JP2014091150A - Bonded flux for multi-electrode one side submerged arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bonded flux for multi-electrode one side submerged arc welding, the bonded flux that eliminates the occurrence of iron particle projections on a top bead surface, can obtain a stable bead shape and bead appearance by forming a sound weld metal without weld defects, and further can obtain a weld metal of a superior machine performance.SOLUTION: A bonded flux for multi-electrode one side submerged arc welding contains, by mass, 7-27% SiO, 14-32% MgO, 3-15% CaO, 7-19% AlO, 4-11% CaF, 0.5-5% ZrO, 0.1-3% BO, 10-35% Fe, 0.3-4% Si, 0.1-3% Mo, and 0.1-3% Ti. In addition, the bonded flux comprises a deoxidizing agent, CO, alkali metal oxide and inevitable impurities.

Description

  TECHNICAL FIELD 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 more particularly to obtain a stable bead shape and the like and to form a weld metal with excellent mechanical performance. The present invention relates to a bond flux for arc welding.

  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, increasing the strength and toughness of steel materials, and increasing the thickness of plates due to the increase in size of structures, etc. have been studied, and the application ratio of high-strength or extremely thick steel materials has been increasing year by year. doing. Therefore, in submerged arc welding, further quality improvement is required in order to improve productivity and ensure safety and durability in welding work. There is a great demand for higher toughness.

  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 the construction, further welding is required. The demand for higher work efficiency and higher weld metal toughness is extremely high.

  For welding to the large plate joint, which is the main axis of the shipbuilding construction process, a flux copper backing single-sided submerged arc welding method (hereinafter referred to as FCuB method) shown in FIG. 1 is frequently used. 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 to each welding from a thin plate to a thick plate.

  Submerged arc welding has higher welding heat input and higher base metal dilution ratio than clad arc welding and gas shielded arc welding, so welding workability and weld metal performance are almost determined by the composition of flux and wire. The Among the submerged arc welding, the above-described single-sided submerged arc welding method is characterized by a high amount of welding heat input and a large base material dilution rate.

  In this single-sided submerged arc welding method, bond flux which is a calcined flux is mainly applied. Bond flux is made by adding water glass to various raw materials, granulated, and fired at about 500 ° C. It can be used to adjust the chemical composition of the weld metal freely and can add iron powder. There is an excellent feature that efficiency can be increased.

  However, in high-speed single-sided submerged arc welding, iron grain protrusions are likely to occur on the surface bead surface, and slag tends to stick. In particular, when the number of wire electrodes is 4 electrodes, there is a tendency that iron grain protrusions or the like are remarkably generated, and it has already been confirmed that this depends on the welding speed. That is, if the number of wire electrodes is increased, the welding speed can be increased. Therefore, the welding speed is faster with the four electrodes, and iron grain protrusions on the surface bead surface and slag sticking are likely to occur.

  In consideration of these points, a flux for submerged arc welding and a single-sided welding method that can provide good welding workability and weld metal machine performance have been proposed.

  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 of 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 without a sound defect, it cannot improve the iron grain protrusion and slag sticking on the surface bead surface, and a deoxidizer in the flux, The addition of the alloying agent is not limited. For this reason, in the case of high heat input welding of a thick plate, the tensile strength of the weld metal is lowered and the toughness is further lowered, so that there is a problem that stable welding workability and good weld metal mechanical performance cannot be obtained.

  Patent Document 2 discloses a technique relating to a high-speed single-sided submerged arc welding flux using three or more electrodes and a welding method using the same. This limits the components of the flux, further limits the particle size configuration and bulk density of the flux, and aims to improve sound front and back beads. However, since the particles having a particle size exceeding 840 μm are less than 20% by weight in the particle size configuration, the particle size of the entire flux becomes fine. As a result, the arc state during welding is finely dispersed and the arc is difficult to spread, the bead shape becomes convex, the gas escape is worsened, and welding defects such as pits and pock marks are generated. There is a problem that the front and back beads cannot be obtained.

  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. Although the technology described in Patent Document 3 can obtain a healthy back bead even at high speed by single-sided submerged arc welding, it cannot improve the iron grain protrusion and slag sticking on the surface bead surface. I can't get it.

  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 conditions, both the front bead and the back bead can obtain a sound and stable bead shape and appearance, but the welding speed is slow because of the single electrode welding. There is a problem that the welding efficiency is lowered and the production efficiency is remarkably lowered.

  Patent Document 5 discloses a technique related to a bond flux for multi-electrode high-speed single-sided submerged arc welding. This disclosed technique aims to improve iron grain protrusions and undercuts on the surface bead surface in high-speed single-sided submerged arc welding. According to the technique described in Patent Document 5, the composition of the flux composition is limited, and as a result of iron powder (Fe), which is considered to be the cause of generation of iron grain protrusions, being 5% or less, the generation of iron grain protrusions on the bead surface is Can be reduced. However, in high-speed single-sided welding, Fe in the flux is an essential component for obtaining a stable back bead shape and penetration, and can improve the welding efficiency, so that the addition amount is stable at 5% or less. Since the back bead shape cannot be obtained and the welding efficiency is also lowered, there is a problem that welding workability and production efficiency are remarkably deteriorated.

  Patent Document 6 also discloses a technique for improving iron grain protrusions and welding defects on the surface bead surface related to the bond flux for multi-electrode high-speed single-sided submerged arc welding. In the technique described in Patent Document 6, the components of the flux composition are limited in a manner similar to the technique described in Patent Document 5, and in particular, iron powder (Fe), which is considered to be the cause of the generation of iron grain protrusions, is 5% or less, and is further subjected to welding. The joint plate thickness is 16 mm or less. However, with the disclosed technique of Patent Document 6, as described above, even when the applied joint plate thickness is 16 mm or less, a stable back bead shape cannot be obtained if the Fe addition amount in the flux is 5% or less, and the welding efficiency is also low. Therefore, there is a problem that welding workability and production efficiency are remarkably deteriorated.

  In addition, the present applicant has proposed a technique related to bond flux for multi-electrode high-speed single-sided submerged arc welding, in which a weld metal with improved iron grain protrusions and welding defects on the surface bead surface and excellent mechanical performance can be obtained. The technology described in Patent Document 7 limits the components of the flux composition and further improves the iron grain protrusions on the surface bead surface by adjusting the particle size of the flux, but only by limiting the components of the flux composition and adjusting the flux particle size There was a problem that the generation of iron grain protrusions could not be completely eliminated.

Japanese Patent Laid-Open No. 5-337651 JP-A-6-277878 JP-A-8-99178 JP 2004-154841 A JP 2006-272348 A JP 2007-136516 A Japanese Patent Application No. 2011-88311

  Therefore, the present invention has been devised in view of the above-described problems, and in multi-electrode high-speed single-sided submerged arc welding with three or more electrodes, iron grain protrusions do not occur on the surface bead surface, and there is no welding defect. To provide a bond flux for multi-electrode single-sided submerged arc welding that can form a stable weld metal, obtain a stable bead shape and bead appearance on both the front bead and the back bead, and obtain a weld metal with excellent mechanical performance. With the goal.

  In order to solve the above problems, the present inventors have studied the chemical composition of the bond flux and the particle size of the iron powder raw material used for the Fe component. As a result, by limiting the chemical composition of the bond flux and further limiting the particle size of the iron powder raw material used for the Fe component, iron grain protrusions are formed on the surface bead surface even in multi-electrode high-speed single-sided submerged arc welding of three or more electrodes. It has been found that a sound weld metal that does not occur and has no weld defects can be formed, a stable bead shape and a bead appearance can be obtained on both the front and back beads, and a weld metal with excellent mechanical performance can be obtained.

That is, the gist of the present invention, in _{mass%, SiO 2: 7~27%,} MgO: 14~32%, CaO: 3~15%, Al 2 O 3: 7~19%, CaF 2: 4~11 %, ZrO ₂ : 0.5 to 5%, B ₂ O ₃ : 0.1 to 3%, Fe: 10 to 35%, Si: 0.3 to 4%, Mo: 0.1 to 3%, Ti : 0.1 to 3%, and the other is characterized by comprising a deoxidizer, CO ₂ , an alkali metal oxide and inevitable impurities.

Further, TiO ₂ : 1.5% or less, and the average particle size of the iron powder raw material used for the Fe component is 150 μm or less.

  According to the bond flux for multi-electrode single-sided submerged arc welding of the present invention, even in a multi-electrode high-speed single-sided submerged arc welding of 3 or more electrodes, iron grain protrusions are not generated on the surface bead surface, and a healthy weld metal without welding defects is formed. As a result, a stable bead shape and bead appearance can be obtained for both the front and back beads, and a weld metal having superior mechanical performance can be obtained with high efficiency.

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.

  The inventors of the present invention maintain a good weld metal mechanical performance, do not generate iron grain protrusions on the front bead surface, and obtain an excellent front and back bead shape having no welding defects. And the particle size of the iron powder raw material used for the Fe component was examined in detail.

  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, to obtain excellent weld metal mechanical performance even in high heat input welding, it is necessary to add a deoxidizer, an alloying agent, etc. in the bond flux to keep the oxygen content of the weld metal low and to improve the hardenability. is there. However, if a deoxidizer and an alloying agent are added excessively, the hardenability of the weld metal becomes excessive, the strength increases, and the toughness decreases. Therefore, as a result of examining various deoxidizers and alloying agents in order to develop bond fluxes corresponding to changes in welding heat input at various plate thicknesses, by adding appropriate amounts of Si and Mo, a good weld metal It has been found that the tensile strength and toughness of can be obtained.

  Next, the improvement in welding workability is the improvement of iron grain protrusions on the surface bead surface, which is currently considered the most important issue of single-sided submerged arc welding applied to large plate joints in shipbuilding. If iron grain protrusions occur on the front bead, a large amount of paint adheres to the iron grain protrusions in the shipbuilding coating process, and depending on the shape of the iron grain protrusions, it may be easy to peel off. Rust is easy to progress, and corrosion resistance is remarkably lowered. Therefore, the current shipyard removes the iron grain protrusions on the surface bead surface with a grinder, shot blasting, or the like, which raises a problem of cost increase due to a decrease in productivity.

  In order to improve the above problems, the chemical composition of bond flux was examined. The cause of the iron grain protrusion is the iron powder (Fe) added to the bond flux. The weld metal during welding and the iron powder added to the bond flux during the slag solidification process are in a semi-molten state. It melts on the metal surface and remains on the surface when it is not completely melted.

  Therefore, as a result of removing the iron powder in the bond flux, there was no iron grain protrusion on the front bead surface, but the back bead shape was unstable and welding defects such as poor penetration and undercut occurred. Since the welding efficiency is reduced by removing the, the productivity is remarkably reduced as the welding speed is reduced. From the above, it has been found that iron powder in the bond flux is an essential component and cannot be removed in order to obtain a stable back bead shape, penetration and high welding efficiency in high-speed single-side welding.

Therefore the results of investigations of the bonded flux chemical composition assuming bonded flux of iron powder added type, by optimizing _{TiO 2, SiO 2, MgO,} CaO, Al 2 O 3, the slag composition such as CaF ₂ We succeeded in reducing iron grain protrusions. However, only by optimizing these slag compositions, the iron grain protrusions could not be completely eliminated, and the slag composition was further examined.

As a result, it was found that when TiO ₂ is contained in the slag composition, the slag tends to stick to the bead surface and promotes the generation of iron grain protrusions. Therefore, in order not to contain TiO _2, we succeeded in significantly reducing iron grain protrusions by applying raw materials not containing TiO ₂ as much as possible.

However, TiO ₂ is an essential component for welding materials as a component for maintaining arc stability and bead smoothness. By removing TiO ₂ , iron grain protrusions decreased, but arc stability deteriorated. In addition, a tendency to disturb the bead shape was observed. In addition, TiO ₂ is an important nucleation site that generates Ti oxide and the like in the form of weld metal structure and generates fine crystal grain acicular ferrite effective in improving strength and toughness. Therefore, the removal of TiO ₂ eliminated the nucleation site for generating acicular ferrite, and the tendency for weld metal toughness to decrease was recognized.

In order to solve these problems, the slag composition was further examined by adding ZrO ₂ and metal Ti. ZrO ₂ is similar to TiO _{2 in} that it has the effect of improving arc stability and bead smoothness, and no slag sticking is observed, and the bead heel end is well adapted and slag peelability is good. It was recognized that

  Nucleation for generating acicular ferrite was made possible by adding a small amount of metal Ti, and it was found that weld metal toughness was improved.

  By optimizing the above flux chemical composition, the iron grain protrusions on the surface bead surface were greatly reduced, and it became possible to obtain excellent weld metal mechanical performance. In welding, the iron grain protrusion on the surface bead surface could not be completely eliminated.

  Therefore, the present inventors paid attention to the particle size of the iron powder raw material used for the Fe component of the bond flux as a further improvement of the iron particle protrusion, and by adjusting the particle size of the iron powder raw material, It was found that a good front bead shape and appearance can be obtained.

That is, the bond flux for multi-electrode single-sided submerged arc welding to which the present invention is applied is in mass%, SiO ₂ : 7 to 27%, MgO: 14 to 32%, CaO: _{3 to} 15%, Al ₂ O ₃ : 7 _{~19%, CaF 2: 4~11%} , ZrO 2: 0.5~5%, B 2 O 3: 0.1~3%, Fe: 10~35%, Si: 0.3~4%, Mo: 0.1% to 3%, Ti: contains 0.1% to 3%, others deoxidizing agent, CO _2, consisting of an alkali metal oxide and inevitable impurities. At this time, TiO ₂ may be 1.5% or less, and the average particle size of the iron powder raw material used for the Fe component may be 150 μm or less.

  The reason for limitation of the particle size constitution of the iron powder raw material used for the flux component composition and Fe component of the bond flux for multi-electrode single-sided submerged arc welding of the present invention will be described below. The content of each component is expressed by 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 is simply expressed as%.

SiO ₂ : 7 to 27%
SiO ₂ using silica sand, zircon sand, wollastonite, water glass (sodium silicate, potassium silicate), etc. as a raw material is an important component for forming a good weld bead. The amount increases and the toughness deteriorates. If the SiO ₂ content is less than 7%, the fit of the bead end becomes worse, the slag peelability is deteriorated, and undercutting occurs particularly in high-speed single-sided welding. On the other hand, if SiO ₂ exceeds 27%, the oxygen content of the weld metal increases and the toughness deteriorates. Therefore, the content of SiO ₂ is 7 to 27%.

MgO: 14-32%
MgO using magnesia clinker, magnesium carbonate or the like as a raw material has an effect of improving the slag fire resistance and basicity and reducing the oxygen content of the weld metal. If MgO is less than 14%, the basicity of the flux becomes low, the amount of oxygen in the weld metal increases, and the toughness deteriorates. On the other hand, if MgO exceeds 32%, 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 appearance become poor. Therefore, the content of MgO is 14 to 32%.

CaO: 3 to 15%
CaO using wollastonite, calcium carbonate or the like as a raw material is an important component for adjusting the melting point and fluidity of slag. If the CaO content is less than 3%, the bead collar will not fit well and the bead appearance will be poor, and undercut will also occur in high-speed single-sided welding. On the other hand, if CaO exceeds 15%, the slag fluidity becomes poor, the bead height is uneven, and the slag peelability becomes poor. Therefore, the CaO content is 3 to 15%.

Al ₂ O ₃ : 7 to 19%
Al ₂ O ₃ mainly composed of alumina is an extremely important component for obtaining good slag removability and bead appearance by high-speed single-side welding. It also has the effect of improving the arc stability. If Al ₂ O ₃ is less than 7%, the effect cannot be obtained. On the other hand, if Al ₂ O ₃ exceeds 19%, it becomes a convex bead and the slag peelability becomes poor. Therefore, the content of Al ₂ O ₃ is 7 to 19%.

CaF ₂ : 4 to 11%
CaF ₂ using fluorite as a raw material is effective in improving toughness, but since the melting point is low, if it is excessive, the smoothness of the beads is impaired. If CaF ₂ is less than 4%, there is no effect of improving toughness, and if it exceeds 11%, the bead appearance becomes poor. Therefore, the content of CaF ₂ is 4 to 11%.

ZrO ₂ : 0.5 to 5%
ZrO ₂ using zircon sand, zircon oxide, or the like as a raw material is an extremely important component for obtaining arc stability, good bead shape / appearance, and slag peelability by high-speed single-side welding. If ZrO ₂ is less than 0.5%, the effect cannot be obtained. On the other hand, if ZrO ₂ exceeds 5%, the oxygen content of the weld metal increases and the toughness deteriorates. Therefore, the ZrO ₂ content is set to 0.5 to 5%.

B ₂ O ₃ : 0.1 to 3%
B ₂ O ₃ made from boron oxide, borax or the like is effective in improving toughness. If B ₂ O ₃ is less than 0.1%, the effect of improving toughness cannot be obtained. If it exceeds 3%, the weld metal is hardened and the toughness is deteriorated. Therefore, the content of B ₂ O ₃ is 0.1 to 3%.

Fe: 10 to 35%
Fe using iron powder and iron alloys such as Fe-Si and Fe-Mn as raw materials is effective in improving welding efficiency and arc concentration. If Fe is less than 10%, the welding efficiency is lowered and the arc concentration is inferior, so that the bead shape of the back bead becomes unstable. On the other hand, if Fe exceeds 35%, iron grain protrusions are generated on the bead surface and the slag peelability becomes poor. Therefore, the Fe content is 10 to 35%.

The particle size of the iron powder raw material used for the Fe component: 150 μm or less The particle size of the iron powder raw material used for the Fe component is an important factor for completely eliminating the iron particle protrusions on the bead surface in high speed and continuous welding. It is. In order not to generate iron grain protrusions on the bead surface, it is necessary to make the iron powder melt into the molten metal at an early stage of welding, and it is improved to some extent by limiting the overall particle size of the flux to the optimum configuration However, it is preferable that the iron powder raw material to be applied has a finer particle size, and the average particle size is preferably 150 μm or less. However, in the present invention, it is not essential that the average particle size of the iron powder raw material is 150 μm or less, and even if it exceeds this, the desired effect is exhibited.

Si: 0.3 to 4%
Si using metal Si, Fe—Si, Fe—Si—Mn, or the like as a raw material is a deoxidizing element and reduces the oxygen content of the weld metal. If Si is less than 0.3%, the deoxidation effect cannot be obtained, and the toughness deteriorates. On the other hand, if Si exceeds 4%, the hardness of the weld metal becomes excessive and the toughness deteriorates. Therefore, Si is 0.3 to 4%.

Mo: 0.1 to 3%
Mo made of metal Mo and Fe—Mo is an important component as an element for increasing the hardenability of weld metal. If Mo is less than 0.1%, the strength of the weld metal is reduced and there is no effect in improving toughness. On the other hand, if Mo exceeds 3%, the hardenability of the weld metal becomes excessive and the hardness becomes excessive. Toughness deteriorates. Therefore, Mo is 0.1 to 3%.

Ti: 0.1 to 3%
Ti using metal Ti, Fe-Ti, etc. as a raw material is important to generate Ti oxides and the like in the weld metal microstructure, and to produce fine crystalline acicular ferrite effective in improving strength and toughness. It becomes a nucleation site. If Ti is less than 0.1%, acicular ferrite effective for improving toughness cannot be produced, and the toughness deteriorates. On the other hand, if Ti exceeds 3%, the hardness of the weld metal becomes excessive and the toughness deteriorates. Therefore, Ti is 0.1 to 3%.

TiO ₂ : 1.5% or less TiO ₂ is an effective component for maintaining arc stability and bead smoothness, but slag tends to stick to the bead surface and promotes the generation of iron grain protrusions. But there is. Therefore, the content of TiO ₂ as an impurity in each raw material is preferably as low as possible, and the content is desirably 1.5% or less. However, in the present invention, it is not essential that the content of TiO ₂ is 1.5% or less, and even if it exceeds this, the desired effect can be obtained.

Others include deoxidizers such as Mn and Al: 0.3% or less, CO ₂ from metal carbonates, alkali metal oxides such as K ₂ O and Na ₂ O from water glass: 4% or less and P, It is an unavoidable impurity such as S, and both P and S are preferably as low as possible because they produce a low melting point compound and reduce toughness.

Note that CO ₂ from metal carbonates such as calcium carbonate and magnesium carbonate is gasified by welding heat, and has a shielding effect in an arc atmosphere and an effect of stabilizing the arc. However, when CO ₂ becomes excessive, the arc becomes unstable and a pock mark is generated on the bead surface. Therefore, the CO ₂ from the metal carbonate is preferably 1 to 6%.

  Further, in the single-side welding using the bond flux for multi-electrode single-sided submerged arc welding according to the present invention, the wire diameter to be combined is 4 in order to perform welding that enables stable arc, wire feedability, and improved 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.

  Table 4 shows the bond flux adjusted for the average particle size of the iron powder raw material applied to the various flux components and Fe components shown in Table 1, the back flux of the chemical composition shown in Table 2, and the wire of the chemical composition shown in Table 3. A welded steel plate 4 having a thickness of 20 mm having the chemical composition shown is processed into a groove shape having a groove angle of 50 ° and a root face of 3 mm as shown in FIG. The FCuB single-sided submerged arc welding test shown in FIG. 1 was performed.

  In this FCuB single-sided submerged arc welding test, about 4 to 7 mm of back flux 2 having the composition shown in Table 2 is sprayed on the backing copper plate 1 and air is injected into the air hose 3. The groove is pressed against the groove back surface 4a corresponding to the back side. 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.

  The bond flux shown in Table 1 was granulated with water glass as a fixing agent, then baked at 400 to 550 ° C. for 2 hours, and sized to 12 × 100 mesh.

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

  Evaluation of each prototype bond flux is as follows: Arc stability during single-sided submerged arc welding with 3 or 4 electrodes, presence or absence of iron grain protrusions and slag sticking on the surface bead surface after welding, bead appearance / shape, slag peelability, under The presence or absence of cut was investigated, and the tensile strength, toughness and weld metal oxygen content of the weld metal were further investigated.

  The mechanical performance evaluation of the weld metal was performed using a Charpy impact test piece (JIS Z2242 V-notch test piece) and a tensile test piece (JIS Z2241 10) centering on the center of the steel plate thickness of the single-sided submerged arc welding test piece with three electrodes or four electrodes. No.) was collected and subjected to a mechanical test. The toughness was evaluated by a Charpy impact test at −20 ° C., and evaluated by the average of absorbed energy vE (J) of 3 repetitions. The absorbed energy in the Charpy impact test was 80 J or more. Evaluation of tensile strength made 490-690 MPa favorable. The results of these surveys are summarized in Table 6.

Flux symbols F1 to F10 in Tables 1 and 6 are examples of the present invention, and flux symbols F11 to F22 are comparative examples. The flux symbols F1 to F10 according to the present invention have appropriate flux components, so that there is no iron grain protrusion and slag sticking on the surface bead surface in both one-sided submerged arc welding with three electrodes or four electrodes, and welding workability is good. There was no defect in the welded part, and the mechanical performance of the weld metal was excellent, which was a very satisfactory result. In addition, the flux symbol F5 having a large amount of TiO ₂ and the flux symbol F10 having a large average particle diameter of the iron powder raw material did not cause iron grain protrusions and sticking on the surface bead surface.

  Since the flux symbol F11 in the comparative example has a large amount of MgO, the wavy surface of the bead surface becomes rough, and the slag peelability and the bead appearance deteriorate. Further, since the Fe content is small, the welding efficiency is lowered and the arc concentration is inferior, so that the bead shape of the back bead becomes unstable. Furthermore, since Mo is high, the tensile strength of the weld metal is high and the absorbed energy is low.

  Since the flux symbol F12 has a small amount of CaO, the bead appearance is poor and undercutting occurs. Moreover, since there is much Si, the tensile strength of a weld metal became high and the absorbed energy was a low value.

Flux code F13, since SiO ₂ is large, amount of oxygen in the weld metal is large and the absorbed energy were low. Further, since ZrO ₂ was small, the arc became unstable, and the bead shape, appearance, and slag peelability deteriorated. Furthermore, since the average particle diameter of the iron powder raw material was large, iron grain protrusions were generated on the surface beads, and slag was stuck.

Flux symbol F14 has a small amount of MgO, so the amount of oxygen in the weld metal is large and the absorbed energy is low. Further, the bead shape and the slag removability was poor because Al ₂ O ₃ is large. Further, since TiO ₂ is large sticking slag on the bead surface were also generated iron particle projection.

Since the flux symbol F15 is low in SiO ₂ , the slag peelability is poor and undercutting occurs. In addition, since the CaF ₂ is large, the bead shape was poor. Furthermore, since the B ₂ O ₃ is large, the tensile strength of the weld metal was high and the absorbed energy was low.

  Since the flux symbol F16 contains a large amount of CaO, the bead appearance and slag peelability were poor. Moreover, since there is much Ti, the tensile strength of a weld metal became high and the absorbed energy was a low value.

Since the flux symbol F17 has a small amount of Al ₂ O ₃ , the arc becomes unstable, and the slag peelability and the bead appearance are poor. Moreover, since Ti was not added, the absorbed energy of the weld metal was low.

Since the flux symbol F18 has a small amount of CaF ₂ , the absorbed energy of the weld metal was low. Moreover, since there was much Fe, the iron grain protrusion generate | occur | produced on the bead surface, slag stuck, and also slag peelability was unsatisfactory.

  In the flux symbol F19, since Mo is not added, the tensile strength of the weld metal is low and the absorbed energy is also low.

In the flux symbol F20, since B ₂ O ₃ was not added, the absorbed energy of the weld metal was low.

Since the flux symbol F21 has a large amount of ZrO ₂ , the amount of oxygen in the weld metal is large and the absorbed energy is low.

  Since the flux symbol F22 has a small amount of Si, the amount of oxygen in the weld metal is large and the absorbed energy is low.

1 Back copper plate 2 Back flux 3 Air hose 4 Steel plate to be welded 5 Wire 6 Front flux

Claims (3)

% By mass
SiO ₂ : 7 to 27%,
MgO: 14 to 32%,
CaO: 3 to 15%,
Al ₂ O ₃ : 7 to 19%,
CaF ₂ : 4 to 11%,
ZrO ₂ : 0.5 to 5%,
B ₂ O ₃ : 0.1 to 3%,
Fe: 10 to 35%,
Si: 0.3 to 4%
Mo: 0.1 to 3%,
Ti: 0.1 to 3%
The other is composed of a deoxidizer, CO ₂ , an alkali metal oxide and inevitable impurities, and a bond flux for multi-electrode single-sided submerged arc welding. % By mass
The bond flux for multi-electrode single-sided submerged arc welding according to claim 1, wherein TiO _{2 is} 1.5% or less.   3. The bond flux for multi-electrode single-sided submerged arc welding according to claim 1, wherein an average particle diameter of the iron powder raw material used for the Fe component is 150 μm or less.

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