KR19990015625A - Flux Filling Wire for Arc Welding - Google Patents

Abstract

Flux-filled wire for arc welding is provided having excellent toughness such as high Charpy absorbed energy and CTOD values in the range of about -60 ° C to -80 ° C for the weld specification and the PWHT specification and excellent processability in the electronic world. This flux welding wire for arc welding is 3.0 to 9.0 wt% titanium oxide (based on TiO ₂ ), 0.1 to 0.8 wt% Mg, B 0.001 to 0.03 wt%, Mn 1.0 to 3.0 wt% and Si 0.1 to the total weight of the wire. To 1.2 wt%, Nb and V contained in the wire are adjusted to Nb 0.0120 wt% or less, V 0.0200 wt% or less with respect to the total weight of the wire, and the metal iron contained in the flux is 5 to the total weight of the flux. 50 wt% and the ratio of metal iron to total iron satisfies the formula [metal iron (wt%) / total iron (wt%)] ≥ 0.85.

Description

Flux Filling Wire for Arc Welding

Field of invention

The present invention relates to flux filled wire filled with titania-based fluxes for arc welding, and more particularly to the present invention is a material specification as welded (hereinafter referred to as a "weld specification") and a material specification requiring post-weld heat treatment. A flux-filled wire for arc welding with good weldability and low temperature stability to electron beam welding, applicable to "PWHT specifications".

Description of Background

Recently, as the development of energy resources has been extended to far polar regions and deep seas, steel materials and welding materials having excellent low temperature toughness have been strongly demanded. In this respect, titania-based flux-filled wires for gas-sealed arc welding have excellent weldability and effectiveness against electric field welding, but contain a large amount of oxide such as TiO ₂ as a slag forming agent to generate acidic slag. For this reason, the oxygen content in the welded metal is generally high at 700 to 900 ppm by weight, and in terms of toughness, the weld specification is applicable only to the lowest temperature region of about -30 ° C. As an alternative, the basic wire has good low temperature toughness in either the weld specification or the PWHT specification because the oxygen level in the molten metal obtained is relatively low compared to the toughness of the titania-based flux filled wire, but the workability for electron beam welding is much poorer.

As shown in Japanese Patent No. 1,407,581 in recent years, a technique for realizing the application of titania-based flux filled wire to low temperature specifications from -60 ° C to -80 ° C has been alloyed therein, such as Ti, B, Mg and Ni. Although developed due to the synergistic effects of the components, strictly speaking this technique is mainly suitable for weld specifications. Therefore, this technique is not satisfactory for applications in applications requiring improved toughness, such as stress relief annealing (hereinafter referred to as "SR").

Moreover, Japanese Patent Application Laid-Open No. 5-45360 increases the amount of fluoride applied to the flux-filled wire to improve low temperature toughness, including COD characteristics, but this increases the volume of welded fuse and spatter generated. In addition, the use of CaF ₂ and BaF ₂ increases the basicity of the slag, which severely degrades the weldability in the vertical position. Therefore, this prior art can hardly be applied to the electric field welding.

The present inventors have already found a technique which has good low temperature toughness and good processability in the electronic world, both in the specification of welding only and in the PWHT specification, which consists of limiting trace metals remaining in the weld metal (eg Nb, V and P). (Japanese Patent Laid-Open No. 8-10982).

However, the inventors have continued to work on this state of the art, yet the low temperature toughness at -60 ° C to -80 ° C is not satisfactorily stable and in some cases the desired low temperature toughness cannot be obtained in practical applications. It has been proved that there is a possibility of causing a stain.

The present invention has been made in view of the above problems. It is an object of the present invention to provide a flux filling wire for arc welding that is sufficiently stable at low temperature toughness at -60 ° C to -80 ° C for both specifications of the weld specification and the PWHT specification and is excellent in workability in the electronic world.

1 is a graph showing the relationship between the ratio of ferrous metal (wt%) / total iron (wt%) in the flux and oxygen content in the weld metal or absorbed energy of the weld metal;

2 is a graph (horizontal coordinate axis; logarithmic scale) showing the relationship between the Nb content in the wire and the absorbed energy of the weld metal;

3 is a graph showing the relationship between the V content in the wire and the absorbed energy of the weld metal;

4 is a graph showing the relationship between the P content in the wire and the absorbed energy of the weld metal;

5A-D illustrate cross-sectional shapes of flux filling wires.

Summary of the Invention

The flux filling wire for arc welding according to the present invention is prepared by filling the steel shell with flux, and based on the total weight of the wire, titanium oxide (based on TiO ₂ ) 3.0 to 9.0 wt%, Mg 0.1 to 0.8 wt%, B 0.001 to 0.03 wt%, Mn 1.0 to 3.0 wt% and Si 0.1 to 1.2 wt%, and Nb and V contained in the wire are adjusted to Nb 0.0120 wt% or less, V 0.0200 wt% or less relative to the total weight of the wire, and The metal iron contained in the flux is 5 to 50 wt% with respect to the total weight of the flux and the ratio of metal iron to total iron satisfies the formula [metal iron (wt%) / total iron (wt%)] ≧ 0.85.

Preferably, the total water content is adjusted in the range of 20 to 1000 ppm by weight (KF method at 750 ° C. in O ₂ atmosphere), and the P in the impurity is 0.030 wt% or less relative to the total weight of the wire. Also preferably the wire contains from 0.01 to 0.30 wt% of metal fluoride, based on the fluoride, and up to 9.0 wt% of oxide containing TiO ₂ , based on the total weight of the wire.

Furthermore, the wire preferably contains 0.3 to 5.0 wt.% Ni with respect to the total weight of the wire while the flux packed therein has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 μm or less.

Detailed description of the invention

In order to overcome the above problem, the present inventors have repeatedly performed various experiments and research work. The inventors found that a further reduction in the oxygen content in the weld metal is effective to stabilize the low temperature toughness in both the weld specification and the PWHT specification. Accordingly, the present inventors have found that the ratio of metal iron to total iron in the flux [metal iron (wt%) / total iron (wt) as a means of further reducing the oxygen content in the weld metal than the reduction by the technique disclosed in Japanese Patent Laid-Open No. 8-10982. %)] Was found to be effective.

The difference between iron and metal iron in the flux corresponds to the iron compound therein, mainly composed of iron oxide. The iron oxide acts as a factor that greatly affects the oxygen content in the weld metal, and by adjusting the content, the oxygen content in the weld metal is further suppressed to a lower level, whereby low temperature toughness can be stabilized and improved.

As used herein, the term "metal iron" refers to the various iron alloys (Fe-Mn, Fe-Ti, Fe-B, etc.) contained in the flux and all metal iron components contained in the iron powder. In addition, the impurities contained in these flux materials are mainly oxides such as iron oxides. Therefore, according to the present invention, the ratio of [metal iron (wt%) / total iron (wt%)] should be 0.85 or less. This limitation reduces the oxygen content in the weld metal. Even if the range of impurity elements as disclosed in Japanese Patent Laid-Open No. 8-10982 is expanded, satisfactory low-temperature toughness can be obtained in both specifications of the weld specification and the PWHT specification. In other words, it can be newly discovered that the low temperature toughness in both specifications can never be degraded even if Nb is not present in the weld metal.

The present invention provides the toughness required to build an ice-covered marine offshore structure and LPG and LNG vessels, such as Charpy impact and COD values, in the weld and PWHT specifications in the temperature range of about -60 ° C to -80 ° C. At the same time, to provide a flux-filled wire excellent in workability during the electric field welding.

The reason why a certain component should be applied to the flux filling wire for gas shielded arc welding according to the present invention and the composition of the flux filling wire should be described below.

The present inventors intensively experimented with various flux filling wires having different compositions by welding tests and compared their performance. The test wire had a wire diameter of 1.2 mm and had a shape as shown in FIG. 5A. The flux ratio was 15 wt%. Welding tests were performed using wires of the compositions shown in Table 1. Welding conditions were as follows.

1. Charpy impact test (according to JIS Z3111)

Polarity: DCEP

Welding current: 280A

Welding voltage: 29A

Test steel plate: BS4360, Gr50D

Sealed gas: 80% Ar-20% CO ₂ , flow rate 25 liters / minute

Other: Welding according to JIS Z3313

2.COD test (according to BS7448-1991)

Polarity: DCEP

Welding current: 180-250A

Welding voltage: suitable amount

Test steel plate: BS4360, Gr500D, plate thickness 40mm, X-bevel angle 50。K

Sealed gas: 80% Ar-20% CO ₂ , flow rate 25 liters / minute

1, 2 and 3 show the results of the Charpy impact test and the COD test of the weld metal. FIG. 1 shows the relationship between the metal iron (wt%) / total iron (wt%) on the abscissa and the Charpy impact value or the oxygen content in the weld metal on the ordinate. As shown in FIG. 1, when the ratio of ferrous (wt%) / total iron (wt%) is ≧ 0.85, the oxygen content in the weld metal is greatly reduced, and the toughness is surprisingly improved.

2 and 3 show graphs showing the relationship between Nb and V content and toughness, where the ordinate axis represents the Charpy impact value and the abscissa axis represents the Nb content in the wire or the V content in the wire. The Charpy impact value is particularly high at Nb 0.0120 wt% or less and V 0.0200 wt% or less. Unlike the toughness described in Japanese Patent Laid-Open No. 8-10982, the absolute value of the toughness itself is improved. In particular, good low temperature toughness can be obtained in both specifications even if Nb is not present in the weld metal. As described above, the control of the Nb and V components is important as a factor for improving the low temperature toughness of the titania-based flux filled wire.

Therefore, in order to improve the low temperature toughness of the titania-based flux-filled wire, it is necessary to adjust Nb and V, but further adjustment of the iron and iron contained in the flux to be used can significantly reduce the oxygen level in the weld metal. The Nb range below may be modified. Therefore, the low temperature toughness can be remarkably improved in any of the PWHT specification and the weld specification such as SR through the adjustment of the above factor, thereby providing a titania-based flux filling wire having stable low temperature toughness.

Next, the reason why the content of the element contained in the titania-based flux-filled wire manufactured as described above should be limited based on the experimental results according to the present invention will be described together with the reason that the characteristics of the raw material should be adjusted.

Titanium Oxide (TiO ₂ On the basis of): 3.0 to 9.0wt%

Titanium oxide is a main component of titania-based flux filling wire and an essential component as a slag former and an arc stabilizer. The titanium compound should be contained in the wire at 3.0 to 9.0 wt% relative to the total weight of the wire on a TiO ₂ basis. Titanium oxide has properties as a slag former having good slag coatability and peelability not observed in other slag formers. If the titanium oxide is less than 3.0 wt%, a good appearance of the beads or a good shape of the beads cannot be obtained, which leads to an increase in spatter. In particular, the bead hanging is prominent in the vertical and the upper posture, so that a good welded part is not obtained. Instead, when the titanium oxide is more than 9.0wt%, slag formation and slag viscosity are too excessive, resulting in slag incorporation, which leads to a decrease in weldability.

Examples of titanium oxide sources include natural titanium oxide and industrial titanium oxide (including synthetic rutile), rutile, reduced illumenite, leucoxene, ilmenite and potassium titanate. However, the content of Nb and V inevitably contained in the wire, as described below, should preferably be controlled by such a source of titanium oxide containing less impurities.

Mg (magnesium): 0.1 to 0.8 wt%

Mg has the effect of reducing the oxygen content in the weld metal and the low temperature toughness of the weld metal can be remarkably improved when the oxygen content in the weld metal is suppressed to about 600 ppm by weight or less. Therefore, as the Mg content increases, the Charpy impact value of the weld metal increases, so that the wavefront transition temperature of the weld metal decreases and the impact value at low temperatures can be increased. On the contrary, increasing the Mg content increases the high melting point MgO in the slag, accompanied by a decrease in fluidity, which also involves a decrease in slag coverage with an increase in spatter and fum. Therefore, the Mg content should be 0.1 to 0.8 wt% based on the total weight of the wire. In addition to the metal Mg, Mg may also be added in the form of Mg alloys such as Al-Mg, Si-Mg, Si-Ca-Mg, Ca-Mg and Ni-Mg. Such Mg alloys, if used, can cause relatively slower reactions than metal Mg, reducing spatter generation.

B (boron): 0.001 to 0.03 wt%

B has the effect of improving notch toughness. If the B content is less than 0.001 wt%, the effect is reduced. Instead, when the B content is more than 0.03 wt%, the toughness improvement effect is rapidly decreased, and the expansion force is too high due to hardening, so that breakage of the weld metal occurs rapidly. Therefore, B content is 0.001 to 0.03 wt% with respect to the total weight of the wire. In addition, B is added in the form of a B alloy such as Fe-B, but B may be added in the form of a boron oxide. This is because boron oxide is reduced to boron during the welding process.

Mn (manganese): 1.0 to 3.0 wt%

Mn has the effect of improving the appearance and shape of the beads and the effect of improving the weldability. In addition, Mn promotes deoxidation of the weld metal, and part of the Mn is trapped in the weld metal to improve hardenability and to refine the unaffected crystalline tissue parts to improve toughness and strength. These effects deteriorate when Mn content is less than 1.0 wt%. Instead, when the Mn content exceeds 3.0 wt%, the Mn yield in the weld metal is increased to improve the strength more than necessary, thereby easily causing breakage of the weld metal. The Mn content is therefore 1.0 to 3.0 wt% with respect to the total weight of the wire. In addition, Mn can be added in the form of Mn alloys such as Fe-Mn and Si-Mn in addition to electrolytic Mn.

Si (silicon): 0.1 to 1.2 wt%

Si, like Mn, has the effect of improving the appearance and formation of beads and maintaining good weldability. In addition, Si promotes deoxidation of the weld metal, and part of Si is effectively trapped in the weld metal, thereby improving the strength of the weld metal. If the Si content is less than 0.1 wt%, these effects are reduced. Instead, when the Si content exceeds 1.2wt%, the yield of Si trapped in the weld metal is increased to make crystal grains of the weld metal in the coarse particles, thereby deteriorating the notch toughness. The Si content is therefore 0.1 to 1.2 wt% with respect to the total weight of the wire. In addition, Si can be added in the form of Si alloys such as Fe-Si and Si-Mn.

Nb (niobium): 0.0120 wt% or less

V (vanadium): 0.0200 wt% or less

Nb and V contained in the wire are mainly present in the form of titanium oxide (natural and industrial titanium oxide (including synthetic rutile), rutile, reduced ilmenite, leucoxene, ilmenite, potassium titanium, etc.) as a raw material of TiO ₂ . Trace amounts of Nb or V may affect the crystal composition and mechanical properties of the weld metal. More specifically, when the Nb and V contained in the wire exceeds 0.0120 wt% and 0.0200 wt%, respectively, carbides and nitrides are remarkably formed in the reheated portion of the weld metal, thereby degrading the hardenability and toughness. When PWHT, such as SR processing, is performed on the weld metal, carbides of Nb and V are deposited differently across all crystal structures in the reheat section of the weld metal, as in the weld reheat section, further degrading the toughness.

Preferably the range of Nb and V is 0.00050 wt% or less and 0.0150 wt% or less, respectively. More preferably, the ranges are 0.00010 wt% or less and 0.0100 wt% or less, respectively. In this range, high notch toughness can be obtained and high fracture toughness (e.g., CTOD value of 0.25 mm or more at 10 DEG C for a weld specification or PWHT specification) can be obtained.

As mentioned above, the toughness can be dramatically improved by controlling the Nb and V content. This is probably because the oxygen content in the weld metal is significantly reduced by the adjustment according to the formula [ferrous metal (wt%) / total iron (wt%)] ≧ 0.85.

Metal iron: 5 to 50 wt% (relative to the total weight of the flux)

Metal iron is particularly represented by metal iron components contained in iron powder and various iron alloys (Fe-Mn and Fe-Ti, etc.). Metal iron is added in an appropriate amount to increase the weld metal volume, adjust the bead shape and increase the arc stability. In order to achieve this effect, it is necessary to add metal iron at 5 wt% or more based on the total weight of the flux. Instead, when the ratio of metal iron exceeds 50wt%, defects such as poor bonding are easily generated, and the spatter generated is significantly increased. Therefore, the ratio of the metal iron to the present flux filling wire should be defined as 5 to 50 wt% with respect to the total weight of the flux.

In general, iron compounds mainly composed of iron oxides are contained in iron powders and various iron alloys, and iron oxides have an effect of greatly increasing the oxygen content in the weld metal. Therefore, when defined in accordance with the present invention, the ratio of ferrous (wt%) to iron (wt%) in the flux of the present flux filling wire should be defined as described in the following section.

Ratio of metal iron / iron rail: more than 0.85

According to the present invention, the ratio of iron contained in all fluxes to those contained in the form of pure metals (metal iron, iron alloys, etc.) relative to those contained in the form of iron compounds mainly composed of iron oxides is the amount of metal iron to total iron. It is limited by the limitation of the ratio. As shown in FIG. 1, when the ratio is less than 0.85, the oxygen content in the weld metal is greatly increased to deteriorate low temperature toughness. For this reason, the metal iron (wt%) / total iron (wt%) is required to be 0.85 or more. Moreover, it is more preferable that the range is 0.95 or more.

The term "iron iron" herein means the amount of iron as iron component solubilized in alkaline solvents (caustic soda and sodium peroxide) and measured by ascorbic acid reduced potassium iodide titration.

Water content in the wire: 20 to 1000 ppm by weight

In order to suppress Nb and V content in a wire, it is preferable to use industrial titanium oxide with little Nb and / or V content as a raw material of a titanium oxide. However, commercially available titanium oxides have been used as raw materials for pigments, catalysts, electronic materials and the like, and therefore have very fine particle sizes and low bulk specific gravity. Attention is not paid to its water content and its water content is so high that it cannot be used as a raw material for flux filling wire. By pretreatment, the water content in the wire must be controlled at a constant level.

According to the research work of the present inventors, the upper limit of the water content in the wire as the final product containing the surface lubricant is determined in the atmosphere (oxygen atmosphere) at a temperature of 750 ° C. by the KF method (Karl-Fisher total analysis method; JIS K0113-1979). 1000 ppm by weight when measured. If the water content exceeds this limit, the breakdown occurs easily due to the high content of dispersible hydrogen in the weld metal and the presence of gas defects. Instead, if the water content is less than 20 ppm by weight, the arc stability during welding deteriorates and severely degrades the weldability. Therefore, the water content in the flux-filled wire should be defined as 20 to 1000 ppm by weight (KF method, 750 ° C, in O ₂ atmosphere). Furthermore, the preferred range of water content is 50 to 500 ppm by weight.

The pretreatment can be satisfactory whether the titanium oxide is simply present as a raw material, the step of forming and stretching the wire and any subsequent steps, and the method is not limited at all.

P (phosphorus): 0.030wt% or less

P is an element having a great influence on low temperature toughness. Increasing its content will degrade the toughness. 4 shows a graph showing the relationship between the P content in the wire on the abscissa and the Charpy impact value on the ordinate. As shown in Fig. 4, the brittle P component is deposited at the crystal boundary during PWHT after SR processing or the like to degrade toughness. When the P content to the total weight of the wire is in the range of about 0.010 wt%, almost the same impact value is obtained regardless of the content. However, at 0.015 wt%, the impact value tends to decrease slightly, while at 0.030 wt% the impact value is severely lowered.

In addition, the P content also has the same effect on the Charpy absorbed energy on the CTOD value. Therefore, the P content should be suppressed below 0.030 wt%, preferably 0.020 wt%. This figure is also different from that shown in Japanese Patent Laid-Open No. 8-10982, but this is also one of the limiting effects of [metal iron (wt%) / total iron (wt%)] ≧ 0.85 as in the case of Nb and V.

P remaining in the weld metal from the steel shell is different from P remaining in the weld metal from the flux. More specifically, more P remains in the weld metal from the steel shell than the flux, and therefore, the P content is preferably suppressed to 0.015 wt% or lower based on the above reason.

F (fluoride): 0.01 to 0.30 wt%

F has the effect of improving the arc stability and also improving the low temperature toughness of the weld metal because of its dehydrogenation action. If the F content is less than 0.01 wt%, the effect is reduced. Instead, if the F content is higher than 0.30 wt%, the amount of spatter and puree is increased to deteriorate weldability. At the same time, the slag fluidity increases excessively, resulting in deterioration of the bead form. Therefore, the F content should be 0.01 to 0.30 wt% based on the total weight of the wire. In addition, F is added from the metal fluoride of alkali metals or alkaline earth metals such as NaF, KF, LiF, MgF ₂ and CaF ₂ contained in the flux, so the F content is based on the F content therein.

Gross weight of oxide: 9.0wt% or less

The amount of slag slag formers as TiO ₂ in addition to _{SiO 2, Al 2 O 3,} ZrO 2 and however may use a combination of oxides such as Bi ₂ O ₃ is the total weight of the oxide including TiO ₂ is generated above the 9.0wt% There are so many slag mixing easily that it leads to deterioration of weldability. At this point the iron oxide should be added in a range that satisfies the formula [metal iron (wt%) / total iron (wt%)] ≥ 0.85 in terms of the total composition of the flux.

Ni (nickel): 0.3 to 5.0 wt%

Ni has the effect of improving the hardenability of the weld metal. If the Ni content is less than 0.3 wt%, the effect is reduced. Instead, when the Ni content is higher than 5.0 wt%, the yield of Ni remaining in the weld metal increases, which leads to higher strength than that of the weld metal, which is accompanied by high frequency of occurrence of breakage. Therefore, Ni content is 0.3-5.0 wt% with respect to the gross weight of a wire. Ni may here be added from a Ni alloy in addition to the metal Ni.

Charging Flux Characteristics

Titanium oxides as raw materials, such as industrial titanium oxides, have extremely fine grain sizes and small apparent densities, so if these oxides are to be used as flux materials for flux-filled wires, these oxides may be granulated, cured, crushed, and grounded prior to wire forming. Pretreatment in the form of a filling flux is often required. In order to produce flux filling wire at a more stable flux ratio, the filling flux must have characteristics such as an apparent density of 1.0 to 4.0 and a flux particle size of up to 500 μm. It is preferable that particle size is 500 micrometers or less from the point of wire manufacture. Above this maximum particle size, wire breakage or flux may occur during wire forming and stretching, and welding cannot be performed in a stable manner. More preferably, the particle size ranges from 50 to 400 µm in terms of wire production.

The pretreatment can also be satisfactorily carried out in either the step in which the titanium oxide is simply present as a raw material and in the step of mixing the various flux materials together and the method is not limited at all.

According to the present invention, various other alloying elements and the like can be satisfactorily applied to the flux or steel shell within the limited range of the conditions as described above. For example, when Al, Ti or Zr in the form of metal or ferroalloy is added at 0.5wt% or less, the deoxidation or denitrification effect is improved to prevent the molten metal from hanging in the vertical position. Furthermore, if Cr or Cu is contained in a small amount therein, weather resistance can be improved. This effect can be provided from Ni or P defined according to the invention. As arc stabilizers additionally oxides of alkali metals such as K, Na and Li or compounds of rare earth elements such as Ce and La may be added satisfactorily.

The flux filling wire according to the present invention can be produced by filling titania-based fluxes into a soft steel shell according to a routine method using cold steels and hot steels having deep drawing properties in terms of filling operability. The flux filling ratio is not particularly limited but is preferably 10 to 30 wt% based on the total weight of the wire.

The wire has any cross-sectional shape without particular limitation, including, for example, the various shapes illustrated in FIGS. 5A, B, C, D, and the like. The wire surface in the shape of FIG. 5D may be plated with Al, Cu, or the like at a plating level of 0.05 to 0.35 wt%. The wire diameter can be appropriately determined depending on the use.

Furthermore, oxidizing, neutral or reducing shield gases are used for welding. Generally the shield gas is a CO ₂ gas or two or more mixed gases selected from Ar, CO ₂ , O ₂ and He.

Description of Preferred Embodiments

Now, Examples of the present invention will be described in comparison with Comparative Examples. First, test wires of the composition shown in Tables 1 to 6, each having a cross-sectional shape as shown in FIG. 5B, were prepared. Subsequently, welding was performed using these individual test wires under conditions provided in the Charpy impact test and COD test column, and then tested for toughness and weldability after SR (620 ° C × 10 hours) in the form of weld specifications and PWHT specifications. . The test results are shown in Tables 7 to 10 below.

The Charpy impact test and COD test of the flux-filled wires of the inventive examples and comparative examples as shown in Tables 1 to 6 were carried out in combination with its weldability test. The results are shown in Tables 7 to 10 below. The Charpy impact test was carried out under the same conditions as the welding conditions described above. Welding conditions for the COD test are described below.

Welding condition (about COD test)

Test wire

Wire diameter: 1.2mm

Cross-sectional shape: FIG. 5A

Flux ratio: 15wt%

Polarity: DCEP (DC Reverse Polarity)

Welding current: 180 ~ 250A

Welding voltage: suitable amount

Test steel plate: BS4360, Gr50D, plate thickness 40 mm, x-bevel angle 50 °

Welding position: vertical, top view

Sealed gas: 80% Ar-20% CO ₂ mixed gas, flow rate 25 liters / minute

COD testing was performed according to BS7448-1991.

Also in Tables 8 and 10, weldability is classified into five stages, namely 1 (poor) to 5 (excellent).

As can be seen from Tables 1 and 10, in the examples in which the chemical composition in the wire is within the range according to the present invention, the weldability including the appearance of the beads and the Charpy impact test and the COD test were good.

Instead, since the titanium oxide content in Comparative Example No. 14 was less than the lower limit of the present invention, the appearance and form of the beads were poor. In the comparative example No. 15 in which the content of the titanium oxide was above the upper limit of the present invention, slag mixing occurred. In Comparative Example No. 16, since the Mg content was less than the lower limit of the present invention, the oxygen content in the weld metal was increased, and the Charpy absorbed energy and CTOD value were clearly reduced. In Comparative Example No. 17, the Mg content was higher than the upper limit of the present invention, so that the volume of the spatter and the pue increased, causing deterioration of workability. Furthermore, in Comparative Example No. 18, since the B content was less than the lower limit of the present invention, the Charpy absorbed energy and CTOD value were significantly reduced, and the volume of the spatter and the pue increased because the F content was above the upper limit of the present invention. In Comparative Example No. 19, since the B content was above the upper limit of the present invention, cracks occurred in the weld metal.

Furthermore, in Comparative Example No. 20, since the Mn content was less than the lower limit of the present invention, the Charpy absorbed energy and CTOD value were clearly reduced, and the appearance and shape of the beads were poor. In Comparative Example No. 21, since the Mn content was above the upper limit of the present invention, the strength improved more than the required level, causing cracks in the weld metal. In Comparative Example No. 22, the appearance and form of the beads deteriorated because the Si content was less than the lower limit of the present invention. In Comparative Example No. 23, since the Si content was above the upper limit of the scope of the present invention, the crystal grains expanded to the crude particles, causing cracking in the weld metal.

Further, in Comparative Examples No. 24 and 25, since the Nb or V content was above the upper limit of the present invention, weldability and the like were good, but the Charpy absorbed energy and CTOD values were remarkably reduced. In Comparative Examples Nos. 26 to 28, the Charpy absorbed energy and CTOD values were reduced because the metal iron (wt%) / total iron (wt%) was below the lower limit of the present invention.

As fully described in Tables 1 to 10, the present invention has good toughness after the two specifications of the weld specification and the PWHT specification, in particular the low temperature toughness at -60 ° C to -80 ° C required to build LPG and LNG ships and offshore structures. Provided is a flux-filled wire for arc welding that has excellent processability in an electronic world.

Claims (17)

It is prepared by filling the steel shell with flux, 3.0 to 9.0 wt% titanium oxide (based on TiO ₂ ), 0.1 to 0.8 wt% Mg, 0.001 to 0.03 wt% B, 1.0 to 3.0 wt% and Si 0.1 to 1.2 wt%, Nb and V contained in the wire are adjusted to Nb 0.0120wt% or less, V 0.0200wt% or less relative to the total weight of the wire, and the metal iron contained in the flux is added to the total weight of the flux. A flux-filled wire for arc welding, characterized in that it is 5 to 50 wt% and the ratio of metal iron to total iron satisfies the formula [metal iron (wt%) / total iron (wt%)] ≥ 0.85. The flux filling wire for arc welding according to claim 1, wherein the total water content is adjusted in the range of 20 to 1000 ppm by weight (KF method at 750 ° C in O ₂ atmosphere). The flux filling wire for arc welding according to claim 1 or 2, wherein P in the impurity is 0.030 wt% or less with respect to the total weight of the wire. Flux-filled wire for arc welding, characterized in that the wire contains metal fluoride 0.01 to 0.30 wt% based on the fluoride and 9.0 wt% or less of an oxide containing TiO ₂ based on the total weight of the wire. The flux-filled wire for arc welding according to claim 3, wherein the wire contains metal fluoride in an amount of 0.01 to 0.30% by weight based on fluoride and 9.0% by weight or less of an oxide including TiO ₂ . The flux-filled wire for arc welding according to claim 1 or 2, wherein the wire contains 0.3 to 5.0 wt% of Ni with respect to the total weight of the wire. The flux-filled wire for arc welding according to claim 3, wherein the wire contains 0.3 to 5.0 wt% of Ni, based on the total weight of the wire. The flux-filled wire for arc welding according to claim 4, wherein the wire contains 0.3 to 5.0 wt% of Ni, based on the total weight of the wire. The flux-filled wire for arc welding according to claim 5, wherein the wire contains 0.3 to 5.0 wt% of Ni, based on the total weight of the wire. The flux filling wire for arc welding according to claim 1 or 2, wherein the filled flux has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 mu m or less. 4. The flux filling wire for arc welding according to claim 3, wherein the filled flux has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 mu m or less. The flux filling wire for arc welding according to claim 4, wherein the filled flux has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 mu m or less. The flux filling wire for arc welding according to claim 5, wherein the filled flux has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 mu m or less. 7. The flux filling wire for arc welding according to claim 6, wherein the filled flux has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 mu m or less. 8. The flux filling wire for arc welding according to claim 7, wherein the filled flux has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 mu m or less. 9. The flux filling wire for arc welding according to claim 8, wherein the filled flux has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 mu m or less. 10. The flux filling wire for arc welding according to claim 9, wherein the filled flux has an apparent density of 1.0 to 4.0 and a maximum particle size of 500 mu m or less.