KR100764301B1 - Solid wires for gas-shielded arc welding and gas-shielded arc welding method using the same - Google Patents

Abstract

The present invention is 0.03 to 0.15% by mass of carbon (C) based on the total mass of the wire; Silicon (Si) 0.50-1.50 mass%; 1.00-3.00 mass% of manganese (Mn); Sulfur (S) from 0.020 to 0.150 mass%; And 0.01 to 0.20% by mass of titanium (Ti), 0.01 to 0.20% by mass of zirconium (Zr), 0.01 to 0.05% by mass of lanthanum (La), and 0.01 to 0.05% by mass of cerium (Ce). And the balance provides a solid wire for gas shield arc welding, which is iron and inevitable impurities. The solid wire can stably form beads even at high speed welding of 1.0 m / min or more, and can produce weld joints having low high temperature crackability and excellent fatigue strength, tensile strength and toughness in welding steel sheets having a thickness of 0.6 to 10 mm. Can be.

Description

Solid wire for gas shield arc welding and gas shield arc welding method using the same {SOLID WIRES FOR GAS-SHIELDED ARC WELDING AND GAS-SHIELDED ARC WELDING METHOD USING THE SAME}

1 illustrates the weld tip of a wrap-fillet weld joint.

FIG. 2A is a cross-sectional view showing where the specimen is sampled, and FIG. 2B is a plan view showing a method of preparing the specimen in a fishbone crack test.

The present invention relates to solid wire for gas shielded arc welding of 0.6-10 mm thick mild steel sheets and high tensile steel sheets, for example automotive steel sheets.

Structures welded by gas shield arc welding should be of high quality and their manufacturing method should provide more thorough labor savings and high efficiency. In the automotive industry, for example, full automation of welding using welding robots is promoted, and welding in current commercial manufacturing lines is carried out at a speed of about 1.0 m / min. There is a demand for welding with higher efficiency at higher speeds.

The steel plate structures have significant technical opportunities to meet global environmental issues. Among them, the demand for gauge reduction (dimension reduction) using high tensile steel sheet is urgent in the automobile industry for improving fuel efficiency through weight reduction. However, the fabricated welds do not exhibit the inherent fatigue strength of high tensile steel sheet materials because the fatigue strength of the welded spot does not increase compared to the ordinary base metal, but is equivalent to that of ordinary mild steel, while the load stress to the welded spot increases. Do not.

Welding at high speeds, in excess of 1.3 m / min, to further improve welding efficiency using conventional fill metal materials tends to produce irregular beads such as undercut beads and humping beads. have. In addition, the root opening of lap-fillet welds often fluctuates due to variations in the press accuracy of the work, and when high speed welding is performed with a root spacing greater than 1.9 mm, welding defects such as burn through and perforation may occur. Thus, there has been a strong demand for welding materials that can produce beads even in high speed welding stably and obtain wide beads that can be crosslinked over the root gap.

Conventional solid wires for gas shield arc welding of steel sheets with a thickness of 6 mm or less can be found in Japanese Patent Application Laid-Open No. 199-305476. This solid wire is used to improve welding workability and welding quality when welding a 6 mm thick thin plate at a speed of 1.0 m / min or higher. The carbon (C) is 0.02 to 0.10% by mass and the silicon (Si) is 0.8 to 1.2% by mass. %, Manganese (Mn) 1.0-1.8 mass%, phosphorus (P) 0.020 mass% or less, sulfur (S) 0.020-0.100 mass%, aluminum (Al) 0.005 mass% or less, oxygen (O) 0.0070 mass% or less, and It contains 0.00790 mass% or less of nitrogen (N), and remainder is iron (Fe) and an unavoidable impurity, where the ratio (Mn / Si) of Mn to Si is 1.2 to 1.8. This technique is intended to improve bead formation in high speed welding by adding a large amount of sulfur to adjust the surface tension of the molten metal.

High speed welding of the steel sheet as a base material using conventional welding materials often results in convex beads, even if not irregular beads. Such convex beads often reduce fatigue strength due to stress concentrations in the protrusions of the weld. As a result, welding should be carried out at lower welding speeds than in conventional techniques. Accordingly, there has been a need to provide a welding material that can provide a weld structure with high fatigue strength for a broader application of high tensile steel sheets in these structures and which can maintain satisfactory welding efficiency.

Welding materials capable of imparting compressive stress to the weld point have been commonly used to improve the fatigue strength of the joint. Specifically, the residual stress is reduced by lowering the martensite strain initiation temperature (hereinafter referred to as "Ms point"), making it possible to use strain expansion at low temperatures. For example, Japanese Laid-Open Patent Publication No. 1999-138290 discloses a welding material having a controlled Ms point of 250 to 170 ° C, typically using those having a predetermined composition in C, Cr, Ni, Si, Mn, Mo, and Nb contents. Is proposed.

However, the prior art has the following disadvantages. Sulfur (S) added to the solid wire described in Japanese Patent Laid-Open No. 193-305476 is an element that greatly changes the interfacial tension and fluidity of molten metal and can realize high speed welding at a specific amount. However, sulfur promotes hot cracking. This tendency (hot crack promotion) is evident in weld metals using filler metal materials compounded with sulfur of at least 0.02%. In particular, hot cracking occurs very often at varying root intervals greater than 1.0 mm when welding is performed at high speeds of 1.0 m / min or more.

Sulfur not only results in hot cracking but also reduces the strength and toughness of the material because the sulfide thickens as the amount of sulfur increases. Sulfurized free machined steel materials, ie machined steels according to Japanese Industrial Standard (JIS) G 4804 have improved machinability by containing a large amount of sulfur (SUM 24L, containing 0.26 to 0.35% by mass of sulfur). However, in weld metals that generally require some level of strength, toughness, and other mechanical properties, sulfur content is minimized to 0.03% or less because sulfur is very detrimental to these properties. Therefore, the solid wire described in Japanese Patent Laid-Open No. 193-305476 shows much higher hot-crack susceptibility and lower strength and toughness than ordinary wire.

The welding material described in Japanese Patent Laid-Open No. 1999-183890 contains a large amount of expensive alloying elements such as Cr and Ni, shows poor pullability when used as a solid wire, and is a very expensive (high cost) welding material. The welding material has poor applicability to the high speed welding required for the welding of steel sheets, because the welding metal has high viscosity. In addition, there is resistance to droplet movement, which causes spatter (welding slag). Thus, these materials have poor applicability to actual welding lines.

In this situation, it is an object of the present invention to stably form beads even at high speed welding of 1.0 m / min or more in the welding of steel sheets having a thickness of 0.6 to 10 mm, and have low hot cracking properties, fatigue strength, tensile strength and toughness. It is to provide a solid wire for gas shielded arc welding that can yield this excellent weld joint.

Specifically, in the first embodiment, the present invention is based on the total mass of the wire, 0.03 to 0.15 mass% of carbon (C); Silicon (Si) 0.50-1.50 mass%; 1.00-3.00 mass% of manganese (Mn); Sulfur (S) from 0.020 to 0.150 mass%; And 0.01 to 0.20% by mass of titanium (Ti), 0.01 to 0.20% by mass of zirconium (Zr), 0.01 to 0.05% by mass of lanthanum (La), and 0.01 to 0.05% by mass of cerium (Ce). And, the remainder is iron and unavoidable impurities, the content of phosphorus (P) as an unavoidable impurity is 0.025% by mass or less, to provide a solid wire for gas shielded arc welding with an A value of 100 or more determined according to the following equation (1) do:

In the above formula, [Mn], [Ti], [Zr], [La], [Ce] and [S] represent Mn, Ti, Zr, La, Ce and S contents (mass%) of the wire, respectively.

The solid wire according to the invention has a specific sulfur (S) content of 0.020 to 0.150% by mass, based on the total weight of the wire, thereby allowing the molten metal to flow less backwards and more in the width direction. In addition, the solid wire has a manganese (Mn) content of 1.00 to 3.00% by mass. This causes crystallization of MnS, which increases the eutectic temperature of the solid wire and reduces the high temperature crackability. In addition, the solid wire contains an appropriate amount of at least one element selected from the group consisting of Ti, Zr, La, and Ce, which tend to form sulfides. This results in the formation of sulfides containing these elements and having a high melting point so that sulfur is dispersed in the matrix phase. This prevents the formation of sulfides at grain boundaries. In addition, in the solid wire, the A value determined according to Equation 1 is set to 100 or more, whereby beads are stably formed in high-speed welding, a high temperature cracking property is reduced, and a weld joint having excellent fatigue strength of the high tensile steel sheet is formed. It can also be obtained by welding.

The solid wire may have a manganese (Mn) content of at least 1.50 mass%. This can greatly reduce hot cracking.

In addition, the solid wire may have a sulfur (S) content of 0.040% by mass or more. This allows beads to be formed more stably in high speed welding and improves fatigue strength.

Moreover, in 2nd embodiment, this invention is 0.02-0.15 mass% of carbon (C) on the basis of the total mass of a wire; Silicon (Si) 0.50-1.50 mass%; 1.00-3.00 mass% of manganese (Mn); Sulfur (S) from 0.020 to 0.150 mass%; 0.005 to 0.5 mass% of niobium (Nb); And 0.005 to 0.5 mass% of vanadium (V), 0.010 to 0.5 mass% of aluminum (Al), 0.005 to 0.5 mass% of chromium (Cr), 0.005 to 0.5 mass% of nickel (Ni) and 0.0010 to 0.0100 mass of boron (B). Contains%; The balance is iron and unavoidable impurities, and provides a solid wire for gas shielded arc welding in which the content of phosphorus (P) as an unavoidable impurity is 0.025% by mass or less.

Since the solid wire according to the present invention has been properly adjusted in the content of sulfur and other alloying elements, it is possible to stably form beads even in high-speed welding in the welding of high strength steel sheets, and has reduced high temperature cracking properties and has fatigue strength, tensile strength and toughness. This excellent weld joint can be manufactured.

Furthermore, the present invention provides a method of performing gas shield arc welding, in a third embodiment, comprising welding a high strength steel sheet having a thickness of 0.6 to 10 mm using the solid wire for gas shield arc welding.

According to the present invention, beads can be stably formed even in high-speed welding, and welded joints with excellent fatigue strength, tensile strength and toughness with reduced high temperature cracking properties can be obtained even in welding high tensile steel sheets having a thickness of 0.6 to 10 mm. .

The present invention can form wide and suitable beads with less slag and excellent electrodeposition paintability. This advantage is especially noticeable when welding steel sheets having a thickness of 0.6 to 10 mm at a high speed of 1.0 m / min or more. In conclusion, beads having a stable shape can be formed in high speed welding of steel sheets, and welded joints excellent in fatigue strength can be obtained. In addition, hot cracking can be reduced, and appropriate strength and toughness can be ensured.

Further objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the attached drawings.

As a result of earnest examination to achieve the above object, the present inventors have found that the following phenomena are caused by irregular bead formation, sulfur-induced hot cracking, and reduction of fatigue strength, strength, and toughness in welding metals in the welding of steel sheets having a thickness of 0.6 to 10 mm. I figured it out.

Molten metal on the molten pool surface of the regular weld bead is sucked backward from the hot portion to the cold portion, and the strength of the suction is proportional to the surface tension gradient due to the temperature difference, and the length of the molten pool. At high speed welding of 1.0 m / min or more, the melt extends in the weld line direction, and the flow rate of the molten metal is greatly increased. This is one of the factors causing irregular beads such as undercut beads and humping beads.

Although the original range of the molten metal solidification temperature is relatively narrow, sulfur acts as a trace amount to widen the solidification temperature range. In this step, the sulfur is enriched in the residual melt of the dendrite arrangement accompanying the solidification of the mother phase, and the sulfide is crystallized in the final stage of the mother phase solidification due to the eutectic solidification of the residual melt. The eutectic temperature of Fe-FeS is significantly lower than the melting point of iron. Hot cracking is due to the segregation of these low melting liquid phases and compounds at grain boundaries in the final stage of solidification.

Sulfur not only causes hot cracking but also thickens the sulfide as its amount increases, reducing the elongation and toughness of the material. Steels, such as sulfided free machining steels according to Japanese Industrial Standard (JIS) G 4804, i.e., machined steels, have improved machinability by containing a large amount of sulfur (SUM 24L, containing 0.26 to 0.35 mass% sulfur). However, sulfur content is generally minimized to less than 0.03% in weld metals that require some degree of elongation, toughness and other mechanical properties, since the presence of sulfur is very detrimental to these properties.

In addition, the fatigue limit of the weld joint of high tensile steel may be lower than the fatigue limit of ordinary steel as a base material. This is mainly due to local stress concentrations occurring at the toe of the weld. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the welding tip of a lap-fillet weld joint. In the joint shown in FIG. 1, the base material (lower plate) 1a is welded obliquely downward with another base material (top plate) 1b. The inventors have found that the stress concentration varies greatly depending on the portion where the surface of the base material 1a and the surface of the weld bead 2 intersect, that is, the shape of the weld tip, and the fatigue strength of the weld joint is 0.3 mm at the tip diameter ρ. It was found to increase by setting larger. However, the tip diameter p is small because the beads tend to be convex in the high speed welding of the high tensile steel sheet, so that the original fatigue strength of the high tensile steel sheet may not be sufficiently exhibited.

Sulfur (S) is an element that reduces the surface tension of molten metal and changes the surface tension gradient due to temperature difference. Thus, the inventors were able to successfully make the molten metal flow less backwards but more in the width direction by adjusting and specifying the content of sulfur and other elements. Thus, a composition was found that yields beads that are resistant to undercut and humming even at high speed welding. Specifically, by setting the sulfur content to 0.020 to 0.150 mass% based on the total mass of the wire, the molten metal could flow less backwards but more in the width direction. As a result, the tip diameter p shown in FIG. 1 becomes 0.3 mm or more, so that the fatigue strength of the weld joint in the high speed welding of the high tensile steel sheet can be improved.

The addition of sulfur increases hot cracking as described above. Sulfur-induced hot cracking can be lowered by raising the eutectic temperature. This can be achieved by dispersing sulfur on the mother phase by adding an appropriate amount of element with high affinity to sulfur to form a compound having a high melting point. Specifically, by setting the manganese content to 1.00 to 3.00 mass% based on the total weight of the wire, MnS is crystallized and the eutectic temperature can be increased. Sulfur can also be dispersed in the mother phase by incorporating at least one of Ti, Zr, La and Ce in an appropriate amount, since these elements serve to form sulfur-containing high melting compounds by forming sulfides. This can substantially prevent the formation of sulfides at grain boundaries.

In addition, by adjusting the content of the alloy component so that the A value determined according to the following Equation 1 is 100 or more, beads of a stable shape can be obtained even in the welding of high tensile steel sheets, high temperature cracking property is reduced, and fatigue strength is excellent. Weld joints can be obtained:

Equation 1

In the above formula, [Mn], [Ti], [Zr], [La], [Ce] and [S] represent Mn, Ti Zr, La, Ce and S contents (mass%) of the wire, respectively.

Based on the above findings, the present inventors achieved the solid wire for gas shield arc welding as the first embodiment of the present invention. The solid wire can form a bead having a stable shape and can form a weld joint with low hot crackability and excellent fatigue strength even in high-speed welding in gas shielded arc welding of a high strength steel sheet having a thickness of 0.6 to 10 mm.

Hot cracking properties increase with increasing sulfur content as described above. The high temperature cracking property is lowered by preventing the formation of the low melting point compound FeS, which is the main cause of the high temperature cracking. According to the present technology, the formation of the low melting point compound FeS is prevented by dispersing the sulfide formed by incorporating an element having affinity with sulfur and raising the eutectic temperature to the mother phase. As a second solution, the hot cracking property can be lowered by preventing the grains by uniformly dispersing the FeS by adding elements having high curability, which reduces the size of crystal grains formed as a result of solidification and thus the surface area of the grain boundary. Because it increases. Based on this, the inventors have found that in order to lower the hot crackability, an effective content of the element must be found.

Based on the above findings, the inventors of the present invention have achieved a solid shield for gas shield arc welding as a second embodiment of the present invention. This solid wire can produce beads having a stable shape even at high speed welding and can produce weld joints with low hot cracking properties and good fatigue strength, tensile strength and toughness in welding high tensile steel sheets.

(1) By setting the sulfur content to 0.020 to 0.150 mass%, the molten metal can flow less backwards and more in the width direction.

(2) By setting the Mn content to 1.00 to 3.00 mass%, the MnS is crystallized and the eutectic temperature rises so that the cracking property can be lowered.

(3) 0.005 to 0.50% by mass of niobium (Nb), 0.005 to 0.5% by mass of vanadium (V), 0.010 to 0.5% by mass of aluminum (Al), 0.005 to 0.5% by mass of chromium (Cr), and 0.005 to 0.5 of nickel (Ni) By incorporating at least one of the mass% and the 0.001 to 0.010 mass% of boron (B), the curability increases and the crystal grain becomes finer. By incorporating the appropriate amount of the element, the texture formed as a result of solidification becomes finer, thereby increasing the surface area of the grain boundary. The FeS liquid phase is prevented from being dispersed and dispersed, which reduces hot cracking. FeS liquid phase forms at grain boundaries and dendrite arrays and causes cracks. The elements also serve to reduce hot cracking, because they form finer grains to improve toughness and relieve stress concentration in the FeS liquid phase upon solidification due to expansion and contraction during welding.

(4) The additional elements listed in (3) are resistant to the formation of slag. That is, they form less slag and contribute to the formation of appropriate beads. Thus, an appropriate amount of the element can reduce hot cracking properties and ensure adequate strength and toughness without compromising the benefits of the element.

The reason for defining the composition of the welding wire according to the present invention is explained below. First, the composition of the solid wire for gas shield arc welding as the first embodiment of the present invention will be described.

Carbon content: 0.03 to 0.15 mass%

Carbon (C) is an element necessary to secure the strength of the welded metal and is effective in accelerating deoxidation. However, the weld metal has insufficient strength when the carbon content is less than 0.03 mass% based on the total mass of the wire. On the other hand, the weld metal, when the carbon content exceeds 0.15% by mass, the toughness decreases and the high temperature cracking property increases. Therefore, the carbon content is set at 0.03 to 0.15 mass% based on the total weight of the wire.

Silicon content: 0.50-1.50 mass%

Silicon (Si) is an element that greatly promotes deoxidation, is required for improving the strength of steel, and serves to improve the conformability of beads. However, these advantages are not obtained if the silicon content is less than 0.50 mass% based on the total mass of the wire. On the other hand, the peelability of the droplets and the toughness of the weld metal are damaged when the silicon content exceeds 1.50% by mass. Therefore, the silicon content here is set at 0.50 to 1.50 mass% based on the total mass of the wire.

Manganese Content: 1.00-3.00 mass%

Manganese (Mn), like silicon, is an effective element for promoting deoxidation and serves to improve the mechanical properties of the weld metal. In addition, by increasing the eutectic temperature by crystallizing MnS serves to reduce the high temperature cracking properties. However, if the manganese content is less than 1.00 mass% based on the total mass of the wire, the high temperature crackability increases. On the other hand, when the amount of manganese in the weld metal exceeds 3.00 mass% and is excessive, the toughness is lowered. Therefore, the manganese content is set to 1.00 to 3.00 mass% based on the total mass of the wire. Preferably it is set to 1.50 mass% or more.

Sulfur content: 0.020 to 0.150 mass%

Sulfur (S) serves to reduce the surface tension of the molten metal, and when added in an appropriate amount to improve the followability between the bead and the base material at the weld tip and to improve the fatigue strength of the weld joint. However, this advantage is not obtained if the sulfur content is less than 0.020 mass% based on the total mass of the wire. On the other hand, even when the content of other elements is adjusted, high temperature cracking tends to occur when the sulfur content exceeds 0.150 mass%. Therefore, the sulfur content is set at 0.020 to 0.150 mass% based on the total mass of the wire. Preferably it is set to 0.040 mass% or more, More preferably, it is set to 0.060 mass% or more.

"At least one selected from the group consisting of 0.01 to 0.20 mass% of titanium (Ti), 0.01 to 0.20 mass% of zirconium (Zr), 0.01 to 0.05 mass% of lanthanum (La) and 0.01 to 0.05 mass% of cerium (Ce)"

Titanium (Ti), zirconium (Zr), lanthanum (La), and cerium (Ce) are elements that readily combine with sulfur to form hot melt sulfides. Sulfur may be dispersed in the mother phase by adding one or more of the above elements. However, this advantage is not obtained even if two or more kinds of the above elements are added to the solid wire as long as the content of each element is less than 0.01% by mass based on the total mass of the wire. On the other hand, when the titanium content or the zirconium content exceeds 0.20% by mass, the droplets become thick, the movement of the droplets is hindered, and the slag is excessively formed, which impairs the welding workability. Therefore, the content of Ti and / or Zr, when added, is set at 0.01 to 0.20 mass% based on the total mass of the wire. When the content of lanthanum or cerium exceeds 0.05% by mass, the sulfide becomes thicker, and the steelmaking yield decreases, thereby increasing the cost. Therefore, the content of La and / or Ce when added is set to 0.01 to 0.05% by mass based on the total mass of the wire.

Phosphorus content: 0.025 mass% or less

Phosphorus (P) contaminates the river as an unavoidable impurity. Phosphorus is an element that increases hot crackability, and its content should preferably be reduced. However, phosphorus in a content of 0.025% by mass based on the total mass of the wire may be used. Therefore, the phosphorus content is controlled to 0.025 mass% or less based on the total mass of the wire.

"A": more than 100

According to the present invention, the A value determined according to the following Equation 1 is specified to be 100 or more. In Equation 1, [Mn], [Ti], [Zr], [La], [Ce], and [S] represent Mn, Ti, Zr, La, Ce, and S contents (mass%) of the wire, respectively. . Hot cracking properties increase when the A value is less than 100. On the other hand, by adjusting the Mn, Ti, Zr, La, Ce, and S content on the basis of the total mass of the wire so that the A value is 100 or more, MnS is crystallized and the eutectic temperature rises, and the low melting liquid phase and the final solidification of the compound Separation at the grain boundary in the step is prevented. In addition, hot melt sulfides containing at least one of Ti, Zr, La and Ce can be formed. Therefore, high temperature cracking property can be greatly reduced. In Equation 1 below, the coefficients are defined based on the crack test results, and these coefficients are probably greatly influenced by the sulfide formation tendency of the individual elements.

Equation 1

Unavoidable impurities contained in the solid wire according to the present invention include, for example, Cu, Al, Ni, Cr, Mo and B in addition to phosphorus (P).

Next, the reason for defining the composition of the welding wire for gas shield arc welding as the second embodiment of the present invention will be described.

Carbon content: 0.02 to 0.15 mass%

Carbon (C) is an element necessary to secure the strength of the welded metal and is effective as a deoxidation element. The strength of the weld metal is insufficient when the carbon content is less than 0.02 mass% based on the total mass of the wire. On the other hand, when the carbon content exceeds 0.15% by mass, the toughness of the weld metal decreases and the high temperature cracking property increases. Excessive addition of carbon impairs the dripping property and causes a large amount of spatters. This leads to poor welding workability and a large amount of slag. Therefore, the carbon content in the present invention is set to 0.02 to 0.15% by mass.

Silicon content: 0.50-1.50 mass%

Silicon (Si) is also an element that contributes greatly to deoxidation, improves the strength of the steel, and improves the followability of the beads. This advantage is insufficient if the silicon content is less than 0.50 mass% based on the total mass of the wire, and the beads have poor trackability with poor tip shape, which leads to stress concentration and reduced fatigue strength. The silicon content is preferably at least 0.60%. On the other hand, when the silicon content exceeds 1.50 mass%, the melt has an excessive viscosity (flow resistance), which often results in humping beads in high speed welding. Excess silicon impairs the dripping property and causes a large amount of spatters. This leads to poor welding workability and a large amount of slag. The silicon content is more preferably 1.20% by mass or less.

Manganese Content: 1.00-3.00 mass%

Manganese (Mn) is a useful element as a deoxidation element, such as silicon (Si), and serves to improve the mechanical properties of the weld metal. In addition, by increasing the eutectic temperature as a result of the crystallization of MnS serves to lower the high temperature cracking properties. If the manganese content is less than 1.00 mass% based on the total mass of the wire, the hot cracking property increases, and the weld metal has insufficient strength. On the other hand, when the manganese content of the weld metal exceeds 3.00 mass%, the molten pool has excessive viscosity (flow resistance), which often results in humping beads and large amounts of slag in high speed welding. Therefore, manganese content is set to 1.00-3.00 mass%. More preferably, it is 1.00-2.00 mass%.

Phosphorus content: 0.025 mass% or less

Phosphorus (P) is an element that increases hot crackability. The phosphorus content is preferably minimized because hot melt phosphorus compounds cannot be formed even when alloying elements are added. However, phosphorus of 0.025 mass% is all right.

Sulfur content: 0.020 to 0.150 mass%

Sulfur (S) serves to reduce the surface tension of the molten metal, and when added in an appropriate amount to improve the followability between the bead and the base material at the weld tip and to improve the fatigue strength of the weld joint. However, a large amount of sulfur without addition of the following specific elements thickens the sulfides formed at the grains and grain boundaries, thereby lowering the strength and toughness of the weld metal. This benefit can be obtained by adding sulfur in an amount of at least 0.020% by mass. On the other hand, even when the content of other elements is adjusted, high temperature cracking tends to occur when the sulfur content exceeds 0.150 mass%. Therefore, sulfur content is set to 0.020-0.150 mass%. Preferably it is set to 0.040-0.150 mass%, More preferably, it is set to 0.050-0.150 mass%.

Niobium content: 0.005 to 0.50 mass%

Niobium (Nb) is affinity for sulfur and easily forms sulfides. An appropriate amount of niobium prevents the formation of FeS which causes hot cracking. In addition, since it is an element that improves hardenability and makes grains finer, it serves to reduce high temperature cracking property and secure proper strength and toughness. However, these advantages are not obtained if the niobium content is less than 0.005 mass% and the hot cracking property is increased. Niobium content is more preferably 0.02 mass% or more. On the other hand, if the niobium content exceeds 0.50% by mass, the above advantages are saturated, and during solidification, crystallization occurs at grain boundaries and dendrites, and conversely, high temperature crackability increases. Excess niobium increases the cost of manufacturing solid wires, increases the viscosity (flow resistance) of the melt, leads to humping beads, and increases spatter in high speed welding.

"At least one selected from the group consisting of 0.005 to 0.5 mass% of vanadium (V), 0.010 to 0.5 mass% of aluminum (Al), 0.005 to 0.5 mass% of chromium (Cr) and 0.005 to 0.5 mass% of nickel (Ni)"

Vanadium (V), aluminum (Al), chromium (Cr) and nickel (Ni) are elements that increase the hardenability and act to further refine the grains of the weld metal formed as a result of welding, thereby ensuring proper strength and toughness. Reduce hot cracking. In order to show these advantages, the content of each of V, Cr and Ni should be at least 0.005 mass%, and the Al content should be at least 0.010 mass%. More preferably, the content of each of V, Cr and Ni is at least 0.02 mass%, and the Al content is at least 0.030 mass%. On the other hand, when the content of the elements exceeds 0.5% by mass, respectively, the manufacturing cost of the solid wire increases, and the viscosity (flow resistance) of the molten paper increases, resulting in humping beads and an increased amount of spatter in high speed welding.

Boron content: 0.001 to 0.010 mass%

Boron (B) is an element that increases the hardenability, and serves to reduce the crystal grains of the weld metal formed as a result of welding, to secure appropriate strength and toughness, and to reduce hot cracking properties. In order to show these advantages, the boron content should be at least 0.001 mass%. On the other hand, the upper limit of the boron content is set to 0.010% by mass or less, since the high temperature crackability increases when the boron content exceeds 0.010% by mass. Therefore, the boron content is set at 0.001 to 0.010 mass%.

Welding method according to the invention

Solid wires according to the first and second embodiments of the invention are used for gas shielded arc welding of steel sheets having a thickness of 0.6 to 10 mm. Preferred welding methods and welding conditions are as follows. The gas shield arc welding method herein can be any welding method such as CO ₂ welding, metal activated gas (MAG) welding, metal inert gas (MIG) welding, and tungsten inert gas (TIG) welding. Welding conditions such as output power or current and welding speed can typically be set according to the type of processing machine, the thickness and shape of the workpiece. MAG pulse welding, MIG pulse welding, or TIG pulse welding is more effective. The target weld joint can be any suitable one, such as a butt joint or a lap joint, depending on the portion to be joined. The present invention can be applied to any junction.

Pulse welder

Pulse welders are preferably used herein to ensure high speed weldability and arc stability and to reduce fume of steel sheet welding. The pulse condition may be a peak current of 350A to 600A, a base current of 30A to 100A, and 0.8 to 5.0 milliseconds at 1 peak (from the start of pulse generation to the end of the pulse drop through a constant peak), but is not limited thereto. Do not. Welding in the present invention can be performed under the above conditions.

0.6 to 10mm thick steel sheet

Normal reverse-polar arc welding is difficult to carry out if the steel sheet thickness is less than 0.6 mm because the steel sheet penetrates and melts due to the arc force. On the other hand, if the thickness exceeds 10 mm, the deformation force is increased so that the stress deformation of the weld metal due to thermal expansion and thermal contraction is excessively applied, and the risk of hot cracking increases because the molten pool is cooled more quickly. In addition, the melt formed by welding using the wire according to the present invention has a low viscosity (flow resistance) so that the upper leg flows when the T-type horizontal fillet welding is performed in a large leg length one pass. Therefore, the thickness of the welded steel sheet is preferably 0.6 to 10 mm. Regarding the strength of the welded steel sheet, the present invention can be applied to a wide range of steel sheets from standard mild steel sheets to high tensile steel sheets. The upper limit of the strength of the steel sheet is not particularly limited.

Test Example 1

The advantages of the present invention will be described in more detail with reference to several examples below, in comparison with comparative examples which depart from the scope of the present invention. First, Test Example 1 regarding a solid wire according to the first embodiment of the present invention will be described.

In Test Example 1, gas shield arc welding was performed using a solid wire having the composition of Table 1 below. Bead formation ability in high speed welding, mechanical properties of the weld metal, tip diameter p, high temperature crackability, and weldability were evaluated. The balance in the composition of the solid wire of Table 1 is iron and inevitable impurities.

Next, the evaluation method of a characteristic will be described.

Mechanical Properties of Welded Metals

The mechanical properties of the weld metal were determined by the tension test method for the butt weld joint defined in Japanese Industrial Standard (JIS) Z 3121, and the impact test method for the weld joint defined in JIS Z 3128. In these tests, samples having a tensile strength of at least 560 N / mm ² at a test temperature of −20 ° C. and an absorbent energy of at least 100 J in a Charpy impact test were evaluated as “good” and 560 N / mm ² at a test temperature of −20 ° C. Samples with less than 100 J absorbed energy in tensile strength below and Charpy impact test were rated as "poor".

Bead Formability in High Speed Welding

Bead formation ability in the high speed welding was evaluated as follows. A sample wrap joint of a high tensile strength steel sheet having a composition of Table 2 and having a thickness of 2.3 mm, using a gas phase mixture of 80% by volume Ar and 20% by volume of CO ₂ as a shield gas, has a root spacing of 1.0 mm, a welding current of 200 to 300 A, And MAG pulse welding at a welding speed of 1.3 to 1.5 m / min. Samples with no undercuts, humping beads, melts and perforations and capable of crosslinking across the gap throughout the weld were rated as "good" and samples with defects such as undercuts, humping beads, melts or perforations were rated as "bad". .

Weldability

Welding workability was evaluated by using high speed cameras to observe the regularity of arc stability and droplet movement, and to determine the amount of scattered spatters. In this procedure, pulseless MAG welding was performed with a welding current of 200 to 300 A using a gaseous mixture of 80 vol% Ar and 20 vol% CO ₂ as shield gas. Samples that provide a stable arc, have a high degree of regularity of drop movement, and obtain a small amount of spatter are evaluated as "good", and have a sample that is poor in at least one of arc stability, regularity of drop movement, and amount of spatter. Poor ".

Hot Cracking of Welded Metals

Hot cracking properties of the weld metal were evaluated by fishbone crack test and crater crack test. First, the method of performing a fishbone crack test is explained. 2A is a cross-sectional view showing where the test piece is sampled, and FIG. 2B is a plan view showing how the test piece is prepared in a fishbone cracking test. Referring to FIG. 2A, a two-ply high tensile steel sheet having a thickness of 20 mm and including SM490A mild steel as the base material 11 is butt using a backing metal 13 including mild steel SM490A at an inclination angle of 45 °. Welded. The resulting weld joint was mechanically cut to a thickness of 5 mm to obtain a test piece 14 for a fishbone crack test of width 175 mm, length 250 mm and thickness 5 mm.

Next, as shown in FIG. 2B, the slits 15 were formed at regular intervals at both ends of the long sides of the test piece 14. The slit 15 has a length that increases from one short side to the other short side so that the thermal strain (thermal stress strain) applied to the molten metal changes continuously along the length of the slit. Specifically, the thermal deformation is large on one short side where the slit 15 has a small length, and small on the other short side where the slit 15 has a large length. The test piece 14 was arrange | positioned on the copper plate 16 of width 750mm, length 500mm, and thickness 25mm, and TIG welding which a test plate carrier moves is performed under the conditions of Table 3 below. In this procedure, solidification due to shrinkage / solidification deformation during the cooling process at the plate end by applying a static arc for about 5 seconds to the plate end with the shorter length of the slit to melt the plate end sufficiently and thermally deform the plate end. Cracks (hot cracks) are induced. Next, welding was performed in the welding direction 17 from the plate end where the crack occurred to the other plate end where the slit has a longer length. The high temperature crack resistance was evaluated based on how far (how long) the crack starting from the plate end of the test piece 14 extends. The crack length corresponds to thermal deformation, ie hot cracking. Specifically, color matching was performed after welding, the length of the cracks formed in the beads 12 was measured, and the ratio of the uniform length to the test piece length (crack ratio) was determined. Samples with a crack ratio of 5% or less were rated "good", and samples with a crack ratio above 5% were rated "bad".

In crater cracking tests using SM490A mild steel, three weld beads, each having a length of about 70 mm, were welded from 200 to 300 A by pulse-free MAG welding at a depth of 5 mm at an inclination angle of 90 ° on the V-shaped groove slope under the same conditions. It was formed intermittently using a gaseous mixture of 80 vol% Ar and 20 vol% CO ₂ as shield gas at current. The total length of the cracks at each weld crater surface was determined. The ratio of the crack length to the length or diameter of the weld crater was determined and the average of the ratio of the three weld craters was used as an index. Samples with an average crack ratio of 15% or less were evaluated as "good" and samples with an average crack ratio above 15% were evaluated as "bad".

Tip diameter ρ

As the tip diameter ρ increases, the stress concentration is relaxed and the fatigue strength is improved, so the tip diameter ρ is measured as an index of the fatigue strength of the weld joint for convenience. Specifically, the lap joint of the high tensile strength steel sheet having the composition shown in Table 2 and having a thickness of 2.9 mm was 80% by volume of Ar and 20% by volume of CO ₂ as shield gas at an average welding current of 200 to 300A and a welding speed of 1.3 to 1.5 m / min. Gas phase mixtures were used to perform MAG pulse welding following automatic wrap-fillet welding. Then, the tip diameter ρ as shown in FIG. 1 was measured. Samples with a tip diameter p of 0.3 mm or more were evaluated as "good", and samples with a tip diameter p of less than 0.3 mm were evaluated as "bad". The evaluation results are shown in Table 4 below.

Table 4 shows that the solid wires of Examples 1-20 according to the invention show excellent results in all evaluations. On the other hand, the solid wire of Comparative Examples 21 to 40 outside the scope of the present invention is poor in one or more of the bead forming ability, high-temperature cracking property, and weld workability of the bead forming ability, high-speed welding metal in the high-speed welding. Specifically, the solid wire of Comparative Example 21 exhibits insufficient weld metal strength because it has a carbon content less than the range specified in the present invention. The solid wire of Comparative Example 22 exhibits insufficient weld metal toughness due to the carbon content exceeding the range defined in the present invention. In addition, this solid wire has an increased hot cracking property because it has an A value less than the range defined in the present invention.

The solid wire of Comparative Example 23 exhibits insufficient weld metal strength because it has less silicon content than the range specified in the present invention. The solid wire also exhibits poor bead formation ability in high speed welding and has a small tip diameter p. On the other hand, the solid wire of Comparative Example 24 had a silicon content exceeding the range defined in the present invention, indicating insufficient welded metal toughness, coarse drip, and increased spatter. The solid wire of Comparative Example 25 had a manganese content less than the range defined in the present invention and an A value less than the range specified in the present invention, indicating insufficient molten metal strength and increased hot cracking properties. On the other hand, the solid wire of Comparative Example 26 has a manganese content in excess of the range specified in the present invention, which indicates insufficient weld metal toughness.

The solid wire of Comparative Example 27 had a phosphorus content in excess of the range specified in the present invention, thereby showing increased hot crackability. The solid wire of Comparative Example 28 had less sulfur content than the range defined in the present invention, but exhibited poor bead formation ability and small tip diameter p in high speed welding, although it had low hot cracking property. On the other hand, the solid wire of Comparative Example No. 29 has a sulfur content exceeding the range specified in the present invention and an A value smaller than the range specified in the present invention, so that even if the content of other elements is within the range specified in the present invention, the high temperature crack Indicates the last name. Each of the solid wires of Comparative Examples 30, 32, 34 and 35 has a high A value that is smaller than the range defined in the present invention and shows high hot crackability.

The solid wire of Comparative Example 31 had a titanium content in excess of the range defined in the present invention, resulting in thickened droplets, increased spatter and increased slag. Likewise, the solid wire of Comparative Example 33 had a zirconium content in excess of the range defined in the present invention, showing coarse drip, increased spatter and increased slag. The solid wires of Comparative Examples 36, 37, and 38 did not contain any of Ti, Zr, La, and Ce, and each had an A value less than the range specified in the present invention, showing high high temperature crackability. The solid wires of Comparative Examples 39 and 40 containing none of Ti, Zr, La, and Ce have a sulfur content exceeding the range defined in the present invention, and exhibit high hot crackability.

Test Example 2

Test Example 2 according to the second embodiment of the present invention will be described. In this test example, the steel plate was welded using a wire having the composition shown in Table 5 below. Bead formation ability in high speed welding, mechanical properties of the weld metal, tip diameter p, coating ability, high temperature crackability, and welding workability were evaluated. The balance of the solid wire of Table 5 is Fe and inevitable impurities.

Next, the evaluation method of a characteristic will be described.

Mechanical Properties of Welded Metals

The mechanical properties of the weld metal were determined by the tension test method for the butt weld joint defined in Japanese Industrial Standard (JIS) Z 3121, and the impact test method for the weld joint defined in JIS Z 3128. In these tests, samples having a tensile strength of at least 560 N / mm ² at a test temperature of −20 ° C. and an absorbent energy of at least 100 J in a Charpy impact test were evaluated as “good”, and a tensile of less than 560 N / mm ² at a test temperature of −20 ° C. Samples with an absorbed energy of less than 100 J in the strength or Charpy impact test were rated "bad."

Bead Formability in High Speed Welding

Bead formation ability in the high speed welding was evaluated as follows. A sample wrap joint of a high strength steel sheet having a composition of Table 6 and having a thickness of 2.9 mm using a gas phase mixture of 80% by volume of Ar and 20% by volume of CO ₂ as shield gas, with a root spacing of 1.0 mm, a welding current of 250 A, and 1.5 MAG pulse welding was carried out at a welding speed of m / min. Samples that were free of undercuts, humping beads, melts and perforations and could be crosslinked across the gap throughout the weld were rated "good" and samples with defects were rated "bad".

Weldability

Welding workability was evaluated by using high speed cameras to observe the regularity of arc stability and droplet movement, and to determine the amount of scattered spatters. In this procedure, pulseless MAG welding was performed with a welding current of 250 A and a welding speed of 1.0 m / min using a gaseous mixture of 80 vol% Ar and 20 vol% CO ₂ as shield gas. Samples that provide a stable arc, have a high degree of regularity of drop movement, and obtain a small amount of spatter are evaluated as "good", and have a sample that is poor in at least one of arc stability, regularity of drop movement, and amount of spatter. Poor ".

Coverage

The coating ability was evaluated as the risk of the coating peeling off due to the peeling of the slag in the electrodeposition coating step after welding. The risk was determined based on the area of slag formed on the bead surface after welding. In this procedure, a pulseless MAG welding was performed with a gaseous mixture of 80% Ar and 20% CO ₂ as a shield gas with a welding current of 250A and a welding speed of 1.0 m / min. Samples with a ratio of slag area to bead surface area of less than 10% were evaluated as "good", and samples with a ratio of 10% or more were rated as "bad".

Fishbone crack test

The high temperature cracking property of the weld metal was evaluated based on the fish bone crack test and the crater crack test results described later.

Where the specimen is sampled is shown in Figure 2a. Referring to FIG. 2A, two-ply high tensile steel sheets having a thickness of 20 mm and containing SM490A mild steel as the base material 11 were butt welded using a backing material 13 including mild steel SM490A at an inclination angle of 45 °. The resulting weld joint was mechanically cut to a thickness of 5 mm to obtain a test piece 14 for a fishbone crack test of width 175 mm, length 250 mm and thickness 5 mm.

Next, as shown in FIG. 2B, the slits 15 were formed at regular intervals at both ends of the long sides of the test piece 14. The slit 15 has a length that increases from one short side to the other short side so that the thermal strain (thermal stress strain) applied to the molten metal changes continuously along the length of the slit. Specifically, the thermal deformation is large on one short side where the slit 15 has a small length, and small on the other short side where the slit 15 has a large length. The test piece 14 was arrange | positioned on the copper plate 16 of width 750mm, length 500mm, and thickness 25mm, and TIG welding which a test plate carrier moves is performed under the conditions of Table 3 below. In this procedure, solidification due to shrinkage / solidification deformation during the cooling process at the plate end by applying a static arc for about 5 seconds to the plate end with the shorter length of the slit to melt the plate end sufficiently and thermally deform the plate end. Cracks (hot cracks) are induced. Next, welding was performed in the welding direction 17 from the plate end where the crack occurred to the other plate end where the slit has a longer length. The high temperature crack resistance was evaluated based on how far (how long) the crack starting from the plate end of the test piece 14 extends. The crack length corresponds to thermal deformation, ie hot cracking. Specifically, color matching was performed after welding, the length of the cracks formed in the beads 12 was measured, and the ratio of the uniform length to the test piece length (crack ratio) was determined. Samples with a crack ratio of 5% or less were rated "good", and samples with a crack ratio above 5% were rated "bad".

Crater Crack Test

Using SM490A mild steel, three weld beads each having a length of about 70 mm were formed intermittently by pulse-free MAG welding at a depth of 5 mm at an inclination angle of 90 ° on the V-shaped groove slope under the same conditions. The total length of the cracks at each weld crater surface was determined. The ratio of the crack length to the length or diameter of the weld crater was determined and the average of the ratio of the three weld craters was used as an index. Samples with an average crack ratio of 15% or less were evaluated as "good" and samples with an average crack ratio above 15% were evaluated as "bad".

Tip diameter ρ

As the tip diameter ρ increases, the stress concentration is relaxed and the fatigue strength is improved, so the tip diameter ρ is measured as an index of the fatigue strength of the weld joint for convenience. Specifically, the lap joint of a high-strength steel sheet having a composition of Table 6 and having a thickness of 2.9 mm was a gaseous mixture of 80% by volume of Ar and 20% by volume of CO ₂ as a shield gas at an average welding current of 250A and a welding speed of 1.5m / min. Using MAG pulse welding according to horizontal wrap welding. Then, the tip diameter ρ as shown in FIG. 1 was measured. Samples with a tip diameter p of 0.3 mm or more were evaluated as "good", and samples with a tip diameter p of less than 0.3 mm were evaluated as "bad". The evaluation results are shown in Table 8 below.

The results show that the solid wires of Examples 1-25 have a composition within the range defined in the present invention and are excellent in all evaluations. On the other hand, the solid wires of Comparative Examples 26 to 50 have a composition outside the range specified in the present invention and have bead forming ability in high speed welding, mechanical properties of weld metal, tip diameter p, high temperature crackability, coating ability, and welding workability. At least one of is bad.

Specifically, Table 8 shows that the solid wires of Examples 1 to 25 having a composition within the range defined in the present invention are excellent in all evaluations. On the other hand, the solid wires of Comparative Examples 26 to 50 have a composition outside the range specified in the present invention and have bead forming ability in high speed welding, mechanical properties of weld metal, tip diameter p, high temperature crackability, coating ability, and welding workability. At least one of is bad.

The solid wires of Comparative Examples 26 to 30 do not contain any of Cr, Ni, Nb, V, Al and B or contain one of these elements in an amount less than the range specified in the present invention, thereby increasing the hot cracking properties. And insufficient weld metal strength and toughness. The solid wire of Comparative Example 31 had an excessively high carbon content, indicating insufficient weld metal toughness and increased hot cracking. It also shows a large amount of slag that causes thick spots, increased spatter, and poor coverage. The solid wire of Comparative Example 32 had an excessively high manganese content, exhibiting insufficient toughness of the weld metal, causing humping beads in high speed welding, and failing to form normal beads. In addition, a large amount of slag is generated to show poor coating ability. The solid wire of Comparative Example 33 had an excessively high silicon content, indicating insufficient toughness, coarse drip, and increased spatter of the weld metal. In addition, a large amount of slag is generated to show poor coating ability. The solid wire of Comparative Example 34 has an excessively high phosphorus content and shows high hot crackability.

The solid wires of Comparative Examples 35 and 36 had an excessively low sulfur content, showing low hot cracking properties but poor bead formation ability and high tip diameter in high speed welding. The solid wires of Comparative Examples 37 to 40 have an excessively high content of at least one of Cr, Ni, V, and Al, which is expensive and results in humping beads in high speed welding. In addition, a thick drop and a large amount of spatter are shown. The solid wire of Comparative Example 41 has an excessively high niobium content, exhibits high hot cracking properties but is expensive, resulting in humping beads in high speed welding. It also exhibits thick droplets and results in a large amount of spatters. The solid wire of Comparative Example 42 has an excessively high boron content and shows high hot crackability. The solid wire of Comparative Example 43 has an excessively high boron and vanadium content, exhibits high hot crackability, is expensive, and results in humping beads in high speed welding. It also exhibits thick droplets and results in a large amount of spatters.

The solid wire of Comparative Example 44 had an excessively high silicon content and an excessively low manganese content, indicating insufficient weld metal strength, coarse drip, and increased spatter. It also results in humping beads and large amounts of slag in high speed welding, and shows poor coverage and high hot cracking properties. The solid wire of Comparative Example 45 had an excessively high sulfur content, indicating insufficient weld metal strength and toughness and high hot cracking properties. The solid wire of Comparative Example 46 had an excessively low carbon and manganese content, indicating insufficient weld metal strength and high hot cracking properties. The solid wire of Comparative Example 47 had an excessively high carbon content and an excessively low silicon content, indicating insufficient weld metal toughness and increased hot cracking. It also exhibits poor followability of beads, small tip diameter, results in thick droplets, increased spatters, and large amounts of slag, and poor coverage. The solid wire of Comparative Example 48 had an excessively low silicon content and an excessively high phosphorus content, indicating insufficient weld metal strength, poor followability of the beads, small tip diameter, and high hot cracking properties.

The solid wire of Comparative Example 49 had an excessively high carbon and manganese content showing excessive weld metal strength and poor toughness. In addition, high speed welding results in humping beads, failing to form normal beads, and exhibit coarse droplets, increased spatter, large amounts of slag, poor coverage, and high hot cracking properties. The solid wire of Comparative Example 50 had an excessively low carbon content and an excessively high phosphorus content, indicating insufficient weld metal strength and high hot cracking properties.

According to the present invention, there is provided a solid wire capable of stably forming beads and forming weld joints having low high temperature crackability and excellent fatigue strength in gas shielded arc welding of high tensile steel sheets having a thickness of 0.6 to 10 mm even in high speed welding. can do.

Claims (5)

Solid wire for gas shield arc welding, Based on the total mass of the wire, 0.03 to 0.15 mass% of carbon (C); Silicon (Si) 0.50-1.50 mass%; 1.00-3.00 mass% of manganese (Mn); Sulfur (S) from 0.020 to 0.150 mass%; And 0.01 to 0.20 mass% of titanium (Ti), 0.01 to 0.20 mass% of zirconium (Zr), 0.01 to 0.05 mass% of lanthanum (La), and 0.01 to 0.05 mass% of cerium (Ce). , Balance is iron and inevitable impurities, The content of phosphorus (P) as an unavoidable impurity is 0.025 mass% or less, Solid wire for gas shield arc welding having an A value of 100 or more determined according to Equation 1 below: Equation 1

In the above formula, [Mn], [Ti], [Zr], [La], [Ce] and [S] represent Mn, Ti, Zr, La, Ce and S contents (mass%) of the wire, respectively. The method of claim 1, Solid wire for gas shielded arc welding with a manganese (Mn) content of 1.50 to 3.00 mass%. The method of claim 1, Solid wire for gas shielded arc welding with a sulfur (S) content of 0.040 to 0.150 mass%. Solid wire for gas shield arc welding, Based on the total mass of the wire, 0.02 to 0.15 mass% of carbon (C); Silicon (Si) 0.50-1.50 mass%; 1.00-3.00 mass% of manganese (Mn); Sulfur (S) from 0.020 to 0.150 mass%; 0.005 to 0.5 mass% of niobium (Nb); And Vanadium (V) 0.005 to 0.5 mass%, aluminum (Al) 0.010 to 0.5 mass%, chromium (Cr) 0.005 to 0.5 mass%, nickel (Ni) 0.005 to 0.5 mass% and boron (B) 0.0010 to 0.0100 mass% At least one selected from the group consisting of: Balance is iron and inevitable impurities, Solid wire for gas shielded arc welding, wherein the content of phosphorus (P) as an unavoidable impurity is 0.025 mass% or less. A method of welding a gas shielded arc, comprising welding a mild steel sheet or high tensile steel sheet having a thickness of 0.6 to 10 mm using the solid wire according to claim 1.

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