JP6908547B2 - Bond flux for multi-electrode single-sided submerged arc welding - Google Patents

Description

The present invention relates to a bond flux for multi-electrode single-sided submerged arc welding used for large plate joints such as shipbuilding, and particularly in large heat input welding of thick steel plates, it has good welding workability, good strength and stable low temperature toughness. The present invention relates to a bond flux for multi-electrode single-sided submerged arc welding suitable for obtaining.

In submerged arc welding, granular flux is sprayed along the welding line in advance, an electrode wire is continuously supplied into the flux, and an arc is generated between the tip of the electrode wire and the base metal for welding. Is a method of continuously performing. According to this submerged arc welding method, highly efficient and stable welding workability and mechanical performance of weld metal can be obtained, so that a wide range of fields including large structures such as shipbuilding, steel frames, pipes, bridges, and vehicles can be obtained. It is applied in.

In recent years, with the development of the energy industry, it has been studied to increase the strength and toughness of steel materials, and to increase the plate thickness due to the increase in size of structures, and the application ratio of high-strength or extra-thick steel materials is increasing year by year. is doing. Therefore, in submerged arc welding, further quality improvement is required in order to improve productivity, safety, and durability in welding work.

Especially in the shipbuilding industry, the number of large bulk carriers, tankers, container carriers, etc. built is increasing year by year, and welding efficiency is further improved in order to improve productivity, safety, and durability in these constructions. There is an extremely large demand for higher toughness of welded parts.

The flux copper backing single-sided submerged arc welding method (hereinafter referred to as the FCuB method) shown in FIG. 1 is often used for the large plate joint, which is the main axis of the shipbuilding construction process. In this FCuB method, the back flux 2 is sprayed on the backing copper plate 1 by about 4 to 7 mm, air is injected into the air hose 3, and this is pressed against the groove back surface 4a which is the back side of the steel plate 4 to be welded. Then, the front flux 6 is sprayed from the front side using 2 to 4 wires 5 and one-layer welding is performed to form the front bead and the back bead at the same time. In this welding method, the back flux 2 is in close contact with the groove back surface 4a, so that the backing is good, and the backing copper plate 1 under the back flux 2 suppresses the extra height of the back bead, so that a large current can be generated. A beautiful back bead with no welding defects can be obtained even if it is installed under welding conditions. Therefore, the FCuB method is widely applied from thin plates to thick plates.

For example, Patent Document 1 discloses a basic technique relating to a high-speed single-sided submerged arc welding method using four electrodes. This is an improvement by limiting the wire diameter, welding current, welding speed, distance between electrodes, flux and wire component in order to obtain a sound and defect-free weld metal in high-speed single-sided submerged arc welding. However, although it is possible to obtain a weld metal without sound defects by the technique described in Patent Document 1, the tensile strength of the weld metal is lowered in the case of large heat input welding of a thick steel plate, and the temperature is more stable. There was a problem that toughness could not be obtained.

Further, Patent Document 2 discloses a technique relating to a bond flux for single-sided submerged arc welding using three or more electrodes. This is intended to improve the sound bead shape and the mechanical performance of the weld metal by limiting the flux component and the particle size of the iron powder. However, the technique described in Patent Document 2 has a problem that the welding workability tends to be unstable when the thick steel plate is subjected to large heat input welding.

Further, Patent Document 3 discloses a technique for obtaining a sound back bead by using electrodes having three or more electrodes and limiting the wire diameter, welding current, distance between electrodes, and torch angle of the electrodes. However, although the technique described in Patent Document 3 can obtain a sound back bead in high-speed single-sided submerged arc welding, there is a problem that stable welding workability cannot be obtained in large heat input welding of thick steel sheets. was there.

Patent Document 4 discloses a technique relating to a single-sided submerged arc welding method using a single electrode. According to this method, a sound and stable bead shape and appearance can be obtained for both the front bead and the back bead by optimizing the welding speed and welding heat input. There is a problem that the efficiency is lowered and the production efficiency is remarkably lowered.

On the other hand, the applicant has proposed in Patent Documents 5 and 6 a bond flux for multi-electrode single-sided submerged arc welding, which can obtain a weld metal with improved surface beads and excellent mechanical performance. However, although the technique described in Patent Document 5 can obtain good mechanical performance of the weld metal in a medium steel plate having a plate thickness of about 20 mm, the tensile strength and toughness of the weld metal are lowered in the large heat input welding of the thick steel plate. There was a problem of doing. Further, the technique described in Patent Document 6 has a problem that although good tensile strength can be obtained in large heat input welding of a thick steel sheet, arc tends to be unstable and stable low temperature toughness cannot be obtained.

Japanese Unexamined Patent Publication No. 5-337651 JP-A-2015-74011 Japanese Unexamined Patent Publication No. 8-99178 Japanese Unexamined Patent Publication No. 2004-154841 Japanese Unexamined Patent Publication No. 2012-218053 JP-A-2015-155111

Therefore, the present invention has been devised in view of the above-mentioned problems, and is also used for performing multi-electrode single-sided submerged arc welding of three or more electrodes, and particularly for welding a thick steel plate having a high welding heat input. Multi-electrode single-sided submerged arc that has good arc stability and slag peelability, can obtain excellent bead shape and appearance without welding defects such as undercuts, and can obtain welded metal with good strength and stable low temperature toughness. It is an object of the present invention to provide a bond flux for welding.

The gist of the present invention is
(1) In the bond flux for multi-electrode single-sided submerge arc welding, _{the total SiO 2} conversion value of Si oxide: 11 to 25%, the total CaO conversion value of Ca oxide: 1 in mass% with respect to the total mass of the flux. 10%, the total of MgO converted value of Mg oxide: 10-30%, the total of TiO ₂ converted value of Ti oxides: 1-10%, the sum of terms of Al ₂ O ₃ value of Al oxide: 1 8%, total F conversion value of fluorine compound: 1 to 6%, total CO ₂ conversion value of one or more metal carbonates: 1 to 8%, Na _{2 of Na oxide and K oxide} Total of one or more types of O conversion value and K ₂ O conversion value: 1 to 5%, B ₂ O ₃ : 0.1 to 3%, Fe: 15 to 40%, Si: 0.5 to 2 %, Mn: 0.5 to 1.5%, Mo: 0.1 to 3%, Ti: 0.1 to 3%, Al: 0.05 to 0.5% , FeO of Fe oxide A bond flux for multi-electrode single-sided submerge arc welding, characterized in that the total conversion value is 1% or less, and the balance is composed of unavoidable impurities.

(2) Single-sided submerged arc welding according to (1), further containing 0.01 to 0.3% of the total _{ZrO 2} conversion value of the Zr oxide in terms of mass% with respect to the total mass of the flux. For bond flux.

According to the bond flux for multi-electrode single-sided submerged arc welding to which the present invention is applied, the arc is stable when performing multi-electrode single-sided submerged arc welding of three or more electrodes, especially when performing large heat input welding of thick steel plates. A multi-electrode single-sided submerged arc welding bond that provides excellent bead shape and appearance with good slag peelability and no welding defects such as undercuts, and provides welded metal with good strength and stable low-temperature toughness. It becomes possible to provide a flux.

It is sectional drawing which shows the flux copper backing single-sided submerged arc welding method used in the Example of this invention. It is a figure which shows the groove shape of the steel plate used in the Example of this invention. It is a figure which shows the tensile test piece sampling position of the weld metal used in the Example of this invention. It is a figure which shows the impact test piece sampling position of the weld metal used in the Example of this invention.

In the multi-electrode single-sided submerged arc welding of thick steel plates, the present inventors can obtain a bead shape and appearance with stable arc and no welding defects such as slag peeling property and undercut, and have good strength and stable low temperature toughness. In order to obtain a bond flux for multi-electrode single-sided submerged arc welding from which the weld metal of the above can be obtained, various studies were conducted on the component composition of the bond flux.

Multi-electrode high-speed single-sided submerged arc welding, which is applied to large plate joints for shipbuilding, has a wide plate thickness of 8 mm to 40 mm, and the thicker the plate thickness of the steel plate, the greater the heat input welding.

Therefore, the slag composition in the bond flux was examined in order to obtain excellent welding workability with stable arc even in high heat input welding.

As a result, it was found that the arc tends to become unstable when the amount of metal carbonate added is large. Metal carbonates thermally decompose in an arc _{to generate CO or CO 2} gas, but when the amount of gas generated becomes excessive, it works to hinder the progress of molten metal, and the arc tends to become unstable, resulting in a blow-up phenomenon. It was found that it promotes. Therefore, as a result of removing the metal carbonate, the arc stability was improved, but the effect of reducing nitrogen and oxygen in the arc atmosphere was lost, and the low temperature toughness of the weld metal was lowered. From the above, it was found that the metal carbonate in the bond flux is an essential component and cannot be removed in order to obtain the low temperature toughness of the weld metal.

Therefore, as a result of examining the slag composition of the bond flux on the premise that a metal carbonate is added, the Si oxide, Ca oxide, Ti oxide, Mg oxide, Al oxide, and metal of the bond flux are examined. It was found that the arc is stabilized by adding an appropriate amount of the total CO _{2 conversion value of the carbonate and the total of the Na oxide and the K oxide.}

It was also found that the slag peeling property was improved by adding an appropriate amount of Si oxide, Ca oxide and Mg oxide, and the sticking of the bead surface was improved by adding an appropriate amount of Ti oxide.

Furthermore, regarding the bead shape and appearance, the melting point and fluidity of the molten slag can be improved by adding an appropriate amount of Si oxide, Ca oxide, Mg oxide, Ti oxide, Al oxide, Ca oxide, and metal fluoride. It was found that by optimizing and adding an appropriate amount of iron powder, the arc concentration is enhanced and a good bead shape and appearance can be obtained.

Next, the mechanical performance of the weld metal was examined. In order to obtain a weld metal with good strength and stable low temperature toughness, a deoxidizer, alloying agent, etc. are added to the bond flux, and the basicity of the flux is increased to keep the oxygen content of the weld metal low. It is necessary to improve the hardenability. However, if an excessive deoxidizer and alloying agent are added, the hardenability of the weld metal becomes excessive, the strength becomes high, and the low temperature toughness decreases. Therefore, in order to develop a bond flux that responds to changes in the amount of heat input to welding at various plate thicknesses, various deoxidizers, alloying agents, and slag compositions were examined.

As a result, it was found that good strength and low temperature toughness can be obtained by adding an appropriate amount of Si, Mn, Mo, Ti, Al, B ₂ O _{3, Mg oxide and metal fluoride in the bond flux.} In particular, it has been found that it is effective to miniaturize the structure of the weld metal by optimizing the addition amounts _{of Mo, Ti and B 2} O _{3 in} order to obtain stable low temperature toughness in high heat input welding.

It was also found that the slag peeling property was further improved by adding an appropriate amount of Zr oxide, and the bead shape was further improved by limiting the amount of Fe oxide added.

The reasons for limiting the component composition of the bond flux for multi-electrode single-sided submerged arc welding to which the present invention is applied will be described below. Regarding the following components, the mass% with respect to the total mass of the bond flux for multi-electrode single-sided submerged arc welding shall be indicated, and when the mass% is expressed, it shall be simply expressed as%.

_{[Total SiO 2} conversion value of Si oxide: 11 to 25%]
Si oxide is an important component for forming a good weld bead. In addition, it exerts the effect of making Si oxide and slag into glassy properties to make slag that is easily crushed and has good peelability. _{If the total SiO 2} conversion value of the Si oxide is less than 11%, the bead toe end will not fit well, the slag peelability will deteriorate, the bead shape and appearance will be poor, and undercut will occur. On the other hand, when _{the total SiO 2} conversion value of the Si oxide exceeds 25%, the amount of oxygen in the weld metal increases and the low temperature toughness decreases. Therefore, the total value of Si oxide in _{terms of SiO 2} is set to 11 to 25%. The Si oxide can be added from silica sand, zircon sand, wollastonite, water glass (sodium silicate, potassium silicate) and the like.

[Total CaO conversion value of Ca oxide: 1-10%]
Ca oxide is an important component for adjusting the melting point and fluidity of slag. If the total CaO conversion value of Ca oxide is less than 1%, the bead toe end will not fit well, the bead shape and appearance will be poor, and undercut will occur. On the other hand, if the total CaO conversion value of the Ca oxide exceeds 10%, the slag fluidity becomes poor, the bead height becomes non-uniform, and the slag peelability and the bead shape / appearance become poor. Therefore, the total CaO conversion value of Ca oxide is 1 to 10%. The Ca oxide can be added from wollastonite, calcium carbonate and the like.

[Total MgO conversion value of Mg oxide: 10 to 30%]
Mg oxide has the effect of improving the fire resistance and basicity of slag and reducing the amount of oxygen in the weld metal. When the total MgO conversion value of the Mg oxide is less than 10%, the basicity of the flux becomes low, the amount of oxygen in the weld metal increases, and the low temperature toughness decreases. On the other hand, when the total MgO conversion value of the Mg oxide exceeds 30%, the softening and melting point of the flux becomes high, the wavy surface of the bead becomes rough, and the slag peelability and the bead shape / appearance become poor. Therefore, the total MgO conversion value of Mg oxide is set to 10 to 30%. The Mg oxide can be added from magnesia clinker, magnesium carbonate and the like.

[Total of TiO ₂ conversion values of Ti oxide: 1 to 10%]
Ti oxide has the effect of improving arc stability. Ti oxide is also effective for the smoothness of the bead surface. _{If the total of the TIO 2} conversion values of the Ti oxide is less than 1%, the arc is unstable, the effect of improving the smoothness of the bead surface cannot be obtained, and the bead shape and appearance become poor. On the other hand, when _{the total of the TIO 2} conversion values of the Ti oxide exceeds 10%, the slag becomes dense and the slag peelability becomes poor. In addition, the slag tends to stick to the surface of the bead, and the shape and appearance of the bead deteriorate. Therefore, _{the total TiO 2} conversion value of Ti oxide is 1 to 10%. The Ti oxide can be added from rutile, titanium oxide, titanium slag and the like.

_{[Total Al 2} O ₃ conversion value of Al oxide: 1-8%]
Al oxide has the effect of improving the slag exfoliation property and the bead appearance. Al oxide is also effective in obtaining good arc stability. _{If the total Al 2} O ₃ conversion value of the Al oxide is less than 1%, the arc is unstable, the slag peeling property and the wavy surface of the bead become rough, and the bead shape and appearance deteriorate. On the other hand, when _{the total Al 2} O ₃ conversion value of Al oxide exceeds 8%, the bead shape becomes convex and the slag peelability becomes poor. Therefore, _{the total Al 2} O ₃ conversion value of Al oxide is 1 to 8%. Al oxide can be added from alumina, feldspar, silica sand and the like.

[Total F conversion value of fluorine compounds: 1 to 6%]
Fluorine compounds are important components for adjusting the melting point and fluidity of slag. Further, the fluorine compound has an effect of increasing the basicity of the flux and improving the low temperature toughness. When the total F conversion value of the fluorine compound is less than 1%, the basicity of the flux becomes low, the amount of oxygen in the weld metal increases, and the low temperature toughness decreases. On the other hand, when the total F-converted value of the fluorine compound exceeds 6%, the softening and melting point of the flux becomes low, the bead smoothness deteriorates, and the bead shape and appearance become poor. Therefore, the total F conversion value of the fluorine compound is 1 to 6%. The fluorine compound can be added from aluminum fluoride, fluorite and the like.

_{[Total CO 2} conversion value of one or more metal carbonates: 1-8%]
The metal carbonate has the _{effect of decomposing in the arc to generate CO or CO 2} gas, improving the arc stability, and reducing nitrogen and oxygen in the arc atmosphere. _{If the total CO 2} conversion value of one type or two or more types of metal carbonate is less than 1%, the arc becomes unstable and the bead shape / appearance becomes poor. In addition, nitrogen and oxygen in the weld metal increase and low temperature toughness decreases. _{On the other hand, if the total CO 2} conversion value of one or more types of metal carbonate exceeds 8%, the _{amount of CO or CO 2} gas generated becomes excessive, and the arc becomes unstable and the bead shape and appearance. Deteriorates. _{Therefore, the total CO 2} conversion value of one or more metal carbonates is 1 to 8%. The metal carbonate can be added from calcium carbonate, magnesium carbonate, barium carbonate, manganese carbonate, iron carbonate, lithium carbonate and the like.

_{[Total of one or more Na 2} O conversion values and K ₂ O conversion values of Na oxide and K oxide: 1 to 5%]
Na oxide and K oxide have the effect of improving the stability of the arc. _{If the total of one or more of the Na 2} O conversion value and the K ₂ O conversion value of the Na compound and the K compound is less than 1%, the effect of improving the arc stability cannot be obtained. On the other hand, if the _{sum of one or more of the Na 2} O conversion value and the K ₂ O conversion value of the Na compound and the K compound exceeds 5%, the gloss of the bead surface is lost and the bead appearance becomes poor. _{Therefore, the total of the Na 2} O conversion value and the K ₂ O conversion value of Na oxide and K oxide is 1 to 5%. In addition, Na oxide and K oxide can be added from sodium silicate, potassium silicate, potassium feldspar and the like in water glass.

[B ₂ O ₃ : 0.1 to 3%]
B ₂ O ₃ has the effect of refining the microstructure of the weld metal and stabilizing the low temperature toughness of the weld metal. If B ₂ O ₃ is less than 0.1%, the low temperature toughness of the weld metal will vary. On the other hand, when B ₂ O ₃ exceeds 3%, the weld metal is hardened and the low temperature toughness is rather lowered. Therefore, B ₂ O ₃ is 0.1 to 3%. B ₂ O ₃ can be added from boron oxide, borax, etc.

[Fe: 15-40%]
Fe has the effect of improving the welding efficiency and the concentration of the arc to stabilize the bead shape. If Fe is less than 15%, the welding efficiency is lowered, the concentration of arcs is poor, the shape of the back bead is poor, and undercut occurs. On the other hand, if Fe exceeds 40%, iron grain protrusions are generated on the bead surface, the bead shape and appearance are deteriorated, and the slag peelability is also poor. Therefore, Fe is set to 15 to 40%. Fe can be added from iron powder, Fe-Si, Fe-Mn, Fe-Mo, and the like.

[Si: 0.5-2%]
Si is an antacid and has the effect of reducing the amount of oxygen in the weld metal. If Si is less than 0.5%, the deoxidizing effect cannot be obtained, and the strength and low temperature toughness of the weld metal are lowered. On the other hand, when Si exceeds 2%, the strength of the weld metal increases and the low temperature toughness decreases. Therefore, Si is set to 0.5 to 2%. In addition, Si can be added from metal Si, Fe-Si, Fe-Si-Mn and the like.

[Mn: 0.5 to 1.5%]
Mn is a deoxidizer like Si and reduces the amount of oxygen in the weld metal. If Mn is less than 0.5%, the deoxidizing effect cannot be obtained, and the strength and low temperature toughness of the weld metal are lowered. On the other hand, when Mn exceeds 1.5%, the weld metal is excessively yielded, the strength is increased, and the low temperature toughness is lowered. Therefore, Mn is set to 0.5 to 1.5%. In addition, Mn can be added from metal Mn, Fe-Mn, Fe-Si-Mn and the like.

[Mo: 0.1 to 3%]
Mo is an element that improves the hardenability of the weld metal, and is particularly effective in ensuring the strength of thick steel sheets in large heat input welding. Mo is also effective in refining the structure of the weld metal to stabilize low temperature toughness. If Mo is less than 0.1%, the strength of the weld metal is lowered and the low temperature toughness varies. On the other hand, when Mo exceeds 3%, the strength of the weld metal becomes excessive, and the low temperature toughness is rather lowered. Therefore, Mo is 0.1 to 3%. In addition, Mo can be added from metal Mo, Fe-Mo and the like.

[Ti: 0.1 to 3%]
Ti has the effect of refining the microstructure of the weld metal and stabilizing the low temperature toughness. If Ti is less than 0.1%, the effect of miniaturizing the microstructure of the weld metal cannot be obtained and the low temperature toughness varies. On the other hand, when Ti exceeds 3%, the strength of the weld metal increases and the low temperature toughness decreases. Therefore, Ti is set to 0.1 to 3%. In addition, Ti can be added from metal Ti, Fe-Ti and the like.

[Al: 0.05 to 0.5%]
Al is a strong deoxidizer and has an effect of improving the low temperature toughness of the weld metal, especially in large heat input welding of thick steel sheets. When Al is less than 0.05%, the amount of oxygen in the weld metal increases and the low temperature toughness decreases. On the other hand, when Al exceeds 0.5%, it remains as an Al oxide in the weld metal and the low temperature toughness is lowered. Therefore, Al is set to 0.05 to 0.5%. In addition, Al can be added from metal Al, Fe-Al and the like.

_{[Total ZrO 2} conversion value of Zr oxide: 0.01-0.3%]
Zr oxide has the effect of improving the slag exfoliation property. _{If the total ZrO 2} conversion value of the Zr oxide is less than 0.01%, the effect cannot be obtained. On the other hand, when _{the total of the ZrO 2} conversion values of the Zr oxide exceeds 0.3%, the slag becomes dense and the slag peelability becomes poor. Therefore, _{the total ZrO 2} conversion value of Zr oxide is 0.01 to 0.3%. The Zr oxide can be added from zircon sand, zircon flower, zirconium oxide and the like.

[Total FeO conversion value of Fe oxide: 1% or less]
Fe oxide is contained in a trace amount in Ti oxide and Mg oxide. However, if the total FeO conversion value of Fe oxide exceeds 1%, the smoothness of the bead surface is impaired, resulting in poor bead shape and appearance. Therefore, the total FeO conversion value of Fe oxide is set to 1% or less.

The balance is unavoidable impurities such as P and S, and both P and S generate compounds having a low melting point and lower the low temperature toughness, so it is preferably as low as possible.
In the single-sided welding using the bond flux for multi-electrode single-sided submerged arc welding of the present invention, the wire diameters to be combined are 4. It is 0 to 6.4 mm and is applied to multi-electrode single-sided submerged arc welding with 3 or more electrodes.

Hereinafter, the effects of the present invention will be described in more detail with reference to Examples.

A steel sheet 4 to be welded with a chemical composition shown in Table 4 and a thickness of 40 mm, using a bond flux prepared by adjusting various flux components shown in Table 1, a back flux having a chemical composition shown in Table 2, and a wire having a chemical composition shown in Table 3. Is processed into a groove shape with a groove angle of 45 ° and a root face of 6 mm as shown in FIG. 1 (3 electrodes) or condition No. An FCuB single-sided submerged arc welding test was carried out under the welding conditions of 2 (4 electrodes).

The bond flux shown in Table 1 was granulated using water glass as a fixing agent and then fired at 400 to 550 ° C. for 2 hours to adjust the particle size to 1.4 × 0.15 mm.

The wires shown in Table 3 were used by reducing the diameter, annealing, pickling, and copper-plating the original wires to obtain strands, and drawing those strands to diameters of 4.8 mm and 6.4 mm.

The evaluation of each prototype bond flux is based on the condition No. 1 or condition No. Investigate the arc stability during single-sided submerged arc welding according to 2, slag peelability after welding, presence or absence of undercut, presence or absence of iron grain protrusions and slag sticking on the surface of the front bead, bead shape and appearance, and further tension of weld metal. The strength and low temperature toughness were investigated.

For the mechanical performance evaluation of the weld metal, a tensile test piece 7 (JIS Z 2241 10) was taken from the center (t / 2) of the plate thickness t of the steel plate 4 to be welded as shown in FIG. As shown in FIG. 4, the Charpy impact test piece 8 (JIS Z2242 V-notch test piece) is taken from a depth of 2 mm from the front surface 4b of the steel plate 4 to be welded and from a depth of 2 mm from the back surface 4c and the Charpy impact test piece 8F. Two types of collected Charpy impact test pieces 8R were collected. The tensile strength was evaluated as good at 490 to 690 Mpa. The low temperature toughness was evaluated by the Charpy impact test at -20, and the average value of each of the three repetitions was 50 J or more, the difference between the average value and the minimum value was 10 J or less, and the average value in the thickness direction of the steel sheet 4 to be welded. (Difference in average value of absorbed energy between the front side of the steel plate and the back side of the steel plate) was set to be good at 20 J or less. These results are summarized in Table 6.

The flux symbols F1 to F3, F6 to F7, and F9 to F13 in Tables 1 and 6 are examples of the present invention, and the flux symbols F14 to F30 are comparative examples. The flux symbols F1 to F3, F6 to F7, and F9 to F13, which are examples of the present invention, are _{the total of the SiO 2} conversion value of the Si oxide in the flux, the CaO conversion value of the Ca oxide, and the MgO conversion value of the Mg oxide. Total, total TiO ₂ conversion value of _{Ti oxide, total Al 2} O ₃ conversion value of Al oxide, total F conversion value of fluorine compound, CO ₂ conversion value of one or more kinds of metal carbonates , The total of one or more of _{the Na 2} O conversion value and the K ₂ O conversion value of Na oxide and K oxide _{, and B 2} O ₃ , Fe, Si, Mn, Mo, and Al are appropriate. Therefore, the arc was stable, there was no undercut, iron grain protrusions on the surface of the front bead, and slag sticking, and the slag peelability, bead shape, and appearance were good. In addition, the tensile strength and absorbed energy of the weld metal were also good, which was an extremely satisfactory result.

As for the flux symbols F2, F3, F6, F7, F9, F11, and F12, the ZrO ₂ conversion value of the Zr oxide was appropriate, so that the slag peeling property was very good.

In the comparative example, the flux symbol 14 has a _{small SiO 2} conversion value of the Si oxide, so that the bead toe end is not well-fitted, and the surface bead shape / appearance and slag peelability are poor, and undercut occurs. Further, since the ZrO ₂ conversion value of the Zr oxide was small, the effect of improving the slag peelability could not be obtained.

Since the flux symbol F15 has a _{large value of Si oxide in terms of SiO 2} , the absorbed energy of the weld metal is low. Further, since a large amount of Fe was generated, iron grain protrusions were generated on the surface of the bead, and the slag peelability and the shape and appearance of the surface bead were also poor.

Since the flux symbol F16 has a small CaO conversion value of Ca oxide, the bead toe end is not well fitted, the surface bead shape and appearance are poor, and undercut occurs. Further, since the amount of Si was small, the tensile strength and absorbed energy of the weld metal were low.

Since the flux symbol F17 has a large CaO conversion value of Ca oxide, the slag peelability and the surface bead shape / appearance were poor. Further, since Mn was small, the tensile strength and absorbed energy of the weld metal were low.

Since the flux symbol F18 has a small MgO conversion value of Mg oxide, the absorbed energy of the weld metal is low. In addition, since the Zr oxide _{had a large ZrO 2} conversion value, the slag peelability was poor.

Since the flux symbol F19 has a large MgO conversion value of Mg oxide, the slag peelability and the surface bead shape / appearance were poor. Moreover, since the amount of Al is small, the absorbed energy of the weld metal is low.

Since the flux symbol F20 has a _{small TiO 2} conversion value of the Ti oxide, the arc is unstable and the shape and appearance of the front bead are also poor. Moreover, since the amount of B ₂ O ₃ was large, the tensile strength of the weld metal was high and the absorbed energy was low.

Since the flux symbol F21 has a _{large TiO 2} conversion value of the Ti oxide, the slag peelability was poor, the slag stuck to the bead surface, and the surface bead shape and appearance were also poor. Further, since the amount of Mn is large, the tensile strength of the weld metal is high and the absorbed energy is low.

Since the flux symbol F22 has a _{small Al 2} O ₃ conversion value of Al oxide, the arc is unstable, and the surface bead shape / appearance and slag peelability are also poor. Further, since the amount of Mo was small, the tensile strength of the weld metal was low, and the difference between the average value and the minimum value of absorbed energy and the difference between the average value in the plate thickness direction were large.

Since the flux symbol F23 has a _{large Al 2} O ₃ conversion value of Al oxide, the surface bead shape / appearance and slag peelability were poor. Further, since the amount of Mo was large, the tensile strength of the weld metal was high and the absorbed energy was low.

Since the flux symbol F24 has a small F conversion value of the fluorine compound, the absorbed energy of the weld metal is low. In addition, since the amount of Fe is small, the shape and appearance of the back bead are poor and undercut occurs.

Since the flux symbol F25 has a large F conversion value of the fluorine compound, the surface bead shape and appearance were poor. Further, since Ti was small, the difference between the average value and the minimum value of the absorbed energy and the difference between the average value in the plate thickness direction were large.

_{Since the total of the CO 2} conversion values of one type or two or more types of metal carbonate is small in the flux symbol F26, the arc is unstable and the shape and appearance of the table bead are also poor. In addition, the absorbed energy of the weld metal was low.

Since the flux symbol F27 has a _{large sum of one or more of the Na 2} O conversion value and the K ₂ O conversion value of Na oxide and K oxide, the shape and appearance of the table bead are poor. Moreover, since the amount of Al is large, the absorbed energy of the weld metal is low.

Since the flux symbol F28 has a large sum of one or more of _{the Na 2} O conversion value and the K _{2 O conversion value of Na oxide and K oxide, the arc was unstable.} Moreover, since B ₂ O ₃ was small, the difference between the average value and the minimum value of the absorbed energy and the difference between the average value in the plate thickness direction were large.

Since the flux symbol F29 has a large amount of Ti, the tensile strength of the weld metal is high and the absorbed energy is low. In addition, since the FeO conversion value of Fe oxide is large, the shape and appearance of the table bead are poor.

_{Since the flux symbol F30 has a large sum of the CO 2} conversion values of one type or two or more types of metal carbonates, the arc is unstable and the shape and appearance of the table bead are poor. Further, since the amount of Si is large, the tensile strength of the weld metal is high and the absorbed energy is low.

1 Back contact copper plate 2 Back flux 3 Air hose 4 Steel plate to be welded 4a Groove back surface 5 Wire 6 Front flux 7 Tensile test piece 8F, 8R Impact test piece

Claims (2)

In the bond flux for multi-electrode single-sided submerged arc welding, by mass% of the total mass of the flux,
_{Total SiO 2} conversion value of Si oxide: 11-25%,
Total CaO conversion value of Ca oxide: 1-10%,
Total MgO equivalent of Mg oxides: 10-30%,
Total of Ti Oxide _{converted to TIO 2} : 1-10%,
_{Total Al 2} O ₃ conversion value of Al oxide: 1-8%,
Total F conversion value of fluorine compound: 1-6%,
_{Total CO 2} equivalent of one or more metal carbonates: 1-8%,
_{Na 2} O conversion value of Na oxide and K oxide and one or more total of _{K 2 O conversion value:}
1-5%,
B ₂ O ₃ : 0.1 to 3%,
Fe: 15-40%,
Si: 0.5-2%,
Mn: 0.5-1.5%,
Mo: 0.1 to 3%,
Ti: 0.1 to 3%,
Al: Contains 0.05-0.5%,
Total FeO conversion value of Fe oxide: 1% or less,
A bond flux for multi-electrode single-sided submerged arc welding, characterized in that the rest is composed of unavoidable impurities. _{Total ZrO 2} conversion value of Zr oxide as a mass% of the total mass of the flux: 0.01
The bond flux for multi-electrode single-sided submerged arc welding according to claim 1, further containing ~ 0.3%.

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