JP2001239367A - Gas shielded arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a favorable weld metal in a high working efficiency in a high heat input gas shielded arc welding for which a welding wire containing 0.005-0.06 mass % of carbon, 1.5-2.5 mass % of manganese, and 0.12-0.25 mass % of molybdenum is used, and a vertical upward welding work is carried out under 7 kj/mm or more welding heat input condition while weaving in a groove by an automatic welding. SOLUTION: In the welding method using an argon gas containing 15-40% of carbon dioxide as a shielding gas, a vertical upward welding is carried out in a heat input condition while using a consumable electrode containing 0.5-1.0 mass % of silicon, 0.15-0.30 mass % of titanium, and 0.0010-0.0025 mass % of boron.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas shielded arc welding method, and more particularly to a method for efficiently welding a steel structure such as a column connection of a building steel frame with an increase in plate thickness. It is intended to secure a welded portion (weld metal) having good toughness even when the value of the value is increased.

[0002]

2. Description of the Related Art Gas shielded arc welding is widely used as the most common welding method, and with the recent development of robots, fully automatic welding by welding robots has become widespread.

In particular, in the field of welding of steel frames for building buildings, high efficiency has been achieved by applying high heat input welding.
2. Description of the Related Art A gas shielded arc welding method using a vertical upward movement as disclosed in JP-A-6-190556 is known.

[0004] The above-mentioned welding method is characterized in that the torch is swung while the torch is rotated around each layer within the groove surface, and according to this, heat input is reduced. It is described that even when the size is large, the occurrence of defects such as undercuts and convex beads is suppressed, and it is possible to improve the welding efficiency and the bead appearance.

[0005] In this method, however, the toughness of the obtained weld does not reach a desired level.

[0006] On the other hand, in gas shielded arc welding in which the vertical ascent is applied, to improve the toughness of the welded portion, the content of the wire component, such as carbon, is adjusted to a desired range and Ti or B is reduced. Japanese Patent Application Laid-Open No. Sho 56
Although the technology disclosed in Japanese Patent Application Publication No. 66383 is known, the technology disclosed herein is intended for welding low-temperature steel, and has a large heat input welding as the object of the present invention. However, not only is the alloy element content of the entire steel expressed by the carbon equivalent insufficient, but also welding defects are likely to occur.

Further, Japanese Patent Application Laid-Open No. 51-78750 proposes to improve the toughness of a welded portion by specifying a chemical composition in a wire in vertical advance welding using carbon dioxide gas as a shielding gas. However, when the heat input of welding exceeds 6.5 kJ / mm, the toughness of the welded portion becomes insufficient and the heat input of the wire becomes 10 kJ / mm.
Above J / mm, extremely low values cannot be avoided.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas shielded arc welding (hereinafter, referred to as MAG welding) using an Ar gas mixed with carbon dioxide as a shielding gas, with a welding heat input of 7 kJ / mm. To propose a new method that enables efficient welding by automatic welding and secures a tough welded part, even for large heat input welding that targets thick steel plates exceeding It is in.

[0009]

Means for Solving the Problems In conventional MAG welding,
When large heat input welding is not assumed and a welding wire developed for MAG welding is simply used, blowholes are likely to occur, and when carbon dioxide gas is used as a shielding gas, the toughness of the weld is not sufficient. is not. The present invention comprehensively examines the chemical composition of a weld metal, the occurrence of welding defects, and the like in large heat input welding such as vertical upward welding, and performs large heat input welding to generate a wide weld metal original part. MAG
A wire composition suitable for welding is found, and welding is performed using this wire.

That is, the present invention relates to a welding method performed by using an Ar gas containing 15 to 40% of CO ₂ as a shielding gas, wherein C: 0.005 to 0.06 mass%, Si: 0.5 to 1.0mm%, Mn: 1.5-2.5mass%, Ti: 0.15-0.30mass%, Mo: 0.12-0.25mass%, B: 0.0010-0.0025mass% This is a gas shielded arc welding method characterized by performing vertical upward welding under a large heat input condition in which the welding heat input is 7 kJ / mm or more while weaving inside.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a thick steel plate can be welded with high efficiency while suppressing generation of slag and spatter. For example, as shown in FIGS. 1 (a) and 2 (b), in the joining of a steel column with a column penetration type and a connection as shown in FIG. It refers to a vertical weaving welding method in which welding is performed while being raised every cycle. This conventional welding method requires a large number of welding passes and increases the probability of occurrence of welding defects when the thickness of conventional downward or sideways welding is increased, but has a small number of passes and is efficient and has insufficient penetration or poor fusion. It is characterized by the fact that defects are unlikely to occur.

Hereinafter, the reasons for limiting the composition of the welding wire specified in the present invention will be described.

C: 0.005 to 0.06 mass% (hereinafter, mass% is simply expressed as%) C is inevitably contained in the steel welding wire, but C secures the strength of the weld metal. And is also useful as a deoxidizing element. Its content is 0.005
%, The strength of the weld metal is insufficient. On the other hand, if it exceeds 0.06%, a decrease in toughness cannot be avoided. Therefore, in the present invention, the content is set to 0.005 to 0.06%.

Si: 0.5 to 1.0%, Si is an indispensable element as a deoxidizing element in a wire for CO ₂ welding or MAG welding. If the content of Si is less than 0.5%, the deoxidizing effect is insufficient and blowholes are easily generated. On the other hand, if it exceeds 1%, the content in the weld metal becomes excessive, and on the contrary, the toughness decreases. For this reason,
In the present invention, the range is limited to 0.5 to 1.0%.

Mn: 1.5 to 2.5%, Mn is an element that is not only an indispensable element together with Si as a deoxidizing element, but also improves the mechanical properties of the weld metal. If the content of Mn is less than 1.5%, the content in the weld metal is insufficient, so that sufficient strength and toughness cannot be obtained.
However, if the content exceeds 2.5%, the content in the weld metal becomes excessive and the toughness is deteriorated.
Therefore, in the present invention, Mn is limited to the range of 1.5 to 2.5%.

Ti: 0.15 to 0.30%, Ti is a gas shield gas arc welding wire having a relatively high heat input, which stabilizes the arc, reduces spatter, prevents the occurrence of blow holes, and improves the toughness. There is. However, its content is 0.15
%, The effect is poor. On the other hand, when it exceeds 0.30%, there is a problem in that productivity is reduced due to a problem in wire smelting. For this reason, in the present invention, it was limited to the range of 0.15 to 0.30%.

Mo: 0.12 to 0.25%, Mo is an element indispensable for refining the structure of a weld metal and improving toughness in large heat input welding. The effect is
If it is less than 0.12%, it is poor, but if it is added more than 0.25%, a low-temperature transformation structure is formed in the structure of the weld metal, hardening and toughness is deteriorated. Therefore, in the present invention, 0.12 to 0.
Limited to a range of 25%.

B: 0.0010 to 0.0025%, B is a useful element for suppressing the formation of coarse ferrite in the structure of the weld metal to refine the structure and improve the toughness. There is a disadvantage to make it easier. If B in the wire is less than 0.0010%, it is not enough to obtain the effect of improving the toughness, particularly by refining the structure. On the other hand, if it exceeds 0.0025%, no further improvement in the toughness can be expected. Rather, cracks tend to occur. For this reason, in the present invention, it was limited to the range of 0.0010 to 0.0025%.

The present invention provides the above-mentioned elements, if necessary,
Ni: 3.0% or less, Cr: 0.5% or less, Cu including plating 2.
0% or less, Nb and V; can be added under 0.1% or less. Further, as for P, S, and Al inevitably contained, it is sufficient that S, P: 0.03% or less and Al: 0.05% or less.

In the present invention, the welding heat input is 7 kJ while weaving in a groove by automatic welding.
/ Mm or more, the vertical upward welding is performed, and the welding current at that time is preferably 150 to 300A. The reason is that it is difficult to get a stable arc below 1.50A,
On the other hand, if it exceeds 300 A, the wire feedability deteriorates and it is difficult to perform welding for a long time.

In the present invention, it is desirable that the welding after the second pass be performed by two-electrode submerged arc welding.

In performing the two-electrode submerged arc welding, an appropriate welding heat input condition is set, or a laminating method in which welding defects hardly occur is applied.

[0023]

EXAMPLE Using a steel plate having a composition as shown in Table 1 and having a groove shape as shown in FIG. 3 using a steel plate having a thickness of 25 mm, and using a welding wire having a composition as shown in Table 2, respectively, Table 3 was used. Gas shielded arc welding was performed under the following conditions, and the absorbed energy of the welded portion and the occurrence of welding defects were investigated.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

Table 4 shows the results of the investigation. When welding was performed in accordance with the method of the present invention (Nos. 1 to 3), the absorbed energy showed a high value, and no welding defects were generated. On the other hand, in Comparative Examples (Nos. 4 to 6),
It was confirmed that although there was no welding defect, the value of the absorbed energy was small or the value of the absorbed energy was high, but the occurrence of welding defects was inevitable.

[0029]

According to the present invention, welding heat input is 7 kJ / mm.
In the case of large heat input gas shielded arc welding and vertical upward welding that enables highly efficient construction, a good weld metal can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a welding example.

FIGS. 2A and 2B are diagrams showing groove shapes.

FIG. 3 is a diagram showing a groove shape used in the embodiment.

[Explanation of symbols]

 1 Steel plate (base material) 2 Backing metal

Continuation of the front page (72) Inventor Yoshitaka Sasa 1-chome, Kawasaki-dori, Mizushima, Kurashiki-shi, Okayama Pref. No address) F-term in Kawasaki Steel Corporation Mizushima Works (reference) 4E001 AA03 BB06 CA01 DA03 DD02 DD04 DF04 EA02 4E081 AA08 AA12 BA37 BB03 CA09 DA05 DA20 DA57 DA62 EA24 FA14

Claims (1)

[Claims] 1. A shielding gas comprising 15 to 40% of C
A welding method performed using an Ar gas containing O ₂ , wherein consumable electrodes include: C: 0.005 to 0.06 mass%, Si: 0.5 to 1.0 mass%, Mn: 1.5 to 2.5 mass%, Ti: 0.15 to 0.30 mass %, Mo: 0.12 ~ 0.25mass%, B: 0.0010 ~ 0.0025mass%, Welding with welding heat input of 7kJ / mm or more while weaving in the groove by automatic welding. A gas shielded arc welding method comprising performing vertical upward welding under thermal conditions.