KR101637471B1 - Flux cored wire for Gas shielded arc welding - Google Patents

Abstract

The present invention provides a flux and an envelope surrounding the flux for a gas-filled arc welding flux welding wire having good cryogenic impact toughness and excellent CTOD value and electron weldability, the flux comprising a total weight By weight of titanium oxide, from 3.5 to 8.0% by weight of titanium dioxide, from 0.03 to 0.12% by weight of carbon, from 0.2 to 1.0% by weight of silicon, from 1.0 to 2.5% by weight of manganese, from 1.0 to 2.9% (FeTi ₂ O ₅ ), 0.01 wt% or less (greater than 0 wt%) of vanadium, 0.005 wt% or less of vanadium, 0.005 wt% or less of vanadium, (% By weight) of niobium, 0.2 to 0.8% by weight of silicon dioxide, and inevitable impurities.

Description

[0001] Flux cored wire for gas shielded arc welding [0002]

The present invention relates to a flux-charging wire for welding, and more particularly to a flux-charging wire for gas-shielded arc welding.

Recently, the extraction of gas and natural gas from offshore has been increasing in the offshore plant. Since the enormous amount of offshore plant is welded, the standards for safety of welds are constantly complicated, which is comparable to the aerospace sector. In particular, it has become a very urgent task to secure a stable weld at a cryogenic temperature. As a method for evaluating the stable performance of welds at low temperature, there is a method of measuring low temperature impact value and CTOD (Crack tip opening displacement) value, but CTOD value at low temperature is emerging as a more important evaluation standard.

However, titania-based flux-filled wires, which are generally excellent in electron weldability, are acidic such as TiO ₂ , so that welding workability is good, but cryogenic toughness lowers and low-temperature CTOD values tend to decrease. In order to compensate for the disadvantages of such titania-based flux-charging wires, the prior art attempts to secure a low-temperature toughness by filling the basic flux of TiO ₂ -CaF ₂ system. However, the workability is deteriorated and it is difficult to secure a low temperature CTOD. Have.

On the other hand, Korean Patent Application No. 10-2012-0014412 and Korean Patent Application No. 10-2012-0153867 disclose that the ratio of C, Si, Mn, Ti, Ni, Mo, Y and REM and the formation of carbide prebenite The CTOD value is unstable due to insufficient control of the martensite which is vulnerable to fracture toughness, and the latter has insufficient control of the martensite.

Another method for ensuring excellent toughness at low temperatures is to reduce the oxygen content in the weld metal. The technology developed in view of this is a technique for limiting the ratio of metal iron to total iron as well as trace elements in the welding wire. Although this technology is being used to produce wires with excellent low temperature toughness, these techniques are too biased to reduce the amount of oxygen in the deposited metal, which can easily cause hardening of welds and can not form a uniform overall structure. There is a limit.

In addition, the most effective method for improving the CTOD characteristics is to maximize the acicular ferrite fraction in the welded structure. The present inventors have found that the Korean patent application No. 10-2012-0121638 discloses a gas shielded arc welding method in which the percentage of acicular type ferrite is increased by using a trace component and oxygen in the iron powder to provide a cryogenic impact toughness and a CTOD value and excellent electron weldability Although it has been reported to provide flux-filled wires, it has a limit to have a stable CTOD value at low temperatures.

 It is an object of the present invention to provide a flux-charging wire for gas shielded arc welding which is excellent in cryogenic impact toughness and excellent in CTOD value and electron weldability, for solving various problems including the above-mentioned problems. However, these problems are exemplary and do not limit the scope of the present invention.

A flux-charging wire for gas-shielded arc welding according to one aspect of the present invention comprises a flux and an envelope surrounding the flux, the flux comprising 3.5 to 8.0 wt% titanium dioxide, From about 0.03 to about 0.12 weight percent carbon, from about 0.2 to about 1.0 weight percent silicon, from about 1.0 to about 2.5 weight percent manganese, from about 1.0 to 2.9 weight percent nickel, from 0.2 weight percent to 1.5 weight percent magnesium, from 0.1 weight percent to 0.6 weight percent titanium, (FeTi ₂ O ₅ ), 0.01 wt% or less (0 wt% or more) of vanadium, 0.005 wt% or less (0 wt% or more) of niobium, 0.02 wt% or less of boron, 0.05-0.7 wt% 0.2 to 0.8% by weight of silicon dioxide and inevitable impurities.

In the flux-cored wire for gas-shielded arc welding, the content of the pseudobromocite, silicon dioxide, and titanium dioxide may satisfy the following formula (1).

Equation 1:

0.7 ≤ {((2 × mass of pseudodruckite) + (10 × mass of silicon dioxide)) / (of titanium dioxide Mass)} ^1/2 < ^{/ =} 1.3

In the flux-cored wire for gas-shielded arc welding, the flux may include those having a particle size distribution of 75 to 500 占 퐉 in 80% or more of the flux.

According to an embodiment of the present invention, as described above, the present invention has been made to solve the problems of the prior art described above, and has an excellent impact toughness at a cryogenic temperature and an excellent CTOD value and electron weldability. Of course, the scope of the present invention is not limited by these effects.

FIG. 1 is a photograph (B) of a case where the low temperature impact value and the CTOD value are improved and the f value satisfies the technical idea of the present invention when the low temperature impact value and the CTOD value are insufficient .
Fig. 2 is a photograph showing an acicular type ferrite formed from titanium oxide (III) according to Experimental Example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Also, for convenience of explanation, the components may be exaggerated or reduced in size.

The present invention relates to a flux filled wire for gas shielded arc welding comprising a flux and an envelope surrounding said flux, said flux comprising 3.5 to 8.0 wt% titanium dioxide, 0.03 to 0.12 wt% From about 0.2 to about 1.0 weight percent silicon, from about 1.0 to about 2.5 weight percent manganese, from about 1.0 to 2.9 weight percent nickel, from 0.2 to 1.5 weight percent magnesium, from 0.1 to 0.6 weight percent titanium, from 0.003 to 0.02 weight percent boron, (FeTi ₂ O ₅ ), 0.01 wt% or less (0 wt% or more) of vanadium, 0.005 wt% or less (0 wt% or more) of niobium, 0.2-0.8 wt% Silicon dioxide, and inevitable impurities. The present invention provides a flux-charging wire for gas-shielded arc welding.

The flux-charging wire for gas-shield arc welding can be termed a cored wire for gas-shield arc welding.

Hereinafter, the role of each constituent component of the flux in the flux-filling wire for gas shielded arc welding of the present invention will be described in detail and the technical significance of the numerical limitation of each constituent component will be described in detail.

The carbon (C) among the constituent components of the present invention may contain, for example, 0.03 to 0.12% by weight. If the content of carbon is less than 0.03% by weight, the effect of adding carbon can not be expected. If the content of carbon is more than 0.12% by weight, the strength is excessively increased, and the weld metal may be hardened to cause cracking. As a result, when the content of carbon is out of the range of 0.03 to 0.12% by weight, the toughness and CTOD (Crack tip opening displacement) value may be deteriorated.

In addition, the carbon within the above range can not only provide the necessary strength to the wire but also slow down the growth rate of grain boundary ferrite in the austenite grain plane, thereby preventing coarsening of the structure. Furthermore, It is possible to prevent penetration of inclusions (MnS, Al ₂ O ₃ , SiO _2, etc.) into the inside of the weld metal, thereby obtaining a sound weld.

The silicon (metal Si) may include, for example, 0.2 to 1.0% by weight. The silicon can reduce the amount of oxygen in the deposited metal and improve the cleanliness of the deposited metal in an appropriate range as a strong deoxidizer. In addition, the viscosity of the welding slag can be maintained, and the electronic workability can be facilitated. However, when the content of silicon is less than 0.2% by weight, deoxidation is insufficient, resulting in poor work performance and poor bead appearance. If the silicon content is more than 1.0% by weight, a large amount of spatter is generated, and the slag surface overflows and the toughness of the weld metal tends to be lowered.

The manganese (Mn) may, for example, comprise from 1.0 to 2.5% by weight. The manganese improves the strength of the wire and can be added as a deoxidizer to reduce the amount of oxygen in the deposited metal. However, if the content of manganese is less than 1.0 wt%, not only the weld bead property may deteriorate but also the strength and toughness of the weld metal may be deteriorated. If the content of manganese exceeds 2.5% by weight, the arc is unstable, the melting property is decreased, and high temperature cracks are generated, so an appropriate range for strength improvement is required.

Magnesium (Mg) may include, for example, 0.2 to 1.5% by weight. The magnesium reacts with oxygen in the molten metal as a deoxidizing agent to inhibit the formation of nonmetallic inclusions and improve the cleanliness of the weld metal. If the content of magnesium is also less than 0.2% by weight, an excellent effect of low temperature toughness and CTOD value according to the content can not be expected. If the content of magnesium exceeds 1.5% by weight, the amount of welding fumes and spatter is increased and the workability of the electronic degreasing is deteriorated.

The boron (B) may include, for example, 0.003 to 0.02% by weight. The boron may be added as a trace element to refine the structure and inhibit the growth of intergranular ferrite, thereby improving the low temperature toughness and the CTOD property. If the content of boron is less than 0.003% by weight, the effect of the boron to make the structure finer is not realized. If the content of boron exceeds 0.02% by weight, the hardness of the welded portion may be excessively increased to cause cracking.

Nickel (Ni) may include, for example, 1.0 to 2.9 wt%. The nickel may lower the impact transition temperature of the weld metal to stabilize low-temperature toughness and fine structure to improve CTOD characteristics. However, if the content of nickel is less than 1.0% by weight, an effect depending on the content can not be expected. If the content of nickel exceeds 2.9 wt%, the strength of the weld metal excessively increases, and toughness and CTOD characteristics may be deteriorated.

Titanium (Ti) may, for example, comprise from 0.1 to 0.6% by weight. The titanium reacts with oxygen and nitrogen in the molten metal as a deoxidizing agent to improve the cleanliness of the weld metal and to refine the structure. If the content of titanium is less than 0.1% by weight, the effect due to the content can not be expected. If the content of titanium exceeds 0.6% by weight, the amount of welding fume and spatter may be increased. Further, it is necessary to adjust the composition ratio because it deteriorates the workability of the electronic aging and causes cracks.

Titanium dioxide (TiO ₂ ) may include, for example, 3.5 to 8.0 wt%. Titanium dioxide is the main component of the flux, which can stabilize the arc and form a beautiful bead appearance as a main slag forming agent. In addition, it is possible to provide a good welding workability of electron beam. Further, after dissociation with titanium (Ti) and oxygen (O ₂ ) during the welding process, the oxide such as titanium oxide (III) (Ti ₂ O ₃ ) is reformed to serve as nucleation site of needle- Some may remain in the weld in the form of titanium dioxide or float as slag.

If the content of titanium dioxide is less than 3.5% by weight, the electric arc weldability may deteriorate due to arc instability and excessive spattering. If the content of the titanium dioxide exceeds 8.0 wt%, the flowability of the slag may become poor. In addition, it is necessary to limit the range of the mass fraction of the titanium dioxide, since the inclusion of slag in the deposited metal can be caused to greatly lower the toughness and hinder the CTOD characteristics.

Silicon dioxide (SiO ₂ ) stabilizes the arc and improves the flowability of the slag to form a beautiful bead appearance, and can impart good welding workability in electronic aging.

If the content of silicon dioxide is less than 0.2% by weight, the flowability of the slag may be deteriorated and the bead appearance may be uneven and the welding workability may be deteriorated. If the content of silicon dioxide exceeds 0.8% by weight, the flowability of the slag may be excessively increased to cause bead streaking and considerably lower the toughness, thereby deteriorating the CTOD characteristics.

In addition, the silicon dioxide can be easily dissociated into silicon (Si) and oxygen (O ₂ ) during the welding process. At this time, dissociated oxygen (O ₂ ) reacts with titanium (Ti) to form titanium oxide (III) (Ti ₂ O ₃ ) and the remaining part remains in the welded part in the form of silicon dioxide or floats as slag.

Blood establish Fig brookite (FeTi ₂ O ₅₎ is a very important post element dissociated as a titanium (Ti) and oxygen (O ₂₎ of the welding process, the first titanium dioxide than the titanium dioxide (Ⅲ) (Ti ₂ O In the present invention, ₃ ) to form a nucleation site of needle-like ferrite. When the content of the fusidobrukite is less than 0.05 wt%, the effect of forming the needle-like ferrite is insufficient. If the content of the pseudo broucite is more than 0.7% by weight, slag inclusion in the deposited metal may be caused to lower the toughness, thereby deteriorating the CTOD characteristics. Therefore, it is necessary to limit the range of the mass fraction of the above-mentioned pseudo-brucite.

 The more important role of the above-mentioned pseudo brookite and silicon dioxide is to supply a sufficient amount of oxygen necessary for titanium dissociated from titanium dioxide to precipitate into titanium oxide (III). That is, the pseudo broucite and the silicon dioxide component are most easily reacted because the dissociation energy of oxygen is relatively low, so that the two components are advantageously used as an oxygen source.

For such a role, the content of the above-mentioned brookite may include, for example, 0.05 to 0.7% by weight. Strictly from 0.07 to 0.5% by weight, for example.

Niobium (Nb) and vanadium (V) can be added as impurities. The niobium and the vanadium may precipitate at the crystal grain boundaries to promote solid solution strengthening and increase the strength of the welded portion. However, when the niobium and the vanadium exceed a certain mass fraction, the low temperature toughness and the CTOD value can be lowered due to irregular precipitation in grain boundaries in the form of carbide or nitride. For example, the niobium needs to have a mass fraction of more than 0 and less than 0.005 wt%, and a vanadium content of more than 0 and less than 0.01 wt%.

The composition may further include a composition for controlling the content ratio between the above-mentioned persulphate, silicon dioxide, and titanium dioxide to a predetermined value. If the content ratio is kept within a certain range, acicular ferrite can be abundantly produced. As a result, the weld metal becomes very dense, so that not only the low temperature toughness is excellent but also the weld metal having excellent CTOD characteristics can be provided.

Titanium oxide III (Ti ₂ O ₃ ) serving as a nucleation site for acicular ferrite to produce the acicular ferrite is formed by dissolving titanium and pseudodourucite dissociated from pseudodorucite and titanium dioxide, Dissociated oxygen can be formed by reaction. However, the value of f, which is the square root value of ((mass of 2 × pseudodruckite) + (mass of silicon dioxide) / (mass of titanium dioxide), is strictly in the range of 0.7 to 1.3 May be required.

The reason for limiting the f value to a certain range is that if the f value is less than 0.7, the oxygen content is insufficient to form a sufficient amount of needle-like ferrite. If the f value is more than 1.3, Ti is insufficient and a sufficient amount of needle- There is a problem that it can not be formed. In addition, since there is a problem that the toughness can be lowered by forming a non-metallic inclusion due to an excessive amount of oxygen, it is necessary to maintain the composition ratio of, for example, 0.7 to 1.3.

Further, in order to obtain a flux-charging wire for gas-shielded arc welding having a low temperature toughness and a good CTOD value, for example, a particle size distribution of 85% or more of the flux may be limited to a range of 75 to 500 mu m.

 FIG. 1 is a photograph (B) of a case where the low temperature impact value and the CTOD value are improved and the f value satisfies the technical idea of the present invention when the low temperature impact value and the CTOD value are insufficient . Referring to FIG. 1, it can be seen that the tissue photograph of (A) is outside the scope of the technical idea of the present invention, so that the tissue (A) with insufficient low temperature toughness can be identified. The structure (B) having excellent toughness and excellent CTOD characteristics can be identified.

Fig. 2 is a photograph showing an acicular type ferrite formed from titanium oxide (III) according to Experimental Example of the present invention. Referring to FIG. 2, it can be confirmed that needle-like ferrite is finely generated from titanium oxide (III) (dotted line portion).

Hereinafter, experimental examples are provided to facilitate understanding of the present invention. It should be understood, however, that the following examples are for the purpose of promoting understanding of the present invention and are not intended to limit the scope of the present invention.

(Experimental Example)

Table 1 shows the flux cored wire for gas shield arc welding of 1.2 mm in diameter having the composition shown in Table 1 below, and the sheath composition of the wire used was expressed as% by weight with respect to the wire.

<Table 3> shows the specific welding condition of V-type modified butt welding for the base material in the API 5L 2W 60 steel with 80mm thickness by using each wire prepared in this way.

Table 4 shows the results of welding workability, weld toughness and CTOD results for each wire after welding.

In the meantime, in one experimental example of the present invention, the welding workability was judged visually in consideration of bead shape and the like and classified into four stages of very good (⊚), excellent (◯), normal (△) Respectively. The impact test was carried out at -80 ° C. The CTOD test was carried out at -30 ° C. according to the BS 7448 standard. The result of 0.25 or more was accepted. The values are shown in Table 4 below .

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (3)

A flux-charging wire for gas-shielded arc welding,
Flux; And
And an envelope surrounding said flux,
Wherein the flux comprises at least one selected from the group consisting of 3.5 to 8.0 wt% titanium dioxide, 0.03 to 0.12 wt% carbon, 0.2 to 1.0 wt% silicon, 1.0 to 2.5 wt% manganese, 1.0 to 2.9 wt% (FeTi ₂ O ₅ ), not more than 0.01 wt% of nickel, 0.2 to 1.5 wt% of magnesium, 0.1 to 0.6 wt% of titanium, 0.003 to 0.02 wt% of boron, 0.05 to 0.7 wt% of fesudo brookite (Greater than 0 weight percent) of vanadium, 0.005 weight percent or less (greater than 0 weight percent) of niobium, 0.2 to 0.8 weight percent silicon dioxide, and inevitable impurities. The method according to claim 1,
The flux-cored wire for gas shielded arc welding according to claim 1, wherein the content of the fused copper, silicon dioxide and titanium dioxide satisfies the following formula (1).
Equation 1:
0.7 ≤ {((2 × mass of pseudodruckite) + (10 × mass of silicon dioxide)) / (of titanium dioxide Mass)} ^1/2 &lt; ^{/ =} 1.3 The method according to claim 1,
The flux-charging wire for gas-shielded arc welding, wherein the flux comprises a particle size distribution of 75 to 500 占 퐉 in 80% or more of the flux.

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