JP7039374B2 - Shielded metal arc welding rod for low hydrogen fillet welding - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention has excellent pit resistance, a small amount of fume generation, good welding workability such as a good bead shape, and excellent mechanical properties of the weld metal in fillet welding of prime-coated steel plates. The present invention relates to a shielded metal arc welding rod for low hydrogen fillet welding, which is also excellent in productivity.

In recent years, thick steel plates of 490 MPag class high-strength steel have been used due to the increase in size of welded structures such as buildings, bridges and ships, but they have been used for a long time in harsh environments such as air or marine areas. A prime-coated steel sheet in which the surface of the steel sheet is coated with a primer for the purpose of rust prevention is widely used.

In the welding of welded structures using such thick prima-coated steel plates, it is possible to weld complex structures, the welding efficiency is high, and the large diameter is low in gravity welding, which can ensure the mechanical properties of the welded part. Shielded metal arc welding rods for hydrogen-based fillet welding are often used. However, in the case of fillet welding of a primer-coated steel sheet, there is a problem that the primer coated on the surface of the steel sheet is vaporized at the time of welding, pits are likely to occur frequently, and welding workability is deteriorated due to a large amount of fume generation. be.

In addition, the shielded metal arc welding rod for low hydrogen fillet welding in gravity welding has a larger outer diameter than the normal shielded metal arc welding rod in order to secure the welding amount in 1-pass welding. Since it is long, there is also a problem that productivity deteriorates, such as coating cracking easily occurring during production.

Under such circumstances, gravity welding has excellent pit resistance, good welding workability such as a small amount of fume generation, excellent mechanical properties of the welded part, and excellent productivity. Conventionally, a shielded metal arc welding rod for fillet welding has been proposed.

For example, Patent Document 1 defines the ratio of the contents of TiO ₂ , SiO ₂ , MgCO ₃ , and MnCO ₃ in the coating agent to improve welding workability such as pit resistance by low hydrogen-based shielded metal arc welding. The stick is disclosed. According to the low hydrogen-based shielded metal arc welding rod described in Patent Document 1, the pit resistance in welding of a normal primer-coated steel sheet can be improved. However, when the wash primer coated steel sheet is welded, there is a problem that sufficient pit resistance cannot be obtained. Further, the technique described in Patent Document 1 cannot obtain good welding workability such as reduction of the amount of fume generated. Further, the technique described in Patent Document 1 has a problem that coating cracks occur during production.

Further, in Patent Document 2 and Patent Document 3, by adding an appropriate amount of an alloy iron containing graphite, activated carbon or carbon and a nitrogen compound to the coating material, bubbling is generated in the molten pool due to gas release during welding to withstand bubbling. A shielded metal arc welding rod that can improve pitting properties is disclosed. According to the shielded metal arc welding rods described in Patent Documents 2 and 3, although the pit resistance in the welding of a normal primed coated steel sheet can be improved, the wash primed coated steel sheet is welded as in Patent Document 1. In some cases, sufficient pit resistance cannot be obtained, and good welding workability cannot be obtained due to an increase in the amount of fume generated. In addition, good productivity cannot be obtained due to cracks in the coating during production.

Further, in Patent Document 4, by adding an appropriate amount of metal fluoride, MgO, TiO ₂ , SiO ₂ , and tetrasilicon fluoride mica to the coating material, the fluidity of slag is improved and welding workability, particularly fume generation, is generated. A low hydrogen-based shielded metal arc welding rod that can improve pit resistance by reducing the amount and adding an appropriate amount of one or more of metal carbonate and Ti, Al, Mg, Si, and SiC is disclosed. According to the low hydrogen-based shielded metal arc welding rod described in Patent Document 4, the pit resistance is improved while reducing the amount of fume generated by welding a normal primer-coated steel sheet, which is also the same as in Patent Document 1. Sufficient pit resistance cannot be obtained when welding wash-primer coated steel sheets. In addition, there is a problem that good productivity cannot be obtained, such as coating cracking during production.

Japanese Unexamined Patent Publication No. 60-196293 Japanese Unexamined Patent Publication No. 55-40064 Japanese Unexamined Patent Publication No. 60-837998 Japanese Unexamined Patent Publication No. 59-110495

Therefore, the present invention has been devised in view of the above-mentioned problems, and while ensuring excellent pit resistance in fillet welding of prime-coated steel sheets with a shielded metal arc welding rod for low hydrogen fillet welding. Welding workability is excellent, such as a small amount of fume generation and a good bead shape, and excellent mechanical properties of weld metal can be obtained, and coating cracks do not occur during production, resulting in good productivity. It is an object of the present invention to provide a shielded metal arc welding rod for low hydrogen fillet welding.

The gist of the present invention is that in a coated arc welding rod for low hydrogen fillet welding in which a coating agent is applied to a steel core wire, the coating agent is 1 by mass% of the total mass of the coating material and is one of metal carbonates. Total of seeds or 2 or more species: 5 to 15%, Total of 2 or more species of metal fluoride: 3 to 8%, NaF in the metal fluoride: 0.2 to 1.5%, Tio of Ti oxide Total of ₂ conversion values: 8 to 18%, total of SiO ₂ conversion values of Si oxide: 10 to 20%, total of Al ₂ O ₃ conversion values of Al oxide: 1.5 to 4.0%, Fe Total FeO conversion value of oxide: 0.5 to 2.0%, MgO: more than 6% to 10%, Si: 0.5 to 2.0%, Mn: 5 to 10%, Ni: 0.3 ~ 2.0%, iron powder: 25 ~ 45%, total of Na ₂ O conversion value and K ₂ O conversion value of Na oxide and K oxide: 2 ~ 6%, the rest is coating agent, iron It is a coated arc welding rod for low hydrogen fillet welding, which is characterized by having Fe content from an alloy and unavoidable impurities.

According to the shielded metal arc welding rod for low hydrogen fillet welding of the present invention, excellent pit resistance is ensured in fillet welding of prime-coated steel sheets, the amount of fume generated is small, and a good bead shape can be obtained. Since the welding workability is good, the excellent mechanical properties of the weld metal can be obtained, and the productivity is also excellent, the efficiency and quality of welding can be improved.

In order to solve the above-mentioned problems, the present inventors have studied various causes of poor pit resistance in fillet welding of primer-coated steel sheets.

In fillet welding of prime-coated steel sheets, the prima coated on the surface of the steel sheet vaporizes during welding to generate gas and form pits. A method is known in which a large amount of salt is contained to intensify the spraying of an arc to stir the inside of the molten pool to forcibly release the gas remaining in the molten pool to improve the pit resistance. However, in gravity welding, the core wire diameter and the outer diameter of the shielded metal arc welding rod are large for the purpose of ensuring the welding amount in one-pass welding, and the concentration of the arc is deteriorated and the spraying of the arc is weakened. In particular, when a wash primer-coated steel plate, which is prone to pits, is fillet welded, it was found that the inside of the molten pool could not be sufficiently agitated and good pit resistance could not be obtained.

Therefore, as a result of various trial trials and studies on the coating material components of the shielded metal arc welding rod for low hydrogen fillet welding in order to improve the arc spraying in gravity welding, NaF and metal carbonate were added in appropriate amounts to the coating material. By doing so, it was found that strong arc spraying was ensured and good pit resistance could be obtained even by fillet welding of wash prime coated steel sheets.

Next, as a result of studies to improve other welding workability, regarding the stabilization of the arc and the reduction of the amount of spatter generated, Na oxide and K oxide, Ti oxide, Al oxide, and iron were added to the coating material. By adding an appropriate amount of powder, the arc can be stabilized and the amount of spatter generated can be reduced, and by further specifying the total content of Na oxide and K oxide and the total amount of metal fluoride, the amount of fume generated. Was found to be able to be reduced.

Regarding the slag encapsulation property, by adding an appropriate amount of Ti oxide and Si oxide to the coating agent, an appropriate amount of slag that can completely enclose the molten pool is generated, and an appropriate amount of metal fluoride and Fe oxide are added. It has been found that by adding the slag, the fluidity of the molten slag can be made appropriate and the slag can be uniformly encapsulated on the bead surface to improve the slag encapsulation property and improve the bead shape.

Furthermore, it has been found that by adding an appropriate amount of Si oxide and MgO, the slag peelability is improved and an excellent bead shape can be obtained.

Regarding the mechanical properties of the weld metal, by adding an appropriate amount of metal carbonate to the coating agent, CO ₂ gas is generated during welding to shield the molten pool and improve the toughness of the weld metal, and deoxidation. It has been found that the strength and toughness of the weld metal can be improved by adding an appropriate amount of effective Si and Mn as well as an appropriate amount of Ni.

In terms of productivity, shielded metal arc welding rods are made by adding water glass to the raw material, applying a kneaded coating agent around the core wire, and then drying it to make a product. Since the core wire of the shielded metal arc welding rod has a larger diameter than that of a normal one, the wall thickness of the coating agent to be applied becomes large, and defects such as coating cracks are likely to occur during drying. Therefore, in the present invention, it has been found that by limiting the amount of Na oxide and K oxide added to the water glass in the coating agent, defects such as coating cracks during drying can be prevented and productivity can be improved.

Hereinafter, the component composition of the coating agent for the shielded metal arc welding rod for low hydrogen fillet welding of the present invention and the reason for limiting the component composition will be described in detail. The content of each component composition shall be expressed in mass% with respect to the total mass of the coating agent, and when expressing the mass%, it shall be simply described as%.

[Total of one or more metal carbonates: 5-15%]
Metallic carbonate is added from MgCO ₃ , CaCO ₃ , BaCO ₃ , MnCO ₃ , etc. and decomposes in an arc to generate CO ₂ gas, which protects the molten pool and molten slag from the atmosphere and enhances the toughness of the weld metal. In addition to ensuring, it has the effect of strengthening the spraying of arcs and preventing the occurrence of pits. If the total of one or more of the metal carbonates is less than 5%, the shielding effect is insufficient, the toughness of the weld metal is lowered, and the arc spraying is weakened, so that pits are likely to occur. On the other hand, if the total of one or more of the metal carbonates exceeds 15%, the arc spraying becomes too strong and the amount of spatter generated increases. Therefore, the total of one or more metal carbonates is 5 to 15%.

[Total of 2 or more types of metal fluoride: 3-8%]
Metal fluoride is added in two or more kinds from CaF ₂ , MgF ₂ , BaF ₂ , AlF ₃ , Na ₃ AlF ₆ , NaF, LiF, etc., and has the effect of adjusting the fluidity of molten slag to improve the bead shape. There is. When the total of two or more kinds of metal fluoride is less than 3%, the fluidity of the molten slag is poor and the bead shape becomes convex. On the other hand, when the total of two or more kinds of metal fluoride exceeds 8%, the fluidity of the molten slag becomes remarkably high, the lower leg side of the bead becomes a bulging shape, and the amount of fume generated also increases. Therefore, the total of two or more kinds of metal fluorides is 3 to 8%.

[NaF in metal fluoride: 0.2-1.5%]
NaF in the metal fluoride has a high effect of strengthening the spraying of the arc, and can prevent the generation of pits even in the fillet welding of the wash primer coated steel sheet. If the NaF in the metal fluoride is less than 0.2%, sufficient arc spraying cannot be obtained, and the formation of pits cannot be prevented by fillet welding of the wash primer coated steel sheet. On the other hand, when NaF in the metal fluoride exceeds 1.5%, the spraying of the arc becomes too strong and the amount of spatter generated increases. Therefore, NaF in the metal fluoride is 0.2 to 1.5%.

[Total TIO ₂ conversion value of Ti oxide: 8-18%]
Ti oxide is added from rutile, titanium oxide, sodium titanate, titanium slag, illuminate, etc., acts as an arc stabilizer and slag generator, stabilizes the arc, reduces the amount of spatter generated, and slag encapsulation. It has the effect of improving the properties and bead shape. If the total TiO ₂ conversion value of the Ti oxide is less than 8%, the arc becomes unstable and the amount of spatter generated increases. If the total TiO ₂ conversion value of the Ti oxide is less than 8%, the amount of slag is insufficient, the slag encapsulation property is deteriorated, and the bead shape becomes poor. On the other hand, when the total of the TIO ₂ conversion values of the Ti oxide exceeds 18%, the amount of slag becomes excessive, the slag encapsulation state becomes uneven, and the bead shape becomes poor. Therefore, the total TiO ₂ conversion value of Ti oxide is set to 8 to 18%.

[Total SiO ₂ conversion value of Si oxide: 10 to 20%]
Si oxide is added from silica sand, feldspar, water glass, etc., and has the effect of improving the slag exfoliation property and improving the bead shape. If the total SiO ₂ conversion value of the Si oxide is less than 10%, the slag peelability and the bead shape will be poor. On the other hand, when the total SiO ₂ conversion value of the Si oxide exceeds 20%, the viscosity of the slag becomes high, the slag cannot uniformly cover the bead surface, and the bead shape becomes poor. Further, when the total SiO ₂ conversion value of the Si oxide exceeds 20%, the gas in the molten pool is less likely to be released, and pits are likely to occur. Therefore, the total value of Si oxide converted to SiO ₂ is 10 to 20%.

[Total Al ₂ O ₃ conversion value of Al oxide: 1.5 to 4.0%]
Al oxide is added from alumina, feldspar, etc., and has the effect of adjusting the viscosity of molten slag and improving the slag exfoliation property. If the total Al ₂ O ₃ conversion value of the Al oxide is less than 1.5%, the slag peelability is poor, the viscosity of the molten slag is low, and the bead shape is poor. On the other hand, when the total Al ₂ O ₃ conversion value of the Al oxide exceeds 4.0%, the slag becomes glassy and the slag peelability is poor, the viscosity of the molten slag is high, and the bead shape is poor. Therefore, the total Al ₂ O ₃ conversion value of Al oxide is 1.5 to 4.0%.

[Total FeO conversion value of Fe oxide: 0.5 to 2.0%]
Fe oxide is added from FeO, Fe ₂ O ₃ and the like, and has the effect of adjusting the fluidity of the molten slag to improve the slag encapsulation property and improve the bead shape. If the total FeO conversion value of the Fe oxide is less than 0.5%, the fluidity of the molten slag becomes poor, the slag encapsulation property becomes poor, and the bead shape becomes poor. On the other hand, when the total FeO conversion value of Fe oxide exceeds 2.0%, the amount of slag becomes excessive, the slag encapsulation state becomes uneven, and the bead shape becomes poor. Therefore, the total FeO conversion value of Fe oxide is set to 0.5 to 2.0%.

[MgO: Over 6% to 10%]
MgO is added from magnesia clinker and the like, and has an effect of improving slag peelability and bead shape. If the MgO content is 6% or less, the effect cannot be obtained, and the slag peelability and the bead shape become poor. On the other hand, when MgO exceeds 10%, the amount of slag becomes excessive, the slag encapsulation state becomes uneven, and the bead shape becomes poor. Therefore, MgO is set to more than 6% to 10%.

[Si: 0.5-2.0%]
Si is added from alloy powders such as metallic Si, Fe—Si, and Fe—Si—Mn and acts as a deoxidizing agent to improve the toughness of the weld metal and prevent the generation of pits. If Si is less than 0.5%, deoxidation is insufficient, the toughness of the weld metal is lowered, and pits are likely to occur. On the other hand, when Si exceeds 2.0%, a low melting point oxide is deposited at the grain boundaries of the weld metal and the toughness is lowered. Therefore, Si is set to 0.5 to 2.0%.

[Mn: 5-10%]
Mn is added from alloy powders such as metal Mn, Fe-Mn, and Fe-Si-Mn and acts as a deoxidizing agent to improve the strength and toughness of the weld metal and prevent the formation of pits. be. If Mn is less than 5%, deoxidation is insufficient, the strength and toughness of the weld metal are lowered, and pits are likely to occur. On the other hand, when Mn exceeds 10%, the strength of the weld metal increases and the toughness decreases. Therefore, Mn is set to 5 to 10%.

[Ni: 0.3-2.0%]
Ni is added from alloy powders such as metallic Ni and Fe—Ni, and has the effect of improving the strength and toughness of the weld metal. If Ni is less than 0.3%, the required strength and toughness of the weld metal cannot be obtained. On the other hand, when Ni exceeds 2.0%, the strength of the weld metal increases and the toughness decreases. Therefore, Ni is set to 0.3 to 2.0%.

[Iron powder: 25-45%]
Iron powder has the effect of softening the arc state. If the iron powder is less than 25%, the arc becomes unstable and the amount of spatter generated increases. On the other hand, when the iron powder exceeds 45%, the spraying of the arc becomes weak and pits are likely to occur. Therefore, the iron powder is 25 to 45%.

[Total of Na ₂ O conversion value and K ₂ O conversion value of Na oxide and K oxide: 2 to 6%]
Na oxide and K oxide are added from sodium silicate and potassium silicate, potassium feldspar, potassium glass, soda feldspar and the like in water glass, and have an effect of stabilizing an arc and reducing the amount of spatter generated. Further, Na oxide and K oxide also have an effect of adjusting the viscosity of the coating agent to prevent coating cracking during drying and improving productivity when producing a shielded metal arc welding rod. If the total of the Na ₂ O conversion value and the K ₂ O conversion value of Na oxide and K oxide is less than 2%, coating cracks are likely to occur during production. In addition, the arc becomes unstable and the amount of spatter generated increases. On the other hand, when the total of the Na ₂ O conversion value and the K ₂ O conversion value of Na oxide and K oxide exceeds 6%, the arc spraying becomes too strong, the amount of spatter generated increases, and the amount of fume generated increases. Will also increase. Therefore, the total of the Na ₂ O conversion value and the K ₂ O conversion value of Na oxide and K oxide is 2 to 6%.

In addition to the above components, the balance in the coating agent of the shielded metal arc welding rod for low hydrogen fillet welding of the present invention contains 0.1 to 3% of a coating agent such as sodium alginate and cellulose from the viewpoint of productivity. , Fe—Si, Fe—Mn, Fe—Si—Mn and other iron alloys with Fe content and unavoidable impurities. Further, it is preferable to use JIS G 3523 SWY11 as the steel core wire to be used. Further, the coverage of the coating agent on the steel core wire is preferably 35 to 55%.

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

Various coating agents shown in Table 1 are applied to the steel core wire of JIS G 3523 SWY11 having a diameter of 6.4 mm and a length of 700 mm at a coverage of 40 to 47%, and then fired at 400 ° C. to produce various prototype welding rods. The properties, welding workability and mechanical properties were investigated.

For the productivity evaluation, 500 kg of various prototype welding rods were produced, the presence or absence of defects such as coating cracks was visually confirmed, and those having a good coating appearance and no defects were considered to be good.

For the evaluation of welding workability, various prototype welding rods were used, and a primer-coated steel plate with a thickness of 12 mm x width 100 mm x length 1000 mm coated with a wash primer with a thickness of 25 to 35 μm was applied to a T-shape using JIS G 3106 SM490A. Horizontal fillet welding with a welding current of 300 A is performed by gravity welding using a T-shaped test piece assembled in a mold, and the quality of the arc state, spatter generation amount and fume generation amount, slag encapsulation, and slag are performed. The peelability and the quality of the bead shape were visually investigated. The pit resistance was good when no pits were generated in the entire length of the weld bead.

For the evaluation of mechanical properties, a welded metal test was performed with an AC welder according to JIS Z 3111 using a steel plate with a thickness of 20 mm of JIS G 3106 SM490A, and a tensile test piece (A1) and an impact test piece (V notch). The test piece) was collected and subjected to a tensile test and an impact test. In the tensile test, the tensile strength was 490 to 590 MPa, and in the impact test, the average value of the absorbed energy three times was repeated at a test temperature of −20 ° C. and the average value was 47 J or more. The results of these surveys are summarized in Table 2.

No. in Tables 1 and 2 1 to No. No. 12 is an example of the present invention. 13-No. 24 is a comparative example. No. 1 of the present invention. 1 to No. 12 is the total of metal carbonates in the coating agent, the total of two or more kinds of metal fluorides, the total of NaF in metal fluorides, the total of TiO ₂ conversion values of Ti oxides, and the total of SiO ₂ conversion values of Si oxides. Total, Al ₂ O ₃ conversion value of Al oxide, FeO conversion value of Fe oxide, Na ₂ O conversion value of MgO, Si, Mn, Ni, iron powder, Na oxide and K oxide and Since the total of the K ₂ O conversion values was appropriate, there were no defects such as coating cracks during the production of the coated arc welding rod, and the productivity was good. In addition, the arc state in horizontal fillet welding with wash primer coated steel sheet is good, the amount of spatter generation and fume generation is small, the slag encapsulation property, slag peelability and bead shape are good, and pits do not occur. rice field. Furthermore, the tensile strength and absorption energy of the weld metal were also appropriate, and the results were extremely satisfactory.

No. in the comparative example. In No. 13, since the amount of NaF in the metal fluoride was small, the arc was weakly sprayed and pits were generated. In addition, since the total of Al ₂ O ₃ conversion values of Al oxide was small, the slag peelability was poor and the bead shape was also poor.

No. In No. 14, since the total FeO conversion value of Fe oxide was small, the slag encapsulation property was poor and the bead shape was poor. Further, since the total of the Na ₂ O conversion value and the K ₂ O conversion value of the Na oxide and the K oxide was large, the arc spraying became too strong, the amount of spatter generated was large, and the amount of fume generated was also large.

No. In No. 15, since the total of the TiO ₂ conversion values of the Ti oxide was small, the arc was unstable and the amount of spatter generated was large. In addition, the slag encapsulation was poor and the bead shape was poor. Furthermore, since the amount of Ni was small, the tensile strength and absorption energy of the weld metal were low.

No. In No. 16, since the total of Al ₂ O ₃ conversion values of Al oxide was large, the slag peelability was poor and the bead shape was also poor. In addition, since the amount of iron powder was small, the arc was unstable and the amount of spatter generated was large.

No. In No. 17, since the amount of MgO was small, the slag peelability was poor and the bead shape was also poor. Moreover, since the amount of Ni was high, the tensile strength of the weld metal was high and the absorption energy was low. Furthermore, since there was a lot of iron powder, the arc was weakly sprayed and pits were generated.

No. In No. 18, since the total amount of metal carbonate was large, the arc was sprayed too strongly and the amount of spatter generated was large. In addition, since the total value of Si oxide in terms of SiO ₂ is large, the slag encapsulation property is poor, the bead shape is poor, and pits are also generated.

No. In No. 19, since the total amount of metal carbonate was small, the arc was weakly sprayed and pits were generated. In addition, the absorbed energy of the weld metal was low. Further, since a large amount of MgO was present, the slag encapsulation property was poor and the bead shape was poor.

No. In No. 20, since the total of two or more kinds of metal fluorides is small, the bead shape is convex. In addition, since the amount of Si was small, pits were generated and the absorption energy of the weld metal was low. Further, since the total of the Na ₂ O conversion value and the K ₂ O conversion value of Na oxide and K oxide is small, coating cracks occurred on the coating surface during production. In addition, the arc spraying was weak and unstable, and the amount of spatter generated was large.

No. In No. 21, since the total of two or more kinds of metal fluorides was large, the bead shape was poor and the amount of fume generated was large. Moreover, since the amount of Si was large, the absorption energy of the weld metal was low.

No. In No. 22, since the total of the TIO ₂ conversion values of the Ti oxide was large, the amount of slag was excessive and the slag encapsulation property and the bead shape were poor. Further, since the amount of Mn was large, the tensile strength of the weld metal was high and the absorption energy was low.

No. In No. 23, since the total value of Si oxides converted to SiO ₂ was small, the slag peelability was poor and the bead shape was also poor. Further, since Mn was small, pits were generated, and the tensile strength and absorption energy of the weld metal were low.

No. In No. 24, since the amount of NaF in the metal fluoride was large, the arc was sprayed too strongly and the amount of spatter generated was large. Further, since the FeO conversion value of Fe oxide is large, the slag encapsulation property is poor and the bead shape is poor.

Claims (1)

In a shielded metal arc welding rod for low hydrogen fillet welding in which a coating agent is applied to the steel core wire.
The coating agent is a mass% based on the total mass of the coating agent.
Total of one or more metal carbonates: 5-15%,
Total of 2 or more types of metal fluoride: 3-8%,
NaF in the metal fluoride: 0.2-1.5%,
Total of TIO ₂ conversion values of Ti oxide: 8-18%,
Total SiO ₂ conversion value of Si oxide: 10 to 20%,
Total Al ₂ O ₃ conversion value of Al oxide: 1.5-4.0%,
Total FeO conversion value of Fe oxide: 0.5-2.0%,
MgO: Over 6% to 10%,
Si: 0.5-2.0%,
Mn: 5-10%,
Ni: 0.3-2.0%,
Iron powder: 25-45%,
Total of Na ₂ O conversion value and K ₂ O conversion value of Na oxide and K oxide: 2 to 6% is contained.
The balance is a shielded metal arc welding rod for low hydrogen fillet welding, which is composed of a coating agent, Fe content from an iron alloy, and unavoidable impurities.