JP2003225794A - Steel wire for gas-shielded arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide welding wire which can be stably fed even when used, e.g. for gas-shielded arc welding performed under the severe conditions, e.g. that the feeding rate of the welding wire increases, and the temperature of the welding wire increases. <P>SOLUTION: In the steel wire for gas-shielded arc welding, the surface of steel elemental wire containing, by mass, ≤0.20% C, 0.25 to 2.5% Si, 0.45 to 3.5% Mn and ≤0.0020% Ca is provided with a solid lubricant layer containing 15 to 70% of one or more kinds selected from MoS<SB>2</SB>and BN, ≤2% wax, a 2 to 70% K compound and 5 to 70% copper powder in 0.2 to 1.0 g per 10 kg of the steel elemental wire, and the surface of the solid lubricant layer is provided with a lubricant layer consisting of fatty acid ester and/or lubricating oil in 0.2 to 1.8 g per 10 kg of the steel elemental wire. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire for gas shielded arc welding, and particularly to automatic welding using a welding robot or welding with a large welding current, in which the feedability of the welding wire and the stability of the arc are important. The present invention relates to a gas-shielded arc welding steel wire (hereinafter referred to as a welding wire) suitable for gas-shielded arc welding of steel frames and bridges.

[0002]

2. Description of the Related Art In MAG welding, an oxidizing gas such as carbon dioxide gas, argon gas, or a mixed gas containing carbon dioxide gas and oxygen gas is used as a shield gas, and a welding wire having a diameter of 0.6 to 1.6 mm is used as a consumable electrode. 4 to 20 m / m
This is a welding method in which welding is performed at a welding speed of in, and in order to maintain its stable weldability, it is necessary to stably feed the welding wire. So on the surface of the welding wire
We are improving the feedability of the welding wire by applying Cu plating or applying lubricating oil.

However, in recent years, as gas shielded arc welding with a large current using a welding robot has been put into practical use, the feed rate of the welding wire has increased and the temperature of the welding wire has increased. As a result, the feeding of the welding wire becomes unstable, making it impossible to maintain the stability of the arc, which is a cause of hindrance to the welding work. In order to maintain stable weldability in a welding method in which the feed rate of the welding wire increases and the temperature of the welding wire rises, various techniques for improving the feedability of the welding wire have been proposed. .

[0004] For example, Japanese Patent Laid-Open No. 5-23731 discloses that a steel wire as a material is made to retain a lubricant composed of polytetrafluoroethylene, MoS ₂ , graphite and minerals on the surface thereof, and the welding wire feeding property is improved. A technique for improving the above is disclosed.
Further, Japanese Patent Application Laid-Open No. 11-217578 discloses a technique for improving the feedability of a welding wire by holding a lubricant made of MoS ₂ or WS ₂ , ester, petroleum wax or the like on the surface of a steel wire as a raw material. Is disclosed.

[0005]

[Patent Document 1] Japanese Patent Laid-Open No. 5-23731

[Patent Document 2] Japanese Patent Laid-Open No. 11-217578

[0006]

SUMMARY OF THE INVENTION
With the technology disclosed in Japanese Patent No. 5-23731 and Japanese Patent Laid-Open No. 11-217578, the stability of welding wire feeding is still maintained when applied to gas shield arc welding with a large current using a welding robot. It is inevitable that it will not be possible and will interfere with the welding work.

Therefore, an object of the present invention is to perform a gas shielded arc under severe conditions, such as high current welding using a welding robot, where the feeding speed of the welding wire is increased and the temperature of the welding wire is increased. It is to provide a steel wire for gas shielded arc welding (that is, a welding wire) that can obtain stable feedability even when used for welding.

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention have earnestly studied the phenomenon in which the feedability of a welding wire becomes unstable when performing gas shielded arc welding with a large current using a welding robot. As a result, it was found that the composition of the steel wire used as the material, the composition of the lubricant applied to the steel wire, and the coating amount had a great influence.

First, regarding the components of the steel wire, by containing a predetermined amount of C, Si and Mn and Ca, a short circuit at the time of welding and a reduction in the feed resistance of the welding wire are achieved. . As a result, the stability of the welding wire feeding can be maintained even if the welding wire feeding speed is increased, so that a stable arc can be obtained. Furthermore, when performing gas shielded arc welding with a high welding current of 300 A or more, the temperature of the tip of the power feed tip exceeds 500 ° C, so the lubricating oil and ester lubricants that have been known in the past can be heated to high temperatures. Decomposes upon exposure. Therefore, these lubricating oils and ester lubricants cannot maintain the lubricity at high temperatures. Therefore, by applying a solid lubricant containing an inorganic substance that is stable against heat, that is, a MoS ₂ , K compound, the feedability of the welding wire can be improved even if the temperature of the welding wire rises as the temperature of the feed tip rises. maintain. As a result, a highly stable arc can be obtained.

That is, the present invention is a steel wire for welding used in gas shield welding, wherein C: 0.20 mass% or less, Si: 0.25 to 2.5 mass%, Mn: 0.45 to 3.5 mass%, C
a: MoS on the surface of the steel wire containing 0.0020 mass% or less
A solid lubricant layer containing 15 to 70% by mass of one or more of ₂ and BN, 2% by mass or less of wax, 2 to 70% by mass of K compound, and 5 to 70% by mass of copper powder. Steel wire
A steel wire for gas shield arc welding, which has 0.2 to 1.0 g per 10 kg and has a lubricant layer consisting of a fatty acid ester and / or lubricating oil on the surface of a solid lubricant layer at 0.2 to 1.8 g per 10 kg of steel wire.

In the above invention, as a first preferred embodiment, the solid lubricant layer is one of MoS ₂ and BN.
15 to 70% by weight of one or more kinds, 2% by weight of wax
Below, K compound is 2 to 70% by mass, copper powder is 5 to 70% by mass,
Graphite: It is preferable to contain 5 to 20% by mass. In a second preferred embodiment, the K compound is preferably potassium stearate.

As a third preferred embodiment, the actual measurement of steel wire
Surface area S_o(Mm²) And theoretical surface area S _a(Mm²) And
The actual surface area ratio S calculated from the following equation (1) is 0.01 to 3.
It is preferable to satisfy the range of 0%.     S = 100 x (S_o-S_a) / S_a                    ... (1) S: Actual surface area ratio (%) S_o: Measured surface area of steel wire (mm²) S_a: Theoretical surface area of steel wire (mm²) As a fourth preferred aspect, the average thickness is
 It is preferable to form a Cu plating layer having a thickness of 0.5 μm or more.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION First, the reasons for limiting the components of the steel wire which is the material of the welding wire of the present invention will be explained. C: 0.20% by mass or less C is an important component for ensuring the strength of the weld metal, but it has the action of lowering the viscosity of the molten metal and improving the fluidity. However, if the C content exceeds 0.20 mass%, the behavior of the molten metal becomes unstable during welding,
A large amount of spatter is generated. Moreover, an unstable short circuit phenomenon occurs, which hinders the feedability of the welding wire. Therefore,
C was limited to 0.20 mass% or less. In order to secure the strength of the weld metal, the lower limit of the C content is preferably 0.01% by mass.

Si: 0.25 to 2.5 mass% Si has a deoxidizing action and is an essential component for deoxidizing the weld metal. If the Si content is less than 0.25% by mass, the molten metal sways during welding and a large amount of spatter occurs. Moreover, an unstable short circuit phenomenon occurs, which hinders the feedability of the welding wire. On the other hand, if it exceeds 2.5% by mass, the toughness of the weld metal decreases. Therefore, Si must satisfy the range of 0.25 to 2.5 mass%.

Mn: 0.45 to 3.5 mass% Mn has a deoxidizing action like Si and is an essential component for deoxidizing the weld metal. If the Mn content is less than 0.45% by mass, the molten metal fluctuates during welding and not only a large amount of spatter occurs, but also deoxidation of the molten metal is insufficient and blow defects occur in the weld metal. . Moreover, an unstable short circuit phenomenon occurs, which hinders the feedability of the welding wire.
On the other hand, if it exceeds 3.5% by mass, the toughness of the weld metal will decrease. Therefore, Mn must satisfy the range of 0.45 to 3.5 mass%.

Ca: 0.0020% by mass or less Ca is mixed in the steel wire as an impurity in the steel making process, the casting process or the wire drawing process. Ca content of 0.0020 mass%
If it exceeds, the arc becomes unstable during welding,
A large amount of spatter is generated. Moreover, an unstable short circuit phenomenon occurs, which hinders the feedability of the welding wire. Therefore,
Ca was limited to 0.0020 mass% or less.

Further, in the present invention, the components of the steel wire are, in addition to the above-mentioned composition, P: 0.003 to 0.050 mass%, S:
0.050 mass% or less, K: 0.0001 to 0.0150 mass% and T
It is preferable to contain i: 0.30 mass% or less. The reason will be described. P: 0.003 to 0.050 mass% P is an element mixed in the steel wire as an impurity in the steel making process and the casting process, but also has an effect of smoothing the bead shape. If the P content is less than 0.003% by mass, the effect of smoothing the bead shape cannot be obtained. On the other hand, if it exceeds 0.050 mass%, the viscosity of the molten metal is lowered during welding, the arc becomes unstable, and small droplets increase. Therefore, it is preferable that P satisfies the range of 0.003 to 0.050% by mass.

S: 0.050% by mass or less S has the effect of lowering the viscosity of the molten metal, assisting the detachment of droplets suspended at the tip of the welding wire, and stabilizing the arc. If the S content exceeds 0.050 mass%, the viscosity of the molten metal is lowered during welding, the arc becomes unstable, and small droplets increase. Therefore, S is 0.050
It is preferably not more than mass%. Note that S also has the effect of smoothing the bead shape. In order to make the bead shape smooth, it is preferable to add S in an amount of 0.003 mass% or more.

K: 0.0001 to 0.0150 mass% K has the effect of expanding (or softening) the arc, facilitating the transfer of droplets, and refining the droplets to suppress fluctuations in the feed resistance of the welding wire. Have. K content is 0.
If it is less than 0001% by mass, these effects cannot be obtained. On the other hand, if it exceeds 0.0150 mass%, the arc becomes long during welding, and the droplets suspended at the tip of the welding wire become unstable and a large amount of spatter occurs. Therefore,
It is preferable that K satisfies the range of 0.0001 to 0.0150% by mass. More preferably, it is 0.0003 to 0.0030 mass%.
Since K has a low boiling point of about 760 ° C., if K is added at the stage of melting the steel material, the yield is extremely low. Therefore, at the stage of manufacturing a steel wire, K can be stably contained in the steel wire by applying a potassium salt solution to the surface of the steel wire and performing annealing.

Ti: 0.30% by mass or less Ti is a component that acts as a deoxidizing material and further increases the strength of the weld metal. However, if the Ti content exceeds 0.30 mass%, not only coarse droplets are generated during welding and large-sized spatters are generated, but also the toughness of the weld metal is significantly reduced. Therefore, Ti is preferably 0.30 mass% or less. In order to increase the strength of the weld metal,
It is preferable to add Ti in an amount of 0.03 mass% or more.

Further, in the present invention, in addition to the above composition, the components of the steel wire are Cr: 3.0 mass% or less, Ni: 3.0 mass%.
Hereinafter, it is preferable to contain one or more of Mo: 1.5 mass% or less, Cu: 3.0 mass% or less, and B: 0.005 mass% or less. That is, Cr, Ni, Mo, Cu and B are components that increase the strength of the weld metal and improve the weather resistance,
It may be added if necessary. However, it is not necessary to set a lower limit because each component exhibits these effects with a small amount of addition. However, if added excessively, the toughness of the weld metal will be reduced, so when adding these components,
Cr: 3.0 mass% or less, Ni: 3.0 mass% or less, Mo: 1.5 mass% or less, Cu: 3.0 mass% or less, B: 0.005 mass% or less is preferable.

Further, in the present invention, it is preferable to add one or more of Zr, Nb and V as the components of the steel wire in addition to the above composition. That is, Zr, Nb, and V are all components that improve the strength and toughness of the weld metal and improve the stability of the arc, and may be added as necessary. However, it is not necessary to set a lower limit because each component exhibits these effects with a small amount of addition. However, if added excessively, the toughness of the weld metal will be deteriorated. Therefore, when one of these components is added, the addition amount is preferably 0.55% by mass or less, and when two or more are added. In addition, the total addition amount is preferably 0.55% by mass or less.

Furthermore, in the present invention, the components of the steel wire are
In addition to the above composition, it is preferable to add Al: 0.50 mass% or less. That is, Al is a component that acts as a deoxidizer for the weld metal and improves the stability of the arc when performing horizontal welding, and may be added as necessary. However, if added in excess of 0.50% by mass, toughness is reduced. Therefore, when Al is added, the addition amount is preferably 0.50 mass% or less.

The balance other than the components of the steel wire described above is Fe and inevitable impurities. For example, O or N is a typical unavoidable impurity, and it is inevitably mixed at the stage of melting a steel material or at the stage of manufacturing a steel wire. O is 0.020
It is preferable to reduce the content of N to 0.010% by mass or less and N to 0.010% by mass or less. O, in particular, has the effect of subdividing the migration form of droplets, so 0.0020 to 0.0080 mass% is more preferable.

Next, a method for manufacturing the welding wire of the present invention will be described. Molten steel having the above composition is melted by using a converter or an electric furnace. The method for producing molten steel is not limited to a specific technique, and a technique known in the related art is used. Then, the obtained molten steel is manufactured into a steel material (such as a billet) by a continuous casting method, an ingot making method, or the like. After heating this steel material, hot rolling is performed, and then dry cold rolling (that is, wire drawing) is performed to manufacture a steel element wire. The operating conditions of hot rolling and cold rolling are not limited to specific conditions, and may be any conditions as long as the steel wire having a desired size and shape is manufactured.

Further, the steel wire is annealed-pickled-copper plated-
The steps of wire drawing-lubricant application are sequentially performed to obtain a predetermined product, that is, a welding wire. Before the annealing, it is preferable to apply the potassium salt solution on the surface of the steel wire in advance. As the potassium salt solution, it is preferable to use an aqueous solution of 3 potassium citrate, an aqueous solution of potassium carbonate, an aqueous solution of potassium hydroxide or the like. The potassium salt concentration after coating is preferably 0.5 to 3.0% by volume in terms of K value.

By thus annealing the steel wire coated with the potassium salt solution on the surface, K is stably retained in the internal oxide layer produced. On the other hand, in the method of holding K in the Cu plating layer or the method of simply applying it, problems such as Cu plating and discoloration of the steel wire tend to occur.
Moreover, since it is thermally unstable, the effect of reducing the spatter by K becomes small.

The annealing is carried out for the purpose of softening the steel wire and imparting K, and in the temperature range of 650 to 950 ° C.
And it is preferable to carry out in a nitrogen gas atmosphere containing water vapor. That is, when the annealing temperature is lower than 650 ° C, the progress of internal oxidation is slowed down. On the other hand, if the temperature exceeds 950 ° C, the progress of internal oxidation is too fast, and it becomes difficult to adjust the internal oxidation amount. From the viewpoint of promoting internal oxidation, the annealing atmosphere preferably has a dew point of 0 ° C. or less and an oxygen concentration of 200 ppm by volume or less. By annealing the steel wire coated with the potassium salt solution on the surface in such an annealing atmosphere, oxidation progresses from the surface and the surface layer portion is internally oxidized. K is reliably retained in this internal oxide layer.

The annealing time and the annealing temperature are preferably set according to the application conditions of the potassium salt solution (eg, application amount, potassium salt concentration, diameter of steel wire, etc.).
Further, the K content in the steel wire is 0.0003 to 0.0030 mass%, O
It is preferable to set the annealing time and the annealing temperature so that the content is 0.0020 to 0.0080 mass%. The steel wire thus annealed is, after being pickled,
It is preferable to apply Cu plating to the surface. The thickness of the Cu plating layer is preferably 0.5 μm or more.

That is, when continuous welding is carried out at a high current, the feeding of the welding wire is likely to be hindered due to defective power supply. On the other hand, by setting the thickness of the Cu plating layer to 0.5 μm or more, it is possible to prevent instability of the feeding of the welding wire due to a defective power supply. More preferably, it is 0.8 μm or more. By thus thickening the Cu plating, the effect of reducing the wear of the power feeding chip can also be obtained.

Further, the actual surface area ratio S of the steel wire is 0.01 to 3.
It is preferable to satisfy the range of 00%. Actual surface area ratio S
Is a value calculated by the following equation (1). _{S = 100 × (S o -S} a) / S a ··· (1) S: actual surface area ratio (%) S _o: Found surface area of the steel element wires (mm ²⁾ S _a: Theoretical surface area of the steel wires (Mm ² ) Here, the surface area means a surface area in a state before applying a lubricant described later. Therefore, it refers to the surface area of the steel wire that is the material of the welding wire. However, when the steel wire is Cu-plated, it is the surface area of the steel wire including the Cu-plated layer.

Further, the actually measured surface area S _o (mm ² ) of the steel wire refers to the area occupied by the steel wire on a 400 times observation surface by a scanning electron microscope (so-called SEM). Further, the theoretical surface area S _a (mm ² ) of the steel wire refers to the surface area calculated by using the steel wire as a cylinder on the same observation surface. Therefore, the actual surface area ratio S of the steel wire represents the size of the unevenness on the surface of the steel wire before applying the lubricant. That is, as the actual surface area ratio S increases, the unevenness increases, and the area where the lubricant adheres increases. Conversely, when the actual surface area ratio S decreases, it means that the area where the lubricant adheres decreases. In order to stabilize power supply during welding, it is preferable to smooth the surface of the steel wire (that is, reduce the actual surface area ratio S), and the actual surface area ratio S should be 3.00% or less. preferable. on the other hand,
If the actual surface area ratio S is less than 0.01%, when the lubricant is applied to the surface of the steel wire, the amount of the adhered material tends to be insufficient. If the lubricant is applied excessively, it is possible to make the lubricant adhere to the surface of the steel wire, but the welding is slipped by the feed roller, which makes the feeding unstable. Therefore, it is preferable that the actual surface area ratio S of the steel wire satisfies the range of 0.01 to 3.00%.

Incidentally, in the examples described later, as a result of investigating the wire number 6 using a scanning electron microscope, as shown in FIG. 1, the actual surface area ratio S of the wire number 6 is
It is 1.24%. The actual surface area ratio S is the SRI _{r in} FIG.
Calculated by subtracting 100 from the value. By using the process of drawing and coating the steel wire thus Cu-plated, MoS ₂ or BN: 15 to 70% by mass or MoS ₂ and BN: 15 to 70% by mass in total, wax:
A solid lubricant consisting of 2 mass% or less, K compound: 2 to 70 mass%, and copper powder generated in the wire drawing step: 5 to 70 mass% is formed. This solid lubricant layer is 0.2 to 1.0 per 10 kg of steel wire.
g.

If continuous welding is performed for 1 minute or more at a welding current of 400 A, the temperature of the power feed tip becomes 500 ° C. or more. At such a high temperature, the fatty acid ester and the lubricating oil decompose, so that the lubricity cannot be maintained. As a result of studying various lubricants, the inventors have found that MoS ₂ , BN, K compounds, and copper powder are effective for maintaining lubricity even at high temperatures. However, MoS ₂ or BN: 15 to 70 mass% or MoS ₂ and BN: 15 to 70 mass% in total, wax:
It is necessary to satisfy the ranges of 2 mass% or less, K compound: 2 to 70 mass%, and copper powder generated in the wire drawing step: 5 to 70 mass%. Outside this range, the lubricity cannot be maintained during high current gas shielded arc welding, and the feed rate of the welding wire fluctuates significantly, resulting in unstable feed.

The content of MoS ₂ and BN is preferably
The amount of MoS ₂ or BN is 15 to 50% by mass, or the total amount of MoS ₂ and BN is 15 to 50% by mass. Further, if graphite is contained in an amount of 5 to 20% by mass, the lubricity of the high temperature power feed chip is improved, which is more preferable. Further, it is preferable to use potassium stearate as the K compound because the high temperature lubricity is improved.

On the other hand, the copper powder generated in the wire drawing process after Cu plating has an effect of reducing friction in the conduit tube. When the amount of copper powder in the solid lubricant layer is less than 5% by mass, there is no effect of reducing the resistance when feeding the welding wire. If the amount of copper powder in the solid lubricant layer exceeds 70% by mass, seizure will occur in the power feed tip during welding, and the feeding of the welding wire will stop momentarily. As a result, the arc becomes unstable. Therefore, the content of the copper powder in the solid lubricant layer is 5 to
It must be 70% by mass.

The wax as used in the present invention refers to a wax which is solid at room temperature among fatty acid esters, cotton waxes, animal and plant solid waxes, synthetic waxes and petroleum waxes. Wax has the effect of improving wire drawability and lubricity at room temperature, but 2% by mass
If added over the range, arc instability hinders feedability. Therefore, the content of wax in the solid lubricant layer is set to 2% by mass or less.

As described above, K stabilizes the arc,
It has the function of stabilizing the feeding of the welding wire. As the K compound, potassium stearate is preferable. If the K compound content is less than 2% by mass, the effect of stabilizing the feed due to the arc stabilization is not obtained, and if it is added in excess of 70% by mass, the effect of improving the feeding property by the solid lubricant is lost. Therefore, the content of the K compound in the solid lubricant layer is set to 2 to 70% by mass.

Further, the solid lubricant layer adhered to the steel element wire was 10 kg.
If the amount is less than 0.2 g, the effect of reducing the resistance when feeding the welding wire cannot be obtained. On the other hand, per 10 kg of steel wire
If it exceeds 1.0 g, the solid lubricant adheres and accumulates on the inner surface of the power feed tip, which hinders the feeding of the welding wire. Therefore,
The amount of solid lubricant adhered must be within the range of 0.2 to 1.0 g per 10 kg of steel wire.

Further, in order to reduce the feeding resistance of the welding wire during welding and stabilize the feeding, the surface of this solid lubricant layer is fatty acid ester or lubrication liquid at room temperature (25 ° C.). Apply oil. Alternatively, a mixture of fatty acid ester and lubricating oil may be applied. In this way, a lubricant layer made of fatty acid ester and / or lubricating oil is formed. If this lubricant layer is less than 0.2 g per 10 kg of steel wire, the effect of reducing the resistance when feeding the welding wire cannot be obtained. On the other hand, if the weight exceeds 1.8 g per 10 kg of steel wire, the welding wire slips on the feeding roller during welding, and the feeding speed fluctuates remarkably, resulting in unstable feeding. Therefore, the lubricant layer per 10 kg of steel wire
It is necessary to satisfy the range of 0.2 to 1.8 g.

By thus forming the lubricant layer by applying the fatty acid ester and / or the lubricating oil, it is possible to obtain the effect of preventing discoloration and deterioration of the surface of the steel wire due to MoS ₂ or K compound.

[0042]

Example A billet produced by continuous casting was hot rolled into a wire rod having a diameter of 5.6 to 7.0 mm. Then, by cold rolling (that is, wire drawing), a steel wire having a diameter of 2.0 to 2.8 mm was made, and further, 30 to 50 g of a 2 to 30% by volume aqueous solution of tripotassium citrate was applied per 1 kg of the steel wire.

Thereafter, the steel wire was heated to a dew point of −2 ° C. or below,
Oxygen concentration less than 200 volume ppm, carbon dioxide concentration 0.1 volume%
It was annealed in the following nitrogen atmosphere. Annealing temperature is 760-950
By adjusting the annealing temperature and the annealing time according to the diameter of the steel wire and the potassium salt concentration as the range of ℃, the progress of internal oxidation is adjusted and the K content and O content of the steel wire are adjusted. did.

After annealing in this way, the surface of the steel wire is plated with Cu, and the wire is cold drawn (wet wire drawing).
Then, a welding wire having a diameter of 1.2 mm was manufactured. With respect to some of the welding wires, a solid lubricant containing MoS ₂ and a K compound was applied by wire drawing and wire drawing, so that a solid lubricant capable of maintaining lubricity at high temperature was attached. The amount of solid lubricant adhered was adjusted by selecting the die schedule and die shape.

The components of the steel wire of the obtained welding wire, the actual surface area ratio S, and the Cu plating thickness are as shown in Table 1.

[0046]

[Table 1]

Steel plates (thickness 19
mm) was subjected to bead-on welding for 2 minutes, and the feed resistance was measured as an index for evaluating the feedability of the welding wire. Here, the target value of the feed resistance of the welding wire is set to 55N or less, the feed resistance of 35N or less is good (○), the one exceeding 35N to 55N or less is acceptable (△), the one exceeding 55N is not acceptable ( X) was evaluated.

The apparatus used for bead-on welding is shown in FIG. In FIG. 2, reference numeral 1 is a welding power source, 2 is a welding torch, 3 is a welding wire, 3a is a conduit tube, 4 is a feed roller, and 5 is a load cell. The feeding resistance of the welding wire was measured by the load cell 5. Next, bead-on welding was performed on the upper surface of the steel plate (thickness: 19 mm) for 1 minute, spatter was collected using a Cu collection jig, and the spatter generation amount was measured. Here, the target value of the amount of spatter is
At 3.0g / min or less, spatter generation rate is 2.0g / min
The following are good (○), exceeding 2.0 g / min to 3.0 g / m
The following items were evaluated as acceptable (△) and those exceeding 3.0 g / min as unacceptable (×).

Next, while rotating a steel pipe having a diameter of 800 mm (thickness: 25 mm), continuous welding was performed for 30 minutes on the outer region of the steel pipe.
After the continuous welding is completed, the inner diameter of the tip of the power feed tip is measured as an index for evaluating the wear of the power feed tip, and the maximum value D _max (mm) and the minimum value D _min (mm) are used to perform the following (2).
The ellipticity (%) was calculated from the formula. Ellipticity (%) = 100 x ( _{Dmax- Dmin} ) / _Dmin (2) _Dmax : maximum inner diameter (mm) _Dmin : minimum inner diameter (mm) The target value of is less than 5%, the ellipticity is less than 2% is good (○), more than 2% to less than 5% is acceptable (△), and more than 5% is not acceptable (x). evaluated.

Tables 2 and 3 show the evaluation of the feedability of the welding wire, the evaluation of the amount of spatter, and the evaluation of the wear of the power feed tip. The amounts of lubricant applied and the amounts of solid lubricant applied to each welding wire used are shown in Tables 2 and 3.

[0051]

[Table 2]

[0052]

[Table 3]

The welding conditions used for these evaluations are as shown in Table 4.

[0054]

[Table 4]

In each of Inventive Examples 1 to 27 shown in Table 2, the evaluation of the feedability of the welding wire, the evaluation of the amount of spatter generation, and the evaluation of the wear of the power supply tip were good or acceptable. On the other hand, in Comparative Examples 1 to 13 shown in Table 3, the evaluation of the feedability of the welding wire, the evaluation of the amount of spatter generation, and the evaluation of the wear of the power supply tip were all impossible.

[0056]

EFFECTS OF THE INVENTION By using the welding wire of the present invention, when gas shielded arc welding is performed continuously with a large welding current, the welding wire is excellent in feedability and arc stability, and is of good quality. Welded joints are obtained. In addition, the amount of spatter generation can be reduced, and the stability of power supply is also excellent,
It is also possible to reduce wear of the power supply chip.

[Brief description of drawings]

FIG. 1 is a graph showing the results of measuring the surface roughness of steel strands with a scanning electron microscope.

FIG. 2 is a layout diagram schematically showing an apparatus used for evaluating a welding wire.

[Explanation of symbols]

1 welding power source 2 welding torch 3 welding wire 3a conduit tube 4 feeding rollers 5 load cell

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuhiko Muramoto             1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama             Shi) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor Yoshitaka Sasa             2-17-4 Kuramae, Taito-ku, Tokyo             Inside the contact rod company F-term (reference) 4E084 CA24 CA25 CA38 DA33 GA02

Claims (5)

[Claims] 1. A welding steel wire used in gas shield welding, wherein C: 0.20 mass% or less, Si: 0.25 to 2.5.
15% to 70% by mass of one or more kinds of MoS ₂ and BN and 2% of wax on the surface of the steel wire containing less than 0.4% by mass, Mn: 0.45 to 3.5% by mass, and Ca: 0.0020% by mass or less. Mass% or less, K compound 2 to 70 mass%, copper powder 5 to 70 mass%
The solid lubricant layer containing 0.2 to 1.
0 g, and a lubricant layer made of fatty acid ester and / or lubricating oil on the surface of the solid lubricant layer
Steel wire for gas shielded arc welding, characterized in that it has 0.2 to 1.8 g per unit. 2. The solid lubricant layer comprises MoS ₂ and BN.
15 to 70% by mass of one or more of the above, 2% by mass or less of wax, 2 to 70% by mass of K compound, and 5 to 5% of copper powder.
70 mass% and graphite: 5-20 mass% is contained, The steel wire for gas shield arc welding of Claim 1 characterized by the above-mentioned. 3. The steel wire for gas shielded arc welding according to claim 1, wherein the K compound is potassium stearate. 4. The measured surface area S of the steel wire_o(Mm²)When
Theoretical surface area S_a(Mm ²) And are calculated from the following equation (1).
The actual surface area ratio S to be output satisfies the range of 0.01 to 3.0%.
Gas according to claim 1, 2 or 3, characterized in that
Steel wire for shield arc welding.     S = 100 x (S_o-S_a) / S_a                    ... (1) S: Actual surface area ratio (%) S_o: Measured surface area of steel wire (mm²) S_a: Theoretical surface area of steel wire (mm²) 5. The surface of the steel wire has an average thickness of 0.5 μm.
The above-mentioned Cu plating layer is formed, The steel wire for gas shield arc welding according to claim 1, 2, 3 or 4.