TWI760843B - Submerged arc welding flux, submerged arc welding method, and manufacturing method of submerged arc welding flux - Google Patents

Abstract

An object of the present invention is to provide a flux for submerged arc welding which is not affected by construction conditions, suppresses the generation of iron particles, pitting, etc., and has excellent slag peeling properties. A flux, which is used for submerged arc welding, is characterized in that it contains fluoride and oxide, and the oxide is composed of a high melting point oxide with a melting point of over 1800°C and a low melting point with a melting point of less than 1800°C Oxide composition, including oxides containing Ca as the high melting point oxide and oxides containing Mn as the low melting point oxide, the content of the total flux of the flux is MnO conversion value of 2~ 8 mass %, and the aforementioned MnO-converted value, F's CaF ₂ -converted value, Ca's CaO-converted value, and CO ₂ satisfy the relationship of 1.6≦{CaF ₂ -converted value/(MnO-converted value+CaO-converted value+CO ₂ )}, The ratio of the total content of the refractory oxides to the total content of the oxides is (the sum of the refractory oxides/the sum of the oxides) 0.56 or more of the flux for submerged arc welding.

Description

Flux for submerged arc welding, method for submerged arc welding, and method for producing flux for submerged arc welding

The present invention relates to a flux for submerged arc welding, and more specifically, to a flux for submerged arc welding having excellent slag peeling properties in welding workability. Moreover, about the submerged arc welding method using the said flux, and the manufacturing method of the said flux.

Submerged arc welding is performed by spreading a granular flux along the welding part in advance, supplying the welding wire continuously into the flux and covering it with the flux, and generating an arc between the material to be welded and the welding wire. welding method.

Various reviews have been carried out for the purpose of improving the welding workability of submerged arc welding. For example, in Patent Documents 1 and 2, it is disclosed that the content of the components constituting the flux is defined, and the ratio of the MgO content to the total content of Al ₂ O ₃ , CaF ₂ conversion value and TiO ₂ is set as A specific range, regardless of whether the welding current is AC or DC, can also improve the welding workability. In addition, Patent Documents 1 and 2 disclose that the amount of diffusible hydrogen in the weld metal can be reduced, and Patent Document 2 discloses that the moisture absorption amount of the flux can be reduced. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-112633 [Patent Document 2] Japanese Patent Laid-Open No. 2016-140889

[Problems to be Solved by Invention]

However, in welding such as slot welding, where construction is particularly difficult, the bead tends to be convex, and it is particularly difficult to ensure the slag peelability at the toe portion.

On the other hand, the inventors of the present invention paid attention to the Mn element, and found that the more Mn is added, the more the slag peelability is improved. In addition, the addition of Mn induces the generation of iron particle protrusions (hereinafter simply referred to as "iron particles"), pitting, and the like, resulting in residual problems in the appearance of beads or surface defects, which are one of welding workability.

The present invention has been developed in view of the above-mentioned situation, and its object is to provide submerged arc welding that can suppress the generation of surface defects such as iron particles and pits, and has excellent slag peelability regardless of construction conditions. Use flux. [Technical means to solve problems]

The flux of one aspect of the present invention is used for submerged arc welding, and includes a fluoride and an oxide, and the oxide is composed of a high melting point oxide having a melting point of 1800°C or higher and a low melting point oxide having a melting point of less than 1800°C , including the oxide containing Ca as the high melting point oxide and the oxide containing Mn as the low melting point oxide, the MnO conversion value of the content of Mn to the total mass of the flux is 2 to 8 mass %, In addition, the above-mentioned MnO-converted value, the CaF ₂ -converted value of F, the CaO-converted value of Ca, and CO ₂ satisfy the relationship of 1.6≦{CaF ₂ -converted value/(MnO-converted value+CaO-converted value+CO ₂ )}, the above-mentioned high melting point oxidation A flux for submerged arc welding in which the ratio of the total content of the oxides to the total content of the oxides (the total content of the refractory oxides/the total content of the oxides) is 0.56 or more.

In the above-mentioned flux for submerged arc welding, wherein the high melting point oxide contains at least one of MgO and TiO ₂ , the content of the flux is 25 mass % or less in terms of MgO equivalent of Mg, and the content of Ti is 25% by mass or less. The TiO ₂ conversion value is 9 mass % or less, the ratio of the content of the sum of the MgO conversion value and the TiO ₂ conversion value to the total content of the high melting point oxide {(MgO conversion value + TiO ₂ conversion value)/ The total content of the refractory oxides} is 0.430 or more. In the above-mentioned flux for submerged arc welding, the content of the high melting point oxide to the total mass of the flux is 10 mass % or less in terms of CaO, 25 mass % or less in terms of Al ₂ O ₃ , and The MgO conversion value, the TiO ₂ conversion value, the CaO conversion value, and the Al ₂ O ₃ conversion value satisfy 30≦(MgO conversion value+0.67TiO ₂ conversion value+0.92CaO conversion value+0.74Al ₂ O ₃ conversion value )≦50.

In the above-mentioned flux for submerged arc welding, the content of the low melting point oxide to the total mass of the flux is 20 mass % or less in terms of Si in terms of SiO ₂ , 5 mass % or less in terms of Fe in terms of Fe, and 5 mass % or less in B The B ₂ O ₃ conversion value is 1 mass % or less, and the alkali metal oxide conversion value of the alkali metal element is 5.0 mass % or less. In the flux for submerged arc welding, the alkali metal oxide conversion value is a value converted to at least one oxide selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O.

In the above-mentioned flux for submerged arc welding, the content of the total mass of the flux is 20% by mass or more in terms of CaF ₂ and 6.0% by mass or less of CO ₂ .

The welding method of one aspect of the present invention is a submerged arc welding method for arc welding using a flux, the flux includes a fluoride and an oxide, and the oxide is composed of a high melting point oxide with a melting point of 1800°C or more and a melting point The composition of low melting point oxides below 1800°C includes oxides containing Ca as the high melting point oxides, and oxides containing Mn as the low melting point oxides, and the content of the total mass of the flux is Mn. The MnO conversion value is 2 to 8 mass %, and the aforementioned MnO conversion value, the CaF ₂ conversion value of F, the CaO conversion value of Ca, and the CO ₂ satisfy 1.6≦{CaF ₂ conversion value/(MnO conversion value+CaO conversion value+CO ₂ )}, the ratio of the total content of the refractory oxides to the total content of the oxides (the total content of the refractory oxides/the total content of the oxides) is 0.56 or more. In the above-mentioned submerged arc welding method, wherein, the material to be welded is processed with grooves as U grooves or V grooves, and the groove angle is 10~60°.

A method for producing a flux of one aspect of the present invention is a method for producing a flux for submerged arc welding, and includes a process of firing granules derived from raw materials at 400 to 950° C., and the firing process is described above. The latter flux contains fluorides and oxides, and the oxides are composed of high melting point oxides with a melting point of 1800°C or higher and low melting point oxides with a melting point of less than 1800°C, including Ca as the high melting point oxides. and the oxides containing Mn which are the aforementioned low melting point oxides, the content of the flux based on the total mass of the flux is 2 to 8 mass % in terms of MnO equivalents, and the aforementioned MnO equivalent values and F in terms of CaF ₂ The value of CaO, the CaO-converted value of Ca, and CO ₂ satisfy the relationship of 1.6≦{CaF ₂ -converted value/(MnO-converted value+CaO-converted value+CO ₂ )}, and the content of the sum of the above-mentioned refractory oxides in the sum of the above-mentioned oxides A method for producing a flux for submerged arc welding in which the ratio of the total content (the total content of the refractory oxides/the total content of the oxides) is 0.56 or more. [Inventive effect]

According to the present invention, it is possible to provide a flux for submerged arc welding having excellent slag peelability while suppressing the generation of iron particles, pitting, and the like. By using this flux for submerged arc welding, excellent slag peelability and good bead appearance with few surface defects can be achieved simultaneously without being affected by construction conditions.

Hereinafter, an embodiment (the present embodiment) for carrying out the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can change arbitrarily in the range which does not deviate from the technical thought of this invention, and can implement.

<Flux> The flux for submerged arc welding of this embodiment (hereinafter referred to as "flux") contains fluorides and oxides, and the oxides are composed of high melting point oxides with a melting point of 1800°C or higher and a melting point of less than 1800°C. The low-melting-point oxide composition of °C includes a Ca-containing oxide as the high-melting-point oxide, and an Mn-containing oxide as the low-melting-point oxide. The content of Mn in the total mass of the flux is 2 to 8 mass % in terms of MnO conversion, and the aforementioned MnO conversion value, F in CaF ₂ conversion value, Ca in CaO conversion value, and CO ₂ satisfy 1.6≦{CaF ₂ conversion value /(MnO-converted value+CaO-converted value+CO ₂ )} relationship. Moreover, the ratio of the total content of the refractory oxides to the total content of the oxides (the total content of the refractory oxides/the total content of the oxides) is 0.56 or more.

As a high melting point _oxide , MgO, _TiO2 , CaO, _Al2O3 , _ZrO2 , BaO etc. are mentioned, for example. In addition to the above, the flux may contain low melting point oxides with a melting point of less than 1800°C, for example, MnO, MnO ₂ , Mn ₂ O ₃ , SiO ₂ , B ₂ O ₃ , FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , alkali metal oxides, and the like.

Hereinafter, the content of each component of the flux of the present embodiment will be described. In addition, the content of the present embodiment refers to the mass % of the total mass of the flux, unless otherwise specified. In addition, a part of each component which comprises a flux is the content of the conversion value converted into oxide or fluoride based on the amount of each element obtained by analysis according to JIS Z 3352:2017 or the like. Therefore, the total content of each component to the total mass of the flux may exceed 100% by mass.

[MnO-converted value of Mn: 2 to 8 mass %] The MnO-converted value is a value obtained by converting the total Mn amount of the flux into MnO. The measured total Mn amount may contain components other than MnO such as MnO ₂ and Mn ₂ O ₃ , but these components have almost the same effect, so the MnO-converted value of total Mn is within the aforementioned range. That's it. MnO affects the viscosity and solidification temperature of the slag, and is an essential component effective in improving the slag peelability. Among the forms of oxides such as MnO, MnO ₂ , and Mn ₂ O ₃ , it is particularly useful when added in the form of MnO or MnO ₂ . In this way, as the content of MnO increases, the slag peelability improves. In addition, it was found that iron particles, pitting, and the like are more likely to be generated as the content of MnO is increased.

The structural considerations for the generation of iron particles are as follows. First, the iron powder in the flux aggregates in the molten slag to form large metal particles and sink. At this time, if the surface of the bead is in a molten state, the metal particles directly become the fusion metal, but if the surface of the bead is in a solidified state, the metal particles adhere to the surface of the bead and become iron particles. That is, when the metal particles sink in the molten slag, if the surface of the bead is in a molten state, the generation of iron particles can be suppressed. In order to bring the surface of the bead into a molten state, it is possible to raise the solidification temperature of the slag. On the other hand, the melting point of MnO is about 1785°C, and it is not a high melting point oxide. Therefore, if the content of MnO is increased too much, iron particles are likely to be generated.

In addition, if the solidification temperature of the molten slag is made too high, the generated air bubbles are not easily released, and it is also presumed that pitting is likely to be generated. In addition, when there is a large amount of water in the slag, pitting is likely to occur. In addition, hygroscopicity is also presumed to be a cause of the generation of pitting, and since MnO has high hygroscopicity, when the content of MnO is too large, pitting is likely to be generated.

For the above reasons, the content of Mn in terms of MnO in the present embodiment is 2 mass % or more, preferably 2.5 mass % or more, and more preferably 3 mass % or more. Moreover, the MnO conversion value is 8 mass % or less, Preferably it is 7.5 mass % or less, More preferably, it is 7 mass % or less.

[CaF ₂ -converted value of F] The CaF ₂ -converted value is a value obtained by converting the total F amount of the flux into CaF ₂ . The measured total F content may contain fluorides other than CaF ₂ such as AlF ₃ and MgF ₂ . However, regardless of the form, as fluorides, it has almost the same effect as CaF ₂ . The CaF ₂ conversion value of F may be within the aforementioned range. Fluoride is a component that improves the suppression of pitting, the electrical conductivity and fluidity of slag, and the like. In addition, regarding the effect|action of fluidity, it is one of the components which influences the high temperature viscosity of a molten slag in proportion to the amount of the presence of CaO, which will be described later.

The content of the CaF ₂ conversion value of F in the present embodiment is preferably 20 mass % or more, more preferably 25 mass %, from the viewpoint of suppressing the generation of pitting by promoting gas discharge from molten slag More than 27 mass % or more is most desirable. In addition, if it is too large, the fluidity of the slag becomes too high, and the shape of the bead is deteriorated. Therefore, the CaF ₂ conversion value is desirably 35 mass % or less, and more desirably 33 mass % or less.

[MgO conversion value of Mg] The MgO conversion value is a value obtained by converting the total Mg amount of the flux into MgO. MgO is a high melting point oxide with a melting point of 2800°C, which greatly contributes to the improvement of slag peelability. In order to obtain this effect, the content of Mg in terms of MgO conversion value is desirably 15 mass % or more, more desirably 16 mass % or more, and most desirably 17 mass % or more. In addition, if the amount is too large, the shape of the bead is deteriorated, slag entrainment, poor fusion, etc. are likely to occur, and results such as overcutting are likely to occur. Moreover, there exists a possibility that the solidification temperature of a molten slag will become too high, and it may become easy to generate|occur|produce pitting. Therefore, the MgO conversion value is desirably 25 mass % or less, more desirably 24 mass % or less, and most desirably 23 mass % or less.

[Ti TiO ₂ conversion value] The TiO ₂ conversion value is a value obtained by converting the total Ti amount of the flux into TiO ₂ . TiO ₂ is a high melting point oxide with a melting point of 1870°C. It is an effective component for improving the slag peeling property, and also has the effect of adjusting the appearance of the bead to be good by adding an appropriate amount. In addition, a part of _TiO2 is formed into Ti by the reduction reaction at the time of welding, and is also added to the welding metal, which contributes to the improvement of toughness. In order to obtain this effect, the content of Ti in terms of TiO ₂ is desirably higher than 0 mass %, more desirably 0.1 mass % or more, and most desirably 0.2 mass % or more. In addition, if the amount is too large, the shape of the bead will be deteriorated, or the solidification temperature of the slag will become too high, and pitting may be easily generated. Therefore, the TiO ₂ conversion value is desirably 9 mass % or less, more desirably 4 mass % or less, and most desirably 3.5 mass % or less.

[CaO-converted value of Ca] The CaO-converted value is a value obtained by converting the total Ca content of the flux by subtracting the Ca content contained in the CaF ₂ -converted value from the total F content to CaO. CaO is a high melting point oxide with a melting point of 2572°C, which improves the basicity of the slag and the cleanliness of the welded metal, and also affects the fluidity of the slag. This action is proportional to the amount present, and the lower limit of the content of Ca in terms of CaO is not particularly limited, but is preferably, for example, 0.5 mass % or more. In addition, when there is too much CaO, the fluidity of the molten slag becomes too large, and the appearance of the bead and the shape of the bead may deteriorate. Moreover, since CaO has high hygroscopicity similarly to MnO, if the content of CaO is too high, there is a possibility that pitting may be easily generated. Therefore, the CaO conversion value is desirably 10 mass % or less, more desirably 9.5 mass % or less, and most desirably 9 mass % or less.

[Al ₂ O ₃ Conversion Value of Al] The Al ₂ O ₃ conversion value is a value obtained by converting the total Al amount of the flux into Al ₂ O ₃ . Al ₂ O ₃ is a high melting point oxide with a melting point of 2072°C. It adjusts the viscosity and melting point of the slag, and has the effect of increasing the solidification temperature of the slag and improving the shape of the bead during welding. In order to obtain this effect, the content of Al in terms of Al ₂ O ₃ is preferably 10% by mass or more, more preferably 12% by mass or more, and most preferably 15% by mass or more. Moreover, when it is too large, the melting point of the slag may rise excessively, which may cause deterioration of the shape of the bead during welding. Therefore, the value in terms of Al ₂ O ₃ is desirably 25 mass % or less, and more desirably 20 mass % or less.

[ZrO ₂ conversion value of Zr] The ZrO ₂ conversion value is a value obtained by converting the total Zr amount of the flux into ZrO ₂ . ZrO ₂ is a high melting point oxide with a melting point of 2715°C. It adjusts the viscosity and melting point of the slag and has the effect of increasing the solidification temperature of the slag and improving the shape of the bead during welding. This action is an arbitrary component proportional to the amount present, and the lower limit of the content of Zr in terms of ZrO ₂ is not particularly limited, but is preferably 0.5% by mass or more if an effective action is to be imparted. In addition, when there is too much ZrO ₂ , the melting point of the molten slag becomes too large, and the appearance of the bead and the shape of the bead may deteriorate. Therefore, the ZrO ₂ conversion value is desirably 5 mass % or less, and more desirably 3 mass % or less.

[BaO conversion value of Ba] The BaO conversion value is a value obtained by converting the total Ba amount of the flux into BaO. BaO is a high melting point oxide with a melting point of 1923°C, which improves the basicity of the slag and the cleanliness of the welded metal, and also affects the fluidity of the slag. This action is an arbitrary component proportional to the amount present, and the lower limit of the content of Ba in terms of BaO is not particularly limited, but is preferably 0.5% by mass or more if an effective action is to be imparted. In addition, when there is too much BaO, the fluidity of the molten slag becomes too large, and there is a possibility that the appearance of the bead and the shape of the bead are deteriorated. Therefore, the BaO conversion value is desirably 5 mass % or less, and more desirably 3 mass % or less.

[High melting point oxide] The flux of the present embodiment contains a high melting point oxide having a melting point of 1800° C. or higher. Among the refractory oxides, the slag peelability becomes better as the ratio of MgO and TiO ₂ increases in particular. Therefore, the content of the sum of the MgO conversion value and the TiO ₂ conversion value to the total content of the refractory oxides is expressed by {(MgO conversion value + TiO ₂ conversion value)/the total content of the refractory oxide} The ratio expressed is preferably 0.430 or more, and more preferably 0.450 or more. In addition, if the ratio is too high, it contributes to an excessive freezing point. Therefore, the ratio is preferably 0.600 or less, and more preferably 0.545 or less.

It means the total content of MgO conversion value, TiO ₂ conversion value, CaO conversion value, and Al ₂ O ₃ conversion value of the total content of high melting point oxides. In addition, when the flux contains ZrO ₂ or BaO, the content of the ZrO ₂ conversion value of Zr and the BaO conversion value of Ba is also included in the total content of the refractory oxides. In addition, when the total content is too large, the solidification temperature of the slag becomes too high, and there is a possibility that pitting is likely to occur. Therefore, these contents, the values represented by the calculation formula of (MgO conversion value + 0.67TiO ₂ conversion value + 0.92 CaO conversion value + 0.74 Al ₂ O ₃ conversion value) are preferably 30 or more, and more preferably 32 or more. good. Moreover, this value is preferably 50 or less, and more preferably 45 or less. In the above-mentioned calculation formula, each coefficient multiplied by the content of each refractory oxide is a coefficient weighted by the ratio of the melting point based on the melting point of MgO at 2800°C. For example, a coefficient of 0.67 multiplied by the TiO ₂ conversion value is a value calculated by dividing the melting point of TiO ₂ at 1870°C by the melting point of MgO at 2800°C.

The ratio of the total content of refractory oxides with a melting point of 1800°C or higher to the total content of all oxides, expressed by (the total content of high melting point oxides/the total content of oxides), Department of 0.56 or more. By making this ratio 0.56 or more, the slag solidification temperature can be increased, and the generation of iron particles can be suppressed. In addition, the upper limit is not particularly limited, but by making the ratio 0.80 or less, the slag solidification temperature can be prevented from increasing to a temperature higher than necessary, and generation of pitting can be desirably suppressed. It is preferable that the value represented by (the total content of the refractory oxides/the total content of the oxides) is 0.57 or more. In addition, it is preferable that this value is 0.75 or less.

In addition, the total content of oxides refers to the oxide conversion value of the element forming a high melting point oxide with a melting point of 1800°C or higher and the oxide conversion value of the element forming a low melting point oxide with a melting point of less than 1800°C. sum. Examples of low melting point oxides having a melting point of less than 1800°C include MnO, MnO ₂ , Mn ₂ O ₃ , SiO ₂ , FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , B ₂ O ₃ , and alkali metal oxides. Wait.

[SiO ₂ conversion value of Si] The SiO ₂ conversion value is a value obtained by converting the total Si amount of the flux into SiO ₂ . SiO ₂ is a component that mainly adjusts the appearance of the bead and the shape of the bead to a good component by imparting appropriate viscosity to the molten slag. In order to obtain this effect, the content of Si in terms of SiO ₂ is preferably 8% by mass or more, and more preferably 11% by mass or more. On the other hand, if the amount is too large, the viscosity of the slag becomes excessive, the slag peelability is deteriorated, and the sintering of the slag may become excessively intense. Therefore, the SiO ₂ conversion value is desirably 20 mass % or less, more desirably 19 mass % or less, and most desirably 17 mass % or less. In addition, SiO ₂ includes SiO ₂ derived from alloys and SiO ₂ derived from minerals and water glass. However, Fe-Si and other alloy-derived SiO ₂ conversion values are ideal from the viewpoint of ensuring good mechanical properties. It is 4 mass % or less, and 16 mass % or less is preferable from the viewpoint of slag peelability of the sum total of the SiO ₂ conversion value derived from minerals and water glass.

[FeO-converted value of Fe] The FeO-converted value is a value obtained by converting the total Fe amount of the flux into FeO. The measured total Fe amount may contain components other than Fe added as metal powders such as FeO, Fe ₂ O ₃ , and Fe ₃ O ₄ . However, the FeO conversion value of all Fe is within the aforementioned range, that is Can. Fe—Si is mentioned as an example of Fe added to the metal powder, and it mainly has the effect of promoting the deoxidation phenomenon of the fusion metal. FeO has the effect of improving pitting resistance. This effect is proportional to the amount of Fe, and the lower limit of Fe in terms of FeO is not particularly limited, but is preferably 0.5% by mass or more, for example. In addition, if it is too large, the solidification temperature of the slag is affected, and the appearance of the bead, the shape of the bead, and the slag peelability may be deteriorated. Therefore, the FeO conversion value is desirably 5 mass % or less, and more desirably 4 mass % or less.

[B ₂ O ₃ conversion value of B] The B ₂ O ₃ conversion value is a value obtained by converting the total B amount of the flux into B ₂ O ₃ . B ₂ O ₃ has the effect of improving the toughness of the welded metal. When B is contained, it is preferable that the content of B in terms of B ₂ O ₃ is 0.1 mass % or more. On the other hand, if the content is too large, the molten metal will be hardened and the toughness will be lowered on the contrary. Therefore, the B ₂ O ₃ conversion value is preferably 1 mass % or less, and more preferably 0.5 mass % or less.

[Alkali metal oxide conversion value of alkali metal element] The alkali metal element is a component that mainly affects the arc stability during welding and the hygroscopic property of the flux, and this effect is proportional to the amount thereof. The lower limit of the total amount of the alkali metal oxide conversion value of the alkali metal element of an arbitrary element is not particularly limited, but it is preferably 1 mass % or more in order to impart an effective effect. In addition, if the sum of the alkali metal oxide conversion values is excessive, the hygroscopic properties of the flux will deteriorate, the arc will become too strong and unstable, and the appearance of the bead and the shape of the bead may be degraded. Therefore, the total amount of alkali metal oxide conversion values is desirably 5.0 mass % or less, and more desirably 4.5 mass % or less.

As the alkali metal element, it is preferable to contain at least one element selected from the group consisting of Na, K, and Li. When Na is included, the value in terms of Na ₂ O is used, and when K is included, K ₂ O is used. The conversion value, in the case of including Li, is limited to the content in terms of Li ₂ O conversion value, respectively. That is, the alkali metal oxide conversion value is preferably a value converted into at least one oxide selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O. Na ₂ O-equivalent value, K ₂ O-equivalent value, and Li ₂ O-converted value are all in Na ₂ O, K ₂ O, and Li ₂ O conversion, respectively, including the binder derived from the flux obtained in accordance with JIS M 8852:1998 The value of the total amount of Na, K or Li (binder). In the measured total Na, K, or Li amount, NaAlSi ₃ O ₈ , KAlSi ₃ O ₈ , or LiAlSi ₃ O ₈ may be contained, but the same effect is obtained. Therefore, the Na ₂ O conversion value and the K ₂ O conversion value The total amount of Li ₂ O conversion values may be within the aforementioned range.

Among the above-mentioned contents, it is more preferable to further contain at least one element of Na and K. In this case, the total amount of the Na ₂ O conversion value and the K ₂ O conversion value is preferably 1 mass % or more, preferably 5.0 mass % or less, and more preferably 4.5 mass % or less.

[CO ₂ ] CO ₂ is mainly derived from carbonate components such as CaCO ₃ , BaCO ₃ , and the like, and the carbonate is decomposed during welding to generate carbon dioxide (CO ₂ ) gas. CO ₂ gas is a component that can effectively prevent intrusion into the welded metal because it shields the outside gas to protect the welding part, and reduces the partial pressure of impurity gases such as H ₂ gas and N ₂ gas. Proportion. It is an arbitrary component, and the lower limit of the content of CO ₂ is not particularly limited, but it is preferably 0.5% by mass or more in order to provide an effective effect. Moreover, if it is too much, it will become a cause of generation|occurrence|production of a pitting, and there exists a possibility that a pitting resistance may deteriorate. Therefore, the CO ₂ content is desirably 6.0 mass % or less, more desirably 5.0 mass % or less, and most desirably 4.5 mass % or less.

[other ingredients] The components other than the above-mentioned components of the flux of the present embodiment are unavoidable impurities such as P and S. Since they affect the welding quality, it is preferable to limit P and S to 0.05 mass % or less, respectively. Moreover, other elements may be included in the range which does not impair the effect of this invention. As other elements, Ni, Cr, Mo, Nb, V, C, etc. are mentioned. The total of these other elements is preferably 5.0 mass % or less. That is, the total sum of the aforementioned components excluding inevitable impurities and other elements is generally 90% by mass or more, preferably 95% by mass or more.

[CaF ₂ conversion value/(MnO conversion value + CaO conversion value + CO ₂ )] In the flux of the present embodiment, the Mn system represented by the MnO conversion value is a component that improves the slag peelability, but it is Moisture induces pitting. Similarly, CaO and CO ₂ are components that tend to induce pitting. In addition, the fluoride specified in terms of CaF ₂ is a component that can suppress the generation of pitting. Therefore, by setting the ratio of the content represented by {CaF ₂ conversion value/(MnO conversion value+CaO conversion value+CO ₂ )} to 1.6 or more, it is possible to desirably suppress the occurrence of pitting. Moreover, it is preferable that this ratio is 1.8 or more. In addition, when the value is too high, the fluidity of the slag becomes too high and the bead shape may be deteriorated. Therefore, the value is preferably 9.0 or less, and more preferably 7.0 or less.

The flux of the present embodiment is preferably a high-temperature fired flux that is fired at 400 to 950° C. as a granulated material derived from a raw material.

＜Production method of flux＞ In the case of manufacturing the flux of the present embodiment, for example, in order to achieve the composition described in the aforementioned <flux>, the process of preparing the raw material powder and mixing it with the binder; the process of granulating; And the process of sintering the obtained granulated material from the raw material. As a binder (binder) in the mixing process, for example, polyvinyl alcohol, water glass, etc. can be used. The granulation method of the granulation process is not particularly limited, but a method using a rolling granulator, a push-type granulator, or the like is preferable.

The granulated flux is subjected to granulation treatment such as dust removal and coarse particle pulverization, and the particle diameter is preferably 2.5 mm or less. The firing after granulation can be performed by a rotary kiln, a stationary batch furnace, a belt firing furnace, or the like. The firing temperature at this time is desirably 400 to 950° C., and more desirably 450° C. or higher, from the viewpoint of the moisture absorption properties of the flux.

The flux of the present embodiment obtained as described above has excellent slag peelability while suppressing the generation of iron particles, pitting, etc., since the content of each component is set in a specific range.

Furthermore, the composition of the flux of the present embodiment is ideal as a high-temperature firing type flux, but it does not exclude that it is ideal as a molten type flux.

<Welding method using flux> The welding method of the present embodiment is a submerged arc welding method for arc welding using a flux having a composition within the range described in the aforementioned <Flux>. This welding method is very effective for slot welding, especially slot welding, which is one of the difficult welding methods. That is, the shape of the groove of the base material and the material to be welded, such as the workpiece, is not particularly limited, but it is more preferable to process a U-groove or a V-groove.

When the material to be welded is a U-shaped groove or a V-shaped groove processed by U-groove or V-groove, the groove angle is preferably 10° or more, more preferably 15° or more. In addition, the groove angle is preferably 90° or less, more preferably 60° or less, and most preferably 20° or less.

The groove depth is preferably 20 mm or less, and more preferably 15 mm or less, from the viewpoint of preventing melting and falling of the material to be welded. In the U-shaped groove, the path radius of the U-shaped groove is preferably R2 or more, and more preferably R5 or more, from the viewpoint of preventing welding defects. In addition, from the viewpoint of fusion efficiency, the path radius is desirably R10 or less, and more desirably R8 or less. The path radius is a welding term defined in JIS Z 3001-1:2018. [Example]

Hereinafter, the content of the present invention will be specifically described with reference to test examples. The raw materials are prepared so as to have the compositions described in Tables 1 and 2, and then they are mixed with water glass as a binder, and then granulated. The kiln was fired at 450 to 550°C (actual temperature) and the particle size was adjusted to prepare the fluxes of Test Examples 1 to 18. In addition, the fluxes of Test Examples 1 to 19 are examples, and the fluxes of Test Examples 20 to 29 are comparative examples. In addition, in Table 1, the [-] mark of CO ₂ means 0.5 mass % or less, and the [-] mark of the B ₂ O ₃ conversion value of B means 0.1 mass % or less.

In the table, the numerical value of each component refers to the content, and it is shown as the mass % of the total mass of the flux. [R] means an alkali metal element, but none of the alkali metal elements other than Li, Na, and K were included in any of the test examples. [RO conversion value] refers to the total content of the alkali metal oxide conversion values of the alkali metal elements. However, since none of the alkali metal elements other than Li, Na, and K were included in any of the test examples, it refers to the conversion to The sum of the values of at least one oxide selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O. "High melting point oxide" refers to the total content of elements that form high melting point oxides with a melting point of 1800°C or higher in terms of oxides. In this example, since ZrO ₂ and BaO are not contained, it is a value in terms of MgO , TiO2 conversion value, CaO conversion value and the total amount of Al ₂ O ₃ conversion value. [Low-melting-point oxide] refers to the total content of elements that form oxides with a melting point of less than 1800° C. in terms of oxides. However, even when Fe ₂ O ₃ , Fe ₃ O ₄ and the like are contained, the total Fe amount is converted into FeO, and even when MnO ₂ , Mn ₂ O ₃ and the like are contained, the total Mn amount is converted into MnO. Therefore, the "low melting point oxide" refers to the total amount of the MnO conversion value, the SiO ₂ conversion value, the FeO conversion value, the B ₂ O ₃ conversion value, and the alkali metal oxide conversion value. The sum of the [oxides] refers to the sum of the above-mentioned high melting point oxides and low melting point oxides, but, for example, in Test Example 11, the sum deviates from the sum of the contents of the high melting point oxides and the low melting point oxides, and is due to significant digits. Similarly, for example, in Test Example 1, the sum of the [Si SiO ₂ conversion value] is deviated from the sum of contents described in alloys and minerals, and this is also due to significant figures. The total content of all the components may exceed 100% by mass because the total amount of each element obtained by the analysis is converted into the oxide or fluoride conversion value as the content.

Using the obtained flux, submerged arc welding using a steel plate as a material to be welded was performed. The material to be welded, the wire used for welding, and the welding conditions are described below.

[material to be welded] Steel sheet: C is 0.16 mass %, Si is 0.30 mass %, Mn is 1.30 mass %, P is 0.007 mass %, S is 0.001 mass %, and the remainder is Fe and inevitable impurities Plate thickness: 25mm Slot depth: 15mm Path spacing: 0mm Slot shape: U-shaped slot Groove Angle: 16˚ Path Radius: R8 [wire] Type of wire: According to JIS Z 3351:2012 YS-S6 Wire diameter: 4.0mm [welding conditions] Welding current: 650A Welding voltage: 30V Welding speed: 65cm/min Lamination method: 1 layer 1 pass

For submerged arc welding using each flux, the slag peelability and the generation rate of iron particles and pitting were evaluated. Each evaluation method and evaluation criteria are as follows. As a total evaluation, among the evaluation results of slag peelability, iron particles, and pitting, if one of the items was unacceptable, it was judged as unacceptable and it was not suitable for use as a flux.

<Slag peelability> The slag peelability was evaluated as described below with respect to the ease of slag removal, where A and B were considered acceptable, and C was considered unacceptable. The results are shown in [Slag Peeling] in Table 2. A: Immediately after welding, the welding slag peeled off naturally. B: When the slag is hit with a jig such as a hammer, the welded slag is peeled off. C: Even if the slag is hit with a jig such as a hammer, the welding slag does not peel off, and the burn marks of the welding slag remain on the bead.

<Production rate of iron particles> It was visually confirmed that iron particles were generated on the surface of the bead. The generation rate was evaluated as described below, and A and B were considered acceptable, and C and D were considered unacceptable. The results are shown in Table 2 [Iron Particles]. A: No iron particles are generated on the surface of the bead. B: One or two iron particles were generated per welding length of 750 mm on the bead surface. C: The number of iron particles generated per welding length of 750 mm on the bead surface is 3 or more and 9 or less. D: The number of iron particles generated per welding length of 750 mm on the bead surface is 10 or more.

＜The rate of occurrence of pockmarks＞ It was visually confirmed that pitting was generated on the surface of the bead. Regarding the generation rate, evaluation was performed as described below, with A to C being acceptable and D being unacceptable. The results are shown in [Pockmark] in Table 2. A: There is no pitting on the surface of the bead. B: The number of pockmarks per welding length of 750 mm on the surface of the bead is one or two. C: The number of occurrences of pitting per welding length of 750 mm on the surface of the bead is 3 or more and 5 or less. D: The number of pockmarks generated per welding length of 750 mm on the surface of the bead is 6 or more.

As shown in Table 2, the fluxes of Test Examples 1 to 19, which are examples, have excellent slag releasability, and the generation rates of iron particles, pitting, and the like are low. In particular, with respect to Test Examples 1 to 6, 10 to 12, and 14 to 16, in the evaluation of slag peelability, iron particles, and pitting, the evaluation results of two or more items are A, which are very good for use in submerged arc welding. of flux.

From the above results, it was confirmed that by using the flux of the present invention for submerged arc welding, even in welding with difficult construction such as slot welding, excellent slag peelability and good beading with few surface defects can be obtained. Appearance exists at the same time.

Various embodiments of the present invention have been described above with reference to the drawings, but the present invention is not limited to these embodiments. A person with ordinary knowledge in the field can easily think of various modifications or amendments within the technical idea described in the scope of the patent application, and it goes without saying that such examples also belong to the technical scope of the present invention. Moreover, each component of the above-mentioned embodiment can be combined arbitrarily in the range which does not deviate from the technical idea of this invention.

Furthermore, the present application is based on Japanese Patent Application (Japanese Patent Application No. 2019-166576) filed on September 12, 2019 and Japanese Patent Application (Japanese Patent Application No. 2020-117993) filed on July 8, 2020, in This specification is incorporated by reference to that content.

Claims (7)

A flux for submerged arc welding, which is used for submerged arc welding, is characterized by comprising: fluoride and oxide, wherein the oxide is composed of a high melting point oxide with a melting point of 1800°C or higher and a melting point of less than 1800 It is composed of low melting point oxides of ℃, and contains: oxides containing Ca as the high melting point oxides and oxides containing Mn as the low melting point oxides, and the content of the total mass of the flux is Mn The MnO conversion value is 2~8 mass %, and the aforementioned MnO conversion value, the _CaF2 conversion value of F, the CaO2 conversion value of Ca, and the _CO2 satisfy 1.6≦{ _CaF2 conversion value/(MnO conversion value+CaO conversion value+ CO ₂ )}, the ratio of the total content of the refractory oxides to the total content of the oxides (the total content of the refractory oxides/the total content of the oxides) is 0.56 or more The high melting point oxide contains at least one of MgO and TiO ₂ , and the content of the total mass of the flux is 25 mass % or less in terms of MgO conversion value of Mg, and 9 mass % or less in terms of TiO ₂ conversion value of Ti, The ratio of the total content of the above-mentioned MgO-converted value and the above-mentioned _TiO2 -converted value to the total content of the above-mentioned refractory oxides {(MgO-converted value + _TiO2 -converted value/content of the sum of the refractory oxides} is: 0.477 or more, the content with respect to the total mass of the flux is 20 mass % or more in terms of the aforementioned CaF ₂ conversion value, and the aforementioned CO ₂ is 6.0 mass % or less. The flux for submerged arc welding according to claim 1, wherein the content of the high melting point oxide to the total mass of the flux is 10 mass % or less in terms of CaO, and 25 mass % in terms of Al ₂ O ₃ . below, and the above-mentioned MgO-converted value, the above-mentioned TiO ₂ -converted value, the above-mentioned CaO-converted value, and the above-mentioned Al ₂ O ₃ -converted value satisfy 30≦(MgO-converted value+0.67 TiO ₂ -converted value+0.92CaO-converted value+0.74Al ₂ O ₃ conversion value)≦50. The flux for submerged arc welding according to claim 1 or 2, wherein the content of the low melting point oxide to the total mass of the flux is 20 mass % or less in terms of Si in terms of SiO ₂ and 5 in FeO in terms of Fe The B ₂ O ₃ conversion value of B is 1 mass % or less, and the alkali metal oxide conversion value of the alkali metal element is 5.0 mass % or less. The flux for submerged arc welding according to claim 3, wherein the alkali metal oxide conversion value is converted to at least one oxide selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O value. A submerged arc welding method is a submerged arc welding method using a flux for arc welding, characterized in that the used flux contains: fluoride and oxide, and the oxide is a high melting point with a melting point of 1800°C or higher. Oxides and low melting point oxides with a melting point of less than 1800°C, and include: oxides containing Ca as the high melting point oxides and oxides containing Mn as the low melting point oxides. The total content of Mn is 2 to 8% by mass in terms of MnO, and the above-mentioned MnO conversion value, CaF ₂ conversion value of F, CaO conversion value of Ca, and CO ₂ satisfy 1.6≦{CaF ₂ conversion value/( The relationship between MnO conversion value + CaO conversion value + CO ₂ )}, the ratio of the total content of the refractory oxides to the total content of the oxides (the total content of the refractory oxides / the content of the oxides The total content) is 0.56 or more, the high melting point oxide contains at least one of MgO and TiO ₂ , and the content of the total mass of the flux is MgO conversion value of 25 mass % or less, and Ti TiO ₂ The converted value is 9 mass % or less, the ratio of the content of the sum of the above-mentioned MgO-converted value and the above-mentioned _TiO2 -converted value to the total content of the above-mentioned refractory oxide {(MgO-converted value + _TiO2 -converted value/high-melting point oxide The content of the sum total of the substances} is 0.477 or more, and the content of the total flux of the flux is ₂₀ mass % or more in terms of CaF ₂ and 6.0 mass % or less. According to the submerged arc welding method of claim 5, wherein the material to be welded is processed with grooves as U grooves or V grooves, and the groove angle is 10~60°. A method for producing a flux for submerged arc welding, which is a method for producing a flux used for submerged arc welding, characterized by comprising: a process of firing granules derived from raw materials at 400 to 950° C., wherein the firing The flux after the finished process includes: fluoride and oxide, the oxide is composed of high melting point oxide with melting point above 1800℃ and low melting point oxide with melting point less than 1800℃, and includes: The oxides of Ca which are the high melting point oxides and the oxides containing Mn which are the low melting point oxides, the content of the total mass of the flux is 4 to 8 mass % in terms of MnO equivalent of Mn, and the aforementioned MnO The conversion value, the CaF ₂ conversion value of F, the CaO conversion value of Ca, and the CO ₂ satisfy the relationship of 1.6≦{CaF ₂ conversion value/(MnO conversion value+CaO conversion value+CO ₂ )}, the sum of the above-mentioned high melting point oxides The ratio of the content of MgO to the total content of the aforementioned oxides (the total content of the refractory oxides/the total content of the oxides) is 0.56 or more, and the refractory oxides contain at least one of MgO and TiO ₂ . On the one hand, the content of the total mass of the flux is 25 mass % or less in terms of MgO conversion value of Mg, and 9 mass % or less in terms of TiO ₂ conversion value of Ti, and the sum of the above-mentioned MgO conversion value and the above-mentioned TiO ₂ conversion value. The ratio {(MgO conversion value + TiO ₂ conversion value / total content of high melting point oxides} is 0.477 or more, and the content to the total mass of the flux is the above The CaF ₂ conversion value is 20 mass % or more, and the aforementioned CO ₂ is 6.0 mass % or less.