JP2008114264A - Flux cored wire for gas shielded arc welding for atmospheric corrosion resistant steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flux cored wire for gas shielded arc welding for atmospheric corrosion resistance steel which is fine in the arc conditions, small in generation amount of spatters, and in which excellent slag detachability and bead shape are obtained and which is excellent in the mechanical performance of weld metal in the horizontal fillet welding of atmospheric corrosion resistant steel of 400 to 570 N/mm<SP>2</SP>grade. <P>SOLUTION: The wire consists of, by mass to the whole mass of the wire, 2.0-4.0% Ti oxide expressed in terms of TiO<SB>2</SB>, 0.5-1.5% SiO<SB>2</SB>, 0.1-0.6% ZrO<SB>2</SB>, 0.02-0.08% fluoride of the value expressed in terms of F, 0.02-0.08% C, 0.3-0.7% Si, 1.5-2.5% Mn and Mn/Si of 2.5-6.0, 0.15-0.5% Al, 0.15-0.5% Mg and Al/Mg of 0.3-3.0, 0.3-0.7% Ni, 0.45-0.8% Cr, 0.3-0.6% Cu and the balance Fe with an arc stabilizer and inevitable impurities. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to 400~570N / mm ² class gas shielded arc welding flux cored wire for weathering steel, especially in the horizontal fillet welding, good spatter arc state less good slag removability and the good bead The present invention relates to a flux-cored wire for gas shielded arc welding for weathering steel, which has a shape and an excellent weld metal mechanical performance.

  Weather-resistant steel is a steel material in which the surface of the steel material forms a rust layer due to atmospheric corrosion and suppresses corrosion to a deeper layer than that, and is widely applied particularly in the field of steel frames and bridges. Many of these weldings are horizontal fillet position welding, and a flux-cored wire for gas shield arc welding excellent in welding workability is required.

The flux-cored wire for gas shielded arc welding for weathering steel is specified in JIS Z 3320. Appropriate amounts of Ni, Cr, and Cu are used for commonly used mild steel and 490 N / mm grade ² horizontal fillet welding flux-cored wire. Various types of flux-cored wires for welding to which is added are applied.

  For example, an appropriate amount of Ni, Cr and Cu is added to a flux-cored wire component (see, for example, Patent Documents 1 to 3).

  However, when the above-mentioned horizontal fillet welding flux-cored wire added with Ni, Cr and Cu is used, the flowability of the slag is improved, the encapsulation of the slag is deteriorated, and the slag peelability is deteriorated and the bead shape Was bad and was not satisfactory.

  On the other hand, various flux-cored wires for welding weather-resistant steel have been proposed (see, for example, Patent Documents 4 to 6), all of which are flux-cored wires for multilayer prime welding in a downward or vertical posture, When applied to horizontal fillet welding, there is a problem that the weld metal tends to sag and forms a convex bead.

JP-A-2-205299 JP-A-6-285672 JP-A-8-281477 JP 2000-102893 A Japanese Patent Laid-Open No. 2000-287881 JP 2000-317680 A

In the horizontal fillet welding of 400 to 570 N / mm grade ² weatherproof steel, the present invention provides good slag releasability and bead shape with a good arc state and low spatter generation, and mechanical performance of weld metal. An object of the present invention is to provide a flux-cored wire for gas shielded arc welding for weathering steel having excellent resistance.

The inventors applied various flux-cored wires for gas shielded arc welding for weathering steel containing Ni, Cr and Cu to horizontal fillet welding of weathering steel, and the arc state, spatter generation amount, slag peelability In addition, we have intensively studied the effects on bead shape and pit resistance. As a result, the amount of TiO ₂ , SiO ₂ and ZrO ₂ contained in the wire is set appropriately, Mn / Si and Al / Mg are set appropriately, and the amount of generated slag is suppressed, so that the arc state is good. The present invention was completed by finding that a flux-cored wire for gas-shielded arc welding for weatherproof steel with excellent spatter generation and good slag peelability and bead shape and excellent mechanical properties of weld metal was obtained. did.

The gist of the present invention is that, in a flux-cored wire for gas shielded arc welding for weatherproof steel, in which a steel outer shell is filled with a flux, the mass% based on the total mass of the wire, and Ti oxide in terms of TiO ₂ : 2.0 to 4.0%, SiO ₂ : 0.5 to 1.5%, ZrO ₂ : 0.1 to 0.6%, F converted value of metal fluoride: 0.02 to 0.08%, C: 0.00. 02 to 0.08%, Si: 0.3 to 0.7%, Mn: 1.5 to 2.5%, and Mn / Si: 2.5 to 6.0, Al: 0.15 to 0 0.5%, Mg: 0.15-0.5%, and Al / Mg: 0.3-3.0, Ni: 0.3-0.7%, Cr: 0.45-0.8% Cu: 0.3 to 0.6% is contained, and the balance is Fe, an arc stabilizer and inevitable impurities, for gas-shielded arc welding for weather-resistant steel, In the Lux-cored wires.

According to the flux-cored wire for gas shield welding for weathering steel of the present invention, the arc state is good even when applied to horizontal fillet welding of 400 to 570 N / mm grade ² weathering steel, and the amount of spatter generated is high. Less, since the slag is uniformly encapsulated on the bead, excellent slag releasability and bead shape can be obtained. Moreover, the same pit resistance as that of the flux-cored wire for mild steel and 490 N / mm class ² horizontal fillet is obtained, and the mechanical performance of the weld metal is excellent, so that a high-quality weld is obtained.

  The inventors have made various types of flux-cored wires for gas shielded arc welding for weathering steel containing Ni, Cr, and Cu, and applied them to horizontal fillet welding of weathering steel. The effects on slag peelability, bead shape and pit resistance were investigated.

As a result, it was found that by adjusting the amounts of TiO ₂ , SiO _2, and ZrO ₂ to appropriate amounts, the arc is stable, the slag encapsulation is uniform, and the slag peelability is improved. Moreover, it discovered that a favorable bead shape was obtained by making Mn / Si and Al / Mg appropriate. Furthermore, it has been found that excellent pit resistance can be obtained by suppressing the amount of generated slag.

  Hereinafter, the component composition of the flux-cored wire for gas shielded arc welding for weathering steel of the present invention and the reason for limiting the content thereof will be described. In addition, content of each component composition described below is shown by the mass% with respect to the wire total mass.

(TiO ₂ converted value of Ti oxides: 2.0 to 4.0%)
TiO ₂ is a main component of the slag forming agent, and is added from rutile of Ti oxide, titanium oxide, sodium titanate, titanium slag, illuminite, and the like. These have the effect | action which covers the whole bead uniformly and arranges a bead shape. Further, there is an effect that the arc is sustained and stabilized to reduce the amount of spatter generated. If the TiO ₂ equivalent value of the Ti oxide is less than 2.0%, the amount of slag generation is insufficient and the beads cannot be uniformly encapsulated, so that the slag peeling is poor and the bead shape cannot be adjusted. Further, the effect of stabilizing the arc is lost and the amount of spatter generated increases. On the other hand, if it exceeds 4.0%, the arc is stabilized and the amount of spatter generated decreases, but the bead shape hangs down and becomes a convex bead. In addition, the slag becomes thick and gas release is hindered, resulting in poor pit resistance.

_(SiO 2: 0.5~1.5%)
SiO ₂ is added from silica sand, zircon sand or the like and acts as a slag forming agent, and has an effect of increasing the slag viscosity with a small amount. When SiO ₂ is less than 0.5%, there is no effect as a slag forming agent, and the slag encapsulation is deteriorated, and the slag peeling and the bead shape are deteriorated. On the other hand, if it exceeds 1.5%, the viscosity of the slag increases and the gas release is inhibited, so that the pit resistance is deteriorated. Moreover, the arc becomes rough and the amount of spatter generated increases.

(ZrO ₂ : 0.1 to 0.6%)
ZrO ₂ is added from zircon sand, zirconium oxide or the like, and acts as a slag forming agent that improves the slag encapsulation by a small amount and improves the bead shape. By adding ZrO ₂ , the solidification temperature of the slag is increased and the solidification of the slag is accelerated. However, compared to other slag forming agents, the thickness of the generated slag is reduced even if the addition amount is the same. Effective for pit resistance. If ZrO ₂ is less than 0.1%, the slag thickness increases, so the pit resistance deteriorates. On the other hand, if it exceeds 0.6%, the arc becomes rough and the amount of spatter generated increases, and the slag becomes hard and it becomes difficult to uniformly encapsulate the slag in the bead, so that the slag peelability is deteriorated.

(F value of metal fluoride: 0.02 to 0.08%)
F is added from sodium fluoride, potassium silicofluoride, cryolite, aluminum fluoride, lithium fluoride, fluorite, etc., and improves the stability of the arc. If the F-converted value of the metal fluoride is less than 0.02%, the arc concentration becomes weak and a stable arc state cannot be obtained. On the other hand, if it exceeds 0.08%, the arc becomes rough and the generation amount of fume and spatter increases.

(C: 0.02-0.08%)
C is one of important elements that are added from a steel outer shell, Fe-Mn, graphite and the like and adjust the strength of the weld metal. When C is less than 0.02%, the strength and toughness of the weld metal are lowered. On the other hand, if it exceeds 0.08%, the arc becomes too strong and the amount of spatter generated increases. In addition, the strength of the weld metal increases and the toughness decreases.

(Si: 0.3-0.7%)
Si is added from metals Si, Fe-Si, Fe-Si-Mn, and the like, and is added to act as a deoxidizer to ensure the strength and toughness of the weld metal. If Si is less than 0.3%, deoxidation is insufficient, and welding defects such as pits occur in the welded portion. In addition, strength and toughness are reduced. On the other hand, if it exceeds 0.7%, the strength of the weld metal increases and the toughness decreases.

(Mn: 1.5-2.5%)
Mn is added from metal Mn, Fe-Mn, steel outer shell, etc., and acts to act as a deoxidizer and to ensure the strength and toughness of the weld metal. If Mn is less than 1.5%, deoxidation is insufficient, and welding defects such as pits occur in the weld. Moreover, the strength and toughness of the weld metal are reduced. On the other hand, if it exceeds 2.5%, the strength of the weld metal increases and the toughness decreases.

(Mn / Si: 2.5-6.0)
Mn / Si affects the viscosity of the weld metal. As Mn / Si increases, the viscosity of the weld metal decreases. Conversely, when Mn / Si decreases, the viscosity of the weld metal increases. When the viscosity of the weld metal is lowered, the gas generated from the weld metal is quickly released, so that the pit resistance can be improved. If Mn / Si is less than 2.5, the amount of Mn with respect to Si is reduced, so that toughness deteriorates. On the other hand, if it exceeds 6.0, the viscosity of the weld metal becomes too low and the bead shape becomes convex.

(Al: 0.15-0.5%)
Al is added from metals Al, Fe—Al, Al—Mg, and the like, and acts as a deoxidizer and has the effect of adjusting the strength and toughness by increasing the yield of Si and Mn into the weld metal. Moreover, it has the effect of increasing the viscosity of the weld metal and has the effect of adjusting the bead shape. If the Al content is less than 0.15%, the effect as a deoxidizer is small, and welding defects such as pits occur in the welded portion. In addition, the bead shape deteriorates because the viscosity of the weld metal decreases. On the other hand, if it exceeds 0.5%, the concentration of arc becomes too high and the amount of spatter generated increases. Further, the strength becomes too high and the toughness is lowered.

(Mg: 0.15-0.5%)
Mg is added from metals such as Mg and Al—Mg, and acts as a deoxidizer and has the effect of adjusting the strength and toughness by increasing the yield of Si and Mn to the weld metal. If Mg is less than 0.15%, there is no effect as a deoxidizing agent, and welding defects such as pits occur in the weld. On the other hand, if it exceeds 0.5%, the arc becomes rough and the amount of spatter generated increases.

(Al / Mg: 0.3-3.0)
Al / Mg affects the viscosity of the weld metal. If Al / Mg is increased, the viscosity of the weld metal is increased. Conversely, if Al / Mg is decreased, the viscosity of the weld metal is decreased. If Al / Mg is less than 0.3, the viscosity of the weld metal becomes low, and the bead shape drips. On the other hand, if it exceeds 3.0, the toughness decreases.

(Ni: 0.3-0.7%, Cr: 0.45-0.8%, Cu: 0.3-0.6%)
Ni, Cr, and Cu are added from metal Ni, metal Cr, metal Cu, and the like, and are essential for the weld metal to have weather resistance performance. When Ni is less than 0.3%, Cr is less than 0.45% and Cu is less than 0.3%, the weather resistance performance cannot be satisfied. On the other hand, if Ni exceeds 0.7%, Cr exceeds 0.8% and Cu exceeds 0.6%, the strength becomes too high. Also, the cost is too high and it is not economical.

  Hereinafter, the effect of the present invention will be described in more detail with reference to examples.

  First, JIS G3141 SPCC band steel was used for the steel outer sheath, and various flux-cored wires for gas shield arc welding having various wire diameters of 1.2 mm shown in Table 1 were produced.

  Using a flux-cored wire for gas shielded arc welding shown in Table 1, a weather-resistant steel plate (JIS G3114 SMA490BW) having a thickness of 12 mm was used as a T-shaped fillet specimen (length 1000 mm). Horizontal fillet welding was performed under the welding conditions of No. 1, and the arc state, spatter generation amount, slag peelability, and bead shape were investigated. For the measurement of the amount of spatter generated, the total amount of spatter generated was collected and converted to the amount generated per minute. Note that the amount of spatter generated in the weather-resistant steel plate is preferably 2 g / min or less.

  In addition, the evaluation of pit resistance was carried out by using a 12 mm-thick inorganic zinc primer coated steel sheet (JIS G3114 SMA490BW, primer film thickness 35-40 μm) as a T-shaped fillet specimen (length 1000 mm). Condition No. shown in FIG. Horizontal fillet welding was performed under the welding conditions of 1 and the number of generated pits was investigated.

Furthermore, a weld metal test using a weather-resistant steel plate (JIS G3114 SMA490BW) having a thickness of 20 mm according to JIS Z 3320 was conducted under the condition No. 1 shown in Table 2. The test was conducted under the welding conditions of No. 2, and a tensile test piece and an impact test piece were collected and tested. The tensile strength was 490 N / mm ² or more, and the absorbed energy was 70 J or more at 0 ° C. The survey results are summarized in Table 3.

In Table 3, wire No. 1 to 10 are examples of the present invention, wire Nos. 11 to 21 are comparative examples. Wire No. which is an example of the present invention. 1 to 10 are appropriate for TiO ₂ equivalent value of Ti oxide, SiO ₂ , ZrO ₂ , F equivalent value of metal fluorine compound, C, Si, Mn, Al, Mg, Mn / Si and Al / Mg. The results were extremely satisfactory, such as good arc condition, small amount of spatter generation, good slag removability and bead shape, no pits, and good mechanical performance.

In the comparative example, the wire No. No. 11 had a large TiO ₂ conversion value of Ti oxide, so the bead shape was poor and pits were generated. Moreover, since Mn / Si was low, the absorbed energy was low.
Wire No. In No. 12, since the TiO ₂ conversion value of the Ti oxide was small, the arc was unstable, the slag peelability and the bead shape were poor, and the amount of spatter was large. Further, since there was little Si, pits were generated, and the tensile strength and absorbed energy of the deposited metal were low.

Wire No. No. 13 has a large amount of sputter due to a large amount of SiO ₂ , and pits were also generated. Moreover, since Al / Mg was high, the absorbed energy of the weld metal was low.

Wire No. No. 14 had poor slag removability and bead shape because of low SiO ₂ . Moreover, since Mn was small, pits were generated, and the tensile strength and absorbed energy of the deposited metal were low.

Wire No. No. 15 had a large amount of spatter due to a large amount of ZrO ₂ , and the slag removability was poor. Further, since C is small, the tensile strength and absorbed energy of the deposited metal were low.

Wire No. No. 16 had pits because ZrO ₂ was small. Moreover, since Al was high, the amount of spatter was large, the tensile strength of the deposited metal was high, and the absorbed energy was low.

  Wire No. No. 17 had a large amount of spatter generation because the F-converted value of the metal fluorine compound was large. Moreover, since Mn was high, the tensile strength of the deposited metal was high and the absorbed energy was low.

  Wire No. In No. 18, the arc was unstable because the F-converted value of the metal fluorine compound was small. Further, since the Al content was small, the bead shape was poor and pits were generated.

  Wire No. No. 19 had a high amount of spatter due to high C, and the weld metal had high tensile strength and low absorbed energy. Moreover, since Al / Mg was low, the bead shape was also poor.

  Wire No. No. 20 had a high tensile strength of the weld metal and a low absorbed energy because of the large amount of Si. Moreover, since there was little Mg, the bead shape was bad and the pit was also produced.

  Wire No. No. 21 has a large amount of spatter due to a large amount of Mg. Moreover, since Mn / Si was high, the bead shape was poor.

Claims (1)

In a flux-cored wire for gas shielded arc welding for weatherproof steel, which is formed by filling a steel outer shell with flux,
TiO ₂ conversion of Ti oxide: 2.0 to 4.0%,
SiO _2: 0.5~1.5%,
ZrO ₂ : 0.1 to 0.6%,
F converted value of metal fluoride: 0.02 to 0.08%,
C: 0.02 to 0.08%,
Si: 0.3-0.7%,
Mn: 1.5 to 2.5%
And Mn / Si: 2.5-6.0,
Al: 0.15 to 0.5%,
Mg: 0.15 to 0.5%,
And Al / Mg: 0.3-3.0,
Ni: 0.3-0.7%,
Cr: 0.45 to 0.8%,
A flux-cored wire for gas-shielded arc welding for weathering steel, characterized by containing Cu: 0.3 to 0.6%, and the balance being Fe, an arc stabilizer and inevitable impurities.