JPH08243749A - Gas shield arc welding method - Google Patents

Abstract

PURPOSE: To obtain the welding method having good appearance and shape of bead by using the wire for welding of specified diameter, composition and welding under conditions of the specified shield gas, wire feed speed, peak current value, etc. CONSTITUTION: A diameter of wire for welding has nominal 1.2mm, a composition consists of, by weight, 0.03-0.10% C, 0.5-1.2% Si, 0.7-1.3% Mn, 0.005-0.03% S, 0.001-0.015% 0 and the balance Fe with inevitable impurities. Ti and Al in inevitable impurities are regulated, further, Si+Mn, Si×(Si+Mn) are regulated. By using this wire, a wire feed speed in the shield gas mixing 3-7% 0 to Ar is set to 4-7m/min, an output current of welding power source is set to 380-460A peak current value in pulse wave form of 0.8-2.5ms peak period, pulse MAG welding is executed with spray arc. By this method, spatter as well as burn through are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is suitable for welding thin steel plates in automobile manufacturing processes and the like, and is used for so-called "melting of steel plates" without reducing the welding current and welding speed and reducing the wire diameter. The present invention relates to a gas shield arc welding method capable of preventing "falling" and obtaining a sound weld.

[0002]

2. Description of the Related Art As a burn-through preventive measure in gas shielded arc welding of thin steel sheets, conventionally, a wire having a normal diameter of 1.2 mm is mainly used for welding at a low current and a low speed, or a small diameter (diameter). (0.6-1.0 mm etc.) Welding with a low current using a wire, etc. is generally considered from the viewpoint of welding conditions, and ordinary CO ₂ or Ar-20% CO ₂ is used as the shielding gas. There is.

[0003]

However, in the above-mentioned conventional technique, when a wire having a diameter of 1.2 mm is used, there is a drawback that the welding speed is lowered and the efficiency of the welding operation is lowered. In addition, small diameter (diameter 0.6 ~
When using a wire (1.0 mm, etc.), the diameter is 1.2 m
Since the allowable range of the wire aiming position is narrower than the wire of m and the wire feedability is deteriorated, welding defects are likely to occur. In addition, it is necessary to use a contact tip, a conduit liner, or the like exclusively for the small-diameter wire, and there is a big problem in that parts management is required.

The present invention has been made in view of the above problems, and does not reduce the welding current and the welding speed and reduce the diameter of the wire, that is, the deterioration of the feedability of the wire and the welding defect. It is an object of the present invention to provide a gas shielded arc welding method capable of preventing burn-through and obtaining a sound welded portion while preventing the occurrence thereof and requiring no special part management.

[0005]

The gas shielded arc welding method according to the present invention is a gas shielded arc welding method for a thin steel plate having a thickness of 1.2 mm to 1.6 mm. Yes, C: 0.03-0.10
% By weight, Si: 0.5 to 1.2% by weight, Mn: 0.7 to
1.3% by weight, S: 0.005-0.03% by weight, O:
0.001 to 0.015% by weight, the balance consisting of iron and unavoidable impurities, in which Ti:
0.01% by weight or less, Al: 0.01% by weight or less, and Si + Mn: 1.3 to 2.3% by weight, Si ×
(Si + Mn): using a welding wire having a chemical composition regulated to 0.75 to 2.45, and 3 to 7% by volume in Ar
Of O ₂ 4 the wire feed rate in mixed shielding gas to
The output current of the welding power source is 380 to 460 A and the peak period is 0.8 to 2.5.
It is characterized in that pulse-mag welding is performed by a spray arc as a pulse waveform of ms.

[0006]

In the present invention, by optimizing the combination of the wire composition and the shield gas composition, the penetration is reduced and the spread of the molten pool is expanded as compared with the conventional welding method. As a result, in the conventional method, welding is performed without reducing welding current and welding speed and reducing the diameter of the wire even for joints in which burn-through of steel sheet or bridging failure of the weld pool to the groove surface occurs. It becomes possible. Also, by adjusting the output current waveform of the welding power source as specified in the claims and welding with a spray arc, it is possible to obtain a pulse waveform in which droplet transfer is 1 droplet / 1 pulse, The stability of the molten pool is improved, and burn-through and cross-linking failure can be further suppressed.

Therefore, the efficiency of the entire welding is improved and the quality of the joint is also improved by the effects of shortening the welding (arc generation) time and reducing the number of man-hours for repairing the welding defects.

The reasons for limiting the wire composition and welding conditions in the present invention will be described below. Wire diameter: Nominal 1.2 mm When the wire diameter is less than 1.2 mm, the arc and molten pool are smaller because the diameter is smaller than the proper range, and the allowable range of the wire aiming position is reduced. In addition, the rigidity of the wire decreases due to the decrease in the wire cross-sectional area, and the frequency of occurrence of bending and buckling of the wire increases in a curved feeding system. Therefore, burn-through, cross-linking failure, and the like are likely to occur due to the aim of the wire and poor feeding.

If the wire diameter exceeds 1.2 mm nominally,
The current density decreases due to the increase in the wire cross-sectional area, and the droplet transfer and the molten pool become unstable, so that bridging failure of the molten pool to the groove surface is likely to occur. On the other hand, if the welding current is increased so that the droplet transfer and the molten pool are stable, the penetration becomes deeper and the burn-through easily occurs. In addition, the increase in cross-sectional area increases the rigidity and the feed resistance. For this reason, in a curved feeding system, due to poor feeding of the wire, the frequency of occurrence of burn-through and defective bridging increases.

FIG. 1 is a graph showing the relationship between the wire diameter and the weldable root interval, with the horizontal axis representing the wire diameter and the vertical axis representing the root interval. Wire diameter is 1.2mm
In the case of, it can be seen that the maximum route interval is obtained.

Therefore, from the viewpoint that the arc and the molten pool are relatively large, the droplet transfer and the molten pool are stable, and the aim of the wire and the defective feeding are less likely to occur, the diameter of the applicable wire is nominally 1 mm. 0.2 mm. Shielding gas composition: a mixture of Ar and 3 to 7 volume% O ₂
The atmosphere of the combined gas Ar-O ₂ system has a remarkably strong oxidizing property as compared with the Ar-CO ₂ system, and the oxygen content of the molten metal increases by adding a very small amount of O ₂ . Therefore, the surface tension and the viscosity of the molten metal are significantly reduced, and the molten pool is easily bridged to the groove surface. Further, since the influence of O ₂ on the surface tension and viscosity of the molten metal is larger than that of CO ₂ , Ar—O
_{In the 2} system, compared to the Ar-CO ₂ system, Ar in the shield gas
You can increase the quantity. Since the potential gradient of Ar is smaller than that of O ₂ and CO ₂ , in welding with a constant wire feed rate and arc length, the arc voltage decreases as the Ar content increases, and the penetration depth decreases. Become.

Therefore, from the viewpoint of the cross-linkability of the molten pool to the groove surface and the penetration depth, the shield gas is an Ar--O ₂ system. In this Ar—O ₂ type shield gas, when the O ₂ content is less than 3% by volume, the surface tension and viscosity decrease amount of the molten metal are small, so that the cross-linking property of the molten pool to the groove surface is unsatisfactory. This is sufficient, and the bead appearance and shape defect are likely to occur.

On the other hand, in the Ar-O ₂ shield gas system, when the O ₂ content exceeds 7% by volume, the surface tension and viscosity of the molten metal decrease excessively, resulting in a gap (ie, a root gap) in the groove. The appearance and shape of the bead are likely to deteriorate due to molten metal entering. Further, due to the decrease in the Ar content, the arc voltage increases and the penetration depth increases in welding in which the wire feeding speed and the arc length are constant. Therefore, burn-through easily occurs.

FIG. 2 is a graph showing the relationship between the O ₂ addition rate and the weldable root interval, with the horizontal axis representing the O ₂ gas addition rate and the vertical axis representing the root interval. O ₂ addition rate is 3 ~
The maximum root spacing is obtained with 7% O ₂ .

Therefore, in view of the crosslinkability of the molten pool to the groove surface and the penetration depth, the shield gas composition is a mixed gas in which 3 to 7% by volume of O ₂ is added to Ar. Wire feeding speed: 4 to 7 m / min In the combination of the wire system and the shield gas composition, if the wire feeding speed is less than 4 m / min, adjust the output current waveform (pulse waveform) of the welding power source to a predetermined one. However, it is difficult to use a spray arc, and the occurrence of spatter due to a short arc increases.

The spray arc is characterized in that the droplet diameter is smaller than the wire diameter and the droplets migrate to the molten pool without short circuit. Electromagnetic pinch force is important as the force required to achieve this. This force increases with increasing wire feed rate, ie welding current.

In the present invention, the wire feeding speed is 4 m.
If it is less than / min, the welding current is so small that sufficient electromagnetic pinch force to achieve the spray arc cannot be obtained. As a result, the droplets are short-circuited with the molten pool and migrate to form a so-called short arc.

In the short arc, the droplet is short-circuited to the molten pool, the arc disappears, and the arc is regenerated when the transfer to the molten pool is completed. At this time, particularly in pulsed mag welding as in the present invention, a strong arc force is generated by a high current of about 400 A which is a peak current, so that the droplets or the molten metal in the molten pool are blown off and a large amount of spatter is generated. To do.

Since the spread of the arc and the molten pool in this short arc is smaller than that of the spray arc, it is necessary to reduce the welding speed in order to bridge the molten pool to the groove, which is not preferable.

When the wire feeding speed exceeds 7 m / min, a spray arc can be easily obtained, but since the welding current increases, the penetration depth and the like increase, and burn-through easily occurs.

Therefore, the wire feeding speed is 4 to 7 m / min in view of the amount of spatter generation, the welding speed and the penetration depth.
And As shown in FIG. 3, the wire feeding speed is 4 to 7 m.
In the case of / min, it is found that there is little spatter and the weldable route interval is large. Output current of welding power source: peak current of 380-460A,
Pulse waveform with a peak period of 0.8 to 2.5 ms In the combination of the wire diameter, the shield gas composition and the wire feeding speed, if the peak current is less than 380 A , the pulse conditions such as the peak period may be adjusted. It is difficult to make the droplet transfer one droplet / one pulse, and since the droplet transfer is disturbed, the spatter generation amount increases.

If the peak current exceeds 460 A, even if the pulse conditions such as the peak period are adjusted, the penetration depth increases due to an increase in the welding heat input amount, and the burn-through easily occurs.

In order to set the droplet transfer to 1 droplet / pulse in the peak current range of 380 to 460 A, the peak period is set to 0.
It is necessary to set it in the range of 8 to 2.5 ms. Outside the range, one droplet / one pulse cannot be obtained, so the droplet transfer is disturbed and the spatter generation amount increases.

FIG. 4 is a graph showing the relationship between these pulse waveforms and burn-through sputtering, with the horizontal axis representing the peak period and the vertical axis representing the peak current. As shown in FIG. 4, outside the range of the present invention, burn-through occurs or spatter frequently occurs, and the droplet transfer becomes unstable.

Therefore, the output current of the welding power source has a peak current of 380 to 460 A and a peak period of 0.8 to 2.5 m.
Let s be a pulse waveform. Chemical composition C of welding wire : 0.03 to 0.10% by weight C has the effect of atomizing droplets, and is added for the purpose of reducing the amount of spatter generated. C content is 0.03% by weight
If the amount is less than 1, the atomization of the droplets is insufficient, so that a good effect cannot be obtained with respect to the reduction of the amount and size of spatter. On the other hand, when the C content exceeds 0.10% by weight, the amount of spatters of small particles increases. Further, in high-speed welding of thin plates, the strength and hardness of the weld metal become excessive with respect to the base metal. Since C is a high temperature crack inducing element, the risk of cracking increases. Therefore, the addition amount of C is 0.
It is set to 03 to 0.10% by weight. Si: 0.5 to 1.2 wt% Si has a function of increasing the electrical resistivity of the wire in addition to the normal deoxidizing function, and at the same wire feeding speed, welding increases with the addition amount. It is possible to reduce the current. This reduces the penetration depth and suppresses the occurrence of burn-through. Therefore, Si is added for the purpose of optimizing the viscosity and surface tension of the molten pool, reducing the penetration depth, and preventing the generation of pores due to insufficient deoxidation.

If the amount of Si added is less than 0.5% by weight, the amount of decrease in welding current is small and the decrease in penetration depth is not remarkable. For this reason, a sufficient effect for preventing the occurrence of burn-through cannot be obtained. Further, since the deoxidizing action is small, the viscosity and surface tension of the molten pool are excessively reduced, the molten metal enters the root gap, and the bead appearance and shape are deteriorated. Further, pores are more likely to occur due to insufficient deoxidation.

On the other hand, when the Si content exceeds 1.2% by weight, the viscosity and surface tension of the molten pool increase excessively due to the deoxidizing action, and the crosslinkability of the molten pool to the groove surface decreases, The bead appearance and shape are deteriorated. Further, in high-speed welding of thin plates, the strength and hardness of the weld metal become excessive with respect to the base metal. Therefore, the amount of Si added is 0.5 to 1.2% by weight. Mn: 0.7 to 1.3 wt% Mn is added for the purpose of optimizing the viscosity and surface tension of the molten pool and preventing the generation of pores due to insufficient deoxidation. If the Mn content is less than 0.7% by weight, the deoxidizing effect is small, so that the viscosity and surface tension of the molten pool are excessively reduced as in the case of Si, the molten metal enters the root gap, and the bead appearance and shape are deteriorated. . In addition, pores are more likely to occur due to insufficient deoxidation. On the other hand, if the Mn content exceeds 1.3% by weight, the viscosity and surface tension of the molten pool increase excessively due to the deoxidizing action, and the crosslinkability of the molten pool to the groove surface decreases, so the bead appearance and shape Deteriorates. Further, in high-speed welding of thin plates, the strength and hardness of the weld metal become excessive with respect to the base metal. Therefore, the amount of Mn added is 0.7 to 1.3% by weight. S: 0.005 to 0.03% by weight Since S alone has the effect of lowering the surface tension of the molten metal, the surface tension of the molten pool decreases with an increase in the addition amount, and the crosslinkability to the groove surface Is improved. In addition, the amount of spatter generated is reduced by making the droplets finer. S is added for the purpose of these effects.

If the amount of S added is less than 0.005% by weight, the effect of reducing the surface tension of the molten pool is small, so the crosslinkability to the groove surface is not significantly improved. Further, the effect of atomizing the droplets is small, and the amount of spatter generated is not sufficiently reduced. On the other hand, S
If the addition amount exceeds 0.03% by weight, the surface tension of the molten pool is excessively reduced, and molten metal enters the root gap, so that the bead appearance and shape are deteriorated. Further, the surface tension of the droplets is excessively reduced and the detachment from the wire becomes unstable, so that the spatter generation amount increases. Furthermore, since S is a hot crack inducing element, the risk of cracking increases. Therefore, the amount of S added is 0.005 to 0.03% by weight.
And O: 0.001 to 0.015% by weight O is an oxide such as Si and Mn in the wire,
It is contained on the wire surface as a component of the applied oil and affects the viscosity and surface tension of the droplets and molten pool. Therefore, from the viewpoint of preventing cross-linking failure and increase in spatter generation amount, the O addition amount is specified within a predetermined range in order to optimize the physical properties thereof.

When the O content is less than 0.001% by weight, the surface tension of the droplets excessively increases, so that the droplet diameter increases and large spatters are generated. On the other hand, O content is 0.015
When the content is more than the weight%, the viscosity of the droplets and molten pool and the surface tension are excessively reduced, so that the droplet transfer becomes unstable, the amount of spatter is increased, and the bead appearance and shape are deteriorated. Therefore, the content of O is 0.001 to 0.015.
Weight% Ti and Al in unavoidable impurities: 0.01 wt% or less Since Ti and Al are strong deoxidizing elements, if the Ti and Al contents exceed 0.01 wt%, respectively, the oxygen content of the molten pool decreases. Viscosity and surface tension increase. by this,
The cross-linking property of the molten pool to the groove surface decreases, and the bead appearance and shape deteriorate. Further, since the surface tension of the droplet also increases and the droplet becomes large, the generation amount of large-sized spatter increases. Therefore, the Ti and Al contents are each set to 0.01% by weight or less. Si + Mn: 1.3 to 2.3 wt% Even if the added amount of Si and Mn is within the above range, depending on the total amount of Si and Mn, defective crosslinking or bead appearance and shape may occur depending on the total amount. There is.

That is, when the total amount of Si + Mn is less than 1.3% by weight, the deoxidizing action is small, so that the viscosity and surface tension of the molten pool are excessively reduced and the molten metal enters the root gap to deteriorate the bead appearance and shape. To do. On the other hand, Si + Mn
When the total amount of the above is more than 2.3% by weight, the increase in the viscosity and surface tension of the molten pool becomes excessive, and the defective crosslinking of the molten pool to the groove surface is likely to occur. Therefore, the total amount of Si and Mn added is 1.3 to 2.3% by weight. Si × (Si + Mn): 0.75 to 2.45 Even if the total amount of Si added and the amount of Si and Mn added is within the above range, burn- through, cross-linking failure or bead appearance and shape failure depending on their product. May occur.

When Si × (Si + Mn) is less than 0.75, since the amount of Si is relatively small, the effect of reducing the welding current due to the increase in the wire electrical resistivity is small, and the penetration depth is difficult to decrease. Further, since the amount of Mn is small, the amount of decrease in viscosity and surface tension of the molten pool is large. As a result, the frequency of occurrence of burn-through or bead appearance and defective shape increases.

When Si × (Si + Mn) exceeds 2.45, the electric current of the wire decreases due to the increase of Si, and the welding current decreases. As a result, the penetration depth becomes smaller, and burn-through is less likely to occur. However, since the addition amounts of both Si and Mn increase, the viscosity and surface tension of the molten pool become excessively large due to the deoxidizing action, so that defective crosslinking easily occurs on the groove surface. Therefore, Si x (Si + Mn)
Is 0.75 to 2.45.

In FIG. 5, the horizontal axis represents the amount of Si in the wire,
FIG. 3 is a graph showing the composition range in which the workability is good, with the vertical axis representing the amount of Mn. As shown in FIG. 5, good workability can be obtained when Si and Mn satisfy the above conditions.

[0034]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples that depart from the claims of the present invention.

Steel plates having the compositions and shapes shown in Table 1 below were welded under the welding conditions shown in Table 2 below. The composition of the test wire is shown in Table 3 below. Table 4 below shows the results of experiments on burn-through and spatter generation of the steel sheet. As the welding conditions, the wire diameter, the shield gas composition, the wire feeding speed, and the output current waveform of the welding machine were changed, and the characteristics were investigated together with the wire composition and the like.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4] As shown in Table 4, when the conditions defined in the claims of the present invention are satisfied, the arc form is spray, and good welding results can be obtained even if the welding speed is as high as 100 cm / min. It was However, in the case of the comparative example which deviates from the above conditions, spatter frequently occurs, the bead shape becomes defective, or cross-linking failure occurs.

[0040]

As described above, according to the present invention,
When welding thin steel sheets with a thickness of 1.2 to 1.6 mm, spatter can be prevented and burn through can be prevented without lowering the welding efficiency, the bead appearance and shape are good, and cross-linking failure can be prevented. A possible gas shielded arc welding method can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a wire diameter and a weldable root interval, with a horizontal axis representing a wire diameter and a vertical axis representing a root interval.

FIG. 2 is a graph showing the relationship between the O ₂ addition rate and the weldable root interval, with the horizontal axis representing the O ₂ gas addition rate and the vertical axis representing the root interval.

FIG. 3 is a graph showing a relationship between a wire feeding speed and a weldable root interval, with a horizontal axis representing a wire feeding speed and a vertical axis representing a root interval.

FIG. 4 is a graph showing the relationship between these pulse waveforms, burn-through, and sputtering, with the horizontal axis representing the peak period and the vertical axis representing the peak current.

FIG. 5 is a graph showing the composition range in which welding workability is good, with the horizontal axis representing the amount of Si in the wire and the vertical axis representing the amount of Mn.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C22C 38/00 301 C22C 38/00 301Y 38/14 38/14 (72) Inventor Masaharu Sato Kanagawa Prefecture Fujisawa-shi Miyamae Urakawachi 100-1 Co., Ltd. Kobe Steel, Fujisawa Works (72) Inventor Toshihiko Nakano Fujisawa-shi, Kanagawa Prefecture Miyazaki Urakawachi 100-1 Co., Ltd. Kobe Steel, Fujisawa Works (72) Inventor Susumu Imaoka 100-1 Urakawachi, Miyamae, Fujisawa-shi, Kanagawa Stock company Kobe Steel Works, Fujisawa Works

Claims (1)

[Claims] 1. A gas shielded arc welding method for a thin steel sheet having a thickness of 1.2 mm to 1.6 mm, wherein the diameter is nominally 1.2 mm and C: 0.03 to 0.10% by weight, Si: 0.5 to 1.2% by weight, Mn: 0.7 to 1.
3% by weight, S: 0.005 to 0.03% by weight, O: 0.
001 to 0.015% by weight, the balance consisting of iron and unavoidable impurities, in which Ti: 0.0
1% by weight or less, Al: 0.01% by weight or less, Si + Mn: 1.3 to 2.3% by weight, Si × (Si +
Mn): a welding wire having a chemical composition regulated to 0.75 to 2.45 is used, and a wire feed rate is 4 to 7 m / in a shielding gas in which Ar is mixed with 3 to 7% by volume of O _2.
min, and the output current of the welding power source has a peak current value of 3
A gas shielded arc welding method, which comprises pulse-mag welding with a spray arc in a pulse waveform of 80 to 460 A and a peak period of 0.8 to 2.5 ms.