weld length (1 m) in the evaluation of weld defects (internal) is the measurement of the size (length) of individual defects (defects) in accordance with JIS Z 3104: 1995. ) Is calculated and then divided by the effective length of the test part and converted per unit weld length.

On the other hand, the weld defect (external) is an evaluation mainly related to weld defects generated on the surface of the weld metal such as undercuts and pock marks, and ◎, unit weld length (1 m) where these weld defects did not occur. ) When the generation ratio per unit weld length (1 m) was 0.5% or less, and when the generation ratio per unit weld length (1 m) was over 0.5% and 1.0% or less, Δ, unit weld length The case where the generation ratio per (1 m) exceeded 1.0% was evaluated as x. And in the present Example, what was evaluated as (double-circle) or (circle) was set as the pass.
In addition, the detection of the welding defect (external) was performed visually. The rate of occurrence per unit weld length (1m) in the evaluation of weld defects (external) is to measure the length of each undercut, pock mark, etc., and calculate the total length of weld defects (external). Then, it is divided by the effective length of the same test part as the weld defect (internal) and converted per unit weld length.

  The above evaluation results are summarized in Table 6 and Table 7 below. In Tables 6 and 7, the values of the diffusion hydrogen amount in the weld metal, the moisture absorption amount of the flux, and the Charpy absorbed energy values in the impact test do not satisfy the evaluation criteria, and the numerical values are underlined.

  Example No. shown in Table 6 Since the fluxes 1 to 35 satisfy the scope of the present invention, the bead appearance, the bead shape, the slag peelability and the arc stability are excellent, and no occurrence of weld defects (internal / external) is observed. It was. Further, the moisture absorption amount of the flux and the amount of diffusible hydrogen in the weld metal were low. Moreover, the value of Charpy absorbed energy was low.

Comparative Example No. The flux of No. 1 had an inferior bead shape because the Al ₂ O ₃ content exceeded 25% by mass. Comparative Example No. Since the flux of No. ₂ had an Al ₂ O ₃ content of less than 10% by mass, the bead shape was inferior. Comparative Example No. The flux of No. 3 was inferior in slag removability because the SiO ₂ content exceeded 20% by mass. Comparative Example No. Since the flux of No. 4 had a SiO ₂ content of less than 10% by mass, the bead appearance and bead shape were inferior.

  Comparative Example No. The flux of No. 5 had an MgO content exceeding 35% by mass, so that the bead shape was inferior, and further, weld defects occurred in and on the surface of the weld metal. Comparative Example No. Since the flux of No. 6 had an MgO content of less than 25% by mass, seizure occurred and the slag peelability was inferior. Comparative Example No. The flux of No. 7 had an inferior bead shape because the F content exceeded 35% by mass. Since the flux of Comparative Example 8 had an F content of less than 15% by mass, welding defects such as undercuts and pock marks occurred.

Comparative Example No. The flux of No. 9 had a Mn content (MnO equivalent value) of 2.0% by mass or more, so the Charpy absorbed energy value was low and the toughness was inferior. Comparative Example No. The flux of No. 10 has a Na content (Na ₂ O conversion value), a K content (K ₂ O conversion value), and a Li (Li ₂ O conversion value) total amount of less than 0.5% by mass. Arc stability was significantly reduced, and the bead appearance and bead shape were also deteriorated. As a result, welding was difficult. Comparative Example No. In the flux No. 11, the total amount of Na content (Na ₂ O conversion value), K content (K ₂ O conversion value) and Li (Li ₂ O conversion value) exceeds 6.5 mass%. The arc stability was significantly deteriorated, and the bead appearance and bead shape were inferior. Moreover, the moisture absorption amount of the flux increased.

Comparative Example No. In the flux No. 12, the Fe content (FeO equivalent value) was less than 0.5% by mass, so that welding defects such as undercuts and pock marks occurred on the surface of the weld metal. Comparative Example No. The flux No. 13 had an Fe content (FeO equivalent value) exceeding 5% by mass, so the bead appearance and bead shape were inferior, and the slag peelability was also inferior. Comparative Example No. No. 14 flux was inferior in bead shape and slag peelability because the TiO ₂ content was less than 1% by mass. Moreover, the value of Charpy absorbed energy was low and the toughness was inferior. Comparative Example No. 15 flux is because it contains TiO ₂ exceeds 5 mass%, had poor bead shape.

Comparative Example No. Since the flux of No. 16 has a water-soluble SiO ₂ content exceeding 1.0 mass%, the amount of diffusion hydrogen in the weld metal and the moisture absorption amount of the flux increased. Comparative Example No. Since the flux of No. 17 had a water-soluble SiO ₂ content and a water-soluble Na ₂ O content exceeding 1.0 mass%, the amount of diffusion hydrogen in the weld metal and the moisture absorption amount of the flux increased. Comparative Example No. 18 flux has a water-soluble SiO ₂ content exceeding 1.0 mass%, and since the water-soluble K ₂ O content exceeds 0.8 mass%, diffusion hydrogen in the weld metal The amount and the moisture absorption amount of the flux increased.

  Comparative Example No. Since the flux of No. 19 had M of less than 0.50, the slag peelability was inferior. Comparative Example No. In the flux No. 20, since M exceeds 1.10, the diffusion hydrogen amount in the weld metal and the moisture absorption amount of the flux increased. Comparative Example No. In the flux No. 21, since the CaO content exceeds 6% by mass, the appearance and shape of the beads were inferior. Comparative Example No. Since the C content of the flux No. 22 exceeded 0.2 mass%, a pock mark was generated on the surface of the weld metal, and the bead appearance and bead shape deteriorated.

  From the above results, by using the flux of the present invention, the welding workability is improved, and the moisture absorption amount of the flux and the amount of diffusible hydrogen in the weld metal are reduced regardless of whether the welding is an AC type or a DC type. It was confirmed that it was possible to do.

Claims (4)

MgO: 25 to 35% by mass,
F converted to CaF ₂ : 15 to 35% by mass,
Al ₂ O ₃ : 10 to 25% by mass,
SiO ₂ : 10 to 20% by mass,
A total of at least one of Na converted to Na ₂ O, K converted to K ₂ O and Li converted to Li ₂ O: 0.5 to 6.5% by mass,
FeO converted value of Fe: 0.5 to 5% by mass,
TiO ₂ : 1 to 5% by mass,
CaO: 6 mass% or less,
Mn converted to MnO: less than 2.0% by mass,
Water-soluble SiO ₂ : 1.0% by mass or less
Water-soluble Na ₂ O: 1.0% by mass or less,
Water-soluble K ₂ O: 0.8% by mass or less,
The MgO content is [MgO], the Al ₂ O ₃ content is [Al ₂ O ₃ ], the F content in terms of CaF ₂ is [CaF ₂ ], and the TiO ₂ content is [TiO _2]. ], A flux for submerged arc welding characterized by satisfying the following formula (I).

The flux for submerged arc welding according to claim 1, further comprising water-soluble Li ₂ O: 0.3% by mass or less.   C content is 0.2 mass% or less, The flux for submerged arc welding of Claim 1 or 2 characterized by the above-mentioned.   The flux for submerged arc welding according to any one of claims 1 to 3, wherein the flux is fired at 800 ° C or higher.

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