JP2003225792A - Wire for carbon dioxide gas shielded arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire for welding which not only reduces spatters, but also enables excellent bead shape on carbon dioxide gas shielding arc welding using a shielding gas essentially consisting of CO<SB>2</SB>. <P>SOLUTION: The wire for straight polarity carbon dioxide gas shielded arc welding contains, by mass, ≤0.20% C, 0.25 to 2.5% Si, 0.45 to 3.5% Mn, 0.015 to 0.100% rare earth metals, 0.003 to 0.05% P and 0.015 to 0.05% S. <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 welding wire used for positive polarity carbon dioxide shielded arc welding, and more particularly, when the welding wire is used on the positive electrode side (that is, the negative electrode side), the generation of spatter is small, and Carbon dioxide shielded arc welding wire (hereinafter,
Welding wire).

[0002]

2. Description of the Related Art In gas shielded arc welding using various shield gases, inexpensive carbon dioxide gas (that is, C
Gas shielded arc welding (hereinafter referred to as carbon dioxide shielded arc welding) using a shield gas containing O ₂ ) as a main component is the most popular welding method, and is a highly efficient welding method. Widely used in.

With the rapid progress of automatic welding technology in recent years, the carbon dioxide gas shielded arc welding method has been used in various fields such as shipbuilding, construction, bridges, automobiles and construction machinery. For example, in the fields of shipbuilding, construction, bridges, etc., it is used for high current multi-layer welding of thick plates, and in the fields of automobiles, construction machinery, etc., it is used for fillet welding of thin plates. On the other hand, Ar- (5
Gas shielded arc welding (so-called MAG welding), which uses a mixed gas consisting of 25% by volume) CO ₂ as a shielding gas, is excellent in bead shape and generates less spatter, and therefore is used in fields requiring high quality welding. It is used. However, the cost of Ar is as _high as five times that of CO ₂ , and therefore, in actual welding, a shield gas containing CO ₂ as a main component (that is, CO ₂ : 40% by volume or more) is often used in actual welding work.

In carbon dioxide shielded arc welding using a shielding gas containing CO ₂ as a main component, coarse droplets are suspended at the tip of the welding wire and sway under the influence of the arc. Is likely to occur. As a result, there is a problem that a large amount of spatter is generated.
Therefore, Japanese Patent Laid-Open No. 6-218574 discloses a method of reducing spatter by adding potassium. However, this technique is not sufficient in suppressing the generation of spatter in carbon dioxide shield arc welding.

Further, JP-A-7-47473 and JP-A-7-2902
Japanese Patent Laid-Open No. 41-41 proposes a method of generating one pulse within a transition time of one droplet to reduce spatter. In these techniques, in MAG welding using a mixed gas consisting of Ar- (5 to 25% by volume) CO ₂ as a shield gas, the time required for 1 droplet formation is 1-2 ms and the droplet transfer is stable. Therefore, the effect of reducing spatter is exhibited. However, in carbon dioxide shielded arc welding using a shield gas containing CO ₂ as a main component, 10 to 20 droplets are formed in 1 to 2 ms, so that the droplet becomes unstable, and 1 droplet is transferred within 1 droplet transfer time. It is difficult to generate a pulse. As a result, 1
Droplets that could not be transferred during the pulse short-circuit the steel plate and the welding wire, increasing the generation of spatter.

[0006]

As described above, CO
_In carbon dioxide shielded arc welding using a shield gas containing ₂ as a main component (that is, CO ₂ : 40 vol% or more),
There is a problem that the coarse droplets short-circuit the steel plate and the welding wire, increasing the generation of spatter. The present invention is
The present invention has been made in view of the above circumstances, and an object thereof is to provide a welding wire that not only reduces spatter when performing carbon dioxide gas shielded arc welding but also obtains an excellent bead shape.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that in carbon dioxide shielded arc welding using a shield gas containing CO ₂ as a main component (that is, CO ₂ : 40 vol% or more),
We have diligently studied reduction of spatter and improvement of bead shape. As a result, the following findings were obtained. (1) By performing positive polarity welding with the welding wire as a negative electrode, droplets are coarse, but stable transfer is possible. (2) Addition of a rare earth element (hereinafter referred to as REM) to the welding wire prevents arc breakage in the low voltage region and enables stable droplet transfer. (3) By adding REM to the welding wire, the penetration can be secured and the bead can be smoothed. (4) Stable weldability can be obtained by adding Si, Mn, Ti, Zr, Al, and Cr to the welding wire.

The present invention has been made based on these findings. That is, the present invention is a welding wire used for positive polarity carbon dioxide shielded arc welding, wherein C
0.20 mass% or less, Si 0.25 to 2.5 mass%, Mn 0.45 to 3.
5 mass%, REM 0.015 to 0.100 mass%, P 0.002 to
A carbon dioxide shielded arc welding wire containing 0.05% by mass and 0.002 to 0.05% by mass of S.

In the above invention, as a preferred embodiment, in addition to the above composition, Ti, Zr, Al and Cr are contained, and from the contents of Si, Mn, REM, Ti, Zr and Al, the following (1 It is preferable that the D value calculated by the equation) satisfies the range of 1.4 to 3.0. D = ([Si] / 2) + ([Mn] / 3) + [Ti] + [Zr] + [Al] + (10 × [REM]) (1) [Si]: Welding wire Si content (mass%) [Mn]: Mn content of the welding wire (mass%) [Ti]: Ti content of the welding wire (mass%) [Zr]: Zr content of the welding wire ( Mass%) [Al]: Al content of the welding wire (mass%) [REM]: REM content of the welding wire (mass%)

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, the reasons for limiting the composition of the carbon dioxide shielded arc welding wire of the present invention will be described. C: 0.20% by mass or less C is an important element for ensuring the strength of the weld metal, and has the effect of lowering the viscosity of the molten steel and improving the fluidity. When the C content exceeds 0.20 mass%, not only the behavior of the droplets and the molten pool becomes unstable, but also the toughness of the weld metal deteriorates. Therefore, the C content is limited to 0.20 mass% or less. In addition, preferably 0.01 to 0.10 mass%
Is.

Si: 0.25 to 2.5 mass% Si has a deoxidizing action and is an essential element for deoxidizing the weld metal. Further, it has the effect of suppressing the spread of the arc in positive polarity welding and increasing the number of times droplets are transferred. If the Si content is less than 0.25 mass%, such an effect cannot be obtained. On the other hand, if it exceeds 2.5 mass%, the arc becomes unstable and spatter increases. Therefore, Si is 0.
It is necessary to satisfy the range of 25 to 2.5 mass%.

Mn: 0.45 to 3.5 mass% Mn has a deoxidizing action like Si and is an essential element for deoxidizing the weld metal. If the Mn content is less than 0.45% by mass, deoxidation is insufficient and blow defects occur in the weld metal. 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%.

REM: 0.015 to 0.100 mass% REM is an element effective for refining inclusions in the steel making process and casting process of the material for the welding wire and improving the toughness of the weld metal during welding. Particularly in the positive polarity carbon dioxide shield arc welding, the transfer of droplets in the low voltage region is stabilized. If the REM content is less than 0.015% by mass, such an effect cannot be obtained. On the other hand, if it exceeds 0.100 mass%, the stabilization of the arc is hindered, the melting rate of the welding wire is lowered, and the risk of burn-through in thin plate welding is increased. Therefore, the REM must be within the range of 0.015 to 0.100 mass%. In addition, preferably 0.020 to 0.04
It is 0% by mass.

P: 0.002 to 0.05% by mass P is an element which has the effects of lowering the melting point of steel and improving the electrical resistivity. Therefore, since the melting efficiency is improved, the arc is stabilized in the carbon dioxide shield arc welding having the positive polarity. If the P content is less than 0.002% by mass, such an effect cannot be obtained. On the other hand, if it exceeds 0.05% by mass, the viscosity of molten steel decreases in positive polarity carbon dioxide shielded arc welding, and the arc becomes unstable,
Small particle spatter increases. Moreover, the risk of hot cracking of the weld metal increases. Therefore, P is 0.002
It is necessary to satisfy the range of up to 0.050 mass%.

S: 0.002 to 0.05% by mass S reduces the viscosity of molten steel so that the droplets suspended at the tip of the welding wire can be easily separated, and stabilizes the arc in positive polarity carbon dioxide shielded arc welding. It is an element that has the effect of causing. Further, S also has the effect of smoothing the beads and suppressing burn-through of the upper plate by reducing the viscosity of the molten steel. If the S content is less than 0.002 mass%, such an effect cannot be obtained. On the other hand, if it exceeds 0.05 mass%, the spatter of small particles increases and the toughness of the weld metal decreases. Therefore, it is preferable that S satisfies the range of 0.002 to 0.05 mass%. More preferably
It is 0.015 to 0.03 mass%.

Ti, Zr, Al: D calculated by the following equation (1)
A value of 1.4 to 3.0 Ti, Zr, and Al has the effect of reducing the O content in the weld metal by the deoxidizing effect and smoothing the bead shape. The smooth beat has the effect of suppressing the occurrence of welding defects due to the deviation of the target position of the welding wire. Therefore, Ti, Zr, and Al are added as needed.

When adding Ti, Zr, and Al, the following (1)
When the D value calculated by the formula is less than 1.4, convex and uneven beads are likely to be formed. On the other hand, when it exceeds 3.0,
Larger spatter increases. Therefore, it is preferable to add Ti, Zr and Al in the range where the D value calculated by the following equation (1) satisfies 1.4 to 3.0. D = ([Si] / 2) + ([Mn] / 3) + [Ti] + [Zr] + [Al] + (10 × [REM]) (1) [Si]: Welding wire Si content (mass%) [Mn]: Mn content of the welding wire (mass%) [Ti]: Ti content of the welding wire (mass%) [Zr]: Zr content of the welding wire ( Mass%) [Al]: Al content of the welding wire (mass%) [REM]: REM content of the welding wire (mass%) Note that Ti has a deoxidizing action and the strength of the weld metal. It is an element that enhances. If the Ti content is less than 0.01% by mass, such an effect cannot be obtained. On the other hand, if it exceeds 0.30% by mass, coarse droplets are generated and large-sized spatter increases. Therefore, if Ti is added, its content should be 0.01
It is even more preferable that the content be 0.30% by mass.

Zr is an element that improves the strength and toughness of the weld metal and enhances the stability of the arc. If the Zr content is less than 0.01% by mass, such an effect cannot be obtained. On the other hand, 0.30
If it exceeds the mass%, the toughness of the weld metal is lowered. Therefore, when Zr is added, its content is more preferably 0.01 to 0.30 mass%. Al is an element that improves the strength and toughness of the weld metal and enhances the stability of the arc. When the Al content is less than 0.01% by mass,
Such an effect cannot be obtained. On the other hand, when it exceeds 0.50 mass%, the toughness of the weld metal is deteriorated. Therefore, when Al is added, its content is more preferably 0.01 to 0.50% by mass.

In the present invention, in addition to these elements, the following elements can be added if necessary. Cr: 0.02 to 3.0 mass% Cr is an element that improves the strength of the weld metal and enhances the weather resistance. If the Cr content is less than 0.02 mass%, such an effect cannot be obtained. On the other hand, when it exceeds 3.0 mass%, the toughness of the weld metal is deteriorated. Therefore, when Cr is added, its content is more preferably 0.02 to 3.0 mass%.

Ni: 0.05 to 3.0% by mass, Mo: 0.05 to 1.5% by mass, Cu: 0.05 to 3.0% by mass, B: 0.0005 to 0.005% by mass Ni, Mo, Cu and B all have the strength of the weld metal. It is an element that improves the strength of the weld metal and enhances the weather resistance. If the contents of these elements are insufficient, such effects cannot be obtained. On the other hand, if added excessively, the toughness of the weld metal is reduced. Therefore, when adding Ni, Mo, Cu, B, Ni:
0.05 to 3.0 mass%, Mo: 0.05 to 1.5 mass%, Cu: 0.05 to
It is preferable to set 3.0 mass% and B: 0.0005 to 0.005 mass%.

Nb: 0.005 to 0.05 mass%, V: 0.005 to 0.
05 mass% Nb and V are both elements that improve the strength and toughness of the weld metal and enhance the stability of the arc. If the contents of these elements are insufficient, such effects cannot be obtained. on the other hand,
If added excessively, the toughness of the weld metal is lowered. Therefore, when Nb and V are added, it is preferable to set Nb: 0.005 to 0.05 mass% and V: 0.005 to 0.05 mass%.

The balance other than the above components is Fe and inevitable impurities. The unavoidable impurities are O:
0.020 mass% or less and N: 0.010 mass% or less are acceptable. O is unavoidably mixed in the welding wire material in the melting step or the welding wire drawing step, but it is effective in refining the droplet transfer pattern.
It is preferably adjusted to 0.0080 mass%. More preferably, it is 0.0020 mass% or more and less than 0.0080 mass%.

Next, a method of manufacturing the welding wire applied to the present invention will be described. Molten steel having the above composition is melted by a conventionally known method such as a converter or an electric furnace, and then a steel material (for example, billet) is manufactured by a continuous casting method or the like. This steel material is heated and then hot-rolled or cold-rolled (for example, dry wire drawing) to obtain a steel wire. Note that hot rolling and cold rolling may be performed by producing a steel wire having a predetermined size and shape, and therefore the setting conditions are not particularly limited.

Next, the steel wire is further subjected to the steps of annealing-pickling-Cu plating-drawing in order to obtain a product having a predetermined diameter (that is, a welding wire). In the positive polarity carbon dioxide shielded arc welding, the arc tends to become unstable due to poor power supply, as compared with the opposite polarity welding. However, by setting the Cu plating thickness to 0.6 μm or more, it is possible to prevent instability of the arc due to defective power supply. The Cu plating thickness is preferably 0.8 μm or more. Also, like this
The use of thick Cu plating also has the effect of reducing wear on the power supply chip. On the other hand, if the Cu content, including Cu in the welding wire, exceeds 3.0% by mass, the toughness of the weld metal decreases significantly. Therefore, the Cu plating thickness should be 0.6 μm or more, and should include Cu in the welding wire.
It is preferable to adjust the Cu plating thickness so that the Cu content is 3.0% by mass or less. The Cu plating thickness is more preferably 0.8 μm or more.

Further, in order to improve the stability of power supply and reduce the generation of spatter, it is important to set the flatness (that is, the actual surface area / theoretical surface area) of the welding wire surface to less than 1.01. The flatness of the welding wire surface can be maintained in the range of less than 1.01 by strictly controlling the dies in the wire drawing process. The lubricating oil that is applied to improve the feedability of the welding wire is the welding wire 10
It is preferably 0.35 to 1.7 g or less per kg. The feedability of the welding wire is important when performing robot welding.

In order to improve the stability of power supply, impurities adhering to the surface of the welding wire are added per 10 kg of the welding wire.
It is preferable to keep it to 0.01 g or less.

[0027]

[Example] After hot-rolling a steel material (that is, a billet) manufactured by continuous casting into a wire having a diameter of 5.5 to 7.0 mm,
Cold rolled (ie wire drawing) and diameter 2.0 ~ 2.8m
m steel wire was used. An aqueous solution of tripotassium citrate having a concentration of 2 to 30 mass% was applied to this steel wire. The coating amount was 30 to 50 g per 1 kg of steel wire.

Next, the steel wire is placed under N having a dew point of −2 ° C. or less.₂Atmosphere
Qi (O₂: 200 volume ppm or less, CO ₂: 0.1 volume% or less
Annealed below). The annealing temperature was 750 to 950 ° C. this
When the diameter of the steel wire and the concentration of the aqueous solution of 3 potassium citrate
Temperature, annealing temperature and annealing time to adjust the inside of the steel wire.
Adjust the O content and K content by oxidation to the specified range.
It was

After the annealing, the steel wire was pickled and then Cu
It was plated. Next, cold wire drawing is applied to the diameter
A welding wire of 0.9 to 1.6 mm was used. Lubricating oil was applied to the surface of the welding wire (application amount: 0.4 to 1.7 g per 10 kg of the welding wire). With the composition of the obtained welding wire
The Cu plating thickness is shown in Table 1.

[0030]

[Table 1]

A carbon dioxide shield arc welding test was carried out using these welding wires, and the amount of spatter generated, the bead shape and the dilution rate (ie, penetration) were evaluated.
The results are shown in Table 2.

[0032]

[Table 2]

(A) Spatter generation amount Bead-on-welding was performed on a steel plate having a thickness of 3.2 mm, and a sputtering jig made of Cu was used to collect spatter having a diameter of 0.5 mm or more to investigate the spatter generation amount. Spatter generation amount is welding amount 100
The evaluation was made such that 0.20 g or less per g was good (◯), more than 0.2 g to 0.3 g or less was acceptable (△), and more than 0.3 g was not acceptable (x). The welding time was 1 min. (b) Bead shape Weld beads on 3.2 mm thick steel plate, and after welding,
The cross section of the weld bead was observed, and the bead width W (mm) and the bead height H (mm) were measured. As a result, it was evaluated that the H / W was 0.5 or less as good (◯), 0.5 to 0.7 or less was acceptable (Δ), and 0.7 or more was not acceptable (x). (c) Dilution rate (penetration) Bead-on welding is performed on a steel plate with a thickness of 3.2 mm.
The cross section of the weld bead was observed, and the surplus area G (mm ² ) and the penetration area P (mm ² ) were measured. As a result, P / (G
When + P) was 0.4 or more, it was evaluated as good (◯), 0.3 g or more and less than 0.4 g was evaluated as acceptable (△), and less than 0.3 was evaluated as unacceptable (×).

The welding conditions common to the welding tests (a) to (c) are shown in Table 3.

[0035]

[Table 3]

As is clear from Table 2, in the inventive examples, the spatter generation rate was as small as 0.3 g / min or less, the spatter reduction effect was exhibited, and the beads having a good shape were obtained. In particular, by adding REM and setting the D value to 1.4 or more, the effect of reducing spatter and the effect of improving the bead shape were more significantly exhibited. On the other hand, in the comparative example in which the components are out of the range of the present invention, the spatter generation amount is large (that is, 0.7 g
/ Min) and the bead shape deteriorated.

[0037]

EFFECTS OF THE INVENTION According to the present invention, in positive polarity carbon dioxide shielded arc welding, since arc stability is excellent and extremely low spatter and penetration can be secured, stable welding from thin steel plate to thick steel plate is possible. Become. In addition, burn-through defects can be reduced, resulting in a remarkable industrial effect.

Claims (2)

[Claims] 1. A welding wire used for positive polarity carbon dioxide shield arc welding, wherein C is 0.20 mass% or less, Si
0.25 to 2.5 mass%, Mn 0.45 to 3.5 mass%, rare earth element 0.015 to 0.100 mass%, P 0.002 to 0.05 mass%,
A carbon dioxide shielded arc welding wire containing S in an amount of 0.002 to 0.05% by mass. 2. A D value calculated from the following formula (1) from the contents of Ti, Zr, Al and Cr in addition to the composition, and the contents of Si, Mn, rare earth elements, Ti, Zr and Al. Satisfies the range of 1.4 to 3.0. 2. The carbon dioxide shielded arc welding wire according to claim 1, wherein D = ([Si] / 2) + ([Mn] / 3) + [Ti] + [Zr] + [Al] + (10 × [REM]) (1) [Si]: Welding wire Si content (mass%) [Mn]: Mn content of the welding wire (mass%) [Ti]: Ti content of the welding wire (mass%) [Zr]: Zr content of the welding wire ( Mass%) [Al]: Al content of the welding wire (mass%) [REM]: Rare earth element content of the welding wire (mass%)