JPH09206984A - Gas shield arc welding for thin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas shield arc welding method having excellent prosity resistance and gap resistance and capable of performing low spatter welding in a high speed gas shield welding for a thin steel sheet and galvanized steel sheet. SOLUTION: In pulse-MAG welding using gas shield arc welding steel wires for the thin sheet, which contain the specified amount of C, Si, Mn, S and O, moreover one kind or more of Al, Ti or Zr, further if necessary one kind or more of Nb, V or Ta and substantially the balance Fe, the range of peak current Ip=380-680 (A) of pulse current, pulse peak time Tp=0.4-3.0(msec) and base current Ib=20-100 (A) are applied. Welding having excellent prosity resistance, gap resistance and few amount of spatter generation is performed in the high speed gas shield arc welding for the galvanized steel sheet and thin sheet by adding suitable alloy elements and applying the pulse-MAG welding method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to Ar--CO ₂
The present invention relates to a method for welding a thin steel sheet using a mixed gas as a shield gas, and more particularly to a pulsed mag welding method capable of obtaining excellent weldability in welding a galvanized steel sheet and a non-surface-treated cold-rolled and hot-rolled thin sheet. .

[0002]

2. Description of the Related Art As a means for compensating for the rust-prone defect of steel or the like, there is a surface-treated steel sheet obtained by coating a cold-rolled steel sheet or hot-rolled steel sheet with a zinc-based paint or galvanizing. In the field of thin plates, these surface-treated steel sheets are used not only in columns such as prefabricated structures, building materials such as roofs, gasoline cans, washing machine parts, but also in automobile bodies.

Gas shielded arc welding is often used for welding these surface-treated steel sheets. However, in the welding of zinc-based surface-treated steel sheets, the occurrence of pore defects such as pits and blowholes and the increase in the amount of spatter. In addition to the problem
There are various problems such as burn-through and a narrow condition range for the gap between the welded members. In particular, recently, with the progress of automation through the adoption of welding robots, the above problems tend to become more apparent as a factor that hinders automation, and it is strongly desired to solve these problems.

Since the automation of thin plate welding is aimed at improving productivity, welding is often performed at a high welding speed of about 1 m / min or more. Therefore, it is necessary to perform stable welding in a high speed region. In the welding of such a thin plate, the welding speed must be set high and the welding current must be set low in order to prevent burn-through, so that the welding heat input becomes small and the cooling rate becomes fast. For this reason, in the case of a galvanized steel sheet, a sufficient time required for floating the zinc-based gas that has penetrated into the molten metal cannot be obtained, so that pore defects frequently occur. Further, since high-speed welding is likely to result in poor shielding properties, it is necessary to consider pore defects due to the shield surface. Further, in high-speed welding of thin plates, the welding condition range for the groove gap is also narrowed, so it is necessary to satisfy the gap resistance at the same time.

A technique for preventing pore defects in a galvanized steel sheet is disclosed in Japanese Unexamined Patent Publication No. 63-56395, Te,
A technique has been proposed in which an inhibitor composed of a simple substance such as Se or REM or an oxide, a carbonate, a fluoride or the like is applied to the surface of a steel sheet. In Japanese Patent Laid-Open No. 63-108995, phosphorus iron is the main component. Although coating agents have been proposed, these are not only required to be applied on the surface of the steel sheet in advance before welding, but also a step of removing the coating agent is required after welding, which makes it practical. is not.

Next, a steel wire is disclosed in Japanese Patent Laid-Open No. 63-7.
2498 discloses a large amount of Ni in addition to Al, Ti and Cu.
There is a proposal of a solid wire containing a metal. However, such a composition cannot be expected to be effective for high-speed welding of galvanized steel sheet, which is the object of the present invention. Further, in Japanese Patent Application Laid-Open No. 1-309796, C, Si, Mn, B
A solid wire for welding galvanized steel sheet in which the addition amounts of i, O, and Ti are regulated is disclosed. Although this technique is effective in suppressing pores in the galvanized steel sheet and reducing the amount of spatter generation, no consideration is given to the gap resistance of thin plate high-speed welding.

Further, Japanese Patent Laid-Open No. 4-41098 discloses that
C, Si, Mn, Bi to Nb, V and Al, Ti, Z
Solid wires for various surface-treated steel sheets in which r is regulated are disclosed. This wire is also effective for the porosity resistance of the galvanized steel sheet, but cannot be expected to be effective for the reduction of spatter generation and the gap resistance. Further, Japanese Patent Laid-Open No. 5-305445 proposes a welding method of zinc-based plated steel sheet, but the welding speed is 100 cm /
High-speed welding exceeding min has no effect on porosity resistance, and no consideration is given to gap resistance.

Furthermore, Japanese Patent Laid-Open No. 5-305476, which is intended for high-speed welding of thin plates, discloses C, Si, Mn, P,
This is a proposal of a solid wire in which the amounts of S, Al, N, O, and Mn / Si ratio are specified. Of these, the addition of S is intended to reduce the amount of spatter generated in high-speed welding of ordinary steel plates, improve bead formability, and improve slag peelability. Further, O is rather limited in consideration of adverse effects on the workability of the core wire and the workability of welding. As described above, this proposal is also intended for high-speed welding of only a plain steel plate having a size of about 3.2 mm, and does not satisfy the pore resistance of the surface-treated steel plate.

Further, in Japanese Patent Laid-Open No. 5-329682, in addition to the amounts of C, Si, Mn, P, S, the amounts of Ti, Nb,
Further, a pulsed MAG welding method in which a shielding gas is regulated has been proposed. Although this method is also effective in reducing the porosity resistance and the amount of spatter generation of the zinc-based plated steel sheet,
No effect can be expected on gap resistance.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. In high-speed welding of thin plates, porosity resistance, low spatter amount, and gap resistance are simultaneously achieved. It is an object of the present invention to provide a satisfactory pulsed mag welding method.

[0011]

That is, the gist of the present invention is that, in weight% with respect to the total weight of the wire,
C: 0.02 to 0.40%, Si: 0.50 to 2.0
%, Mn: 0.20 to 3.0%, S: 0.005 to 0.
050%, O: 0.0030 to 0.050%,
Al: 0.005-0.20%, Ti: 0.005-
0.20%, Zr: 0.005 to 0.20% of 1 or 2 or more, or Nb: 0.05 to.
1.50%, V: 0.05 to 1.50%, Ta: 0.0
The peak current Ip of the pulse current is 380 to 680 in pulsed mag welding using a gas shielded arc welded steel wire for a thin plate containing 5 to 1.50% of 1 type or 2 types, and the balance being substantially Fe. (A), the pulse peak time Tp is 0.4 to 3.0 (msec), and the base current Ib is in the range of 20 to 100 (A).

[0012]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems in high-speed welding of thin plates, and as a result, while ensuring the gap resistance, there is no generation of pores due to defective shielding, and the amount of spatter is small. The present invention has completed the welding method of the present invention, which has a small number of defects. That is, the inventors can improve the gap resistance by examining the amounts of S and O.
It was also found that by selecting the pulse conditions by pulse welding, the amount of spatter generation can be reduced and the gap resistance can be improved.

By adding S, the penetration of the weld metal is reduced and the bead width of the weld metal is increased by adding S,
It has the effect of improving the wettability to the base material, improving the crosslinkability, and improving the gap resistance. However, if only S is added, the arc stability is insufficient in the high-speed welding targeted by the present invention. The addition of O is effective for improving high-speed weldability, and O also has the effect of improving the gap resistance like S, and the coexistence of S and O is effective for improving the gap resistance in high-speed welding. . This stabilizes the arc state, which also contributes to the reduction of spatter generation. Furthermore, A
The addition of 1, Ti, and Zr is effective in reducing the amount of spatter generated. Further, V, Nb, and Ta fix nitrogen in the weld metal when the shield is defective to improve the shield resistance, and also change the viscosity of the molten metal to effectively act on the gap resistance.

Thus, the coexistence of S and O, Al, Ti,
In addition to the effects of Zr, Ta, etc., pulse conditions by pulse arc welding (peak current = Ip, peak time = Tp,
By properly setting the base time = Ib), the arc state can be stabilized, and a pulse arc welding method with reduced spatter generation in high-speed welding, improved gap resistance, and improved crack resistance can be obtained. Arrived

The reasons and effects of limiting the components and the reason for limiting the pulse conditions of the present invention will be described in detail below. C: 0.02 to 0.40% C is effective in suppressing generation of pores in the galvanized steel sheet in the constitution of the present invention. However, if the C content is less than 0.02%, the effect is not recognized, and if it exceeds 0.40%, the spatter generation amount increases and the crack susceptibility becomes extremely high even in high-speed welding of thin plates. 0.02-0.4
0%.

Si: 0.50 to 2.0% Si is added as a main deoxidizer, but besides, it has the effect of improving the bead shape and improving the gap resistance in high speed welding. However, if the Si amount is less than 0.50%, these effects cannot be obtained, and if it exceeds 2.0%, the slag generation amount increases, so the range was made 0.50 to 2.0%.

Mn: 0.20 to 3.0% Mn acts as a deoxidizer together with Si, and is added for the purpose of improving the bead shape. However, if the amount of Mn is less than 0.20%, the deoxidation is insufficient and the generation of pores due to factors other than zinc becomes significant, and spatter frequently occurs, so the lower limit was made 0.20%. Also, the Mn content is 3.0%
If it exceeds, the gap resistance deteriorates and the hardening of the weld metal becomes remarkable, so the upper limit was made 3.0%.

S: 0.005 to 0.050% S is extremely effective as an element for improving the gap resistance together with oxygen. The effect is exhibited from about 0.005%, but on the other hand, if it exceeds 0.050%, the risk of cracking resistance increases as with P, so the range of S is from 0.005 to 0.005.
0.050%.

O: 0.0030 to 0.050% O is an element necessary for securing the gap resistance in high speed welding together with S. It also has the effect of reducing the amount of spatter generated. With the configuration of the present invention, 0.0030
%, The effect becomes remarkable, but if it exceeds 0.050%, not only the effect is saturated, but also the arc becomes unstable and spatter frequently occurs.
It was set to 030 to 0.050%. The existing form of O may be evenly distributed in the wire as a solid solution or an oxide, but it is more preferable that it is concentrated in the wire surface portion as an internal oxide layer or a grain boundary oxide layer.

Al: 0.005-0.20% Al is a strong deoxidizing element, and as a nitrogen fixing element, T
Along with i and Zr, the addition of an extremely small amount has the effect of suppressing the generation of pores due to defective shielding. However, when the amount of Al is 0.1.
If it is less than 005%, the above effect is not observed, and it is 0.20.
If it exceeds 0.1%, the amount of slag generated increases and the generation of pores by zinc is promoted, so the upper limit must be 0.20%.

Ti: 0.005 to 0.20% Ti is a strong deoxidizing agent like Al and Zr, and as a nitrogen fixing element, addition of a very small amount of Ti has the effect of suppressing the generation of pores due to defective shielding. is there. Further, Ti stabilizes the arc and effectively acts to improve high-speed weldability and reduce the amount of spatter generated. However, if the Ti content is less than 0.005%, the above effect is not observed, and if it exceeds 0.20%, the slag generation amount increases, the slag encapsulation area on the bead surface increases, and the zinc-coated steel sheet has pores. To accelerate the outbreak
The upper limit needs to be 0.20%.

Zr: 0.005 to 0.20% Zr is a strong deoxidizer like Al and Ti.
It has the effect of suppressing the generation of pores due to poor shielding by the combined addition of The effect is exhibited when the Zr amount is 0.005% or more. However, when the Zr content exceeds 0.20%, the same action as Al and Ti promotes the generation of pores, so the upper limit was made 0.20%.

Nb: 0.05 to 1.50% Nb is a nitride-forming element, which suppresses the generation of pores due to defective shielding and also has an effect on the generation of pores due to zinc. It also improves the gap resistance in welding. The effect is recognized at the addition of 0.05% or more. However, if the amount of Nb exceeds 1.50%, the above effects are saturated and the hardness of the bead becomes significantly high, so the upper limit was made 1.50%.

V: 0.05 to 1.50% V forms a nitride together with Nb, and is added for the purpose of suppressing generation of pores due to defective shield. However, if the V content is less than 0.05%, the effect is insufficient, and if it exceeds 1.50%, the crack susceptibility increases, so 0.05 to 1.50%.
Range. Ta: 0.05 to 1.50% Like Nb and V, Ta is added as a nitrogen fixing element.
The effect is recognized in the range of 0.05 to 1.50%.

The reason for setting the pulse condition of the pulse mag welding in combination with the above wire is as follows. Peak current Ip = 380 to 680 (A) If the peak current is less than 380 A, the electromagnetic pinch force becomes weak, the detachment of droplets from the wire is likely to be unstable, and the amount of spatter is increased. Further, if it exceeds 680A, the effective heat input increases, the penetration depth increases, and it becomes difficult to secure the penetration width, and the gap resistance deteriorates. Therefore, the peak current Ip is set in the range of 380 to 680 (A).

Peak time Tp = 0.4 to 3.0 (msec) Peak time is less than 0.4 msec, and 3.0 mse
If it exceeds c, the droplet transfer morphology becomes unstable, not only the amount of sputtering increases but also the gap resistance decreases, so the peak time Tp was set to a range of 0.4 to 3.0 (msec). Base current Ib = 20 to 100 (A) When the base current is less than 20 A, the droplet and the molten pool are likely to be short-circuited during the base period, the arc becomes unstable, the amount of spatter increases, and the gap resistance is also improved. to degrade. on the other hand,
If the base current exceeds 100 A, it is likely to be affected by the arc, so that the droplet transfer becomes unstable and the amount of spatter increases.

The present invention will be specifically described below with reference to examples.

[0028]

EXAMPLE A steel wire having a chemical composition shown in Table 1 (wire diameter: 1.2 mmφ) was welded under the welding conditions shown in Table 2 and the gap resistance, porosity resistance, and spatter generation amount were investigated. The gap resistance was evaluated by welding with the joint shape shown in FIG. Table 3 shows the evaluation results of the porosity resistance, the gap resistance, and the spatter generation amount in this welding.

Further, the wire symbol No. By 5,
Pulse arc welding under various pulse conditions was carried out under the welding conditions shown in Table 2, and gap resistance, porosity resistance, and spatter generation amount were investigated. The pulse conditions and evaluation results are shown in Table 4, and examples of pulse waveforms are shown in FIGS. 2 and 3. As for the evaluation criteria, the number of pits is measured by visual inspection for porosity resistance and converted to 4 or less per 1 m of bead, and the blowhole occurrence rate is determined by X-ray transmission inspection. / A bead length of 30% or less was regarded as acceptable. In addition, the gap resistance was evaluated to be acceptable when the gap in which welding was possible was 2.0 mm or more, and the amount of spatter was evaluated to be 1.0 g / min or less when the weight of the spatter collected by the steel collection box was evaluated. Was accepted. Crack is X
The line penetration test was conducted by excluding the crater portion of the weld bead.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

Wire No. In No. 7, since the amount of C exceeds the range of the present invention, the amount of spatter is particularly large and cracking is recognized. Wire No. In No. 8, the amount of Si exceeds the limit range of the present invention, but the performance of each item is not sufficiently obtained as a whole. Wire No. In No. 9, since the amount of Si is less than the range of the present invention, pits and blow holes different from the pores due to zinc are often generated, the gap resistance is inferior, and the amount of sputtering is large.

Wire No. In No. 10, the Mn content exceeds the range of the present invention, so that the porosity resistance and the gap resistance are particularly insufficient. Wire No. No. 11 had a Mn amount less than the range of the present invention, and the wire No. Similar to the case of No. 7, many pores are generated, many spatters are generated, and the gap resistance is deteriorated. Wire No. No. 12, since the amounts of S and O are less than the range of the present invention,
In particular, the gap resistance is inferior, and other performances are also insufficient as a whole.

Wire No. In No. 13, Ti exceeds the range of the present invention, the porosity resistance and the amount of spatter generation are large, and the performance is not satisfied. Wire No. 14 is Al, Ti,
The amount of Zr does not satisfy the range of the present invention, the porosity resistance is extremely poor, and the amount of sputtering is large. Wire No.
In No. 15, Nb, V, and Ta contents were less than the ranges of the present invention, the porosity resistance was particularly poor, and the sputter amount was large, and cracks were generated.

Wire No. No. 16 is a wire whose V amount exceeds the range of the present invention, and cracks have occurred. Test symbol N
o. In No. 6, since the peak current exceeds the range of the present invention and the peak time is outside the range of the present invention, the gap resistance is poor, the amount of sputtering is large, and the porosity resistance is insufficient. This test code No. An example of the pulse waveform of No. 6 is shown in FIG.

Test code No. In No. 7, the peak current is less than the range of the present invention, the arc becomes unstable, spatter is often generated, and the porosity resistance is inferior. Test code No. 8 is
The base current is out of the range of the present invention, the arc becomes unstable, and spatter frequently occurs. Test code No. 9 and No. In No. 10, the peak time is out of the range of the present invention, the droplet transfer becomes unstable, and each performance is not satisfied.

In comparison with these, the wire No. 1 to
No. 6 and test code No. 1 to No. In No. 5, it is clear that good performance is obtained in any of the items.

[0040]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to perform welding of a surface-treated steel sheet and a normal steel sheet with excellent porosity resistance and gap resistance at high speed welding with a small amount of spatter.

[Brief description of drawings]

FIG. 1 is a perspective view showing a joint shape of a test plate.

FIG. 2 is a diagram showing an example of a pulse waveform.

FIG. 3 is a diagram showing an example of a pulse waveform.

Claims (2)

[Claims] 1. C: 0.02 to 0.40%, Si: 0.50 to 2.0%, Mn: 0.20 to 3.0%, S in weight% with respect to the total weight of the wire. : 0.005 to 0.050%, O: 0.0030 to 0.050%, Al: 0.005 to 0.20%, Ti: 0.005 to 0.20%, Zr: 0. 005-0.20% of 1 type (s) or 2 or more types, and the balance is substantially F.
In the pulsed mag welding using the gas shielded arc welding steel wire for thin plate made of e, the peak current Ip of the pulse current is 380 to 680 (A), the pulse peak time Tp is 0.4 to 3.0 (msec), and the base current Ib. 20 ~
A gas shield arc welding method for thin plates, characterized in that the range is 100 (A). 2. C: 0.02 to 0.40%, Si: 0.50 to 2.0%, Mn: 0.20 to 3.0%, S in weight% with respect to the total weight of the wire. : 0.005 to 0.050%, O: 0.0030 to 0.050%, Al: 0.005 to 0.20%, Ti: 0.005 to 0.20%, Zr: 0. 005-0.20% of 1 type (s) or 2 or more types, Nb: 0.05-1.50%, V: 0.05-1.50%, Ta: 0.05-1.50% 1 or 2 or more and the balance is substantially F
In the pulsed mag welding using the gas shielded arc welding steel wire for thin plate made of e, the peak current Ip of the pulse current is 380 to 680 (A), the pulse peak time Tp is 0.4 to 3.0 (msec), and the base current Ib. 20 ~
A gas shield arc welding method for thin plates, characterized in that the range is 100 (A).