Single-sided submerged arc welding method, backing flux and backing flux

Abstract

A single-sided submerged arc welding method, a supporting flux, and a backing flux are provided, resulting in a highly stable back weld bead and a good back weld bead appearance. The single-sided submerged arc welding method involves butt-welding a pair of steel plates (1a, 1b) to form a bevel, placing a backing flux (10) in contact with the back side of the bevel, and welding from the surface side of the bevel. The backing flux (10) comprises a slag-forming flux (2) constituting the upper layer and a supporting flux (3) constituting the lower layer. Both the slag-forming flux (2) and the supporting flux (3) contain resin. The supporting flux (3) contains one or more of the following components: an acidic oxide with a melting point of 1600°C or higher containing only one metallic element, and an amphoteric oxide with a melting point of 2000°C or higher containing only one metallic element, totaling 43% by mass or more. The aforementioned components in the slag-forming flux (2) are less than 43% by mass.

Description

Technical Field

[0001] The present invention relates to a single-sided submerged arc welding method for welding steel plates from one side, and a support flux and a backing flux for this welding method. Background Technology

[0002] Single-sided submerged arc welding, which involves welding steel plates from one side, is a highly efficient welding method used in a wide range of fields, primarily shipbuilding, as a butt welding technique. In this method, to obtain a good back weld bead, a backing flux is applied to the back side of the bevel formed in the steel plate.

[0003] For example, Patent Document 1 discloses a molten backing flux for single-sided welding, which comprises flux raw materials and a thermosetting resin, and has a bulk density of 1.20 to 1.45 g / cm³. 3 The description further states that the flux raw materials contain, by weight, CaF2: 5.0 to 20.0 wt%, ZrO2: 5.0 to 25.0 wt%, MgO: 20.0 to 40.0 wt%, SiO2: 30.0 to 50.0 wt%, TiO2: 1.0 to 5.0 wt%, MnO: 0.5 to 5.0 wt%, CaO: 0.3 to 5.0 wt%, and Al2O3: 0.3 to 5.0 wt%, with the balance consisting of trace components and unavoidable impurities of less than 1 wt% by weight.

[0004] Furthermore, it is stated that when the contents of CaF2, ZrO2, TiO2, and MnO are set to [CaF2], [ZrO2], [TiO2], and [MnO] respectively, calculated by the formula A = ([CaF2] + [ZrO2]) / ([TiO2] + [MnO]), A is 2.0 to 9.0% by weight, and the thermosetting resin is 0.5 to 15% by weight in the total weight of the backing flux.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 10-314983 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, in recent years, with the aim of improving efficiency and strength, the steel plates used for welding have become thicker, and the thicker the plate, the greater the heat input required. Therefore, due to the heat effect, the height of the weld bead on the back side tends to be unstable.

[0010] Even when using the backing flux described in Patent Document 1, it is still difficult to obtain a sufficiently well-shaped back weld bead when the welding object is a thick steel plate. As a result, there is an increasing demand for welding methods that can obtain a more stable back weld bead height.

[0011] The present invention addresses this problem and aims to provide a single-sided submerged arc welding method, a supporting flux, and a backing flux, which ensures stable back weld height even when welding thick plates, resulting in a good back weld appearance.

[0012] Problem-solving methods

[0013] The inventors have conducted intensive research on a single-sided submerged arc welding method for obtaining a stable back weld bead height and a good back weld bead appearance. Their findings indicate that by using a double-layer structure for the conventionally used backing flux, employing an easily molten resin-based flux as the upper layer and a resin-based flux that is not easily molten, or even if it melts slightly, has high viscosity of slag, the aforementioned problems can be solved.

[0014] This invention is based on these findings.

[0015] The above-mentioned objective of the present invention is achieved by the following [1] configuration relating to a single-sided submerged arc welding method.

[0016] [1] A single-sided submerged arc welding method, wherein a pair of steel plates are butt-jointed to form a bevel, a backing flux is disposed in contact with the back side of the bevel, and welding is performed from the surface side of the bevel, wherein...

[0017] The backing flux comprises a slag-forming flux forming the upper layer and a support flux forming the lower layer.

[0018] Both the slag-forming flux and the supporting flux contain resin.

[0019] The slag-forming flux, in the presence of acidic oxides with a melting point above 1600℃ and containing only one metallic element, and amphoteric oxides with a melting point above 2000℃ and containing only one metallic element, has a total content of one or more of these elements below 43% by mass (including 0%).

[0020] The supporting flux contains one or more of the following: an acidic oxide with a melting point of 1600°C or higher and containing only one metal element, and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metal element, with a total content of 43% or more.

[0021] Furthermore, the preferred embodiments of the present invention for the single-sided submerged arc welding method relate to the following [2] to [8].

[0022] [2] According to the single-sided submerged arc welding method described in [1], wherein, relative to the total mass of the slag-forming flux, the total amount of slag-forming flux with a particle size of 400 μm or more is F. U400 (mass%), the total amount of slag-forming flux with a particle size of less than 212 μm is F U212 When (mass%),

[0023] By F U400 / F U212 The calculated value is below 0.30.

[0024] Relative to the total mass of the supporting flux, let the total amount of supporting flux with a particle size of 400 μm or larger be F. L400 (mass%), the total amount of support flux with a particle size of less than 212 μm is F L212 When (mass%),

[0025] By F L400 / F L212 The calculated value is above 0.50 and below 3.80.

[0026] [3] According to the single-sided submerged arc welding method described in [1] or [2], wherein the slag-forming flux contains more than 1.0% by mass and less than 5.0% by mass of resin relative to the total mass of the slag-forming flux.

[0027] [4] The single-sided submerged arc welding method according to any one of [1] to [3], wherein the supporting flux contains 1.0% by mass and 5.0% by mass of resin relative to the total mass of the supporting flux.

[0028] [5] The single-sided submerged arc welding method according to any one of [1] to [4], wherein the thickness of the upper layer in the direction parallel to the thickness direction of the steel plate is more than 1 mm and less than 7 mm.

[0029] The thickness of the lower layer in the direction parallel to the thickness direction of the steel plate is 3 mm or more and 20 mm or less.

[0030] [6] The single-sided submerged arc welding method according to any one of [1] to [5], wherein the flux pad method is used.

[0031] [7] The single-sided submerged arc welding method according to any one of [1] to [6], wherein the thickness of the steel plate is greater than 20 mm.

[0032] [8] The single-sided submerged arc welding method according to any one of [1] to [7], wherein the total amount of support flux with a particle size of 850 μm or more is 18% by mass or less relative to the total mass of support flux.

[0033] The above-mentioned objective of the present invention is achieved by the following [9] configuration involving the support flux.

[0034] [9] A supporting flux is used in a single-sided submerged arc welding method for welding a pair of steel plates to form a bevel by butt joint approximately horizontally, wherein a supporting flux having an upper and lower layer is disposed on the lower side of a backing flux disposed on the back side of the bevel, and supporting the slag-forming flux is disposed on the lower side of the upper layer of the slag-forming flux, wherein...

[0035] The slag-forming flux is disposed on the underside of a resin-containing flux containing an acidic oxide with a melting point above 1600°C and containing only one metallic element, and an amphoteric oxide with a melting point above 2000°C and containing only one metallic element, wherein the total content of one or more of these two elements is less than 43% by mass.

[0036] The supporting flux contains a resin, and contains one or more of the following: an acidic oxide with a melting point of 1600°C or higher and containing only one metal element, and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metal element, with a total content of 43% or more.

[0037] The above-mentioned objective of the present invention is achieved by the following

[10] configuration involving the pad flux.

[0038]

[10] A backing flux is used in a single-sided submerged arc welding method for butt-welding a pair of steel plates approximately horizontally to form a bevel, and welding is performed from the upper side of the bevel, wherein the backing flux is disposed on the back side of the bevel, wherein...

[0039] It has a slag-forming flux configured to contact the back side of the bevel, and a support flux configured below the slag-forming flux.

[0040] Both the slag-forming flux and the supporting flux contain resin.

[0041] The slag-forming flux contains less than 43% by mass of one or more of the following: an acidic oxide with a melting point above 1600°C containing only one metallic element, and an amphoteric oxide with a melting point above 2000°C containing only one metallic element.

[0042] The supporting flux contains one or more of the following: an acidic oxide with a melting point of 1600°C or higher and containing only one metal element, and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metal element, with a total content of 43% or more.

[0043] Invention Effects

[0044] According to the present invention, a single-sided submerged arc welding method, a supporting flux, and a backing flux can be provided, which can ensure that the height of the back weld bead is stable even when welding thick plates, and can obtain a good back weld bead appearance. Attached Figure Description

[0045] Figure 1 This is a cross-sectional view schematically illustrating a single-sided submerged arc welding method according to an embodiment of the present invention.

[0046] Figure 2 This is a schematic cross-sectional view illustrating a single-sided submerged arc welding method using existing backing flux.

[0047] Figure 3 This is a schematic diagram illustrating a scenario in which single-sided submerged arc welding of this embodiment is performed using the flux pad method.

[0048] Symbol Explanation

[0049] 1a, 1b, 11a, 11b steel plates

[0050] 2. Slag-forming flux

[0051] 3. Support flux

[0052] 4.14 Under-layer flux

[0053] 5.15 Welding Metal

[0054] 6.16 molten slag

[0055] 10, 12 Backing Flux Detailed Implementation

[0056] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the present invention is not limited to the embodiments described below, and can be implemented in any way without departing from the essential points of the invention.

[0057] [Single-sided submerged arc welding method]

[0058] Figure 1 This is a cross-sectional view schematically illustrating a single-sided submerged arc welding method according to an embodiment of the present invention. First, a pair of steel plates 1a and 1b are joined approximately horizontally to form a bevel, and the backing flux 10 is positioned in contact with the back side of the bevel.

[0059] In this embodiment, the backing flux 10 is composed of slag-forming flux 2 forming the upper layer and support flux 3 forming the lower layer.

[0060] The lower supporting flux 3 is a flux that is difficult to melt, or even if it melts slightly, the slag has high viscosity, and it contains resin. The upper slag-forming flux 2, compared to the lower supporting flux 3, is a flux that melts easily, and like the supporting flux 3, it contains resin. The supporting flux 3 and the slag-forming flux 2 will be described in detail later.

[0061] In addition, a bottom layer flux 4 is disposed below the backing flux 10, and a surface layer flux (not shown) is spread at the bevel.

[0062] Subsequently, welding wire is fed from the upper side of the bevel towards the surface flux, and an electric arc is generated between the steel plates 1a and 1b and the welding wire.

[0063] At this point, in the backing flux 10, the area affected by the heat of the molten metal is thermally decomposed into molten slag, which covers the molten metal on the back side of the weld. Subsequently, the molten metal and molten slag are cooled and solidified, thereby forming weld metal 5 and slag 6.

[0064] Here, for comparison with this embodiment, a single-sided submerged arc welding method using existing backing flux will be described with reference to the accompanying drawings.

[0065] Figure 2 This is a schematic cross-sectional view illustrating a single-sided submerged arc welding method using existing backing flux. (Example) Figure 2 As shown, a pair of steel plates 11a and 11b are joined approximately horizontally to form a bevel, and the backing flux 12 is positioned to contact the back side of the bevel.

[0066] Furthermore, a bottom flux 14 is disposed below the backing flux 12, and a surface flux (not shown) is spread at the bevel.

[0067] Subsequently, welding wire is fed into the surface flux dispersed in the bevel, and an arc is generated between the steel plates 1a and 1b and the welding wire, thereby performing single-sided submerged arc welding.

[0068] Thus, in the existing welding method, the area in the backing flux that is affected by heat from molten metal, etc., becomes molten slag. In addition, the molten metal and molten slag are cooled to form weld metal 15 and slag 16.

[0069] However, when welding thick steel plates 11a and 11b using existing welding methods, high heat input is required, resulting in a large amount of melting of the backing flux 12 and an increase in the amount of slag generated. As a result, molten metal flows into the space formed by the melting of the backing flux 12, and the height of the back weld bead 15a exceeds the desired height. In addition, the height of the back weld bead 15a tends to become unstable.

[0070] Furthermore, in order to suppress the increase in molten slag formation, when using a difficult-to-melt backing flux 12, the backing flux 12 does not melt much, and only a small amount of molten slag is generated. Therefore, the following problems may occur: space cannot be formed for molten metal to flow in, the back weld bead 15a cannot be fully formed; and the back bevel does not melt and fusion occurs, resulting in poor appearance of the back weld bead 15a.

[0071] On the other hand, according to Figure 1 The welding method of this embodiment shown uses two fluxes: a slag-forming flux for improving the appearance of the back weld bead 5a and a support flux for maintaining a certain height of the back weld bead 5a. Therefore, it is possible to obtain a good back weld bead appearance and a stable back weld bead height.

[0072] In this invention, the method for arranging the backing flux 10 in contact with the back side of the steel plates 1a and 1b is not particularly limited. For example, the flux pad method and the copper pad method shown below can be used.

[0073] Figure 3 This is a schematic diagram illustrating the implementation of single-sided submerged arc welding using the flux pad method in this embodiment. Furthermore, in Figure 3 In China, for the sake of Figure 1 For identical or equivalent parts, the same symbol is added to the diagram and their descriptions are omitted or simplified.

[0074] like Figure 3 As shown, a pair of steel plates 1a and 1b are arranged roughly horizontally to form a bevel. On the underside of this bevel, a backing flux 10 consisting of slag-forming flux 2 and supporting flux 3 is placed. The backing flux 10 is pressed against the back side of the steel plates 1a and 1b by the pressure of the gas in the air hose 20 through the bottom flux 4 filled in the amorphous bag-shaped container 8.

[0075] Furthermore, the air hose 20 and the bottom flux 4 filled in the bag-shaped container 8 are housed in a metal box 9 with the upper surface open.

[0076] If the flux pad method is used in this way, the slag flux 2 and the support flux 3 can be held in the specified position through the air hose 20, and can be firmly pressed against the back side of the steel plates 1a and 1b.

[0077] As a method for arranging the backing flux 10 to contact the back side of the steel plates 1a and 1b, the copper pad method can also be used.

[0078] The diagram is omitted, but the copper pad method involves... Figure 3 The method shown is to replace the bottom flux with a copper plate in the flux pad method, press the pad flux 10 onto the back of the steel plates 1a and 1b, and then perform welding.

[0079] The flux pad method using only flux has the following advantages: regardless of whether the steel plates have different thicknesses or are misaligned, the backing flux and the bottom flux can be applied along the height difference generated on the back side of the steel plate. Therefore, welding can be performed regardless of whether the steel plates have different thicknesses or are misaligned.

[0080] On the other hand, the above-mentioned flux copper pad method has the advantage of easily stabilizing the height of the back solder bead because a copper plate is placed under the flux pad.

[0081] According to the single-sided submerged arc welding method of this embodiment, as the backing flux 10, the upper layer of slag-forming flux 2 and the lower layer of support flux 3 are stacked, and the support flux 3 can be used to press the molten metal. Therefore, it is not necessary to use a copper plate, and the height of the back weld bead can be stabilized.

[0082] In addition, by using the flux pad method, the height of the back weld bead can be kept stable regardless of the thickness of the steel plate or whether it is misaligned, while also obtaining a good appearance of the back weld bead.

[0083] Therefore, in this embodiment, the advantages of both the flux pad method and the copper pad method can be obtained simultaneously, making it particularly suitable.

[0084] In the single-sided submerged arc welding method of this embodiment, there are no particular restrictions on welding conditions other than the use of a specific backing flux 10, and the conditions of a conventional single-sided submerged arc welding method can be used. Regarding the electrodes, a method using one electrode or a method using two or more electrodes can be selected.

[0085] The following describes the pad flux 10, as well as the slag-forming flux 2 and the support flux 3 that constitute the pad flux 10, in more detail.

[0086] [1. Backing flux]

[0087] The backing flux 10 has a slag-forming flux 2 forming an upper layer and a support flux 3 forming a lower layer. In this embodiment, the slag-forming flux 2 is disposed in contact with the back side of the bevel, and the support flux 3 is disposed in contact with the lower side of the slag-forming flux 2. For example, a flux with other functions can be disposed on the lower side of the support flux 3.

[0088] [1-1. Supporting flux]

[0089] For the lower layer of support flux, a stable back weld bead height is required. To achieve a highly stable back weld bead, it is considered important that the support flux itself is difficult to melt, or that even if the support flux melts slightly, the slag has high viscosity. If the slag has high viscosity, it can be assumed that the slag will not penetrate below the lower layer constituting the support flux 3, but will remain at the upper part of the lower layer for slagging.

[0090] Therefore, based on the results of various studies conducted by the inventors, it is believed that, considering viscosity and melting point, acidic oxides with a melting point of 1600°C or higher and containing only one metallic element, and amphoteric oxides with a melting point of 2000°C or higher and containing only one metallic element, are effective substances as materials that meet the requirements for supporting flux.

[0091] Specifically, the inventors have discovered that by using a support flux in which the total content of one or more of an acidic oxide with a melting point of 1600°C or higher and containing only one metal element, and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metal element, is adjusted to 43% by mass or higher, a stable and high back weld bead can be obtained.

[0092] In this embodiment, the supporting flux contains one or more of the following: an acidic oxide with a melting point of 1600°C or higher and containing only one metallic element; and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metallic element, totaling 43% by mass or more. This results in a stable back-side weld bead height. For example, SiO2 is preferably used as the acidic oxide with a melting point of 1600°C or higher and containing only one metallic element. For example, Al2O3 or ZrO2 is preferably used as the amphoteric oxide with a melting point of 2000°C or higher and containing only one metallic element.

[0093] There are no particular limitations on the amount of flux that can be used, and it may include: compounds with a melting point below 1600℃ and containing only one metal element; composite compounds with a melting point below 1600℃ and containing multiple metal elements; alkaline oxides with a melting point above 1600℃ and containing only one metal element; amphoteric oxides with a melting point above 1600℃ and below 2000℃ and containing only one metal element; composite compounds with a melting point above 1600℃ and containing multiple metal elements; one or more metal powders such as Fe, Si, Mn, and Ti; and unavoidable impurities.

[0094] Compounds with melting points below 1600℃ and containing only one metallic element, such as CaF2, MnO2, Na2O, K2O, FeO, and Fe2O3. Composite compounds with melting points below 1600℃ and containing multiple metallic elements, such as CaO-MgO-SiO2-based molten fluxes. Basic oxides with melting points above 1600℃ and containing only one metallic element, such as MgO, CaO, BaO, and MnO. Amphoteric oxides with melting points above 1600℃ and below 2000℃ and containing only one metallic element, such as TiO2. Composite compounds with melting points above 1600℃ and containing multiple metallic elements, such as BaTiO3, CaTiO3, and MgAl2O4.

[0095] If the combined content of one or more of the following—acidic oxides with a melting point above 1600℃ containing only one metallic element and amphoteric oxides with a melting point above 2000℃ containing only one metallic element—is less than 43% by mass, then the supporting flux 3 will easily melt, and the viscosity of the molten slag will decrease. Therefore, the molten slag and molten metal generated by the slag-forming flux (described later) cannot be blocked at the upper end of the supporting flux 3 (lower layer). As a result, the molten slag and molten metal may enter the middle or lower part of the supporting flux 3 layer, and the height of the back weld bead 5a will be unstable.

[0096] Therefore, among the acidic oxide with a melting point of 1600°C or higher and containing only one metallic element, and the amphoteric oxide with a melting point of 2000°C or higher and containing only one metallic element, the total content of one or more of these elements is 43% by mass or more, preferably 55% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Furthermore, the total content can be 90% by mass or more, 93% by mass or more, or 95% by mass or more. While the upper limit is 100% by mass, it is preferably 99% by mass or less, more preferably 97% by mass or less. Also, the supporting flux 3 contains resin.

[0097] Acidic oxides with a melting point above 1600℃ and containing only one metallic element are not particularly limited in their form in flux. They can be made by pulverizing the monomeric amphoteric oxide or by using ore raw materials containing amphoteric oxides as flux. Similarly, amphoteric oxides with a melting point above 2000℃ and containing only one metallic element are also not particularly limited in their form in flux. They can be made by pulverizing the monomeric amphoteric oxide or by using ore raw materials containing amphoteric oxides as flux.

[0098] Here, the acidic oxides, amphoteric oxides, and composite oxides in this embodiment will be described in more detail.

[0099] Oxides are classified into three types based on their reactivity: acidic oxides that react with bases, basic oxides that react with acids, and amphoteric oxides that react with both acids and bases. Examples of acidic oxides containing only one metal element include SiO2, MoO3, and V2O5. Examples of acidic oxides containing only one metal element and having a melting point above 1600℃ include SiO2.

[0100] Examples of amphoteric oxides containing only one metallic element include Al2O3, TiO2, B2O3, ZrO2, Fe2O3, and Cr2O3. Examples of amphoteric oxides containing only one metallic element with a melting point above 2000℃ include Al2O3, ZrO2, and Cr2O3.

[0101] Composite oxides are a type of composite compound. They are oxides composed of multiple metallic elements and oxygen (O). For example, CaO-MgO-SiO2-based molten fluxes are composite oxides.

[0102] (Thickness of the lower layer consisting of supporting flux: 3mm or more and 20mm or less)

[0103] In this embodiment, because the melting point of the molten slag formed by the aforementioned supporting flux is relatively high, it can be controlled in a way that the height of the back weld bead is not too high.

[0104] If the thickness of the lower layer composed of the supporting flux is 3 mm or more, the height of the back weld bead can be stabilized. Therefore, the thickness of the lower layer is preferably 3 mm or more. On the other hand, the thickness of the lower layer is not particularly limited, but practically it is preferably 20 mm or less. Also, the term "thickness of the lower layer" refers to the thickness in the direction parallel to the thickness direction of the steel plate.

[0105] <1-1-1. Supporting the resin contained in the flux>

[0106] In this embodiment, the support flux 3 has a resin on its surface. This resin includes a thermosetting resin, which has the property of curing after melting upon heating. If the support flux has such a resin, the resin, which melts due to the heat of the molten metal and slag on the welding travel direction side of the welding torch, subsequently cures, causing the support flux 3 to adhere to each other. As a result, the fluidity of the support flux 3 and the fluidity of the molten metal can be reduced. In particular, the resin contained in the support flux 3 can reduce the fluidity of the molten metal in the longitudinal direction relative to the welding direction, i.e., the vertical direction. Therefore, by containing resin in the support flux 3, the height of the back weld bead 5a can be kept constant.

[0107] Specifically, as for the types of resins, phenolic resins, furan resins, epoxy resins, urea resins, xylene resins, etc., can be used.

[0108] Furthermore, as a method for obtaining such a support flux, one method includes adding the flux as a raw material and the aforementioned resin together to a solvent such as ethanol, methanol, or acetone, mixing them, and then drying them below the melting temperature of the resin. Also, as a support flux, a flux in which resin is coated onto the flux as a raw material can be used; however, the resin does not need to coat the entire surface of the flux as a raw material, but only needs to adhere to at least a portion of the surface.

[0109] (Resin content: ≥1.0% by mass and ≤5.0% by mass)

[0110] If the resin content in the supporting flux is 1.0% by mass or more, the powdered flux can be properly cured during welding, resulting in a better appearance of the back weld bead, as described above. Therefore, the resin content in the supporting flux is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, even more preferably 2.0% by mass or more, and particularly preferably 2.5% by mass or more.

[0111] On the other hand, if the amount of resin contained in the supporting flux is 5.0% by mass or less, the degree of curing of the powdered flux during welding can be appropriately adjusted, and as mentioned above, the appearance of the back weld bead can be improved. Therefore, the content of resin relative to the total mass of the supporting flux is preferably 5.0% by mass or less, more preferably 4.5% by mass or less, even more preferably 4.0% by mass or less, and particularly preferably 3.5% by mass or less.

[0112] [1-2. Slag-forming flux]

[0113] As described above, the slag-forming flux 2 is a flux that melts more easily than the supporting flux 3 that forms the lower layer. The supporting flux 3 contains at least 43% by mass of flux components that are difficult to melt or have high viscosity even when slightly molten, and these components are viscous. Specifically, the combined content of one or more of the following—acidic oxides with a melting point of 1600°C or higher containing only one metallic element, and amphoteric oxides with a melting point of 2000°C or higher containing only one metallic element—is limited to less than 43% by mass.

[0114] In other words, the slag-forming flux 2 contains one or more of the following: compounds with a melting point below 1600°C and containing only one metallic element; composite compounds with a melting point below 1600°C and containing multiple metallic elements; basic oxides with a melting point above 1600°C and containing only one metallic element; amphoteric oxides with a melting point above 1600°C and below 2000°C and containing only one metallic element; composite compounds with a melting point above 1600°C and containing multiple metallic elements; metal powder; and resin, in total, at least 5.7% by mass. The total content is preferably at least 60% by mass, more preferably at least 65% by mass, and even more preferably at least 70% by mass. While the upper limit is 100% by mass, it is preferably 99% by mass or less, more preferably 97% by mass or less. Like the supporting flux 3, the slag-forming flux 2 also contains resin on its surface. The balance may contain unavoidable impurities.

[0115] The alkaline oxide having a melting point above 1600℃ and containing only one metallic element is preferably an alkaline oxide having a melting point above 1600℃ and below 2900℃ and containing only one metallic element. The composite compound having a melting point above 1600℃ and containing multiple metallic elements is preferably a composite compound having a melting point above 1600℃ and below 2900℃ and containing multiple metallic elements.

[0116] If the combined content of one or more of the following—acidic oxides with a melting point above 1600℃ containing only one metallic element and amphoteric oxides with a melting point above 2000℃ containing only one metallic element—exceeds 43% by mass, it becomes the same composition as the aforementioned supporting flux 3. This results in poor melting, or even if it melts slightly, the slag has high viscosity. Consequently, a sufficient amount of slag cannot be generated, leading to poor appearance of the back weld bead. Furthermore, because it is difficult to melt below the slag-forming flux, the molten metal cannot flow below the back of the steel plates 1a and 1b, resulting in incomplete fusion at the bevel of the steel plates.

[0117] Among acidic oxides with a melting point of 1600°C or higher and containing only one metallic element, and amphoteric oxides with a melting point of 2000°C or higher and containing only one metallic element, by limiting the total content of one or more of these to less than 43% by mass, a sufficient amount of molten slag can be generated up to the bottom of the slag-forming flux 2. As a result, the molten slag can fully cover the molten metal, thus resulting in a good appearance of the back weld bead. Among acidic oxides with a melting point of 1600°C or higher and containing only one metallic element, and amphoteric oxides with a melting point of 2000°C or higher and containing only one metallic element, the total content of one or more of these is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. Furthermore, the lower limit is not particularly limited and can also be 0% by mass.

[0118] In slag-forming flux 2, if the total content of one or more of the following—acidic oxides with a melting point of 1600℃ or higher and containing only one metallic element, and amphoteric oxides with a melting point of 2000℃ or higher and containing only one metallic element—is limited to less than 43% by mass, then a backing flux for submerged arc welding can be used. For submerged arc welding backing fluxes, molten fluxes, sintered fluxes, bonding fluxes, and mixed fluxes can be used. Mixtures of molten flux and bonding flux, and mixtures of molten flux and sintered flux, can also be used.

[0119] (Thickness of the upper layer composed of slag-forming flux: 1mm or more and 7mm or less)

[0120] In this embodiment, the melting point of the molten slag formed by the aforementioned slag-forming flux is relatively low. Therefore, by appropriately adjusting the thickness of the upper layer composed of the slag-forming flux, a more ideal back weld bead can be obtained. Furthermore, the thickness of the upper layer refers to the thickness in a direction parallel to the thickness direction of the steel plate.

[0121] If the thickness of the top layer is 1 mm or more, the appropriate height of the molten metal inflow and the amount of slag will result in a better appearance of the back weld bead. On the other hand, if the thickness of the top layer is less than 7 mm, the height of the back weld bead can be maintained more consistently.

[0122] Therefore, the thickness of the upper layer is preferably 1 mm or more and 7 mm or less, more preferably 1.5 mm or more and 5 mm or less.

[0123] <1-2-1. Resin contained in slag-forming flux>

[0124] In this embodiment, the slag-forming flux 2 also has resin on its surface. The resin need only have the property of curing after melting upon heating. If the slag-forming flux has such a resin, the resin, which melts due to the heat of the molten metal and molten slag on the welding travel direction side of the welding torch, subsequently cures, causing the slag-forming flux 2 to adhere to each other. As a result, the fluidity of the slag-forming flux 2 and the fluidity of the molten metal can be reduced. In particular, the resin contained in the slag-forming flux 2 can reduce the fluidity of the molten metal in the transverse direction (left-right) relative to the welding direction. Therefore, by containing resin in the slag-forming flux 2, the height of the back weld bead 5a can be maintained at a constant level through the synergistic effect with the resin contained in the aforementioned support flux.

[0125] The types of resins, methods for obtaining slag fluxes, and forms containing resins are the same as those for the support fluxes described above.

[0126] (Resin content: ≥1.0% by mass and ≤5.0% by mass)

[0127] If the amount of resin contained in the slag-forming flux, i.e., the resin content in the slag-forming flux, is 1.0% by mass or more, then during welding, the powdered flux can be properly cured, resulting in a better appearance of the weld bead on the back side, as described above. Therefore, the resin content relative to the total mass of the slag-forming flux is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, even more preferably 2.0% by mass or more, and particularly preferably 2.5% by mass or more.

[0128] On the other hand, if the amount of resin contained in the slag-forming flux is 5.0% by mass or less, the degree of curing of the powdery flux during welding can be appropriately adjusted, as described above, resulting in a better appearance of the back weld bead. Therefore, the resin content relative to the total mass of the slag-forming flux is preferably 5.0% by mass or less, more preferably 4.5% by mass or less, even more preferably 4.0% by mass or less, and particularly preferably 3.5% by mass or less.

[0129] <1-2-2. Composition of Slag-Forming Flux>

[0130] In this embodiment, the composition of the slag-forming flux is not particularly limited as long as the conditions described in [1-2. Slag-forming flux] are met. It may contain one or more of CaF2, SiO2, TiO2, ZrO2, and MgO. In addition, it may contain one or more of the following metal powders: Fe, Si, Mn, and Ti.

[0131] In this embodiment, CaF₂ is a compound with a melting point below 1600°C and containing only one metallic element. In this embodiment, SiO₂ is an acidic oxide with a melting point above 1600°C and containing only one metallic element. In this embodiment, TiO₂ is an amphoteric oxide with a melting point above 1600°C and below 2000°C and containing only one metallic element. In this embodiment, MgO is a basic oxide with a melting point above 1600°C and containing only one metallic element. In this embodiment, ZrO₂ is an amphoteric oxide with a melting point above 2000°C and containing only one metallic element.

[0132] [2. Underlying flux]

[0133] In this embodiment, a bottom flux 4 is disposed on the underside of the backing flux 10. However, in this invention, a bottom flux 4 is not necessarily required. For example, a copper plate can be disposed on the underside of the backing flux 10 to achieve the same effect as a bottom flux 4.

[0134] When using the bottom flux, materials with excellent moisture resistance can be used as its raw materials.

[0135] [3. Other conditions]

[0136] <3-1. Particle size distribution of slag-forming flux and support flux>

[0137] (According to F) U400 / F U212 Calculated value: below 0.30

[0138] Let F be the total amount of flux formed from slag with a particle size of 400 μm or larger, relative to the total mass of the flux forming slag. U400(mass%), the total amount of flux formed by slag with a particle size of less than 212 μm is F U212 When (mass%), if from F U400 / F U212 When the calculated value is below 0.30, the gaps between the slag-forming flux particles increase, and the density decreases. Furthermore, in this embodiment, because the slag-forming flux is composed of a material that melts relatively easily, the apparent volume of the molten slag-forming flux increases, and the space created by the melting and slag-forming flux also increases. Thus, the molten metal flows into the ample space obtained described above, thereby achieving a suitable back weld bead height.

[0139] Therefore, by F U400 / F U212 The calculated value is preferably below 0.30. Furthermore, although there is no specific lower limit, it is determined by F... U400 / F U212 The calculated value is preferably 0.01 or higher.

[0140] (by F) L400 / F L212 Calculated value: 0.50 or higher and 3.80 or lower

[0141] Let F be the total amount of supporting flux with a particle size of 400 μm or larger relative to the total mass of supporting flux. L400 (mass%), the total amount of support flux with a particle size of less than 212 μm is FL. L212 When (mass%), if from F L400 / F L212 When the calculated value is above 0.50 and below 3.80, the gaps between the flux particles decrease, and the density increases. Furthermore, in this embodiment, because the flux support is composed of a relatively difficult-to-melt material, the apparent volume of the molten flux is smaller, and even when the flux melts and slags, large empty spaces are not formed. As a result, the height of the lower layer composed of flux support does not change significantly, and the positions of the molten slag and molten metal do not change significantly, thus enabling a more stable back-side weld bead height.

[0142] Therefore, by F L400 / F L212 The calculated value is preferably 0.50 or higher, more preferably 0.55 or higher. Additionally, from F... L400 / F L212 The calculated value is preferably 3.80 or less.

[0143] (Total amount of support flux with particle size greater than 850μm: less than 18% by mass (including 0% by mass))

[0144] As mentioned above, in order to reduce the gaps between the flux support particles and increase the flux support density, it is important to balance the formulation of flux with large particle size (F). L400 ) support flux, and has a small particle size (F L212 Support flux.

[0145] Furthermore, by suppressing coarse particles to a certain amount, the gap between particles can be further stabilized and reduced, resulting in a more stable height of the back weld bead.

[0146] Therefore, relative to the total mass of the supporting flux, the total amount of supporting flux with a particle size of 850 μm or more is preferably 18% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less. Furthermore, the total amount of supporting flux with a particle size of 850 μm or more is particularly preferably 0% by mass.

[0147] (Steel plate thickness: greater than 20mm)

[0148] As mentioned above, according to existing single-sided submerged arc welding methods, the thicker the plate, the greater the required heat input, and due to the heat effect, the height of the back weld bead tends to become unstable. In this embodiment, even when welding thick plates, the height of the back weld bead can be stabilized, and a good back weld bead appearance can be obtained. Therefore, the thickness of the steel plate to be welded is not particularly limited; for example, it can be applied to steel plates with a thickness greater than 20 mm. The upper limit of the thickness of the steel plate to be welded is, for example, preferably 55 mm or less.

[0149] Furthermore, the supporting flux in this embodiment is as described in [1-1. Supporting Flux] above.

[0150] In addition, the pad flux in this embodiment is as described in [1. Pad Flux] above.

[0151] (Manufacturing methods for slag-forming flux and support flux)

[0152] As a method for manufacturing the slag-forming flux and supporting flux of this embodiment, existing methods can be used. For example, it can be manufactured by mixing the raw material powder in the manner described above and then kneading it together with the resin.

[0153] There are no particular limitations on the method for adjusting the supporting flux and slag-forming flux to the target particle size. For example, the following methods can be used: any of the following methods can be used for adjustment: using raw material powder whose particle size has been adjusted by pre-sieving, etc., or adjusting the particle size distribution by sieving the mixed flux, etc.

[0154] Example

[0155] The following examples and comparative examples illustrate the invention in detail, but the invention is not limited thereto.

[0156] Single-sided submerged arc welding

[0157] As the welding materials, prepare two steel plates with a thickness of 25 mm, and prepare four electrodes, numbered 1 to 4. Additionally, prepare slag-forming fluxes and support fluxes with different compositions and particle sizes.

[0158] Next, to be applicable Figure 3 The flux pad method shown above involves preparing the aforementioned steel plate, surface flux, slag-forming flux, and support flux, and performing single-sided submerged arc welding at a welding speed of 800 mm / min.

[0159] The following shows the welding current, arc voltage, and wire diameter of the welding wire used for electrodes 1 through 4.

[0160] (Electrode 1) Welding current: 1400A, arc voltage: 35V, wire diameter: 4.0mm

[0161] (Second electrode) Welding current: 1000A, arc voltage: 32V, wire diameter: 4.8mm

[0162] (Third electrode) Welding current: 1200A, arc voltage: 44V, wire diameter: 4.8mm

[0163] (Electrode 4) Welding current: 1150A, arc voltage: 44V, wire diameter: 6.4mm

[0164] [evaluate]

[0165] For the obtained weld metal, evaluate the high stability of the back weld and the appearance of the back weld.

[0166] (Evaluation methods and criteria for the high stability of back weld beads)

[0167] For the range of 600mm to 900mm from the starting end of the steel plate, a laser displacement meter is used to measure at 0.10mm intervals, and the standard deviation is calculated to evaluate the height stability of the back weld bead.

[0168] As an evaluation standard, a standard deviation of less than 0.55 mm is ◎ (excellent), 0.55 mm or more but less than 1.00 mm is ○ (good), and 1.00 mm or more is × (poor).

[0169] (Evaluation methods and criteria for the appearance of back weld beads)

[0170] The appearance of the back weld bead is evaluated by visually inspecting it.

[0171] As an evaluation standard, good is marked with ○ and bad is marked with ×.

[0172] The type and composition of the steel plate used for welding are shown in Table 1 below, the composition of the welding wire used is shown in Table 2 below, and the composition of the surface flux is shown in Table 3 below. Furthermore, the compositions of the slag-forming flux and supporting flux of the Invention Example are shown in Tables 4 and 5 below, respectively, and the compositions of the slag-forming flux and supporting flux of the Comparative Example are shown in Tables 6 and 7 below, respectively. In addition, the particle size distribution is shown in Table 8 below, and the particle size composition, resin content (mass%), and dispersion height (mm) of the slag-forming flux and supporting flux, as well as the evaluation results, are shown in Table 9 below. In Tables 4 to 7, numerical values ​​indicate components intentionally present in the slag-forming flux and supporting flux. "-" in Tables 4 to 7 indicates components not intentionally present in the slag-forming flux and supporting flux. The total balance in Tables 4 to 7 represents unavoidable impurities not intentionally present in the slag-forming flux and supporting flux. The unavoidable impurities include trace amounts of alkaline oxides with a melting point above 1600°C and containing only one metal element, amphoteric oxides with a melting point above 1600°C and below 2000°C and containing only one metal element, compounds with a melting point below 1600°C and containing only one metal element, composite compounds with a melting point below 1600°C and containing multiple metal elements, and metal powders containing at least one of Fe, Ti, Mn, and Si, or two or more of these.

[0173] Table 1

[0174] Table 1

[0175]

[0176] Balance: Fe and unavoidable impurities

[0177] Table 2

[0178] Table 2

[0179]

[0180] Balance: Fe and unavoidable impurities

[0181] Table 3

[0182] Table 3

[0183]

[0184] *B2O3 and CaCO3, etc.

[0185] Table 4

[0186]

[0187] Table 5

[0188]

[0189] Table 6

[0190]

[0191] Table 7

[0192]

[0193] Table 8

[0194] Table 8

[0195]

[0196] Table 9

[0197] Table 9

[0198]

[0199] As shown in Tables 4-9 above, in Invention Examples No. 1-18, the upper layer of the backing flux contains resin and a slag-forming flux with specific properties specified in this invention is configured. The lower layer contains resin and a support flux with specific properties specified in this invention is configured, and single-sided submerged arc welding is performed. Therefore, the back weld bead height is stable, and a back weld bead with a good appearance can be obtained. In particular, in Invention Examples No. 1-15, No. 17, and 18, the particle size distribution of the support flux (F...) L400 / F L212 The value of ) is greater than the preferred lower limit value specified in this invention, thus achieving a more superior result in the high stability of the back weld bead.

[0200] On the other hand, in Comparative Examples No. 1 to 4, the total content of one or more of the acidic oxides with a melting point of 1600°C or higher and containing only one metallic element, and the amphoteric oxides with a melting point of 2000°C or higher and containing only one metallic element in the supporting flux shown in Table 7, deviates from the range specified in this invention. In particular, as shown in Tables 6 and 7, Comparative Example No. 1 used the same flux as the slag-forming flux as the supporting flux, resulting in a single-layer structure. Therefore, the height of the back weld bead was unstable, and the appearance of the back weld bead was also poor.

[0201] Furthermore, in Comparative Examples No. 5 to 7, the total content of one or more of the acidic oxides with a melting point of 1600°C or higher and containing only one metallic element, and the amphoteric oxides with a melting point of 2000°C or higher and containing only one metallic element in the slag-forming fluxes shown in Table 6, deviates from the range specified in this invention. In particular, in Comparative Example No. 6, the same flux as the support flux was used as the slag-forming flux, resulting in a single-layer structure. Therefore, the appearance of the back weld bead was poor.

Claims

1. A single-sided submerged arc welding method, comprising butt-welding a pair of steel plates to form a bevel, distributing a backing flux in contact with the back side of the bevel, and welding from the surface side of the bevel, wherein... The backing flux comprises a slag-forming flux forming the upper layer and a support flux forming the lower layer. The thickness of the upper layer in the direction parallel to the thickness direction of the steel plate is more than 1 mm and less than 7 mm. The thickness of the lower layer in the direction parallel to the thickness direction of the steel plate is 3 mm or more. Both the slag-forming flux and the supporting flux contain a resin that cures once it melts upon heating. The slag-forming flux contains, relative to its total mass, 1.0% to 5.0% by mass of the resin that cures upon melting under heat. The supporting flux contains, relative to its total mass, 1.0% to 5.0% by mass of the resin that cures upon melting under heat. The slag-forming flux, comprising an acidic oxide with a melting point above 1600℃ and containing only one metallic element, and an amphoteric oxide with a melting point above 2000℃ and containing only one metallic element, wherein the total content of one or more of these two types is less than 43% by mass and includes 0%. The supporting flux contains one or more of the following: an acidic oxide with a melting point of 1600°C or higher and containing only one metal element, and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metal element, with a total content of 43% or more by mass.

2. The single-sided submerged arc welding method according to claim 1, wherein, Relative to the total mass of the slag-forming flux, let the total amount of slag-forming flux with a particle size of 400 μm or larger be F, expressed as a percentage by mass. U400 The total amount of slag-forming flux with a particle size of less than 212 μm is F U212 hour, By F U400 / F U212 The calculated value is 0.30 or less, Relative to the total mass of the supporting flux, let F be the total amount of supporting flux with a particle size of 400 μm or larger, expressed as a percentage by mass. L400 The total amount of supporting flux with a particle size of less than 212 μm is F L212 hour, By F L400 / F L212 The calculated value is 0.50 or more and 3.80 or less.

3. The single-sided submerged arc welding method according to claim 1 or 2, wherein, The thickness of the lower layer in the direction parallel to the thickness direction of the steel plate is more than 3 mm and less than 20 mm.

4. The single-sided submerged arc welding method according to claim 1 or 2, wherein, Use the flux pad method.

5. The single-sided submerged arc welding method according to claim 1 or 2, wherein, The thickness of the steel plate is greater than 20 mm.

6. The single-sided submerged arc welding method according to claim 1 or 2, wherein, The total amount of supporting flux with a particle size of 850 μm or larger is less than 18% by mass relative to the total mass of the supporting flux.

7. A support flux for welding a pair of steel plates together to form a bevel, wherein the support flux is disposed on the underside of the upper slag-forming flux forming the upper layer, and is disposed on the back side of the bevel, supporting the slag-forming flux and the lower support flux, wherein... The thickness of the upper layer in the direction parallel to the thickness direction of the steel plate is more than 1 mm and less than 7 mm. The thickness of the lower layer in the direction parallel to the thickness direction of the steel plate is 3 mm or more. The slag-forming flux is disposed below the following slag-forming flux, wherein the slag-forming flux contains 1.0% by mass and 5.0% by mass of a resin that cures upon heating and melting, wherein the total content of one or more of the following—an acidic oxide with a melting point of 1600°C or higher and containing only one metallic element, and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metallic element—is less than 43% by mass. The supporting flux contains 1.0% by mass and less than 5.0% by mass of a resin that is cured upon heating after melting, and contains one or more of the following: an acidic oxide with a melting point of 1600°C or higher and containing only one metal element, and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metal element, totaling 43% by mass or more.

8. A backing flux for a single-sided submerged arc welding method of welding a pair of steel plates together to form a bevel from the upper side of the bevel, wherein the backing flux is disposed on the back side of the bevel and has upper and lower layers, wherein... It has a slag-forming flux configured to contact the back side of the bevel, and a support flux configured below the slag-forming flux. The upper layer is composed of the slag-forming flux. The lower layer is composed of the supporting flux. The thickness of the upper layer in the direction parallel to the thickness direction of the steel plate is more than 1 mm and less than 7 mm. The thickness of the lower layer in the direction parallel to the thickness direction of the steel plate is 3 mm or more. Both the slag-forming flux and the supporting flux contain a resin that cures once it melts upon heating. The slag-forming flux contains, relative to its total mass, 1.0% to 5.0% by mass of the resin that cures upon melting under heat. The supporting flux contains, relative to its total mass, 1.0% to 5.0% by mass of the resin that cures upon melting under heat. The slag-forming flux contains, in the form of an acidic oxide with a melting point above 1600℃ and containing only one metallic element, and an amphoteric oxide with a melting point above 2000℃ and containing only one metallic element, the total content of one or more of these two types is less than 43% by mass. The supporting flux contains one or more of the following: an acidic oxide with a melting point of 1600°C or higher and containing only one metal element, and an amphoteric oxide with a melting point of 2000°C or higher and containing only one metal element, with a total content of 43% or more by mass.

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