JP2019150859A - Bond flux for multielectrode single-sided submerge arc welding - Google Patents

Abstract

To provide a bond flux for multielectrode single-sided submerge arc welding which has a satisfactory weld workability and is capable of obtaining a welding metal with a satisfactory strength and a stable low-temperature toughness even in multielectrode single-sided submerge welding of three or more electrodes, in particular, in large-scaled heat input welding of a thick steel plate.SOLUTION: A bond flux for multielectrode single-sided submerge arc welding consists of, by mass %, 11-25% of total values in terms of SiO, 1-10% of total values in terms of CaO, 10-30% of total values in terms of MgO, 1-10% of total values in terms of TiO, 1-8% of total values in terms of AlO, 1-6% of total values in terms of F, 1-8% of total values in terms of CO, 1-5% of total values in terms of one or two kinds or more of NaO and KO, 0.1-3% of BO, 15-40% of Fe, 0.5-2% of Si, 0.5-1.5% of Mn, 0.1-3% of Mo, 0.1-3% of Ti, and 0.05-0.5% of Al.SELECTED DRAWING: None

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 in particular, in high heat input welding of thick steel plates, it has good welding workability, good strength and stable low temperature toughness. It is related with the bond flux for multi-electrode single-sided submerged arc welding suitable for obtaining.

  In submerged arc welding, a granular flux is dispersed in advance along the welding line, and an electrode wire is continuously supplied therein, and an arc is generated between the tip of the electrode wire and the base material to perform welding. Is a method of continuously performing. According to this submerged arc welding method, high efficiency and stable welding workability and mechanical performance of weld metal can be obtained, so a wide range of fields such as shipbuilding, steel frames, pipes, bridges, vehicles, etc. Has been applied.

  In recent years, with the development of the energy industry, high strength and high toughness of steel materials have been studied, and the increase in the thickness of structures due to the increase in size of structures has been studied. is doing. Therefore, in the submerged arc welding, further quality improvement is required in order to improve the productivity in the welding work and to ensure safety and durability.

  Especially in the shipbuilding industry, the number of large-scale bulk carriers, tankers, container carriers, etc. is increasing year by year, and in order to improve productivity and secure safety and durability in these constructions, further increase the efficiency of welding. There is a great demand for higher toughness of welds.

  The large plate joint, which is the main axis of the shipbuilding construction process, is frequently used the flux copper backing single-sided submerged arc welding method (hereinafter referred to as FCuB method) shown in FIG. In this FCuB method, about 4 to 7 mm of back flux 2 is sprayed on the backing copper plate 1, air is injected into the air hose 3, and this is pressed against the groove back surface 4 a corresponding to the back side of the steel plate 4 to be welded. And the front bead and the back bead are formed simultaneously by spraying the front flux 6 from the front side using 2 to 4 wires 5 and welding one layer. In this welding method, since the back flux 2 adheres closely to the groove back surface 4a, the backing hits well, and the back copper bead 1 under the back flux 2 suppresses the height of the back bead. Even if it is constructed under welding conditions, a beautiful back bead with no welding defects can be obtained. For this reason, the FCuB method is widely applied from a thin plate to a thick plate.

  For example, Patent Document 1 discloses a basic technique related to a high-speed single-sided submerged arc welding method using four electrodes. In order to obtain a weld metal free from sound defects in high-speed single-sided submerged arc welding, the wire diameter, welding current, welding speed, distance between electrodes, flux, and wire components are limited and improved. However, although the technique described in Patent Document 1 can obtain a weld metal having no sound defect, when the high heat input welding of a thick steel plate is performed, the tensile strength of the weld metal is lowered, and the stable low temperature is achieved. There was a problem that toughness could not be obtained.

  Patent Document 2 discloses a technique related 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 components of the flux and the particle size of the iron powder. However, the technique described in Patent Document 2 has a problem that welding workability tends to become unstable when large heat input welding of a thick steel plate is performed.

  Patent Document 3 discloses a technique for obtaining a sound back bead by using three or more electrodes, limiting the wire diameter, welding current, distance between electrodes, and electrode torch angle. However, the technique described in Patent Document 3 can obtain a sound back bead in high-speed single-sided submerged arc welding, but cannot obtain stable welding workability when large heat input welding is performed on a thick steel plate. was there.

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

  On the other hand, the present applicant has proposed a bond flux for multi-electrode single-sided submerged arc welding in which a weld metal having improved front bead and excellent mechanical performance is obtained in Patent Document 5 and Patent Document 6. However, although the technique described in Patent Document 5 can obtain good weld metal mechanical performance with a medium steel plate having a thickness of about 20 mm, the tensile strength and toughness of the weld metal are reduced in high heat input welding of a thick steel plate. There was a problem to do. In addition, the technique described in Patent Document 6 has a problem in that although a good tensile strength can be obtained in high heat input welding of a thick steel plate, the arc tends to become unstable and stable low temperature toughness cannot be obtained.

Japanese Patent Laid-Open No. 5-337651 Japanese Patent Laying-Open No. 2015-74011 JP-A-8-99178 JP 2004-154841 A JP 2012-218053 A JP2015-155111A

  Therefore, the present invention has been devised in view of the above-described problems, and when performing multi-electrode single-sided submerged arc welding of three or more electrodes, particularly when performing welding of thick steel plates having high welding heat input. Multi-electrode single-sided submerged arc with good arc stability and slag removability, excellent bead shape and appearance without weld defects such as undercut, and good weld strength and stable low temperature toughness It aims at providing the bond flux for welding.

The gist of the present invention is as follows:
(1) In the multielectrode sided submerged arc welding bonded flux, by mass% with respect to the flux to the total mass%, the sum of SiO ₂ converted value of Si oxides: 11 to 25%, the total of CaO converted value of Ca oxides: 1 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 converted value of fluorine compound: 1 to 6%, total of one or more metal carbonates converted to CO ₂ value: 1 to 8%, Na oxide and Na _{2 of} K oxide one or more of the total O converted value and K ₂ O converted _{value: 1~5%, B 2 O 3} : 0.1~3%, Fe: 15~40%, Si: 0.5~2 %, Mn: 0.5 to 1.5%, Mo: 0.1 to 3%, Ti: 0.1 to 3%, Al: 0.05 to 0.5% A, balance multielectrode sided submerged arc welding bonded flux, characterized in that it consists of inevitable impurities.

(2) The single-sided submerged arc welding according to (1), further containing, in mass% with respect to the total mass of the flux, a total of ZrO ₂ converted values of Zr oxide: 0.01 to 0.3% Bond flux.

  (3) The bond for multi-electrode single-sided submerged arc welding according to (1) or (2), characterized in that the total mass of Fe oxide is 1% or less in terms of mass% with respect to the total mass of the flux. It is 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, particularly when performing high heat input welding of thick steel plates. Bonds for multi-electrode single-sided submerged arc welding with good slag removability, excellent bead shape and appearance without weld defects such as undercut, and good weld 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 collection position of the weld metal used in the Example of this invention. It is a figure which shows the impact test piece collection 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 arc is stable, slag peelability, bead shape and appearance without welding defects such as undercut, good strength and stable low temperature toughness are obtained. In order to obtain a bond flux for multi-electrode single-sided submerged arc welding that yields a weld metal of various sizes, various studies were made on the 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 range of plate thicknesses from 8 mm to 40 mm, and the heat input increases as the plate thickness increases.

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

As a result, it was found that the arc tends to become unstable as the amount of added metal carbonate increases. Metal carbonate is pyrolyzed in the arc to generate CO or CO ₂ gas, but if the amount of gas generated is excessive, it works to hinder the progress of the molten metal, making the arc unstable and blowing up. It was found to promote Thus, 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, in order to obtain the low temperature toughness of the weld metal, it has been found that the metal carbonate in the bond flux is an essential component and cannot be removed.

For this reason, as a result of investigating the slag composition of the bond flux on the assumption that the metal carbonate is added, the Si oxide, Ca oxide, Ti oxide, Mg oxide, Al oxide, metal of the bond flux It has been found that the arc is stabilized by adding an appropriate amount of the total CO ₂ equivalent value of carbonate and the total of Na oxide and K oxide.

  Further, it has been found that the slag peelability is improved by adding appropriate amounts of Si oxide, Ca oxide, and Mg oxide, and stickiness on the bead surface is improved by adding an appropriate amount of Ti oxide.

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

  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, an 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 hardenability. However, if a deoxidizer and an alloying agent are added excessively, the hardenability of the weld metal becomes excessive, the strength increases, and the low temperature toughness decreases. Therefore, various deoxidizers, alloying agents, and slag compositions were investigated in order to develop bond fluxes corresponding to changes in welding heat input at various plate thicknesses.

As a result, it was found that good strength and low temperature toughness can be obtained by adding appropriate amounts 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 refine the microstructure of the weld metal by optimizing the addition amount of Mo, Ti and B ₂ O _{3 in} order to obtain stable low temperature toughness in high heat input welding.

  It has also been found that slag peelability is further improved by adding an appropriate amount of Zr oxide, and that the bead shape is further improved by limiting the amount of Fe oxide added.

  The reason 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. In addition, about the following component, it shall show the mass% with respect to the total mass of the bond flux for multi-electrode single-sided submerged arc welding, and when expressing the mass%, it shall be expressed simply as%.

[Total of SiO ₂ conversion value of Si oxide: 11-25%]
Si oxide is an important component for forming a good weld bead. Moreover, Si oxide and slag are made into a glassy property, and the effect which makes it easy to crush and makes slag with favorable peelability is exhibited. When the total SiO ₂ conversion value of the Si oxide is less than 11%, the fit of the bead heel end portion is deteriorated, the slag peelability is deteriorated, the bead shape / appearance is poor, and the undercut occurs. On the other hand, if the total of SiO ₂ conversion values of the Si oxide exceeds 25%, the amount of oxygen in the weld metal increases and the low temperature toughness decreases. Therefore, the total of SiO ₂ conversion values of Si oxide is 11 to 25%. Si oxide can be added from silica sand, zircon sand, wollastonite, water glass (sodium silicate, potassium silicate) or the like.

[Total of Ca oxide converted to CaO: 1 to 10%]
Ca oxide is an important component for adjusting the melting point and fluidity of the slag. If the total CaO equivalent value of the Ca oxide is less than 1%, the familiarity of the bead heel end is deteriorated, the bead shape / appearance is poor, and undercutting occurs. On the other hand, when the total CaO equivalent value of Ca oxide exceeds 10%, the slag fluidity is deteriorated, the bead height is non-uniform, and the slag peelability and the bead shape / appearance are poor. Therefore, the total CaO equivalent value of Ca oxide is 1 to 10%. In addition, Ca oxide can be added from wollastonite, calcium carbonate, or the like.

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

[Total of TiO ₂ converted values of Ti oxide: 1 to 10%]
Ti oxide has the effect of improving the arc stability. Ti oxide is also effective for the smoothness of the bead surface. If the total TiO ₂ conversion value 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 are poor. On the other hand, if the total of TiO ₂ converted 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 bead surface and the bead shape and appearance deteriorate. Therefore, the total of the TiO ₂ converted values of the Ti oxide is 1 to 10%. Ti oxide can be added from rutile, titanium oxide, titanium slag or the like.

Total of terms of Al ₂ O ₃ value of Al oxide: 1 to 8%
Al oxide has the effect of improving the slag peelability and bead appearance. Moreover, Al oxide is effective in obtaining good arc stability. If the total of Al ₂ O ₃ converted values of Al oxides is less than 1%, the arc is unstable, the slag peelability and the wavy surface of the bead surface become rough, and the bead shape and appearance deteriorate. On the other hand, if the total of Al ₂ O ₃ converted values of the Al oxide exceeds 8%, the bead shape becomes convex and the slag peelability becomes poor. Therefore, the total of Al ₂ O ₃ converted values of Al oxide is 1 to 8%. The Al oxide can be added from alumina, feldspar, silica sand or the like.

[Total F converted value of fluorine compounds: 1-6%]
The fluorine compound is an important component for adjusting the melting point and fluidity of the slag. Fluorine compounds have the effect of increasing the basicity of the flux and improving the low temperature toughness. If the total F converted value of the fluorine compound is less than 1%, the basicity of the flux is lowered, the amount of oxygen in the weld metal is increased, and the low temperature toughness is lowered. On the other hand, if the total F converted value of the fluorine compound exceeds 6%, the softening and melting point of the flux is lowered, the bead smoothness is lowered, and the bead shape / appearance is poor. Therefore, the total F converted value of the fluorine compound is 1 to 6%. The fluorine compound can be added from aluminum fluoride, fluorite or the like.

[Total of 1 or 2 kinds of metal carbonate converted to CO ₂ : 1 to 8%]
The metal carbonate decomposes in the arc and generates CO or CO ₂ gas to improve the arc stability, and has the effect of reducing nitrogen and oxygen in the arc atmosphere. If the total of one or more metal carbonates converted to CO ₂ 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 of one or more metal carbonates in terms of CO ₂ conversion exceeds 8%, the amount of CO or CO ₂ gas generated will be excessive, the arc will become unstable, and the bead shape and appearance Deteriorates. Accordingly, the total of one or more metal carbonates converted to CO ₂ is 1 to 8%. The metal carbonate can be added from calcium carbonate, magnesium carbonate, barium carbonate, manganese carbonate, iron carbonate, lithium carbonate or the like.

[Total of one or more of Na oxide and K oxide converted to Na ₂ O and K ₂ O: 1 to 5%]
Na oxide and K oxide have the effect of improving the stability of the arc. When the total of one or more of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound is less than 1%, the effect of improving the arc stability cannot be obtained. On the other hand, if the total of one or two or more of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound exceeds 5%, the gloss of the bead surface is lost and the bead appearance becomes poor. Therefore, the total of Na ₂ O equivalent value and K ₂ O equivalent value of Na oxide and K oxide is 1 to 5%. 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. When B ₂ O ₃ is less than 0.1%, variations occur in the low temperature toughness of the weld metal. On the other hand, if B ₂ O ₃ exceeds 3%, the weld metal is hardened and the low-temperature toughness is lowered. Therefore, B ₂ O ₃ is 0.1 to 3%. B ₂ O ₃ can be added from boron oxide, borax or the like.

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

[Si: 0.5-2%]
Si is a deoxidizer and has the effect of reducing the oxygen content of 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 0.5 to 2%. Si can be added from metal Si, Fe-Si, Fe-Si-Mn, or the like.

[Mn: 0.5 to 1.5%]
Mn is a deoxidizer like Si and reduces the oxygen content of the weld metal. When 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 yield is excessively increased in the weld metal, the strength is increased, and the low temperature toughness is lowered. Therefore, Mn is 0.5 to 1.5%. Mn can be added from metal Mn, Fe-Mn, Fe-Si-Mn, or the like.

[Mo: 0.1-3%]
Mo is an element that improves the hardenability of the weld metal, and in particular has an effect of ensuring the strength in high heat input welding of thick steel plates. Mo is also effective in refining the weld metal structure and stabilizing low temperature toughness. If the Mo content is less than 0.1%, the strength of the weld metal decreases, and the low-temperature toughness varies. On the other hand, if Mo exceeds 3%, the strength of the weld metal becomes excessive, and the low-temperature toughness is lowered. Therefore, Mo is 0.1 to 3%. Mo can be added from metal Mo, Fe-Mo, or the like.

[Ti: 0.1 to 3%]
Ti has the effect of refining the microstructure of the weld metal and stabilizing low temperature toughness. When Ti is less than 0.1%, the effect of refining the microstructure of the weld metal cannot be obtained, and variation occurs in the low temperature toughness. On the other hand, if Ti exceeds 3%, the strength of the weld metal increases and the low-temperature toughness decreases. Therefore, Ti is 0.1 to 3%. Ti can be added from metal Ti, Fe-Ti, or the like.

[Al: 0.05 to 0.5%]
Al is a strong deoxidizer and has the effect of improving the low temperature toughness of the weld metal, particularly in large heat input welding of thick steel plates. If the Al content is less than 0.05%, the amount of oxygen in the weld metal increases and the low temperature toughness decreases. On the other hand, if Al exceeds 0.5%, it remains in the weld metal as Al oxide and the low temperature toughness decreases. Therefore, Al is made 0.05 to 0.5%. Al can be added from metal Al, Fe-Al, or the like.

[Total ZrO ₂ conversion value of Zr oxide: 0.01 to 0.3%]
Zr oxide has the effect of improving slag peelability. If the total of ZrO ₂ converted values of the Zr oxide is less than 0.01%, the effect cannot be obtained. On the other hand, if the total of ZrO ₂ converted values of the Zr oxide exceeds 0.3%, the slag becomes dense and the slag peelability becomes poor. Therefore, the total of ZrO ₂ conversion values of the Zr oxide is set to 0.01 to 0.3%. The Zr oxide can be added from zircon sand, zircon flour, zirconium oxide or the like.

[Total FeO equivalent 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 equivalent value of the Fe oxide exceeds 1%, the bead shape and appearance become poor because the smoothness of the bead surface is impaired. Therefore, the total FeO equivalent value of the Fe oxide is 1% or less.

The balance is inevitable impurities such as P and S. Since both P and S generate a low melting point compound and lower the low temperature toughness, it is preferably as low as possible.
In the single-side welding using the bond flux for multi-electrode single-sided submerged arc welding according to the present invention, the diameter of the wire to be combined is 4 in order to perform welding capable of improving stable arc, wire feedability and welding efficiency. 0 to 6.4 mm, and applied to multi-electrode single-sided submerged arc welding with 3 or more electrodes.

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

  A welded steel plate 4 having a chemical composition shown in Table 4 and having a thickness of 40 mm using a bond flux prepared with 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. 2 was 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 conducted under the welding conditions of 2 (4 electrodes).

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

  In addition, the wires shown in Table 3 were used by drawing the raw wires to 4.8 mm and 6.4 mm diameters by reducing the diameter, annealing, pickling, and copper plating to form the strands.

  Each prototype bond flux was evaluated under the condition no. 1 or condition no. Investigate the arc stability during single-sided submerged arc welding with 2; slag peelability after welding; presence of undercut; presence of iron grain protrusions and slag sticking on the surface bead surface; bead shape and appearance; 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 sampled from the center (t / 2) of the plate thickness t of the welded steel plate 4 as shown in FIG. The Charpy impact test piece 8 (JIS Z2242 V-notch test piece) has a depth of 2 mm from the Charpy impact test piece 8F and the back surface 4c taken from the depth of 2 mm from the front surface 4b of the welded steel plate 4 as shown in FIG. Two kinds of collected Charpy impact test pieces 8R were collected. Evaluation of tensile strength made 490-690 Mpa favorable. The low temperature toughness is evaluated by a Charpy impact test at -20, and the average value of 3 repetitions is 50 J or more, the difference between the average value and the minimum value is 10 J or less, and the average value in the plate thickness direction of the steel plate 4 to be welded. Of 20J or less (difference in average value of absorbed energy between the steel plate surface side and the steel plate back side) was determined to be good. These results are summarized in Table 6.

Flux symbols F1 to F13 in Tables 1 and 6 are examples of the present invention, and flux symbols F14 to F30 are comparative examples. Flux symbols F1 to F13, which are examples of the present invention, are the SiO ₂ equivalent value of the Si oxide in the flux, the CaO equivalent value of the Ca oxide, the MgO equivalent value of the Mg oxide, and the TiO _{2 of the} Ti oxide. Total converted value, total Al ₂ O ₃ converted value of Al oxide, total F converted value of fluorine compound, total of one or more CO ₂ converted values of metal carbonate, Na oxide and K Since the total of one or more of Na ₂ O converted value and K ₂ O converted value of oxide, B ₂ O ₃ , Fe, Si, Mn, Mo, Al is appropriate, the arc is stable and under There were no cuts or iron grain protrusions on the surface bead surface and no slag sticking, and the slag peelability, bead shape and appearance were good. In addition, the tensile strength and absorbed energy energy of the weld metal were good, and the results were extremely satisfactory.

The flux symbols F2, F3, F6, F7, F9, F11, and F12 had very good slag removability because the ZrO ₂ converted value of the Zr oxide was appropriate.

  Further, since the flux symbols F4, F5, and F8 have a large amount of Fe oxide in terms of FeO, the bead shape and appearance were somewhat poor, but were practically not problematic.

Since the flux symbol 14 in the comparative example has a small SiO ₂ equivalent value of Si oxide, the fit of the bead heel end portion was poor, the surface bead shape / appearance and slag peelability were poor, and undercut occurred. Further, since the terms of ZrO ₂ value of Zr oxide is small, the effect of improving the slag removability were not obtained.

Since the flux symbol F15 has a large SiO ₂ equivalent value of Si oxide, the absorbed energy of the weld metal was low. Moreover, since there was much Fe, the iron particle protrusion generate | occur | produced on the bead surface, and slag peelability and surface bead shape and appearance were also inferior.

  In the flux symbol F16, since the Ca oxide value of Ca oxide is small, the familiarity of the end portion of the bead collar is poor, the surface bead shape / appearance is poor, and undercut occurs. Moreover, since there is little Si, the tensile strength and absorbed energy of the weld metal were low.

  Since the flux symbol F17 has many Ca oxide conversion values of Ca oxide, the slag peelability and the surface bead shape / appearance were poor. Moreover, since Mn is small, the tensile strength and absorbed energy of the weld metal were low.

Since the flux symbol F18 has a small MgO equivalent value of Mg oxide, the absorbed energy of the weld metal was low. Further, since the terms of ZrO ₂ value of Zr oxide is large, the slag removability was poor.

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

Flux code F20, since TiO ₂ converted value of Ti oxides is small, the arc is unstable, it was poor also Table bead shape and appearance. Moreover, since the B ₂ O ₃ is large, the tensile strength of the weld metal becomes high and the absorbed energy were low.

Since the flux symbol F21 has many TiO ₂ converted values of Ti oxide, the slag peelability was poor, the slag was stuck to the bead surface, and the surface bead shape and appearance were also poor. Moreover, since there was much Mn, the tensile strength of the weld metal became high and the absorbed energy was low.

Flux code F22, since in terms of Al ₂ O ₃ value of Al oxide is small, the arc is unstable, Table bead shape and appearance and the slag removability was also poor. Moreover, since there was little Mo, the tensile strength of the weld metal was low, and the difference between the average value and the minimum value of the absorbed energy and the difference between the average values in the plate thickness direction were large.

Since the flux symbol F23 has many Al ₂ O ₃ converted values of Al oxide, the surface bead shape / appearance and slag peelability were poor. Moreover, since there is much Mo, the tensile strength of a weld metal became high and the absorbed energy was low.

  In the flux symbol F24, the F-converted value of the fluorine compound is small, so the absorbed energy of the weld metal is low. Further, since Fe was small, the back bead shape / appearance was poor and undercutting occurred.

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

The flux symbol F26 had a small total of CO ₂ equivalent values of one or more metal carbonates, so that the arc was unstable and the surface bead shape and appearance were poor. Moreover, the absorbed energy of the weld metal was low.

Since the flux symbol F27 has a large total of one or more of Na oxide and K oxide converted to Na ₂ O and K ₂ O, the surface bead shape and appearance were poor. Moreover, since there is much Al, the absorbed energy of the weld metal was low.

In the flux symbol F28, since the total of one or more of Na ₂ O equivalent value and K ₂ O equivalent value of Na oxide and K oxide was large, the arc was unstable. Further, 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 values in the thickness direction were large.

  Since the flux symbol F29 has a large amount of Ti, the tensile strength of the weld metal was high and the absorbed energy was low. Moreover, since there were many FeO conversion values of Fe oxide, the surface bead shape and external appearance were unsatisfactory.

Flux code F30, since the sum of one or more of CO ₂ in terms of the metal carbonate is large, the arc is unstable, Table bead shape and appearance was poor. Moreover, since there is much Si, the tensile strength of a weld metal became high and the absorbed energy was a low value.

DESCRIPTION OF SYMBOLS 1 Back copper plate 2 Back flux 3 Air hose 4 Welded steel plate 4a Groove back surface 5 Wire 6 Front flux 7 Tensile test piece 8F, 8R Impact test piece

Claims (3)

In the bond flux for multi-electrode single-sided submerged arc welding, in mass% with respect to the total mass of the flux,
Total of SiO ₂ conversion value of Si oxide: 11 to 25%,
Total CaO equivalent value of Ca oxide: 1 to 10%,
Total MgO equivalent value of Mg oxide: 10-30%,
Total of TiO ₂ conversion value of Ti oxide: 1 to 10%,
Total terms of Al ₂ O ₃ value of Al oxide: 1 to 8%
Total of F converted values of fluorine compounds: 1 to 6%,
Total of one or more metal carbonates in terms of CO ₂ equivalent: 1 to 8%,
One or more of the total Na oxide and terms of Na ₂ O values and K ₂ O conversion value of K oxide: 1-5%,
B ₂ O ₃ : 0.1 to 3%,
Fe: 15-40%,
Si: 0.5-2%,
Mn: 0.5 to 1.5%
Mo: 0.1 to 3%,
Ti: 0.1 to 3%,
Al: 0.05 to 0.5% is contained,
Bond flux for multi-electrode single-sided submerged arc welding, characterized in that the balance consists of inevitable impurities. _2. The multi-electrode single-sided submerged arc welding bond according to claim 1, further comprising 0.01% to 0.3% of the total amount of Zr oxide converted to ZrO _{2 by} mass% with respect to the total mass of the flux. flux.   The bond flux for multi-electrode single-sided submerged arc welding according to claim 1 or 2, wherein the total mass of the flux is the mass% based on the FeO equivalent value of Fe oxide: 1% or less.

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