JP2014200812A - Solid wire for gas shield arc welding of thin steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid wire for gas shield arc welding of a thin steel sheet, with which high-speed welding is enabled with stable arc, a preferable bead shape, reduced spatter generation, and reduced slag generation even if there is a large gap between thin steel sheets.SOLUTION: The solid wire for gas shield arc welding of a thin steel sheet includes, by mass relative to the wire total mass, 0.03 to 0.10% C, 0.5 to 1.0% Si, 1.4 to 2.0% Mn, 0.1 to 0.3% Ti, 0.01 to 0.1% Bi, 0.005 to 0.070% S, 0.03% or less P, 0.01% or less O, and Fe with inevitable impurities as the balance.

Description

The present invention can be applied to short arc welding of a CO ₂ gas shield or MAG welding in which Ar, CO ₂ , O _2, etc. are combined with a shielding gas and pulse MAG welding in the welding of a thin steel plate having a thickness of 0.6 to 3.2 mm. The present invention relates to a solid wire for gas shielded arc welding of a thin steel plate that is used, has a smooth bead shape with good bead start-in fit, and has good crosslinkability.

Conventionally, a gas shield arc welding method using a solid wire is highly efficient and widely applied to welding of thin steel sheets because a weld metal with good mechanical performance and a good bead shape can be obtained. Generally, a short arc welding method using CO ₂ as a shielding gas is used. From the viewpoint of reducing the amount of spatter generated and ensuring high-speed weldability, the main component is Ar gas, and CO ₂ is mixed with this. In recent years, MAG welding or pulse MAG welding methods using a shielding gas mixed with O ₂ gas have been increasing. These welds are applied under high current and high speed welding conditions to improve productivity, and form a good weld bead to produce a sound welded joint.

  In recent years, high quality and high efficiency are required for welded structures by gas shielded arc welding using solid wires. For example, in the automobile industry, the weight of steel materials has been reduced for the purpose of improving fuel efficiency in order to reduce environmental impact. In order to reduce the weight of steel materials, there is an increasing demand for high-strength materials that can ensure the strength of the steel materials to be used even in thin plates. Since the strength of the steel material increases the springback of the steel sheet, the gap of the welded part is widened in construction. Therefore, a wire with good gap resistance is desired.

  The surface tension and viscosity of the molten metal greatly affect the gap resistance. It is important to widen the bead width by reducing the surface tension and to make it difficult for the bead to droop by increasing the viscosity. Therefore, there is a need for a wire that can optimize the surface tension and viscosity of the molten metal, obtain a wide bead width that can bridge the gap, and can realize a good bead shape that does not easily melt.

  FIGS. 1A, 1 </ b> B, 1 </ b> C, 1 </ b> D, and 1 </ b> E show an example of a bead shape state in the case where there is a gap G in a lateral orientation of a lap joint portion of a thin steel plate. FIG. 1A is an example in which a weld metal 3 having a good bead shape without melting or bead dripping is obtained. FIG. 1B shows an example in which an undercut 4 occurs, and FIG. 1C shows an example in which the weld metal hangs down to the front plate 1 side. FIG. 1 (d) is an example in which the rear plate has melted, and FIG. 1 (e) is an example in which the weld metal has dropped in the gap G between the front plate 1 and the rear plate 2. As described above, when the gap G of the lap joint portion is large, there is a problem that undercut occurs or the weld metal is liable to sag and it is difficult to form a good weld bead.

From such a background, as a solid wire for gas shielded arc welding of a thin steel plate, Japanese Patent Application Laid-Open No. 2007-31558 (Patent Document 1) obtains a stable and wide bead shape even in high-speed welding with a high S wire component. The technique of being able to be performed is disclosed. In the present technology, a wide bead can be obtained by reducing the flow velocity of the weld metal to the rear by S and promoting the hot water flow in the width direction.

  However, S not only causes hot cracking, but with the addition of S, sulfides are coarsened, and the strength and toughness of the material are reduced. Therefore, as a countermeasure, one or more contents of Mn and Ti, Zr, La, and Ce are specified to prevent hot cracking. However, the specified amount of Mn is insufficient to suppress hot cracking. Further, S greatly reduces the viscosity of the molten metal, and the weld with a wide gap causes the bead to be burned out, so that the gap resistance performance is insufficient.

  Japanese Patent Application Laid-Open No. 62-40995 (Patent Document 2) discloses a technique in which Bi is added to improve slag peelability in high-current carbon dioxide arc welding. However, the focus is only on slag peelability, and no consideration is given to gap resistance performance. Furthermore, in JP-A-61-159296 (Patent Document 3), components such as S + O are added to a composition composed of C, Si, Mn and Ti, and the amount of each component is optimized to reduce sputtering. There is a disclosure of the technology to make it.

  However, no consideration is given to the gap resistance performance during high-speed welding of mixed gas, and there is a problem in that high-speed welding at a portion having a gap causes unstable arcs, a large amount of spatter, and poor bead shape. It was.

JP 2007-31558 A Japanese Patent Laid-Open No. 62-40995 JP-A 61-159296

  The present invention enables high-speed welding even when the gap of the thin steel plate is large, makes the bead shape smooth and satisfactory, suppresses the occurrence of high temperature cracks, stabilizes the arc, and generates spatter and slag. An object of the present invention is to provide a solid wire for gas shielded arc welding of a thin steel plate with a very small amount.

  The gist of the present invention is mass% with respect to the total mass of the wire, C: 0.03 to 0.10%, Si: 0.5 to 1.0%, Mn: 1.4 to 2.0%, Ti: 0 0.1 to 0.3%, Bi: 0.01 to 0.1%, S: 0.005 to 0.070%, P: 0.030% or less, O: 0.010% or less, The other is a solid wire for gas shielded arc welding of a thin steel plate characterized by Fe and inevitable impurities.

  According to the solid wire for gas shielded arc welding of the thin steel plate of the present invention, high-speed welding is possible even when the gap is large, the arc is stable, the amount of spatter generation is extremely small, and the bead shape is smooth and beautiful, It becomes possible to obtain a high quality weld metal that does not cause hot cracking.

(A), (b), (c), (d), (e) is a figure which shows the example of a bead formation state in case there exists a gap in the horizontal attitude | position of the lap joint part of a thin steel plate, respectively. It is a figure which shows the test plate of the horizontal lap joint used for the Example of this invention. It is a figure which shows the wire aiming position of the horizontal lap joint part in the Example of this invention.

Hereinafter, the solid wire for gas shielded arc welding of the thin steel plate of the present invention will be described in detail. In order to solve the above-mentioned problems, the inventors made a trial manufacture of wires having different components, and formed a JIS G3131 SPCC steel plate having a thickness of 2.0 mm and a length of 450 mm into a tapered spacer as shown in FIG. 5 is a horizontal lap joint with a gap G ₁ = 2 mm and G ₂ = 4 mm sandwiched between the back plate 2 and the front plate 1, short arc welding by CO ₂ welding, Ar-20% CO ₂ gas is used MAG welding, MAG welding using Ar-20% CO ₂ -3% O ₂ gas, pulse MAG welding using Ar-20% CO ₂ gas, and Ar-20% CO ₂ -3% O ₂ gas The pulse MAG welding was performed at a high welding speed of 80 cm / min, and the arc state, bead shape, spatter generation, gap resistance performance, etc. were investigated in detail.

  As a result, in any welding method, appropriate amounts of Bi, S, and Ti are added to the wire, and the amounts of C, Si, and Mn are optimized to optimize arc stability, molten metal viscosity, and surface tension. It has been found that a wide and smooth bead can be obtained with a reduction in the amount of spatter generated, an effect of preventing hot cracking and gap resistance.

Hereinafter, the reason for limiting the wire composition and the content thereof in the present invention will be described. In addition, content of each component is shown by the mass%.
[C: 0.03-0.10%]
C has the effect of stabilizing the arc and making the droplets fine. If C is less than 0.03%, the droplets become large, the arc becomes unstable, and the amount of spatter generated increases. On the other hand, if C exceeds 0.10%, the viscosity of the molten metal becomes low and the molten metal droops, resulting in a poor bead shape. Further, not only the amount of spatter generated increases, but the weld metal is remarkably hardened and crack resistance deteriorates. Therefore, C is 0.03 to 0.10%.

[Si: 0.5 to 1.0%]
Si is indispensable as a main deoxidizer for weld metal and increases the electric resistance of the wire to increase the amount of melting of the wire. In addition, fine inclusions of Si are generated in the molten metal, and the viscosity of the molten metal is increased to obtain a good gap resistance performance. If Si is less than 0.5%, the amount of wire melting is small, the viscosity of the molten metal is also low, and gap resistance cannot be obtained. On the other hand, if Si exceeds 1.0%, the viscosity of the molten metal excessively increases, so that the molten metal cannot follow the high welding speed, and the arc is unstable and tends to be a humping bead. Moreover, since the strength of the weld metal is increased, hot cracking is likely to occur. Therefore, Si is 0.5 to 1.0%.

[Mn: 1.4 to 2.0%]
Mn acts as a deoxidizer like Si, and has the effect of increasing the viscosity of the molten metal and reducing the surface tension. Further, since S is fixed as MnS before a low melting point compound such as FeS is produced, there is an effect of preventing high temperature cracking. If Mn is less than 1.4%, hot cracking is likely to occur, and pore defects such as blow holes are likely to occur, and the molten metal drips and sufficient gap resistance cannot be obtained. Further, since the surface tension is increased and the droplets are coarsened, the amount of spatter generated increases. On the other hand, if Mn exceeds 2.0%, the viscosity of the molten metal excessively increases, so that the molten metal cannot follow the high welding speed, and the arc is unstable and tends to be a humping bead. Therefore, Mn is set to 1.4 to 2.0%.

[Ti: 0.1 to 0.3%]
By containing Ti, oxides (inclusions) in the molten metal increase, viscosity becomes suitable, and gap resistance becomes good. When Ti is less than 0.1%, the viscosity of the molten metal is lowered and gap resistance cannot be obtained. On the other hand, if Ti exceeds 0.3%, the amount of oxide in the molten metal becomes too large to form a convex bead and gap resistance cannot be obtained. Therefore, Ti is 0.1 to 0.3%.

[Bi: 0.01 to 0.1%]
Bi has the effect of reducing the surface tension of the molten metal, thereby improving the smoothness of the bead and the wettability of the bead toe. Moreover, since the surface tension is lowered, the hot water flow in the molten pool can be changed, the slag peelability can be improved, and the bead is widened, so that a good gap resistance performance can be obtained. If Bi is less than 0.01%, it becomes a convex bead, smoothness of the bead and good wettability of the bead toe cannot be obtained, slag peelability is poor, and gap resistance is also deteriorated. On the other hand, if Bi exceeds 0.1%, the arc becomes unstable, the amount of spatter generated increases, and the amount of slag generated further increases. Therefore, Bi is set to 0.01 to 0.1%.

[S: 0.005 to 0.070%]
S has the effect of lowering the surface tension of the molten metal, which can greatly improve the atomization of the droplets, the smoothness of the beads and the wettability of the bead toes. In addition, by reducing the surface tension, it is possible to change the hot water flow in the molten pool and reduce the amount of slag generated. Furthermore, since the bead is wide, a good gap resistance performance can be obtained. is there. If S is less than 0.005%, the effect of improving the bead is insufficient and the gap resistance is poor, and the droplets become large and the arc becomes unstable, resulting in an increase in the amount of spatter generation and slag generation. On the other hand, when S exceeds 0.070%, hot cracking tends to occur. In addition, the surface tension of the droplets is excessively lowered, and the molten metal is liable to sag, and the bead shape is poor particularly in welding with a gap. Therefore, S is made 0.005 to 0.070%.

[P: 0.03% or less, O: 0.01% or less]
If P exceeds 0.03%, the crack resistance of the weld metal deteriorates. On the other hand, if O exceeds 0.01%, the wire surface is cracked at the time of wire production, and the copper plating on the surface of the wire is peeled off at the time of welding, and chip clogging is likely to occur. In addition, the wire for gas shielded arc welding of the thin steel plate of the present invention may be subjected to copper plating with a thickness of 0.3 to 1.1 μm on the wire surface in order to improve rust prevention, electrical conductivity and wire feedability. it can. Others are Fe and inevitable impurities.

Also, short arc welding by CO ₂ welding, MAG welding using Ar—CO ₂ gas, MAG welding using Ar—CO ₂ —O ₂ gas, pulse MAG welding using Ar—CO ₂ gas, and Ar—CO. _In the pulse MAG welding using _2- O ₂ gas, the flow rate of the shielding gas is preferably 20 to 25 liters / minute in order to prevent the defect resistance and the mixing of nitrogen from the atmosphere.

Hereinafter, the effect of the present invention will be described in detail with reference to examples.
A solid wire having a wire diameter of 1.2 mm of various components shown in Table 1 was made as an experiment. As shown in FIG. 2, a JIS G3131 SPCC steel plate having a thickness of 2.0 mm and a length of 450 mm is sandwiched between a rear plate 2 and a front plate 1 with a gap G ₁ = 2 mm and G ₂ = 4 mm. MAG welding was performed under the welding conditions shown in Table 2 using a lateral lap joint in which a gap was formed.

なお、表１に示す化学組成のワイヤ記号１〜８は本発明例、ワイヤ記号９〜１８は比較例である。

In addition, the wire symbols 1-8 of the chemical composition shown in Table 1 are examples of the present invention, and the wire symbols 9-18 are comparative examples.

As shown in FIG. 3, the welding is started from the gap G ₁ (2 mm) side when the wire aiming position 6 is the center of the steel plate thickness on the front plate 1 side, the angle θ of the torch 7 is 30 °, and the gap G ₂ (4 mm The weldable gap was defined as the point where the molten metal could not be cross-linked by welding in the) direction. The weldable gap, arc stability and bead shape of each wire were investigated. The weldable gap was determined to be 3.5 mm or more. Furthermore, spatter, using a copper collecting box, welded five times with welding conditions shown in Table 2 the gap G ₁ of sideways lap joint shown in FIG. 2 as a constant 2 mm, per minute spatter The amount was calculated. A spatter generation amount of 0.5 g / min or less was considered good. The results are summarized in Table 3.

表３中に示すワイヤ記号１〜８が本発明例、ワイヤ記号９〜１８は比較例である。

Wire symbols 1 to 8 shown in Table 3 are examples of the present invention, and wire symbols 9 to 18 are comparative examples.

  Since the wire symbols 1 to 8 of the present invention are appropriate amounts of C, Si, Mn, S, Ti, Bi, the arc is stable, the viscosity and surface tension of the molten metal are appropriate, and the weldable gap is wide. A bead with a small amount of spatter generated and a good appearance was obtained, and there was no occurrence of hot cracking. Since the wire symbol 9 in the comparative example has a large amount of C, the molten metal dripped, the bead shape was poor, the arc was somewhat unstable, the amount of spatter was large, and high temperature cracking occurred. Furthermore, since there was little Ti, the weldable gap was also narrow.

Since the wire symbol 10 has a small amount of C, the arc is unstable and the amount of spatter generated is large. Moreover, since there was much Ti, it became a convex bead and the weldable gap was also narrow. Since the wire symbol 11 has a large amount of Si, the arc is unstable, a humping bead is formed, a weldable gap is narrow, and a high temperature is also generated. Since the wire symbol 12 has less Si, the arc becomes unstable and the weldable gap is narrow. Since the wire symbol 13 had a large amount of Mn, the arc was unstable and a humping bead was formed, and the weldable gap was narrow.

Since the wire symbol 14 has a small amount of Mn, the amount of spatter generated was large. Moreover, the molten metal dripped and the weldable gap was narrow. Furthermore, hot cracking also occurred. Since the wire symbol 15 has a large amount of S, the molten metal dripped and the weldable gap was narrow. Moreover, hot cracking occurred. Since the wire symbol 16 had a small amount of S, the arc was unstable and the bead start end was not well-suited, so that it became a convex bead and the weldable gap was narrow. Also, the amount of spatter generated was large. Since the wire symbol 17 has a large amount of Bi, the arc becomes unstable, and the amount of spatter generation and slag generation is large. Since the wire symbol 18 had a small Bi, it became a convex bead and the fit of the bead toe portion was poor, and the weldable gap was narrow.

1 Front plate 2 Rear plate 3 Weld metal 4 Undercut 5 Spacer 6 Wire target position 7 Torch G, G ₁ , G ₂ gap θ Torch angle


Patent Applicant Nippon Steel & Sumikin Welding Industry Co., Ltd.
Attorney Attorney Shiina and others 1

Claims (1)

In mass% with respect to the total mass of the wire, C: 0.03 to 0.10%, Si: 0.5 to 1.0%, Mn: 1.4 to 2.0%, Ti: 0.1 to 0.3 %, Bi: 0.01 to 0.1%, S: 0.005 to 0.070%, P: 0.03% or less, O: 0.01% or less, and the others are Fe and inevitable impurities A solid wire for gas shielded arc welding of thin steel sheet, characterized by

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